VEHICLE/ENGINE Integration Issues are explored for orbit transfer vehicles (OTV's). The impact of space basing and aeroassist on VEHICLE/ENGINE integration is discussed. The AOTV structure and thermal protection subsystem weights were scaled as the vehicle length and surface was changed. It is concluded that for increased allowable payload lengths in a ground-based system, lower length-to-diameter (L/D) is as important as higher mixture ration (MR) in the range of mid L/D ATOV's. Scenario validity, geometry constraints, throttle levels, reliability, and servicing are discussed in the context of engine design and engine/vehicle integration

Bergeron, R. P.

Brown, J. R.

Cooper, L. P.

Florence, D. E.

Michel, R. W.

Vinopal, T. J.

Weldon, V. A.

English

NASA Technical Reports Server

VEHICLE/ENGINE INTEGRATION 
L. P. Cooper, Moderator,  NASA Lewis Research Center 
Tim Vinopal ,  Boeing Aerospace 
D .  Florence, General E l e c t r i c  
Roy W.  M iche l ,  A e r o j e t  Techsystems Company 
J. R.  Brown, P r a t t  & Whitney A i r c r a f t  
Bergeron and V .  A .  Weldon, Rockwell I n t e r n a t i o n a l  Corpora t ion  
https://ntrs.nasa.gov/search.jsp?R=19850008699 2020-03-20T20:37:39+00:00Z
Tim V i  nopal  
Boeing Aerospace 
As a systems i n t e g r a t o r ,  Boeing recognizes t h a t  t h e  main p r o p u l s i o n  system has 
a profound a f f e c t  on v e h i c l e  development c o s t  and schedule. S i g n i f i c a n t  engine 
we igh t  growth o r  unplanned changes i n  performance c a p a b i l i t y  have impo r tan t  i m p l i -  
c a t i o n s  i n  v e h i c l e  des ign  and m iss i on  cap tu re .  
Agreement i s  needed on man-rat ing requi rements  as these w i l l  g r e a t l y  a f f e c t  
v e h i c l e l e n g i n e  i n t e g r a t i o n .  As a minimum, e l i m i n a t i o n  o f  a l l  s i n g l e  p o i n t  f a i l u r e s  
r e q u i r e s  re-examinat ion o f  a e r o a s s i s t  concepts which r e q u i r e  l a rge ,  r e t r a c t a b l e  
engine nozz les.  P l ac i ng  t h e  nozz les  behind t h e  hea t  s h i e l d  moves l a r g e  deployed 
payloads i n  f r o n t  o f  t h e  shield-making P/L r e t u r n  imposs ib le .  The manned t r a n s f e r  
cab i s  sma l l  enough t o  e i t h e r  f i t  behind t h e  unmanned a e r o a s s i s t  dev i ce  o r  have a 
k i t t a b l e  hea t  s h i e l d ,  depending on a e r o a s s i s t  concept.  P r e l i m i n a r y  r e l i a b i l i t y  
ana lyses i n d i c a t e  t h a t  a s i n g l e  engine i s  unable t o  meet manned m iss i on  r e l i a b i l i t y  
goa ls .  An i nc rease  i n  t h e  number o f  engines corresponds t o  a decrease i n  per form- 
ance and an inc rease  i n  maintenance requi rements .  Performance analyses c u r r e n t l y  
show a 5000 t o  7000 l b  engine t h r u s t  range as optimum; however, t h e  c o s t  a n a l y s i s  
i s  expected t o  move t h e  optimum t o  a l e v e l  above 7000 I b s .  The h i g h  c o s t  o f  space 
based maintenance may have t h e  dua l  e f f e c t  o f  i n c r e a s i n g  t h e  t h r u s t  l e v e l ,  and 
