Electrical Power Requirements Analysis

‘NA iJ-TE-7’- - - Q ) H i E C ‘ i E I C A L ECYEE N77-32233 h Z Q L ~ E i E B E Y 1 L A Y A L Y S I E . SIIJGIE € A I L U S E TOLE:.-.NT E N T B Y (SASA) 36 F BC AO3/rlE A01

CSCL 10E Uncl as G3/20 U9310

Single Failure Toierant Entry

Mission Planning and Analysis Division September 1977

https://ntrs.nasa.gov/search.jsp?R=19770025289 2020-05-01T03:58:55+00:00Z

77 -FH-44

SHUTTLE QROGRlIH

JSC-13046

ELECTRICAL PO#ER REQUiRENENTS ANALYSIS

SINGLE FAILURE TOLERANT ENTRY

9y Marvic D. Pipher , Paul A. Green, and Debbie F. Wolfgram McDonnell h u g l a s Technical Serv ices Co., I n c .

JSC Tash Moni tor : Sam 0. M a y f i e l d

Approve

p- /t!z-4/ 7 .&L=@

Ronald L. Berry, C h i s -. ~

Mission Planning and Ana;, & % v i s i o n

Nat ion31 Aeronautic; and Space A d m i n i s t r a t i o n

Lyndon B. Johnson S p x e Center

Mission Planning and Ar,alysis D i v i s i o n

Houstoti, rexas

September 1977

Section

CONTEWTS

Page

1 . 0 2.0

3.0

4.0

5.0

6.0

7.0

SYMBOLS ...................................... vi

SWpllARY ...................................... 1

INTRODUCTION ................................. 2

SYSTEM DEFINITION DATA ....................... 4

3.1 Fuel Cell characteristics ................ 4 3.2 Circuit Description ...................... 4 3.3 Inverter Characteristics ................. 5 3.4 Orbiter Electrical Loads ................. 5 3.5 Payload Electrical Loads ................. 5

GUIDELINES AND ASSUMPTIONS ................... 8

4.1 Guidelines ............................... 8 4.2 Assumptions .............................. 9

SINGLE FAILURE TOLERANT ENTRY ANALYSIS ....... 5.1 Analysis Definition Data ................ 13 5.2 Analysis Results ........................ 14 5.3 Analysis Uncertainties .................. 15

CONCLUSIONS ................................. 18

REFERENCES ................................... 30

13

i i i

TABLES

TABLE PAGE

4 . 1 - 1 AVIONICS CONFIGURATION FOR SfT ENTRY ............ 12

5 . 1 - 1 SFT ENTRY ANALYSIS . TIME LINE .................. 20

5 . 2 - 1 LOW VOLTAGE LIMITS . SFT ANALYSIS USING NEW POWER P LANT ...................................... 27

5.?-!1 EPS ANALYSIS TAPE INFORMATION ................... 28

5.3-i LOW VOLTAGE LIMITS . SFT ANALYSIS USING 5000 WJR POWERPLANT ( INFORMATION ONLY) .............. 29

i v

TABLE

3.1-1

3 .3 -1

5.2-1

5.2-2

5.2-3

5.2-4

5 .2 -5

5.2-5

F ISURES

PAGE

FUEL CELL PERFORMANCE CHARACTERISTICS-SEPS PROGRPM .... 6

INVERTER CHARACTERISTICS . SEPS PROGRAH ............... 7

FUEL CELL 1 SOURCE POMER . CURRENT. AND VOLTAGE ........ 21 FORWARD BUS 2 . 2. and 3 VOLTAGE PROFILES .............. 22

H I D BUS 1. 2. AND 3 VOLTAGE PROFILES .................. 23

'FT BUS 1. 2 . AND 3 VOLTAGE PROFILES .................. 24

ESSENTIAL BUS 1. 2. and 3 VOLTAGE PROFILES ............ 25 PANEL 14. 15. AND 16 BUS VOLTAGE PROFILES ............. 26

V

SY MBO LS

APU DF I ECLSS EOM E PS FA FCP FC S FES FF FM GPT: G SE H2 H20 K41 NASA N/A 09 OMS 9V 02 PL PL B PSIA RC S RH RJD RMS X P S ?FT W D B ' '9QYE d I

