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, , . 't , 1

NASA CR· 152257 LSI ER·336·4

TECHNOLOGY ADVANCEMENT OF AN OXYGEN GENERATHlN SUBSYSTEM

'09-2BBB3 (NhSl-CR-152257) TECHNOLOGY ADV1NCE~ENT OF AN OXYGEN GENERATION SUBSYSTE ft Final Report (L~fe systems. Inc •• Cleveland. Ohio.) 78 p HC A05/~F 101 CSCL 06K

G3/5Li Unclas 31Li2B

FINAL REPORT

by

M. K. lee, K. A. Burke, F. H. Schubert and R. A. Wynveen

May, 1979

Prepared Under Contract NAS2-9795

by

,Cife SlIs/ellls, 'NC. Cleveland, OH 44122

for

AMES RESEARCH CENTER National Aerona\!tics and Space Administration

AUG197t

RECEIVED NA3A sn FACIUl'f ACCns DEPl. '

, _\ . /

NASA CR-152257 LSI ER-336-4

TECHNOLOGY ADVANCEMENT OF AN OXYGEN GENERATHlN SUBSYSTEM

'09-28883 (NhSA-CR-1S22S7) TECHNOLOGY lDVANCE~ENT OF AN OXYGEN GENERATION SUBSYSTEft Pinal Report (L~fe systems. Inc •• Cleveland. Ohio.) 78 p HC AOS/~F AOl CSCL 06K

G3/S11 Unclas )11128

FINAL REPORT by

M_ K. Lee, K_ A. Burke, F _ H. Schubert and R. A_ Wynveen

May, 1979

Prepared Under Contract NAS2-9795

by

.ci/e S!ls/eIllS, IHC. Cleveland, OH 44122

for

AMES RESEARCH CENTER National Aeronal!tics and Space Administration

AUG197t

RrCEIVED NAU sn FACIut'f ACCm DEP1. .

,

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ER-336-4

TECHNOLOGY ADVANCEMENT OF AN OXYGEN GENERATION SUBSYSTEM

FINAL REPORT

by

Lee, M. K., Burke, K. A., Schube,rt, F. H. and Wynveen, R. A.

May, 1979

"."";..'

Distribution of this report is p,rovided in the interest of informa·tion exC:hange. Responsibility for the contents resides in the autho,rs o,r o,rganization that prepared it.

Prepared Under Contract NAS2-9795

by

LIFE SYSTEMS, INC. Cleveland, OH 44122

for

AMES RESEARCH CENTER NATl'ONAL AERONAUTICS AND SPACE ADMINISTRATION

,

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ER-336-4

TECHNOLOGY ADVANCEMENT OF AN OXYGEN GENERATION SUBSYSTEM

FINAL REPORT

by

Lee, M. K., Burke, K. A., Schube,rt, F. H. and Wynveen, R. A.

May, 1979

"."";..'

Distribution of this report is p,rovided in the interest of informa·tion exC:hange. Responsibility for the contents resides in the autho,rs o,r o,rganization that prepared it.

Prepared Under Contract NAS2-9795

by

LIFE SYSTEMS, INC. Cleveland, OH 44122

for

AMES RESEARCH CENTER NATl'ONAL AERONAUTICS AND SPACE ADMINISTRATION

FOREWORD

This repGrt was prepared by Life Systems, Inc. fGr the National AerGnautics and Space Administration (NASA) Ames Research Center in accordance with the require­ments Gf CGntract NAS2-9795, "BevelGpment Gf a Static Fee<l Wa,ter ElectrGlysis Oxygen Generation Subsystem BreadbGard." The period Gf perfGrmance for the prGgram was December 1, 1977 tG May 30, 1979. The Gbjective Gf the program was tG advance the Oxygen Genera,tion Subsystem technGlogy, based Gn static feed water electrGlysis, and tG demGnstrate the maturity Gf the hardware development f"r future multicrew space missiGns.

Mr. Franz H. Schubert was Program Manager. Dr. Myon K. Lee was Project Manager. The personnel contributing tG the program and their areas of re,sponsibili ty are indicated below.

Personp.el Area(s) of Responsibility

Ken A. Burke Lab BreadbGard Testir,g and mGdule assembly

Bob W. Ellacott Single Cell Testing

Tim M. Hallick Integrated ARX-I testing

Dennis B. Heppner I Ph.B. Subsystem integratiGn into ARX-I and ARX-I testing

Don W. Johnson Electronics fabd"ation

Ron H. Kohler BGcumentation and c(mtract administration

Eugene P. KGs?enski ElectrGde and matrix fabriC'atiGn

Myon K. Lee, Ph.B. Process calcula,tiGns and a,oalyses. COGrdi­na'tiGn Gf testing activities and aata reduction.

J. Elavid PGwell Control/Monito'r InstrumentatiG'1 design

Franz H. Cichubert Mechanical aesign, p,rGauct assurance, system analyses ana p,rGgram management

Baniel C. Walte'r Meehanieal subsystem ana compGnent aesigns

Rick A. Wynveen, Ph.B. Systems I!lesign

The CGntraet' s TeChnical MGnitGr was P. I!l. QuattrGne I Chief I Advanced Life Suppo,rt Office I NASA Ames Research Center I MGffett Field, CA.

.'

•

FOREWORD

This repGrt was prepared by Life Systems, Inc. fGr the National AerGnautics and Space Administration (NASA) Ames Research Center in accordance with the require­ments Gf CGntract NAS2-9795, "BevelGpment Gf a Static Fee<l Wa,ter ElectrGlysis Oxygen Generation Subsystem BreadbGard." The period Gf perfGrmance for the prGgram was December 1, 1977 tG May 30, 1979. The Gbjective Gf the program was tG advance the Oxygen Genera,tion Subsystem technGlogy, based Gn static feed water electrGlysis, and tG demGnstrate the maturity Gf the hardware development f"r future multicrew space missiGns.

Mr. Franz H. Schubert was Program Manager. Dr. Myon K. Lee was Project Manager. The personnel contributing tG the program and their areas of re,sponsibili ty are indicated below.

Personp.el Area(s) of Responsibility

Ken A. Burke Lab BreadbGard Testir,g and mGdule assembly

Bob W. Ellacott Single Cell Testing

Tim M. Hallick Integrated ARX-I testing

Dennis B. Heppner I Ph.B. Subsystem integratiGn into ARX-I and ARX-I testing

Don W. Johnson Electronics fabd"ation

Ron H. Kohler BGcumentation and c(mtract administration

Eugene P. KGs?enski ElectrGde and matrix fabriC'atiGn

Myon K. Lee, Ph.B. Process calcula,tiGns and a,oalyses. COGrdi­na'tiGn Gf testing activities and aata reduction.

J. Elavid PGwell Control/Monito'r InstrumentatiG'1 design

Franz H. Cichubert Mechanical aesign, p,rGauct assurance, system analyses ana p,rGgram management

Baniel C. Walte'r Meehanieal subsystem ana compGnent aesigns

Rick A. Wynveen, Ph.B. Systems I!lesign

The CGntraet' s TeChnical MGnitGr was P. I!l. QuattrGne I Chief I Advanced Life Suppo,rt Office I NASA Ames Research Center I MGffett Field, CA.

.'

•

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TABLE OF CONTENTS

LIST (IF FIGURES

LIST OF TABLES

LIST OF ACRONYMS

SUMMARY .....

PROGRAM ACCOMPLISHMENTS

INTRODUCTlON

Background Program Objectives Program Organization

AIR REVITALIZATION SYSTEM DEVELOPMENT

Concept Ilescription Hardware Ilescription

SUBSYSTEM IlEVELOPMENTS

Oxygen Generation Subsystem

Static Feed Water Electrolysis Oxygen Genera'tion Subsystem Descriptions

Water Handling Subsystem . .

Schematic and Opera,tion Hardware Ilescription

Control and Monitor Instrumentation

Power Sharing Concept . . . . . Operating Modes and Mode Transitions System Control and Monitoring Operator/System Interface Software

TEST SUPPORT ACCESSORIES

One-Person Air Revitalizatioll System Labo'ra,tocry Breadboard Module Test Sta,tld

PROilUCT ASSURANCE PROGRAM . . . .

i

£ifc SIIS/CHlS, Inc.

l:'AGE

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iv

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3

3

4 4 4

6

6 8

8

8

13 17

24

24 28

28

28 28 33 33 38

38

38 41

41

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t I

TABLE OF CONTENTS

LIST (IF FIGURES

LIST OF TABLES

LIST OF ACRONYMS

SUMMARY .....

PROGRAM ACCOMPLISHMENTS

INTRODUCTlON

Background Program Objectives Program Organization

AIR REVITALIZATION SYSTEM DEVELOPMENT

Concept Ilescription Hardware Ilescription

SUBSYSTEM IlEVELOPMENTS

Oxygen Generation Subsystem

Static Feed Water Electrolysis Oxygen Genera'tion Subsystem Descriptions

Water Handling Subsystem . .

Schematic and Opera,tion Hardware Ilescription

Control and Monitor Instrumentation

Power Sharing Concept . . . . . Operating Modes and Mode Transitions System Control and Monitoring Operator/System Interface Software

TEST SUPPORT ACCESSORIES

One-Person Air Revitalizatioll System Labo'ra,tocry Breadboard Module Test Sta,tld

PROilUCT ASSURANCE PROGRAM . . . .

i

£ifc SIIS/CHlS, Inc.

l:'AGE

iii

iv

iv

1

3

3

4 4 4

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6 8

8

8

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24

24 28

28

28 28 33 33 38

38

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Table of Contents - continued

Quality Assurance Reliability Sa£ety . . . . . . Materials Control Configuration Control

PROGRAM TESTING . . .

Integrated ARX-1 Testing

Testing Summary . OGS Perfo·rmance .

SFWEM Endurance Tes ts

Super Electrode Testing Advanced Electrode Testing

SNPPORTING TECHNOLOGY STUDIES . •

Single Cell Endurance Tests Three-Fluid Pressure Contraller Tests Product Gas Dehumidification Analysis

Concept Descriptions Selected. App'roach . .

Elimination of Stray Electrolysis in the Coolant Loop

CONCLNSIONS . .

RECOMMENrJATIONS

REFERENCES

APPENlHX 1 ARX-I FLOW SCHEMATIC

APPENIHX 2 ARX-I OPERATING MODES DEFINITIONS

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Table of Contents - continued

Quality Assurance Reliability Sa£ety . . . . . . Materials Control Configuration Control

PROGRAM TESTING . . .

Integrated ARX-1 Testing

Testing Summary . OGS Perfo·rmance .

SFWEM Endurance Tes ts

Super Electrode Testing Advanced Electrode Testing

SNPPORTING TECHNOLOGY STUDIES . •

Single Cell Endurance Tests Three-Fluid Pressure Contraller Tests Product Gas Dehumidification Analysis

Concept Descriptions Selected. App'roach . .

Elimination of Stray Electrolysis in the Coolant Loop

CONCLNSIONS . .

RECOMMENrJATIONS

REFERENCES

APPENlHX 1 ARX-I FLOW SCHEMATIC

APPENIHX 2 ARX-I OPERATING MODES DEFINITIONS

ii

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41 41 43 43 43

43

43

43 45

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61 62

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FIGURE

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17

18 19

20 21 22 23 24 25 26 27 28 29 30

31

LIST OF FIGURES

~Jajor Electrode/Catalyst Performance Improvements Air Revitalization System Block Diagram ARX-1 Hechanical Hardware . . . . . . . . ARX-1 Test Facility .......... . ARX-1 Control and Honitor Instrumentation Static Feed Water Electrolysis Concept Functional. Schematic of an SFlVE Cell OGS Flow Schematic . . . . . . . . . Single-Cell Parts . . . . . ..... Static Feed Water Electrolysis Module Three-Fluid Pressure Controller . . Water Handling Subsystem Schematic Deiodinator/Deionizer . . . . . Water Supply Tank . . . . . . ... Power Controller Block Diagram Operating Nodes and Allowable Mode Transitions One-Person Air Revitalization System Opera,tor/System Interface Panel . . . . . . . . . . . . . . . . Air Revitalization System TSA Block Diagram .. One-Person Air Revitalization System Parametric Data Display Cabinet . . . . Laboratory Breadboard ~lodule Test Stand ARX-1 Test Overview . . . . . . . ARX-l System Performance . . .. Life Testing of ARX-l Componen,ts/Subsystems ARX-l SFWE~I Performance . . . . . . . . . . SFWEM Performance Versus Current Density Performance of the SFWEM with Super Electrodes Perf(lrmance of the SFWEM with Advanced Electrodes Single Cell PerfoEmance fJuring Endurance Test . . SupeE Electrode Performance Versus CUErent Density Th,ree-Fluid Pressure Controller - Solid State Transducer Characteristics Product Gas De\~ Point . . . . .

iii

Cite SlIs/ellls. Inc.

PAGE

6 7

10 11 12 14 15 19 22 23 25 26 29 30 31 32

37 39

40 42 44 46 47 48 52 53 55 56 57

59 63

FIGURE

t 1

J 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17

18 19

20 21 22 23 24 25 26 27 28 29 30

31

LIST OF FIGURES

~Jajor Electrode/Catalyst Performance Improvements Air Revitalization System Block Diagram ARX-1 Hechanical Hardware . . . . . . . . ARX-1 Test Facility .......... . ARX-1 Control and Honitor Instrumentation Static Feed Water Electrolysis Concept Functional. Schematic of an SFlVE Cell OGS Flow Schematic . . . . . . . . . Single-Cell Parts . . . . . ..... Static Feed Water Electrolysis Module Three-Fluid Pressure Controller . . Water Handling Subsystem Schematic Deiodinator/Deionizer . . . . . Water Supply Tank . . . . . . ... Power Controller Block Diagram Operating Nodes and Allowable Mode Transitions One-Person Air Revitalization System Opera,tor/System Interface Panel . . . . . . . . . . . . . . . . Air Revitalization System TSA Block Diagram .. One-Person Air Revitalization System Parametric Data Display Cabinet . . . . Laboratory Breadboard ~lodule Test Stand ARX-1 Test Overview . . . . . . . ARX-l System Performance . . .. Life Testing of ARX-l Componen,ts/Subsystems ARX-l SFWE~I Performance . . . . . . . . . . SFWEM Performance Versus Current Density Performance of the SFWEM with Super Electrodes Perf(lrmance of the SFWEM with Advanced Electrodes Single Cell PerfoEmance fJuring Endurance Test . . SupeE Electrode Performance Versus CUErent Density Th,ree-Fluid Pressure Controller - Solid State Transducer Characteristics Product Gas De\~ Point . . . . .

iii

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PAGE

6 7

10 11 12 14 15 19 22 23 25 26 29 30 31 32

37 39

40 42 44 46 47 48 52 53 55 56 57

59 63

I-~--~---

Ci/e SlIs/eIllS. J6t.

TABLE ..=..:.....=;.,

1

2 3 4 5 6 7 8 9

10 11

12

13

14

LIST OF TABLES

One-Person Air Revitalization System Design Requirements . . . • . . . . OGS Design Specifications . . OGS Mechanical Component List OGS Nominal Operating Conditions Water Handling Subsystem Characteristics OGS and WHS Controls Definition • . . . . Sensor List ........ ' ...... . Parameters Monitored for Automatic Shutdown OGS Baseline OperaUng Conditions . . . ARX-l Shutdown Summary ....... . Three-Fluid Pressure Controller Nominal Operating Conditions . . . . . . . . . . . . . . . Comparison of ED and Line Heating Approach for Dehumidification . . . . • . . . . . . . . Operating Conditions and Characteristics of a Three­Person Capacity OGS . . . . Summary of Energy Balances . . . . . . . .

ARS ARX-l

ASl!! CHeS C/M I CRT I!lM EC/LSS EI!l EI!lC EDCM NGM NSS OGS ORS S-CRS SFWE SF\VEM 3-FPC tSA WHS

LIST OF ACRONYMS

Air Revitalization Sys'tem Air Revitalization System (one-person, experimental) Air Supply Unit Cabin Humidity Control Subsystem Contro l/Moni to'r Instrumentation Cathode-Ray Tube Dehumidifier Module Environmen,tal Control/Life Support System Electrolytic Dehumidification Electrochemical Depolarized CO

2 Concentrato'r

EDC Module Nitrogen Generation Module Nitrogen Supply Subsys'tem Oxygen Generation Subsystem Oxygen Recovery System Saba tier CO

2 Reduction Subsystem

S,tatic Feed Water Elect,rolysis Static Feed Water Electrolysis Module Three-Fluid Pressure Controller Test Support Accessories Water Handling Subsystem

iv

9 18 20 21 27 34 35 36 49 50

60

64

65 66

.'

I-~--~­

Ci/e SlIs/eIllS. J6t.

TABLE ..=..:.....=;.,

1

2 3 4 5 6 7 8 9

10 11

12

13

14

LIST OF TABLES

One-Person Air Revitalization System Design Requirements . . . • . . . . OGS Design Specifications . . OGS Mechanical Component List OGS Nominal Operating Conditions Water Handling Subsystem Characteristics OGS and WHS Controls Definition • . . . . Sensor List ........ ' ...... . Parameters Monitored for Automatic Shutdown OGS Baseline OperaUng Conditions . . . ARX-l Shutdown Summary ....... . Three-Fluid Pressure Controller Nominal Operating Conditions . . . . . . . . . . . . . . . Comparison of ED and Line Heating Approach for Dehumidification . . . . • . . . . . . . . Operating Conditions and Characteristics of a Three­Person Capacity OGS . . . . Summary of Energy Balances . . . . . . . .

ARS ARX-l

ASl!! CHeS C/M I CRT I!lM EC/LSS EI!l EI!lC EDCM NGM NSS OGS ORS S-CRS SFWE SF\VEM 3-FPC tSA WHS

LIST OF ACRONYMS

Air Revitalization Sys'tem Air Revitalization System (one-person, experimental) Air Supply Unit Cabin Humidity Control Subsystem Contro l/Moni to'r Instrumentation Cathode-Ray Tube Dehumidifier Module Environmen,tal Control/Life Support System Electrolytic Dehumidification Electrochemical Depolarized CO

2 Concentrato'r

EDC Module Nitrogen Generation Module Nitrogen Supply Subsys'tem Oxygen Generation Subsystem Oxygen Recovery System Saba tier CO

2 Reduction Subsystem

S,tatic Feed Water Elect,rolysis Static Feed Water Electrolysis Module Three-Fluid Pressure Controller Test Support Accessories Water Handling Subsystem

iv

9 18 20 21 27 34 35 36 49 50

60

64

65 66

.'

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Ci/e Gl/s/eIllS, IHC.

SUMMARY

Regenerative processes for the revitaliza,tion of spacecraft atmospheres are essential for making long-term manned space missions possible. One of the mast important steps in this revitaliza,tion pracess is the reclamation af breathable oxygen fram metabolically-praduced carbon dioxide. Oxygen can be recovered in the farm of water thraugh the chemical reduction af carban dioxide. The water is then electralyzed ta produce oxygen. Under this program an Oxygen GeneraticlO Subsystem based on water electralysis was develaped and tested ta further advance the concept and technolagy of the spacecraft Air Revitalizatian System. Emphasis was placed on demanstra,ting the subsystem integration concept and hardware maturity at a subsystem level.

The Air Revitaliza,tian System cansists af six subsystems and the centralized Cantrol/Monitor Instrumentation. These subsystems are (1) an Oxygen Genera­tian Subsystem, (Z) a Carbon Dioxide Cancentrator, (3) a Carbon Bioxide Reduc­tian Subsystem, (4) a Water Handling Subsystem, (5) a Cabin Humidity Cantral Subsystem and (6) a Nitrogen Supply Subsystem. The Oxygen Generatian Subsystem, part of the Water Handling Subsystem and centraliZed Contral/Manitar Instrumen­tat ian were designed, fabricated and tested as part of the Air Revitalization System under this p'ragram. Developments of other subsystems af the Air Revita~ lizatian System were funded under separate NASA Ames Research Centa pragrams and under the Cantracta,r's internal research and develapment pragrams. This repart autlines the develapment activities a.ssaciated with the Oxygen Genera­tion Subsystem, the Water Handling Subsystem and the centralized Cantral/Manitar Instrumentation. Emphasis is placed on the develapments af the Oxygen Genera­tian Subsystem and its technalagy.

The primary abjective af the Oxygen Generatian Subsystem is ta p,raduce axygen for metabalic cansumption. The byproduct hydragen is used in pracesses for concentrating and reducing carban diaxide. The Oxygen Generation Subsystem develaped under the present program employs the Sta,tic Feed Water Electralysis cancept. The static feed-based Oxygen Gene'ration Subsystem cansists basically af three main parts: an elettrachemical module, a pressure con,traller and a water feed tank. The generatian afaxygen and hydragen accu'rs in a series af electralysis cells fo,rming an electrachemiical madule. The cells use an aqueous salutian of potassium hyd·roxide retained in a porous asbestos ma,trix. Water feed into the individual cells is a.chieved statically, minimizing maving parts for increased subsystem reliability.

The Oxygen Generation Subsystem develaped as part af this p,ragrdm was designed ta deliver oxygen at a rate of 1.46 kg/d (3.ZZ lb/d) which included 0.83 kg/d 0.84 lb/d) far metabalic consumptian of ane person aOGl 0.63 kg/d (1.3'8 lb/d) far other requirements such as cabin leaikagema,keup. ZThe 1Z-cell electrochemi­cal madule apera,ted at a current density of 197 mAl cm (183 ASF), temperature af 339 K (150 F) and p,ressnre of

Z1,068 kP2 055 psia). The active elect.rade

area of a single cell is 9Z.9 cm (0.1 ft). The electralysis cells were inte,tcannected i!l se,ries electrically. All fluid cannectians were made in parallel. The pressure cantraller combined, in a single assembly, the sensars and actua·tors necessary to cantral and monitor fluid p'res.sure levels and differentials during all aperating mades and transitians, including steady­state aperatian, startup and shutdown.

1

t j

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Ci/e Gl/s/eIllS, IHC.

SUMMARY

Regenerative processes for the revitaliza,tion of spacecraft atmospheres are essential for making long-term manned space missions possible. One of the mast important steps in this revitaliza,tion pracess is the reclamation af breathable oxygen fram metabolically-praduced carbon dioxide. Oxygen can be recovered in the farm of water thraugh the chemical reduction af carban dioxide. The water is then electralyzed ta produce oxygen. Under this program an Oxygen GeneraticlO Subsystem based on water electralysis was develaped and tested ta further advance the concept and technolagy of the spacecraft Air Revitalizatian System. Emphasis was placed on demanstra,ting the subsystem integration concept and hardware maturity at a subsystem level.

The Air Revitaliza,tian System cansists af six subsystems and the centralized Cantrol/Monitor Instrumentation. These subsystems are (1) an Oxygen Genera­tian Subsystem, (Z) a Carbon Dioxide Cancentrator, (3) a Carbon Bioxide Reduc­tian Subsystem, (4) a Water Handling Subsystem, (5) a Cabin Humidity Cantral Subsystem and (6) a Nitrogen Supply Subsystem. The Oxygen Generatian Subsystem, part of the Water Handling Subsystem and centraliZed Contral/Manitar Instrumen­tat ian were designed, fabricated and tested as part of the Air Revitalization System under this p'ragram. Developments of other subsystems af the Air Revita~ lizatian System were funded under separate NASA Ames Research Centa pragrams and under the Cantracta,r's internal research and develapment pragrams. This repart autlines the develapment activities a,ssaciated with the Oxygen Genera­tion Subsystem, the Water Handling Subsystem and the centralized Cantral/Manitar Instrumentation. Emphasis is placed on the develapments af the Oxygen Genera­tian Subsystem and its technalagy.

The primary abjective af the Oxygen Generatian Subsystem is ta p,raduce axygen for metabalic cansumption. The byproduct hydragen is used in pracesses for concentrating and reducing carban diaxide. The Oxygen Generation Subsystem develaped under the present program employs the Sta,tic Feed Water Electralysis cancept. The static feed-based Oxygen Gene'ration Subsystem cansists basically af three main parts: an elettrachemical module, a pressure con,traller and a water feed tank. The generatian afaxygen and hydragen accu'rs in a series af electralysis cells fo,rming an electrachemiical madule. The cells use an aqueous salutian of potassium hyd'roldde retained in a porous asbestos ma,trix. Water feed into the individual cells is achieved statically, minimizing maving parts for increased subsystem reliability.

The Oxygen Generation Subsystem develaped as part af this p,ragrdm was designed ta deliver oxygen at a rate of 1.46 kg/d (3.ZZ lb/d) which included 0.83 kg/d 0.84 lb/d) far metabalic consumptian of ane person aOGl 0.63 kg/d (1.3,g lb/d) far other requirements such as cabin leaikagema.keup. ZThe lZ-cell electrochemi­cal madule apera,ted at a current density of 197 mAl cm (183 ASF), temperature af 339 K (150 F) and p,ressnre of

Z1,068 kP2 055 psia). The active elect.rade

area of a single cell is 9Z.9 cm (0.1 ft). The electralysis cells were inte,tcannected i!l se,ries electrically. All fluid cannectians were made in parallel. The pressure cantraller combined, in a single assembly, the sensars and actua'tors necessary to cantral and monitor fluid p,res,sure levels and differentials during all aperating mades and transitians, including steady­state aperatian, startup and shutdown.

