An overview of NASA's low thrust liquid chemical propulsion program is presented with particular emphasis on thrust system technology in the ten to one thousand pound thrust range. Key technology issues include high performance of cooled low thrust engines; small cryogenic pumps; multiple starts-shutdowns (10) with slow ramps (approximately 10 seconds); thrust variation - 4/1 in flight and 20/1 between flights; long life (100 hours); improved system weight and size; and propellant selection

Priem, R. J.

English

NASA Technical Reports Server

CHEMICALPROPULSIONTECHNOLOGY
RichardO. Prlem
NASA Lewis ResearchCenter
NASAts Low Thrust Liquid Chemical Propulsion Program is represented in the following charts.
They have been used in presentations to several of the NASA Overview Committees in the past
couple of months and are In a program plan that contains most of this Information, so they
represent an overall view of the chemical propulsion technology program. This presentation
pertains to thrust system technology in the ten to thousand lb. thrust range. This chart
schematically shows the elements of the propulsion system, with tanks, structures, and engines
included In the program.
LOWTHRUSTCHEMICALPROPULSIONTECHNOLOGYPROGR_NI
!
I
D
J
T,R,s
iO-i,O00LBS.
31
https://ntrs.nasa.gov/search.jsp?R=19800022947 2020-03-21T17:35:45+00:00Z
This chart Shows that the new chemical program that we are talking about is in the ten to thousand
lb. thrust range and • speclf|¢ impulse which is close to 500 sac. The State-of-the-art drops
off very rapidly in the low thrust range. Thls Is why we are speaking of a dedicated thrust
system in the low thrust range. There are other programs in the thousand lbs. and higher thrust
range that are used for orbital transfer. I am not discussing that today.
PROPULSrONSYSTE/4SFORLSS
3ooo- __
2000- EP
; CONCEPTS
lOOO--," ADV..D_
CHEHICAL
Specific 600
Impulse,
Set. 400-
300- _.O.A.
200.
I00 I i I :
0.1 1.0 10 I00 1000
THRUST,I.br,.
32
The obJective of the program, shown In this chert, is a technology program as Dick Carlisle
mentioned before: We want to provide the tools, data, and analyses to allow propulsion system
designers and people that do mission studies to optimize the actual system. We also need to
develop new techniques that are required for this low thrust system, including throttling of the
chambers, how to cool very small chambers, pumps and packaging of the complete systam. The pro-
gram also has to demonstrate the technology readiness, both in the components and possibly in the
total propulsion system.
OBJECTIVESOFLTCPPROGRAM
TECHNOLOGY PROGRAM THAT:
0 PROVIDES TOOLS (DATA, ANALYSIS, DESIGN PROCEDURES)
To DEFINE PROPULSIONSYSTEMPERFORMANCE,
WEIGHT, SIZE, ETC, IN TERMSOF ENGINEDESIGN
VARIABLE (THRUST, PRESSURE,ETC,)
O DEVELOPSNEWTECHNIQUESNEEDEDFORLSS MISSIONS
(THROTTLING, COOLING, PUMPS,PACKAGING,ETC,)
O DEMONSTRATESTECHNOLOGYREADINESS
(COMPONENTSANDPROPULSIONSYSTEM)
33
The elements of the program are shown In this chert. The fundamental technologies ere studies to
establish what the engine requirements are. Cooling studies are listed, because cooling Is a
severe problem, especially at low thrust. We think that high pressure might be required, so we
have included pumps, bearings, and seals. Also Included are throttling concepts. In the components
and engine systems area, we have to design and test these components to demonstrate that they are
truly feasible and that the critical technology is available. We also need simulation tests of
the engine systems for the most difficult technology. This is where we are not sure how far we
have to go (how far we have to get into slmulatlon testing as part of the program). The last step
would be for a breadboard system to demonstrate that the complete technology Is ready for a full
system development. Again, we are not sure at this time whether a breadboard system would be