SSME TACAN TC s TV VDC

AUXILIARY POWER UNIT DEVELOPMENT FLIGHT INSTRUMENTATION ENVIRONMENTAL CONTROL AND L I F E SUPPORT SYSTEM END OF MISSION ELECTRICAL POWER SYSTEM FLIGHT AFT (MDM) FUEL CELL POWERPLANT FLIGHT CONTROL SURFACE FLASH EVAPORATOR SYSTEM FLIGHT FORWARD (MOM) FREQUENCY MODU LAT I ON GENERAL PURPOSE COMPUTER GROUND SUPPORT EQUIPMENT HYOROGEN WATER K !LOWATTS NATIONAL AERONAUTICS AND SPACE ADMINISTRATION NOT APPLICABLE OPERATIONAL FORWARD (MDM) ORBITAL MANEUVERING SYSTEM ORBITER VEHICLE OXYGEN PAY LOAD PAYLOAD BAY POUNDS PER SQUARE INCH ABSOLUTE REACTION CONTROL SYSTEM RIGHT HAND REACTION JET DRIVER REMOTE MAN1 PULATOR SYSTEM SHUTTLE ELECTRICAL POWER SYSTEM ANALYSIS COMPUTER PROGRAM SINGLE FAILURE TOLERANT SHUTTLE OPERATIONAL DATA BOOK SHUTTLE ORBITER UVIF IED RECORDS FOR CONSUMABLES EVALUATION STOPROLL SPACE SHUTTLE MAIN ENGINE TACTICAL AIR NAVIGATION THERMAL CONTROL SYSTEM TELEVISION VOLTS DIRECT CURRENT

v i

ELECTRICAL POWER REQUIREMENTS ANALYSIS

SINGLE FAILURE TOLERANT ENTRY

By Marvin D. Pipher, Paul A. Green, and Debbie F. Wolfgram McDonnell Douglds Technical Services Co., Inc.

'.O SUMMARY

This document presents the results of an analysis of the orbiter

electrical power system for the case of a single failure tolerarlt

[SFT) entry.

Power System (SEPS) analysis computer program (Ref. 1).

to permit assessment of the capability of the orbiter systems to

support the proposed entry configuration and to provide the data

necessary to identify potential constraints and limitations.

The analysis was performed using the Shuttl- Electrical

It was performed

Three contingency modes have been identified which would require

an SFT entry.

the losr, of two fuel cell powerplants, while on orbit. The arlalysis

is presented in three parts, as follows:

This analysis addresses an SFT entry resulting from

o Electrical Power system configurdtion definition

o Guidelines and Assumptions for the analysis

r) Discussion of the results of the analysis

The results of the analysis indicate that, even under near optimum

conditions, the fuel cell power demand will exceed the tested operating

capacity of 16 kw, and that various electrical components may

experience voltages below 24 VDC. Insufficient data i s available to

assess the implications of these limit violations, or to perform

a worst case analysis.

configuration cannot be shown t o be safe for entry.

Without this data and analysis, the SFT

2.0 IPJTROWCTIOW

Three f a i l u r e mode% have been postulated that require a minimum Orbi ter

power entry (Ref. 2) . The f a i l u r e modes are the loss o f two f u e l

cel ls, the loss o f one freon loop, and the loss o f cabin pressure.

Lcss of tw fue l c e l l s l i m i t s the capab i l i t y t o provide e l e c t r i c a l

power t o that avai lable Prom a s ingle fue l ce l l . Loss o f a freon

loop r e s t r i c t s power due t o the resu l t ing degradation i n heat transport

and heat re jec t ion capabi l i t ies . With loss o f cabin pressure, and

the necessity t o maintain an 8 ps ia environment, avai lable power i s

l im i ted by reduced a i r cool ing and cryogenic oxygen f low r a t e constraints.