d e r a t i n g  t h e  engine components t o  reduce t h e  amount o f  engine maintenance requ i r ed .  
VEHICLEIENGINE INTEGRATION ISSUES 
Q. FROM A PRIME CONTRACTOR STANDPOINT WHAT ARE KEY VEHICLEIENGINE 
INTEGRATION ISSUES? 
IMPACT OF ENGINE INTEGRATION ON CONFIGURATION DEVELOPMENT 
(DEVELOPMENT TIME, DDT&E, AND PERFORMANCE). 
r IMPACT ON MAN RATING AND MISSION RELIABILITY (OPERATING 
COST). 
Q. HOW DOES SPACE BASING IMPACT VEHICLEIENGINE INTEGRATION? 
MODULAHIZE ENGINE INSTALLATION AND/OR CRITICAL COMPONENTS 
TO ALLOW EFFECTIVE ON ORBIT SERVICING. 
HIGH SERVICING COSTS (- $20,00O/HR) MAKES DERATING ENGINE FOR 
LONG SERVICE - FREE LIFE ATTRACTIVE. 
Q. HOW DOES AEROASSIST IMPACT VEHICLEIENGINE INTEGRATION? 
ENGINE NOZZLE RETRACTION REQUIREMENT INTRODUCES SINGLE- 
POINT FAILURE MODES. 
r LARGE, HIGH EXPANSION RATIO ENGINES DIFFICUI-'7 TO SHIELD FROM 
FREE STREAM FLOW. 
F i gu re  1 
231 
ORMMIAL PAGE ISi 
OF POOR QUALITY 
EFFECT OF ENGINE RELIABILIIY ON SYSTEM RELIABILITY 
OTV P R O P U L S I O N  S Y S T E M  R E L I A B I L I T Y  
Figure 2 
Fresh Look Lifting Brake Designed for Space Assembly 
STS COMPATIBLE OTV MOUNTED 
USING SHUTTLE F lX lURES 
O l ' /  CAN RE EITHER GROUND 
BASEL) OR SPACE BASED 
NO NOZ7LE RETRACTION REOUIRED 
c,noss'r n w  ACCOMPLISHFD BY  
SLIDING 0 T V  ON I3AILS 
COI'JTllOL W I l I I  AEROOYNAMICSURFACES 
& FCS 
COMBINE BEST FEATURES OF LIFTING 
BRAKE & AMOTV TO INCREASE U D  
AND REDUCE SCAR WEIGHT 
SPACE ASSEMBLED PREFABRICATED 
COMPOSITE- PANELS 
RIGID OR FABRIC REUSABLE TPS 
LARGE PLANFORM AREA REDUCES 
TEMPERATURES 
NO IMPINGEMENT PROBLEM 
Figure 3 
PRELIMINARY RESULTS OF VEMICLEIENGINE 
INTEGRATION STUDY 
@ DUAL ENGINE INSTALLATIONS FAVORED 
RELIABILITY VS. OPERATING COSTS 
a ENGINES IN 7000 LB + TO 15000 LB + SIZE RANGE CURRENTLY FAVORED 
@ FUNCTION OF HIGH EXPANSION RATIO NOZZLE EFFECTIVENESS 
@ ENGINE DERATING WlLL INFI-UENCE SIZING TRADE 
@ AVERAGE MISSION COST WlLL BE SELECTION CRITERIA 
@ NON RETRACTABLE NOZZLES FAVORED FOR M A N  RATING & MISSlON RELIABIL.ITV 
@ PUTS PAYLOAD IN FRONT OF HEAT SHIELD 
TREAT MANNED MISSIONS AS UNIQUE AND INTEGRATE HEAT SHIELD WITH 
MANNED MODULE 
F i g u r e  4 
D .  Florence 
General Elect r ic  
Numerous propulsion subsystem re la ted parameters impact the AOTV 
configuration development and ult imate performance. However, the major 
f i r s t  order parameters appearing t o  have the g rea tes t  impact a r e  engine 
spec-ific impulse, Isp ,  propellant  mixture r a t i o ,  M R ,  and packaging volume 
a n d  length required f o r  the engines and associated plumbing, Figure 1 .  
I t  was demonstrated in Reference 1 t ha t  1 )  improved spec i f i c  impulse (443 
t~ 480 sec )  provides the l a rge s t  benef i t  f o r  both s ing le  s tage  and two 
s t a ~ e  A0TV's9 2 )  f o r  the s ing le  s tage  A O T V ,  the combined e f f ec t s  of a 
srrtalier hydrogen tank due t o  increased mixture r a t i o  and the shor te r  
vehicle due t o  use of multiple small engines, provides a benef i t  nearly 
as large as the increased Isp.  
