AD-A248 943111111 IIK I III IIII IIIIICIII I

PL-TR-91-2194

DATA ANALYSIS SUPPORT FOR THE SHUTTLEPOTENTIAL AND RETURN ELECTRONEXPERIMENT (SPREE) ON THE TETHEREDSATELLITE SYSTEM 1 (TSS-1) FLIGHT

T. T. Luu [ TICJ. R. Lilley

ELECT _V. A. Davis

Maxwell Laboratories, Inc. ..... -"

S-CUBED DivisionP.O. Box 1620La Jolla, California 92038-1620

June 24, 1991

Scientific Report No. 1

Approved for public release; distribution unlimited

Phillips LaboratoryAir Force Systems CommandHanscom Air Force Base, Massachusetts 01731-5000

92-09495

"This technical report has been reviewed and is approved for publication"

MARILYN R. b"ERHARDT, CAPT, USAF E. G. MULLENContract Manager Branch Chief

RITA C. SAGALYNDirector, Space Physics Division

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June 24, 1991 r Scientific Report No. I4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

"Data Analysis Support for the Shuttle Potential and Return Electron Experiment F19628-90-C-0133

(SPREE) on the Tethered Satellite System I (TSS-l) light" PE 634 OF

6. AUTHOR(S) PR 2822TA01 WUAK

T. T. Luu V. A. DavisJ. R. Lilley I. Katz

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATIONREPORT NUMBER

Maxwell Laboratories, Inc.

S-Cubed Division SSS-DPR-91-12627P. O. Box 1620La Jolla, CA 92038-1620

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORINGAGENCY REPORT NUMBERPhillips LaboratoryPLT-124

Hanscom Air Force Base, MA 01731-5000 PL-TR-91-2194

Contract Manager: Capt. M. Oberhardt/PHE

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release;disbribution unlimited

13. ABSTRACT (Maximum 200 words)

This report describes the first year of a scientific study of the interactions between the first flight of the Tethered SatelliteSystem (TSS-1) and the ionosphere to increase understanding of the structure and current characteristics of high-voltagesheaths in the ionosphere. The investigations described here include a determination of the tether current and voltages,an evaluation of the shuttle orbiter ion collection, the ion current detected by the SPREE instrumentation, and the effectof the subsatellite thrusters on the surrounding neutral densities.

14. SUBJECT TERMS 1S. NUMBER OF PAGES

tether, TSS-I, shuttle, current collection, SPREE 12616. PRICE CODE

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT

OF REPORTj OF THIS PAGE OF ABSTRACT

Unclassified Unclassified Unclassified SAR

NSN 7540-01-280-5500 Standard Form 298 (Rev 2-89)Prescribed by ANSI Sid Z39-18

TABLE OF CONTENTS

Section Pg

1. IN T R O D U C T IO N ..................................................................................... 1

2. CALCULATION OF TSS-1 USING EPSAT (SPECIAL

V E R S IO N ) ................................................................................................ 3

2 .1 Intro d uctio n .................................................................................. 3

3. CALCULATIONS OF ION CURRENT COLLECTED BY

SHUTTLE ORBITER .............................................................................. 11

4. CALCULATIONS OF ION CURRENT COLLECTED BY THE

SPREE INSTRUMENT .......................................................................... 13

5. OBSTRUCTION OF CURRENT OF SPREE INSTRUMENTS

DUE TO RMS AND CAMERA ............................................................ 85

5 .1 O bjective s .................................................................................... 8 5

5 .2 P roced u re .................................................................................... 8 5

5.3 R un C ases ................................................................................. 8 5

5.4 Param eters ................................................................................. 86

5 .6 R esults ......................................................................................... 8 9

6. CALCULATIONS OF ION CURRENT COLLECTED BY

SHUTTILE oCRrITE .................................... ..........................

6.1 Ion Current Collected as a Function of Orientation .............. 103

6 .2 R e su lts .......................................................................................... 10 8

6.3 Ion Current Collected as a Function ............................................ 109

7. NEUTRAL DENSITIES ABOUT TSS-1 SUBSATELLITE ............... 111

Iil

1. INTRODUCTION

This interim report covers the period June 15, 1990, to June 23, 1991, anddescribes the scientific progress on Contract F19628-90-0133 entitled "DataAnalysis Suport for the SPREE Instruments on the TSS-1 Shuttle Flight." The

objective of this contract is a scientific study of the interactions between the firstflight of the Tethered Satellite System (TSS-1)and the ionosphere to increase

understanding of the structure and current characteristics of high-voltagesheaths in the ionosphere.

During the first year of this contract, we investigated the tether current andvoltages, the shuttle orbiter ion collection, the ion current detected by theSPREE instrument, the effect of the subsatellite thrusters on the neutraldensities, and provided support for the TSS-1 program.

The technical staff who contributed to the research described in this report are I.

Katz, J. R. Lilley, Jr., T. T. Luu, and V. A. Davis.

Aooegg1on For

NTIS GRA&I

DTIC TAB 0Unannounced 0Just ification

By- .

Availabilty 0""ti &Wtr

l4 p~a

2. CALCULATION OF TSS-1 USING EPSAT (SPECIAL VERSION)

2.1 INTRODUCTION

Calculations of the tether current and voltages over the mission were performed

using a specially modified version of EPSAT (Environment-Power SystemAnalysis Tool). The model consisted of an orbiter with the subsatellite extended

20 km out of the bay. Collection of electrons was the product of the 1-sided

thermal flux and 2nr 2 times the minimum of the space-charge-limited or

magnetic-limited collection radii. The ion collection is just the space-charge-

limited ion collection to a sphere with effective area that of the engine bells.

The first calculations examined the effect of subsatellite paint resistance on the

tether currents. It is uncertain whether the subsatellite paint will be 8K Q, the

highest impedance in the tether circuit, or whether it will have negligible bulkresistance at the operating potentials. With the core gun on, usirg a perveance

of 3.8 x 10-6, tether currents were calculated for the mission duration of different

sphere and tether resistances. The results were surprisingly insensitive to the

paint resistance. When the total resistance, tether plus subsatellite paint, was10K Q, the peak current was about 60 percent of that for an assumed 2K Q

resistance. Peak subsatellite potentials differed little, because they occur at low

plasma density when low ionospheric currents cause the resistive voltage drop

to be negligible.

The other sequence of EPSAT studies examined orbiter potentials when the

tether is connected to the orbiter chassis through a large resistance. Theresistances studied were between 25K Q and 350K 0. The calculations showed

that the orbiter would charge only at low plasma density, again because the

resistive voltage drop is small due to low tether currents. However, orbiter

potentials as large as -2200 V resulted when the total tether, subsatellite, andshunt resistance was 35K Q.

