- NASA CONTRACTOR REPORT 177368

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:_ Test and Evaluate Passive 0rbttal Disconnect Struts (PODS-III)

•, R T. Parmley

:_: S.A. Katz

_- I. Spradley

,;L Lockheed Mtsstles& Space Company_;.. Research & Development Divislon_. Palo Alto, California 94304

.,, W.C. Henninger

_ ACR_:,.; San a Cruz, California 95061:

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.,_ Prepared forAmes Research Center

:.: Under Contract NAS2-11946

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.i:' !_IGUST1985

:, NatlonalAeronauticsandSpaceAdmmTstrat_on

,.: AmesResearchCentar,_- MoffettFoelcl,Cahf_rnla94035 i

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o,,. FOREWORD

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:,/. TMs york vas conductedfor the NattoM1 Aeronautics and SpaceAdstntstratton_'i (NASA)through the AmesResearchCenter, Hoffett Fteld, Cellfornta, Dr. Peter

' Ktttel, ProgramManager.'r

_:: T,e LockheedPalo Alto ResearchLaboratepj (LPARL)conductedthe program:i!_ vlthtn the CryogenicTechnologyGroupof the Themal Sclences Laboratory, vlth

__::- Applted ComputerResources, Inc. (ACRI) support. Key Individuals who

_ contributed to th|s program are:

.:,'_ • D. Bushnell - developedDEWARoptimization program°:;; • 14. C. Henntnger (ACRI) - predicted modal resonance

_. • S. A. Katz - performed modal resonance testtn9 and reduced data

!:?...... • 1. Spradley - performed..beneftt study

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:::; R.T. Parmle.y

":; Principal Investigator

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1986000807-TSA04

CONTENTS

•.. Sectton Page•w

FOREWORD t t t" ILLUSTIUtTIONS vt

TABLES vtt

............... 1. INTRODUCTIONANDSUNIARY 11.1 Introduction 1

: 1.2 Summary 22 PODS-III DESIGNCONCEPT 3

• 3 TASK1 - MODALVIBRATIONTESTS 7

3.1 Test Artlcle and Setup 73.2 Test Procedure 11

3.3 Test Results 113.4 Predlcted Results 17

4 TASK2 o BENEFITSTUDY 214.1 ReferenceTanks 21

4.2 Support Optimization 22

4.2.1 Support Optimization Program(DEWAR) 22

4.2.2 DEWARInputs andConstraints 26- 4.2.3 DEWARResults 28

4.3 Themal Analyses 284.3.1 THE_ 32

4.3.2 Themal Models 32

4.3.3 Results 36• ..;'*

5 CONCLUSIONSANDRECOH_NDATZONS 55

: 5.1 Task 1 - ModalVibration Tests 55

:: 5.2 Task 2 -Beneftt Study 56

6 REFERENCES 59

:: 7 APPENDIXA 61

;. 8 OISTRIBUTIONLIST 83

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-,["................r.RI_CI_D.ING,,pAG]_ B'bANK NOTMED ................. 1986000807-TSA05

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" ZLLUSTRATZONS

': Ftgure Page

o, 2-1 POOS-III Support Concept 4

:" 3-1 POOS-II! Support Strut Assembly 8i' "• 3.2 DewarSimulator With PODS-III Strut No. 6 Instrumented for: "- IqodalResonanceTests 10p -

"" 3-3 Strut Excitation 12_" 3-4 Acceleromter Locattons 12

_: 3.5 Hodal Test Results 15

/. 3.6 ModePhastn9 Comparison 16

, i:'. 3.7 • Strut Hodel With AccelerometersandClamp 18

) / 3-8 Strut I4odel Without Acceleromters 18

i!:_ 4-1 CryogenTank Characteristics 23)_ 4-2 Selection Crtterta for Orbtt TubeMaterial 27

_ ° 4-3 PODS-III Tank ThermalModel Without Vapor-CooledShtelds 33'" 4.4 SOTAStrut Tank Themal ModelWtthout Vapor-CooledShtelds 33

) _-:.. 4-5 PODS-III Tank Therml Hodel Wtth Vapor-CooledShtelds 34; :_" 4-6 SOTAStrut Tank ThermalModelWith Vapor-CooledShtelds 34

," 4.7 Ralattve Reduction th Tank Heat hate for the OTVLO2'_ Tank (PODSvs SOTAStruts) 43

4-8 Relattve Reduction in Tank Heat hate for the OTVLH2:: Tank (PODSvs SOTAStruts) 43

4.9 Relattve Reduction in Tank Hut hate for the SpaceStation_- LO2 Tank (PODSvs SOTAStruts) 44

4.10 Relative Reduction tn Tank Heat Rate for the SpaceStatton:; LH2 Tank (PODSvs SOTAStruts) 45

t'" 4-11 Relattve Raducttontn Strut Heat Leak for the SpaceStatton;_ Tanks (PODSvs SOTA) 46

_! i 4-12 LO2 Loss for VentedTanks 48

: 4-13 LH2 Loss for VentedTanks 49

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1986000807-TSA06

%LLUSTRAT%ONS(Cont.)

Ftg.re4-14 LO20TV Tank No-VentPressure Htstor_ 50

4-1S LH20TV Tank No-VentPressure H/stor_ 514-16 LO2 SSSTank No-VentPressure Htsto_ 52

4-17 LH2 SSSrank No-Vent Pressure Htstory 53

TABLES

Tab1___ee Page

3-1 Characteristics of PODS-I! Strut No. 6 9

3-2 LoadCasesTested 133-3 Hodal Test Results 14

3-4 Hodel Analysts Versus Test Results 194.1 ParametersUsedto Evaluate _he Supports 22

4-2 Tank LaunchMetghts 24

4-3 Factors Usedfor Calculattn9 Me_ghts 25

4.4 Dewar%nputsand Constraints 29

4-5 PODS-Z11Optimized Dimensions 30 +

4.6 HodeledSystemResistors 35

4-7 OTVHeat Rates, LO2 Tank (_) 374-8 OTVHeat Rates, LH2 Tank (mW) 38

4-9 SSSHmatRates, LO2 Tank (mW) 39

4-10 SSSHeat Rates, LH2 Tank (mM) 404-11 SS$Heat Rates, Vapor-CooledLO2 Tank (mW) 41

4-12 SSSHeat Rates, Vapor-CooledLH2 Tank (mW) 42

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1986000807-TSA07

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Sectton 1

INTRODUCTIONANDSUWeARY

: 1.1 INTRODUCTION

�ThePassive Orbttal Disconnect Strut (PODS) support system.s developed under

: contract NAS2-10848 (Refs. 1, 2, 3). Struts were analyzed, designed,

fabricated, and tested structurally and thermally. Tests on a stngle strut

11 tncluded thermal conductance to heitum temperature, thermal expansion data,loads to thermally short out the strut, ulttmate loads, evacuation rates, and

fattgue tests at 11quid-nitrogen temperature. Load tests on a set of stx

struts tncluded axtal and stee-load tests and the effect on strut shorttng of

simulated asj_nmetrtc temperatures of the vacuumshell.

The Task 1 modal resonance tests descrtbeO in thts report complete the test

:. series on the ;)ODS-II] version of the strut. The Task 2 benefit study in this

i.. report addresses use of PODS-IlI supports on Orbtt Transfer Vehtcle (OTV) andSpace Station (ms) l_qutd-oxygen and liquid-hydrogen tanks and compares

_:. PODS-Ill supports to ,. ,_Otsconnect strut supports.