1

Ci/t SII.S/(HlS, !HC.

the primary function of the Water Handling Subsystem is to ensure that a supply of water exists for the Oxygen Generation Subsystem. The principal components in the Water Handling Subsystem are a water storage tank and a deionizer. The deionizer contains both a charcoal and an ion-exchange resin bed for removing iodine ions and dissolved carbon dioxide from the feed water of the Oxygen Generation Subsystem. Water comes either from the Carbon Dioxide Reduction and Cabin Humidity Control Subsystems or from an external source.

The centralized Control/Monitor Instrumentation employs an advan.ced instrumenta­tion concept which is highlighted by minicomputer-based control and monitoring. The function of the Control/Monitor Instrumenta,tion is to provide automatic mode and mode transition "ontrol, automatic shutdown provisions fo,r self-pro­teetion, provisions for monitoring system parameters and provisions for inter-facing with ground test instrumentation. .

An extensive test program including components, subsystem and integrated system testing was completed. The overall objectives of the test program were to (1) prove the integration concept of the Air Revitalization System, (2) further advance the Oxygen Generation Subsystem technology, and (3) demons tra,te the hardware maturity of the Oxygen Generation Subsystem components such as electrolysis cells, modules and the Three-Fluid PresSure Controller. Inte­grated t.esting of the experimental Air Revitalization System was conducted for a period of 120 days and included testing at the component, subSystem and total system le~'els.

A total of 480 hours of suceessful integrated operation was aehieved with the Air Revitalization System. Of the total normal operation, two seven-day periods of uninterrupted operation were achieved. A single cell with one of the super electrodes (WAB-6) was subjected to endurance testing. A total of 8,650 hours continuous operation has been accumulated at the "one Ius ion of the current program. Cell voltages du'ring the period of endurance testing remained stable in the range of 1. 462 to 1. 50 V. Opera't~ng eondi tions were set nominally at 352 K (175 F), 161 rnA/em' (I50 ASF) and amhent pressure. A 12-cell module /Ising the super electrodzs (WAB-6) was tested a,t 355 K (180 F), 993 kPa (144 psia) and 161 rnA/em (I50 ASF). Individual eell voltages varied in the range of 1. 47 to 1.50 V, indica'ting the perfo,rmanee of the super electrodes is reprodUcible. In addition, the pressu're controller and another 12-cell module using the advan~ed electrodes (WAB-5) were extensively tested to determine the hardwa re ma'tllri ty .

It is concluded from the results reported herein that the integration concept of the Air Revitalization System is feasible. Hardware and technology of the Oxygen Generation Subsystem has been demonstrated to be close to the preproto­type level. Continueg development of the oxygen generation teehnology is recommended to further reduce the total weight penalties of the Oxygen Genera­tion Subsystem through optimiZation. Successfui completion of this development will p,roduce timely technology necessary to plan future advanced emrironmental control and life suppo,rt system programs and experiments.

2

Ci/t SII.S/(HlS, !HC.

the primary function of the Water Handling Subsystem is to ensure that a supply of water exists for the Oxygen Generation Subsystem. The principal components in the Water Handling Subsystem are a water storage tank and a deionizer. The deionizer contains both a charcoal and an ion-exchange resin bed for removing iodine ions and dissolved carbon dioxide from the feed water of the Oxygen Generation Subsystem. Water comes either from the Carbon Dioxide Reduction and Cabin Humidity Control Subsystems or from an external source.

The centralized Control/Monitor Instrumentation employs an advan.ced instrumenta­tion concept which is highlighted by minicomputer-based control and monitoring. The function of the Control/Monitor Instrumenta,tion is to provide automatic mode and mode transition "ontrol, automatic shutdown provisions fo,r self-pro­teetion, provisions for monitoring system parameters and provisions for inter-facing with ground test instrumentation. .

An extensive test program including components, subsystem and integrated system testing was completed. The overall objectives of the test program were to (1) prove the integration concept of the Air Revitalization System, (2) further advance the Oxygen Generation Subsystem technology, and (3) demons tra,te the hardware maturity of the Oxygen Generation Subsystem components such as electrolysis cells, modules and the Three-Fluid PresSure Controller. Inte­grated t.esting of the experimental Air Revitalization System was conducted for a period of 120 days and included testing at the component, subSystem and total system le~'els.

A total of 480 hours of suceessful integrated operation was aehieved with the Air Revitalization System. Of the total normal operation, two seven-day periods of uninterrupted operation were achieved. A single cell with one of the super electrodes (WAB-6) was subjected to endurance testing. A total of 8,650 hours continuous operation has been accumulated at the "one Ius ion of the current program. Cell voltages du'ring the period of endurance testing remained stable in the range of 1. 462 to 1. 50 V. Opera't~ng eondi tions were set nominally at 352 K (175 F), 161 rnA/em' (I50 ASF) and amhent pressure. A 12-cell module /Ising the super electrodzs (WAB-6) was tested a,t 355 K (180 F), 993 kPa (144 psia) and 161 rnA/em (I50 ASF). Individual eell voltages varied in the range of 1. 47 to 1.50 V, indica'ting the perfo,rmanee of the super electrodes is reprodUcible. In addition, the pressu're controller and another 12-cell module using the advan~ed electrodes (WAB-5) were extensively tested to determine the hardwa re ma'tllri ty .

It is concluded from the results reported herein that the integration concept of the Air Revitalization System is feasible. Hardware and technology of the Oxygen Generation Subsystem has been demonstrated to be close to the preproto­type level. Continueg development of the oxygen generation teehnology is recommended to further reduce the total weight penalties of the Oxygen Genera­tion Subsystem through optimiZation. Successfui completion of this development will p,roduce timely technology necessary to plan future advanced emrironmental control and life suppo,rt system programs and experiments.

2

.... ~. • •• ~ ....... ~ •••• ,... T •• •• • •• ~-:m

Ci/e Sils/ems. !HC.

PROGRAM ACCOMPLISHMENTS

Under Contract NAS2-9795 the following major accomplishments were' made in ~ technology and hardware development of the Oxygen Generation Subsystem (OGS):

• Designed and fabricated a one-person capacity engineering breadboard OGS.

• Integrated and tested the OGS with an experimental Air Revitalization System (ARX-I). Proved the integration concept of the Air Revitaliza­tion System (ARS) is feasible.

• Demonstrated the superior perforlilam:e of advanced water ilectrolysis cells (e.g. cell voltages of 1.45 to 1.50 V at 161 rnA/cm (150 ASF) and 340 K (153 F)) is stable and reliable over a long period of t,ime (greater than 8,650 h).

• Demonstrated that the super electrode (WAB-6) performance was retained through scale-up from single cells to a 12-cell module.

• Demonstrated the hardware maturity of the OGS components such as electrodes, cells, modules and a Three-Fluid Pressure Controller (3-FPC) .

• Developed a Water Handling Subsystem (WHS). Integrated and tested the WHS with the ARX-I.

• Developed automatic, centralized Control/Monitor Instrumentation (C/M 1) for the ARX-1. The central CIM I provided single-button startup, automatic process control and monitoring and automatic fail-safe shutdown.

INTRODUCTION

Regenerative processes for the revitalization of spaeecraft atmospheres are essential for making long-term manned space Iilissions possible. An important step in this overall process is the reclamation of oxygen (0 ) for metabolic consumption through the electrolysis of water. The byproduct hyd·rogen (H2) is used to produce water from metabolically-generated carbon dioxide (C02), The water is then eleetrolyzed to produce O

2 and H

2•

An Oxygen Generation Subsystem (OGS) based on the static feed water eleetrolysis (SFWE) concept has been recognized as a design capable of efficient, reliable O2 generation with few SUbsystem components. The static feed concept has evolved over the past 12 years under the National Aeronautics and Space Adminis­tration (NASA) and Life Systems, Inc. (LSI) sponsorship. Recent developments at LSI allow substantial reductions in the operating voltage levels of water electrolysis cells. This state-of-the-art advancement is significant since the OGS is the largest power eonsUJner of a regenerative Environmental Control/ Life Support System (EC/LSS). The electrolysis power is directly related to the cell volta.ge.

3

.... ~. • •• ~ ....... ~ •••• ,... T •• •• • •• ~-:m

Ci/e Sils/ems. !HC.

PROGRAM ACCOMPLISHMENTS

Under Contract NAS2-9795 the following major accomplishments were' made in ~ technology and hardware development of the Oxygen Generation Subsystem (OGS):

• Designed and fabricated a one-person capacity engineering breadboard OGS.

• Integrated and tested the OGS with an experimental Air Revitalization System (ARX-I). Proved the integration concept of the Air Revitaliza­tion System (ARS) is feasible.

• Demonstrated the superior perforlilam:e of advanced water ilectrolysis cells (e.g. cell voltages of 1.45 to 1.50 V at 161 rnA/cm (150 ASF) and 340 K (153 F)) is stable and reliable over a long period of t,ime (greater than 8,650 h).

• Demonstrated that the super electrode (WAB-6) performance was retained through scale-up from single cells to a 12-cell module.

• Demonstrated the hardware maturity of the OGS components such as electrodes, cells, modules and a Three-Fluid Pressure Controller (3-FPC) .

• Developed a Water Handling Subsystem (WHS). Integrated and tested the WHS with the ARX-I.

• Developed automatic, centralized Control/Monitor Instrumentation (C/M 1) for the ARX-1. The central CIM I provided single-button startup, automatic process control and monitoring and automatic fail-safe shutdown.

INTRODUCTION

Regenerative processes for the revitalization of spaeecraft atmospheres are essential for making long-term manned space Iilissions possible. An important step in this overall process is the reclamation of oxygen (0 ) for metabolic consumption through the electrolysis of water. The byproduct hyd·rogen (H2) is used to produce water from metabolically-generated carbon dioxide (C02), The water is then eleetrolyzed to produce O

2 and H

2•

An Oxygen Generation Subsystem (OGS) based on the static feed water eleetrolysis (SFWE) concept has been recognized as a design capable of efficient, reliable O2 generation with few SUbsystem components. The static feed concept has evolved over the past 12 years under the National Aeronautics and Space Adminis­tration (NASA) and Life Systems, Inc. (LSI) sponsorship. Recent developments at LSI allow substantial reductions in the operating voltage levels of water electrolysis cells. This state-of-the-art advancement is significant since the OGS is the largest power eonsUJner of a regenerative Environmental Control/ Life Support System (EC/LSS). The electrolysis power is directly related to the cell volta.ge.

3

Ci/e Sus/ellis. Inc.

Background

Prior development efforts of water electrolysis cells, moduli::4,nd subsystem:, have included those that use the static water feed concept. l Subsystems using this concept(~ag5 demonstrated an inherent simplicity and long opecating life capabilities.' The OGS, using SFWE, has the potential for the lowen 6) power .. consuming electrolysis subsystem due to the alkaline electrolyte used. ' Various approaches to the static feed design and the resut~' of extensive test programs identified necessary key subsystem improvements. These improvements were made and incorporated into the dtai~~ of the hardware being developed by LSI. Specific improvements included: '

• Reduction in electrolysis cell voltage

• Elimination of water feed compartment degassing

• Elimination of condenser/separa%ors which are characteristic of other applicable water electrolysis subsystems

• Elimination of aerosols in the product gas streams

In 1977 a significant reduction in state-of-the-art cell voltage levels was achieved with a Contractor-developed catalyst for the 02-evolving electrode (Figure 1). Under a previous program (Contract NAS2-8682) sponsored by NASA, a total of 136 days of Single cell operation were acc~ulated with rep,resenta­ti ve cell voltage levels avt1;jging 1. 45 V a,t 161 mAl cm (150 ASF) and 355 K (I80 F) being demonstra,ted.

Program Objectives

The objective of the present program with major emphasis on demonstrating ware maturity at a subsystem level.

was to further advance the OGS technology the subsystem integration concept and hard­Specific objectives were to:

1. Besign and fabricate an engineering breadboard OGS based on SFWE.

2. Integrate and test the OGS with an ARX-l to prove the feasibility of the subsystem integration concept.

3. Bemonstrate the superior performance of previously-developed, advanced water p-lectrolysis cells at both the single cell and staled-up module levels.

4. Bemonstra,te the hardware maturity of the OGS at a subsystem level by endurance testing the ARX-I.

The obj "cti ves of the p'rogram were met.

Program Organization

To meet the above objectives, the program was diVided into five tas,ks plus the documentation a,nd program mana,gement functions. These five tasks were:

en References at end of this report.

4

Ci/e Sus/ellis. Inc.

Background

Prior development efforts of water electrolysis cells, moduli::4,nd subsystem:, have included those that use the static water feed concept. l Subsystems using this concept(~ag5 demonstrated an inherent simplicity and long opecating life capabilities.' The OGS, using SFWE, has the potential for the lowen 6) power .. consuming electrolysis subsystem due to the alkaline electrolyte used. ' Various approaches to the static feed design and the resut~' of extensive test programs identified necessary key subsystem improvements. These improvements were made and incorporated into the dtai~~ of the hardware being developed by LSI. Specific improvements included: '

• Reduction in electrolysis cell voltage

• Elimination of water feed compartment degassing

• Elimination of condenser/separa%ors which are characteristic of other applicable water electrolysis subsystems

• Elimination of aerosols in the product gas streams

In 1977 a significant reduction in state-of-the-art cell voltage levels was achieved with a Contractor-developed catalyst for the 02-evolving electrode (Figure 1). Under a previous program (Contract NAS2-8682) sponsored by NASA, a total of 136 days of Single cell operation were acc~ulated with rep,resenta­ti ve cell voltage levels avt1;jging 1. 45 V a,t 161 mAl cm (150 ASF) and 355 K (I80 F) being demonstra,ted.

Program Objectives

The objective of the present program with major emphasis on demonstrating ware maturity at a subsystem level.

was to further advance the OGS technology the subsystem integration concept and hard­Specific objectives were to:

1. Besign and fabricate an engineering breadboard OGS based on SFWE.

2. Integrate and test the OGS with an ARX-l to prove the feasibility of the subsystem integration concept.

3. Bemonstrate the superior performance of previously-developed, advanced water p-lectrolysis cells at both the single cell and staled-up module levels.

4. Bemonstra,te the hardware maturity of the OGS at a subsystem level by endurance testing the ARX-I.

The obj "cti ves of the p'rogram were met.

Program Organization

To meet the above objectives, the program was diVided into five tas,ks plus the documentation a,nd program mana,gement functions. These five tasks were:

en References at end of this report.

4

In

;~

> . '" ~ '" .... ~ .... .... '" u

o 10.0 .! \0 ", •• 4,.1 •.••. ::1.

1.4

(i) 1(i)(i)

200

Ii

2eiH]) 30(i) ,

Current I!lensity, ASP

400

1965-1969 Technology

4J(i)(i)

500 60.0

S(i)O 6(i)(i)

~

Current Density, rnA/em'·

7(i)(i) 800

FIGURE 1 MAJOR ELECTROI!lE/CATALYST PERFORMANCE IMPROVEMENTS

-,.

9(i)0 100(i)

~',

~ ~ " ~ ~ I !Iii

~ :"

(i) l(i)(i) 2(i)(i) •• "I ••• ! I, ,·",.",4,,1.,

> . '" ~ 2.(i)

'" In .... ~ .... .... , '" u 1.8

, , ;~

1.4

(i) (i) l(i)(i) 2eiH])

FIGURE 1

30(i)

!ilii

3(i)(i) ;

Current I!lensity, ASP

4(i)(i)

1965-1969 Technology

4J(i)(i)

S(i)(i)

S(i)O

6(i)(i) UJG

liJiiIiWl-" :' " , -'.: . .-

6(i)(i) 7(i)(i)

~

Current Density, rnA/cm'-

800

MAJOR ELECTROI!lE/CATALYST PERFORMANCE IMPROVEMENTS

-,.

9(i)0 100(i)

~ ~ " ~ ~ I !Iii

~ :"

ei/e S!ls/ems. IHt.

Task

1.0

2.0

3.0

4.0

5.0

Descriptio~

Design, falJrie:ate and assemble the OGS, the WHS and the CIM I. Integrate the subsystems into the ARK-I.

Develop and calibrate Test Support Accessories (TSA) to enable operation of the OGS within the ARX-I.

Establish, implement and maintain a mini-Product Assurance p,rogram.

Perform a variety of module, sUbsystem and integrated ARX-I testing.

Complete supporting research and development effort to further expand the OGS technology.

AIR REVITALIZATION SYSTEM DEVELOPMENT

A prior program demonstrated that the OGS could be successfully integrated :,jth other air revitalization subsystems into i)4laboratory breadboard Oxygen Recovery System (ORS) at the one-person level. t ) A 30-day endurance test of the OGS, integrated with an Electrochemical Depolarized CO

2 Concentrato,r (EDC)

and a Sabatier-based CO2 Reduction Subsystem (S-CRS), showed that the three subsystems would remove and reduce the metabolieally-generated CO

2 and p,roduce

the required 02 level for one person in a spacecraft application.

The next step in the development of the OGS for the spaeecraft ARS was eompleted as part of the program activities. This activity was the design, fabrica'tion and test of the ARX-I which incorpo,rated the OGS. The philosophy for this "next-step" app,roach was different than in previously integrated laboratory breadboard systems where each of the SUbsystems: (1) were self-contained, (2) had their own CIM I, (3) were started and shut down independently, (4) were tied together by appropriate interfaces and (5) contained redundant components.

The self-contained system (versus subsystem) approach selected for the ARX-I was based on reducing SUbsystem interfaees, elimina'ting redundant components and utilizing the products (Le. heat, electrical power, fluids) of one sub­system in another. As an example, the lI2 generated by the OGS is used by thc EDC and S-CRS. Also,the CIM I was deSigned as a single unit that would opera;te all components as a single system by providing for one-button startupl shutdown of all ARS functions, automatic sequencing and control and monitoring for self-protection and safe operation. The objective of this portion of the program activities was to demonstrate, t.hrough actual testing, the valid,ity of the integration appnach as well as verify the advantages, identify new ones and isola'te shortcomings for futu,re correction.

Concept Deserip,tion

Figure 2 is a block diagram of the self-contained ARS concept. The three prinCipal subsystems (OGS, EDC and S-CRS) needed to provide 02 to and remove CO2 from the creW space are shown.

6

- -, - ~ . .,., -,. .... _- .,"",,~, ............ "" ... , - " ... -..... '-,,'-~,-, .. --~ -... ~--.. --.--~-,- .. --_ .. '--,,_.-.:"~~.: ,-;.t· .. .i_~.::.t,.;.. ''" • .I.J::c .... ,,_~

ei/e S!ls/ems. IHt.

Task

1.0

2.0

3.0

4.0

5.0

Descriptio~

Design, falJrie:ate and assemble the OGS, the WHS and the CIM I. Integrate the subsystems into the ARK-I.

Develop and calibrate Test Support Accessories (TSA) to enable operation of the OGS within the ARX-I.

Establish, implement and maintain a mini-Product Assurance p,rogram.

Perform a variety of module, sUbsystem and integrated ARX-I testing.

Complete supporting research and development effort to further expand the OGS technology.

AIR REVITALIZATION SYSTEM DEVELOPMENT

A prior program demonstrated that the OGS could be successfully integrated :,jth other air revitalization subsystems into i)4laboratory breadboard Oxygen Recovery System (ORS) at the one-person level. t ) A 30-day endurance test of the OGS, integrated with an Electrochemical Depolarized CO

2 Concentrato,r (EDC)

and a Sabatier-based CO2 Reduction Subsystem (S-CRS), showed that the three subsystems would remove and reduce the metabolieally-generated CO

2 and p,roduce

the required 02 level for one person in a spacecraft application.

The next step in the development of the OGS for the spaeecraft ARS was eompleted as part of the program activities. This activity was the design, fabrica'tion and test of the ARX-I which incorpo,rated the OGS. The philosophy for this "next-step" app,roach was different than in previously integrated laboratory breadboard systems where each of the SUbsystems: (1) were self-contained, (2) had their own CIM I, (3) were started and shut down independently, (4) were tied together by appropriate interfaces and (5) contained redundant components.

The self-contained system (versus subsystem) approach selected for the ARX-I was based on reducing SUbsystem interfaees, elimina'ting redundant components and utilizing the products (Le. heat, electrical power, fluids) of one sub­system in another. As an example, the lI2 generated by the OGS is used by thc EDC and S-CRS. Also,the CIM I was deSigned as a single unit that would opera;te all components as a single system by providing for one-button startupl shutdown of all ARS functions, automatic sequencing and control and monitoring for self-protection and safe operation. The objective of this portion of the program activities was to demonstrate, t.hrough actual testing, the valid,ity of the integration appnach as well as verify the advantages, identify new ones and isola'te shortcomings for futu,re correction.

Concept Deserip,tion

Figure 2 is a block diagram of the self-contained ARS concept. The three prinCipal subsystems (OGS, EDC and S-CRS) needed to provide 02 to and remove CO2 from the creW space are shown.

6

- -, - ~ . .,., -,. .... _- .,"",,~, ............ "" ... , - " ... -..... '-,,'-~,-, .. --~ -... ~--.. --.--~-,- .. --_ .. '--" .. -.:<: ,-;.t· .. .i_~.::.t,.;..''"·.I.J::c .... ,,_~

.-.,. '.:

•

Air + 1:12° t Air + CO

2 + H

2Q

I Air + eo, Crew Cabin HlIIDidity Space I Cantral Sl:lbsystem

•

j l. H (') H 2 ' 2

" I

Pz N FI 2 I "

2 .. ,

'. '1

• I

, ,

..... Wa,ter Handling H <'l

Subsystem' r 2

I

II I I

I

i ~

, I ~ , !

" Nitragen I

Supply NO , 2 I Sabsystem

I

Oxygen Generatian I

Sabsys,tem

FIG{I]RE 2 AIR :~EVIlf"'UZAnON SYSTEM BLOCK fil[AGPAM

, ,~" '-r:"

-'''''r

I Electrachemical

filepalarized Carban filiaxMe Cancentratar

Ii

CO2 + H2

Sabatier Ca,rban filiaxide ~

Redactian Sabsystem !

',',

CH4

~ 'S\ 'Ii

~ ~ ~ !'l

~ r"

"

::; "

"

• .j.

"

i

"",'-,----~ ,--.,..-'

.-.--

•

• Air + CO2 + H2O I ,

Air + CO2 Electrachemical Crew Cabin HlIIDidity filepalarized Space , Cantral Sl:lbsystem Carban filiaxMe

Cancentratar

~ l. H (') H I 2 . 2 ,. ,

., i

Pz N FI CO2 + H 2

1'\. 2 , 2 /

,

" 'I

,

, ,

Wa,ter Handling H <'l Subsystem·

,. 2 Sabatier

: !

,

Carban filiaxide , ,

: Redactian Sabsystem !

i ,

,

!

, Nitragen ,

Supply NO ! 2 I

Sabsystem

I

<'lxygen Generatian ,

Sabsys,tem

FIG{I]RE 2 AIR :~EVIlf"'UZAnON SYSTEM BLOCK fil[AGPAM

Cite SlI.slellls. IHC.

Additional subsystems and components are needed to provide other air ~evitali­zation functions. A Nitrogen (N

2) Supply Subsystem (N8S) using decomposition

of hydrazine (N2"4) provides for N2 lost through cabin leakage. Also, the NSS supplies extra H2 required by the S-CRS. A Cabin Humidity Control Subsystem (CHCS) is used to supply conditioned air to the EDC at a humidity level which results in optimum efficiency and to remove the metabolically- and EDC-produced moisture from the cabin air. A WIIS collects, stores and distributes process wa ter to the OGS. Finally, th" centralize.d C/~I I provides for automatic, integrated operation. Tabl" 1 lists the design requirements established for the ARX-I. Of particular note is the net 02 generation rate which inclujes 02 for crew consumption and a provision for overboard leakage.

The activities associated with the development of the EDC, CHCS, NSS and portions of the Cm I for(§h'fo,RX-I were funded under separate NASA Ames Research Center programs. The development associated with the S-CRS and its major components were supported by Contractor funds. Only the OGS develop­ment and part of both the WHS and C/~I I development.s were funded thr.ough this contract.

Details of the OGS, WIIS and C/N I for the ARX-I are discussed in the Subsystem Development section of this report. Only highlights of the ARX-I design are described below.

Hardware Description

The mechanical hardware of the ARX-l was packaged as a single unit as shown in Figure 3. Identified in Figure 3 are the OGS module, the Sabatier reactor aud modules of the EDC and NSS. Components of the WIIS are distributed throughout the system. This breadboard system has a t0tal weigh,t 0f 281 kg (619 Ib) and occupies an evel<>pe of 71 x 96 x 114 cm (28 x 38 x 45 in). The ARX-I mechanical hardware with its C/H I and TSA, which comprille the test facility, is shown in Figure 4. A detailed flow schematic of the ARX-I is presented in Appendix 1.