3

The FPSAT Model

Problem Name: spree2 I I >HELP<! Object Definition I

-Axial Views of System Axonometric View of SystemView Front View Direction:

View Side Draftino View Theta 0.0View Too Phi 0.0

Axonometric View

Create Another Object Delete An Object

Solar Position Dimensions Orientation

Object Array Les(Z)Nidth(Y)Hqht(X)Theta Phi Twist

.ose no -14.0 1.0 C.3 4.00 4.00 8.00 0. 0. 0. surf spec.ocdy nc 0.0 0.0 0.0 8.00 8.00 20.00 0. 0. 0. surf spec.wing no 5.0 0.0 0.C 1.00 30.00 10.00 0. 0. 0. surf spec.tail no 7.5 0.0 8.1 5.00 1.00 5.00 0. 0. 0. surf spec.

engines ro 10.5 0.0 0.0 8.00 8.00 i.00 0. 0. 0. surf spec.

spree no 0.0 0. 8.0 2.00 1.00 i.00 0. 0. 0. surf-spec.ss no 0.0 3.0 .02 1.02 1.02 0. 0. C. surtfspec.

The conducting surfaces are spree, engines, and subsat.

2ap ViW t o DrWr

4 4

t8

-10

--B

"-a - l~a -i Q 5 0 15 2x

Figure 2.1 The EPSAT model of the shuttle orbiter.

4

Gda Mow of Ski e Orbiter20

16-

10-

N 3

01-o

-10-20 -IS -io -5 a 5 10 15

Figure 2.2 Side view of the EPSAT Orbiter model.

The model was oriented with the subsatellite away from the earth.

Update I Object Orientation................................................................................

Rotation from Body to (Ram) Space FrameX(Velocity Direction) Y Z(Down)

Rotation Axis 1.000 0.000 0.0OCRotation Angle 1.800E+02

Stabilization gravity

Spin StabilizationX(body) Y(body) Z(body)

Rotation Axis 1.000 1.000 1.000Rotation Rate 0.000E+00................................................................................

Time intoMission 9.420Ef04Vector_ trom System Center to PoinIt Veocity Vector

Poi nt Rody >pace I Hody SpaceAltitude 0.000E+00 X 1.407Ei05 N 7.407E,05 I X 7. 2CE-C3 N -3.!5CC'CLatitude 0.000Ei00 Y 5.679E+06 E -b.679E 06 Y -6.i43E-J8 E 7.053E.03Longitude 0.OOOE+00 Z -9.587E+06 D 9.587E+06 I Z -. 093E-01 D 7.083E-C

5

Tether Current with Electron Gun

0.28

0.20

0.1a

.a

0. 4.OOE+O4. 9.OOE-e04mr.Icn tim. Can)

Figure 2.3

Plasma Density During TSS-I Mission

2N 1.5-t-12

2 .0CE+1ZI

V v

a.++UEt4 Oz-2~o IM(c

Fiue .

~ 1.0-I-6

Max Tether Current vs. Total Resistance0.48

a .40

a -~

0 0.30

.25-

S0.20

0.15

0.10

0.110

0 4000 8000oubeatilo de tathar radatnoo ( hme)

Figure 2.5

Results for a low current time on orbit.

No gun, 35K Q impedance.

Update I Floating Potentials

Max Iterations 15 Plasma Tnermal CurrentsMax Current 1.O00E-03 ion 9.6263E-06Voltage tol 1.OOOE-02 Electrun -6.4821E-04

Altitude 399. Magnetic Field (B)Mission Time l.OOE+03 Latitude 25.3 Ncth 0.163Unvrsl Time 1.00E+03 Longitude 58.6 East -3.595E-32Angle between velocity and solar array 24.5 Down -0.210

Bias V X B FloatingCbject Location Radius Voltage Voltage Pctentiai C-rrent

nose -14.0 0.0 2.0 3.6 0.OOOE+00 0.OOOE+00 -2222. 0.body 0.0 0.0 4.0 7.8 O.O00E+C0 4.163F-01 -2222. 0.wing 5.0 0.0 0.5 7.4 0.000E+00 -3.18E-',1 -2222. 0.tall 7.5 0.0 10.5 2.4 O.0COE+O0 I. 7 E,,) -22? 0 0.

unqines; 10.5 0.0 4.0 3.6 0.030E+00 4.1 .42K-" -2222. 1.745E-02spree 0.0 0.0 8.' 0.1 0 .000 00 .09..0 E00 -2221. 2.445E-03subsat 0.0 0.0*0** . 0.000*00 4.1 ( 0 F 22 -1.990F-02

7

3.8E-6 Perveance, 10K Q Impedance.

UJpdate Floatino Potentials

Aax iterations isPlasma Thermal CurrentsMax C, -rrent i.c3OL-C3 Ion 9.6263E:-C6

Joltage tol 1.OO3E-02 Electron -6.4821E-C4Aiti*-&Je 399. Magnetic Field (B)

Mission Time 1-.0102-03 Latizde 25.3 North 0.163..vrsl1 Time 1.O1CE±03 Longltude 58.6 East -3.595F-02

Angle betwdeen velocity and soiar ar:ay 24.5 Down -0.210

Obe Bias V X B FloatingCblo Location Radius Voltage Voltaqe Potential Current

nose -'.4.0 01.3 2.3 3.6 0.0002+00 0.0002+00 -340.5 0ody D.C C.3 4.0 7.8 0.000Ei00 4.163E-01 -340.1 0.

W~g5.0 0.0 0.5 7.4 0.0002+00 -3.181E-01 -340.8 0.tal35 0.0 l0.L 2.4 0.0002+00 1.777EF00 -338.7 0.

engires 10.S 0.0 4.C 3.6 0.0002+00 4.1422-01 -340.1 3.235E-02soree 0.01 0.0 8.-- 0.7 O.OOOEiOO 1.359Et00 -339.2 7.671E-04

s';zsa7: 0.0 J.C*"* 0.7 0.0C0E+00 4.290E+03 3519. -3.311E-02

The orbital parameters used for the EPSAT study.

~oa~e I rb'Jt GeneratorI

Oroit Parameters1 Name Valie Name Value Mission Start

Timr. Span z4. X) PNum of Pts 200 Day 335.A c20 .00 P er iq ve 4100.00 Time 0.

ndl:.c ~ m 28.0;3 Ma Anomaly 0.00 Year 1991.Ar3, j' Perlqjee 0 .(0 Kt Ascension 0.00

uyAv, .iq( M: orurm Max mumA 4. 4F~j 6 F,- 024 .10DE, 2

E, F0.1 6.035E-C2 3.566F~i02-2. 9v 2. 7982 401

A.mJo La!n i uo~ .. rq 1t ude Velocity

t3 3-- 1 4 .I 1 2 /. 2580

Plasma conditions at one time during the mission.