:. The PODS-Ill support ts ready for use on fltght dewars or other support

• applications, A ne_ version of the strut (PODS-IV) wtth Improved resistance

: ..... to stde loads ts being developed on contract NAS2-11945, amendment1. The

_- PODS-IV support ts the current selection for supporting the 1580-1 superfluid

'.r. heltum tank on the 6ravtt¥ PrObe-S program. Other missions ,here the PODS

:_ supports ma_ be used tncluoe SIRTF, LDR, OTVs, Space Statton, and other NASA" and DoOmissions.

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1986000807-TSA08

l i_, The objectives of this programare: (1) to perfom mdal resonancetosttng ofthe POOS-III supports andcomparethe results to predicted values so that all

L__!, engineering data required for use on f11ght Systemsare available; and (2) to! o_:

!_,_ detomtne posstble perfomance improvementsas comparedto nondtsconnect_/! struts tn large ltqutd-oxygen/ltqutd-hydregen (LO2/LH2) tank spacei.

f_. uppltcsttons.

_ Task 1 - Hods1Vibration Tests

! Using the PODS-Ill supports and the dewar simulator developedunder contracti . NAS2-10848,a modal resonancesurvey is performedon the set of stx struts

_ii assmbled in the dewar simulator. Survey conditions stmulate launch and_*__ steulate orbital loadtngs of the struts. The orbttal 1sad range spansa full

i_il. to an empty tank. The frequencies surveyedcover the range consistent vlth_** SpaceTransport System (STS) qualtftcatt on requtrementsand the prtnctpal

...._ resonant modesof the strut system. The results of these tests are compared_- to predicted results basedon strut dtmonstonsand measuredmodulusvalues.

_:il Task 2 - Benefit Study

i _! The benefit of using PODS-XX!supportson OTVand SpaceStation LO2 and_:ii LH2 reference tanks is comparedto ustng present state-of-the-art (SOTA)

_ i i nondtsconnectstruts. Thesestudies are performed on four different LO2 and_'_ LH2 tanks (1) holdtng the launch resonanceat 35 Hz and varytng the orbit

° i resonancefrom 1 to 20 Hz, (2) analyzing both full and emptytanks at launch,

?( (3) varytng orbit boundarytemperatures from 150 to 250 K, (4) varying the

ii!I numberof struts from 6 to 12, (5) varytng orbit ttmes up to 5 years, and (6)using or not using vapor cooltng.

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1986000807-TSA09

&_tton 2

PODS-!11 OESI_;NCONCEPT

Figure 2-1 presents the PODS-IIZ support concept. A mtntmumof six struts

(three patrs) is required to support a cryogen tank. (Stx struts provide a

statically detemtnate support system t, all axes.) As the tank diameter

changes due to cooldown or pressurization, the angled pinned-end struts are

free to move in and out as the tank move_ up or downsltghtly a value of H. A

similar adjustment occurs automatically as the vacuumshell changes diameter t

in orbit due to temperature changes. !J

For purposes of installation, the warm end of the strut provides a length

adjustment feature. The threads on the rod-end fitting and length adjustment +

are a different pitch; consequenty, by rotating the adjustment hex, precise

length adjustments can be madeduring strut tnstallatfon without rotating the

strut. This feature allows length adjus1_nentsafter the vapor-cooled shieldsare attached to the struts.

The cold end of the strut providesthe passiveorbitaldisconnectfeature.

The cold rod end fitting/stem is connected to the body by a thin-_all

fiberglass or graphite/epoxy orbit tube and adjustment bushing. The contcal

stem load-bearing surfaces are separated from the nut (tension) and body

(compression) by an axial gap of -0.076 mm(0.003 in.) at eperattng +_

temperature. At ambient temperature, the gaps are set to take into accoun+ "

the differential shrinkage between the various parts. During one-g thermal

•- test or orbital flight, the conical surfaces do not touch. Consequently, heat

ts transferred from the body to the thin-wail orbit tube/stem/rod end fitting

subassembly by radiation and by conduction along the orbit tube.

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1986000807-TSA10

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7"llilll lili_llT Tl/li OIIIITAL IlIIPIWll _ IllffAIII

' "_" IS-CLASS IPOIIY| (GIMPHITI tTQIYI¢OLO llOD¥ Ill.All|

.._ DISCONNECT MICHAN IJ&l: DI/MNSIONS IN sm • *" •

•" J":.'.. GILAPHITE/I[IDOXY TUBE

1_ IS,,41q lIND ANGLE)' _ O.O_O

•,:2"

"_ ADJUSTMENT LAUNCH LOAO BEARINGFIBERGLASS/EPOXY SURFACE (0.0"/(_nm CAP)

_ PIR STRUT TUBE 12"lll-_eg WIND COMi'RESSION I

'" RIGHT: i.U _l_ ANGLE} lOAD BEARING•,.i." DESIGN lOAD.* p N SURFACE:,;. SHORTING WEIGHT: 1117kg IN 1-'o (I).O?i-mm GAP):. l St, 1 "

•'_'" VACUUM "'@

;" I EACH

•_'," SHELL

- SIDE"-,t •

,, Ftg. 2-1 PODS-III Support Concept

i_; During launch, the 9 load elastically deforms the orbit tube along tts axis;,:,} the contcal shoulder of the stem rests hard on the body (compression) or nut

ii)_ (tension). The load path bypasses the orbtt tube. The major thermal

:_ resistance and load path during launch is now the launch tube. Upon achieving

orbit, the conical shoulder of the stem passively disconnects from the body or

,,._ nut, and the major thermal resistance is again the thin-wall orbit tube.

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II

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- This design combinesthe desirable features of a thermal disconnect during

".--; groundhold andorbit with the high reliability of a comp'letelypasstve

_ design, Since the struts do not short out tn one-go the orbital performance

: of the struts can be demonstratedtn one-g thermal qualification tests and the

ground hold neat leak ts lower, These are both highly desirable features,

*:,- Oetatls of prior analyses, deslgn, fabrication, andstructural andthermali'.} test results ale provided tn Refs, 1, Z, and. 3,

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: Sectton 3w

:: TASK1 - MODALVIBRATIONTESTS

:.... 3.1 TESTARTICLENil) SETUP

: Ftgure 3-1 showsthe PODS-IlI test arttcle. Strut numberstx from Ref. 3 vms

tnstrment_d for thes.ete.sts. T!b.l..e..3-.1.p_vtd.es measuredcharacteristics of.. the strut.

•_ A dewarsimulator was destgnedso that simulated 9round hold, launch, or orbtt

- loads could be applted durtng th_ modal resonancetests. Thesetnclude

stmulatad loads from the wetght of the tank, heltum, vapor-cooled shtelds, andt Insulation.

,: The simulator was fabricated and tnstmlled tn a thr_e-post load machtneas

- shownIn Ftg. 3-2. A 56-kg (123.S-lb) triangular alumtnumplate and six

; adjustable clevis fttttngs stmulate the alumtnumtank attachments. Threealumtnumblocks are attached to the three load posts. Stx adjustable clevts

._ fttttngs attached to the blocks stmulate the vacuumshell attachments. The

stx struts are Installed as shownat a 55-deg angle fr_ the horizontal.7

..- • Axtal compressionor tenston hydraulic loads were applted at the geometric

center of the simulated tank through a load cell and large spherical beartng. ,1-; For sometests, the wetght of the stmulated tank was taken off the struts by- suspendingthe ietght from a ptnned clevts on the top center of the triangular

.i: alumtnumplate. All struts were electrically wtred using six ltght bulbs anda powersupply to tndtcate wheneach strut shorted under load.