Two e l e c t r i c a l equipment

as possible means o f dea

these, known as the sing

guidance, f 1 ight control

entry configurations Rave also been i d e n t i f i e d

ing w i th these contingencies.

e s t r i n g configuration, provides the minimurn

The f i r s t o f

and display electronics necessary t o accomplish

a safe entry and landing, but provides no hardware or software redundancy.

This i s the minimum power config , rat ion f o r a safe ent ry and landing. The

second configuration i s the s ingle fa i lu re to lerant (SFT) mode. This

configuration provides l imi ted redundancy i n the areas o f guidance

and f l i g h t control, at the expense o f increased power and heat re jec t ion

demands.

Heretofore, the s ingle s t r i n g configuration has been the design

baseline.

i n the c r i t i c a l f l i g h t control areas, however, the SFT configuration

i s being considered as a revised baseline.

performed t o evaluate the capabi l i ty o f the e lec t r i ca l power

generation system t o support t h i s configuration and t o i d e n t i f y

DiJe t o concerns regarding the lack o f f a i l u r e tolerance

This analysis was

2

possible bus voltage limitations and constraints.

The analysis was performed with the XPS computer program, using the

basic avionics configuration of Reference 2, with equipment usage

variations derived through a series o f meetings with flight control

division personnel.

3

3.0 SYSTM DEFINITIOW DATA

The EPS, as inodeled by the SEPS computer program, consists of the

orbiter electrical power generation and distribution subsystems. The

system generates required orbiter electrical power and delivers it to

end item loads in accordance with a predefined equipment time line.

The sections which follow define the EPS system characteristics and

the system loads used in this analysis.

3.1 Fuel Cell Characteristics

The fuel cell performance characteristics, used in the analysis,

are those illustrated in Figure 3.1-1. These characteristics were

derived from powerplant performance predictions and test data,

and include extrapolations beyond the operational capabilities

of the powerplant. The portion of the curve lying between 2 and

72 kilowatts (kw) is based on predicted initial powerplant performance,

as defined in the Shuttle Operational Data Book (Ref. 3). The

portion of the curve ranging from 12 to 16 kw is predicated on

the wsiJ:ts of powerplant tests performed i n Pupport of SFT entry

analyses. The portion of the curve above 16 kw is an extrapolation

for purposes of analysis and may not be representative of actual power-

pl ant performance.

3.2 Circuit Description

The SEPS circuit, used in the analysis, i s described in Reference 4.

This description i s in conformance with Shuttle Operational Data Book

(SODS) amendments 59 and P2-144 (Refs. 3 and 5). The guidellnes and

assumptions used In formulating the circuit are discussed, in detail,

in Reference 6.

4

3.3 Inverter Characteristics

The inverter performance characteristics used I n the analysis

are shown i n Figure 3.3-1.

3.4 Orbiter Electr ical Loads

The orbi ter e lec t r i ca l equipment l i s t , u t i l i z e d i n the performance

o f t h i s analysis, i s that defined i n Reference 7 for operational

orbiters. This l i s t corresponds t o the OV-103 equipment l i s t

contained i n SOD6 Amendment f’ (Ref. 3).

3.5 Payload Electr ical Loads

No discrete payload e lec t r i ca l equipment was u t i l i z e d i n the performance

of t h i s analysis. The maximum power al location f o r maintaining

a safe payload, however, was applied as a constant power load

on aux i l ia ry bus A, a t stat ion 693 (Ref. 8).

5

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4.0 WIDELIIS A#) ASSU#gTIO#S

The guidelines fallwed d the assunptims ma&, i n the fmwlation

of the WS enalysis,,are the subject of this section.

