AlAA 89-2503 Shuttle4 Main Propulsion System Development from the Space Transportation System Shuttle R. Burg, T. Gaynor and D. Brakeville Rockwe I I I n te rn at io nal Downey, CA

AI A A/AS M E/S A E/AS E E 25th Joint Propulsion Conference

Monterey, CA / July 10-12, 1989

For permission to copy or republish, contact the American Institute of Aeronautics and Astronautics 370 L’Enfant Promenade, S.W., Washington, D.C. 20024

by Roger Burg,* Tim Gaynor,** and Donna Brakevillel

Hockwell International Space Transportalion Systems Division

I)owney, California

Abslract __

Shuttle-C providcs the Space Ttansportation System (STS) with a hcavy-lift cargo capability that is a low-cost derivative of the cur- rent Spacc Shuttle. This systeni can deliver 100,ooO to 150,oOO pounds of payload to low earth orbit within 4 years of authority to procccd. Shuttle-C will share the cxistitlg STS launch iacilities at Kcnnedy Space Ccntcr (KSC).

The configuration of the Shuttle-C main propulsion systcm (MI’S) incorporates eithcr two or threc Spacc Shuttle main engines (SSMES). Since the Shuttle-C MPS is common with thc STS MPS in

Infroducliun

Shuttle-C, an unmanned cargo vciiiclc, is a natural low-cost derivative of the Spacc Shuttle. This growth vcrsion of the STS can deliver IW,ooO to 150,ooO pounds of cargo lo low earth orbit from KSC Launch Complex 39 within 4 years of go-ahcad. It offers early heavy-lift capability with low development cost by taking advantagc of thc existing STS qualification data base. The propulsion system has options for either two or three Space Shuttle main engines, depending on mission requirements. The basic two-engine Shuttlc-C isdepictcd in Fig. 1, and the boattail and propulsion system in Fig. 2.

niaintainutl based on the extensive STS data base for its MPS evolution. The maior contributor to this data base was thc Main Propulsion Tcst

6 I

EXISTING ET

h ORBITER BOATTAIL

SME’S

EXISTING SRB’S

Fig. 1 Bosic Shurlle-C elemenls.

*Program director, Shuttle-C

iMembcr of technical staff , Mechanical and Propulsion , *‘Program manager, Advanced Engineering

Engineering

I

4

Fig. 2 Uonccail und propulsion .sys/em LJciliie niajur STS elemenrs.

17-inch iiropcllant discunnects, have bccn ccrrified; dcvelopmcnt arid qiislification for hydraulic subsystems and the propcllant lermi- m1 chain test h a w bccn conipletcd. This forindation, along with dcmon~tialcd ground iintl launch operations, provides confidencc i l lat Shorllc~C program objectives can bc inct.

A Shintlc-C "rcfercncc configuration" MPS that mccts program rcquircmcnts l i as bccn dcfincd. The thrcc-cnginc xrsion marimizcr the lhcavy~li f t capacity oSthc vchiclc with an MPS design erscntially ~nini i ini i to flit STS orbiter and e ~ t ~ i n n l lank configurations. Although miciion l u n c h costs arc minimizctl by llic two-cnginc vcr- sion, iiiorc dcvclopment activities arc rcquircrl. i\dditianally, potcn- tial spin-off bcocfits from Shuttle-C to the STS program and its ei'o- liitioii arc atfiactivc, a is the oppoitimity to u t i l i x Sholi lc~C iis a flighl tc(t bed for STS modifications, since it is unmanned.

Shullle-C MPS Rcquircments and Design Cliaraclerislics

Like lhc STS MPS, tlic Shuttlc-C MPS augments the impulse ccqoiccmcnt (providing approximately 20 pciccnt of this first-stagc total impolrc) from lift-off through solid rockci boostc~. (SRR) scpa- lalion. After SRll separation, tlic MPS contiimcs to opcratc until the rcfercncc main cnginc cutoff (MECO) condition is satisfied. For tlic discct-iriswtioii Spncc Station mission, MECO I ICCLII~ with tlic vch-

11 57 nautical niilcs ai ii YClQcity of 25,900 feci per i ~ c o n t l and a flight pat11 anglc of 1.02 dcgsccs.

