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NASA Project Apollo Working Paper No. 1054
n
NATIONAL A E R O N A m C S AND SPACE A T I M I M I S m I O N
MANNED SPACECRAET CEIVIER
HOUSTON, TEXAS
c
October 26, 1962
NASA PROJECT APOIUI WORKING P
m NO., 1054
PROJECT AFOLlX
PRESSURIZED GAS REClCTION CONTROL SYSW
FU3R LITTLZ J O E I1
Prepared by :
Authorized f o r Distribution:
L
e i m e x. Faget
Assistant Director, Research and Development
K
NATIONAL AERONAUTICS AND SPACE A D M I N I S W I O N
MANNED SPACECRAlFT CENTER
HOUSTON, TEXAS
October 26, 1962
i
TABLE OF CONTENTS
Sections
Page
s u I 4 M A R Y . . . . . . . . . . . . . . * . . . . . . . . . . . .
INTRODUCTION
.....
SYSTEMANALYSIS..
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Test Apparatus .
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TestValves.. .
Reaction System Performance .
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SYSTEN SELECTION FOR LITPLE JOE I1 - .
Pressurized-Gas System Considerations .
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TESTPROGRAM......
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Comparison of Monopropellant and Pressurized-Gas Systems
FIGURES
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.................- ......
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RESULTS AND CONCLUSIONS
REZEBENCES
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LXST OF FIGURES
Figure
1
Comparative schematic diagrams of pressurized-gas
and monopropellant reaction control system
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Comparative i n s t a l l a t i o n of r.eaction oontrol system
i n L i t t l e Joe I1
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Nitrogen T-S Diagram
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Compressibility f a c t o r f o r nitrogen . . . . .
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Propellant a v a i l a b i l i t y . . .
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Nitrogen impulse characteristics .
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Propellant storage
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Nozzle performance .
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Regulation e f f e c t possible i n a blowdqm type reaction
. . .. - ... .
control system . - .
The three valves submitted for t e s t
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The Marotta MV 121 valve i n s t a l l e d i n thrust stand . .
Thruststand
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Carrier amplifier and recorder .
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Analog computer
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8 - c h ~ recorder
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Regulated and unregulated reaction 'control systebs
schematics
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R e l i a b i l i t y comparison f o r L i t t l e Joe 11 reaction
control system
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1
PRESSURIZED GAS REACTION CONTROL SYSTEM
FOR LITI'U JOE I1
SUMMARY
This paper presents t h e analysis and t e s t evaluation used t o establ i s h t h e f e a s i b i l i t y of a pressurized-gas reaction control system f o r
L i t t l e Joe 11. A comparison of a pressurized-gas system and a monopropellant system i s a l s o presented. The comparison includes considerations
of r e l i a b i l i t y , launch operations , ccjst, development time, and weight.
The pressurized-gas system o f f e r s decided advantages i n every considerat i o n except weight.
INTRODUCTION
A study of t h e control system for " L i t t l e Joe 11" has established
t h a t a combination of aerodynamic and reaction controls w i l l be needed t o
perfom a l l phases of each type of mission. The lack of s u f f i c i e n t aerodynamic control during the f i r s t t e n seconds of f l i g h t r e s u l t s i n a requirement of about 1000 pounds of s i d e force from t h e reaction control
system during t h a t f l i g h t phase. Flight beyond t h e atmosphere requires
approximately t h e same control force for about 40 seconds. A t o t a l impulse of about 30,000 pound-seconds i s required.
Preliminary investigation (Ref. 1) showed t h a t e i t h e r a s o l i d o r
monopropellant type system could be used f o r t h i s application. Also, a
pressurized-gas type of system appeared feasible. However, a thorough
d e f i n i t i o n of t h e l a t t e r system was required before it could be f u r t h e r
considered f o r t h i s application.
Approval has been given t o proceed with construction of a monoprop e l l a n t system because early action on t h i s system was required if it were
t o be available f o r t h e proposed f l i g h t schedule. However, study of t h e
pressurized-gas system has continued on t h e basis t h a t it might be used
as a s u b s t i t u t e o r backup f o r the monopropellant system. This paper presents t h e r e s u l t s of t h e study.