4.1 6uidelincs --

The guidelines used in fowulating the single failure tolerant

entry analysis m e as follows:

a. The vehicle malsed is an OV-103 configuration orbiter on

an operational fli@t.

b. The single failure tolerant entry resulted fm the loss of

f w l c@lls 2 itnd 3.

c. The electrical pmer distribution subsystem i s reconfigured

such that fuel cells 2 and 3 are isolated, while fuel cell

1 i s supplying power to main buses A, B, and C.

d. The analysis i s initiate0 with fuel cells 2 and 3 Cactivabed

and fuel cell 1 supplying all power.

e. The analysis covers the interval fm three hours prior to

deorbit until the orbiter i s Cactiwated 4.56 k r s later.

f. Critical avionics equipment i s ccnfigud in accordance with

Reference 2, including those changes identified therein as

being requested by the WAS. The awionics canfigarration used

is that presented in Table 4.1-1.

8

The fol lowing assumptions were made i n formulating tk single

f a i l u r e t o l e r m t entry analysis:

a. Two hundred watts of payload safing pmw are applied as a

constant pasrer load on auxi l iary bus A.

b. No obss k i t i s instal led.

c. Thermal conditioning of the orb i ter i s impractical due t o

thermal lag and the t ia te available. Therefore, a mmrinal

a t t i tude and a $0 to 50 degree beta angle w e r e used t o define

thermal control heater operation.

d. With fuel c e l l p,werplants 2 and 3 off , their produet water

l i n e heaters are assumed to cycle wi th 4W duty cycles.

e. WO nose gear s t r u t actuator heater i s instal led.

f. A11 conmunication requirements are sa t is f ied using S - k n d direct. Therefore, no Ku-Band equipment i s required.

9. The fol lowing heaters were disabled i n accordance wi th information

obtained from f l i g h t control d iv is ion personnel:

(1) Forward RCS thruster heaters

(2) Forward RCS l i n e and tank heaters

(3) A f t RCS vernier thruster heaters

(4) FES port feedwater l i n e heaters

(5) Waste H$l dump l i n e heaters

9

Matte H$ dump nozzle heaters

Potable H@ ckrrag l i n e h a t e r s

Potable H@ dueip nozzle heaters

02/H2 purge l i n e heaters

R#S a m heaters

SsbdE c o n t ~ ~ l l e r heaters

Ku-band deployed assembly heaters

Ku-band cable heaters

PLB and RplS fv camera heaters

PLB and RMS pan ti lt assembly heaters

6al ley Hfl heaters

02 cryogenic heaters (one set)

A i r data probe heaters

h. F l igh t deck l i gh t i ng was configured i n accordance with in fomat ion

received fm C. D. WheelwigRt/EU5. The configuration used

was as follows:

(1) Forward instrument l i gh ts - 40% o f max p m r

(2) Glareshield f loodl ights - 20% o f max poker

(3) Forward numerics - 50% o f rnax power

i. One hydraulic c i rcu la t ion pump was operated from the s ta r t

of the analysis u n t i l the beginning o f the pre-&orbit aerosurface

deflect ion checks at deorbit minus 2:30:00.

operated from deorbit minus 1:30:00 u n t i l the GPC's were configured

fo r descent a t deorbft minus 00:35:00.

It was subsequently

j. TRe brake skid power units tiere 8ctiwetd f iw minutes prior

to touchdown.

TPUKE 4.1-1 AVIOWICS COWIWWATIOW FOR ST EW7WY

DESCaI PTIOW

CENTRAL PROCESSIN6 UWITS-IWPUT/OUfPUT PROCESSORS WLTIPLEXER/DEPILILTIPLEXERS - ff WLTIPLEXER/DMULTIPLEXERS - FA MJLTIPLEXER/DB4JLTIPLEXER - PI. DISLAY WCIVEU UNITS

MASS #woBY UHITS PCU M T E R U N - 3 #ULTIPL€XER/G- IULTIPLEXER - OF WLTIPLEXER/DEWLTIPLEXER - OA HULTIBLEXER/DEHULTIPLEXER - FLIGHT DECK

DISPLAY n ~ c m I e s UAIITS/CRT DISBUY uwm

M A I N T E W E LOOP RECORDER U I D E W S I G N COPJDIVIOWERS SIGWAL COWOITIOWIffi UWITS IWERTIAh Wt!A!%RmEtdT UWIfS AIR DATA TRBwsIwcER BSSEWBLIES RATE 6YcITRo ASSEMBLIES ACCELEROMETERS