The C/~I I of the ARX-I employs an advanced instrwnentation concept which is highligh,ted by minicomputer-based controls and monitors. The C/N I was pack­aged in a separate enclosure shown in Figur'e 5. The function of the C/M I is to provide automatic mode and nwde transiti0n control, automatic shutdown pro­visicns for self-protection, system parameter monitoring and ground test instrumentation interface.

8UBSYSTEN I!lEVELOP~IENTS

~Iajor program activities were focused on the deve10pmeJllt of the OGS. The following sections describe the OGS, the WIIS and the C/N I. Eml'hasis is placed on the OGS development.

Oxygen Gene .. a tion Subsys,tem

The primary objective of an OGS is to produce O2 for metab01ic consumption. The byproduct H2 is used in processes for cOllcentra'ting and redllcing CO2 , The OGS developed employed the SFWE concept.

8

.. ,-~, ,., ,

•

Cite SlI.slellls. IHC.

Additional subsystems and components are needed to provide other air ~evitali­zation functions. A Nitrogen (N

2) Supply Subsystem (N8S) using decomposition

of hydrazine (N2"4) provides for N2 lost through cabin leakage. Also, the NSS supplies extra H2 required by the S-CRS. A Cabin Humidity Control Subsystem (CHCS) is used to supply conditioned air to the EDC at a humidity level which results in optimum efficiency and to remove the metabolically- and EDC-produced moisture from the cabin air. A WIIS collects, stores and distributes process wa ter to the OGS. Finally, th" centralize.d C/~I I provides for automatic, integrated operation. Tabl" 1 lists the design requirements established for the ARX-I. Of particular note is the net 02 generation rate which inclujes 02 for crew consumption and a provision for overboard leakage.

The activities associated with the development of the EDC, CHCS, NSS and portions of the Cm I for(§h'fo,RX-I were funded under separate NASA Ames Research Center programs. The development associated with the S-CRS and its major components were supported by Contractor funds. Only the OGS develop­ment and part of both the WHS and C/~I I development.s were funded thr.ough this contract.

Details of the OGS, WIIS and C/N I for the ARX-I are discussed in the Subsystem Development section of this report. Only highlights of the ARX-I design are described below.

Hardware Description

The mechanical hardware of the ARX-l was packaged as a single unit as shown in Figure 3. Identified in Figure 3 are the OGS module, the Sabatier reactor aud modules of the EDC and NSS. Components of the WIIS are distributed throughout the system. This breadboard system has a t0tal weigh,t 0f 281 kg (619 Ib) and occupies an evel<>pe of 71 x 96 x 114 cm (28 x 38 x 45 in). The ARX-I mechanical hardware with its C/H I and TSA, which comprille the test facility, is shown in Figure 4. A detailed flow schematic of the ARX-I is presented in Appendix 1.

The C/~I I of the ARX-I employs an advanced instrwnentation concept which is highligh,ted by minicomputer-based controls and monitors. The C/N I was pack­aged in a separate enclosure shown in Figur'e 5. The function of the C/M I is to provide automatic mode and nwde transiti0n control, automatic shutdown pro­visicns for self-protection, system parameter monitoring and ground test instrumentation interface.

8UBSYSTEN I!lEVELOP~IENTS

~Iajor program activities were focused on the deve10pmeJllt of the OGS. The following sections describe the OGS, the WIIS and the C/N I. Eml'hasis is placed on the OGS development.

Oxygen Gene .. a tion Subsys,tem

The primary objective of an OGS is to produce O2 for metab01ic consumption. The byproduct H2 is used in processes for cOllcentra'ting and redllcing CO2 , The OGS developed employed the SFWE concept.

8

.. '-', ,., ,

•

,. •

TABLE lONE-PERSON AIR REVITALIZATION SYSTEM DESIGN REQIDIREMENTS

Crew Size

CO2 Removal Ra,te, kg/d (lb/d)

02 Generation Rate, kg/d (Ibid)

Water Vapor Removal Rate, kg/d (lb/d)

Liquid Wa,ter Production Ra,te, kg/d (Ibid)

CH4 Praduction Rate, kg/d (Ibid)

N2 Production Rate, kg/d (Ibid)

1

1.00

1.03

1.80

1.49

0.36

0.60

i ei/e SlIsleHis. Inc. 1

(2.20)

(2.27)(a)

(3.96)

(3.27)

(0.79)

(1. 32)

(a) Cansists of 0.84 kg/d (1.84 Ibid) 02 metabolic and 0.19 kg/d (0.43 Ibid) for leakage requirements.

9

,. •

TABLE lONE-PERSON AIR REVITALIZATION SYSTEM DESIGN REQIDIREMENTS

Crew Size

CO2 Removal Ra,te, kg/d (lb/d)

02 Generation Rate, kg/d (Ibid)

Water Vapor Removal Rate, kg/d (lb/d)

Liquid Wa,ter Production Ra,te, kg/d (Ibid)

CH4 Praduction Rate, kg/d (Ibid)

N2 Production Rate, kg/d (Ibid)

1

1.00

1.03

1.80

1.49

0.36

0.60

i ei/e SlIsleHis. Inc. 1

(2.20)

(2.27)(a)

(3.96)

(3.27)

(0.79)

(1. 32)

(a) Cansists of 0.84 kg/d (1.84 Ibid) 02 metabolic and 0.19 kg/d (0.43 Ibid) for leakage requirements.

9

CHCS Heat Exchanger

Sabatier Reactor

FIGURE 3

EDC Module

A1!X-l MECHANICAL lIAllDWAlIE

10

NSS Hodule

ORiCIHM. PAM • OF POOR 951.1' n

CliCS Heat Exchanger

Sabatier Reactor

FIGURE 3

EDC Module

AlIX-l MECHANICAL HARDWARE

10

NSS ~lodule

ORiCIHAL NGI • OF POOR sa.' Il'

.. ..

Parametric Data Display

--I

~I

Air Supply Unit (ASU) C/M I

Fluid Supply Unit

FIGURE 4 ARX-I TEST FACILITY

, .

~~ Mechanical

Control/Monitor Instrumentation (C/M I)

h ~ ~ ~ I ~

~ :'i

.. ..

Parametric Data Display

Air Supply Unit (ASU) elM I

Supply Unit

FIGURE 4 ARX-I TEST FACILITY

Mechanical -::"1"'--'

Hydrazine Storage and Supply

Control/Monitor Instrumentation (C/M I)

Cife S,lleMI, Jilt.

Sy.t.... Statu8 j' t,

Message Display Scree" r--"'"

r

\

FIGURE 5 ARX-I CONTROL AND MONITOR INSTRUMENTATION

12 " .Qi,'JAL PAGE IS OF POOR QlJALITY ...

Cife S,lfeMI. lllc.

System Statu8

Message Display ___ ~_ Scree ... l ;-

-~ ....

I

\

'. '- .'-

FIGURE 5 ARX-l CONTROL AND MONITOR INSTRUMENTATION

12 d.QI.'IAL PAGE IS OF POOR Q!JALITY .. .

t,"

Cifo S,Is/eIllS. IHCo

Static Feed Water Electrolysis

Detailed descriptions of the SFWE process have been discussed pr~viously.(2) The following summarizes its concept and the electrochemical processes.

Static Feed Water Electrolysis Concept. A conceptual schematic of an OGS based on the SFWE concept is shown in Figure 6. The subsystem consists of three main parts: an electrochemical module, a water feed tank and a pressure controller.

The module generates 02 and H2 from wa,ter supplied by the water feed tank. The water feed tank is cyclically filled as required from the collection points within the EC/LSS (e.g., CO2 Reduction Subsystem). The pressure con­troller (a) maintains the absolute pressu,re of the subsystem, (b) maintains the pressure differentials required to establish and maintain fluid (H20 and electrolyte) locations within the individual cells of the module and (c) controls pressurization and depressuriza,tion of the subsystem during mode transitions (i.e., start-ups and shutdowns).

Figure 7 is a functional schematic of one of the electrochemical cells which are installed electrically in series in the electrolysis module. Basically, a single cell consists of an electrode assembly, product gas cavities for H2 and °2 , a feed water compartment and a coolant compartment for tempera,ture control. The electrode assembly consists of a cathode, asbestos ma'trix and an anode. The N2 purge line is activated during sta,rtup and pressurization, shutdown or in case of emergency. All fluid interfaces are manifolded w;,th the respective ones of other cells in the module.

The overall static water feed concept operates as follows. Initially, the feed water compartment and the electrode assembly contain an aqueous solution of KOH electrolyte at an equal concentration. Both the H2 and 02 cavities are void of liquid. An equilibrium condition exists prior to start of electrolysis. When power is applied to the electrodes, water from the cell electrolyte is decomposed. As a result, the concentration of the cell electrolyte increases and its water vapor pressure decreases to a level below that of the feed compartment electrolyte. This water vapor pressu,re differential is a driving force causing water vapor to diffuse from the liquid gas interface within the water feed matrix, through the H2 cavity and cathode electrode, into the cell electrolyte. This process establishes new steady-state conditions based on the water requirements for electrolysis.

As water evapo'ra,tes from the feed water compartment it is statically replen­ished from the water feed tank to maintain a constant pressure within the feed compartment. Bpon interruption of electrical power, water vapor will continue to diffuse across the H2 compartment until the electrolyte concentra,tion in the cell matrix is equal to that of the water feed compartment. At this point the original equilibrium condition is reestablished with the electrolyte having the initial charge concentration.

13

Cifo S,Is/eIllS. IHCo

Static Feed Water Electrolysis

Detailed descriptions of the SFWE process have been discussed pr~viously.(2) The following summarizes its concept and the electrochemical processes.

Static Feed Water Electrolysis Concept. A conceptual schematic of an OGS based on the SFWE concept is shown in Figure 6. The subsystem consists of three main parts: an electrochemical module, a water feed tank and a pressure controller.

The module generates 02 and H2 from wa,ter supplied by the water feed tank. The water feed tank is cyclically filled as required from the collection points within the EC/LSS (e.g., CO2 Reduction Subsystem). The pressure con­troller (a) maintains the absolute pressu·re of the subsystem, (b) maintains the pressure differentials required to establish and maintain fluid (H20 and electrolyte) locations within the individual cells of the module and (c) controls pressurization and depressuriza,tion of the subsystem during mode transitions (i.e., start-ups and shutdowns).

Figure 7 is a functional schematic of one of the electrochemical cells which are installed electrically in series in the electrolysis module. Basically, a single cell consists of an electrode assembly, product gas cavities for H2 and °2 , a feed water compartment and a coolant compartment for tempera,ture control. The electrode assembly consists of a cathode, asbestos ma'trix and an anode. The N2 purge line is activated during sta,rtup and pressurization, shutdown or in case of emergency. All fluid interfaces are manifolded w;,th the respective ones of other cells in the module.

The overall static water feed concept operates as follows. Initially, the feed water compartment and the electrode assembly contain an aqueous solution of KOH electrolyte at an equal concentration. Both the H2 and 02 cavities are void of liquid. An equilibrium condition exists prior to start of electrolysis. When power is applied to the electrodes, water from the cell electrolyte is decomposed. As a resul t, the concentra·tion of the cell electrolyte increases and its water vapor pressure decreases to a level below that of the feed compartment electrolyte. This water vapor pressu,re differential is a driving force causing water vapor to diffuse from the liquid gas interface within the water feed matrix, through the H2 cavity and cathode electrode, into the cell electrolyte. This process establishes new steady-state conditions based on the water requirements for electrolysis.

As water evapo'ra,tes from the feed water compartment it is statically replen­ished from the water feed tank to maintain a constant pressure within the feed compartment. Bpon interruption of electrical power, water vapor will continue to diffuse across the H2 compartment until the electrolyte concentra·tion in the cell matrix is equal to that of the water feed compartment. At this point the original equilibrium condition is reestablished with the electrolyte having the initial charge concentration.

13

, •. -. r-,'- -, -" ....... ~, _.,

Ci/e SlIsleHls, IHf.

Electrolysis Module

Product Gas Pressure Controller 1---------------, , ,

~--I

L_·· ___ . __ ~ ______ J

Water Feed Tank

FIGURE 6 STATIC FEED WAtER ELECTRoLYSIS CONCEPT

14

"

Ci/e SlIsleHls, IHf.

Electrolysis Module

Product Gas Pressure Controller 1---------------, , ,

L_·· ___ . __ ~ ______ J

. --

Water Feed Tank

FIGURE 6 STATIC FEED WATER ELECTRoLYSIS CONCEPT

14

"

'.:

l , ut •

H20 Feed

Matrix ~

Water Fee Cavity ~ Cavity

Cathode ( -)

Polysul Parts

fone

Water Fee d

/"

e

~.

~ )

.r-

""-... . 1--,.. ..

I'--. - '- ~

J

Cite S,IsleIllS. Inc.

COnstant Current

Power Supply

- -e

I I. • Ir=0 I . • C

2 Output oolant OUt

" t::: 1

' " ~~ i'-. ~ ~~ ~

I:::: ~.

~ .. ~

~

I:'"

.~

L,.;

f... p

I'--.L.oo.:' ... " ....., ...

~.

r-.... t'-

~ .....

"'- .....

'"

....

.... r--. "-t--,... ~

r--- I"-r-.. f

-C ell Matrix With Electrolyte

. .

Z:: ... ~

Liquid Coolant Cavity

02 Cavity

Anode (+)

Liquid Coolant Cavity Separator

Coolant In

Purge N2 Inputs

FIGURE 7 FUNCTllONAL SCHEMATIC OF AN SFWE CELl.

15

'.:

l , ut •

H20 Feed Matrix ~

Water Fee Cavity ~ Cavity

Cathode (- )

e

~.

~ ~

.r-

COnstant Current

Power Supply

- e

I ~

".' I' r--~ r--" " ,,~,

"" ::::

~

~ .. ~

~

~

::::

"'"

Cite S,IsleIllS. Inc.

-02 Output Coolant OUt Ir=.

"- I'

~ ~ r--i'. ~

J--

~ ~

Cell Matrix With Electrolyte

Liquid Coolant Cavity

02 Cavity

Anode (+)

Liquid Coolant Cavity Separator

Polysul£ Parts

one / .. " '" ...... P"' I'- ....... ~

. ........ "'" ... "'" ~

Water Fee

. . ~. t'---. .......

- '- ~ " d

~

f . .

Z:: ... '<J

Coolant In

Purge N2 Inputs

FIGURE 7 FUNCTllONAL SCHEMATIC OF AN SFWE CELl.

15

eife Sus/elliS, /Ht.

Electrochemical Process. The electrochemical process of water electrolysis occurs within the cell's electrode assembly. The reactions occurring at the anode and cathode of the electrolysis cell with an alkaline electroly~e are:

Cathode

- -2e + 2H2

O = H2 + 20H

i\nod~

-20H = H20 + 1/2 02 + 2e

resulting in the overall rea.ction of

electrical energy + H20 = H2 + 1/2 02 + heat

The flow rates of product gases are given by

where G = I = N =

11 = c n = F =

G '" IN '1 /(nF) c

product gas flow rates, g~males/sec, current, A number af cells in series current efficiency number of electrons involved in reaction (1) or (2) to praduce a molecule of a product gas Faraday's canstant, 96479 coulamb/equivalent

The current efficiency, I'J , may be defined as c

(1)

(2)

(3)

(4)

I'J = W /W (5) cat

where W = weight of desired product actually obtained and W = weight of desiredap'raduct if current had been used solely to produce tlie desired product. Current efficiency is influenced by current density.

In analyzing calcula,ted.

electrachemical pracesses, energy efficiencies are Energy efficiency, '1 may be defined as follaws:

e

'1 = Et/E ea

alsa frequently

(6)

where E = energy theoretically required, based an the decompasition voltage and on the amaunt of desired p,raduct actually obtained and E "actual energy input. The energy efficiency calculation may be based on th~ anode p,roduct o,r an the cathade product. If the current efficiencies for the anade and cathade are the same, energy efficiency may be calculated as:

where V = decomposition valtage and V = actual cell valtage. The decomposi~ tion vo~tage is a function of operatin~ temperatu,re and pressure. The decom­position voltage af wa,ter at 298 K (77 F) and atmospheric pressure is 1.229 V.

16

eife Sus/elliS, /Ht.

Electrochemical Process. The electrochemical process of water electrolysis occurs within the cell's electrode assembly. The reactions occurring at the anode and cathode of the electrolysis cell with an alkaline electroly~e are:

Cathode

- -2e + 2H2

O = H2 + 20H

i\nod~

-20H = H20 + 1/2 02 + 2e

resulting in the overall rea.ction of

electrical energy + H20 = H2 + 1/2 02 + heat

The flow rates of product gases are given by

where G = I = N =

11 = c n = F =

G '" IN '1 /(nF) c

product gas flow rates, g~males/sec, current, A number af cells in series current efficiency number of electrons involved in reaction (1) or (2) to praduce a molecule of a product gas Faraday's canstant, 96479 coulamb/equivalent

The current efficiency, I'J , may be defined as c

(1)

(2)

(3)

(4)

I'J = W /W (5) cat

where W = weight of desired product actually obtained and W = weight of desiredap'raduct if current had been used solely to produce tlie desired product. Current efficiency is influenced by current density.

In analyzing calcula,ted.

electrachemical pracesses, energy efficiencies are Energy efficiency, '1 may be defined as follaws:

e

'1 = Et/E ea

alsa frequently

(6)

where E = energy theoretically required, based an the decompasition voltage and on the amaunt of desired p,raduct actually obtained and E "actual energy input. The energy efficiency calculation may be based on th~ anode p,roduct o,r an the cathade product. If the current efficiencies for the anade and cathade are the same, energy efficiency may be calculated as:

where V = decomposition valtage and V = actual cell valtage. The decomposi~ tion vo~tage is a function of operatin~ temperatu,re and pressure. The decom­position voltage af wa,ter at 298 K (77 F) and atmospheric pressure is 1.229 V.

16

Cife S,Islellls. /Ht.

Oxygen Generation liubsystem Descriptions

Design Specifications. The OGS was designed to deliver 02 at a rate of 1.46 kg/d (3.22 lb/d) which included 0.83 kg/d (1.84 Ibid) 02 for metabolic consumption and 0.63 kg/d (1.38 Ibid) for other requirements such as EDC consumption and cabin leakage makeup. Details of the OGS design speCifications are presented in Table 2.

Schematic and Operation. The OGS schematic is shown in Figure 8. Basically, the OGS operates as described in the previous section. The water feed tank is periodically filled with water which is being treated by a deionizer. During normal operation the valve (13A), located downstream of the deionizer, is closed. Feed water is statically replenished to the electrolysis module as the water in the aqueous electrolyte solution is being electrolyzed.

A list of the OGS mechanical components is presented in Table 3. The 3-FPC is the key component which maintains the system pressure (water-feed tank pressure) and pressures of the product gases and their respect:ive compartments in the module.

Temperature of the electrolysis module is kept uniform and constant by cir­culating water through the coolant cavities of the electrolysis cells. The module temperature can be varied for parametric testing by the use of electrical heaters, installed in the module endplates, and a liquid-to~air heat exchanger. A diverter valve in the coolant loop adjusts the water, flow rate through the heat exchanger to maintain a constant module temperature.

Both the 02 and H? compartments of each cell can be purged with N2

. The flow of the N2 purge s~ream is regulated by orifices upstream of the module. The N2 purging is not only a safety feature but also prevents module pressure from going subatmospheric due to the reaction of H2 and 02 after shutdown or isolation.

The nominal operating conditions of the OGS are presented in T!!ble 4. The electrolysis module operated at a current density of 197 rnA/em (183 ASF) to ensure that the OGS delivers 02 at a rate equal to or greater than the speci­fied production rate of 1.46 kg/d (3.22 Ibid). The module temperature and p'ressure were set at 339 K (150 F) and 1,068 kPa (155 psia), respectively. The initial module charge concentration of KOH was 25% by weight.

Hardware ])escriptions. Unique components of the OGS design are the electro­chemical module and the 3-FPC. The remaining ancillary components were either commercially available or other 1,SI state-of-the-art hardware.

The design of the SFWE Module (SFWEM) was based on the single-cell components shown in Figure 9. Twelve electrolysis cells were assembled using an endplate­to-endplate concept to minimize interconnecting plumb~ng, as s20wn in Figure 10. The active electrode area of a single cell is 92.9 em (0.1 ft). The elec­trolysis cells were interconnected in series electrically. All fluid connec­tions were. made in ~arallel. , D?'z1iled descriptions of the design have beer. presented l.n a p,revl.ous report.'

17

Cife S,Islellls. /Ht.

Oxygen Generation liubsystem Descriptions

Design Specifications. The OGS was designed to deliver 02 at a rate of 1.46 kg/d (3.22 lb/d) which included 0.83 kg/d (1.84 Ibid) 02 for metabolic consumption and 0.63 kg/d (1.38 Ibid) for other requirements such as EDC consumption and cabin leakage makeup. Details of the OGS design speCifications are presented in Table 2.

Schematic and Operation. The OGS schematic is shown in Figure 8. Basically, the OGS operates as described in the previous section. The water feed tank is periodically filled with water which is being treated by a deionizer. During normal operation the valve (13A), located downstream of the deionizer, is closed. Feed water is statically replenished to the electrolysis module as the water in the aqueous electrolyte solution is being electrolyzed.

A list of the OGS mechanical components is presented in Table 3. The 3-FPC is the key component which maintains the system pressure (water-feed tank pressure) and pressures of the product gases and their respect:ive compartments in the module.

Temperature of the electrolysis module is kept uniform and constant by cir­culating water through the coolant cavities of the electrolysis cells. The module temperature can be varied for parametric testing by the use of electrical heaters, installed in the module endplates, and a liquid-to~air heat exchanger. A diverter valve in the coolant loop adjusts the water, flow rate through the heat exchanger to maintain a constant module temperature.

Both the 02 and H? compartments of each cell can be purged with N2

. The flow of the N2 purge s~ream is regulated by orifices upstream of the module. The N2 purging is not only a safety feature but also prevents module pressure from going subatmospheric due to the reaction of H2 and 02 after shutdown or isolation.

The nominal operating conditions of the OGS are presented in T!!ble 4. The electrolysis module operated at a current density of 197 rnA/em (183 ASF) to ensure that the OGS delivers 02 at a rate equal to or greater than the speci­fied production rate of 1.46 kg/d (3.22 Ibid). The module temperature and p'ressure were set at 339 K (150 F) and 1,068 kPa (155 psia), respectively. The initial module charge concentration of KOH was 25% by weight.

Hardware ])escriptions. Unique components of the OGS design are the electro­chemical module and the 3-FPC. The remaining ancillary components were either commercially available or other 1,SI state-of-the-art hardware.

The design of the SFWE Module (SFWEM) was based on the single-cell components shown in Figure 9. Twelve electrolysis cells were assembled using an endplate­to-endplate concept to minimize interconnecting plumb~ng, as s20wn in Figure 10. The active electrode area of a single cell is 92.9 em (0.1 ft). The elec­trolysis cells were interconnected in series electrically. All fluid connec­tions were. made in ~arallel. , D?'z1iled descriptions of the design have beer. presented l.n a p,revl.ous report.'

17

Cife SlIs/eHis. !Ht.

TABLE 2 OGS DESIGN SPECIFICATIONS

Crew Size

02 Generation Rate(a), kg/d (lb/d)

H2 Generation Rate, kg/d (Ib/d)

Water Supply Pressure, kPa (psia) Temperature, K (F)

Cooling Air Total' Pressure, kPa (psia) Tempenture, K (F)

Pllrge Gas Supply Type Pressure, kPa (psia)

Electrical Power, V DC AC

Gravity, g

Duty Cycle

1

1. 46 (3.22)

0.18 (0.41)

207 (30) 277 to 300 (40 to 80)

101 (14.7) 294 (70)

N 9~5 (140)

24 115/200 (60 Hz,

1 and 3 Phase)

o to 1

Continuous

(a) Includes 0.83 kg/d (1.84 lb/d) 02 for metabolic consumption and 0.63 kg/d (1.38 lb/d) for other requiremen,ts such as eabin leak­age ma,keup and EDC consumption.

18

Cife SlIs/eHis. !Ht.

TABLE 2 OGS DESIGN SPECIFICATIONS

Crew Size

02 Generation Rate(a), kg/d (lb/d)

H2 Generation Rate, kg/d (Ib/d)

Water Supply Pressure, kPa (psia) Temperature, K (F)

Cooling Air Total' Pressure, kPa (psia) Tempenture, K (F)

Pllrge Gas Supply Type Pressure, kPa (psia)

Electrical Power, V DC AC

Gravity, g

Duty Cycle

1

1. 46 (3.22)

0.18 (0.41)

207 (30) 277 to 300 (40 to 80)

101 (14.7) 294 (70)

N 9~5 (140)

24 115/200 (60 Hz,

1 and 3 Phase)

o to 1

Continuous

(a) Includes 0.83 kg/d (1.84 lb/d) 02 for metabolic consumption and 0.63 kg/d (1.38 lb/d) for other requiremen,ts such as eabin leak­age ma,keup and EDC consumption.