" Trtaxtal accelerometers were mountedto a steel block whtch tn turn was

:_ mountedto a steel hoseclamp (Ftg. 3-21. The clampwas mountedon the

: PODS-III fiberglass tube at different locations durtng the tests. To ensurethat the clamp contributed no spurtous frequency responses, tt,'e trtaxtal

,_ _! ............ P.RECEDJNG PAGE BLANK NOT I_LM_D PAGE [,_ INIENTIONALLy

.... " ........ '.............................. " -" ,-;._ .............................._._...................... _..................... _........_ T,r

] 986000807-TSA13

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: Table 3-1 CHARACTER%ST]CSOF PODS.]|] STRUTNO. 6iiii

: Length, rod end to rod end centers: 0.5907 m 123.256 tn.)

Fiberglass Tube

e Unsupported Length: 0.422 m (16.60 in.)

e ]D: 0.02799 m 11.1018 tn.)

e OO: 0.02938 m (1.1566 tn.)

e Cross Sectional Area: 6.27 x 10.5 m2 10.0972 tn. z)

• Nodulus: 5.4 x 1010 N/m2 (7.8 x 106 pst)

Graphite Tube

e U_lsuppo_ea Length: 0.0417 m (1.64 tn.)

e ID: 0.01524 m (0.600 tn.)

OD: 0.01582 m 10.623 tn.)

• Cross Sectional Area: 1.45 x 10.5 m2 (0.0221 tn. 2)

• Noaulus: 10,8 x 1010 N/m2 (15.7 x 106 pst)

_etght (Ftg. 3-1)

Item No. ...9__0 Item No. ._L_

5 1 RoOEno, Cold 42.5 10 Clamshell, Large 21.0 (ea)2 aam Nut 3.6 11 Body, garm End 64.4

3 Stem 33.0 12 Length Adj. 39.74 Nut 60.0 13 aam Nut 21.7

5 Body, Cola End 148.3 14 _am Nut 3.6

6 AOJ. Bushtng 19.2 15 Rod End, _arm 42.5 14

7 Clamshell, Small 1.8 lea) 16 Spacer 0.1

8 Small Tube 1.1 17 Spacer 16.2!

: (Graphite) 18 Radiation Shteld 1.1 i, m I_

: 9 Large Tube 58.0 600.6,_ (Fiberglass) 1

• i

accelerometer block was also mounted dtrectly to the PODS-]]] end fttttngs 1: wtth beeswax tn a separate test. A comparison of the data showedthe clamp

had no e_fect on the freauency response of the str,t. Data were acqutred one

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1986000807-TSB01

analyzed uslng a GENItAl)2S15OynamlcData Analyzer and a 10adcell

tnstrmented Immarltap test technique.

3.2 TESTPROCEDURE

• The trtaxtal accelerometers weremountedto the hex_lm nut (Item 13,

Ftg. 3-1) wtth beeswax. The strut was tappedon the length adJustmnt (Item

12, Ftg. 3-1) with the load cell tnstrmented hammerwhtle different axtal

loads were applted to the struts (Fig. 3-3). The tratxtal acceleromter wasthen attached to the steel clamp, and the clamp was attached to the fiberglass

tubes tn one of six locations (Ft9. 3-4). Different loads were applted to the, struts (Table 3-2), and the strut shorting wasmonitored with the 11ght bulbs.

Eachof the etght modal tests was repeated stx ttmos with the tr.taxtalaccelerometers movedto the stx locations showntn Ftg. 3-4. Theexc|tatlon

was performedustng the load cell Instrumented hammer. The X-axts wasthe

axts of excitation. The potnt of hammertmpact was the hex face of the Jam*:" nut (Item 13, F_9. 3-1) below accelerometer locations 1 and 2.

Modaldata were analyzed on the GENRAD2515. Stnce the structure te,,Cedwas a

" stmple cylindrical shape, the computermodel usedto describe tts modal

dynamicswas a rectangle formedby the blsecttng Y-axts plane of the strutabout which the a¢celeromter locations were placed. Figure 3-4 (as-analyzed

diagram) describes the camputermodel. The accelerometer locations and axtalorientation of both the "as-tested" and the "as-analyzed" configurations are

. Identical.i °

3.3 TESTRESULTS,

The modal ana1:fsts revealed two _pes of fundamntal modes: columnbendingand strut torston. Zn a few cases a complexmodeconsisting of a combination

of both bendtngand torston was seen. The dynamtcmodesand ,issoctated

fundamontal frequencies and damptngcoefficients are smmartzed tn Table 3-3

" and plotted Jn Ftg. 3-5.,:.

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Table 3-2 LOADCASESTESTED

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Load LoadOn Stmulares:Direction: OnAll Stx Strut: GroundHold (GH)

Test C-Compression Struts Shorted-S Orbtt (0)No. T-Tension N (lbf) MonShorted-NS Launch(L)

," T I . '

::' 1 -- 0 I_ 0i | i iJ ill ill i ii i i

2 T 8,896 (2000) NS GH3 T 17,792 (4000) S L4 T 35,584 (8000) S L

i i ii i , ,,

5 C 549 (123.5) NS GH6 C 2,224 (500) NS GH

: 7 C 8,896 (2000) S L8 C 35,584 (8000) S L

In Ftg. 3-5, the lowest fundamentalfrequency ts plotted versus the square

root of the applted axial load. There appears to be a slight step changetnslope betweenthe shorted and nonshortedcases.

ModeshapeesttmtIons were performedtn reference to the center accelero:eter

locations (3 and4). All other locatton responsesw_.reIntegrated tnto the

mdal models. To develop a high degree of _oaftdence tn the computermedalrode1 esttmttons, admittance function phase data were examined.Accelerometer 1ocatt on sets (4. e., 1&2, 384, 5&6) were at the same

longitudinal locattofl on the strut but were rotated 180 deg. Consequently,- the clamp/,_cceleromter assembiywas merel_ rotated 180 deg to accommodatethe

: opposite set location. Thts dtd not effect Z-axts measurements;howeverX-

and Y-axts measurementsof oppostte locations were 180 degout of phase.

Ftgure 3-6 Illustrates thts. Theseare admittance functton plots of locations

3 and4 tn the X-axts (the upper plot ts locat/on 4 In the X- direction, the

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.... ......... .... " ..... " 1986000807-TSB05

; Table 3-3 NODALTESTRESULTS

Test No. Fundamntal Duptn9 Node- (Table 3-2) Freq, (Hz) Coeff. , _ , I)_sdcs:

:- 1 99.8 0.02183 Prtmry 8endtng222.6 0.01491 Prlmry llendtng -

2 142.4 0.02401 Prlmry Bendtn9/" 254.0 0.00756 Prtmry Bendtn9

483.3 0.00NO Prtmr_ Torsional

i- 3 174.8 0.03667 Prtmary 8endtng: 449.6 0.01062 Prtmary Bendtng

474.1 0.02748 Prtmary Torsional

4 194.9 0.01226 Prtmry Bendtng• 459.1 0.00706 Prteary aendtng

!; 462.2 0.00069 PrtmaryTorsional_ 482.2 0.03731 PrtmaryBendtng

- 5 125.2 0.01450 Prtmary Bendtng: 137.6 0.01782 Pr4ma_j Bending

423.6 0.02618 ComplexBendtng/Tors|onal* 464.1 O.00869 ComplexBend1ng/Torstonal

- 6 111.9 0.01352 Prtmary Bendtng!- 120.4 0.04342 Prtmary Bending . .

- 222.1 0.09968 Complex8endtrig/Torsional: i:.--

:_ 7 132.9 0.09755 Pr4mary8en41n9148.9 0.00612 Prtmary Bendtng

- 428.0 0.03669 Prtmry Torsional

: 8 124.6 0.01602 Prtea_ Bendtng137.3 0.01117 Primary Bending

,: 422.9 0.03585 Prtmrj Torsional',' I n

; Cautionary Note: Ourtn9 tests 1 and S, the strut tended to" "rattle" on tts mountingswhendynamically exctted, so thei-' associated data contain someuncertainty.