The paper i s divided i n t o three sections, The f i r s t section i s devoted t o an analysis of the thermodynamics of t h e system. The second
section describes an experimental t e s t program using available hardware
and presents t h e r e s u l t s of t h e t e s t s . The t h i r d section contains a d i s cussion of the comparison of t h e pressurized-gas and monopropellant
2
systems. Figure 1 shows the two systems schematically, and f i g u r e 2
i l l u s t r a t e s t h e i n s t a l l a t i o n of t h e systems i n t h e L i t t l e Joe I1 vehicle.
s y s m ANALYSIS
Several of t h e thermodynamic properties of nitrogen are shown i n t h e
temperature-entropy chart (fig. 3 ) - Isentropic processes A, B, and C are
superimposed on t h i s chart t o show the technique of locating thermodynamic
state points as used i n t h i s study, Process D is shown t o illustrate a
r e a l i s t i c polytropic type process i n which t h e gas absorbs some heat durTng expansion. The assumption of t h e isentropic expansion.in t h e prop e l l a n t tank leads t o a conservative estimate of propellant a v a i l a b i l i t y .
Figure 4 shows t h e variation of t h e compressibility f a c t o r of nitro-
gen i n t h e ranges of pressures and temperatures'considered.
Data f r o m f i g u r e s 3 and 4 were used i n t h e determination of an
"Availability Factor" shown i n figure 5. The "Availability Factor" is
t h e r a t i o of expendable gas t o t h e i n i t i a l quantity as calculated by t h e
i d e a l gas law.
The s p e c i f i c impulse which can be obtained f r o m t h e available gas
shown i n f i g u r e 5 i s presented i n figure 6. The choice of a pressure
r a t i o used t o c a l c u l a t e t h e s p e c i f i c impulse may be questioned because
t h e nozzle expansion process continues i n t o t h e saturated vapor region.
However, i n a purely isentropic expansion from very high pressures
(5,000 p s i ) t o very low pressures (2 p s i ) only 20 percent of t h e vapor
i s condensed (fig. 3 ) . Also, i n a blow-down type system, t h e required
pressure r a t i o (about l5O/l) i s available outside t h e saturated vapor
region during most of t h e process and the condensation a f f e c t s only a
small portion of t h e o v e r a l l process. Therefore, t h e s e l e c t i o n of a
nozzle pressure r a t i o of 150 f o r t h i s study i s e n t i r e l y acceptable. This
corresponds t o a 1 O : l nozzle area r a t i o . The under-expansion of t h e exhaust gases during t h e first portion of t h e process has a l s o been neglected. This f a c t o r tends t o o f f s e t t h e condensation e f f e c t mentioned
above insofar as t o t a l impulse is concerned. The information i n f i g u r e
6 is believed t o be accurate within a f e w percent. The l a r g e s t deviat i o n f r o m t h i s a n a l y t i c a l performance prediction w i l l be caused by "nonIsentropic" processes i n t h e storage tank. In t h i s case, the a n a l y t i c a l l y
predicted t o t a l impulse f o r a system w i l l d w a p be conservative. The
amount by which t h e prediction i s conservative is not determined.
Changes i n storage tank i n i t i a l pressures do not s i g n i f i c a n t l y
a f f e c t t h e s p e c i f i c impulse calculation f o r t h e propellant; therefore,
figure 6 can be used f o r any system having storage pressures between
2,000 and 5,000 psi, This is because t h e only variable f a c t o r a f f e c t i n g
3
performance i s t h e temperature a t t h e isentropic "state-point" associated
w i t h each amount expended and t h i s temperature did not change appreciably
with t h e various i n i t i a l storage pressures selected f o r this study.
"he data presented i n figures 5 and 6 are combined i n f i g u r e 7.
This information can be used t o estimate t h e weight of t h e propellant and
storage tank i n a system if t h e t o t a l impulse and t h e storage tank pressure r a t i o a r e known.