Update I Arb~ent Plasina

MLss'ion Paramneters

Start Day 335. Sunspx'- :-71Time into Mission 9.42OJE'04

Orbital PcsitjonVajLeName Value NameoV

Ait ude 402 .27 iDuy *.f Yeal 33f1.Lat itude 14 .78 Uniiversa, iV-. ! . "':ELongitude 11/.1 .CISun1spoz. N.;o i~

spetieOS lens;ity p S

atomic oxyqeo1 1.498E1 aL ;MCT lU? 1 4e 2 . 9FhelIi um 3 . 111E +:0 ( .mlcuL;1 1 cx Ync T ; -67nitric _oxide 0.000E,00 Electzcn

Electron Temperature 9.3885-02 Ion qemrperantu.re

Orbiter Potential vs. Ion Current

C&LA

-2513G -

-30004-OPE-00 aM a 12E0

-%er Io crenaorp/r2

Fiue .

a9

Potentials With 35K Ohm Shunt lanud

2000- inEM nu"r FI (Mnl)

o100

a.

-2000

-3000 ''0 1000 200D 3000 4000 .5000

mmion 1ti m (4S)

Figure 2.7

Orbiter PotentTal vs. Shunt Resistancec]

-500

-1500

I -2500

-300

-'IDOGi i

0. 1.00E+05 2OE+05 JQ.OE-45rI ita go ({h me)

Figure 2.8

10

3. CALCULATIONS OF ION CURRENT CC'LECTEDBY SHUTTLE ORBITER

Using NASCAP/LEO, the collected ion (oxygen) currents were calculated as a

function of voltage, plasma density, and the orientation of the shuttle orbiter with

respect to the ram. The ion currents were found by varying the conducting

surface potentials (the engine nozzles), computing the ion wake formed behind

the moving shuttle, calculating the resulting spatial plasma potentials, and then

pushing ions from an equipotential plasma sheath.

The shuttle model was made using PATRAN. The model coordinate system is such

that the tail rises in the +x direction, the nose is in the +z direction, and starboard

side of the shuttle is the +y direction. For the purposes of this calculation, only the

engines nozzles were considered conducting (aluminum in the figure). The

calculations used a nested, cubical grid with a mesh size of 1.645 meters. The

plasma temperature for all of the calculations was 0.1 eV. The surface potentials of

the insulating surfaces were defined to be -0.5 volts to simplify the calculations.

The varied parameters were the potential of the conducting surfaces (-10, -100,

-300, and -1000 volts), the plasma density (10**11 and 10**12 ions/meter**3),

and the shuttle orientation with respect to its velocity 7500 meters/sec (cargo

bay 45 degrees into the ram and into the wake). The corresponding shuttle

velocity vectors in model coordinates are (5303, 0, -5303) meters/sec for the

bay facing in the ram direction and (-5303, 0, 5303) meters/sec for the bay

facing in the wake direction.

The results of the calculations follow:

Bay into the ram (shuttle velocity was (5303, 0, -5303) meters/sec)

Conductor potential Current (amps) at density (ions/meter**3)(volts) 10**11 10**12

-10 4.1 E-03 4.1 E-02-100 8.9E-03 8.9E-02-300 1.5E-02 1.5E-01

-1000 2.3E-02 2.1E-01

11

Bay into the wake (shuttle velocity was (-5303, 0, 5303) meters/sec)

Conductor potential Current (amps) at density (lons/meter**3)(volts) 10**11 10**12

-10 4.O1E-1 5 1.4E-13-100 1.9E-03 2.21E-02-300 5.OE-03 4.7E-02

-1000 1.9E-02 1.4E-01

COLOR LEGEND

12

4. CALCULATIONS OF ION CURRENT COLLECTEDBY THE SPREE INSTRUMENT

Using NASCAP/LEO, ion (oxygen) currents were calculated as a function of

voltage and the orientation of the SPREE instrument with respect to the flowing

plasma. The currents calculated were the total current to each of the detector

entrance screens, the current that entered the detector within 10 degrees of the

surface normal, and the weighted (by particle current) average angle of

particles striking the detector entrance.

The ion currents were found by varying the surface potentials of the detector

cases, computing the ion wake formed by the moving instrument, calculating the

resulting spatial plasma potentials, and then pushing ions from an equipotential

plasma sheath. The particle velocity and current were used, saved, and

postprocessed to compute the calculated currents.

The SPREE model was made using PATRAN. The model coordinate system is

such that the detectors rise in the +y direction with the base plate in the x-z

plane. The detector with screen 2 is higher in z than the detector with screen 1.

The potentials were applied to the case of the detectors and their screens. The

calculations used a nested, cubical grid with a mesh size of 0.04 meters. The

plasma temperature for all of the calculations was 0.1 eV. The surface potentials

of all of the surfaces other than the case of the detector were defined to be -0.5

volts to simplify the calculations.

The varied parameters were the potential of the conducting surfaces (-100,

-300, and -1000 volts) and the SPREE orientation with respect to the flowing

plasma (or orbiter velocity of 7500 meters/sec). Two orientations were studied.

In case 1, the flow direction corresponds to the orbiter nose up 45 degrees and

the cargo bay into the ram. Case 2 arises when the orbiter is oriented with the

wings parallel to the flow (shuttle moving to port or starboard). The

corresponding SPREE velocity vectors in model coordinates are (0, 5303,

-5303) meters/sec for case 1 and (7500, 0, 0) meters/sec for case 2.

13

The results of the calculations follow:

Case 1 Nose up, cargo bay into the ram. (SPREE velocity was (0, 5303, -5303)meters/sec.) In this orientation, the Iow-Z detector is the aft detector.

AFT DETECTOR

Vozltage (vlts) -MO -Mo -lO00Total current (pA) 4.88 1.15 1.61

Current within10 degrees (IiA) .0303 .055 0.

Weighted averageangle detected (degrees) 43.8 64.9 59.4

FORWARD DETECTOR

Voltagoe fvolts) -1_m -3m -1000

Total current (iA) 2.43 .694 2.71

Current within10 degrees (IA) .0962 0. .073

Weighted averageangle detected (degrees) 43.4 49.3 41.7

Case 2 Orbiter moving sideways. (SPREE velocity was (7500, 0, 0)meters/sec.) In this orientation, the low-Z detector is looking towardsits wake and the high-Z detector is looking upstream.