,_ n :

_. lower plot ts locatton 3 tn the X+ direction). Comparingthe phaseangles

:' (accelerometer direction) at the ctrcled fundamentalfrequencies reveals thataccelermeters are 180 deg out of phase. Since the accelerometersare

physically 180 degout of phase, simultaneousmotion of the two accelerometers

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............. 1986C)C)C)8C)7-TSBC)6

;-%

N LEGENDn :",

)- 0 TENSION-o:- U 1::3COMPRESSION

.,2.• z,u / STRUT SHORTED

. i,! u_

" J 200 _ (_

':. Z

':: :8 1:3.*.,r < 1001- Q

= :': Z' "r"

'e- 11_

_;. v) o I I I I I" _ 0 5g_ 2224 8896 17792 3558g N

.::i" _ I I I I I Io

: 0 (1241 (500) (2000) (;0001 (80001 (Ibf)

'.., TOTAL AXIAL LOAD, ALL SIX STRUTS

,." Ftg. 3-5 ModalTest Results

°;; tn the samedirection ts Indicated, and the associated modets bendtng.

,:" Conversely, tf the phase angles are the same, simultaneous oppostte motton

_ occurs, Indicating a torsional mode..,~

:;- Aamtttance functions tn the _- an# Z-axes were also examtnedto determine any

:: off-axts fundamental mo_es. No suchmodeswere found. Ap_endtxA presents ...........

. aamtttance..functtons for all of the stattc loa0tngs at locations 3X+, 4X-,:" 5X+, 3_ ”�and3Z-

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1986000807-TSB07

,.)RiGINAL.I::'t_,Gb;I1_• OF POOR QUAU'I'¥

i:"*. 3.4 PREDICTEDTESTRESULTS-.

•_' 3.4.1 ModelUsed

i_--:2 Finite element analysis (FEA) modelsof the PODS-Ill test article were i

;o: developedusing Lockheed'sASTROcomputerprogram(lef. 9). Intttal analyses t': for all preload cases tested revealed that the strut's fundamentalmodedid_,. not include any participation of the S6-kg (123.5-1b) triangular plate; hence, (

:_:: for the analyses reported herein, the FEAmodelsrepresent a stngle PODS-Ill_/7 I

" strut.

_ ;';:. Twoversions of the strut model were developed. The first version, depicted i'_L;, tn Fig. 3-7, simulates the strut's test configuration by Incorporating the i_: lumpedweight of the trtaxtal accelerometer assembl_(17.5 g) and the hose I

_-. t

i':- clamp (27.4 g). Since the accelerometer/clamp-assemblyweight equaled i

/i2" 85 percent of the fiberglass tube's unsupportedweight, it wasnecessary to

_- ado this weight to obtain frequency results that comparewith the test data,:? As tn the tests, the location of the accelerometer/clamp assemblywasvaried._" The averageOfrequency results determine the strut's fundamental frequency for

:; each preloao case. The secondversion, depicted tn Fig. 3-8, simulates the:!_" strut's as-butlt configuration.:i_°

_::'* The strut FEAmodels consisted of eight beamelements as showntn Ftgs. 3-7<r/::_ and 3-8. Thecenter four elements represent the strut*s unsupported

i .... fiberglass tube length wtth properties as summarizedtn Table 3-1. The end....: beamelement was employedto simulate the orbtt and ground-hold (opengap) and

< launch (closed gap) configurations. Rigid elements usedto offset the:* accelerometer andclampwetghts are showntn Fig. 3-7. The weight of the

i_ ?i;"

i_ fiberglass tube wasevenly distributed over the five Intermediate nodesand

i :. other strut-end item weights (Table 3-1) were lumpedat the tube's end nodes,! y wtth half the weight lumpedto ground.

_.',

:::; As noted, the model's end beamelementwas used to simulate orbtt and launch:_ models. The orbit model, due to Its Increased flexibility, was tuned by

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1986000807-TSB09

CLAMP

l /WEIGHT,__/___o.oo,.--,_X

TUBE O.0 iS mINVAR /ROD END

_t_.CCELEROMETER

Z /WEIGHT

T / r°""°X ,, t 'X _ , - X

/

Ftg. 3-7 Strut Hooel _ttth Accelerometers and Clamp

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

Ftg. 3-8 StPut Model _tthout Accelerometer

. 18

1986000807-TSB10

f L '

"*,

e_usttn9 the end beam'sstiffness to agreevith results of Test 2 andthenanalyzedfor the other relevant preloadconditions. Thelaunchrode1endr

: memberstare simulated by rlgtd beamelemnts to reflect the edd4ttonalL

stiffness of the strut while tn thts configuration.

3.4.2 Predicted Versus Test ResultsT

_i" Thegoal of the analysessumurtzedheretnm to define andanalyzeananalytical model and to compare the model*s fundmentel frequency _th that

_ obtatned exper/mentally. Table 3-4 sunmrdzes the analyses performed for the

test and as-bu|lt FEAmodels. Xn general, the launch model test configuration

: frequencies compare very well with test results for all cases except Test 8.

_ Orbtt and ground-hold model test simulation results demonstrate frequencies

, substantially htgher than detemtned by test, except for Test 2 for whtch the

analytical model was tuned. As-butlt simulation-model frequencies are

consistently htgher due to removal of the accelerometer/clamp lumped tmtght.+-

_ Table 3-4 MODELANALYSISVERSUSTEST RESULTS

-, Test As-Butlto Stmulart on Stmulatton

Test Test (Wtth (kftthout Hodel

No. Results Accelerometers) Accelerometers) Configuration; /" {

:_. 1 99.8 130.1 142.5 Orblt_ 2 142.4 141.1 154.4 Ground HOld

_ 3 174.8 172.6 192.3 Launch_ 4 194.9 193.5 215.4 Launch; S 125.2 129.4 141.7 Ground Hold

6 111.9 126.3 138.3 Ground Hold:- 7 132.9 134.8 1SO.2 Launch__ 8 124. S 79.4 88.5 Launch

_...

; 19._"

.'_=- ...... ,,- ..............., ............................ ................. , ...... _, . _,_._ : ,=............... ,........ _ ,. ....._......

1986000807-TSB11

4652w

m

,_ Sectton 4

•:; TASK2 - BENEFITSTUDY

_ To determine the benefit of using PODS-Ill supports, reference LO_ and LH2:" tanks were established (Ref. 7) for both an OTVmission of 1 month or less and

z space station storage (SSS) tanks wtth storage times of up to 5 years. The

PODS-III supports were comparedwith state-of-the-art (SOTA) fiberglass'_,

: struts. An alternate SOTAsupport, tmston bands, ts heavier for supporting

suc, large tanks due. to the large structures required to react the tension

:_; loads. For smaller tanks, the vacuumshell reacts the support loads. For%,,

these large tanks, vacuumshells are too heavy. PODSand SOTAstruts were

optimized using the DEIdARoptimization program for full tanks at STS launch,

" empty tanks at STS launch, 35-Hz launch resonance, and 1- to 20-Hz orbit_r resonances.

-:_ Four thermal models were set up for bo_h PODSand SOTAsupports with and

_ without vapor cooling. These models Included the supports,multtlayer

" Insulation (NLI), vapoP-cOoled shtelds where applicable, and fill and vent

,r lines. The optimized dimensions of the supports for the different cases were

:: Input tnto the thermal models and run for hot boundary temperatures of 150,

' 200, and 250 K, vapor cooling or no vapor cooling for the SSS tanks and no

:. vapor cooling for the OTV tanks, and storage times up to 1 month for the OTV:%

tanks and 5 years for the SSS tanks. These total heat loads to the tanks were

- then used as the basis for the support evaluation and recommendations.