Choice of a storage tank pressure r a t i o depends on the flow capacity
of t h e valve used t o control thrust. For convenience, the thrust a v a i l able from several nozzles operating a t various pressures i s shown i n
figure 8. Since t h e thrust variation i n a blow-dawn type system may be
reduced by successive introdxction of more "sets" of thrusters. Figure
9 i s provided t o show t h e "thrust variation" f a c t o r as a function of
storage tank pressure r a t i o f o r one, two, and three % e t s " of nozzles.
21 the data of t h i s figure t h e assumption w a s made t h a t , with t h e i n i t i a l
functioning of each successive ''set" of thrusters, t h e thrust w i l l return
t o i t s o r i g i n a l value. This i l l u s t r a t e s t h e "regulation" e f f e c t which
can be obtained i n a '%low-down" type system.
TEST PROGRAM
I n cooperation with t h e Flight Dynamics Branch of the Spacecraft
Technology Division, a t e s t program was i n i t i a t e d with t h e following
goals :
1. Demonstrate that t h e a n a l y t i c a l estimates of system performance
a x e valid.
2.
Demonstrate t h e vehicle f l i g h t dynamics using t h e available
hardware and establish r e a l i s t i c reaction control system t o t a l
impulse and t h r u s t l e v e l requirements.
Test Apparatus
The t e s t apparatus used is shown i n figures 10 and 11. Figure 10
shows t h e t h r e e control valves considered f o r t h i s application. Figure
11 shows a closeup of the Marotta l21E valve and the associated nozzle
and plumbing used. Figure 12 shows t h e t h r u s t stand with two 1,000 i n3
3,000 p s i tanks. These tanks a r e balanced over a pivot i n order that t h e
change i n weight of propellant w i l l not a f f e c t t h e thrust measurement.
The thrust i n t h e v e r t i c a l direction i s measured by a load c e l l consisting of SR4 s t r a i n gages mounted OIL an aluminum bar.
,
4
The Honeywell c a r r i e r amplifier and CEC recorder used t o measure t h e
t h r u s t and response of t h e reaction control system i s shown i n figure 13.
The Pace analog computer used t o simulate t h e vehicle dynamics is shown
i n figure 14. The b m h recorder used t o record vehicle f l i g h t dynamics
i s shown in figure 15Test Valves
Three valves w e r e tested: Two Marotta valves, MV ZLF: and MV 553,
and one Flowdyne valve, The Marotta valves are 1-inch tube s i z e , poppettype valves, p i l o t e d by a 3-way solenoid valve, The MV 12LF has an 0,84"
equivalent diameter sharp-edge o r i f i c e characteristic. Approximately
1,000 such valves have been flown on Thor. The MV 553 i s undergoing quali f i c a t i o n tests a t p r e s e n t - f o r use on T i t a n and should be q u a l i f i e d i n
time f o r use on L i t t l e Joe 11.
The valve submitted by Flowdyne is a 1-inch tube s i z e b a l l valve
actuated by a three-way solenoid p i l o t valve. This valve has been qualif i e d by NASA-MSFC f o r use on G.S.E. and could be q u a l i f i e d f u r t h e r as a
f l i g h t item i n time f o r t h i s application. This valve i s a l s o available
i n a 2-inch tube s i z e version with similar q u a l i f i c a t i o n status.
A l l three valves have a response time of 30 t o
opening o r closing. A l l three have s u f f i c i e n t flow
consideration i n the design of t h e proposed system.
l i v e r e d up t o 1,120-pounds thrust at sea l e v e l w i t h
of 4.