RUDDER PEDAL TRANSDUCER SSEMBLIS SPED BRME THRUST C r n L L % R S AEROSURFACE SERVO AD9PLIFIERS R W T I O W COWTROL SYSTEM RJD'S S-BAWD Ft4 'IRAWSBIITT'ER S-BAWD M E R M P L I F I E R S-BAMD RE-AMPLIFIER S - W D TRMSPOWDW S-$APT NETWORK S I G N PROCESSOR T M i

ROTATIONAL HAW) comoLLms

MICROWAVE SCAN BEMI LANDIWG SYSTEM RADAR ALTIMETERS AUDIO TERMINAL UWITS

HORIZONTAL SITUATION INDICATORS ALrHA MACH INDICATORS ALTITUDE VERTICAL VELOCITY INDICATORS FUEL CELL PC;IERPLANTS APU/h"QAOLICS SYSTEMS OF1 S\,lEM E,' 3s

AlTITUDE DIRECTOR INDICATORS - FORWARD

WHBEFt K T I #

2 3 3 1 2 3 0 1 3 3 1 0 0

13 2 3 3 3 1 1 1 3 4 0 0 0 1 1 2 2 2 2 2 2 2 2 1 3

N/A rmw

12

5.0 SIWGLE FAILURE TOLEaablT ENTRY W N Y S I S

This E 6 analysis was prfomned using the

prog-am (Ref. l), agerating with ingut data k i w d from the $OURCE

data base. The SEPS gmgram -1s the orbiter electrical ptmw

g@n@ration end distribution subsysttms and, working to a gmlefiml

electrical equipment tiate line, gemrates circuit analysis data

bas& on a nodal solution technique. The !3OlRCE data base i s

a magnetic tape file containing a corngosite of all orbiter electrical

equipment, along witn activity blocks defining the nominal usage

of that equipment. The data base provides the capability to select

the equipment complement o f any desired orbiter along with the

nominal usage of that equipment as a function of specific flight

parameters.

modify the nominal usage data, contained within the SOURCE data

base, i n accordance with the requirements of this specffic contingency

situat ion.

analysis computer

In performing this analysis, it was necessary to

5.1 Analysis Definition Data

The following definition data was used as input to this analysis:

a. SOURCE Data Base Input Data.

(1) Orbiter - OW-103 (Operational)

(2) Crew Si telshif t Description - 4/Single Sift

(3) Payload Support Equipment - N/A

(4) OMS Kits/RH Manipulator - N/A

(5 ) Payload Effects on Orbiter - None

13

b. Deviations from nominal SOURCE data base equipment usage

were made as required t o conform t o the guidelines and assump-

t ions o f Section 4.

c. The t ime l ine used i n t h i s analysis of the SFT ent ry contingency

i s presented i n Table 5.1-1.

5.2 Analysis Results

The resul ts of the single fa i lu re tolerant entry analysis are

as follows:

a. Figure 5.2-1 presents fue l c e l l 1 power, current, and voltage

f o r the SFT entry contingency, as analyzed. A review o f t h i s '

f igure indicates that fue l c e l l power can be expected t o range

from 11.92 kw t o 16.90 kw, with-an average value o f 14.06 kw.

Furthermore, the peak power point can be expected t o occur

a f te r stoprol l , when the three hydraulic c i rcu la t ion pumps

are activated.

was 16.14 kn. This l e v e l was achieved 1.33 hours p r i o r t o

deorbit, while the payload bay doors were closing.

The maximum power observed p r io r t o touchdown

b. A fur ther review o f Figure 5.2-1 reveals that the fue l c e l l 1

voltage can be expected t o range between 27.40 and 28.55 VK,

with the minimum occutring a f t e r s topro l l , when the three hydraulic

c i rcu la t ion pumps are activated.

p r i o r t o touchdown was the 27.58 VDC value which corresponds

t o the pre-touchdown peak power point.