Sincc thc Sliottlc-C is cxpcndablc, S~VCIRI rcquircmcnts of the STS MPS system can be climinatcd. For cxamplc, the ~ c t ~ r ~ , - t o - launch-iilc (RT1.S) dump systcm is iiol nccdcd, since this abort mode woiild not be implcmcntcd. I n addition, a postkMEC0 liclium pwgc i ( not rcqiiiicd T h i s STS opcration iemovcs rcridud GO2 and GI12 liqiiids and gases from thc MPS lincs and engines to safc the system prior to reentry. For Slmttlc-C, helium is rcqitircd only for tlic SSME and 1.IF.5 pncumatic rystcm during ~sccnt.

Tlic niaxiniiini hc l i i i n i mass is required for an engine-out abort to orbit. 1st this scenario, eacli engine requires 48 lbrn of hcliim to mcet maximum osagc and cnswc that at least 900 psiti is maintained a i the prcssore icgiilatoi inlet. Thc inoniinal licliiini rcquircment for an STS niicsion is ;tppiosinmcly I65 Ibm, stored in two 4.7-cubic-foot ;,rid one 17.3-cubic-foot lank sets for each cnginc antl one 4.7-cubic-fool tank for pneumatic actuation. Eliminating t l i c post-MECO purge rcquircmcnt eliminates om 4.7-cubic-foot lieliiiin t ank per engine. Thc resulting Shotllc-C MPS schcniatic is shown in Fig. 3. 'The t!ircc- cnginc xrsion of Shuttlc-C requires csscntially ino inodification of tlic dcrign or proccdurcs associated with the cxlcrnal tank (ET) or Ininich facilit\.

Additional MI'S dclciions arcpossiblc i f a two-engine \,ciniol> of Sliottlc-C is uscd. Tor this configuration, SSME 1 antl IIIC iripporl systcnts associated with this cnginc ase rcmovcd. Thex dclclitim, also SIIOWII in Fig. 3, include mnoval of thc SShlE 1 1.02 and 1.1 12 f e d lincs, tlic LO2 blccd and pogo rccirculiition lincs, I.H2 rcciiculzi~ tion linc antl pump, and prcsswiZation lincs. Appropriatc ciiti I'it- lings will be required to closc out tliesccomponents. For cxamii lc. iin cnd cap for the dcletcd SSME I fccd line will be inoiint~tl iil l l i c manifold/cnginc Sccd lint intcrfacc. Also removed, but not cl i i i i \ i i i n Fig. 3, arc t l i c thrust vcctoi control, hydraulics, clcclsical iwwcr, Imliiim, G N z porgc, and cooling syslcms for Kngine 1.

Pciformancc analysis indicates that rcnioxtl of SSMI:. I r e d ~ ~ c c ~ the ET propcllant from approniniatcly 1,597,500 to 1.2hX.600 poiindz, which translalci 10 a rcdoction i n fluid hcad hciyhl of 191 inchcs i n tlic 1-02 tank and 259 inchcs i n the LH2 tank. This inoniiiiiil off-loadcd lank condition rcqeircsadditional fill sensors in tlic I?l_ 10 cnswc tliat 1propcr propcllanl qnantitics arc loaded bcforc flinlil

With scnso~s located at lhc 10o-pcrccnt fill location rool thc t w > . cnginc Shii~tlc-C, propellant loading fimc antl acciiracic\ ciin hc improvcd bccausc tlicrc is no need 10 load and tlicn drain hack limn IIIC IOO~perccnt propcllant lcvcl of tlic STS. Sincc inultiplc iciiwi i

wcictiscd in 11icllTcarly i n tIicShiirtl~program, maniil;icliiring pro- ccdurciaicalrcady inplacctoincorpoiatctliismorlific~ilion uitli Io\v risk and dciclopnicnt cost.