40 milliseconds i n
capacities t o warrant
The valves have dea nozzle area r a t i o
Reaction System Performance
D a t a obtained from t h e t e s t apparatus hqve substantiated t h e analyti c a l estimate of t o t a l impulse within about -3 percent. One test of the
MV ELF: valve, with i n i t i a l storage tank pressure a t 3,000 p s i and f i n a l
pressure at 350 p s i , produced r e s u l t s that agreed very closely with t h e
a n a l y t i c a l prediction of t o t a l impulse f o r t h e system, The test cons i s t e d of a s i n g l e '%low-down" of about one second duration. It is very
unlikely t h a t a s i g n i f i c a n t quantity of heat w a s t r a n s f e r r e d t o t h e gas
during t h i s period and, hence, t h e close agreement v e r i f i e s t h e conservat i v e estimate obtained by assuming isentropic expansion. An estimate of
t h e additional performance which can be obtained by slow expendit& of
t h e gas was not made and this f a c t o r is not included i n s i z i n g t h e system,
Several tests w e r e run using t h e analog computer t o simulate vehicle
dynamics while tBe RCS t e s t apparatus was used t o simulate t h e reaction
control system. These t e s t s included t h e effects of t h e thrust delay
a f t e r valve command s i g n a l and t h e e f f e c t of r e l a y d e l w between t h e guidance system command and valve command signal. R e s u l t s f r o m these t e s t s
i n d i c a t e t h a t t h e '"blow-down""type system i s acceptable from t h e standpoint
5
of changing thrust l e v e l and t h a t a t o t a l impulse of about 50,000 1%-sec
w i l l be s u f f i c i e n t t o control t h e vehicle f o r t h e first 10 and last 40
seconds of booster operation. These results are preliminary in nature
and w i l l be redefined by the Flight Dynamics Branch a f t e r t h e data have
been reviewed in d e t a i l .
SYSTEM SELECTION FDR LI'ITLF JOE II
Pressurized-Gas System Considerations
Two types of pressurized-gas systems are considered:
1, Regulated
2.
- delivering constant t h r u s t throughout f l i g h t .
Unregulated o r '%low-down"
as pressure decreases.
- delivering thrust
which decreases
Both types appear f e a s i b l e f o r t h i s application and a r e shown
schematically i n f i g u r e 16. The t h r u s t delivery c h a r a c t e r i s t i c s of t h e
unregulated system can approach t h a t of t h e regulated system i f additional
t h r u s t e r s a r e made available as t h e propellant storage pressure decays
(see figure 9 ) . The choice of a system then becomes one of a trade-off
between additional t h r u s t e r s and a pressure regulator. The main consideratlon i s t h e e f f e c t of thrust variation on f l i g h t dynamics. Also, t h e
a v a i l a b i l i t y of hardware may influence t h e choice of t h e system.
For t h i s application, t h e unregulated type system could use the
Further evaluation of
t h e f l i g h t dynamics data ma;y show t h a t three s e t s are required, but t h a t
is not indicated a t present. The valve-thruster u n i t with a 1 O : l area
r a t i o nozzle would be about 7 inches long and about 3 inches i n diameter,
This u n i t would weigh about three pounds, The tankage and propellant
weight would depend upon t h e a c t u a l t h r u s t l e v e l required (khat is, t h e
final s t w a g e pressure), but w i l l not exceed 80 pounds per 1,000 Ib-sec
f o r nitrogen a d tankage (see System Analysis). The plumbing weight w i l l
not exceed 100 pounds. Therefore, the system weight f o r 50,OOO lb-sec
t o t a l impulse i s estimated t o be about 4,150 pounds,
MV l21E valve i n a dual "set" type configuration.
"he use of a regulated system requires t h r u s t control valves capable
of handling t h e t o t a l t h r u s t a t t h e minimum pressure. Thepefore, the
2-inch tube size, ball-type valve would be required. No regulator f o r
t h i s application appears t o be available. However, another method of
pressure control i s available which would use p a r a l l e l solenoid valves
operated by pressure switches. I n order t o avoid the problem of r e l i e f
devices, t h e complete system should be designed for maximum storage pressure, thereby enhancing t h e r e l i a b i l i t y of t h e system. Design of t h e
6
system f o r t h i s application could be quite simple depending upon the
thrust tolerance (pressure tolerance) which i s used. The MV l2lE valve
would probably be s u f f i c i e n t f o r t h i s application when arranged i n a
bank of f i v e valves. Hence, t h e system would consist of eight 2-inch b a l l
valves f o r t h r u s t e r s and f i v e MV 12LE: poppet valves f o r pressure regulation. This system would require f u r t h e r qualification of t h e b a l l valve.
This system weight i s estimated t o be about 3,632 pounds.
