Hydrazine operated monopropellant generators are used for spacecraft rocket engines and propellant pressurization systems. Measured work output of monopropellant actuators compares favorably with output of squib-type actuators

Makowski, M. J.

English

NASA Technical Reports Server

Pilot 
Vent 
Valve 
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Spring
1972	 B72-10008 
NASA TECH BRIEF	
A 
Ames Research Center 
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be directed to the Technology Utilization Off i ce, NASA, Code KT, Washington, D.c. 20546. 
Propellant-Powered Actuator for Gas Generators 
Monopropellant gas generators operating with hy-
drazine have been developed for use as spacecraft 
rocket engines and for spacecraft propellant pres-
surization systems. Generally, a gas generator is con-
trolled by valves that are actuated by squib-powered 
devices. However, tests of systems which can be 
actuated by the gases formed from the catalytic 
decomposition of monopropellants have shown that 
small quantities of fuel are capable of producing 
high pressures, thus providing large actuation forces. 
Moreover, the measured work output of a monopro-
pellant actuator compares very favorably with the 
output of squib-type actuators. Hence, it was con-
sidered desirable to investigate the use of propellants 
for powering actuators. 
The diagram indicates one way in which a mono-
propellant chemical actuator can be used for opera-
tion of a monopropellant control valve that is nor-
mally open. Initially there is flow of monopropellant 
through the valve; when turn-off is desired, a pilot 
valve is pulsed, allowing a predetermined amount of
monopropellant to flow through it via a check valve; 
the monopropellant then flows into a catalyst bed 
where it is decomposed into hot gases. The pressure 
of the resulting hot gases acts against the piston or 
bellows head of the actuator to close the valve. When 
the monopropellant flow control valve is to be opened, 
the pilot vent valve is used to vent the pressure in 
the actuator; the vented gas may be directed back 
into the line or overboard. Positive opening or closing 
of a valve may be obtained by using a second 
actuator device. 
Three-way pilot valves may be used to replace the 
separate pilot valves. The advantage of using sep-
arate valves is that they need to be opened only 
momentarily for valve actuation. Actuation can thus 
be effected at reduced power requirements without 
use of latching solenoid-type valves. 
A bipropellant actuator has been designed that is 
similar to the monopropellant unit except that both 
fuel and oxidizer must be injected into the pressure 
chamber. The bipropellant actuation concept may 
also be applied to other spacecraft actuation func-
tions requiring high force levels. The use of gases 
from propellant combustion for actuation are similar 
to the use of squibs for actuating explosive valves, 
except that actuation of propellant systems can be 
repetitive. 
Note: 
Requests for further information may be di-
rected to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: TSP72-1 0008 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United 'States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000008 2020-03-17T03:20:48+00:00Z
Patent status: 
No patent action is contemplated by NASA. 
Source: M. J. Makowski of

TRW Systems Group, TRW, Inc.

under contract to

Ames Research Center

(ARC-10484)
. 
. 
S 
Category 03


Propellant-powered actuator for gas generators

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