LOW-Z DETECTOR (DETECTOR 1), WAKE VIEW

Voltage(.volts M-100 -0

Total current (p.A) 5.14 4.93 3.84

Current within10 degrees (pA) .102 0. 0.

Weighted averageangle detected (degrees) 47.5 67.0 56.7

HIGH-Z DETECTOR (DETECTOR 2), RAM VIEW

Voltage(vl-100 -3oo -1000Total current (pA) 2.43 5.18 4.03

Current within10 degrees (gA) .098 0. 0.

Weighted averageangle detected (degrees) 43.1 72.6 59.4

14

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5. OBSTRUCTION OF CURRENT OF SPREE INSTRUMENTSDUE TO RMS AND CAMERA

5.1 OBJECTIVES

This chapter describes the investigation of the degree of obstruction to the

SPREE instrument due to the RMS (Remote Manipulation System) and the

camera mounted on top of the RMS.

5.2 PROCEDURE

The calculations were done using NASCAP/LEO, which has been modified to

treat wake and ram particles more efficiently. The currents calculated were

1. Total current to the SPREE instruments (the two boxes);

2. Total current to each of the detector entrance screens;

3. Current that entered the detector within 100 of the surface normal; and

4. The weighted (by particle current) average angle of particles striking the

detector entrance.

5.3 RUN CASES

Ion currents to the detectors were calculated for three cases:

1. SPREE only (repeat previous calculation);

2. SPREE and RMS and nonconducting camera;

3. SPREE and RMS and conducting camera.

85

5.4 PARAMETERS

Parameters common to all three cases are as follows:

Plasma temperature 0.1 eVIon density 1011 M-3

Orbiter velocity 7500 m/sInner grid mesh size 0.06 m

In all cases, a potential of -300 V is applied to the surfaces of the detector cases.In case 3, the same potential is applied to the camera surfaces as well.

5.5 ORIENTATIONS

In all cases, the Iow-Z detector is looking toward its wake and the high-Zdetector is looking upstream. Different orientations used in the calculations areshown in table 5.1.

Table 5.1 Detector orientations used in calculations.

Case 0(0) 0(o) Velocity(m/s)1 0 -10 7386,0,-13022 10 -10 7274,1302,-12833 20 -10 6941,2565,-1224

4 0 0 7500,0,05 10 0 7386,1302.06 20 0 7048,2565,0

7 0 __ 10 7386,0,13028 _ 10 _ 10 7274,1302,1283

9 20 10 6941,2565,1224

The symbols 0 and 0pare defined in figure 5.1.

86

y

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87

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5.6 RESULTS

All currents are in amperes. The low-Z detector is facing the wake, and thehigh-Z detector is facing the ram.

Table 5.2 Total currents collected by both detector boxes.

Orientation 0 A Case 1 Case 2 Case 31 0 -10 2.27e-4 1.75e-4 1.76e-4

2 10 -10 2.14e-4 1.61e-4 1.63e-4

3 20 -10 2.03e-4 1.71e-4 1.30e-44 0 0 2.25e-4 1.85e-4 1.86e-4

5 10 0 2.03e-4 1.52e-4 1.51 e-46 20 0 2.02e-4 1.72e-4 1.31e-47 0 10 2.25e-4 1.83e-4 1.83e-4

8 10 10 2.13e-4 1.61e-4 1.58e-49 LO 10 2.12e-4 1.71e-4 1.38e-4

Table 5.3 Total currents collected at the detector screens.

Low-Z High-ZOrientation 0 4 Case 1 Case 2 Case 3 Case 1 Case 2 Case 3

1 0 -10 6.82e-6 7.31e-6 9.52e-6 8.15e-6 7.72e-6 6.86e-62 10 -10 6.43e-6 6.39e-6 6.79e-6 5.84e-6 4.77e-6 6.55e-63 20 -10 5.69e-6 6.63e-6 4.76e-6 5.76e-6 3.90e-6 5.60e-64 0 0 7.17e-6 6.52e-6 8.41e-6 6.06e-6 8.20e-6 7.59e-65 10 0 5.41e-6 5.46e-6 4.72e-6 5.79e-6 6.17e-6 6.05e-6

6 20 0 5.16e-6 6.28e-6 4.17e-6 5.25e-6 5.45e-6 6.53e-6

7 0 10 6.06e-6 6.13e-6 6.67e-6 6.32e-6 6.69e-6 6.29e-68 10 10 5.37e-6 5.01e-6 2.69e-6 5.68e-6 5.94e-6 4.95e-6

9 20 10 4.52e-6 5.11e-6 4.26e-6 6.09e-6 6.39e-6 3.49e-6

89

Table 5.4 Total currents entering the detectors within 10c

of the surtace normal.

Low-Z High-ZOrientation 0 (p Case 1 Case 2 Case 3 Case 1 Case 2 Case 3

1 0 -10 1.45e-7 1.42e-8 1.64e-7 5 27e-7 5.20e-7 0.2 10 -10 1.37e-7 1.08e-8 3.97e-8 5 47e-7 7.06e-7 0.3 20 -10 1.34e-8 4.04e-9 6.40e-9 6.91e-7 7.87e-7 1.73e-74 0 0 3.94e-8 6.06e-9 2.05e-8 4.53e-8 2.61 e-7 9.23e-75 10 0 1.77e-8 3.05e-10 4.92e-8 1.77e-8 1.63e-7 8.26e-76 20 0 3.38e-10 1.10e-9 4.16e-9 2.00e-7 1.09e-7 3.02e-77 0 10 1.19e-7 4.15e-8 3.37e-10 3.65e-9 0. 3.73e-78 10 10 2.13e-20 3.87e-20 7.53e-8 9.31e-8 0. 9.67e-89 20 10 1.37e-9 1.34e-10 2.47e-8 5.65e-8 0. 6.89e-10

Table 5.5 Weighted average angle of the particles striking the detectors.

Low-Z Hi h-ZOrientation 0 i) Case 1 Case 2 Case 3 Case I Case 2 Case 3

1 0 -10 47.5 50.8 38.9 34.6 36.9 44.52 10 -10 47.7 50.0 41.4 27.8 31.0 39.23 20 -10 49.1 48.0 45.0 23.8 23.2 38.04 0 0 47.2 50.3 42.3 29.1 33.4 50.75 10 0 55.4 48.1 42.3 26.5 35.2 34.06 20 0 49.9 48.1 48.6 25.9 31.9 35.27 0 10 47.0 44.5 39.0 28.0 37.7 51.98 10 10 54.9 45.7 40.1 25.2 37.1 48.39 20 10 48.3 47.4 40.7 23.8 35.6 52.4

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6. CALCULATIONS OF ION CURRENT COLLECTEDBY SHUTTLE ORBITER

This attachment describes the calculations of the collected currents as afunction of the orientation of the orbiter with respect to the ram, the potential,

and the plasma density.