Comparison of Monopropellant and Pressurized-Gas.Systems
The p a r t i c u l a r system selected f o r comparison with t h e monopropellant
system i s the non-regulated system shown schematically i n figure 1. Comparative i n s t a l l a t i o n of the two systems on t h e booster a r e shown i n
figure 2. The weight of the mounting arrangement for the tankage i n t h e
pressurized gas system has been estimated t o be about 260 pounds ( R e f 2 ) .
An estimate of t h e r e l i a b i l i t y of t h e pressurized gas system has
been made, using t h e game r e l i a b i l i t y numbers as were used by Convair
Astronautics f o r similar parts i n the monopropellant system. The results
show t h a t the pressurized gas system i s more r e l i a b l e even though t h e
"modular" concept used i n the case of t h e monopropellant system w a s not
used on t h e pressurized gas system (see f i g u r e 17).
A b r i e f review of launch operation complexity indicates t h a t t h e
pressurized gas system i s less d i f f i c u l t t o prepare f o r launch than t h e
monopropellant system.
A brief review of the cost of t h e system showed t h a t t h e pressurized
gas system would cost about $3OO,OOO t o i n s t a l l on one vehicle. This
cost includes 16 valves a t $200 each ($3,200) and 12 titanium tanks a t
$l3,OOO each ($156,000). Some saving i n cost may be possible by using
glass wound tanks. This cost figure represents a significant advantage
over t h e monopropellant system which may cost several times t h i s amount.
The development t i m e f o r t h e experimentally-proven concept described
i n t h i s study could be e s s e n t i a l l y t h e same as t h e "lead time" f o r t h e
manufacture of parts. Delivery time on such hardware can be as short as
three months.
The pressurized-gas system w i l l weigh about twice as much as t h e
monopropellant s y s t e m . However, i f t h e 2-inch tube s i z e b a l l valve mentioned above i s f l i g h t qualified, t h e weight of t h e pressurized-gas system
could be reduced by 500 pounds, This reduction r e s u l t s from increased
u t i l i z a t i o n of t h e pressurized gas. This decision must be based upon
overall design consideration including qualification costs of t h e valve
and t h e e f f e c t of t h e extra weight on the o v e r a l l mission. Present considerations indicate t h a t an additional 2,000 pounds added t o a 243,000pound vehicle m a y not seriously compromise t h e mission.
7
FESULTS AND CONCLUSIONS
The r e s u l t s of t h i s study of a reaction control system using pressurized nitrogen are as follows:
1. Ekperimental performance of t h e pressurized nitrogen system
agrees closely with a n a l y t i c a l l y predicted performance.
2. Total impulse and thrust l e v e l requirements f o r t h i s application
are within t h e capability of this system using available f l i g h t q u a l i f i e d hardtrare.
3.
The nitrogen reaction control system w i l l f i t i n t o t h e space
available i n " L i t t l e Joe 11".
4.
A comparison of t h e pressurized-gas a d monopropellant reaction
control systems indicates an advantage f o r t h e first system i n
r e l i a b i l i t y , launch complexity, cost and development time.
5.
The pressurized-gas system w i l l weigh from 1,100 t o 2,000 pounds
more than t h e presently proposed 2,100-pound monopropellant
system.
It i s concluded t h a t the use of a pressurized-gas reaction control
system f o r this application i s f e a s i b l e using presently available f l i g h t
qualified hardware and o f f e r s a s i g n i f i c a n t advantage over the monoprop e l l a n t systems i n every consideration except weight.
REFERENCES
1. Memorandum f o r Apollo Spacecraft Project Office dated A u g u s t
6, 1962.
2.
k t t e r from General Dynamics/Convair t o W. We Petynia dated August
28, 1962.
3.
General Dynamics/Convair Attitude Control Systems Study Report dated
J u l y 2, 1962. (NASA Contract NAS 9-4923 Report No. GD/C-62-190).