I

The SSME startup conditions dictate specific prcssurc :mil i c f i i - peratorc rangcn for propcllant~ at tlic cnginc inlet (Fig. 4). 011- lo;ding propcllant from thc ET, as \voilld occur for l l l c I w ~ c n g i c i c Shuttle-C configuration, rcducci thc hydrostatic I X C ~ S I I I C oi I . 0 2 hy 7.9psi and LH2 by0.7 psi, compnrcd to thcSTS. S111~llIc~~'~~rcii i irc rcqoircmentr wcic dctcimincd fimm hydrus1;rtic head, 1:11?1. u l l prcssure band, ambicnt prcssurc, and inslrumcntation linccrl' ' l l l l l l C ~ .

Acscssrncnts of startup prcssiirc wcrc bascd on fliglii t l i i i :~ 11on1 Slmttlc missions, from which the cliangc in erpcctcd l iciitl Iprc\wrc was subtracted. The cstimatwl Shotllc-C picssul-c/tc~iipcl--arriic cliirl

point represcnting anticipated loading conditions, :is dmin i n 1 h i 7

figure, lies within thc SSME modificd start box. The SSMI.' c:m \ l a i t at the conditions of ihc modified start box. Thcrcforc, 110 tnlocliVica. tion O F tlic S S M E or preprccsuriration systcin is rcqiiiictl I O iilloii proper cnginc startup of tlic two-engine configrilation

I n addition to satisfying cnginc start conditions, llic l \ $ < > ~ ~ , g i ~ configuration satisfics the net positive suction prcssurc (NPSP) rcquircmcnts during all ascent phases (Fig. 5) . Sincc t h e tli icc-cngmc Shuttlc-C would follow a similar ascent profile 10 tlial of l l i c STS with similar ET propellant-level quantities, thc NPSI' t in ic IKICC

d

L

VALVES

0 fROM HELIUM PNEUMATIC SUPPLY

.... ITtMS OELETEO FROM SHUllL€C

ITEMS O€LLIEO FOR 2 ENGINE CONFIG ONLY

....

LlUH

Fig. 3 MPS schematic (pneumatic system omitted).

LO2 L H 2

TEMPERATURE l’Rl - 1 7 3 . 5 R - 3 7

40.5 SHUTTLE-C 137.5’R. 42.9 PSIAI

ENGINE INLET PRESSURE IPSIAI

TEMPERATURE I D R ]

ENGINE INLET PRESSURE (PSIAI

PRESENT SHUTTLE IC0

0 PROPOSED SHUTTLE-C ICD

APH (SHUTTLE-SHUTTLE-C) 7.9 PSI APH (SHUTTLE-SHUTTLE-C) 0.7 PSI

tXPECTED MlhlMUM START PRESSURE 99 1 PSlA EXPECTED MINIMUM START PRESSURE 4 1 3 PSIA EXPECTED M A X I M U M START PRFSSUflE 101 3 PSIA EXPECTED M A X I M U M START PRESSURE 4 4 3 PSlA

FROM MPTA DATA, ENGINE CAN START AT AN LO2 INLET PRESSURE AS LOW AS 93.0 PSIA

Fig. 4 SSME can support bwer start pressures for the two-engine Shuttle-C.

3

3 ENGINES 140

I MINIMUM REOUIREO NPSP 20

‘ 0 20 1;O l&O 240 220 3dO 340 ab0 4$0 5d0 520 6; 620

Fig. 5A LO2 NPSP for lypical Shurrle and /or Shulrle-C rwo-engine con/iguration.

2 ENGINES LH

IPS11 NPZP

10

5 MINIMUM REOUIRED NPSP L

0 I t I I I I I I 1 1 I I I 0 50 100 150 200 250 300 350 400 450 500 550 600 650

TIME FROM SRB IGNITION ISECl

LH2 NPSP for typical Shrrtlle andfor ShutNe-C Fig. SA rwo-engme con/~gu,oc,on.

s l m w hcrc for the STS should also approximatr that of the ihrcc- enginc Shottlc-C.

iog. Major building blocks in this processarr described i n t l i i iscct ior with cxplanations of how they apply directly to Shuttle-C.