6.1 ION CURRENT COLLECTED AS A FUNCTION OF ORIENTATION

The calculations were done using NASCAP/LEO, which has been modified to

treat wake and ram particles more efficiently.

The following procedure was used in this set of calculations:

1. Select an orientation of the orbiter;

2. Compute the ion wake formed behind the moving shuttle;

3. Calculate the resulting spatial plasma potentials;

4. Push ions from an equipotential plasma sheath to compute the collected

current.

This set of calculations was done with the following parameters:

Plasma temperature 0.1 eV

Ion density 1012 m -3

Orbiter velocity 500 m/s

Conductor potential -300 V

103

Rotalion Axi 0

0I

sT

Figure 6.1 Shuttle orientations used in these calculations.

As shown in figure 6.1, the nose of the orbiter was tilted 450 up, and the orbiterwas rotated around the vertical axis. The orbiter's belly was facing the ram at 0°

rotation and the wake at 1800. The rotation step was 150. Shuttle velocityvectors (traveiing at 7500 m/s) are given in table 6.1:

Table 6.1 Velocity vectors of the shuttle in the different orientations.

Case I-An gl(1_ Velocity(m/s)1 } 0 -5303. 0. 5303.21 15 -5123. 1941. 5123.3 i 30 -4593. 3750. 4593,4 ( 45 -3750. 5303. 3750,5 .60 -2652. 6495 2652.

6 r 75 -1373. 7244. 13737 .90 0. 7500. 0.

8 105 1373. 7244. -1373.

9 120 2652. 6495. -2652.10___ 135 3750 5303. -3750.

11 150 4593. 3750. -4593.12_ 165 5123. 1941. -5123.

13 180 5303. 0. -5303.

104

Figure 6.2 shows the model of the shuttle used for these calculations.

COLOR LEGEND

U

(a)

Figure 6.2 Patran model of the shuttle from three directions.

105

Positive X View17.

16-

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(C)

107

6.2 RESULTS

At 00 angle, the orbiter is traveling with its belly facing the ram directly and theengine nozzles were in the wake. Thus, little current was collected.

As the orbiter rotates, more of the engine nozzles were exposed to the ram sideof the orbiter and more current was collected.

At 900, the orbiter is moving sideways to the ram, and most of the sides of thenozzles were exposed to the ram. The currents to the nozzles' sides peaked atthis point and remained steady.

At 1 800, the nozzles faced the ram direction, and the currents to the faces of theengine nozzles peaked.

Table 6.2 and figure 6.3 show ion current at different rotation angles. Allcurrents are in amperes.

Table 6.2 Collected current at different orientations.

SCase Angle Exterior Nozzle Bay Inside Nozzle Total_____Face Doors Doors

1 0 1.1e-6 4.2e-3 0.Oe+0 0.Oe+0 5.5e-3 9.675e-32 15 1.i1e-5 4.3e-3 0.Oe+O 0.Oe+0 4.7e-3 9.086e-33 30 2.0e-5 4.3e-3 O.Oe+O 0.Oe+O 5.7e-3 1.O0le-24 45 1.8e-5 4.4e-3 0.Oe+O 0.Oe+O 9.2e-3 1.360e-25 60 1.1e-5 6.2e-3 O.Oe+O O.Oe+0 1.7e-2 2.347e-26 75 5.4e-5 8.0e-3 O.Oe+0 0.Oe+O 2.6e-2 3.418e-27 90 1.4e-4 1.0e-2 0.Oe+0 0.Oe+O 3.0e-2 4.082e-28 105 3.4e-4 1.4e-2 0.Oe+0 O.0e+0 3.2e-2 4.655e-29 120 6.5e-4 1.9e-2 0.Oe+0 0.Oe+0 3.3e-2 5.247e-210 135 5.9e-4 2.3e-2 0.Oe+0 0.Oe+0 3.3e-2 5.711 e-211 150 6.3e-4 2.7e-2 0.Oe+0 O.Oe+0 3.3e-2 6.071 e-212 165 5. 1e-4 3.0e-2 0.Oe+O 0.Oe+0 3.2e-2 6.313e-213 180 2.7e-4 3.1 e-2 0.Oe+0 0.Oe+O 3.3e-2 6.406e-2

108

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0.04 -,- Nozzle Faces

- 0.03 "" Nozzle Sides

o'0 A' Total- 0.02

0.01 ,

0 20 40 60 80 100 120 140 160 180

Rotation Angle (0)

Figure 6.3 Ion currents vs. rotation angles.

6.3 ION CURRENT COLLECTED AS A FUNCTIONOF POTENTIAL AND PLASMA DENSITY

The following procedure was used in this set of calculations:

1. Compute the ion wake formed behind the moving shuttle.

2. Calculate the resulting spatial plasma potentials.

3. Push ions from an equipotential plasma sheath to compute the collectedcurrent.

The varied parameters are conductor potentials, orientation, and plasmadensity.

1. Conducting potentials: -10, -100, -300, -1000 V

2. Velocity vectors: (5303,0,-5303) for bay-to-ram direction and(-5303,0,5303) for belly-to-ram direction.

109

Tables 6.3 through 6.6 give the results of the calculations. All currents afe. Ct

amperes.

Table 6.3 Ion current collected with bay-to-ram and 1011/m 3 plasma density.

Pot. Tell Silv Kapt SiO2 Alum 1 Total•10 1.2e-04 2.1e-03 0.0e+00 0.Oe+00 1.5e-03 3.721e-03

-100 7.9e-05 3.3e-03 0.Qe+00 0.Oe+00 4.1e-03 7.414e-03-300 6.5e-05 3.9e-03 .0Oe+00 0.0e+00 6.le-03 1.011e-02

-1000 1.0e-04 4.7e-03 0.Oe+00 0.Oe+00 9.9e-03 1.466e-02

Table 6.4 Ion current collected with bay-to-ram and 1012/m 3 plasma density.

Pot. Tell Silv Kapt SiO2 Alum Total-10 1.2e-03 2.le-02 0.Oe+00 0.Oe+00 1.5e-02 3.703e-02

-100 6.9e-04 2.5e-02 0.Oe+00 0.Oe+00 2.1e-02 4.618e-02-300 2.7e-04 3.1e-02 0.Oe+00 0.Oe+00 3.3e-02 6.406e-02

-1000 4.8e-04 3.8e-02 0.Oe+00 0.Oe+00 5.1e-02 8.916e-02

Table 6.5 Ion current collected with belly-to-ram and 101 1/m3 plasma density.