For ground based AOTV1s, the payload weight delivery o r  round t r i p  capa- 
b i l i z y ,  i s  highly dependent on the AOTV dry weight. Other major parameters 
effectfng the payload magnitude include the engine Isp ,  low ear th  o r b i t  
pay load  capabi l i ty  of the launch vehicle,  and AOTV L/D. For the G E O  del ivery 
mission, the vehicle L / D  has a minor impact on payload del ivery ,  f o r  the 
r o u n d  t r i p  G E O  mission, L / D  i s  more important and f o r  polar del ivery ,  even 
more important, Reference 1 .  A s ing le  s tage  38f t  G E O  del ivery vehicle 
w i t h  propellant tanks sized f o r  a mixture r a t i o  of 7 and a s ing le  engine 
was described in Reference 1 .  Except f o r  the advanced engine ( I sp  = 
477 sec ,  MR = 7 ) ,  t h i s  vehicle u t i  1 i  zed s ta te-of  - the-ar t  techno1 ogy . Si g-  
n i f i c a n t  subsystem weight reductions a re  possible by incorporating advances 
projected due t o  s t a te -o f - the -a r t  advances, Reference 1 .  The improved payload 
delivery of these l i gh t e r  vehicles i s  i l l u s t r a t e d  in Figure 2 ,  and compared 
to  previous AMOOS r e s u l t s ,  Reference 2 .  
Configuration variations of the 38 f t  G E O  delivery vehicle identified 
in Reference 1 ,  were explored for  a Six Hour Polar Mission to determine 
effect  on payload weight/length, Figure 3. Here, i t  i s  noted that incor- 
porating an a f t  conical frustum angle of l o  resul ts  in increased pay load  
length. Lessor frustum angles are expected t o  produce even longer payloads, 
however, the axial center of gravity requirements become less  a t t rac t ive  
and more body f lap (heavier) must be added to trim the vehicle a t  the  desired 
angle of attack. The longer payload lengths are produced by the larger 
propellant mixture rat ios .  Additional payload length i s  obtained by blunting 
the nose, however, the loss of L / D  reduces the payload weight delivery capa- 
b i l i t y .  In th i s  evaluation, the AOTV structure and thermal protection sub- 
system weights were scaled as the vehicle length and surface are changed. 
Hence, we conclude that  for  increased allowable payload lengths in a g r o u n d  
based system, lower L / D  i s  as  important as higher MR in th is  range of  mid  
L / D  AOTV's. 
References 
1.  Florence, D .  & G .  Fischer, "Moderate Lif t  to  Drag Aero Assist",  
presented a t  the NASA Lewis Research Center Conference on Orbit 
Transfer Vehicle Propulsion Issues, April 3 & 4, 1984. 
2 .  Program Development, NASA Marshall Space Flight Center, "Orbit 
Transfer Systems with Emphasis on Shuttle Applications - 1986-1991", 
NASA TMX-73394, 1977. 
V E H I L L E  
L j l) 
, -1 
Mk ) TANK S I Z E  1 
- , VEIIICLL _ - _  V E I I I L L F  
S I Z E  WEIGi lT 
ENGINE S I Z E  ENGINE S I Z E  
& & 
NUMBER NUMBER ,/ 
Figure 1 .  - Propulsion subsystem parameters with first-order impact on AOTV 
performance. 
Figure  2. - Mid LJD AOTV GEO delivery capability f o r  single-stage vehicles. 
F i g u r e  3. - Performance v a r i a t i o n s  o f  a  s i n g l e - s t a g e  A O T V  f o r  p o l a r  d e l i v e r y .  