The minimum voltage experienced

14

c. Figures 5.2-2 through 5.2-5 present voltage profiles for the

forward, mid, aft, and essential buses, as analyzed. Figure

5.2-6 is a corresponding plot of the voltage levels experienced

at circuit breaker panels 14, 15, and 16. For purposes of

analysis, constraint limits were set on each o f these parameters

and the parameters w e monitored for limit violations. The

limits used, the lemst values experienced, and the numbers

of constraint violations are tabulated in Table 5.2-1.

should k observed that, for tR@ a#Kt part, the limits used

represent the expected worst case voltage levels at the local

buses. These are the levels which were used in selection

of the wire sizes necessary to insure component interface

voltages &we 24 Mlc, under worst case conditions. The single

exception was the essential bus voltage limits, which were

set to 27.0 WE.

It

d. Tapes created in the performame o f this analysis are itemized

in Table 5.2-11.

5.3 Analysis Uncertainties

The following major analysis uncertainties should be considered

when interpreting the results of this analysis:

a. The fuel cell curve utilized in this analysis is representative

of a relatively new powerplant. Predictions are that an older

powerplant will produce a somewhat lower voltage for any given

power lewel. A review of existing data (Ref. 3) indicates

15

that t h i s decrease w i l l be on the order o f 0.65 VM: a t 12 kw

and that it m a y be greater a t higher power lev@ls. A supple-

mentary analysis has been performed using powerplant charaeteris-

t i c s thought t o be more representative o f a 5000 hour fue l

c e l l but, since no supporting fue l c e l l t es t data is available,

the results must be considered as tentative, a t best. The

results, however, are presented i n Table 5.3-1 f o r information.

b. Them1 control syst@nl (TCS) heaters were not cycled i n t h i s

analysis, but atere averaged over time. The peak power effects

of mul t ip le heaters being on concurrently, therefore, w i l l

not be apparent f r o m t h i s analysis. As a result, actual maximum

power levels may be s ign i f i can t ly higher than those indicated

i n Figure 5.2-1.

heater power application, see Reference 9.

For a discussion o f the effects o f :oncurrent

e. The heater usage factors used i n t h i s analysis were those

of a nominal a t t i tude wi th in the beta angle rang@ o f 40 t o

50 degrees. The effects o f t h i s contingency occurring a t a

worst case at t i tude and beta angle were not considered.

d. I n general, the SEPS computer program does not model wir lng

to discrete e l t x t r i c a l end-items below the ?oca1 bus level.

To acquire data below the local bus level, the component

interface voltages must, therefore, be calculated from analysis

local bus voltages, using actual wire lengths and sizes,

and the corresponding load power values.

e. Fuel c e l l parerplant operating characteristics above 16 kw

16

are indeterminate. The operating characteristics usd above

this 9ewl are based on extrapolations from test data and

may not be representative of actual fuel cell operation.

f . The TCS heater usage factors usd in this analysis are based

on preliminary and partially complete thermal analysis data.

g. Iuo KS heaters wre active in this analysis when below 400,OOo

f@@t .

17

6.0 CONCLUSIONS

The following conclusions may be drawn from this analysis:

a. Both fuel cell power and bus low voltage limits will be violated

during an SFT entry, even under near optimum conditions.

b. lnsufficient data i s available to allow a worst case analysis

or t o permit an assessment of the impact of limit violations.

The analysis indicates, however, that, during an SFT entry under

nomipal ta cold thermal conditions, a catastrophic fuel cell

failure may occur along with random component failures.

the available information indicates that the magnituo. of these

failures will be a function nf the specific thermal conditions

and the accumulated operating time on the one remaining fuel

cell.

In addition,

c. To perform a more definitive analysis, the following actions

are required:

1. The characteristics of a near SOU0 hour fuel cell must be

determined from 12 KW to the maximum operating limit (fuel

c ~ l l failure).

?. Oetailed heater duty cycles must be determined for the worst

case attitude and beta angle.