Pot._ Te I Siiv Kapt SiO2 Alum Total

-10 1.5e-06 1.8e-06 5.0e-07 2.2e-07 2.5e-05 2.877e-05-100 3.6e-07 8.7e-04 0.Oe+00 0.Oe+00 9.3e-04 1.794e-03-300 6.4e-05 2.1e-03 0.Oe+00 0.Oe+00 1.8e-03 3.992e-03

-1000 4.3e-05 le-03 0.Oe+00 0.Oe+00 4.0e-03 9.160e-03

Table 6.6 Ion current collected with belly-to-ram and 1012 /m 3 plasma density.

Pot. Tel Silv Kapt SiO2 Alum . Total-10 2.7e-05 1.8e-05 1.Oe-07 6.0e-06 2.5e-04 2.992e-04

-100 4.4e-06 2.0e-04 1.8e-09 3.3e-08 7.6e-04 9.617e-04-300 1.1E-06 4.2E-03 0.OE+00 0.OE+00 5.5E-03 9.675E-03

-1000 3.5E-04 1.5E-02 0 OE+00 3.2E-08 1.6E-02 3.147E-02

110

7. NEUTRAL DENSITIES ABOUT TSS-1 SUBSATELLITE

We used EPSAT to examine the plasma environment and sheath structure of thesubsatellite when the subsatellite is at the highest potential it reaches with theelectron gun on. The perveance of the gun is taken to be 3.8 x 10-6, and the netresistance of the subsatellite paint, tether wire, and shunt is tal en to be 10 Mo.

Figure 7.1 shows the subsatellite potential as a function of time. The peakpotential is 3610 V at 1125 s into the mission. The plasma environment at this

time is shown in figure 7.2, and the potentials are shown in figure 7.3. Table 7.1shows the variation in potential with time near the peak potential time. Table 7.2

shows the Parker-Murphy (magnetic-limited) and space-charge-limited radii and

collected currents at the peak potential.

Subsoteilite Potenc (O.ur- O4000

3500 -

- 30C0

1250

00

1500CL

00

5000

o -- I I I - I I

0 1OOCO 20000 30000 400C0

time into misson (sec)

Figure 7.1 The subsatellite potential as a function of time. The perveance ofthe gun is 3.8 x 10-6, and the net resistance of the subsatellitepaint, tether wire, and shunt is 10 MQ.

111

Ambient I 'tpdjte DoTabilc HELP

L lasma i Probl em,: s-L(ue

5:ur t .). ' / I.A i u ,: 4(]O. 'I

Yar: 19910 Absolute U -e -- 2cngit uU,: 66.30

Day: 335 1 Year: 1991 Latitlde: 26.68

Univ Time: 0 1--> Day: 335 I

Time into Mi.ssion ' Jnv T ie: 1125 -- > Sunspot: 104.1125.0 I

Piasa E:nvircnment From 1R186

SpeCies Density

3.4 65 E103.762E10 Eiectron Temperature: 8.166E-02

-e, 4.8150E-09 Ion Temperaturo: 7. 597E-02

0.000E-00

e- 7.645E.10

Figure 7.2 EPSAT screen that shows the plasma environment at the highpotential point in the orbit.

i Floating i Update DoTable HELP!

eie, Parameters Potentials Problem: spree

into Orbital Position Plasma Environment Summary ------

:isslcn Altit.e: 400.41 Species Density Min Max

L2.1 ionqltoe: 66.30 o' 3.47EtI0 51110 1.90E+12

Latituce: 26.68 h* 3.76Etii 5.52Ei0 1.C3E+12

Xafjnet c Fie_<I (9) Velocty e- I.64E110 1.14E+11 2.29E12

X: .4 X: -;.. 4u eL2 sorat res Thermal Currents

Y:28 Y: 0.0c 1):.: '.6E-02 lon: 8.328E-06

Z: -0.24 Z: 4.92 E:ectr, r: 8.2E-02 Electron: -5.844E-04

Mac: .2E -1 Mac: . +.03

jc ecI Crecoct Loc6tic. CiL.c(tt Bias V X 9 Floating

- :-a:'± X Y Z RaJi- Volta VAt age Potent ,' a I C'r renL

- - - - - - -- -- -- ---- -- --- ---- -II 0. 3.Lhq - 0..31).1 0 C.

S.5 2.2 *.t <.4 U.0QL, ' 4. C I -334.i 0.

7 J=. r s C13 C. C 4.0 1 ., 0.0C ,)CFC0 4.217F.-01 -335.b 2.98 F-028 0 0.B.0E2O0 1.3/9E.0G -334.5 6.Z2 /L-04

d 3. ., D.C Z . k: 1 .9 0. 0E ,3 4.250E03 3609. -3.24 -u 2

Figure 7.3 EPSAT floating potential screen. This screen summarizes theenvironment, the potentials on each object, and the collectedcurrent for each object.

112

Table 7.1 Variation of floating potential with time.

Time (s) Subsatellite Potential (V)1100 36071123 36101200 35491300 32711400 2779

Table 7.2 Current collected by the subsatellite at 3609 Vin the above environment.

Collection Radius (m) Current Collected (A)Parker-Murphy(Magnetic-Limited) 2.88 -0.0305Space-Charge-Limited 6.13 -0.276

We also used EPSAT to examine the neutral densities and the likelihood of bulkionization under conditions of high outgassing, the 2 N in-line thruster, and the2.5 kg/hr leak.

In order to determine if enough neutral atoms will be outgassed from the subsatellite

to present a risk of bulk ionization, we examined outgassing densities for the casewhere all the surfaces emit 0.5 W M-2. This is the outgassing rate of G-1 0 afterexposure to air and provides an upper bound. Figures 7.4(a) and (b) show theneutral densities about the subsatellite due to outgassing at this high rate.Figure 7.5 is the neutral column density EPSAT screen. The screen shows that the

column density of outgassed neutrals from a point just outside the subsatellite (a1.02 m cube) to a point 2.88 m away (the Parker-Murphy radius) is 1.6 x 1017. With

a cross section of 3 x 10-20, the ionization fraction (number of ionizations as a

fraction of the number needed to cause ionization) is 0.0048. EPSAT (ionization

screen) estimates the ionization fraction to be 0.15 when the space-charge sheathsize is used as the average path length. Since breakdown is expected when theionization fraction approaches 1 and the outgassing rate used is orders ofmagnitude higher than expected, no bulk ionization is expected from outgassing

alone.