Roy W.  Michel 
Aerojet Techsystems Company 
The Aerojet pos i t ion  i s  t h a t  the  r i g h t  approach t o  advanced OTV pro- 
p u l s i o n  i s  with small mult iple engines. I n  con t ras t  t o  the  other  engine 
con t rac to r s ,  Aerojet has se lec ted  a nominal design t h r u s t  of 3000 lbF. 
The small,  mult iple engine approach has several advantages, notably 
t h 3 t  crew sa fe ty  and mission success a re  assured because of engine-out cap- 
a b i l i t y  and t h a t  highest performance in  a given length i s  obtained with 
srn231 engines. Length i s  important both f o r  earth-based OTVs and aero- 
maneuvering OTVs, and higher performance means g rea te r  payload capab i l i ty .  
Of several options f o r  manned O T V  r e l i a b i l i t y ,  only one provides 
the  necessary r e l i a b i l i t y  and i s  p r a c t i c a l :  redundant engines. Other 
options are  f a r  more cos t ly  or  depend on back-up modes t h a t  simply do not 
e x i  st. 
The 3000 lbF t h r u s t  engine develops about 4 I b F  sec/lbM higher per- 
f o ~ m a ~ c e  than the  15,000 1bF engines within a given length,  by v i r t u e  of 
higher area r a t i o .  For the  l a rge r  engine t o  achieve the  same performance 
reqwircls an addit ional  th ree  t o  four f e e t  of length and two or  th ree  exten- 
dable nozzle segments. I n  an aeromaneuvering vehicle these  extendable seg- 
melots must a l so  r e t r a c t  during passage through the  atmosphere and thus con- 
s t i  t u t e  s ing le  point f a i  l ure modes. 
With mult iple 3000 1 b F  t h r u s t  engines the  whole mission model can 
be performed, e f f i c i e n t l y ,  by a s ing le  propulsion system. Large space 
st , -uctures (LSS) a re  accelera t ion- l imi ted  and have a t h r u s t  requirement of 
503 t o  2500 lbF, which i s  met by one or  two engines t h r o t t l e d .  Many pay- 
loads a re  in the  3000 IbM c l a s s ,  which a lso  requi res  one or two engines. 
H i g h  energy payloads and manned aeromaneuvering vehicles requi re  10,000 t o  
12,000 I b F  t h r u s t ,  obtained by a four engine configurat ion.  
Xero je t ' s  approach t o  space-based maintenance i s  t o  design the  
en;ine t o  be a space-replaceable u n i t ,  which i s  most p laus ib le  f o r  small 
engines. If  an engine component needs r e p a i r ,  the  whole engine would be 
removed and returned t o  ea r th ;  r e p a i r s  would be made by s k i l l e d  tech- 
n i c i a n s  and the  engine re t e s t ed  t o  assure i t s  operation and performance. 
The several advantages of the  small ,  mult iple engine approach t o  
OTV propulsion have a l i f e  cycle cos t  benef i t  on the  order  of $1 Bi l l ion .  
Altogether, the  advantages and potent ia l  cos t  savings prove t h a t  the  r i g h t  
approach t o  advanced OTV propulsion i s  with small ,  m u 1  t i p l e  engines. 
ADVANTAGES OF 
SMALL, MULT PLE ENG 
@ CREW SAFETY AND MISSION SUCCESS 
ASSURED 
@ HIGHEST PERFORMANCE FOR GIVEN 
LENGTH 