18

,.

Cifo S!lS/CIIIS, JH~.

Water In

13A

13C

13D

13F

IOC

13G

N2 Purge "';'_~ ___ .L)'--"~--":}---(cI~--"'I"""~-I In

Elec. Power.-- ------.~-----

In I : I I

Accumulator

14

Out

10D

.-___ -!_ H2 Out to EDC

Static Feed Water

Elec.trolysis

2

1

I Coolant I

Pump I r---- --~l I .....-.J~...,.,..I, I I I

L _______ J I 7 I

Power Controller 6 Valve

Ambient~--- .. --~-- 1-__ . -. ___ ~::::b;;~~=~~_· ___ .. Ambient Air I L.-...... ~-~ I Air . . . I Ex=::ger I

Note: Numbers shown adjacent to cot!lponents refer to part numbers used in Table 3.

FIGNRE 8 OGS FLOW SCH~TIC

19

Cifo S!lS/CIIIS, JH~.

Water In

13A

13C

13D

13F

10C

N2 Purge --+-~---D..-'4P-~-""0---{: Il·--' .... ~-I In

11B lOB

Elec. Power.-- ------.~-----

In I : I I

Accumulator

14 Power

I lOD I

2

Static Feed Water

Elec.trolysis 1

I Coolant I

Pump I r---- --~l I C"-~h.- 1/ I I I

L___ _ __J I 7 I

Out

H2 Out to EDC

Controller 6 Valve

Ambient~--- .. ----- 1----. -. ___ ~~b;;::f::=~~· ____ ... Ambient Air I L.-........ ~_...-J I Air ... I Heat

Exchanger I Note: Numbers shown adjacent to cOl!lponents refer to part numbers

used in Table 3.

FIGNRE 8 OGS FLOW SCH~TIC

19

ei/e Sus/ellis. IHC. ~~~~--------------------------------------------------------

TABL~ 3 OGS MECHANICAL COMPONENT LIST

Part Number Identifit~~ion No. Component Required C()de

1 Electrochemical Module 1 WEl/DMI

2 Three-Fluid Pressure Controller 1 PCl

3 Water Storage Tank 1 WSTI

4 Coolant Pump 1 M3

5 Coolant Accumulato,r 1 WA2

6 Liquid/Air Heat Exchanger 1 HX3

7 Coolant Flow Diverter Valve I V22

8 Feed Water Deionizer 1 WDI

9 Product Gas Filter 2 AF3, 4

10 Orifice 4 R4, 5, 7, 8

11 Check Valve 2 eVl, 2

12 Hand Valve 1 MVlO

13 Solenoid Valve 7 V9, 10, 11, 12 16, 17, 18

14 Power Controller 1

(a) As used in ARX~l System Schematic, LSI-J-1407, (Appendix 1).

20

ei/e Sus/ellis. IHC. ~--~------------------------------------------------

TABL~ 3 OGS MECHANICAL COMPONENT LIST

Part Number Identifit~~ion No. Component Required C()de

1 Electrochemical Module 1 WEl/DMI

2 Three-Fluid Pressure Controller 1 PCl

3 Water Storage Tank 1 WSTI

4 Coolant Pump 1 M3

5 Coolant Accumulato,r 1 WA2

6 Liquid/Air Heat Exchanger 1 HX3

7 Coolant Flow Diverter Valve I V22

8 Feed Water Deionizer 1 WDI

9 Product Gas Filter 2 AF3, 4

10 Orifice 4 R4, 5, 7, 8

11 Check Valve 2 eVl, 2

12 Hand Valve 1 MVlO

13 Solenoid Valve 7 V9, 10, 11, 12 16, 17, 18

14 Power Controller 1

(a) As used in ARX~l System Schematic, LSI-J-1407, (Appendix 1).

20

. - ' ... ' .. " ... _.; ',,", . '., .',-",' ': ,' ..

TABLE 4 OGS NOMINAL OPERATING CONDITIONS

Current, A

Current Density, mA/cm2 (ASF)

Average Cell Voltage, V

Module Temperature, K (F)

Pressures

• • • •

H20 Feed, kPa (psia) H2-to-H20 Differential, kPa (psid) 02-to-H20 Differential, kPa (psid) N2 Purge, kPa (psia)

Flow Rates, kg/d (Ibid)

• • •

H20 Feed

02 Product H2 Product

Electrolyte Charge Concentration, wt %

Cife Sf/stems. Inc.

18.3

197 (183)

1. 5 (a)

339 (150)

1069 (155) 17.2 (2.5) 27.6 (4.0) 965 (140)

1.75 (3.86) 1.55 (3.43) 0.20 (0.43)

25% KOH

(a) Wl.th super electr<>des; 1.7 V with advanced electrodes.

21

. - ' ... ' .. " ... _.; ',,", . '., .',-",' ': ,' ..

TABLE 4 OGS NOMINAL OPERATING CONDITIONS

Current, A

Current Density, mA/cm2 (ASF)

Average Cell Voltage, V

Module Temperature, K (F)

Pressures

• • • •

H20 Feed, kPa (psia) H2-to-H20 Differential, kPa (psid) 02-to-H20 Differential, kPa (psid) N2 Purge, kPa (psia)

Flow Rates, kg/d (Ibid)

• • •

H20 Feed

02 Product H2 Product

Electrolyte Charge Concentration, wt %

Cife Sf/stems. Inc.

18.3

197 (183)

1. 5 (a)

339 (150)

1069 (155) 17.2 (2.5) 27.6 (4.0) 965 (140)

1.75 (3.86) 1.55 (3.43) 0.20 (0.43)

25% KOH

(a) Wl.th super electr<>des; 1.7 V with advanced electrodes.

21

N N

!J 2! :lO r-

g: .~ li) ,... '" ~ iii

. . •• •••

FIGURE 9 SINGLE-CELL PARTS

h ~ ~ ~ a ~

~ :'"

N N

:J 0 > "' r­

oO ." "'': > .~ li) :- fIY

:J iii

FIGURE 9 SINGLE-CELL PARTS

h ~ ~ ~ a ~

~ :"

Water Feed

Cite S,Is/eIllS. IHf.

FIGURE 10 STATIC FEED WATER ELECTROLYSIS MODULE

23

Thermocouple Wells

Water Feed Compartment

kceas

Cite S,Is/ells. IHf.

Thermocouple Welle

FIGURE 10 STATIC FEED WATER ELECTROLYSIS MODULE

23

£i/f SlIstcHls, IHC.

The 3-FPC .. as developed to meet the unique fluidic and pressure control require­ments of the OGS. It combined, in a single assembly, the sensors and actuators necessary to control and monitor fluid pressure levels and differentials during all operating modes including steady-state, startup and shutdo"ll. The major parts of the 3-FPC are three motor-driven regulators, one total pressure level sensor, t .. o differential pressure sensors and three feedback position indicators. A photograph of the pressure controller is shown in F~gure 11. 3 The controller .. eighs 3.65 kg (8.0 Ib) and has a volume of 1.58 cm (96.3 in ). The controller has five fluid interfaces: H2 and 02 inlets, H2 and 02 outlets and a pressure reference to the water feed tank. lUI other fluid incerconnec­tions a!:e manifolded internally and sealed .. ith O-rings. The electr.ical interface is made l<ith a standard connector. Sensor signals are sent to, and actuator signals are received from, the subsystem instrumentation. With these features, the pressure controller is ideally suited for closed-loop control using microprocess0r~ 0[' minicomputer-based instrumentation.

The ancillary components of the OGS consisted of solenoid valves, a heat exchanger, a coolant pump and bladder- type tanks and accumulators. No unique design was needed.

Water Handling Subsystem

Within air revitalization subsystems liquid water: is generated and consumed at various locations. The OGS is the prinCipal consumer of water. It requires certain components to provide an automatic supply of water for ~lectrolysis. For the ARX-1, these components have been grouped and treated as the WHS.

Schematic and Operation

The function of the WHS is to enSUre that a supply of .. ater exist.s for the OGS .. a·te.r feed tank. A schematic of the WHS is shown in Figure 12. The principal component in the WHS is a pressure referenced .. a'ter storage tank .. hich at pre­scribed intervals fills the OGS I'ater feed tank. The water comes from one of two sources: one internal, the other external to the ARX-1. The internal water source combines the water collected from the S-CRS condenser/separator and that from the CHCS. These two sources normally supply all the water Fequired by the OGS. If, however, the internal .. ater collection is diminished below OGS requirements, additional or makeup water can be supplied from an external sOUrce. Conversely, if the internal supplies exceed OGS demand, the excess water can be dumped to external storage through a backpressure regulator.

The internal .. ater supplies normally exceed the OGS .. ater demand as is shown in Table 5 .. hich summarizes the WHS d'dracteristics. Whether the supply .. ater comes from internal Or extern"l supplies, it first passes through a filter, then a deiodinator/deionizer before entering the supply tank. Filling is automatic whenever the pump is on until the water pressure exceeds the dump backpressure (303 kPa (44 psia)). Then the .. ater is automatically dumped. The N2 pressure reference (~00 ~Pa (~9 ~sia)) ass~sts i~ transferring. water to the OGS water feed tank dur~ng ~ts fJ.ll~ng operatJ.on whJ.ch occurs dunng startup and every 12 hours thereafter.

24

£i/f SlIstcHls, IHC.

The 3-FPC .. as developed to meet the unique fluidic and pressure control require­ments of the OGS. It combined, in a single assembly, the sensors and actuators necessary to control and monitor fluid pressure levels and differentials during all operating modes including steady-state, startup and shutdo"ll. The major parts of the 3-FPC are three motor-driven regulators, one total pressure level sensor, t .. o differential pressure sensors and three feedback position indicators. A photograph of the pressure controller is shown in F~gure 11. 3 The controller .. eighs 3.65 kg (8.0 Ib) and has a volume of 1.58 cm (96.3 in ). The controller has five fluid interfaces: H2 and 02 inlets, H2 and 02 outlets and a pressure reference to the water feed tank. lUI other fluid incerconnec­tions a!:e manifolded internally and sealed .. ith O-rings. The electr.ical interface is made l<ith a standard connector. Sensor signals are sent to, and actuator signals are received from, the subsystem instrumentation. With these features, the pressure controller is ideally suited for closed-loop control using microprocess0r~ 0[' minicomputer-based instrumentation.

The ancillary components of the OGS consisted of solenoid valves, a heat exchanger, a coolant pump and bladder- type tanks and accumulators. No unique design was needed.

Water Handling Subsystem

Within air revitalization subsystems liquid water: is generated and consumed at various locations. The OGS is the prinCipal consumer of water. It requires certain components to provide an automatic supply of water for ~lectrolysis. For the ARX-1, these components have been grouped and treated as the WHS.

Schematic and Operation

The function of the WHS is to enSUre that a supply of .. ater exist.s for the OGS .. a·te.r feed tank. A schematic of the WHS is shown in Figure 12. The principal component in the WHS is a pressure referenced .. a'ter storage tank .. hich at pre­scribed intervals fills the OGS I'ater feed tank. The water comes from one of two sources: one internal, the other external to the ARX-1. The internal water source combines the water collected from the S-CRS condenser/separator and that from the CHCS. These two sources normally supply all the water Fequired by the OGS. If, however, the internal .. ater collection is diminished below OGS requirements, additional or makeup water can be supplied from an external sOUrce. Conversely, if the internal supplies exceed OGS demand, the excess water can be dumped to external storage through a backpressure regulator.

The internal .. ater supplies normally exceed the OGS .. ater demand as is shown in Table 5 .. hich summarizes the WHS d'dracteristics. Whether the supply .. ater comes from internal Or extern"l supplies, it first passes through a filter, then a deiodinator/deionizer before entering the supply tank. Filling is automatic whenever the pump is on until the water pressure exceeds the dump backpressure (303 kPa (44 psia)). Then the .. ater is automatically dumped. The N2 pressure reference (~00 ~Pa (~9 ~sia)) ass~sts i~ transferring. water to the OGS water feed tank dur~ng ~ts fJ.ll~ng operatJ.on whJ.ch occurs dunng startup and every 12 hours thereafter.

24

Regul ator Drive ~ lotors

FIGURE 11 THREE-FLUID PRESSURE CONTROLLER

25

Cife S,Is/eMs. JII~.

Fl cc tri c:l 1 COI1l10ctor

Pres sur e TT';\ J1Sduccr

Fluid Port s

Regulator Drive ~lotors

FIGURE 11 THREE-FLUID PRESSURE CONTROLLER

25

Cife S,Is/eMS. JII~.

f-lcct.-ic:!l Connccrol'

Pr es su re TT'ansdurcl'

rIuid Port 5

N

'"

1:-

External . _._-- - -HO ----.

,.i.,y _+_- _R-- ,"'''' ~ ---- i" ,""''''' ~---t- ' ,,~ ... ··eiodinator/ Deionizer

_.-_ R-- _ ---. To OGS Water T --v--- Feed Tank

I

In:~~nal -._ R-- _ -tr. . . -- r J Supply ~. -~-

(S-CRS & CHCS) .

N2 Pressure -11._-------------1 Reference

t,.p:

FIGURE 12 WATER Hil:N»LING SU'BSYSTlm SCHEMATIC

H2

0 Supply Tank

h 'S\ " ~ ~ ~ ! •

~ ~ t:

------------_ . .I\A -~ TO@Exsternal ~ HZ' ,torage

. Filter ExternalR-- I

HZ@ -.---~-~-~-Supply I

I

In'.ter.nal, R.'---- -tr... . -- r J HZO .... -~- -~-

Supply , (S-CRS & CHCS)

'eiodinator/ Deionizer

_.-_ R-- _ ---. To 0GS Water T ~ Feed Tank

N2 Pressure -I ..... ___________ -{')<}..L.L.. __________ .....

Reference

FIGURE 12 WATER Hil:N»LING SU'BSYSTlm SCHEMATIC

..

Cife Svstellls. Inc.

TABLE 5 WATER HANDLING SUBSYSTEM CHARACTERISTICS

Nominal Water Flow Rates, kg/d (Ibid)

Fr0m S-CRS From CHCS To OGS To External Storage

Water Supply Tank

Capacity, I (in3) Reference Pressu,re, kPa (psia) Emptying Cycle, h Filling Cycle

From internal From external

External Supply Pressure, kPa (psia)

Dump Pressure to External Storage, kPa (psia)

27

0.41 (0.91) 1.80 (3.96) 1. 75 (3.86) 0.46 (1.01)

2.46 (150) 200 (29) 12

When Pump is On On Demand

240 (35)

303 (44)

Cife Svstellls. Inc.

TABLE 5 WATER HANDLING SUBSYSTEM CHARACTERISTICS

Nominal Water Flow Rates, kg/d (Ibid)

Fr0m S-CRS From CHCS To OGS To External Storage

Water Supply Tank

Capacity, I (in3) Reference Pressu,re, kPa (psia) Emptying Cycle, h Filling Cycle

From internal From external

External Supply Pressure, kPa (psia)

Dump Pressure to External Storage, kPa (psia)

27

0.41 (0.91) 1.80 (3.96) 1. 75 (3.86) 0.46 (1.01)

2.46 (150) 200 (29) 12

When Pump is On On Demand

240 (35)

303 (44)

Cite Sus/ellis. Jllf.

Hardware Descriptign

The hardware components of the WHS consist of valves, a pump, a deiodinator/ deionizer and a water supply tank. The valves and pump are standard off-the­shelf components. The deiodinator/deionizer, shown in Figure 13, was developed under this program. The 2.4 kg (5.3 lb) unit contains both a charcoal and an ion-exchange resin bed for removing iodine ions and dissolved CO2 from the feed water of the OGS. The charcoal bed also serves as the filter designated in Figure 12.

The water supply tank is shown in Figure 14. The tank, consisting of two stainless steel halves separated by a fljxible diaphragm, has a dry weight of 3.7 kg (8.2 Ib) and holds 2.46 1 (150 in ) of water.

Control and Monitor Instrumentatian

The CIM I provides for automatic control and monitoring of the ARX-1 operation. Through a combination of minicomputer, analog circuitry hardware and assembly language software, all functions of mode and mode transition control, automatic shutdown, monitoring of system parameters and TSA interfacing were provided. The following describes details of the C/M I design and operatian with emphasis on the portions which relate to the OGS.

Power Sharing C~>ncept

The electrical power which the EDC module (EDCM) generates has historically been converted to heat and removed from the SUbsystem as a waste product. Life Systems, Inc. developed a concept for using the EflCM power directly by supplying this power to the OGhyhi2) the two are opera,ted as part of an inte-grated system as in the ARX-1. ,. Using this technique, the EDCM power can be directly subtracted from the power required to operate the SFWEM in the OGS. The remaining power required to operate the SFWEM is then obtained from the input power as shown in Figure 1li. The power controller contains the circuits needed ta automa'tically allow the utilizatian of EflCM power and ta convert the input power to the vol ta.ge and cu·rrent levels required by the SFWEM. All of the EDCM-genera,ted peower is utilized. It is not necessary to send it through a power canversion circuit before it is supplied to the SFWE~L Fo,r the ARX-1, appraximately 10% of the SFWEM power was supplied by the EDCM.

Operating Modes and Mode Tl'ansitions

The elM I pravides fa·r five operating modes: (1) Shutdawn, (2) Normal, (3) Purge, (4) Standby and (5) l!lnpawered. These aperating modes and the allawable mode transitions are shown in Figure 16. In the Norrnal Mode the system gen­erates O2 , removes and reduces CO 2 , controls cabin humidity and distributes ar stores water, as required. In the Shutdown Made these functions are inopera­tive but the system is puwered and all sensors are working. fluring Purge, all H -carrying lines throughout the system are being purged with N. In the Standby Mode the system is pawered and maintained at operating temperatures and pressures; however, actual canversion processes are not taking place.

28

Cite Sus/ellis. Jllf.

Hardware Descriptign

The hardware components of the WHS consist of valves, a pump, a deiodinator/ deionizer and a water supply tank. The valves and pump are standard off-the­shelf components. The deiodinator/deionizer, shown in Figure 13, was developed under this program. The 2.4 kg (5.3 lb) unit contains both a charcoal and an ion-exchange resin bed for removing iodine ions and dissolved CO2 from the feed water of the OGS. The charcoal bed also serves as the filter designated in Figure 12.

The water supply tank is shown in Figure 14. The tank, consisting of two stainless steel halves separated by a fl3xible diaphragm, has a dry weight of 3.7 kg (8.2 Ib) and holds 2.46 1 (150 in ) of water.

Control and Monitor Instrumentatian

The CIM I provides for automatic control and monitoring of the ARX-1 operation. Through a combination of minicomputer, analog circuitry hardware and assembly language software, all functions of mode and mode transition control, automatic shutdown, monitoring of system parameters and TSA interfacing were provided. The following describes details of the C/M I design and operatian with emphasis on the portions which relate to the OGS.

Power Sharing C~>ncept

The electrical power which the EDC module (EDCM) generates has historically been converted to heat and removed from the SUbsystem as a waste product. Life Systems, Inc. developed a concept far using the EflCM power directly by supplying this power to the OGhyhi2) the two are opera,ted as part of an inte-grated system as in the ARX-1. ,. Using this technique, the EDCM power can be directly subtracted from the power required to operate the SFWEM in the OGS. The remaining power required to operate the SFWEM is then obtained from the input power as shown in Figure 1li. The power controller contains the circuits needed ta automa'tically allow the utilizatian of EflCM power and ta convert the input power to the vol ta.ge and cu·rrent levels required by the SFWEM. All of the EDCM-genera,ted peower is utilized. It is not necessary to send it through a power canversion circuit before it is supplied to the SFWE~L Fo,r the ARX-1, appraximately 10% of the SFWEM power was supplied by the EDCM.

Operating Modes and Mode Tl'ansitions

The elM I pravides fa·r five operating modes: (1) Shutdawn, (2) Normal, (3) Purge, (4) Standby and (5) l!lnpawered. These aperating modes and the allawable mode transitions are shown in Figure 16. In the Norrnal Mode the system gen­erates O2 , removes and reduces CO 2 , controls cabin humidity and distributes ar stores water, as required. In the Shutdown Made these functions are inopera­tive but the system is puwered and all sensors are working. fluring Purge, all H -carrying lines throughout the system are being purged with N. In the Standby Mode the system is pawered and maintained at operating temperatures and pressures; however, actual canversion processes are not taking place.

28

'" ""

10.5 em (4.1 in)

J/ P4" ~~,f{ ~

23.6 em (9.3 in)

Mounting Feet

FIGURE 13 DEIODINATOR/DEIONIZER

Water Outlet

Water Inlet

h ~ ~ ~ I !IIi

~ :'"

'" '"

10.5 em (4.1 in)

/1 ~4'" ~~,f{ ~

23.6 em (9.3 in)

Mounting Feet

FIGURE 13 DEIODINATOR/DEIONIZER

Water Outlet

Water Inlet

h ~ ~ ~ I ~

~ l"

.., o

Pressure Reference

(6.5 in) I' "., =

1 · " 14.0 em (5.5 in)

I

Disassembled

FIGURE 14 WATER SUPPLY TANK

Assembled

Flexible Disphrasm

h ~ ~ tl I ~

ir ~

.., o

Pressure Reference I_ 16 . 5 em

• (6.5 in)

~_...J ~ . ,

t ~ 14.0 em (5.5 in)

I

Disassembled

FIGURE 14 WATER SUPPLY TANK

Assembled

Flexible Diaphr ...

h ~ ~ tl i ~

ir ~

•

Input Power

,ci/e SIIBleIllB, IHC.

EDCM Power EDCM

Power Total SFWEM SFWEM Controller Power

FIGURE is POWER CONTROLLER BLOCK DiIAGRAM

31

•

Input Power

,ci/e SIIBleIllB, IHC.

EDCM Power EDCM

Power Total SFWEM SFWEM Controller Power

FIGURE is POWER CONTROLLER BLOCK DiIAGRAM

31

.., ..., ,

,

A 8 C E Normal

~ ~ ! ! (A)

From All Modes

Power On Reset

I:JnpoweFed Shutdewn eJ]) (8)

fuFge eC)

HGl!f~E 16 OPERATING MOJ]ES AND ALLOWABLE ~IOJ]E TRANSITIONS

Standby eE)

'" 5 IV

• 4 a • 8 r

A 1

• 12 Transitions

h ~ I!\

~ .~ ~ I •

~ l'"

A 8 C E Normal

~ ~ ! ! (A)

From All Modes

,

Power On Reset

I:JnpoweFed Shutdewn Standby eJ]) (8) eE)

,

'" 5 Modes • 4 o.pemting ~lodes

fuFge • 8 Programmable, A11o~led Mode eC) Transitions

• 12 Allowable Mode . . Trans1t10ns

HGl!f~E 16 OPERATING MOJ]ES AND ALLOWABLE ~IOJ]E TRANSITIONS

Ci/e Sf/slellls. Inc.

Finally, in the Unpowered Mode, no electrical power is applied to the system and there are no fluid flows. Further details of the mode definitions are presented in Appendix 2.

System Control an<! Monit()ring

There are 16 controls needed to operate the ARX-l. These include controls for EDCM temperature and current, S-CRS temperature, CHCS temperature, water accumulator fill and/or empty, OGS temperature, pressure and current, and N2 Generation Module (NGM) pressure and temperature. The controls for the OGE and WHS are highlighted in Table 6.

Sensors are required to interface with the C/M I to provide for control and monitoring of subsystem parameters and performance. Over 100 sensors are implemented in the ARX-l. These monitor flows, pressures, temperatures, currents, voltages, liquid levels, combustible gas presence and valve positions. Fifty-five monitors, identified in Table 7, are specifically associated with the OGS and WHS. In addition, Table 8 identifies subsystem parameter condi­tions which will call for an automa,tic, controlled shutdown of the ARX-l. The shutdown conditions can be easily modified by the operator through an operator/ system interface.

Operator/System Interface

Figure 17 shows the opera,tor/system interface panel of the C/M I through which the operator can communicate with the system. The panel is subdivided into three major areas: System Status, Operator Commands and System Control.

The overall system status is provided in the upper left-hand portion of the panel. The sta,tus summary is given as Normal, Caution, Warning or Alarm and is determined by the worst case condition fo,r any critical parameter. A reset button is provided to clear the status summary and reset the subsystem monitor­ing functions. Messages and info"ma,tion concerning the system are displayed on a Cathode-Ray Tube (CRT) located below the status summary indicators. In addition, the CRT displays fault diagnostiC messages, present status and values of selected sensors, input/ol:tput data, elapsed times and communications between the system and an operator.

The operator commands section in the lower left-hand corner p"ovides the capability of the operator to communicate with the system. Capability exists for entering data, examining current. values, upda,ting scale factors, modifying setpoints or allowable ranges and control of the CRT display.