3. Critical items of electrical e?itipment must be identified

and their low voltage operating limits must be determined.

4. Line resistances must be determined between a l l ?oca1 buses

and the end i tem equipment.

d. Without a worst case analysis based on the above data, the SFT

configuration cannot be shorn to be a safe mode of entry.

19

TABLE 5.1-1 SFT ENTRY ANALYSIS - TIME L I N E

TIME ( HHMMSS )

000000

003000 003500 01 3630

025000 025015 030000

030641 033828 034328

041935 042035

0 4 2 1 35 343335 L

EVENT

BEG I N ANALY S I S

FCS CHECKOUT

CLOSE PLB DOORS

RCS MANEUVER

DEORBIT

APU SYSTEM ON 400,000 FEET

(TCS HEATERS OFF)’ TOUCHDOWN STOPROLL

APU SYSTEM OFF EOM

ACTIVITY BCp NAME

ORBIT COMMON (ORB-DEORB) RCS ATTITUDE CONTROL OEORBIT PREP 1 PLB DOORS OPEN

SFT CRYO HEATERS

APU DESCENT APU DESCENT PLB DOORS OPEN PLB DOORS CLOSE FWD RCS MANEUVER FWD RCS MANEUVER

NOMINAL HTRS BETAz40-50

MISS ION COMMON (GSE-GSE)

ORBIT COMMON (ORB-DEORB) DESCENT COMMON (DEORB-GSE DESCENT COMMON (DEORB-SR) OMS MANEUVER RCS ATTITUDE CONTROL DECRBIT PREP 1 PLB DOORS CLOSE

OMS MANEUVER APU DESCENT

DESCENT (DEORB-400 KFT)

DESCENT (DEORB-400 KFT) DESCENT (400 KFT-SR) NOMINAL HEATERS BETA-540-5

DESCENT (DEORB-SR) DESCENT (400 KFT-SR) POSTLANDING (SR-GSE)

MISSION COMMON (GSE-GSE) DESCENT COMMON (DEORB-GSE

DESCENT (LOW ALT OPS)

APU DESCENT

SFT CRYO HEATERS

- ON

X X X X X X X x

-

X X

X X X

x X

X

X

X

-

OFF -

X r

X X

X X X

X

X

X

X X

X X X X -.

For purposes of analysis

20

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TaQE W E --

DATA

IWTWACE 1

INTERFACE 2

PLOTS

TABLE 5.2-11

E 6 ANALYSIS TAPE 1WOBbBB;TIBRI

X 1 5227

X15144

X15175

X15202

28

29

7.0 REFERENCES

1.

2.

3.

4.

5.

6.

7.

8.

9.

HDTSCO: User’s Manual f o r the Shuttle E lect r ica l Power System Analysis Computer Program - SEPS. (Unpublished) January 1976.

R I : Minimum Power Deorbit and Entry-Single Fai lure Tolerant (SFT). Memo. No. SAS/MR&I-77-039, March 1977.

Operational Data Branch: Shuttle Operational Data Book, Volume I - Shuttle Systems Performance and Constraints Data, JSC-08934, hendment 59, May 1977.

MDTSCO: SEPS Orbiter E lect r ica l Power Dis t r ibut ion System Model - Revision 2. (Unpublished) July 1977.

Operational Data Branch: Noti f icat ion. JSC-08934, Amendment P2-144, June 1977.

Shuttle Operational Data Book Data Change

WTSCO: SEPS C i rcu i t Definit ion. Memo. No. TM-1.4-7C-16, July 1975.

MDTSCO: Shuttle Program Orbiter E lect r ica l Equipment U t i l i za t i on Baseline.

Shuttle Program Office: Specification.

R. M. Swalin: Technique f o r Handling Cyclic Heaters i n ConsumaSles Analyses. Memo. No. FM26 (77-82), Apr i l 1977.

JSC-12561, Change I , May 1977.

Space Shuttle f l i g h t and Ground System JSC-07700, Vol. X, Rev. B, Change 39, May 1977.

30 NASA-JSC