Anaiysia of tank ~xcssuie versus timc for thc two-engine configura- tion shown in Fig. 6 indicates tiid1 a large pressure overshoot in thc 1.02 tank starts at approximatcly t + 80 seconds and lasts IS0 sec- o n d ~ . This is caused b y the combination of a large initial ullage vol- time in thc tank and the ambient pressure dccay. Arnbicnt prcssorc cffccls mmt br considered bccaosc the LO2 ullagc prcssore is mca- surcd in psig and, aftcr t + 80 seconds. the vehicle is at an altitude of approximately 74,000 fcct, which corrclatcs 10 an ambient pressurc of 0.6 psia.

A possiblc solution lo this problem is to redcsign thc flow control valve area and possibly replacc these valves will, fined orifices r i ~ c d to climinaic the ovcrshoot. The Shiittlc program is currently consid- cring rcplacing the flow control valve with Fivcd orifices. I f this mod- ification is incorporated, a solution for Shuttle-C would bc to icdc- sign thcorificctocIin,inatcovcrshooi. Forcithcrcasc, thcsystcmcan be vcrificd with a longcr flight rcadincss firing and inathematiciil modcls that arc prcscntly available.

Incorporating these dcsign changes into thc well-proven STS main propiilsion system results in a net reduction in MPS weight com~)arcd to the current STS. This rcducrion will also Iowcr produc- tion cost, since fcwci components are required pcr vehicle, and- because these modifications introduce minimal dcvelopment risk- the dcvclopmcnt cost for this system can bc minimizcd.

Thc Main Propulsion Test Program was a schcdulcd SCI~CI 01 cryogenic tankings and cngiiic slatie firings dcsigncd to providc basic dcsign verification of the integrafcd PIPS and dcmonstrale baric interface conipatibilily of the flight and ground subsystems. I’ig. 7 sl~ows an carly static firing test of thc main propukion ICY! arliclc (MPTA). Fiflcen static firing test^ wcre pcrformcd at NASA!s National Space Technology Laboratories (now thc Stcnnis Space Center) i n Mississippi from April 1978 to January 1981. The h.1I’l-A used for testing coiisistcd of a partial orbiter, three SSEvIE’s, a n d an external tank. Tcst cases werc pcrformed for three-engine and two- enginc configurations (one engine out).

The orbiter hardware included a flight-configuralioa aft fuie- Page structiiie with its purge, vent, and drain subsystem and a c m - pletc MPS with rclatcd portions of the hydraulics and aYionics s u b - systems and the orbiier/CT separation subsystcm (le% pyrotccliriicr). The required flight and ground test imstrumcntation i ~ i i ) a150

provided.

T h c MPTA engines werc basically production conrigwniion. cxcept for MPTA-uniquc instrumentation and thc sub5li lul ion of dcvelopment nozzles for flight nozzles to allow full throttling in sciectcd firings. The ET was a flightweight tank that accoi~iniodiitcd dcvclopmcnt test instrumcntation and auxiliary iprcswrizition, drain, and vcnl provisions for both thc LH2 and 1-02 tanks.

TIic dclailcd cvaliiation and analysis of the tcst data indicaicil that all planned test objectives were accomplished. I n addition, c o n sidcrablc data werc obtained lildl pcrmittcd the dcvelopmrni of oprr- ationdl proccdurcs and rcsoliition of key dcsign issucs; thui. I ~ L ~ ~ C I -

STS Main Propulsion System Test Program

Thc STS main propulsion system was d e ~ l o p e d and ccrtificd by a coinhination of component, subsystem, and intcgratcd systcm test-

d

f,cr'lJi\i UL.L/\GiS PRESSURIS IPSiCIl REF 1'0 i\;O!;F CAP

... ..................... rerminul Draiii 'Xes:.