Table 4-1 summarizes the parameters that were used tn the study.j'. ....

f; 4.1 REFERENCETANKS

•":. The reference 2219 aluminum LO2 and LH2 tanks used tn the study are shown;' tn Ftg. 4-1. The support-structure dimensions and tank dimensions were held

constant and the strut angles .vere allowed to optimize. The MLI is double

aluminized mylar/silk net wtth a degradation factor of 1.5. The tanks have

.:

'_ 21

•" PRECEDING PAGE BLANK NOT. I_ILMED INT[NTII)IMLL[lll311tt

1986000807-TSB12

Table 4-1 PARAMETERSUSEOTO EVALUATETHF SUPPORTS

I i II

..Co.ndtttons Evaluated OTV Tanks SSS Tonk,sII

Ntntmum launch Resonance 35 Hz 35 Hz

M4ntmumOrbit Resonance 5 to 20 Hz 1 to 20 Hz

Znittal Launch Condition FulllEmpty Full/Empty

Hot Boundary Temperature Range 150 to 250 K 150 to 250 KStruts 6-12 6-12

Orbtt Times Up to 1 month Up to 5 years

Vapor-Cooled Shtelds Without With/Withoutell

tttantum fill and vent lines with approximately one-half the conductivity of

stainless steel, alumtnum vapor-cooled shields (SSS tanks only where

applicable), and purge bag plus plumbtng componentstf launched wtth cryogen.

A summaryof the launch weights for both full and empty tanks is provtded in

Table 4-2. The weights were calculated using the factors shown tn Table 4-3.

The SSS LO2 tank is only partially loaded tn the "full" column due to STSlaunch constraints of -28,000 kg (62,000 lb). These weights are used tn the

DEWARoptimization program to size the supports.

4.2 SUPPORTOPTZHIZATION

4.2.1 Support Optimization Program (DEWAR)

The objective of this support thermallstructural optimization program is tomtntmtze the flow of heat from the outer structure to which the struts are

attached. Zn addition, enough structural rtgldity mu_t be maintained to keep

the lowest frequencies at launch and durtng orbttal conditions above certain

specified values, and stresses due to assembly and launch loads must be kept

below those that would cause buckltng or matertal failUre.

In the analysts, the outer structure and the tank to whtch tt is attached are

assumedto be _tgtd, and the supports are assumedto be massless. For more

- detatled calculations, the rtgtdtty of the structure and tank and support mass

22

....................................................................................................................1986000807-TSB13

J

ii,

i 12.3

i_ I1.7

• ' SSS TANKS

i! 7711.2 kg 117,000 Ib)

,! 11o.2m3 13.o ft31, _. LH 2

/, 7

S.7OUTSIDEENVELOPE

116720kg (103o000 Ib)

_0.9 m$ (l_q) tt 3)_o3

LOll

6.25.6

OTV TANKS

3220.6 kg (7,100 |b)

_6.0 m3 (1(;25 ft3) II LH2

: 19459. q kg (_2,900 Ib)

*_ 17.0 m3 (601 ft 3)

., (DIMENSIONS IN METERS)

Fig.4-1 CryogenTankCharacteristics

" 23,r

1986000807-TSB14

24

1986000807-TSC01

41:'-

i:i:.

,-@.',;

_- Table 4-3 FACTORSUSEDTO CALCULATEWEZGHTS)/-

:)::!. Item L02 L"2

i: Tanks 0.0_ 0.21_nk

_,. Ml.Ii .... p- 30.8 kglm3 1.8 cm (OTV) (Ref. 81 5.1 cm (OTV) (Ref. 81i:.- (1.g2 lblft3) 3.8 cm (SSS) (Ref. 71 1Z.7 cm (SSS) (Ref. 71

i_" (Thicknesses set based on studyresults of other programs.)

_: Vapor-Cooled Shields 0.98 kglm2 (0.20 lb/ft 2) 0.98 kg/m2 (0.20 lblft 2)

_" Plumbing 68 kg (150 lb) 91 kg (200 lb)

_._, Purge Bag 0.5 kg/m2 (O.1 lblft 2) 0.5 kglm2 (0.1 lblft 2)

_,-ii" Pur9e Pl_btn 9 High-pressure GN2 bottle High-pressure GHe bottle_; sized for 5 volume sized for 5 volume

i_. changes plus plumbtng changes plus plumbtng"T ,.

:_.: should be accounted for. It is also assumedthat the vapor-cooled shtelds and

i_i_ Insulation are rigid, supported by elastic struts which carry loads only along

!C their axes (pinned ends).

i_-

_=-:= In the PODSconcept, the effective axfal stiffness (EA/L)eff and heat flow

T conductance (KAIL)ef f change abruptly from the launch condition to the:; orbttal conditions due to a "disconnect" feature wtthtn each strut, so the

,- design of each of these support systems tnvolves solvtng of two optimization

problems, one corresponding '_o the launch phase and the other corresponding to_ ,.'-

_:. the orbttal phase, The SOTAsupport strut tnvolves solvtng one optimization

, problem corresponding to the launch condition only, since the nature of thts

.:: support system does not change for the orbttal phase and the launch phase

represents the more severe environment.

The program Inputs tnclude: (1) weights and dimensions of the Insulated

tanks, (2) quaststattc and dynamtc acceleration g-factors, (3) launch and

- 25

W..........................................................._::_,_-_-: _ .: ..... _:_._ ii, i:_::_-_ ilL!-:_--:_!:_:I:LI_/!:_-!_:!! _' - :__: . i i "- ., ' : • .............. - .........: ii :' _'_:'_,::':::_:'_'_....

988000807-T$002

orbttal frequency constraints, (4) Young's modulus and the maxtmumal3owable

stress of the fiberglass or graphtte tubes, and (5) themal conductivity of

the tubes. Program outputs include: (1) center of 9ravtty locations and

polar and ttlttng momentsof tnertta of the supported tanks; (2) destgn

margtns at launch of maxtmumstress, tube column (Euler) buckling, and tube

shell (local) buckling; (3) strut length and diameter, strut spactng and

angles, and cross-sectional area and wall thickness of the launch tube; (4)

launch and orbital frequency margtns tn lateral, t_l_, axtal, and torsional

modes; and (5) the axial length and cross-sectional area of the orbtt tube for

the PODSsupport.

Optimization is carrie _ out by a nonlinear programming algorithm called CONMIN

(Refs. 4,b). Thts program, wrttten by Vanderplaats tn the early 1970s, ts

based on a nonlinear constrained search algorithm due to ZoutendtJk (Ref. 6).

The bastc ana13_tc technique used tn CONHZNis to mtnlmtze an objective

functton (e.g., heat flow) unttl one orate constraints, tn thts case

vibration frequencies, buckling loads, maxtmumstress or stratn, and upper and

lower bounds on design variables, becomeacttve. The minimization process

then continues by following the constraint boundaries tn destgn vartable space

tn a direction such that thevalue of the o_ecttve functton continues to

decrease. Whena potnt ts reached such that no further decrease tn the

objective functton ts obtained, the process ts terminated.

4.2.2 DEWARInputs and Constraints

Figure 4-2 provides crtterta for selecting the appropriate composite for the

PODS-ZZZ"orbit" tube on the LH2 tank. Both thermal conductivity (k) and" modulus (E) values affect the chotce. The lower the k and the htgher the [

(|owest k/[ ratto), the more desirable the chotce. The modulus affects the

sprtng rate (K) and consequently the resonance value (_) of the supports

(lla_K) plus the column buckltng and local crippling strength. Zf constraints

such as mtntmumwall gage are encountered durtng the optimization procedure,

the modulus value cannot be used to full advantage.