Manual initiation of the four operating modes (No'rmal, Shutdown, Purge and Standby) is provided in the upper right-hand corner of the panel. The controls

'" automatica.lly prevent the operator from initiating an illegal mode transition (e. g., No,rmal to Purge). The subsystem will not respond to an illegal mode transition command. Accidental mode initiation is prevented by providing a mode change permit button which must be simultaneously depEessed with the de~i,red mode button.

33

Ci/e Sf/slellls. Inc.

Finally, in the Unpowered Mode, no electrical power is applied to the system and there are no fluid flows. Further details of the mode definitions are presented in Appendix 2.

System Control an<! Monit()ring

There are 16 controls needed to operate the ARX-l. These include controls for EDCM temperature and current, S-CRS temperature, CHCS temperature, water accumulator fill and/or empty, OGS temperature, pressure and current, and N2 Generation Module (NGM) pressure and temperature. The controls for the OGE and WHS are highlighted in Table 6.

Sensors are required to interface with the C/M I to provide for control and monitoring of subsystem parameters and performance. Over 100 sensors are implemented in the ARX-l. These monitor flows, pressures, temperatures, currents, voltages, liquid levels, combustible gas presence and valve positions. Fifty-five monitors, identified in Table 7, are specifically associated with the OGS and WHS. In addition, Table 8 identifies subsystem parameter condi­tions which will call for an automa,tic, controlled shutdown of the ARX-l. The shutdown conditions can be easily modified by the operator through an operator/ system interface.

Operator/System Interface

Figure 17 shows the opera,tor/system interface panel of the C/M I through which the operator can communicate with the system. The panel is subdivided into three major areas: System Status, Operator Commands and System Control.

The overall system status is provided in the upper left-hand portion of the panel. The sta,tus summary is given as Normal, Caution, Warning or Alarm and is determined by the worst case condition fo,r any critical parameter. A reset button is provided to clear the status summary and reset the subsystem monitor­ing functions. Messages and info"ma,tion concerning the system are displayed on a Cathode-Ray Tube (CRT) located below the status summary indicators. In addition, the CRT displays fault diagnostiC messages, present status and values of selected sensors, input/ol:tput data, elapsed times and communications between the system and an operator.

The operator commands section in the lower left-hand corner p"ovides the capability of the operator to communicate with the system. Capability exists for entering data, examining current. values, upda,ting scale factors, modifying setpoints or allowable ranges and control of the CRT display.

Manual initiation of the four operating modes (No'rmal, Shutdown, Purge and Standby) is provided in the upper right-hand corner of the panel. The controls

'" automatica.lly prevent the operator from initiating an illegal mode transition (e. g., No,rmal to Purge). The subsystem will not respond to an illegal mode transition command. Accidental mode initiation is prevented by providing a mode change permit button which must be simultaneously depEessed with the de~i,red mode button.

33

Cite Sus/ellis. INf.

Parameter Controlled

SFWEM Temperature

SFWEM Pressure

SFWEM Current

Dehumd.difier Module (DM) Current

DM Voltage

Water Feed Tank Fill

Water Storage Tank Fill

TABLE 6 OGS AND WHS CONTROLS DEFIlHTION

Control Description

Regulates liquid coolant flow through bypass heat exchanger to maintain desired coolant temperature

Controls OGS system pressure to setpoint, H pressure a,t desired /J;P above setpoint and 02 pressu,re at desired /J;P above H2 pressure

Controls current flow to SFWEM cells to regulate production of O2 and H2

Maintains DM current at desired setpoint level

Sets a specified voltage for software control. Interfaces with IilM Current Control

Fills SFWEM Feed Tank eve'ry 12 hours or when Feed Tank /J;P is grea,ter than fixed level

Maintains Storage Tank filled. Fills tank when tank /J;P is greater than fixed level

34

Controlled Actuator

Coolant Diverter Valve

Three-Fluid Pressure Controller

Power Supply/ Power Sharing Circuitry

Power Supply/ Conditioning

Power Supply/ Conditioning

Miscellaneous Valves/Sequences

External Water Source Isolation Valve

Cite Sus/ellis. INf.

Parameter Controlled

SFWEM Temperature

SFWEM Pressure

SFWEM Current

Dehumd.difier Module (DM) Current

DM Voltage

Water Feed Tank Fill

Water Storage Tank Fill

TABLE 6 OGS AND WHS CONTROLS DEFIlHTION

Control Description

Regulates liquid coolant flow through bypass heat exchanger to maintain desired coolant temperature

Controls OGS system pressure to setpoint, H pressure a,t desired /J;P above setpoint and 02 pressu,re at desired /J;P above H2 pressure

Controls current flow to SFWEM cells to regulate production of O2 and H2

Maintains DM current at desired setpoint level

Sets a specified voltage for software control. Interfaces with IilM Current Control

Fills SFWEM Feed Tank eve'ry 12 hours or when Feed Tank /J;P is grea,ter than fixed level

Maintains Storage Tank filled. Fills tank when tank /J;P is greater than fixed level

34

Controlled Actuator

Coolant Diverter Valve

Three-Fluid Pressure Controller

Power Supply/ Power Sharing Circuitry

Power Supply/ Conditioning

Power Supply/ Conditioning

Miscellaneous Valves/Sequences

External Water Source Isolation Valve

Sensor Location

Oxygen Generation Subsystem

Water Handling Subsystem

TABLE 7 SENSOR LIST

Parameter M0nitored

SFWEM Temperature BM Temperature Feed Wa,ter Inlet Pressu·re SFWEM Cnrrent SFWEM Cell Voltage IlM Current DM Cell Voltage H2 , 02 Outlet Pressure System Regulato.r Pressure H2 , 02 M' N2 Purge Supply Pressure Combustible Gas Contamination in 02 Valve Position Indicators

Accumulato.r Pressure Pump Outlet Pressu·re I!leionizer f.P SFWEM Feed Water Tank t.P Water Supply Tank f.P Feed Water Conductivity Aceumulator Level Valve Position Indicato·r

3S

ei/e Sf/sIems, lH(.

No. Sensors

2 2 1 1 12 1 3 2 1 2 1 3 11

1 1 1 1 1 1 2 5

Sensor Location

Oxygen Generation Subsystem

Water Handling Subsystem

TABLE 7 SENSOR LIST

Parameter M0nitored

SFWEM Temperature BM Temperature Feed Wa,ter Inlet Pressu·re SFWEM Cnrrent SFWEM Cell Voltage IlM Current DM Cell Voltage H2 , 02 Outlet Pressure System Regulato.r Pressure H2 , 02 M' N2 Purge Supply Pressure Combustible Gas Contamination in 02 Valve Position Indicators

Accumulato.r Pressure Pump Outlet Pressu·re I!leionizer f.P SFWEM Feed Water Tank t.P Water Supply Tank f.P Feed Water Conductivity Aceumulator Level Valve Position Indicato·r

3S

ei/e Sf/sIems, lH(.

No. Sensors

2 2 1 1 12 1 3 2 1 2 1 3 11

1 1 1 1 1 1 2 5

ei/e Slit/elliS. JH~.

TABLE 8 PARAMETERS MONITORED FOR AUTOMATIC SHUTDOWN

Parameter

Low Cell Voltage, V High Cell Voltage, V Low Current, A High Current, A High Temperature, K (F) Low Feed Water Filter AP, kPa (psid) High Feed Water Filter AP, kPa (psid) Low Feed Water Tank AP, kPa (psid) High Feed Water Tank AP, kPa (psid) Low System Pressure, kPa (psia) High System Pressure, kPa (psia) Low N2 Supply Pressure, kPa (psia) High NZ Supply Pressure, kPa (psia) Low H -to-Water AP, kPa (psid) High ft2-to-water AP, kPa (psid) Low Oz-to-Water AP, kPa (psid) High 0 -to-Water AP, kPa (psid) Low Water Supply Tank AP, kPa (psid) High Water Supply Tank AP, kPa (psid)

36

Shutdown Condition

1.45 1.90 15.0 30.0 356 (180) -21 (-3.0) 21 (3.0) -14 (-2.1) 14 (2.1) 760 (HO) 1170 (170) 790 (115) 1070 (!.\is) -21 (-3) 69 (0) -6.9 (-1) 69 (10) 41 (-6) 14 (2)

ei/e Slit/elliS. JH~.

TABLE 8 PARAMETERS MONITORED FOR AUTOMATIC SHUTDOWN

Parameter

Low Cell Voltage, V High Cell Voltage, V Low Current, A High Current, A High Temperature, K (F) Low Feed Water Filter AP, kPa (psid) High Feed Water Filter AP, kPa (psid) Low Feed Water Tank AP, kPa (psid) High Feed Water Tank AP, kPa (psid) Low System Pressure, kPa (psia) High System Pressure, kPa (psia) Low N2 Supply Pressure, kPa (psia) High NZ Supply Pressure, kPa (psia) Low H -to-Water AP, kPa (psid) High ft2-to-water AP, kPa (psid) Low Oz-to-Water AP, kPa (psid) High 0 -to-Water AP, kPa (psid) Low Water Supply Tank AP, kPa (psid) High Water Supply Tank AP, kPa (psid)

36

Shutdown Condition

1.45 1.90 15.0 30.0 356 (180) -21 (-3.0) 21 (3.0) -14 (-2.1) 14 (2.1) 760 (HO) 1170 (170) 790 (115) 1070 (!.\is) -21 (-3) 69 (0) -6.9 (-1) 69 (10) 41 (-6) 14 (2)

-c'

,

EJJ

" - '-'~ .,.-.- .-.-

Ci/e Svs/ems, Int.

AIR REVITALIZATION SYST£M \ SYSTEM CONTRCl -----___ SYSTEM ST MUS

Gll (

STATuS !:"~lilR'I' I

B EJJ GJ L_ '._.:;...._

O"ERATOR/S'SYEM MESSAG£S

;

'" ERATiNG MCC£/CQW:'NOS _____ ~

II~I IICqW~l

I .. uto ..... ;~

PIlOnCloOOJ 0"

@

!

~-

_ CCNT'lOl 5TAl\JS

AG,:,unI)A. (N(:RII101(

"" @ ©

CP:::'RATOR COMIIIlAI\I~S 'I

r Q-"-'''f'. ]-'"-"~-~ .. ~ " , I ~"'" r'~ ! .... ;~ ~ "I I 10

1 _IN I ~~l\Jt • "';lt~;'(!'oO.l"-of. "'~_l..:.r I 7 8 - I ~c:o,n . - --1 -. C;;;C ~ '''''''" '"""C", '""' ! .. ~, .4 5 6 I cu:.u~ ~npi:l.11I

I q~lt "V'T~ l.t~[l I 2 - I ~~ ='~I "~,, I ' I ;

0.. -\11011: I-~~~ I"""" '"""1 '-- I -I 1>':1', ~T 1tO.1I(",( !.... "o(,,~.')! fUJER - i 0 I •

''€i' '1(_" .ur;, ",::un C'Mt~ ~IU""J L.~P :j~\t'~ku'l ~i I""" ta:!>Pl&Y ~[III:It-t ,~h<;""" mil" '[!of I t"l'RT SlIClCR until

J I ' , I

§ §

~ '....- --€)- .

,.-----

~

§

FIGURE 17 ONE-PERSON AIR REVITALIZATION SYSTEM 0PERA1!OR/SYSTEM INTERFACE PANEL

37

-c·

,

f€l

€l

~ '... ..

" - '-'~ .,.-.- .-.-

Ci/e Svs/ems, Int.

AIR REVITALIZATION SYST£M \ SYSTEM CONTRCl-----"'\ SYSTEM ST MUS

Gll STATuS !:"~lilR'I'

EJJ B EJJ GJ L_ '._.:;...._

O"ERATOR/S'SYEM MESSAG£S

CP:::'RATOR COMIIIlAI\I~S \

"-'''ili~'-]-'<~~~-~ .. ~ " , I ~"'" r ,~ ! .... ;t ~ III I I 0 I _IN I ~~l\Jt • "';lt~;'(!'oO.l"-of. "'~_l..:.r I 7 8 - I ~c:o,n

• _ __. _. C;;;C ~ rloC:'CIl CU~CI'n, "~H ! UIJIIl ~ 4 5 6 I

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FIGURE 17 ONE-PERSON AIR REVITALIZATION SYSTEM 0PERA1!OR/SYSTEM INTERFACE PANEL

37

Ci/e Sus/eHis. INt.

The control status is located directly below the operating mode/commands section. Two lights are p.rovided to indicate whether one of the automatic protection overrides or an actuator override has been activated. A light is also prOVided to indicate when the panel switches have been disabled, a condi­th,n used to prevent unauthorized personnel to activate any button.

Hanual controls, designed primarily for use during system debug or off-design operation, are provided behind an access panel located immediately below the operato,r commands and system control sections. Overrides are provided fer all actuato.rs in the form of toggle switches. The actuator overrides must be placed in an automatic position for the system to opera.te normally. Also, manual adjustments are provided for adjusting certain setpoints such as SFWEM current. The access panel is normally closed to prevent accidental actua,tions.

Software

The ARX-l software is erganized into 70 different software packages or modules. They are divided into system definition and data base, frent panel service, real-time executive, input/output, centrol/menitor, operating mode control and intermode transition functions. Of the total, the OG8 and WHS require 15 of the modules exclusively and share the majority of the remainder.

TEST SUPPORT ACCESSORIES

Test Support Accessories were develo.ped to suppo'rt the test program of the ARX-l. The laboratory breadboard module test stand developed under a previous pregram (Contract NAS2-7470) was used for the SFWEM endu·rance testing.

One-Person Air Revitalization System

A block diagram of the ARS TSA is shown in Figure 18. Some of the TSA hardware Was developed or refurbished as part of this program; some was prOVided from prior programs and modified. This hardware included part or all of the Fluid Supply Unit, the Air Supply Unit and its control, the Coolant Supply Unit, a N2H4 Refill ~acility,. the Vent/Vacuum Source, the m~ta Acquisition Unit and . tile Parametn.c Data lhsplay. Test Support Accessor~es that were needed spec~­fically for the OGS testing included theN purge supply and a water SOurce with liqUid level monitoring. Also, raw De power was supplied to the CIM I which further conditioned the power to operate the OGS and, in conjunction with the power-sharing concept, the EDC.

A major portion of the TSA activities was involved with the development of the parametric data display unit. The unit, packaged in a separate cabinet, is shown in Figure 19. It services all of the functions of the ARX-l. Specifi­cally, it contains displays for temperatures, cell voltages and currents, flows and pressures. Also shown in the lower portien of the cabine't are power supplies reqUired for operation of the parametric data display unit and the ARX-l.

38

Ci/e Sus/eHis. INt.

The control status is located directly below the operating mode/commands section. Two lights are p.rovided to indicate whether one of the automatic protection overrides or an actuator override has been activated. A light is also prOVided to indicate when the panel switches have been disabled, a condi­th,n used to prevent unauthorized personnel to activate any button.

Hanual controls, designed primarily for use during system debug or off-design operation, are provided behind an access panel located immediately below the operato,r commands and system control sections. Overrides are provided fer all actuato.rs in the form of toggle switches. The actuator overrides must be placed in an automatic position for the system to opera.te normally. Also, manual adjustments are provided for adjusting certain setpoints such as SFWEM current. The access panel is normally closed to prevent accidental actua,tions.

Software

The ARX-l software is erganized into 70 different software packages or modules. They are divided into system definition and data base, frent panel service, real-time executive, input/output, centrol/menitor, operating mode control and intermode transition functions. Of the total, the OG8 and WHS require 15 of the modules exclusively and share the majority of the remainder.

TEST SUPPORT ACCESSORIES

Test Support Accessories were develo.ped to suppo'rt the test program of the ARX-l. The laboratory breadboard module test stand developed under a previous pregram (Contract NAS2-7470) was used for the SFWEM endu·rance testing.

One-Person Air Revitalization System

A block diagram of the ARS TSA is shown in Figure 18. Some of the TSA hardware Was developed or refurbished as part of this program; some was prOVided from prior programs and modified. This hardware included part or all of the Fluid Supply Unit, the Air Supply Unit and its control, the Coolant Supply Unit, a N2H4 Refill ~acility,. the Vent/Vacuum Source, the m~ta Acquisition Unit and . tile Parametn.c Data lhsplay. Test Support Accessor~es that were needed spec~­fically for the OGS testing included theN purge supply and a water SOurce with liqUid level monitoring. Also, raw De power was supplied to the CIM I which further conditioned the power to operate the OGS and, in conjunction with the power-sharing concept, the EDC.

A major portion of the TSA activities was involved with the development of the parametric data display unit. The unit, packaged in a separate cabinet, is shown in Figure 19. It services all of the functions of the ARX-l. Specifi­cally, it contains displays for temperatures, cell voltages and currents, flows and pressures. Also shown in the lower portien of the cabine't are power supplies reqUired for operation of the parametric data display unit and the ARX-l.

38

.., '"

Lab Gas

Sapplies

ARX-l

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Refill

High N 2 Press.

Sapply

Coolant Sapply I!Jnit

Water Sot1rce

I • r , I " ~ ____ J I

·1 I : " , _____ J "rent/ ____ . ____,.- \acawn I I 1-- -,-:'--l S0urce

I ' i ARX-l I F1aid

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--'''~f., ~ ,."Yy , .. ,,,M'" Ai,

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I I L ___ I___ _ ___ ." ____ J

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I:1nit I

, Parametric

Data Display

,Data Acqt1isitioo

l!Joit

FlmJRE 18 0NE-PERSON AIR REVITAUZAT]QN SYSTEM TSA Bl!.OCK DIAGRAM

h ~ .~

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~ ~

I

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Sapplies

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i , : 1 " :1 ,;-c. --__ --__ J j ,rent/

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FlmJRE 18 0NE-PERSON AIR REVITAUZATWN SYSTEM TSA BMDCK DIAGRAM

Ci/e S,IlfeMI. Jilt.

, .. J $

• • •

-.. -

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•• • • • •

Temperatures

Cell Voltages and Cur ren t s

Pr essures

Flows

Power Supplies

FIGURE 19 ONE-PERSON AIR REVITALIZATION SYSTEM PARAMETRIC DATA DISPLAY CABINET

40

Ci/e S,IlfeMI. Jilt.

f .. J --. -

• • • DO ·

•• • • •

~- Temperatures

Cell Voltages and Currents

Pressures

Flows

Power Supplies

FIGURE 19 ONE-PERSON AIR REVITALIZATION SYSTEM PARAMETRIC DATA DISPLAY CABINET

40

Cite S,Is/ellls, Inc.

Laboratory Breadboard Module Test Stand

Two 12-cell electrolysis modules were tested in the laboratory breadboard test stand shown in Ft~U45 20. Detailed descriptions of the test stand can be found elsewhere. -,

The primary purpose of the test stand was to allow for bench-top testing of the SFWEM in order to advance the SFWE and module technologies. The basic configuration of the test stand schematic is similar to tha,t of the previously­described OGS. Major differences in the test stand are:

1. Three manual pressure regulators were used instead of the 3-FPC.

2. Automatic operation was limited with only water fill and shu,tdown sequences being automated.

3. Electrolyte can be circulated through feed water compartments to purge liberated gas.

4. Either a DM or condenser/separators can be used for dehumidification of product gases.

The laboratory breadboard test stand was equipped with all needed TSA such as electrical power, process water source, cooling water and N2 purge supply.

PRODUCT ASSURANCE PROGRAM

A mini-Product Assurance Program was established, implemented and maintained throughout all phases of contractual performance including design, purchasing, fabrication and testing.

Quality Assurance

Quality Assurance activities were included during the design studies, interface requirement definitions and during inspection of fabricated and pu,rchased parts. The objective was to search out quality weaknesses and provide appro­priate corrective action. Also, a quality assurance effort was involved in the preparation of the final report with the objective of identifying and resolving deficiencies that could affect the quality of future equipment.

Reliability

Reliability personnel participated in the program to insure (1) p,roper cali­bration of test equipmen,t and TSA instrumentation, (2) adherence to test pro­cedures and (3) proper recording and reporting of test data and observations. A survey of the subsystem and TSA design was performed to determine the cali­bration requirements for testing. Appropriate components were calibrated du,ring assembly and after installation.

41

Cite S,Is/ellls, Inc.

Laboratory Breadboard Module Test Stand

Two 12-cell electrolysis modules were tested in the laboratory breadboard test stand shown in Ft~U45 20. Detailed descriptions of the test stand can be found elsewhere. -,

The primary purpose of the test stand was to allow for bench-top testing of the SFWEM in order to advance the SFWE and module technologies. The basic configuration of the test stand schematic is similar to tha,t of the previously­described OGS. Major differences in the test stand are:

1. Three manual pressure regulators were used instead of the 3-FPC.

2. Automatic operation was limited with only water fill and shu,tdown sequences being automated.

3. Electrolyte can be circulated through feed water compartments to purge liberated gas.

4. Either a DM or condenser/separators can be used for dehumidification of product gases.

The laboratory breadboard test stand was equipped with all needed TSA such as electrical power, process water source, cooling water and N2 purge supply.

PRODUCT ASSURANCE PROGRAM

A mini-Product Assurance Program was established, implemented and maintained throughout all phases of contractual performance including design, purchasing, fabrication and testing.

Quality Assurance

Quality Assurance activities were included during the design studies, interface requirement definitions and during inspection of fabricated and pu,rchased parts. The objective was to search out quality weaknesses and provide appro­priate corrective action. Also, a quality assurance effort was involved in the preparation of the final report with the objective of identifying and resolving deficiencies that could affect the quality of future equipment.

Reliability

Reliability personnel participated in the program to insure (1) p,roper cali­bration of test equipmen,t and TSA instrumentation, (2) adherence to test pro­cedures and (3) proper recording and reporting of test data and observations. A survey of the subsystem and TSA design was performed to determine the cali­bration requirements for testing. Appropriate components were calibrated du,ring assembly and after installation.

41

.,. ...

Oxygen Pressure Re gul a1:or

lIydrogen Pressur e Regulator

System Pressure Regulat.or

• - .... "

0 •••• ,,-

- •••• I " .... - .... - .... - .... - .... - .... - .... - ....

• • =-,

Current Adjus1:ment

Temperature Adjustment

Performance Trend Analysis

Control and Monitor Instrumentation

• _.

Pushbutton

FIGURE 20 LABORATORY BREADBOARD MODULE TEST STAND

I

Manual

~ ~ ~ ~ i !"

~ :'\

. .

Oxygen Pr essure Re gul at or

lIydrogen Pressur e Regulator

System Pressure Regulator

- .... •••••

- .... ••• ••

- .... - .... -- - .... - .... - ....

- .... - ....

• • =-,

Current Adjustment

Temperature Adjustment

I

Performance Trend Analysis

Control and ~Ioni tor Instrumentation

On Pushbutton

FIGURE 20 LABORATORY BREADBOARD MODULE TEST STAND

I Manual

,~~"---~

Cife Sl/llell/l, lHt.

A test procedure was followed to insu're tha,t all critical parameters were properly monitored and that the testing conformed to the program's quality assurance and safety procedures. All major testing required that a test plan be completed and reviewed.

Safety

A safety program was initiated to assure adherence to safety standards and procedures essential to protect personnel and equipment. The program consisted of identifying possible adverse subsystem characteristics, reviewing designs and de.s ign changes for potential safety hazards, reviewing NASA Alerts for safety informa'tion and incorpora,ting the equipment's prote.cti ve features.

Materials Control

A mini-materials control program Was initiated to provide assurance tha,t the OGS design did not preclude the efficient application of a more detailed subsystem materials control program during subsequent developments. As a goal, materials of construction were selected to comply with projected space­craft material specifications.

Configu'ration Control

A mini-configu,ra,tion management program Was established, implemented and main­tained. This program p'rovided for documentation concerning interfa,ce require~ ments for the OGS as applicable for the ARX-1 testing. The p,ro.gram was imple­mented with a primary goal to provide assurance that the efficient applica,tion of a more detailed Gonfiguration management p'rogram could be applied during subsequent developmen.ts of OGS hardware.

PROGRAM TESTING

The overall objectives of the test program were to (1) prove the integration concept of the OGS with the ARS, (2) further advance the OGS technology and (3) demonstra,te the hardware maturity of the OGS components such as electroly­sis cells, modules and the 3-FPC. Testing activities associa,ted with the integrated ARX-1 and the SFWEM are p,resented in this section. Results af other OGS component tests will be presented in the Supporting Technolagy Studies section.

Integrated ARX-l Tes·ting

The ARX-1 testing was conducted for a period of 120 days and included testing at the companent, subsystem, CIM I (hardware and saftware) and total system levels. Specific testing activities which occurred during the checkout, Shakedown and endurance phases are shown in Figu,re 21.

;resting Summary

A total of 480 h (20 d) of successful, integrated AAX-1 opera,tion in the No,rmal Mode was achieved. Normal Mode excludes the time required for the transitions Shutdown to Normal and of No,rmal to Shutdown. These transitions typically requi.re 0.5 h each and primarily involve the presslJ.riza,tion or dep'ressudzation of the OGS.