Table 1. STS chonges from MITA lesling. ~~~~~~~ . . . ~ ~ ~~~ ~~~~ -

Area of Concern Benefit -. . .~ . .~ LH? rccirculation pump Restart procedurc~~~mplif ied - ~~

I-Hz high-point bleed systcm

Pmpcllant loading

SSME inain fuel valve actiiatoiS Pixl)rcssuiization avcrshoot

Engine ready logic

Instrumcntation

~~~~~~

1,Oz drain flow rate

Inciting purgc

1.02 drain-back

1.02 slow f i l l

Fropcllant~levcl control

LH2 topping flow rate

1.02 vent undershoot

Sequencing proccdurcs modified Proccdurc to ininimizc propel- lant tcmpcraturc established Propellant chill-down and ini- tial fill procedurcs defined Heaters addcd to prevent freez- ing of hydraulic fluid Ground support equipmcm (CSE) modified to eliminate ET ullagc pressure overshoot Logic changed to minimize recycling Orbiter transduccrs insulated to minimizc drifts of pressure mcasurcmcms during cryogcnic operations Orifice installed at the CSE interfacc to avoid exceeding the maximum allowablc LO2 drain flow rate and rcdcsignl requalification of orbiter components Proccduies dcvelopcd that min- imize purge time and helium usage Variable LO: drain-back time before cngine stait demon- stratcd, allowing flexibility in KSC launch operations Software procedure devcloped to avoid potential geyscring Control software developed for the propellant replenishing Systcm Intcrface pressurc increased to mcct thc required tapping flaw rate Hclium injection added to ~ 0 1 1 - trol vcnt mlvc undcrshoot phenorncnon

Sevcral analytical models refincd and improved from tcst results, e.&, flight control, pogo. thermal, vibro-acoustic, structural loads, hydraulics, and MPS

-

lated flight configuration. Tests wcre run for three-engine configurations and cnginc-out cascs (two engines).

~~ ~~~

The ability o f ihc iintcgrated MPS to support an LLCO was veri- fied by cvaluation of the follwaing system charactcristics and functions:

~~~~ ~

ECO scnsor performance relative to response time and effects of bubblcs cntraincd in the liquid flow ~- Generation and propagation of cavitation bubblcs within thc inte- grated MPS

~~ ~

* Liquid residual rcquiremcnts aad ECO scnsor timing requiremcnts

Component friction prcssure losses and thc cffccts of two~phasc flow on thcse ~ a l u c s

LO2 propellant tempcraturc stratification

- ET/orbiter I7.inch disconnect performancc undcr higli flow rates './ Flow-induced vibration data for thc aft flex scction a1 high flow ratcs

Data from the first tcsts were used to cslablisbtli sure distribution during tcrminal drain The orbitcr/S available NPSP was then prcdictcd for both thc inain propulsion tcsi (MPT) and flight. The prcdictions show that NPSP rcquircmcnts can bcsatisficd whilcthcorbitcr ECOscnsor is used for l o d c v c l OLII-

off dmhg flight. Nominal LO2 icsiduals were also dctcrmincd. 'Thc tests also showed t!m, for MPT, thc NPSP rcquircmcnl? would he satisfied fora low-levelcuidfat the ECOscnsor bccauseof i l i c lack of v e l i i ~ l c accclcration cffccts on thc groun sciisor was addcd to thc tank for thc MPT t

Thc Shuttlc-C main propulsion system is identical to t h a t tchtcd intheTDT Thcreforc,thcShuttlc-Cpressurcloss, NPSF, cavitation, and ECO sensor response are deteimincd for both the thrcc-engine and ?so-cngine configurations (cnginc-out test runs).

Key Component 'Tests

MPS components were certified by a combination of analyses, componcnt-Icvcl tests, and systcm tcsts. Key componcni\ includc thosc in the propellant fccd, thc fill-and-drain, and t h ~ prupcllant prestart conditioning subsystems.