-
a) 540
REQUIREMENTS -
Ib. thrwd-at each
lI
2-14" dia. X 96" 3000 psi
titanium tanks 246 Ibs. each-,
Relief
valve
nr
II
sec, to.taI.impulse
Monopropellant reaction control system
ressurized nitrogen reaction control system
schematic For Little Joe
b) 50,000 Ib.
of 8 nozzle locations
for Little Joe
lI
N, pressurant tank
N2
1" tu be
relief v aIve
I
N,
essure)
tiII valve
N, regulator
I
(I o w
presswre)
N, pressure system
4 - 9'' X 30"
tanks with biadders
I
2
units
3 Ibs. each
sets of nozzles)
Weight
= 4,150 Ib. for
relief valve
pilot pressure line
Perox ide ma nifo Id
H,O,
reaction control system with
motor valves
2 sets
(12 tanks)
3,268 Ib. for reaction control
system with 3 sets of thrusters (9 tanks)
OTE: Use of 1" ball valve will reduce the weight of the
'2 set' system to 3,632 Ib. due to the increased flow capacity.
I/
HZ 0 2 decomposition bed and nozzle
of thrusters
Weight
= 2,100 Ibs. total
(as quoted by Convair)
NOTE: 4 units required @ 520 Ibs. ea.
F I G U R E 1.- S C H E M A T I C D I A G R A M O F P R E S S U R I Z E D - G A S AND MONOPROPELLANT R E A C T I O N CONTROL SYSTEM.
M
UA
‘d gas
storage tanks
LGC . Main
- Propulsionrockets
Externa IIy
mounted
‘bolt-on’ mono
propellant
reaction
control syster
I
i
FIGURE 2.-
gas manifold
I N S T A L L A T I O N OF R E A C T I O N CONTROL SYSTEM I N
L I T T L E JOE EE.
OTE:
P = 2.67P
This figure is from
170
80
LL
0
Lui
Qc
-10
3
-I
6
CIL
Lu
CL
z
-Lu
-I
-1 00
-1 90
-280
-37c
12
13
14
15
16
17
18
TROPY, BTU/LB. MOL./"!?
19
FIGURE 3 . - NITROGEN T - S DIAGRAM.
20
6
40
30
20
I
I
.9
.85
.80
.75
P
IA
-
t state
pic process
115 0 for 10
ex pansion
nozzle
2
tI
s u r e ratio
= 1O/i
50
40
20
0
ST
L PRESSURE-PSIA
N
s
n cylindrical
. F. = 2/1
2000
1.3
1500
1000
2
I
5
I-
u
6
L
12
c
10
8
6
4
ets
2
0
4
12 14 16 18 20
sts atthe outset of
IBLE I N
SYSTEM
e
Extra sets of thrusters
for 'thrust regulation'
/\
egulated type
pressurized gas reaction
Unregulated type
pressurized gas reaction
control system
IGURE 16,- SCHEMATIC OF REGULATED AND UNREGULATED REACT
CONTROL SYSTEMS
e
MONO-PROPEUANT' SYSTEM.
Component name
PRFSSURIZED GAS SYSTEM
Failure Rate/Hour
8x
86 x
N2 tank
f i l l valves (2)
pressure regulator
N2 plumbing (36 connections)
check valve
r e l i e f valve ( 2 )
32 x 10-6
H202 bladders (4)
32 x 10-
H202 plumbing (16 connections)
80 x
180 x
N~ r e l i e f vaive
190 x 10-6
io- 6
150 x 10-6
solenoid valves (2)
140 x 10-6
decomposition chambers (2 summed) 200 x
2l.28 x
failure rate
4 + 2 R13
FIGURE 17
of one
1629 x
R = 1
R =
-
1120 x 10-
low6
lo-'
% = reliability
g
6
solenoid valves (16)
system
Rt = R1
loe6
N2 Plumbing (36 connections)
6
back pressure valve
-
96 x lom6
43 x
f i l l valve
H202 tanks (4)
R1 = 1
Failure Rate/Hour
N2 tank (12)
6
50 x io600 x io- 6
180 x io- 6
190 x 10-6
280 x 10' 6
€Lrmlng valve
Component name
mLIABILITY COMPARISON FOR LITTL;E JOE II
-
Failure Rate
-99837
REAC17ION CONTROL
sysm