43

,~~"---~

Cife Sl/llell/l, lHt.

A test procedure was followed to insu're tha,t all critical parameters were properly monitored and that the testing conformed to the program's quality assurance and safety procedures. All major testing required that a test plan be completed and reviewed.

Safety

A safety program was initiated to assure adherence to safety standards and procedures essential to protect personnel and equipment. The program consisted of identifying possible adverse subsystem characteristics, reviewing designs and de.s ign changes for potential safety hazards, reviewing NASA Alerts for safety informa'tion and incorpora,ting the equipment's prote.cti ve features.

Materials Control

A mini-materials control program Was initiated to provide assurance tha,t the OGS design did not preclude the efficient application of a more detailed subsystem materials control program during subsequent developments. As a goal, materials of construction were selected to comply with projected space­craft material specifications.

Configu'ration Control

A mini-configu,ra,tion management program Was established, implemented and main­tained. This program p'rovided for documentation concerning interfa,ce require~ ments for the OGS as applicable for the ARX-1 testing. The p,ro.gram was imple­mented with a primary goal to provide assurance that the efficient applica,tion of a more detailed Gonfiguration management p'rogram could be applied during subsequent developmen.ts of OGS hardware.

PROGRAM TESTING

The overall objectives of the test program were to (1) prove the integration concept of the OGS with the ARS, (2) further advance the OGS technology and (3) demonstra,te the hardware maturity of the OGS components such as electroly­sis cells, modules and the 3-FPC. Testing activities associa,ted with the integrated ARX-1 and the SFWEM are p,resented in this section. Results af other OGS component tests will be presented in the Supporting Technolagy Studies section.

Integrated ARX-l Tes·ting

The ARX-1 testing was conducted for a period of 120 days and included testing at the companent, subsystem, CIM I (hardware and saftware) and total system levels. Specific testing activities which occurred during the checkout, Shakedown and endurance phases are shown in Figu,re 21.

;resting Summary

A total of 480 h (20 d) of successful, integrated AAX-1 opera,tion in the No,rmal Mode was achieved. Normal Mode excludes the time required for the transitions Shutdown to Normal and of No,rmal to Shutdown. These transitions typically requi.re 0.5 h each and primarily involve the presslJ.riza,tion or dep'ressudzation of the OGS.

43

I CHEeKeUT ,I

Sensor Ca·librstion Ilfver·ter Valves e.peration and Control Wster Collec·tion and Supply Loops Hydl'ophobie SCl'een Liquid/Cas Separator I!:HCS Tolerance and Control ecs Three~Fl!uid P·ressure Controller

'""" SHAmOOWN -1 EDCM and SabatierControl SFWEM Pressurization/Depressurization Sequencing Water collection and Supply Routines (at pressul'e) Sta·rtup/Shutdown Sequencing CHCS/EDe/S-CRS./eCS Integration

~ Sup.plementa·ry Shutdown Controller Integration

o 15 3a 45 6a 75

Test Time. Days

FliGlJRE 21 AllX-l TEST OVERVliEW

ENDURANeE

Software Sequencing. Modifications Startup/Shu~down Sequences, Verifica­tion, elM I and ASU Electrically In­terfaced forPower-eff Shutdown/Purg­ing, ecs Cootant Loop Modification ORCS/EDC Humidity Control Test

I 9a la5 120

~ ~ "-.~ ~ I !"i

~ ~

I CHEeKeUT I Sensor Ca·librstion Ilfver·ter Valves e.peration and Control Wster Collec·tion and Supply Loops Hydl'ophobie SCl'een Liquid/Cas Separator I!:HCS Tolerance and Control ecs Three~Fl!uid P·ressure Controller

EDCM and SabatierControl SFWEM Pressurization/Depressurization Sequencing Water collection and Supply Routines (at pressul'e) Sta·rtup/Shutdown Sequencing CHCS/EDe/S-CRS./eCS Integration

~ Sup.plementa·ry Shutdown Controller Integration

o 15 3a 45 6a 75

Test Time. Days

FliGlJRE 21 AllX-l TEST OVERVliEW

ENDURANeE

Software Sequencing. Modifications Startup/Shu~down Sequences, Verifica­tion, elM I and ASU Electrically In­terfaced forPower-eff Shutdown/Purg­ing, ecs Cootant Loop Modification ORCS/EDC Humidity Control Test

I 9a la5 120

- - .,~.~

Cilt S,Isleml. IHt.

Of the total normal operation, two seven-day periods of continuous uninter­rupted operation were achieved.

The overall system performance is shown in Figure 22. The ARX-l generated O2 above the design level eql'ivalent to one person's metabolic consumption plus

an allowance for overboard leakage. Also, the ARX-l removed CO2

at greater than the one-person level. The curve for net water recovered is the algebraic total of the water (1) supplied to the OGS, (2) removed by the CHCS from the simulated cabin atmospheN and (3) removed by the S-CRS condenser/separator from the S-CRS exhaust stream.

In summary, the ARX-( testing demonstrated the following: (1) duplicate sub­system interface components can be eliminated by treating the hardware from a single system viewpoint, (2) TSA and expendable usage can be reduced (e.g., OGS H2 used by EDC) , (3) a single integrated CIM I can simplify the collection and dl.splay of engineering data, (4) single-button startup of several integrated subsystems can be achieved, (5) the syst'!m provides real-life test conditions by determining the effects of changes in the cabin simulator on the system as a whole and (6) development and testing costs we.re minimized. To illustrate the last point, Figu,re 23 shows the total test time accumulated on the major subsystems and components of the ARX-l. Over 10,000 hours of testing have been achieved for some components using the ARX-l as a test bed. Development of the ARX-l as a system permitted parallel testing of key hardware elements.

OGS Performance

While Figure 22 showed the performance of the overall ARX-l system, theOGS performance is given in greater detail in Figure 24. The nominal operating conditions for the OGS over the 480 h test period are given in Table 9. As shown, most parameters remained constant over the ope.rating period. The electrolysis module in the ARX-l OGS was assembled using advanced electrodes (WAB-5). The WAB-5 performance is slightly lower (higher cell Voltage) than that of the super electrodes (WAB-6).

The integra,ted testing experienced several automatic s'hutdowns as listed in Table 10. Most were due to senso,r or e/M I malfunctions. Two (numbers 3 and 7) were directly attributed to the OGS. One was due to the loss of coolant water and the other was a cell ma,trix failu're which occurred during a wa,ter. fill sequence. The cell matrix failure w~s due to out-of-tolerance pressure spikes occurring during startup and shutdown. That coupled witb some p'ressure pertubations which occu,rred du,ring the water fill damaged a tell matrix.

SFWEM Endu·rance Tests

The SFWEM endurance tests inclUded tes,ting with super electrodes (WAB-6) and with advanced electrodes (WAB-5). Both types of electrodes were assembled into two separate 12-cell modul~s and the modules were tested on the labo.ra­tory breadboard test stand (Figure 20) to evaluate their performances and hardware ma,turity.

45

- - .,~.~

Cilt S,Isleml. IHt.

Of the total normal operation, two seven-day periods of continuous uninter­rupted operation were achieved.

The overall system performance is shown in Figure 22. The ARX-l generated O2 above the design level eql'ivalent to one person's metabolic consumption plus

an allowance for overboard leakage. Also, the ARX-l removed CO2

at greater than the one-person level. The curve for net water recovered is the algebraic total of the water (1) supplied to the OGS, (2) removed by the CHCS from the simulated cabin atmospheN and (3) removed by the S-CRS condenser/separator from the S-CRS exhaust stream.

In summary, the ARX-( testing demonstrated the following: (1) duplicate sub­system interface components can be eliminated by treating the hardware from a single system viewpoint, (2) TSA and expendable usage can be reduced (e.g., OGS H2 used by EDC) , (3) a single integrated CIM I can simplify the collection and dl.splay of engineering data, (4) single-button startup of several integrated subsystems can be achieved, (5) the syst'!m provides real-life test conditions by determining the effects of changes in the cabin simulator on the system as a whole and (6) development and testing costs we.re minimized. To illustrate the last point, Figu,re 23 shows the total test time accumulated on the major subsystems and components of the ARX-l. Over 10,000 hours of testing have been achieved for some components using the ARX-l as a test bed. Development of the ARX-l as a system permitted parallel testing of key hardware elements.

OGS Performance

While Figure 22 showed the performance of the overall ARX-l system, theOGS performance is given in greater detail in Figure 24. The nominal operating conditions for the OGS over the 480 h test period are given in Table 9. As shown, most parameters remained constant over the ope.rating period. The electrolysis module in the ARX-l OGS was assembled using advanced electrodes (WAB-5). The WAB-5 performance is slightly lower (higher cell Voltage) than that of the super electrodes (WAB-6).

The integra,ted testing experienced several automatic s'hutdowns as listed in Table 10. Most were due to senso,r or e/M I malfunctions. Two (numbers 3 and 7) were directly attributed to the OGS. One was due to the loss of coolant water and the other was a cell ma,trix failu're which occurred during a wa,ter. fill sequence. The cell matrix failure w~s due to out-of-tolerance pressure spikes occurring during startup and shutdown. That coupled witb some p'ressure pertubations which occu,rred du,ring the water fill damaged a tell matrix.

SFWEM Endu·rance Tests

The SFWEM endurance tests inclUded tes,ting with super electrodes (WAB-6) and with advanced electrodes (WAB-5). Both types of electrodes were assembled into two separate 12-cell modul~s and the modules were tested on the labo.ra­tory breadboard test stand (Figure 20) to evaluate their performances and hardware ma,turity.

45

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FIGURE 23 LIFE TESTING OF ARX-l COMPONENTS/SUBSYSTEMS

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FIGURE 23 LIFE TESTING OF ARX-l COMPONENTS/SUBSYST~~

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TABLE 9 OGS BASELINE (JPERATING CONDITIONS

Number of Cells

Current Density, mA/cm2 (ASE)

Coolant Temperature Control Range, K (E)

Pressure Control Ranges System Pressure, kPa (psia)

H2-to-Eeed Water AP, lcl'a (psid)

02-to-Feed Water AP, kPa (psid)

Startup/Shutdown Pressu·rization and Depressurization Rate, kPa/min (psi/min)

49

Cije Slls/eHls, Inc.

12

196 (182)

336 to 341 (145 to 155)

965 to 1035 (140 to 15(J)

15 to 19 (2.2 to 2.8)

26 to 30 (3.7 to 4.3)

37 (5.4)

i.

TABLE 9 OGS BASELINE (JPERATING CONDITIONS

Number of Cells

Current Density, mA/cm2 (ASE)

Coolant Temperature Control Range, K (E)

Pressure Control Ranges System Pressure, kPa (psia)

H2-to-Eeed Water AP, lcl'a (psid)

02-to-Feed Water AP, kPa (psid)

Startup/Shutdown Pressu·rization and Depressurization Rate, kPa/min (psi/min)

49

,',~ .• _, __ .. "_"_~"':~_"-'_ -"'-0:--;,-, -.' _:

i Cije Slls/eHls, Inc. I

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12

196 (182)

336 to 341 (145 to 155)

965 to 1035 (140 to 15(J)

15 to 19 (2.2 to 2.8)

26 to 30 (3.7 to 4.3)

37 (5.4)

'} ~

Cite Svs/ellls. !Hf.

No.

1

2

3

4

5

6

7

TABLE 10 ARX-l SHUTDOWN SUMMARY

Time. h(a)

28

32

37.5

103.4

270.9

436.4

448.4

Cause

EDCM process air exhaust tempera'ture sensor failu're

Air Supply Bnit electrical noise shutdown

Loss of fluid from SFWEM coolant loop

Supplementary shutdown controller malfunction during SFWEM feed tank fill

Computer halt during Normal to Standby Mode transition

Cemputer halt in Saba tier temperature centre I routine

Low SFWEM celJ vol tage shutdown during feed tank fill

(a) From beginning of integrated system testing

50

Cite Svs/ellls. !Hf.

No.

1

2

3

4

5

6

7

TABLE 10 ARX-l SHUTDOWN SUMMARY

Time. h(a)

28

32

37.5

103.4

270.9

436.4

448.4

Cause

EDCM process air exhaust tempera'ture sensor failu're

Air Supply Bnit electrical noise shutdown

Loss of fluid from SFWEM coolant loop

Supplementary shutdown controller malfunction during SFWEM feed tank fill

Computer halt during Normal to Standby Mode transition

Cemputer halt in Saba tier temperature centre I routine

Low SFWEM celJ vol tage shutdown during feed tank fill

(a) From beginning of integrated system testing

50

Ci/c SlIslclIIS, IHC.

Shper Electrode Testing

A 12-cell SFWEH employing super anode electrodes (l'An-6) was assembled and charged with 25% KOII (by weight) solution. FollOl~ing leak checks and instal­lation in the laboratory breadboard test stand, the feed water compartment was fiUeQ with 25% KOII solution and the module was pressurized to operating pressure by using the N purge supply. The module temperature was raised by qperating a startup heater and the temperature control loop. The module was then started by pressing the ON button on the control panel (Figure 20). At the start of operation the feed water tank was automatically filled with deionized water. During the normal operation it was periodically filled every six hours.

The SFWEN performance is shaWl: in Figure 25 as a function of current density. The average cell voltage of the 12-cell module varied2fro!l1 1.48 to 1.66 V as the current density was spanned from 108 to 538 mA/cm (HlO to 500 ASF). Both the module tempera,ture and pressure were maintained constant at 355 K (180 F) and 993 kPa (144 psia), respectively. Exceptionally good performance (low cell Voltages) was achieved.

Figure 26 shows the SFWEN performance as a function of operating time. Naster test conditions are listed in the figure. The average cell voltage remained low and stable in the range of 1.47 to 1.50 V. Increase of the average cell voltage level over the 250-h testing period was negligible (only 0.02 V) considering the cell voltage variation due to temperature fluctuations.

During testing it was found that a weak spot exists in the baseline module construction in the area of the O

2 exhaust port. The weakness at this loca­

tion is created by a lack of polysulfone support for the electrode assembly limiting the modUle's pressure differential capability. A fix has been iden­tified and has been recommended for implementation in a follow-on program.

Readouts of individual cell voltages showed that the twelve cells performed within an exceptionally tight performance band (1.425 ± 0.015 V). The actual cell voltage distribution is shown below for two typical test times:

Number of Cells Cell Voltage, V At 22 h At 114 h

1.47 7 8 1.48 2 3 1.49 2 1 1.50 1 0

The opera·ting cGnditions were the same as those listed in Figure 26 and read­ings were taken both at 22. hand 114 h of operation.

The exceptionally low cell voltages and their distribution indica,te that the performance Gf super electrodes was successfully retained through scale-up from the single cell to the 12-cell module level. Refer to single cell per­formances under Supporting Technology Studies section of this report, but noting the difference in operating pressures. Increases in pressure will in general increase cell voltages slightly.

51

Ci/c SlIslclIIS, IHC.

Shper Electrode Testing

A 12-cell SFWEH employing super anode electrodes (l'An-6) was assembled and charged with 25% KOII (by weight) solution. FollOl~ing leak checks and instal­lation in the laboratory breadboard test stand, the feed water compartment was fiUeQ with 25% KOII solution and the module was pressurized to operating pressure by using the N purge supply. The module temperature was raised by qperating a startup heater and the temperature control loop. The module was then started by pressing the ON button on the control panel (Figure 20). At the start of operation the feed water tank was automatically filled with deionized water. During the normal operation it was periodically filled every six hours.

The SFWEN performance is shaWl: in Figure 25 as a function of current density. The average cell voltage of the 12-cell module varied2fro!l1 1.48 to 1.66 V as the current density was spanned from 108 to 538 mA/cm (HlO to 500 ASF). Both the module tempera,ture and pressure were maintained constant at 355 K (180 F) and 993 kPa (144 psia), respectively. Exceptionally good performance (low cell Voltages) was achieved.

Figure 26 shows the SFWEN performance as a function of operating time. Naster test conditions are listed in the figure. The average cell voltage remained low and stable in the range of 1.47 to 1.50 V. Increase of the average cell voltage level over the 250-h testing period was negligible (only 0.02 V) considering the cell voltage variation due to temperature fluctuations.

During testing it was found that a weak spot exists in the baseline module construction in the area of the O

2 exhaust port. The weakness at this loca­

tion is created by a lack of polysulfone support for the electrode assembly limiting the modUle's pressure differential capability. A fix has been iden­tified and has been recommended for implementation in a follow-on program.

Readouts of individual cell voltages showed that the twelve cells performed within an exceptionally tight performance band (1.425 ± 0.015 V). The actual cell voltage distribution is shown below for two typical test times:

Number of Cells Cell Voltage, V At 22 h At 114 h

1.47 7 8 1.48 2 3 1.49 2 1 1.50 1 0

The opera·ting cGnditions were the same as those listed in Figure 26 and read­ings were taken both at 22. hand 114 h of operation.

The exceptionally low cell voltages and their distribution indica,te that the performance Gf super electrodes was successfully retained through scale-up from the single cell to the 12-cell module level. Refer to single cell per­formances under Supporting Technology Studies section of this report, but noting the difference in operating pressures. Increases in pressure will in general increase cell voltages slightly.

51

o 100 200

~ 1.S~ :>

• QJ co

'" ... ..-i

In Q .., :>

1

..-i

..-i

~ Q) co <U 1 .. Q)

~

3011

Cu~~ent Density, ASF

400 500 600 700

Tempe~ature. K (F) Pressure, kPa (psis) Charge Cone., % KOH Anode Cathode

2 Cu'rrent Density, mAl em

soo

12 : 355 (180) : 993 (144) : 25 : WMl-6

WCB-2

FlGlffiE 2'5 SFWEM PERFORMANCE VERSUS Cl!rnR'ENT DENSITY

900 1000

h -s.. " ~ ~ ~ ~ •

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Cu~~ent Density, ASF

5eo 600 700 see

, ...

Tempe~ature. K (F) Pressure, kPa (psis) Charge Cone., % KOH Anode Cathode

2 Cu'rrent Density, mAl em

: 12 : 355 (180) : 993 (144) : 25 : WMl-6

WCB-2

FlGlffiE 2'5 SFWEM PERFORMANCE VERSUS Cl!rnR'ENT DENSITY

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1

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, ,: " ,J, .. , !:il', :.'! ;~!I'!:.! ",li;) :,,:i:!Jl!:'i'!j;ilk nf!. Pressure, kPa (pda) 2 Current Density, mA/em (ASP) Charge Cone.. % KeH

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" q t· 'ie'

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FIIGURE 26 PERFGRMANCE GF THE S~ WUH SUPER ELECTRGDES

I

,

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,. , ,

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No. of Cells Tempera,ture, K (F) Pressure, kPa (psia) 2 Current Density, mA/em (ASP) Charge Cone., % KeH Anod'e Cathode

200

Time, h

PERFt!lRMANCE t!lF THE S~ WIITH SUPER ELECTRt!lDES

I

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t-'

Cite SlIslellls. 18t.

Advanced Electrode Testing

A separate, 12-cell SFWEM was assembled and tested using advanced anodes (WAB-5). The test procedures were the same as for the super electrode testing. The performance of the advanced electrodes is presented in Figure 27 along with operating conditions. Though the average cell voltage was slightly higher than that of the super electrodes it remained stable at around 1.58 V throughout the testing period. Several shutdowns were experienced during the 120-day testing period. Most of these shutdowns were, however, related to malfunctions of instrumentation and test stand components, other than the module itself, such as feed pump, coolant pump and solenoid valves. The test stand was built six years ago. It is conceivable that a number of aged com­ponents need repair or refurbishment.

SUPPORTING TECHNOLOGY S1UDIES

A variety of supporting studies were performed to ensure that the OGS was successfully developed and integrated into the ARX-I. Some activities, such as those related to developments of electronics, instrumentation and super electrodes, were covered in the previous sections. This section presents results of four major supporting studies: (1) Single-cell endurance tests, (2) 3-FPC tests, (3) p'roduct gas dehumidification analysis and (4) elimina,tion of stray electrolysis in the coolant loop.

Single Cell Endurance Tests

As part of the testing activities to demonstra'te the hardware maturity of the OGS, a single cell was assembled with one of the super anode electrodes (WAB-6) and endurance tested in a single-cell test stand. A flow(~}hematic of the single-cell test stand was presented in a p'revious report and the cell components are identical to those presented in Figure 9.

A t<>tal of 8,650 h of the single cell operation had been accumulated at the conclusion of the current program. Performance during the period of endu,rance testing is presented in ~igure 28. Operating conditions were set nominally at 352 K (175 F), 161 mA/em (150 ASF) and ambient pressure. Only during the period bet.ween 720 to 1 ,~40 h (specified as "A" in Figure 28) was the current density set at 323 mA/cm (300 ASF). Sligh,t fluctuations on the cell voltage level were mostl}:6due to minor temperature variations. A net voltage change of only 4.6 x Hl V/h was observed over the last 6,500 h. It is noted that the cell voltage levels remained constant during the last 3,000-h period. Throughout the testing there were only two interruptions excluding tlie build­ing power failures. One was due to a pump failure and the other was an inten­tional shu,tdown during the transition period from the previous program and to the current one. The initial(4)440-h testing was conducted under the previous program (Contract NAS2-8682).

The effect of the current <density <>n cell voltage is presented in Figure 29 at different load times for the same electrode used for the above endurance testing. The test conditions also were maintained the same. The performance range of the super electrode is at least 10% better than the state-of-the-art performances (also, see comparisons in Figure 1).

54

Cite SlIslellls. 18t.

Advanced Electrode Testing

A separate, 12-cell SFWEM was assembled and tested using advanced anodes (WAB-5). The test procedures were the same as for the super electrode testing. The performance of the advanced electrodes is presented in Figure 27 along with operating conditions. Though the average cell voltage was slightly higher than that of the super electrodes it remained stable at around 1.58 V throughout the testing period. Several shutdowns were experienced during the 120-day testing period. Most of these shutdowns were, however, related to malfunctions of instrumentation and test stand components, other than the module itself, such as feed pump, coolant pump and solenoid valves. The test stand was built six years ago. It is conceivable that a number of aged com­ponents need repair or refurbishment.

SUPPORTING TECHNOLOGY S1UDIES

A variety of supporting studies were performed to ensure that the OGS was successfully developed and integrated into the ARX-I. Some activities, such as those related to developments of electronics, instrumentation and super electrodes, were covered in the previous sections. This section presents results of four major supporting studies: (1) Single-cell endurance tests, (2) 3-FPC tests, (3) p'roduct gas dehumidification analysis and (4) elimina,tion of stray electrolysis in the coolant loop.

Single Cell Endurance Tests

As part of the testing activities to demonstra'te the hardware maturity of the OGS, a single cell was assembled with one of the super anode electrodes (WAB-6) and endurance tested in a single-cell test stand. A flow(~}hematic of the single-cell test stand was presented in a p'revious report and the cell components are identical to those presented in Figure 9.

A t<>tal of 8,650 h of the single cell operation had been accumulated at the conclusion of the current program. Performance during the period of endu,rance testing is presented in ~igure 28. Operating conditions were set nominally at 352 K (175 F), 161 mA/em (150 ASF) and ambient pressure. Only during the period bet.ween 720 to 1 ,~40 h (specified as "A" in Figure 28) was the current density set at 323 mA/cm (300 ASF). Sligh,t fluctuations on the cell voltage level were mostl}:6due to minor temperature variations. A net voltage change of only 4.6 x Hl V/h was observed over the last 6,500 h. It is noted that the cell voltage levels remained constant during the last 3,000-h period. Throughout the testing there were only two interruptions excluding tlie build­ing power failures. One was due to a pump failure and the other was an inten­tional shu,tdown during the transition period from the previous program and to the current one. The initial(4)440-h testing was conducted under the previous program (Contract NAS2-8682).

The effect of the current <density <>n cell voltage is presented in Figure 29 at different load times for the same electrode used for the above endurance testing. The test conditions also were maintained the same. The performance range of the super electrode is at least 10% better than the state-of-the-art performances (also, see comparisons in Figure 1).

54

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'm CIJ

.. as

0,"

, o

"::'.t:l~'" Z~P04UU

to)

., ., 00

11"'_

° ., N

0 0

0

. .

'" ....

. 1,.

.• 1--.,

., --i .• ..:-; '!

"·I"-'*~A":,,--.;..· +c~··

.. ;

'" '"

... ...

55

N

0

... ...

': "":<i":'t

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C •

0 CO CO .... CO CO 0

0

CO CO

'" o CO N

.0 .r: •

.. $1 f-<

< ~~ ."<'

:> . .. '"

OIl

"" '" ... ..... ~~

:0-

.-1

.-1 .. U

H)(~a

,"01,'.