The propcllant feed subsystem delivers LO2 and L H l from thc ET to the SSME. This subsystcm also works with the fill-and-drain subsystcm to provide a flow path for filling and draining thc orbitcr and ET during ground operations. Major components in this subsys- tem are thc ET/orbiter disconnects, the propellant fecd niiiifolds. thc feed lines, and the prevalvcs. Thc fill-and-drain subsystcm uti- lizes the orbitcr feed system to supply propellants to fill thc ET from the ground. By performing this function in the revcrsc dircction, the subsystem also drains thc Shuttle. Thc LO2 and LH2 fill-and-drain subsystems are similarly dcsigned and consist of similar componcnts. Major components include the Fi!l-and-drain lines and thc fill-and- drain valves. The propcllant prestart conditioning subsystcm pro- vides the specified subcooled prestart propellants &!he cnginc inlets. Heat is removed from the orbiter and cnginc by recirculatinij t h c I H2 to thc ET and bleeding thc LO2 overboard. Major components for this subsystem includc thc LH2 rccirculation orbitcr/ET disconncct, thc l ine assemblies, thc valves, and the LH2 recirculation pumps.

d

All key components were tested at the component lcvcl 10 thc maximum cxtcnt practical, but final certification of thc components as a system requires an intcgratcd tcst, which wzis accomplishcd on thc MPTA. MPTA tcsting cxposed the componcnts In l h c full rangc offlow conditions and other operatingconditionsthat c a n w i bc re% sonably simulated at the component IcvcI. By maintaining thc cxist- ing Shuttle configuration and operating conditions, Sliiittlc~C com- ponents can be certified without repeating the expensive componcnt qualification tcsting and integrated system testing. Lxtcnsive cngine- outtcstingonthchlPTAprovidesancxccllcntdatabasc for ccrtifica- lion of the two-engine Shuttle-C. This approach to ccrlification results in low costs and high confidencc and eliniinatcs thc inevitable component redesigns that incrcasc costs and impact schedulcr. W

BATTLESHIP LINE I 1 7 IN.)

ECOSENSORS l A N D 2

N S O R S 3 A N D 4

SIMULATED FLIGHT FEE0 LINES A N 0 MANIFOLD I 1 7 IN. AN0 12 IN.)

ANTIGEYSER- LINE 13-112 1N.I

RETURN LINES I12 IN.) FILL A N 0 CONDITIONING TANK

FACILITY STORAGE

k ig . 8 LO2 terminal drain lesl conjigumtion.

.- Ground and I.aiinch Operations The processing flow for tlic first Shottlc-C, shown in Fig. 9, dif- fcrs from the Shuttle processing flow only in thc cargo clcment. The cargo element will bc processed through a ncw Cargo Elcmcnt Pro- cessing Facility (CEPF) or through the existillg Orbitcr Maintenance and Rcfurbishmcnt Facility (OMRF). The SRBS antl ET for thc Shuttlc-C will bc proccsscd at theelement level-in an identical nlan- ncr to the Shuttlc-in thc Rotation, Processiilg, and Storage Facility (RPSF) antl in thc Vertical Assembly Brlildirrg (VAB), respcctivcly. Integrated Shuttle-C operations-which includc assembly in the VAB, transfcr to thc launch pad on the Mobilc I.aunch Platform (MI.P), and launch from Launch Complex (LC) 39, Pad A or B-

Shottlc-C is an cnhancement of STS and will share many of the esisting STS raciliticr and resources, including the launch complcx. Slwttlc-C Iziunchcs and activitie5, howcvcr, must not intcrfcrc with the ongoing STS launch rchcdnle.

Dcca~isc Slriiltlc-C is similar to the cxisting Shuttlc, tlic two vehi- clcs can share the samelaunch complcxw'ithorit major modification. Supporting simultaneous opmations of two major programs from ihcsamc KSC facilitics, howcvcr, %,ill beachallcngc.

