Power plants – Reaction motor – Electric – nuclear – or radiated energy fluid heating means
Reexamination Certificate
1999-06-04
2001-07-24
Thorpe, Timothy S. (Department: 3746)
Power plants
Reaction motor
Electric, nuclear, or radiated energy fluid heating means
Reexamination Certificate
active
06263665
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to thrusters for spacecraft, particularly compact thrusters.
2. Description of Related Art
Most micropropulsion systems in use today consist of cold gas thrusters which use propellants stored in gaseous form such as molecular nitrogen or helium. Gaseous propellant is stored at high pressures (10's of GPa) in volumetrically large, heavy titanium or graphite composite tanks. The propellant storage and thruster nozzle are typically separated by a complex valve system and perhaps a pressure regulator to reduce the gas pressure to the nozzle. Because the propellant is stored at very high pressures, the valve is typically very large in size to reduce valve leakage. These valves also typically require several Watts of power to actuate. The nozzle throat diameter for a cold gas thruster for a microsatellite mission can be on the order of 10 &mgr;m. This makes the cold gas thruster susceptible to particulate contamination plugging of the nozzle. For variable thrust missions, the operating pressure of the thruster can be regulated; however, this comes at the expense of efficiency in terms of specific impulse or thrust per unit propellant mass flow.
In other prior art is U.S. Pat. No. 5,836,150 to Garcia (1998) which relates to micropropulsion but by combustion, with attendant problems of corrosive gases at high pressures in the thruster.
Accordingly, there is need and market for a compact thruster that overcomes the above prior art shortcomings.
There has now been discovered a compact thruster that is capable of efficiently operating over a wide range of thrust levels.
SUMMARY OF THE INVENTION
Broadly the present invention provides a microthruster which includes a housing having a propellant container and a discharge section, means to heat the propellant to drive vapors toward the discharge section, a heating element to heat the vapors and one or more ports to discharge the vapors to provide thrust.
Also the invention provides a method for powering a microthruster by flowing propellant vapors in free molecular flow therein so that a plurality of vapor or gas molecules contact a heating element before discharge from the microthruster.
Definitions:
By propellant “vapor”, as used herein, is meant a vapor that is equally termed a gas and includes gas molecules.
By the “free molecule condition” or “free molecular flow”, as used herein, is meant a flow of gas molecules in a thruster that collide with each other less often than with surfaces inside of a thruster including a vapor heating element.
REFERENCES:
patent: 4322946 (1982-04-01), Murch et al.
Ketsdever Andrew D.
Muntz Eric P.
Rodriquez W
Stover Thomas C.
The United States of America as represented by the Secretary of
Thorpe Timothy S.
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