26

1986000807-TSC03

.+ +

i

,. _;

_.'* 2.1)

,., tc. . X: 1.8

: 1.i SILEOT RUN DIIIAR

." OPTIMIZATION /_H y)_

"- 1.I EPOXY PROGRAM:'_ GI.ASSI FOR BOTH _ (GI.A&SIEPOX,..,' COMPOSITES .

i!- 1.3 EPOXY H:?

i Tc .2 1.2\iC EPOXY)/;,+T:+ 1.1 1.1

GRAPHITE/ 1,0 1.0.!, EPOXY

*: 0.S O.S

-_; 0.8 0.8 • •. j, 20 30 qO S0 14) 70_*_ WARM END TEMPERATURE OF ORBIT TUBE (K)

i '.%

+2: Fig. 4-2 Selection Criteria for Orbit Tube Composite!.-:.o

i::::," Whenthe orbit tube warm-end temperature is below 27 K, the integrated thermal

'_:+_ conductivity and klE values of graphite/epoxy are below that of glass/epoxy

,-+ (Fig. 4-2). Between27 K and61.5 K, the integrated klE ratio of

_.-:. graphite/epoxy ts below that of glasslepox¥ but not the k value.e *" .'"

:"_ Consequently, in this range the DEWARoptimization program must be run wtth

i + both compositesbefore a choice can be made.

!'.Ti**if Above61.5 K, glass/epoxy is the optimumchoice in all cases for' the orbit

i i tube on the LH2 tank due to the lower k and k/E ratio. The optimum choicefor the PODS-I|I launch tube on the LH2 tank and the launch or orbit tubes

':::,, for the LO2 tank ts fiberglass/epoxy due to the higher temperature ranges,:_ (90 K and higher) and higher graphite/epoxy conductivity.

+_ For all analyses in this section, fiberglass/epoxy tubes were assumedfor both

__: cryogens and the launch or orbit tubes. (The minimumwall gage constraint was

27

t

:_ exercised 12 out of 18 _Jmes for the LH2 orbit tube as showntn Table 4-5.): If additional analyses were run on both composites tn the 27- to 61.5-K range

for the LH2 tank, a graphite/epoxy orbit tube for the LH2 tank may be" optimum for someof the cases shown, providing additional perfomance

,_" tmrovement of the PODS-.Ill support over the $OTAstrut.

i: Table 4-4 presents tnputs and cOnstraints to the DEMARprogram. The tank

i:; "density# values were calculated from the tank dimensions (Fig. 4-1) and tank

: we|ghts (Table 4-2) The modulus value used was measured tn Ref. 3. The

L: maximumallowable stress ts 22 percent of ulttmate to allow for 105 fatigue

_i load cycles (Ref. 3, Fig. 2-6). The axial and lateral g loads were assumedto

be equal for these calculations and are the sumof the STS quaststattc

; Ws-0.5372):_" (3.17 g) and dynamic (9 - 204.5 x accelerations where Wsts the

supported wetght tn kilograms (Ref. 3, Ftg. 6-4).

:: The minimum launch resonance was taken from Ref. 1. The orbit resonances were

} varied over a broad range to detemtne their Impact on PODS-III performance._; Ntnimum wall thicknesses were set based on manufacturing limitations. The

i_ outer diameter of the orbit tube ts always smaller than the inner diameter of: the launch tube due to the destgn of the PODS-III support.

.

'; 4.2.3 DEWARResultsr

!v

Table 4-5 summarizes the DEWARoptimization results for the PODS-III

_ supports. The SOTAstrut dimensions were assumedto be the same as those of

the PODS-[I| support (excluding the orbit tube).

4.3 THERHALANALYSES

Finite-element thermal models were developed using THERHand the reference

:- tank data from Section 4.1 and the optimized support data from Section 4.2.

The resulting heat rate data allowed a comparison between PODS-III supports

i and SOTAstruts for a variety of different cases.

:: 28

,k

] 986000807-T$C05

17

"'_ ORIGII_IAL F;',_;. _.

'i!t _ POOR QUALi'i"lt

• i

• ,.._ _qo, _":* ,,r

• _ _._ _ ._

" if!Ii i i

"1

29

1986000807-TSC06

1986000807-TSC08

/,%"

o

_ 4.3.1 THERN

m

- Dora11 destgn analyses are done wtth THERM,the Lockheed themal analyzer

;'* computer program, on the UNZVAC1110 computer, l_e configuration ts

:; arbttrar|ly dtvtded tnto nodes by the designer, and THEM uses a ftntte-

• difference solutton for the three-<ltmenstonal heat transfer equatton at each

node. Programs wtth well over 1000 nodes have been run wtth no difficulty.

J:. Steady state occurs when the largest temperature difference of any node

between consecutive _,terattons Is less than a value specified In the program.

. Subroutines for THERNcan be perfomed at many places tn the calculation. Two

: examples are: (1) at each Iteration, the temperature-dependent properties can_:_ be recalculated and (2) heat mapscan be obtatned for different nodes.

T

.: 4.3.2 Thermal Models

! Four finite-element thermal models were developed for the following cases.

;_. Vapor,. Support Cryogen Cooled Fig. No.

:: PODS-IZZ L02 or LH2 No 4-3i.: SOTAStrut LO2 or LH2 No 4-4

: PODS-I]I LO2 or LH2 Yes 4-5:. SOTAStrut LO2 or LH2 Yes 4-6

Table 4-6 provtdes the modeled system resistors. Areas for the IVLI were

- calculated from data tn Ftg. 4-1, and NLI thicknesses were taken from Table

:; 4-2. An NLZ degradation factor of 1.5 was used tn the conductivity algorithms°i (Ref. 1). The optimized PODS-]Z] and SOTAsupport dimensions were taken from

; Table 4-5. Table 4-6 presents the ftll and vent 11ne characteristics.,r

,._

: The vapor-cooled modeltng used the cathode follower method. The method

:: determines the amountof heal [Q. _Cp(TH - TC)] a flutd can ptck up as-. It flows from node to node. Stnk nodes are used to remove the heat from the

: model. The struts and vent 11ne were thermally grounded to all three i

:i_ vapor-cooled shtelds. The ftll ltne was grounded to only the tnner shteld, t

!t t32=

1986000807-TSC09

' w

34

1986000807-TSC 11

i '7

Table 4-6 HODELEDSYSTEMRES]STORS

' SystemComponents Resistors Ptiterttll

: POBS.-III

" Rod End, Ham 1 lnconel 710

"_ Length Adjustment 1 Inver

. :_ Body, Harm 1 Invar

,_ Bondktne 1 Epoxy;

•- Large Outer Tube 2-5 S-Slass/Epoxy• BondLtne 6 Epoxyw-

_.. Ikxly, Cold 6 Invar

: " Adjustment Bushing 5 ]nvar

" BondLtne 6 Epoxy

• : Sm11 ZnnerTube 7 S-GlesslEpox_y

Ik)ndL4ne 8 Epoxy-;" Stem 8 lnvar: ,

' Rod End, Cold 8 [nconel 718

" g" - "" SOTA- Sameas aboveexcept for the follo_tn :

: BondLine 6 Epoxy" r

Body, Cold 6 InvarStem 7 Invar

Rod End, Cold .... 7 Inconel 718i ILI 30-33 DANISIIk Net, am ii • i

'_ Ftll Tube 2.54 an diam. x 0.051 cmx 61 an 40-41 Titanium 6 A1 4V

. (1.0 tn. diam. x 0.020 in. x 24 in.)J II

Vent Tube 1.27 an diam. x 0.0254 cmx 101.6 cm So-53 Titanium 5 A1 4V

(,0.5In. diam.x 0.010In. x 40 in.) i ii

; Vapor-Cooled Shiel ds 60-62 5061 A1umtnum

'!7

°,

4.3.3 Results

The following tables provtde a breakdownof the calcul,;ted haat rates as a

functton of wam boundary temperature, orbtt resonance, and full or emtytanks at launch.