113

I -

(a)

MV xir'ur Cut.cs!,na Dens lies

Lege-d1 - 1.101

5 2 - 3 16211,1'OA / 3 - 1

¢

- - 3 16229=00"5 - I.I

i ~7 - IT1

6 6- 3 16228.:0e

2- i

/

0

(b)

Figure 7.4 Neutral densities about the subsatellite from outgassing at0.5 W m- 2 , which is a maximal rate. (a) s a 3-dimensional plot,

and (b) is a contour plot. The units of position are meters and ofdensity are molecules per cubic meter.

114

I Neutral Column I Update DoTabie HELP!

I Density I Problem:spree

Time into Absolute Date Orbital Position 7otal A:-bient

Mission Year: 1991 Altitude: 400.41 Neutral 3ensity1125.0 Day: 335 Longitude: 66.30 1.200E-14

Univ Time: 1125 Latituce: 2C.68

Column Parameters Column Display Integration Parameters

Length: 2.88 Display LengthOrigin Direction 1 2.88 Nurser of Points

X: 0.51 Theta: 90.0 Top View (XY Plane) 50Y: 0. Phi: 0.0 Front View (YZ Plane) Spacing of PointsZ: 2.OCE+04 i Right Side View (XZ Plane) Log

Point Density Along Column IDistance from Density I Column Density

Column Origin 2.758E+16 I !.u13F+171.27

Figure 7.5 EPSAT neutral column density screen for outgassing only.

We used the EPSAT nozzle model to model one nozzle of the 2 N in-line thruster onthe subsatellite. Figure 7.6 shows the parameters used in the model. Figures 7.7show the gas density about the subsatellite with operation of one nozzle of the 2 Nin-line thruster only. We computed column densities for the thruster gas. Thecomputations are shown in figure 7.8. The column density for a 2.88 m column offsetfrom the axis of the nozzle by 0.51 m is 5 x 102o. The column density for a 2.88 mcolumn normal to the axis of the nozzle starting 0.51 m from the nozzle is 6 x 1017.

Change Nozzle I Nozzle I Update DoTable HELP:Nozzle Name: InLine 2N I Analysis I Problem: spree

Nozzle ---- Nozzle Direction ---- Neutral Relative

Position Spher. Angles Unit Vector Species Abundance

X: 0.0 Theta: 90.0 X: 1.0 Add Species

Y: 0.0 Phi: 0.0 Y: 0.0 Delete Species n2 1.03Z: 20000.0 Z: 0.0

------------ --------- Input Parameters----------------------Length: 1.700E-02 Stagnation Temp: 1.730E+02

Exit Radius: 4.560E-03 Staqnation Press: 1.700E-06Exit Mach Number: 6.940E+00------------ -------- Derived Parameters---------------------Throat Radius: 4.555E-04 Number Flow Rate: 5.998E+22

Thrust: 1.91 Mass Flow Rate: 2.7907-03Area Ratio: 100. Gamma: 1.40

------------ ------ Density From the Nozzle------------------Origin Spnerical Coord I Cartesian Coord

X: 0. Rho: 0. 1 X: 0. Total NeutralY: 0. Theta: 0. I-> Y: 0. Density

Z: 2.000E04 Phi: 0. I Z: 2.000E+04 1.931E+24

Figure 7.6 Nozzle model screen showing parameters used to model onenozzle of the 2 N in-line thruster.

115

(c

0=c

0--

C.

aN< UN'-0

CCCa)

4- -

- N2E0~~~ 0 C-

CD IU)

4 4

- I ED00

r /

-~~~- Z ' N-0i

x - c

116 U

I Neutral Column Update DoTable HELP!I Density I Problem:spree

Time into Absolute Date Orbital Position Total Ambient

Mission Year: 1991 Altitude: 400.41 Nputral Density1125.0 Day: 335 Longitude: 66.30 1.200E+14

Univ Time: 1125 Latitude: 26.68

Column Parameters I Column Display i integration ParametersLength: 2.88 Display LengthOrigin Direction 2.88 Number of Pcints

X: 0.51 Theta: 90.0 Top View (XY Plane) 50

Y: 0. Phi: 0.0 1 Front View (YZ Plane) Spacing of Points

Z: 2.00E+04 I Right Side View (XZ Plane) Leg

Point Density Along Column I

Distance from Density I Column Density

Column Origin 9.744E+19 I 5.16CE 2C1.27

(a)

I Neutral Column I Update DoTable HELP!

I Density Problem:spree

Time into Absolute Date Orbital Position Total Abient

Mission Year: 1991 Altitude: 430.41 Neutral Density

1125.0 Day: 335 Longitude: 66.30 1.20C7+14Univ Time: 1125 Latitude: 26.68

Column Parameters I Column Display integration ParametersLength: 2.88 i Display LengthOrigin Direction I 2.88 Number of Points

X: 0. Theta: 90.0 1 Top View (XY Plane) 50

Y: 0.51 Phi: 90.0 I Front View (YZ Plane) Spacing of PointsZ: 2.OOE+04 I Right Side View (XZ Plane) Log

................................................................................

Point Density Along Column I

Distance from Density I CoIunn Censity

Column Origin 1.158E+17 i 6.299E-'71.27

(b)

Figure 7.8 Column density screens for the computation of the column density(a) along the nozzle axis and (b) normal to the nozzle axis.

Nozzle parameters for the other thruster nozzles were also determined. EPSATscreens describing each of the nozzles are shown in figure 7.9 through 7.12.

117

CL.nge Nzzle NozzI- I Upuate DoFarj C. P'

Nozzle Name: .n Line 1N A uI" ysis I Protlm: sprkce

N'zzL ... .e,: > ---- N.rural l .

Position Spre. Angles U; t Vect or Species Abundarce

X: 3.0 Theta: 90.0 X: 1.0 Acd Species -

Y: 0.. Phi: C.0 Y: 0.0 Delete Species n2 I.Co

Z; 20000.0 Z: 0.0------------ --------- Input L-rameters ----------------------

Length: 1.200E-02 Stagnation Ternp: 1.730E+02Exit Radius: 3.230E-03 Stagnation Press: 1.700E+06

rx-t Mach Number: 6.940Et00------------ -------- Derivea Parameters----------------------

Tr..at R adius: 3.2267-04 Number Flow Rate: 3.009E22

Thrust: 0.959 Mass Flow Rate: 1.40CE-03

Area Patio: 10c. Gamma: 1.4u------------ ------ Density Frur the Nozzle- ------------------

S Spherical Cooro Cartesian Courd

X: . Rho: C. X: -. otal Neutral

Y: 0. r:eta: 0. -> Y: 0. Density

7: 2.CC0E-S4 Phi: 0. Z: 2.000E'04 1.931E,24 Leak?arame'uers

Figure 7 9 EPSAT screen showing nozzle parameters for one nozzle of the 1N in-line thruster.