@ MORE PAYLOAD CAPABILITY 
@ GREATER MlSSlON FLEXIBILITY 
@ REAL SPACE-BASED MAINTENANCE 
@ SAVES $1 BlLLlON 
Figure  1 
ONS FOR 
OTV REL 
RELIABILITY 
REQUIREMENT D LIFE BOAT \ R = .999 E RESCUE VEWlCLE 
Figure 2 
GHEST PERFORMANCE FOR 
490 r 
GIVEN LENGTH 
PC F E Isp 
2000 3K 1200 484.1 
ROCKETDVNE 2000 15K 1300 483.8 
ENGINE LENGTH, IN. 
F i g u r e  3 
GREATER 
PAYLOAD THRUST, ibF # ENGINES 
LSS 500-2500 1 O R 2  
(THROTTLED) 
MANNED 9,500 4 
(AEROMANEUVERsNG) 
SMALL ENG NE MEANS REAL 
SPACE-BASED MA NTENANCE 
Figure 5 
SMALL ENG NE APPROACH 
SAVES $1 B 
VALUE 
@ WEIGHT -40 M 
@ PERFORMANCE 400 M 
F i g u r e  6 
241 
J.  R .  Brown 
P r a t t  & Whi tney  A i r c r a f t  
Prat t  & Whi tney  A i r c r a f t  b e l i e v e s  t h a t  s e v e r a l  s i g n i f i c a n t  i s s u e s  e x i s t  
i n  the e n g i n e / v e h i c l e  i n t e g r a t i o n  a rea .  These i s s u e s  f a l l  i n t o  t h e  g e n e r a l  
c a t e g o r i e s  o f  : 
o s c e n a r i o  v a l i d i t y  
o geomet ry  c o n s t r a i n t s  
o t h r o t t l e  l e v e l s  
s r e 1  i a b i  1 i t y  
o s e r v i c i n g  
We b e l i e v e  t h a t  one eng ine  canno t  be o p t i m i z e d  t o  c o v e r  a l l  p o s s i b l e  
per."turb;stions o f  t h e s e  i s s u e s .  Ra the r ,  t h e  i s s u e s  must  be r e s o l v e d  i n  a 
c o o r d i n a t e d  e f f o r t  between t h e  e n g i n e  and systems c o n t r a c t o r  and o n l y  t h e n  can 
t h e  eng ine  c o n f i g u r a t i o n  be s e l e c t e d .  
IS CURRENT SCENARIO VALID? 
Space based 8 T V  
Prope11ant depot 
rganned GEO missions 
Serbstantial LEO-GEO traffic 
E.ow thrust deployment missions 
Only one type OTV 
blew driver mission (e.g., lunar lander) 
F i g u r e  1 
242 
WHAT ARE ENGlNE 
GEOMETRY CONSTRAINTS? 
Available length 
@ Available diameter 
Vehicle total thrust required 
Number of engines 
F i g u r e  2 
WHAT THROTTLE LEVELS ARE REQUIRE[)? 
Steps I%, 10%, 100% 
Continuous I%, 3% to 100% 
Mixed 1%, 3% to 10%, 100% 
What response rate are required? 
'WHAT ARE ENGINE REQUIREMENTS 
DURING AEROASSIST MANEUVER? 
-- 
a) Nonfiring 
Firing 
Thrust level , response 
Extendable nozzle position 
a Engine environment 
'Thermal 
Flow field 
F i g u r e  4 
6110\SJ DOES ENGINE INFLUENCE 
VEHICLE RELIABILTY? 
a Number of engines 
Mission %ogic (number of failures to abort) 
Barzk-up dependency 
bkiain engine 
Rescue mission 
Figure  5 
WHAT ARE VEHICLE SERVICING 
REQUIREMENTS/CAPABILBTIES? 
Routine maintenance (after every mission) 
Periodic maintenance (after every 10 missions) 
Unscheduled maintenance 
Back-up mission logic 
One spare vehicle 
One spare + components 
Two spare vehicles 
Etc. 
Dependency on diagnostic systems 
The engine contractors need to know: 
1. How does vehicle limit engine geometry? 
2. What is engine required to do? 
Primary mode 
Aeroassist mode 
3. What propulsion system reliability is needed? 
4. What engine servicing capability is available? 
F i g u r e  7 
2 45 


Vehicle/engine integration

Vehicle/engine integration

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