Table No. T..an._k VaporCooled

4-7 OTV- LOZ No

4-8 OTV- LH2 No

4-9 SSS- LO2 No

4-10 SSS- LH2 No

4-11 SSS- LO2 Yes

4-12 SSS- LH2 Yes

From these tables, the ratio of the total heat rate for PODSsupported SSS

tanks to SOTAstrut supported tanks ts plotted versus the warmboundary

temperature, full or empty tanks at launch, and orbtt resonance (Figs. 4-7

through 4-10). The Inverse of thts ratio ts also plotted for the struts-only

heat leak tn Ftg. 4-11.

The following trends appear tn the data: (1) the _.l heat rate ts dominant;

(2) lower orbit resonance values (smaller AlL ratios) and lower warm boundary

temperatures (where _1 heat rate decreases faster than support heat rates)

Improve the PODS-]Z! supported tank thermal performance versus SOTAstruts;

(4) non-vapor-oooled PODS-IX! support tanks show greater relattve performance

gatn over SOTAstruts than when the struts are vapor cooled; and (5) launching

tanks empty provides the smallest relative gatn tn POOS-][Z tank performance

Improvement over SOTAstruts.

The empty tanks are ftlled tn orbit from a supply tank; consequently,

additional cryogen ts required for cooltng downthe warm tank. A second

launch may be requtred to bring up the extra cryogen, and a supply dewar ts

required.

36 ]

1986000807-T$C13

37 JL

1986000807-TSC14

!i _- _ _

!

. 38

1986000807-TSD01

: A

i

ii | i

i i "

i:

i-

! 39

1986000807-TSD02

40 :.I

1986000807-TSD03

1986000807-TSD04

' 1986000807-TSD05

/ .o.so..,T^LR.ONA.Ceosmuts I1,0_. , --20 _ I;.ESIGNED I

_- - _- ( FOR EMPTY I/ "s.l=.slT^NK I| '" ^T LAUNC"I

_oo.sl- 20 '/ _ _sT,,uTs I! _ • ! DESIGNEDI

2:2 , , I150 200 250

TH(K)

Fig, 4-7 Relative Recluction tn Tank Heat Rate for the 0TV L02 Tank(PODS Versus SOTA Struts)

0.6150 200 250

TH(K)

Fig. 4-8 Relat'ive Reduction 'in Tank Heat Rate for the 0TV LH2 Tank(PODS Versus SOTA Struts)

43

q4

1986000807-TSD07

q

:_' I STRUTS DESIGNED FOR EMPTY

?,- PODS ORBITAL/:. Z I. 01-.-- RESONANCE_:: _- / :o JVAPOR-:: _ 1 ,lOJ COOLED

::,: ..... m_l.'( _ _.-- _... -_ 20 INON

_i_; C_' _"__- _....__.,,,--__-- " ICOOLED

i"_ 0.8 I I?,_ 150 200 250

_:"_ T H (K)

,7

_!: 1.0 .S'I'RUT_; DESIGNED FOR FULLZ_':" I'TANI(-AT- _U-Nc-H ....... PODS ORBITAL !

0.,I- ,° Iv^,o -I: _ ---- ": Jc°°u_°l

_ NON/? z,::.. _ ,_,_ _ _" 'VAI_R-,::: _,_ _ 10 COOLED:.'. VII '( 0.7-- _ _ _ I

o,. O.6 _ _

:_-.. o.s I I.; so 2oo 25o;e

., THIK )

7

Ftg. 4-10 Relattve Reduction tn TankHeat Rate for the SpaceStatton_!_ LH2 Tank (PODSVersusSOTAStruts)

: 45

: :T" :.................... .......................................................................................................

1986000807-TSD08

,°llIiOI | LEGEND

LH2

LO2 ,---- ,,--

?0L_j E - STRUTS DESIGNED TO SUPPORT ..

Ft EMPTY TANK AT LAUNCH

! _ F - STRUTS DESIGNED TO SUPPORTFULL TANK AT LAUNCH

$0 VC - VAPOR-COOLED STRUTS- |0

F,VCI-

I-(/)

(/1

0<I-0_ 3O

0

20E,VC

E

10

00 10 20

SUPPORT ORBITAL RESONANCE (Hz)

Fig. 4-11 Ratio of Strut Heat Rate for the Space StationTanks (PODSVersus SOTAStruts)

' 46

_J

1986000807-TSD09

The support heat rates can be kept equal between _he PODS-Ill supports(designed for 35 Hz during launch wtth a full tank) and the SOTAstruts

:_ (designed for 35 Hz during launch with an enlpt_ tank) b_ lowerlng the PODS-Ill

; orbital resonances to the following values.

|,

i_ Full Tank Full Tank_, PODS-III Orbital SOTAStru_ Orbital:; Resonance, Hz Resonancet Hz

i ! Vapor (Designed for Full (Designed for Emptyi!_ Tank Cooled , Tank at Launch_,, , Tank ,at LaunchI_ OTV-L02 No 4 4 ......

" OTV-LH2 No 15 16:: SSS-L02 No 3 6-:_ SSS-L02 Yes 8 6': SSS-LH2 No 15 16i: SSS-LH2 Yes 23 18

_ The orbital resonances for the SOTAstruts and PODS-IlI are comparable.

"! However, the PODS-III strut-supported tanks can be launched full or empty,

- with potentially lower launch costs (1 versus 2 launches). For the OTVLO2: tank, orbit resonances of 4 to 8 Hz would probably not be acceptable during

_i orbital engtne ftrtngs. The LO2 PODSsupports with low orbital resonances::i would short and drive the strut resonance higher to "launch values" durt_g..?

_! orbital engine firings. The difference in fabrication costs between PODS-II1:._ supports and SOTAstruts is insignificant compared to the total costs of a

,. cryogen system (Ref. 2).

• The calculated heat rates were translated into cryogen left for vented systems

)_ (Figs. 4-12, 4-13) and pressure rise versus time for nonvented systems

_!. (Figs. 4-14 through 4-17). An orbital resonance of 20 Hz was arbitrarily

li. selected for the OTV tanks due to the higher orbital accelerations they!l experience. A lower ZO-Hz orbttal resonance was arbitrarily selected for theI SSS tanks due to minimal accelerations they experience in orbit.

47,e

1986000807-TSD10

Ftg. 4-12 LO2 Loss for Vented Tanks

48

NO BOIL-OFF1.00

', MONTH

_DS FULL AND EMPTY

"_ SSSS YEARS

0.90 WITH 'VAPOR-COOLED

_ SHIELDS -

_z o.80 _ _

E 0.70

STRUTS SIZED FOR SSSi INITIAL lAUNCH

CONDITION OF: S YEARSPODS-ill

FULL _ "_

EMPTY _r----- -IV

0.6o SOTA ..FULL v --

i_MPTY0" .... "4)

PODS ORBITAL FREQUENCY • 20 Hz (OTV)- t0 Hz (SSS) ,

: i o.so , I , I'" , 150 200 2S0

HOT BOUNDARY TEMPERATURE (K)

Ftg. 4-13 LH2 Loss fop Vented Tanks

49

t

,J" _:

1986000807-TSD12

r

i -i n _*

Iif'

; SUPPORT __ 1700 - T.. T,, • S0.2 K-i _ n

i: 1800 -TH:2S0 K TH" 200 K TH s IS0 K t_' -- MAXIMUM

J / PRESSURE:! 1SO0 / -(30 psla):[ / ....