.J

CARGO ELEMENT WITH PAYLOAD VERTICAL

\ %-+, & PAYLOAD

EXISTING PAYLOAD \ PROCESSING BUILDINGS \

\

a& b \ Go ELEMENT PAYLOAD HORIZONTAL

\ OMRFORCEPF

-L %-- h2-%34$$$L&~ .~T?(I .~ ._

CARGO ELEMENT WITH PAYLOAD HORIZONTAL VABILCC

CARGO ELEMENT

= a l / / / ET

/TRANSPORTER

SRB SEGMENT/

& RPSF AND SURGE

v Fig. 9 Shritlle-C embedded in rhe exirling STS operalions flohl

~

I I L A U N C H CARGO ELEMENT PROCESSING I

will hc wry similar to Shuttle operations and will hc controlled frorn the cnisting Launch Control Ccntcr ( K C ) .

Proccssing timc lines haw been devcloped in dctail to support the top-lcvcl processing timc line shown in Fig. IO. The timc line indi- cates that lhe commonality and simplification of the MPS havc con- trihutcd to Shuttlc~C cost-effectiveness by minimizing ncw equip- ment, software, and proceduredevclopmcnt. Thecritical launch pad operations of propellant loading and prepressurization will be idcnti- cal to thc Shuttle for the three-engine configuidlion. For the two- cnginc configuration, these opcrations will hc modificd to account for thc cnginc deletion, lower propellant loading Icvcls, and incrcascd ullagc volume. These arc not major revisions and will not rcquire dcvclopment lcsting hcyond thc countdown dcmonstration test, which includes propellant loading, conductcd on all new STS "chicles. An cxlcndiul-duration flight rcadincss firing (beyond thc normal 15 scconds) wil l he conducted to certify the in-flight LO2 pressurization system for the two-engine configuration as mcntioncd previously, Checkout of the MPS is simplcr than existing Shuttle chcckout because of the system delctiuns for the Shuttlc-C.

As the program matures, the combined Shuttlc and Shuttle-C launch rate will makc the VAB a choke point and will require thc acti- vation of a new SRR buildup and stacking facility. MPS operations, howcvcr, will no1 hc affected. Facility activation and modification

schedules haw been developed to eliminate significanr STS impacts while supporting Shnttlc-C.

Summary __ L/

Thc Shuttle-C main propulsion system providcs high cunfidcnce and high rcliahility at a minimum dcvelopment cost. Tlrc thcee- engineconfiguration isessentially that iiow flying on Sholtlc, Icss the dump and incrting systems requircd for abort rcentr),. Thc IUO-

cnginc configirration rcquirci slightly morc developmarl bcciiiix of thc off-loaded ET propellants. Even licrc, however, thc MPT 1pm gram providcd a wcalth of dircctly applicablc data t l i a t lini hccn incorporated into thc system modcls.

Thc multitutlc of dci,clopmcnt issucs anticipatcd wi th a high- performance hydrogcdoxygcn cryogcnic system haw alrcady bccn solved. These range from the qualification of individnal C O I I I ~ ~ ~ I I C I I I S

through the propellant loading and conditioning opciations in thc launch countdown to thc end-burn shutdown. Of i>articulai imimr~ lance is the compatibility of Shuttlc-C KSC I.aunch Coniplcx 39 operations with thosc cu~rent ly utilized.

In summary, this background allows thc Shuttle-C l o progrcsi .smootldy to its schedulcd launch dntc of Dcccmbcr 1994.

L-]SRB PROCESSING I SRB RECOVER I

I I

, I r ET PROCESSING

I SRBSTACK 1 1 I

I

NON- CONSTRAINING

[/ET MATE

b c A R G 0 ELEMEi

PAD O P E R A T I O N S [ ~

, 1 4 0 10 20 30 40 50 60

WORKING DAYS (THREE SHIFTS]

MATEIINTEGRATION

~ M L P I P A D REFURB - 70 80

Fig. 10 Shurrle-C top-level processing lime line is supporled by .simpl&d / similar MPS processing.

8