required, but have Included It in the program.
The key issue that we see in the low thrust chemical propulsion is high performance of cooled low
thrust engines. You have already seen that we have achieved low performance, low I._ down in
these low thrust ranges. Now we must demonstrate hlgh performance and long Ilfe, w_ch requires
cooling. We believe this will require small cryogenic pumps, and they are not available in the
state-of-the-art. Multiple starts appears to be a requlrement for perhaps ten starts and
shutdowns, with a slow ramp such that the structure is not damaged by a sudden change in acceleration.
Thrust varlatlon could be 4 to 1 in flight so that constant g's are malntalned as propellant is
used up. For different missions, it is possible that a thrust range of 20 to 1 would be needed.
Very long llfe is requlred. At very low thrust levels, a hundred hours of engine firing time
is needed to complete a mission. We also have to improve the system weight and size. The final
Item is the selection of propellants, because defferent propellant systems have different char-
acteristics that might be desirable for different missions. These are the key issues as we see
them right now.
KEYTECHNPLOGYISSUESFOR
LOWTHRUSTCHEMICALPROPULSION
m m n
0 HIGH PERFORMANCEOF COOLED- LowTHRUSTENGINES
O SHALLCRYOGENICPUMPS
O MULTIPLESTARTS- SHUTDOWNS(10) WITH SLOWRAMPS
(_10 SECONDS)
O THRUSTVARIATION - 4/1 IN FLIGHT AND20/1 BETWEEN
FLIGHTS
O LONGLIFE (100 HOURS)
0 IMPROVEDSYSTEMWEIGHTANDSIZE
0 PROPELLANTSELECTION
34
ELEMENTSOFLOHTHRUSTPROPULSIONPROGRAM
0 FUNDAMENTALTECHNOLOGIES
STUDIES TO ESTABLISH ENGINE REQUIREMENTS
COOLING STUDIES & TESTS
PUMP, BEARINGS, SEALS, FABRICATION STUDIES
THROTTLING CONCEPTS
o COMPONEI_TS& ENGINESYSTEMS
DESIGN & TESTING OF COMPONENTS TO DEMONSTRATE
FEASIBILITY OF CRITICAL TECHNOLOGY
SIMULATIONTESTS OF ENGINESYSTEMSWITH MOST
DIFFICULT TECHNOLOGY
o BREADBOARDSYSTEMTEST
DEMONSTRATIONOF TECHNOLOGYREADINESSTO ACHIEVE
LIFE, PERFORMANCE,THROTTLINGANDMULTIPLESTART
35
This chart includes funding level. This Is from a planning document end therefore, It shows
fiscal years from when we get the increased funds that are required to accomplish the program.
The first year could be the fiscal 81 or 82 program. Currently we have payloadpropulsion
interactions studies going on. You will hear about these later. There are cooling concepts
and pump analysis studies that are being conducted, and you will also here about these later.
The next phase of the program will consist of component design, fabrication and testing in
the critical technology areas. This would lead to life and performance tests to demonstrate
the technology. The final phase, which I am not sure will be required, would include a complete
breadboard of the system. Breadboard means not necessarily lightweight, but creation of the
condltlons that are needed for an engine. This would demonstrate that the technology for a
complete system $s avaIlab|e. We definitely would carry it through the design phase of the
program. The final phase consists of altitude testing, because of the very large expansion ratio
nozzles which have not been demonstrated to date.
That summarizes the chemical propulsion program as we see it now. The Funds shown are what we
think are required to do the program. This funding level is in the F'Y82budget. We are planning
for it. On the other hand, it Is roughly double or triple the funds we have available right now
for the program.
LOWTHRUSTPROPULSIONPROGRAM
FISCALYEAR
PRIOR 1 2 3 4 5 6 [
i
FPAYLOAD- PROPULSION
FU._IDA.MENTAL INTERACTIONSTUDIES
TECHNOLOGY
ICOOLINGCOI:ICEPTSI
PUMPANALYSIS,DESIG._I,FABIrIVES.
i
L_{ COMPONENTDESIGN& FAB_
ENGINECOMPOI'IENTsYsTEM& L_ COMPONENTSTESTINGI! • ._,--_--,
I__ IL-L-_-PERFORMA,_ICE& ,
:THROTTLING-TESTS
BREADBnARD ,,
SYSTEM FA_ ASSFI,!BLEI
LT,TESTI ::
,,.,.
36


Chemical propulsion technology

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