Temperature, K (F) Pressure 2 Current Density, mA/em (AS'F) Charge Cone., % K0H Anode Cathode

353 (175) Ambient 161. (150)

: 25 : WAB-6

WCB-2

2aaa 3aOfl 4aoo 50aa 6aaa 7iaaa 8aoo 9aoo 0pe-rat ing Time, h

FEGURE 28 SINGLE CELL PERF0RMANCE DURING ENDURANCE TEST

::,"'~;

laoao

~ ~ ~

~ ~ ~ ~

~-l"

:> . .. OIl

'" '" "" ... ..... ~~

:0-

.-1 , .-1 i

.. u

1.0

1a00

Temperature, K (F) Pressure 2 Current Density, mA/em (AS'F) Charge Cone., % K0H Anode Cathode

353 (175) Ambient 161. (150)

: 25 : WAB-6

WCB-2

2000 3000 4000 5000 6aoo 80ao 9000

0pe·rat ing Time, h

FEGURE 28 SINGLE CELL PERF0RMANCE DURING ENDURANCE TEST

10000

~ . OJ ..

en .. ... ... ..... 0 ~

~ .... ,Il! ~

Curren~ Density, ASF

o 800

.< • " l:Jitlir.ltt;ct:fl!W . E.r- " ;-~~mm~l~~- t' ~J.+'.; ~~;.1lrFH!r-:!fHillH ·'1'001_.··.·······'.· ill t ;t·_'~!n.,~,'r.l~

1 9 I" 'I" .. "1 • .p' ....... "

1.8~;~

1.7

1.6 I, "1 ttl t; i ,;.:;;.i 'i.i" ,;,;:: ;. "F;·; ,'l' ,'Ii JT,;;)'" ii ~jl~·l±tll±lri 't'lltjt:"lltlffiilljlHJIt'tlti i HtIlll]; jjjjlfll'J.l.l; lif!' IlIll!1jtPtf"jFijilIBIU W ttt ... -.- L • ,.IT ...... -t. ", "" ·.·,I·!~_ .• ~ .. -..•. ," ~.I .1:,J ____ .11 t u ~;. l. ...... .:.... .1 .......... ~l.. :J .... , ,_, .• J.ill ,d,,~ , •. M. ~H" ..

o o 100 206 306 466 560 606 2 Current nensity, mAl em

700 800 900

FIGURE 29 SUPER ELECTR6DE PERF0RMANCE VERSUS CURRENT DENSITY

,

1000

..

:'

h ~ ~ ~ I ~

~ :"

, ,/

o

1.9 [:;)

0 0

1.8 0

~ . OJ .. 1.7 en .. ... ... ..... 0 ~

~ .... . Il! ~ 1.6

1.5

1.4

01ll1!ili1:!iB o 100

200 300

o h

269i h 10/77

3242 h 8/78

7428 h 4/79

200 300

Curren~ Density, ASF

400 500 600

4(!)0 500 600 2 Current Density, mAl em

700 800

~

700 800 900

FIGURE 29 SUPER ELECTR0DE PERF0RMANCE VERSUS CURRENT DENSITY

900

..

1000 =~

1000

Cite SlIslellls. JHf.

Three-Fluid Pressure Controller Tests

The 3-FPC of the OGS was extensively tested (approximately 9000 h) as part of the ARX-l test program. The ARX-l provided a "real-life" test facility since .. it combined all three major elements of the controller (mecnanical, electrical and software) in one loca tion. The mechanical po.rtion consisted of the motor-driven regulators and sources of O2 and H2 from the OGS at the design flow rates. In addition, the time variations of the flow rates as they occur during a water feed tank fill (i.e., flows cease) were implemented. The elec-trical elements were the pressure t.ransducers, their signal conditioning and motor drive circuitry. The software contained the control routines for actu-ating the regulators in response to pressure level inputs.

Early in the testing phase it was found that the originally selected miniature, solid-state, differential pressure transducers exhibited certain undesirable characteristics. While the sensed pressure differentia::'- were reproducible, the response level was found to be a function of absolute pressure. Figure 30 illustrates the typical behavi0r. A mechanical transducer (ordinate) reading is compared to the solid state transducer (abscissa) reading at vari0us system pressures. Ideally, all Curves would be c<mgruent, have positive s10pes and pass thr0ugh the origin. Only the curve for zer0 system pressure (atmospheric pressure) had a positive slope. The intercept can be adjusted with signal conditioning. At other pressures, h0wever, the data sh0wed large scatter and slope changes as a functi0n of pressure. The severity 0f the changes as well as the data scatter precluded use of the miniature pressure transducers of the type eriginally selected. The central ef the SFWEN internal cavity pressures and pressure differen·tials are sufficiently critical that reliable transducers are needed. It was fer this reason that the controller was medified to accept mechanical transducers with electrical outputs te cemplete the testing. There were ne further preblems with pressure sensing.

Anether asp.ect of the centreller testing was selection ef the proper parameters in the software control routines to obtain the desired dynamic response in the regulaters. Complex interactions ameng regulater seat travel, rotatien rate, gas flow rate, pressure and contr01 parameters (such as signal sample time, resp0nse time, response rate and waiting perioo-s be'tween successive regulator stepping) were analyzed and evaluated. Adjustments were made so that the OGS would experience only pressure changes Idtllin the tolerance band during startup pressurization, normal operation and shutdown depressurization. Table 11 summarizes the operating conditions of the controller that were used during most of the testing.

Several areas were identified for additional improvements and m0dification of the controller. Vendor discussions indicated that solid-state pressure trans­ducers can be found which will give the required performance. Additional analysis is required to relate control routine parameters with mechanical aspects such as orifice sizes, valve thread size and pitch, flow rates and l',ressure l"vels, so that optimum conditions can be established for any ca'l'a-city OGS. Also, the weight of the eoh,troller can be rpdueed and the package streamlined. These modifications have been recommended f0r follow-on activities.

58

Cite SlIslellls. JHf.

Three-Fluid Pressure Controller Tests

The 3-FPC of the OGS was extensively tested (approximately 9000 h) as part of the ARX-l test program. The ARX-l provided a "real-life" test facility since .. it combined all three major elements of the controller (mecnanical, electrical and software) in one loca tion. The mechanical po.rtion consisted of the motor-driven regulators and sources of O2 and H2 from the OGS at the design flow rates. In addition, the time variations of the flow rates as they occur during a water feed tank fill (i.e., flows cease) were implemented. The elec-trical elements were the pressure t.ransducers, their signal conditioning and motor drive circuitry. The software contained the control routines for actu-ating the regulators in response to pressure level inputs.

Early in the testing phase it was found that the originally selected miniature, solid-state, differential pressure transducers exhibited certain undesirable characteristics. While the sensed pressure differentia::'- were reproducible, the response level was found to be a function of absolute pressure. Figure 30 illustrates the typical behavi0r. A mechanical transducer (ordinate) reading is compared to the solid state transducer (abscissa) reading at vari0us system pressures. Ideally, all Curves would be c<mgruent, have positive s10pes and pass thr0ugh the origin. Only the curve for zer0 system pressure (atmospheric pressure) had a positive slope. The intercept can be adjusted with signal conditioning. At other pressures, h0wever, the data sh0wed large scatter and slope changes as a functi0n of pressure. The severity 0f the changes as well as the data scatter precluded use of the miniature pressure transducers of the type eriginally selected. The central ef the SFWEN internal cavity pressures and pressure differen·tials are sufficiently critical that reliable transducers are needed. It was fer this reason that the controller was medified to accept mechanical transducers with electrical outputs te cemplete the testing. There were ne further preblems with pressure sensing.

Anether asp.ect of the centreller testing was selection ef the proper parameters in the software control routines to obtain the desired dynamic response in the regulaters. Complex interactions ameng regulater seat travel, rotatien rate, gas flow rate, pressure and contr01 parameters (such as signal sample time, resp0nse time, response rate and waiting perioo-s be'tween successive regulator stepping) were analyzed and evaluated. Adjustments were made so that the OGS would experience only pressure changes Idtllin the tolerance band during startup pressurization, normal operation and shutdown depressurization. Table 11 summarizes the operating conditions of the controller that were used during most of the testing.

Several areas were identified for additional improvements and m0dification of the controller. Vendor discussions indicated that solid-state pressure trans­ducers can be found which will give the required performance. Additional analysis is required to relate control routine parameters with mechanical aspects such as orifice sizes, valve thread size and pitch, flow rates and l',ressure l"vels, so that optimum conditions can be established for any ca'l'a-city OGS. Also, the weight of the eoh,troller can be rpdueed and the package streamlined. These modifications have been recommended f0r follow-on activities.

58

:

01

~ . .-I

~ ~ ClI

'" ClI .... .... ... ~ ClI

~ III III ClI

'" ""

Ci/e Sl/SleHlI, lH

C.

System

Curve

Pressu

rel

kPa ~l2sia)

0 738

(107)

A

614 (89)

0 448

(65)

0 138

(20

)

\7 103

(15)

Solid~State Transducer O

utput (R

elative M

agnitude Only)

FIGU

RE 30 TH

REE-FLB:J:p PRESSURE ceN

TReLLER

-SO

LID

STATE TRANSDUCER CH

ARA

CTERISTICS 59

4.0

3.0

'0

.,.. Ul

., • .-I 01

2.0

.... ... ai '" ClI .... .... 0" "" ClI ~ ., til ClI

&::

1.0

o

!I 1 .j 1 i j

:

01

~ . .-I

~ ~ ClI

'" ClI .... .... ... ~ ClI

~ III III ClI

'" ""

Ci/e Sl/SleHlI, lH

C.

System

Curve

Pressu

rel

kPa ~l2sia)

0 738

(107)

A

614 (89)

0 448

(65)

0 138

(20

)

\7 103

(15)

Solid~State Transducer O

utput (R

elative M

agnitude Only)

FIGU

RE 30 TH

REE-FLB:J:p PRESSURE ceN

TReLLER

-SO

LID

STATE TRANSDUCER CH

ARA

CTERISTICS 59

4.0

3.0

'0

.,.. Ul

., • .-I 01

2.0

.... ... ai '" ClI .... .... 0" "" ClI ~ ., til ClI

&::

1.0

o

!I 1 .j 1 i j

Cite SVSICHlS, lH~.

TABLE 11 THREE-FLUID PRESSURE CONTROLLER NOMINAL OPERATING CONDITIONS

Characteristic

A. ~Iechanical

Gas Type

Upstream Pressure, kPa (psia)

Downstt'eam Pressure, kPa (psia)

Upstream-to-Water Feed &P, kPa (psid)

Mass Flow Rate, g/min (Ibid)

Volumetric Flow, slpm (scfm)

B. Control

Actuation Time(a) s ,

Minimum Waiting Period(b), s

System

O2

1035 (150)

103 (15)

0

1.07 (3.4)

0.8 (0.028)

0.1 (Max)

10

Regulator __ =il,2 __ _

O2 H2

1060 (154) 1050 (152)

1035 (150) 114 (16.5)

28 (4.0) 17 (2,5)

1.07 (3.4) 0.134 (0.42)

0.8 (0.028) 1.6 (0.056)

13.6 7.6

40 23

(a) Time for regulator to respond to 6.9 kPa (1 psid) sensed differential pressure. Response only occurs if level is not within control range.

(b) Between successive regulator advances.

60

4 , , , ~

'.

Cite SVSICHlS, lH~.

TABLE 11 THREE-FLUID PRESSURE CONTROLLER NOMINAL OPERATING CONDITIONS

Characteristic

A. ~Iechanical

Gas Type

Upstream Pressure, kPa (psia)

Downstt"eam Pressure, kPa (psia)

Upstream-to-Water Feed &P, kPa (psid)

System

O2

1035 (150)

103 (15)

0

Regulator

O2 H2

1060 (154) 1050 (152)

1035 (150) 114 (16.5)

28 (4.0) 17 (2" 5)

Mass Flow Rate, g/min (Ibid) 1.07 (3.4) 1.07 (3.4) 0.134 (0.42)

Volumetric Flow, slpm (scfm) 0.8 (0.028) 0.8 (0.028) 1.6 (0.056)

B. Control

Actuation Time(a) s , 0.1 (Max) 13.6 7.6

Minimum Waiting Period(b), s 10 40 23

(a) Time for regulator to respond to 6.9 kPa (1 psid) sensed differential pressure. Response only occurs if level is not within control range.

(b) Between successive regulator advances.

60

".

.'

Ci/e SIII/eml, IHC.

Product Gas Dehumidification Analysis

Past development efforts of water electrolysis-based OGS's identified dew point control of product gases as one of the obstacles to be overcome. Dehu­midification of product gases from water electrolysis subsystems is necessary when the product gases have a dew point greater than thf> maximum allowable dew point level within the cabin or greater than their dry bu:? temperatures. GenerallY the spacecraft atmosphere requires that the dew-pot2~ of the OGS product gases (H2 and 02) should be lower than 287 K (57 F).

Direct application of conventional condenser/separators to the water vapor removal from the OGS product gases was not deemed desirable because of the zero gravity environment. Three techniques among various approaches to solve the problem have been considered to be the most practical. These are:

1. Low temperature operation 2. Electrolytic dehumidification 3. Line heating with the gas expansion

The previous programs (Contracts NAS2-7470 and NAS2-8682) have(2o~~sed on fur­ther development of the electrolytic dehumidification concept. '

ConcePt: Descriptions

The dew point of the product gases is a function of the operating conditions of the water electrolySis module such as temperature, pressure and KOH concen­tration. Their effects on the product gas dew point are presented in Figure 31. The dew point can be reduced either by increasing operating pressure and the KOll concentration or by decreasing operating temperature.

Low Temperature Operation. The dew point of 287 K (57 F) corresponds to a water vapor pressure of 1.60 kPa (12 mm Hg). This vapor pressure level can be obtained directly within the module itself by d"creasing temperature. For example, the water vapor partial pressure of a gas saturated with a 33.3% KOIl (by weight) solution at 297.6 K (75.7 F) and 101 kPa (14.7 psia) is 1.60 kPa (12 min Hg) which corresponds to a dew paint of 287 K (57 F) at 101 kPa (14.7 psia).

Though this method is the simplest and most reliable among the three methods considered, it has been eliminated due to high power needs (increased cell vol tage) at low temperatures. The driving force (water vapor p,ressure gradient) for the water vapor transport is also low at lower temperatures, resulting in current density limita,tions.

Electrolytic Dehumidificoation (ED). The ED concept uses water vapor electroly­sis to remove the water vapor carried with the product gases. The 02 and H2 from the main electrolysis module are passed respectively through the anode and ca'thode cavities of the water vapor electrolysis cells of the ED module. Wa,ter vapor is then absorbed in electrolyte and electrolyzed to form additional 02 and H2 .Detailed descriptt2n~)of the ED concept and its development activi­t1es are presented elsewhere. '

61

.'

Ci/e SIII/eml, IHC.

Product Gas Dehumidification Analysis

Past development efforts of water electrolysis-based OGS's identified dew point control of product gases as one of the obstacles to be overcome. Dehu­midification of product gases from water electrolysis subsystems is necessary when the product gases have a dew point greater than thf> maximum allowable dew point level within the cabin or greater than their dry bu:? temperatures. GenerallY the spacecraft atmosphere requires that the dew-pot2~ of the OGS product gases (H2 and 02) should be lower than 287 K (57 F).

Direct application of conventional condenser/separators to the water vapor removal from the OGS product gases was not deemed desirable because of the zero gravity environment. Three techniques among various approaches to solve the problem have been considered to be the most practical. These are:

1. Low temperature operation 2. Electrolytic dehumidification 3. Line heating with the gas expansion

The previous programs (Contracts NAS2-7470 and NAS2-8682) have(2o~~sed on fur­ther development of the electrolytic dehumidification concept. '

ConcePt: Descriptions

The dew point of the product gases is a function of the operating conditions of the water electrolySis module such as temperature, pressure and KOH concen­tration. Their effects on the product gas dew point are presented in Figure 31. The dew point can be reduced either by increasing operating pressure and the KOll concentration or by decreasing operating temperature.

Low Temperature Operation. The dew point of 287 K (57 F) corresponds to a water vapor pressure of 1.60 kPa (12 mm Hg). This vapor pressure level can be obtained directly within the module itself by d"creasing temperature. For example, the water vapor partial pressure of a gas saturated with a 33.3% KOIl (by weight) solution at 297.6 K (75.7 F) and 101 kPa (14.7 psia) is 1.60 kPa (12 min Hg) which corresponds to a dew paint of 287 K (57 F) at 101 kPa (14.7 psia).

Though this method is the simplest and most reliable among the three methods considered, it has been eliminated due to high power needs (increased cell vol tage) at low temperatures. The driving force (water vapor p,ressure gradient) for the water vapor transport is also low at lower temperatures, resulting in current density limita,tions.

Electrolytic Dehumidificoation (ED). The ED concept uses water vapor electroly­sis to remove the water vapor carried with the product gases. The 02 and H2 from the main electrolysis module are passed respectively through the anode and ca'thode cavities of the water vapor electrolysis cells of the ED module. Wa,ter vapor is then absorbed in electrolyte and electrolyzed to form additional 02 and H2 .Detailed descriptt2n~)of the ED concept and its development activi­t1es are presented elsewhere. '

61

Cift SUS/tillS. JH~.

The water vapor electrolysis of ambient air is a proven technology. Technical feasibility of it~2a~ylication for dehumidification of the OGS product gases was demonstrated. '

One advantage of the ED concept is the almost total utilization of water processed by the main electrolysis system, including the water vapor normally carried away with the product gas streams. By operating the electrolytic dehumidifier upstream of any system pressure regulators, t.race heating of lines and·regulators can be eliminated. Another advantage is the ED in combi­nation with gas expansion will produce much drier gases than other techniques.

Disadvantages of the ED concept are requirements of water vapor electrolysis cells, additional power supply and control/monitor instrumentation, and possible increases in maintenance requ:Lrements.

Line Heating with GilS E)g!ansign. The partial pressure of water vapor in a given gas mixture is directly proportional to the total gas pressure. Accord­ingly, one simple way of reduCing the partial pressure of water vapor is to reduce the total gas pressure through gas expansion. For example, the dew point of ~87 K (57 F) can be achieved by operating the electrolysis module at 1.24 x 10 kPa (180 pSia), 353 K (175 F) and 40% KOH concentration (see Figure 31). In order to prevent water vapor from condensing in the product gas line, pressure regulators and the lines between the module and regulators may have to be heated depending on the operating temperature and ambient conditions.

Advantages of this technique aFe the simplicity of the concept and its opera­tion, less hardware camplexity and weight, and virtually no maintenance re­quirements.

Disadvantages are those associated with higher pressure operatiml and require­ments for component hea'ting and additional insula,tion. These disadvantages can be lessened by mounting the pressure regulators clase to the module to limit line lengths and heating requirements.

Selected Approach

Among the three p,ractical approaches described, the first method is definitely the simplest one. However, it was eliminated from further consideration because of the greater power penalty and operatianal current density limitations. The other two methods are equally attractive and are comparable in many "ays. Qualita'tive comparisons are summarized in Table 12 with the "X" marked technique being considered to be slightly more favorable. In overall, the line heating approach is favored.

Quantitative comparisons of the twa methods were made by the use of overall energy balances far a three-persan capacitY(~G~) Design details of the three­person capacity OGS can be found elsewhere.' Operating conditions, used as a basis in the energy balance calculations, are presentee! in Table 13. Results of the energy balance calculations are presented in Table 14. LiqUid phase water at 298 K (77 F) was taken as a reference state. Heat losses were esti­mated by assuming that heated eompanetJ.!ts were covered with 5.1 em (2 in) -thick

62

Cift SUS/tillS. JH~.

The water vapor electrolysis of ambient air is a proven technology. Technical feasibility of it~2a~ylication for dehumidification of the OGS product gases was demonstrated. '

One advantage of the ED concept is the almost total utilization of water processed by the main electrolysis system, including the water vapor normally carried away with the product gas streams. By operating the electrolytic dehumidifier upstream of any system pressure regulators, t.race heating of lines and·regulators can be eliminated. Another advantage is the ED in combi­nation with gas expansion will produce much drier gases than other techniques.

Disadvantages of the ED concept are requirements of water vapor electrolysis cells, additional power supply and control/monitor instrumentation, and possible increases in maintenance requ:Lrements.

Line Heating with GilS E)g!ansign. The partial pressure of water vapor in a given gas mixture is directly proportional to the total gas pressure. Accord­ingly, one simple way of reduCing the partial pressure of water vapor is to reduce the total gas pressure through gas expansion. For example, the dew point of ~87 K (57 F) can be achieved by operating the electrolysis module at 1.24 x 10 kPa (180 pSia), 353 K (175 F) and 40% KOH concentration (see Figure 31). In order to prevent water vapor from condensing in the product gas line, pressure regulators and the lines between the module and regulators may have to be heated depending on the operating temperature and ambient conditions.

Advantages of this technique aFe the simplicity of the concept and its opera­tion, less hardware camplexity and weight, and virtually no maintenance re­quirements.

Disadvantages are those associated with higher pressure operatiml and require­ments for component hea'ting and additional insula,tion. These disadvantages can be lessened by mounting the pressure regulators clase to the module to limit line lengths and heating requirements.

Selected Approach

Among the three p,ractical approaches described, the first method is definitely the simplest one. However, it was eliminated from further consideration because of the greater power penalty and operatianal current density limitations. The other two methods are equally attractive and are comparable in many "ays. Qualita'tive comparisons are summarized in Table 12 with the "X" marked technique being considered to be slightly more favorable. In overall, the line heating approach is favored.

Quantitative comparisons of the twa methods were made by the use of overall energy balances far a three-persan capacitY(~G~) Design details of the three­person capacity OGS can be found elsewhere.' Operating conditions, used as a basis in the energy balance calculations, are presentee! in Table 13. Results of the energy balance calculations are presented in Table 14. LiqUid phase water at 298 K (77 F) was taken as a reference state. Heat losses were esti­mated by assuming that heated eompanetJ.!ts were covered with 5.1 em (2 in) -thick

62

:

315

310

305

300

~ • 295 ... ~ ~ ~ '" 290

285

280

275

o

Cite S,Is/ellis. Inc.

100

Operating Pressure, psia 200 300 400 500 ,600 110

D~w Po.int Pi exp""ded Gases

As a function of operating pressure for operating temperature, electrolyte concentration and cabin pressure indicated.

(200 F), 35% KOB, 103 kPa (15 psia)

w-\---=' 366 K (200 F), 40% KOH, 103 kPa (15 psia)

.... >,-+~ 366 K (200 F), 35% KOH, 69 kPa (10 psia)

\ot\-l,-\- 352 K (175 F), 35% KOB, 103 kP" (15 psia)

~\-'\""""r-~ 352 K (175 F), 40% KOB, 103 kPa (15 psis)

100

90

80

~~...-l."""":~-->', 352 K (175 F), 35% KOB, 69 kPa (10 psia)

60

50

40

30

o ~_""""""",_---:-:~_~~_~" _.......,-L.... ____ .L..'"""'"'"-L....~ ......... J.....J""IO o SOO 1000 1500 2000 2500 3000 3500 4000

OpersUngl'r(",s.!.lre, kP ..

FIGURE 31 PRODGe \ cg!,S DEW POINT

63

I I I I

'\

:

315

310

305

300

~ • 295 ... ~ ~ ~ '" 290

285

280

275

Cite S,Is/ellis. Inc.

Operating Pressure, psis

;0~ __ ...;1:.::0;.0 __ ~..:2:.::0;:.0 __ ~..::3;00r-__ ~4::;00r-=_....::.50,O:..-___ ,..:60"0 110

D~w PO,int Pi exp""d~d Gases

As a function of operating pressure for operating temperature, electrolyte concentration and cabin pressure indicated.

(200 F), 35% KOH, 103 l<Pa (15 psia)

w-\---=' 366 K (200 F), 40% KOH, 103 l<Pa (15 psia)

..... >,-+~ 366 K (200 F), 35% KeH, 69 l<Pa (10 psia)

\ot\.....l,.-*- 352 K (175 F), 35% KOH, 103 l<P" (15 psia)

'l4-\-"t--'r->~ 352 K (175 F), 40% KOH, 103 l<Pa (15 psis)

100

90

80

~~....-lc---'~~, 352 K (175 F), 35% KOH, 69 l<Pa (10 psia)

60

50

40

30

o ~----,~--::-~--,:"b:--~" _ ......... .l....o. __ .L...-........ ~L....~ ........ L....J""(O o SOO 1000 1500 2000 --2500" 3000 3500 4000

OpersUngl'r(",s.!.lre, kP ..

FIGURE 31 PRODGe \ cg!,S DEW POINT

63

I I I I

'\

Ci/e Svs/ellls. JHe.

TABLE 12 COMPARISON OF ED AND LINE HEATING AFPROACH FOR DEHUMIDIFICATION

Category

Overall System lIardware Iveight Simplicity (No. of parts)

Power Requirement

lIeat Rejection

~Ia intenance

Reliability

Flexibilities in Operational Temperatures

Dew Point of Product Gases

ED

X

X

(a) ~Iore favorable approach iR marked by "X"

64

Line Heating Remarks

X(a)

X

X Very close

X Very close

X

X

LH has a limit

"

Ci/e Svs/ellls. JHe.