Cnange Nozzle I Nozzie I Update DoTable HELP!

Nozzle Name: Pn ?lane i Analysis I ProhL'em: spree

Nozzle ---- Nuzzle Direction ---- Neutral Relative

Position Spher. Angles Unit Vector Species Abundance

X:. Theta: 90.C X: 1.0 Add Species

Y: 0.1 Phi: C.0 Y: 0.0 Eelete Specirs n2 1.002: 20000.0 /: 0.0

- -pu Parameters-----------------------

.engtn: '.2:CE-C2 Etag:uation Tenp: 1.730+02

Exit Raois: :.0000-02 Stagnat ion Press: 4.3O0E*iOo

x't Mach Number: 6.630E-0:.eriveu Parameters----------------------

rc'a: Radi is; . l3hE-23 N_:rtlor Fow Kte. . ,., .22

n,: st: 2.B3 M ov; low Rate: 1.1b $5-C3

Are. Rat c: 61.9 Gamrm a: .40

------------- ------ Do .-sity Fr ,rr. tne Nozzle ------------------

Or-g-n Spherical Cocro Ca rtesian Cocrd

. Roc: 0. X: 0. Total Neutral.eta: 0. -. Y: 0. Density

2: 2.2,:0004 Phi: C. . Z: 2.000i>04 6.002E-23

Figure 7.10 EPSAT screen showing nozzle parameters for one nozzle of thein-plane thruster.

118

Change Nozzle I Nozzle I Update Do'able HELP!Nozzle Name: Out of Pla I Analysis I Proble7: spree

Nozzle ---- Nozzle Direction ---- Neutral Relative

Position Spher. Angles Unit Vector Species AbundanceX: 0.0 Theta: 90.0 X: 1.0 Add Soe.:ies

Y: 0.0 Phi: 0.0 Y: 0.0 Delete Species n2 >.CZ: 20000.0 Z: 0.0

------------- -------- Input Parameters----------------------Length: 1.955F-02 Stagnation Temp: 1.730E-O2

Exit Radius: 1.150i-02 Stagnation Press: 1.15C7 'O

Exit Mach Number: 8.730E+00------------- ------- Derived Parameters---------------------Throat Radius: 6.823E-04 Number Flow Rate: 9.10E22

Thrust: 2.95 Mass Flow Rate: 4.236E-03Area Ratio: 284. Gamma: 1.40

- Density From the Nozzle------------------Origin Spherical Coord I Cartesian Coord

: 0. Rho: 0. I X: 0. Total Neutral

Y: 0. Theta: 0. I-> Y: 0. DensityZ: 2.00E+04 Phi: 0. 1 Z: 2.000E+04 4.529F,23

Figure 7.11 EPSAT screen showing nozzle parameters for the out-of-planethruster.

Change Nozzle I Nozzle , JUdaze DoTabie HELP!

Nozzle Name: Yaw I Analysis i Probiec: spree

Nozzle ---- Nozzle Direction Neutral Relative

Position Spher. Angles Unit Vector Species AbundanceX: 0.0 Theta: 90.0 X: 1.0 Add Species

Y: 0.0 Phi: 0.0 Y: 0.0 Delete Spocies n2 1.00Z: 20000.0 Z: 0.0

------------- -------- Input Parameters----------------------Length: 2.99CE-02 Stagnation Temp: 1.730E02

Exit Radius: 1.150E-C2 Stagnation Press: 2.100E,035Exit Mach Number: 9.250E+00------------- ------- Derived Parameters---------------------Throat Radius: 5.964E-04 Number Flow Rate: 1.634E+22

Thrust: 0.531 Mass Flow Rate: 7.599E-04Area Ratio: 372. Gamma: 1.40

------------- ----- Density From the Nozzle ------------------Origin Spherical Coord I Cartesian Coord

X: 0. Rho: 0. I X: 0. Total Neurrai

Y: 0. Theta: 0. i-> Y: 0. Density

Z: 2.OOOE+04 Phi: 0. I Z: 2.OOOE+04 8.09 ' E-22

Figure 7.12 EPSAT screen showing nozzle parameters for one nozzle of the

yaw thruster.

119

A 2 1/2 kg per hour leak in one of the thrusters has been reported. The

parameters of the 1 N in-line thruster, with a lower pressure, define a nozzle

that loses gas at this rate. The EPSAT screen describing this nozzle is shown

in figure 7.13. Note that this nozzle gives rise to 0.5 N of thrust. Figure 7.14

shows the neutral densities about the subsatellite due to this leak. At the high

potential point, EPSAT computes the ionization traction to be 2718, which is

much greater than 1. Therefore, the leak is expected to cause a bulk

discharge.

C:.ange Nozzle Nozzle i Upiate CoTable HELP!

:.3zzie Name: Leak Analysis Problem: spree

;ZLe ---- Nczzl eI rect Io, . ---- Ne'tral RelativeSSphe. Anglcs Unit Vector Species Abundance

X: C. et : 9"." X: 1.0 Add Siecies

Y: . Phi C. : 0.0 Delete Species n2 1.00

Z: 20O0 .0 : 0.C--- --- --- --- --- -- rr.z :;r metrs -------------------------

Le:.ctt: i., C t~. -2 Staqnat cn Tempt: . 30E C2

iLx_- Radi..s: 3c.23 i-3 Sagnatiorn Pre-ss: 8.5COE'05Z.A<i- ath Nu.-br_-: 6.94051-0

-------- - --- r d ara.eter - ----------------------rrca Pac-l5 3.226;-04 Number Fiow Rate: ..5C5',22

: 0.479 Mass F'luw Rate: 6.999- 4

A at : 1 . Camma: 1.40--------- ty - -:-- - the Nzzle- ------------------

. i CO2ru ,arLcsiar Coo, j

: - . : $ . ) X : C . ct a l N u ' t L r a '' %. .neta: 0. '-> Y: C. Density: . , ' $. .: 2. 00 L- 4 9.654E,23

Figure 7.13 EPSAT screen showing nozzle parameters used to describe thethruster leak.

120

0sDen sty Wti.

(a)

10 0Cos festwith Lea,

-4

44 4

(b)Figure 7.14 Neutral densities due to "leak". (a) is a 3-dimensional Plot. and(b) is a contour plot.