" 1_oo / /

,j //

.] 13ooI

J• I

4 _W 1200

_, SYRUTSSIZEDFOR1100 INITIAL LAUNCH

CONDITION OF:

PODS-IllFULL "_ 7

1000 EMFTYV'------"Vi SOTA

.: FULL v" _.

, _00 EMPTY 0' .... "0

-_ TOTAL LOs LOAI) : _A720 kg (I03,000 Ib)

: NEAT RATES BASED ON STRUT

_00 DESIGNS FOR 37316.0 kg * FULL CASES ONLY' (liO, 000 Ib)

-_i PODS ORBITAL FREQUENCY • 10 HIt, 700

0 5 10 15 20

TIME (YEARS)

Ft9. 4-16 LO2 SSSTank No-Vent Pressure Htstory

52

1986000807-TSE01

m,

• i

Section 5

,t-" CONCLUSIONSANDRECOIOENDATIONS

:. 5.1 TASK1 - NODALVIBRATIONTESTS_,-.

',Jr....... _del vtbretton tests wereperformed on the PODS-Ill assably, and single:'- strut frequencies were determinedunder vartous preload conditions. These

_ test data were cOmparedwtth analytical results obtatned using linear finiteelement analysts theory, Including the effects of preload.

: The analytical models simulated the test configuration by Including thei .

i: accelerometer/clamp assemblythat was attached to the fiberglass tube to

) monitor the strut's modal.vibration. The results obtatned confirmed the[ %.

_. tntttal assumptionof the Importanceof the effects of thts assemblyon thei, fundamental frequency and associated modeshape. As-butlt frequencies were

predicted by excluding the lumpedwetght and demonstrateda 10 percent

)._ Increase tn the fundamental frequency for each preload case• Thts latter setof frequencies represents the strut's actual, unencumbered,fundamentalJ-':

_" frequenc_!F •!-

i" The fundamentalmodal responseof the strut wasdominatedby the fiberglass

tube for both orbit and launch strut configurations; however, tn tts orbit• t

configuration, the strut's graphtte tube also contributed. Analytical and ,1test results comparedfavorably for all but one launch condition case• The

i;" analytical results differ most significantly from the test results for the: orbit configuration due to "rattling" of the strut under low preload test

conditions. Becauseof thts phenomenaand the excellent comparisonsbetween

':i other analytical _nd test cases, tt ts concludedthat the analyticalfrequencies determined are accurate representat4ons of the strut's fundamental

L.

frequenctpc.

:.

, PRECEDING PAGE BLANK NOT FILMED

" PA INTENTIONALLYBLANll

1986000807-TSE03

! •

The ftMte elementmodeldevelopedvlthtn the scopeof thts project |s a beastcmodeland ts only adequateto represent fundmentel strut behavior. The

tests, hoverer, demonstratedhtgher, rare cmplex modalresponse Including

torston and bendtng. No attempt ws rode to predtct these Mgher modesof

vibration. However,tt ts concluded, basedon the strut's destgn, that thetorsional vibration reported durtng the tests ms a result of theecceleromter/climp offset massand not due to thestrut's structurul ....configuration.

Should the Mgher modesof the strut be of Interest, ttts recommendedthat ea

moredetatled model be developedto detemtne the "range of Interest"

frequenc|es and associated modeshapesto assess the overall strut dynamtcresponseunder various preloeadcondlttons. ;n addition, tests shouldbe

perfomed at morepreload potnts to comparevlth the anealyt|cal results andbetter.define the strut's behavtor under these conditions.

5.2 TASK2 - BEMEFITSTUDY

For the OTV, the largest benefits of ustn9 the PODS-Ill struts occur vlth

fully loaded tanks eatlaunch, at the lowest weamboundarytemperatures, andeat

the lowest orbltol resoneances.Only mtntmol benefits .accrue whenthe PODS-II!

supports are destgnedfor eanempty LO2 tank eatlaunch. However, the orbttelr_sonancesare so low, 4 Hz, the SOTAstrut resonancevealueprobably v111 heave

to be Increased substeant|eally(t.e., to 20 Hz) due to engtne ftrtngs tnorbit. Onthe other hand, the PODS-Ill nonshorted, orbtt support resonance !mAYnot l_ve to be |ncreeasedstnce the orbit resoneancertses to 35 Hz when

Shorted under typtcal orbttel engtne ecceleratton loeads. If thts occurs, the ]PODS-I!! support heat leeakadvantagev111 tncreeaseover the SOTAstrut for eanemptytank l eaunch.

For the SSStanks the sametrends hold true. In addition, the non-veapor-cooled PODS-IXIsupportsheaveIs learger releatlve eadveantegeover the SOTAstrutsthan whenthey are vapor cooled.

56

1986000807-TSE04

Since the cost differential ts small betweenfabricating PODS-I|! or SOTA

struts (Ref. 2) and the differential ts an Insignificant fractton of the total

cryogen tank costs, tt ts recommendedthat the PODSsupports be usedfor all

OTVand SSStank applications. The PODS-IVverston currently betng developed

wtth potentta11_ a side-load shorttng resistance ten ttms that of PODS-]l! ts

the recommendeddestgn chQJr__f_r_t_se large tank applications.

!

"! 57

' 1986000807-TSE05

4

, ,#

,-..

-:::- Sect,ton 6::: REFEREEES

_. 1. Pamley, I. T., Feastb|ltty Study for LongLtfettm Heltum Dewar,NASACl...._ 166254, Dec 1981., ,_

::_r 2. Pamley, R. T., PasstveOrbttal Disconnect Strut (PODS-ZlI) Structural

;_ and ThermalTest, Program,NASACR166473, Mar1983.

_:_ 3. Parmley, R. T., Passtve Orbttel DisconnectStrut, (PODS-ZZZ)Structural_Y" Test Program, NASACR 177325, Oan198S.

':': 4. Vanderplaat,s,S. N., and Moses,F., "Structural Opt,|mtzat,tonby Met,hods

of Feastble Direct,tons," Computersl Structures, Vol. 3, pp. 739-755,i_. 1973.

_: 5. Vanderplaats, G. N., "COMNZH-AFORTRAHProgramfor Const,ra_nedFunct,_on

4/- MtntMzatlon; User's Manual," NASATMX-62_282, AmesResearchCenter',::; Moffett Fteld, CA, Aug 1973; verston updatedtn Mar 1975.

' 6. Zoutendtlk, S., Methodsof Feas|ble Directions, Elsevter PubltsMng Co.,_;.: Amsterdam,1960.

- 7. ]nhousecommunicationvlt,h Spacestar|on Group.

' Z'

_:z 8. AdvancedManeuveringPropulsion Syst,em,LMSC-687208,1969.

ir -,

.).., 9. Havas, T. W., ASTROPrL)gramManual, LockheedMtsstles & SpaceCompany,:' Inc., re.ton J 1J-073185).

. PRECEDING PAGE BLANK NOT,FIEMED._.-

' ': 59 !,:'"__:._":: . . ...... . : PAGE_ INTENTIONALLYBLAIV_..................................._ :

] 986000807-TSE06

4655w

SecUon 7

APPENDIXA - MODAL.RESONANCETEST RESULTS

The a_lttance functton and phase plots gtven here are test data finn Sectton3.3. The tes_ numbers shown on the curves refer to Table 3-2. The axes shown

gtve the accelerometer locations and directions. For the phase plot=, when

the curve htts the +180 deg or -180 deg l the and _umpsIbruptly to the other

extreme, |t ts only an arttfact of the plot routtne and does not represent a r

phase shtft.

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