TABLE 12 COMPARISON OF ED AND LINE HEATING AFPROACH FOR DEHUMIDIFICATION

Category

Overall System lIardware Iveight Simplicity (No. of parts)

Power Requirement

lIeat Rejection

~Ia intenance

Reliability

Flexibilities in Operational Temperatures

Dew Point of Product Gases

ED

X

X

(a) ~Iore favorable approach iR marked by "X"

64

Line Heating Remarks

X(a)

X

X Very close

X Very close

X

X

LH has a limit

"

!

Cife Sus/ellis. Inc.

TABLE 13 OPERATING CONDITIONS AND CHARACTERISTICS OF A THREE-PERSON CAPACITY OGS

Descriptions

No. of Cells

Current Density, mA/cm2 (ASF) SFIVEN Eml

Temperature, K (F)

Pressure, kPa (psia)

O2 Production, kg/d (Ibid)

H2 Production, kg/d (Ibid)

Average Cell Voltage, V SFWE~I

EmJ

Product Gas Temp., K (F)

Feed IVa ter Temp., l( (F)

65

ED

92.9 (0.1)

33

206 (191) 47 (44)

356 (180)

965 (140)

4.19 (9.24)

0.53 0.16)

1.5 1.65

317 (no)

294 (70)

Line Heating

92.9 (0.1)

30

210 (195) Not Applicable

356 (180)

2141 (I80)

4.19 (9.24)

0.53 (1.16)

1.5 Not Applicable

317 (110)

294 (70)

!

Cife Sus/ellis. Inc.

TABLE 13 OPERATING CONDITIONS AND CHARACTERISTICS OF A THREE-PERSON CAPACITY OGS

Descriptions

No. of Cells

Current Density, mA/cm2 (ASF) SFIVEN Eml

Temperature, K (F)

Pressure, kPa (psia)

O2 Production, kg/d (Ibid)

H2 Production, kg/d (Ibid)

Average Cell Voltage, V SFWE~I

EmJ

Product Gas Temp., K (F)

Feed IVa ter Temp., l( (F)

65

ED

92.9 (0.1)

33

206 (191) 47 (44)

356 (180)

965 (140)

4.19 (9.24)

0.53 0.16)

1.5 1.65

317 (no)

294 (70)

Line Heating

92.9 (0.1)

30

210 (195) Not Applicable

356 (180)

2141 (I80)

4.19 (9.24)

0.53 (1.16)

1.5 Not Applicable

317 (110)

294 (70)

~;'

Cite SIIS/(IIIS. lNf.

TABLE 14 SUMMARY OF ENERGY BALANCES

(Basis: 1 day of operation; Reference temperature, 298 K (77 F))

Electrolytic Dehumidification (ED)

• • • • • •

Description

Enthalphy of H20 Enthalpy of Products Electricity (881 Iy) Standard Heat of Reaction Heating (20 W) Heat Losses (Penalty 28 W)

Total

Line Hea ting

__________ ~D~e~s~cription

• • • • • •

Enthalpy of H2

0 Enthalpy of Products Electricity (878 W) Standard Heat of Reaction Heating (20 W) Heat Losses (24 W)

Total

Comparison of Weight Penalties

• • •

Description

Fixed Hardware(a), kg (lb)

Power Penalty(b) (DC), kg (lb)

Heat Rejection Penalty, kg (lb) Total

Input kr.:al (Btu)

-19 (-74)

18,203 (72,178)

412 (1,632)

18,596 (73,736)

Input kcal (Btu)

-19 (-74)

18,123 (71,861)

416 (1,650)

18,520 (73,437)

ED

9 (20)

242 (534)

6 (B) 257 (567)

Output kca1 (Btu)

117 (465)

17 , 899 (70,972)

580 (2,300) 18,596 (73,737)

Output kcal (Btu)

117 (465)

17 , 899 (70,972)

504 (2,000) 18,520 (73,437)

Line Heating

1 (2)

241 (531)

5 (11) 247 (544)

(a) Dehumidifying section only. Fixed hardware weight of the rest of the subsys telll should be the same for both cases.

(b) Based on 0.268 kg/W (0.590 lb/W) for DC power and 0.198 kg/W (0.436 lb/W) for heat rej.prtion. AC power penalty for instrumeIlt~tiGn was not considered. Would be approximately the same for either approach.

66

'.

~;'

Cite SIIS/(IIIS. lNf.

TABLE 14 SUMMARY OF ENERGY BALANCES

(Basis: 1 day of operation; Reference temperature, 298 K (77 F))

Electrolytic Dehumidification (ED)

• • • • • •

Description

Enthalphy of H20 Enthalpy of Products Electricity (881 Iy) Standard Heat of Reaction Heating (20 W) Heat Losses (Penalty 28 W)

Total

Line Hea ting

• • • • • •

Description

Enthalpy of H2

0 Enthalpy of Products Electricity (878 W) Standard Heat of Reaction Heating (20 W) Heat Losses (24 W)

Total

Comparison of Weight Penalties

• • •

Description

Fixed Hardware(a), kg (lb)

Power Penalty(b) (DC), kg (lb)

Heat Rejection Penalty, kg (lb) Total

Input kr.:al (Btu)

-19 (-74)

18,203 (72,178)

412 (1,632)

18,596 (73,736)

Input kcal (Btu)

-19 (-74)

18,123 (71,861)

416 (1,650)

18,520 (73,437)

ED

9 (20)

242 (534)

6 (B) 257 (567)

Output kca1 (Btu)

117 (465)

17 , 899 (70,972)

580 (2,300) 18,596 (73,737)

Output kcal (Btu)

117 (465)

17 , 899 (70,972)

504 (2,000) 18,520 (73,437)

Line Heating

1 (2)

241 (531)

5 (11) 247 (544)

(a) Dehumidifying section only. Fixed hardware weight of the rest of the subsys telll should be the same for both cases.

(b) Based on 0.268 kg/W (0.590 lb/W) for DC power and 0.198 kg/W (0.436 lb/W) for heat rej.prtion. AC power penalty for instrumeIlt~tiGn was not considered. Would be approximately the same for either approach.

66

'.

Cite Sus/eHls, Inc.

Min-K insulation and highly polished aluminum shield. Results of the weight penalties comparison indicate that the total weight penalty for line heating would be approximately 10 kg (22 lb) less than that of electrolytic dehumidifi-

.s cation.

In conclusion, both ED and line heating approaches are technically feasible and equally attractive in some ways. However, close comparison reveals that the line heating technique is slightly more favored with less total weight penalty, less system complexity and less maintenance requirements. Accordingly it was recommended that the line heating should be baselined for the OGS and that the ED be kept as a backup.

Elimination of Stray Electrolysis in the Coolant Loop

fluring the endurance testing of a 12-cell SFWEM it was observed that corrosion was occurring in the last coolant compartment bipolar plate. This corrosion was identified as a result of unwanted stray electrolysis in the coolant loop due to a high potential difference between the last current collector (approxi­ma'tely at 20 V) and the end plate (at zero electrical potential). Such a high potential difference across a common liquid coolant medium (water) caused the wa,ter to be electrolyzed.

The stray electrolysis in th" coolant loop had not been observed previously while testing prior electrolysis modules consisting of six cells or less. For six-cell modules the voltage between the last cellon the high voltage end and the endplate was less than 10 V. With the 12-cell modules the voltage differ­ential is closer to 20 V.

The insulation utilized between the last current collector and the endplate was adequate to withstand 10 V but is not able to withstand the near 20 V. As a- result, a corrosion current flow OCCllrs invelving metal ion dissolution, meaning metal is oxidized and water redueed.

Sinee future subsystems will have more than 12 cells per module this problem must be eliminated. Ia order to correct this problem a special fluid line connect<H, similar to that used for the water feed compartment interface, was fabricated and installed to provide for at least a 5 cm (2 in) insulation between the metallic components. Subsequent tests indieated that the modifiea­tion effectively eliminated the stray electrolysis problem.

CONCLlifSTONS

The following eonclusions are direct results of the p'rogram activities:

1. Int.egrated testing of the OGS a,nd the WHS with the ARX-i has demon~ strated tha't the integration concept of the ARS is feasible.

2. An OGS using the SFWE concept has a poten,tial of being one of the Simplest and most reliable OGS's with low weight and power penalties.

3. The Contractor-developed super anode electrodes (WAB-6) have made it possible to reduce the power eonsumption of state-of-the-art water electrolysis by approximately 10%.

67

Cite Sus/eHls, Inc.

Min-K insulation and highly polished aluminum shield. Results of the weight penalties comparison indicate that the total weight penalty for line heating would be approximately 10 kg (22 lb) less than that of electrolytic dehumidifi-

.s cation.

In conclusion, both ED and line heating approaches are technically feasible and equally attractive in some ways. However, close comparison reveals that the line heating technique is slightly more favored with less total weight penalty, less system complexity and less maintenance requirements. Accordingly it was recommended that the line heating should be baselined for the OGS and that the ED be kept as a backup.

Elimination of Stray Electrolysis in the Coolant Loop

fluring the endurance testing of a 12-cell SFWEM it was observed that corrosion was occurring in the last coolant compartment bipolar plate. This corrosion was identified as a result of unwanted stray electrolysis in the coolant loop due to a high potential difference between the last current collector (approxi­ma'tely at 20 V) and the end plate (at zero electrical potential). Such a high potential difference across a common liquid coolant medium (water) caused the wa,ter to be electrolyzed.

The stray electrolysis in th" coolant loop had not been observed previously while testing prior electrolysis modules consisting of six cells or less. For six-cell modules the voltage between the last cellon the high voltage end and the endplate was less than 10 V. With the 12-cell modules the voltage differ­ential is closer to 20 V.

The insulation utilized between the last current collector and the endplate was adequate to withstand 10 V but is not able to withstand the near 20 V. As a- result, a corrosion current flow OCCllrs invelving metal ion dissolution, meaning metal is oxidized and water redueed.

Sinee future subsystems will have more than 12 cells per module this problem must be eliminated. Ia order to correct this problem a special fluid line connect<H, similar to that used for the water feed compartment interface, was fabricated and installed to provide for at least a 5 cm (2 in) insulation between the metallic components. Subsequent tests indieated that the modifiea­tion effectively eliminated the stray electrolysis problem.

CONCLlifSTONS

The following eonclusions are direct results of the p'rogram activities:

1. Int.egrated testing of the OGS a,nd the WHS with the ARX-i has demon~ strated tha't the integration concept of the ARS is feasible.

2. An OGS using the SFWE concept has a poten,tial of being one of the Simplest and most reliable OGS's with low weight and power penalties.

3. The Contractor-developed super anode electrodes (WAB-6) have made it possible to reduce the power eonsumption of state-of-the-art water electrolysis by approximately 10%.

67

Cif~ SI!$f~III$. !HC.

4. The WAB-6 super electrodes have been endurance-tested for more than 8,650 hours. Thoughout the endurance testing, the performance of the electrodes has been steady and no indication of degradation has been observed.

5. The performance of WAB-6 electrodes has been demonstrated to be reproducible. Twelve super electrodes have been fabricated and tested under this program. Performances of these electrodes varied ill the range 2f 1.47 to 1.50 V at 355 K (180 F), 993 kPa (144 psia) and 161 mAl em (150 ASF);

6. Automatic operation of the 3-FPC, including system pressurization and depressurization, has been demonstra,ted.

7. Hardware and the subsystem teChnology have been demonstrated to be ready for demonstration at the preprototype level.

RECOMMENDATIONS

Based on the work completed, the follOWing recommendations are made:

1. Incorporate all the technology advances in static feed water elec­trolysis including cells, modules and SUbsystems into one, self­contained engineering prototype OGS.

2. Further advance the SFWE-based OGS teChnology by demonstrating methods fo·r KOH elimination from feed water compartments and for elimination of stray electrolysis in the coolant loop. Nodify the current cell design to strengthen the O2 exhaust port and to increase pressure differential capability.

3. Endurance test the engineering prototype OGS to further demonstrate the system te.chnology and the hardware maturity. Demunstrate cyclic operation under typical da'Tlnight time frames expected of a Habit­ability Nodule.

4. Further characterize performance of the super electrodes under various test conditions such as current density, temperature and pressure and over extended periods of time.

5. C0nduct parametric testing of the OGS to generate data needed to <>ptimize the OGS. This is particularly important because the OGS requires the greatest expenditu,re of power among the five subsystems of an ARS.

6. Characterize the 3-FPC, expand its operation over the range of ambient to 1,380 kPa (200 psia) and endurance test to ensure its availability fer future NASA needs.

68

Cif~ SI!$f~III$. !HC.

4. The WAB-6 super electrodes have been endurance-tested for more than 8,650 hours. Thoughout the endurance testing, the performance of the electrodes has been steady and no indication of degradation has been observed.

5. The performance of WAB-6 electrodes has been demonstrated to be reproducible. Twelve super electrodes have been fabricated and tested under this program. Performances of these electrodes varied ill the range 2f 1.47 to 1.50 V at 355 K (180 F), 993 kPa (144 psia) and 161 mAl em (150 ASF);

6. Automatic operation of the 3-FPC, including system pressurization and depressurization, has been demonstra,ted.

7. Hardware and the subsystem teChnology have been demonstrated to be ready for demonstration at the preprototype level.

RECOMMENDATIONS

Based on the work completed, the follOWing recommendations are made:

1. Incorporate all the technology advances in static feed water elec­trolysis including cells, modules and SUbsystems into one, self­contained engineering prototype OGS.

2. Further advance the SFWE-based OGS teChnology by demonstrating methods fo·r KOH elimination from feed water compartments and for elimination of stray electrolysis in the coolant loop. Nodify the current cell design to strengthen the O2 exhaust port and to increase pressure differential capability.

3. Endurance test the engineering prototype OGS to further demonstrate the system te.chnology and the hardware maturity. Demunstrate cyclic operation under typical da'Tlnight time frames expected of a Habit­ability Nodule.

4. Further characterize performance of the super electrodes under various test conditions such as current density, temperature and pressure and over extended periods of time.

5. C0nduct parametric testing of the OGS to generate data needed to <>ptimize the OGS. This is particularly important because the OGS requires the greatest expenditu,re of power among the five subsystems of an ARS.

6. Characterize the 3-FPC, expand its operation over the range of ambient to 1,380 kPa (200 psia) and endurance test to ensure its availability fer future NASA needs.

68

£ifc SVS/CHIS. lUt:.

REFERENCES

1. Ivynveen, R. A. and Schubert, F. H., "A Regenerable Fuel Cell System for ~lodula r Space Station Integrated Electrical Power," Paper No. 739055, Eighth Intersociety Energy Conversion Engineering Conference Proceedings, Philadelphia, PA; August, 1973.

2. Powell, J. D.; Schubert, F. H. and Jensen, F. C., "Static Feed Ivater Electrolysis ~lodule," Final Report, C0ntract NAS2-7470, CR-137577, Life Systems, Inc., Cleveland; OH, November, 1974.

3. Schubert, F. H.; Wynveen, R. A. and Jensen, F. C., "Development of an Advanced Static Feed Wa ter Electrolysis ~lodule," Paper No. 74-ENAs-30, Intersociety C0nference on Environmen,tal Systems, San Francisco, CA; July, 1975.

4. Schubert, F. H. and Wynveen, R. A., "Techn010gy Advancement of the Static Feed Water Electr0lysis Process," Final Report, Contract NAS2-8682, CR-152073, Life Systems, Inc., Cleveland, OH; November 1977.

5. Schubert, F. H., "Long-Term Operati0n of a Water Electrolysis M0dule," Paper No. 690643, Na tiona I Aeronautic and Space Manufacturing ~leeting, Los Angeles, CA; October, 1969.

6. Schubert, F. H., "Selection ",f Electrolytes fo,r Electrolysis Cells:

7.

Alkaline or Acid," Paper No. 70-Av/SpT-14, Space Technology and Heat Transfer Conference, Los Angeles, CA; June, 1970.

Schubert, F. H.; Lee, Electrolysis System: society Conference on

H. K.; Davenport, R. J. and Quattrone, P. D., "Water H2 and O

2 Generation," Paper No. 78-ENAs-3, Inter­

Envir0nmental Systems, San Francisco, CA; July, 1978.

8. Marshall, R. D.; Lee, ~1. K. and Schubert. F. H., "Evaluation of a Spacecraft Nitrogen Generator," Final Report, Contract NAS2-8732, CR-152097, Life Systems, Inc., Cleveland, OH; April, 1978.

9. Schubert, F. H.; Heppner, J'). B.; Ifallick, T. ~1. and Woods, R. R., "Technology Advancement of the Electrochemical CO2 Concentrating Pr0cess," Final Report, Contract NAS2-&666, CR-152250, Life Systems, Inc., Cleveland, OH; May, 1979.

10. Yang, P. Y.; Schubert, F. H.; Gy0rki, J. R. and Wynveen, R. A., "Advanced Instrumentation C0ncepts for Environmental Control Subsystems," Final Report, Contract NAS2-9251, CR-152100, Life Systems, Inc., Cleveland, OH; June, 1978.

11. Schubert, F. H.; I'larshall, R. D.; Hallick, T. H. and Woods, R. R., "One-Han Electrochemical Air Revitalization System Evaluation," Final Report, Contract NAS9-14658, Life Systems, Inc., Cleveland, OH; July, 1976.

12. Woods, R. R.; Schubert, F. If. and Hallick, T. H., "Electrochemical Air Revitalization System Optimization Investigation," Final Rep0rt, Contract NAS9-14301, Life Systems, Inc., Cleveland, Olf; Oct0ber, 1975.

69

£ifc SVS/CHIS. lUt:.

REFERENCES

1. Ivynveen, R. A. and Schubert, F. H., "A Regenerable Fuel Cell System for ~lodula r Space Station Integrated Electrical Power," Paper No. 739055, Eighth Intersociety Energy Conversion Engineering Conference Proceedings, Philadelphia, PA; August, 1973.

2. Powell, J. D.; Schubert, F. H. and Jensen, F. C., "Static Feed Ivater Electrolysis ~lodule," Final Report, C0ntract NAS2-7470, CR-137577, Life Systems, Inc., Cleveland; OH, November, 1974.

3. Schubert, F. H.; Wynveen, R. A. and Jensen, F. C., "Development of an Advanced Static Feed Wa ter Electrolysis ~lodule," Paper No. 74-ENAs-30, Intersociety C0nference on Environmen,tal Systems, San Francisco, CA; July, 1975.

4. Schubert, F. H. and Wynveen, R. A., "Techn010gy Advancement of the Static Feed Water Electr0lysis Process," Final Report, Contract NAS2-8682, CR-152073, Life Systems, Inc., Cleveland, OH; November 1977.

5. Schubert, F. H., "Long-Term Operati0n of a Water Electrolysis M0dule," Paper No. 690643, Na tiona I Aeronautic and Space Manufacturing ~leeting, Los Angeles, CA; October, 1969.

6. Schubert, F. H., "Selection ",f Electrolytes fo,r Electrolysis Cells:

7.

Alkaline or Acid," Paper No. 70-Av/SpT-14, Space Technology and Heat Transfer Conference, Los Angeles, CA; June, 1970.

Schubert, F. H.; Lee, Electrolysis System: society Conference on

H. K.; Davenport, R. J. and Quattrone, P. D., "Water H2 and O

2 Generation," Paper No. 78-ENAs-3, Inter­

Envir0nmental Systems, San Francisco, CA; July, 1978.

8. Marshall, R. D.; Lee, ~1. K. and Schubert. F. H., "Evaluation of a Spacecraft Nitrogen Generator," Final Report, Contract NAS2-8732, CR-152097, Life Systems, Inc., Cleveland, OH; April, 1978.

9. Schubert, F. H.; Heppner, J'). B.; Ifallick, T. ~1. and Woods, R. R., "Technology Advancement of the Electrochemical CO2 Concentrating Pr0cess," Final Report, Contract NAS2-&666, CR-152250, Life Systems, Inc., Cleveland, OH; May, 1979.

10. Yang, P. Y.; Schubert, F. H.; Gy0rki, J. R. and Wynveen, R. A., "Advanced Instrumentation C0ncepts for Environmental Control Subsystems," Final Report, Contract NAS2-9251, CR-152100, Life Systems, Inc., Cleveland, OH; June, 1978.

11. Schubert, F. H.; I'larshall, R. D.; Hallick, T. H. and Woods, R. R., "One-Han Electrochemical Air Revitalization System Evaluation," Final Report, Contract NAS9-14658, Life Systems, Inc., Cleveland, OH; July, 1976.

12. Woods, R. R.; Schubert, F. If. and Hallick, T. H., "Electrochemical Air Revitalization System Optimization Investigation," Final Rep0rt, Contract NAS9-14301, Life Systems, Inc., Cleveland, Olf; Oct0ber, 1975.

69

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APPENDIX 2 ARX-I OPERATING MODES DEFINITIONS

Shutdown Mode (B)

The ARX-I is not generating 02 or N2 and not removing CO2 or moisture from the air. The process air blower is off as is the water separator blower. The currents in the three modules are off, the system is com­pletely depressurized to atmospheric pressure and the Saba tier reactor and N2 generation modules are cold. The system is powered and all sen­sors are operating. The CHCS, EDCM and OGS temperature control loops are operating .. The shutdown mode is called for by any of 92 monitored para­meters exceeding tolerance, manual actuation or unsuccessful mode transi tion.

Normal Mode (A)

The ARX-I is generating 02 and N2 and removing CO2 and water vapor from the air. The CO2 removed from tfie air is reduced by the Sabatier reactor to water and metfiane. The excess water collected is delivered to an external water tank. The Normal Mode is called fo,r by !Danual actuation.

Standby Mode (E)

The ARX-I is operating essentially as it is in the Normal Mode with the exception that the EDCM and SFWE currents are zero, the process air blower and water separator blowers are off and the SFWEM pressure is maintained by N2 through the purge valves. The S'tandby Mode is called for by manual actuation.

Purge Mode (C)

The ARX-I is ~e~ng purged wi7h ex7ernal N2 through all H2 ~carrying lines, H2 module cav1t1es, 02-carrY1ug l1nes and 02 module cav1E1es. All module currents and blowers are off as are the Saba tier and N2 generator m0dule heaters. The system has N2 pressure in it. This is a continuous purge and will remain until a new mode is called f0,r. The Purge Mode is called for by manual actuati0n.

Unpowered Mode (D)

No electrical p0wer is supplied to the ARK-I CjM I. Thus, no electrical p0wer is applied to the ARX-I mechanicaljelectr0chemical hardware. The system is not operating however, there could be N2 , H2 0r 02 pressure in the system and there could be N2 flows through the system depending on h0w the unp0wered c0ndition was arrived at. The Unpowered Hode is called f0r by manual actuation (circuit breaker in TSA) or an electrical power failure.

A2-1

Cife S,IS/CIIIS. Ine.

APPENDIX 2 ARX-I OPERATING MODES DEFINITIONS

Shutdown Mode (B)

The ARX-I is not generating 02 or N2 and not removing CO2 or moisture from the air. The process air blower is off as is the water separator blower. The currents in the three modules are off, the system is com­pletely depressurized to atmospheric pressure and the Saba tier reactor and N2 generation modules are cold. The system is powered and all sen­sors are operating. The CHCS, EDCM and OGS temperature control loops are operating .. The shutdown mode is called for by any of 92 monitored para­meters exceeding tolerance, manual actuation or unsuccessful mode transi tion.

Normal Mode (A)

The ARX-I is generating 02 and N2 and removing CO2 and water vapor from the air. The CO2 removed from tfie air is reduced by the Sabatier reactor to water and metfiane. The excess water collected is delivered to an external water tank. The Normal Mode is called fo,r by !Danual actuation.

Standby Mode (E)

The ARX-I is operating essentially as it is in the Normal Mode with the exception that the EDCM and SFWE currents are zero, the process air blower and water separator blowers are off and the SFWEM pressure is maintained by N2 through the purge valves. The S'tandby Mode is called for by manual actuation.

Purge Mode (C)

The ARX-I is ~e~ng purged wi7h ex7ernal N2 through all H2 ~carrying lines, H2 module cav1t1es, 02-carrY1ug l1nes and 02 module cav1E1es. All module currents and blowers are off as are the Saba tier and N2 generator m0dule heaters. The system has N2 pressure in it. This is a continuous purge and will remain until a new mode is called f0,r. The Purge Mode is called for by manual actuati0n.

Unpowered Mode (D)

No electrical p0wer is supplied to the ARK-I CjM I. Thus, no electrical p0wer is applied to the ARX-I mechanicaljelectr0chemical hardware. The system is not operating however, there could be N2 , H2 0r 02 pressure in the system and there could be N2 flows through the system depending on h0w the unp0wered c0ndition was arrived at. The Unpowered Hode is called f0r by manual actuation (circuit breaker in TSA) or an electrical power failure.

A2-1