Power plants – Reaction motor – Solid and fluid propellant
Reexamination Certificate
1999-07-02
2001-06-26
Miller, Edward A. (Department: 3641)
Power plants
Reaction motor
Solid and fluid propellant
C060S207000, C060S253000, C149S001000
Reexamination Certificate
active
06250072
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
Solid propellants have numerous advantages over liquids for missile propulsion and as gas generants. Among these are greater safety in storage, handling, and transport, higher density, and simplicity of propellant packaging. Liquids, however, have traditionally offered the huge advantage of ease of throttling and can be extinguished and reignited at will, thereby offering better energy management with minimal waste of on-board propulsive resources.
One application for this invention is in the Divert and Attitude Control Systems (DACS) for kinetic-kill missile warheads. DACS provide for control of vehicles flying outside the earth's atmosphere. Missile DACS typically use solid-propellant gas generators (SPGG) to provide propulsive jets that accelerate and point the vehicle in the vacuum conditions of near-earth space. In the typical existing system, the gas generator is ignited at the start of the control period and continues to burn generally at a measured constant rate for the control duration. This is despite the fact that most of the gas is vented uselessly, because control is needed during only about 30% of the flight. As the flight time increases, the necessary control time remains essentially constant. This means that for longer flight times the wasted fuel increases to over 90%. Matching of the propellant consumption to the control requirement in a DACS could be provided by a multi-ignition, burn-on-command SPGG. This capability would eliminate the biggest single deficiency of solid-propellant systems (controllability after ignition) and would have widespread application potential. The technology involved for gas generators could be extended to most solid-propellant rocket motors as well, resulting in substantial system-level performance benefits.
Some DACS being developed, and other applications for gas generators as well, would benefit from a capability of the gas generator not only to be ignited and extinguished on command, but to have its gas temperature and flow rate controllable. For example, a single, simple gas generator may then be called on to provide turbine drive gases at temperatures around 2000° F., and subsequently provide a greater mass flow of gas at much higher temperatures (3000° F. to 5000° F.) for generating thrust in a rocket nozzle.
In this invention a liquid or gaseous oxidizer is used in relatively small quantities and in novel ways to effect the capabilities discussed above. Nitrous oxide (N
2
O) is a suitable agent for use in this invention, but other agents may be used successfully within the scope of the invention in similar ways. Pertinent characteristics of nitrous oxide are discussed below.
SUMMARY OF THE INVENTION
This invention describes reactors and techniques to decompose and otherwise use N
2
O or similar agents in both batch and continuous flow modes to advance the state of the art of throttleable gas generators for military and commercial use.
In the batch mode, a hot charge of decomposed N
2
O (a very hot mixture of oxygen and nitrogen), or other suitable agent, is discharged into a conventional SPGG as an ignition and pressurization source. The gas generator may be repeatedly extinguished and reignited by a new N
2
O discharge on command. In this manner, the need for multiple, sequenced, pyrotechnic ignitors mounted in the gas generator is avoided. The N
2
O reactor uses a single ignitor, but, most importantly, can produce charges of variable amounts as required to properly pressurize and heat the propellant in an SPGG to effect ignition.
In the continuous mode, the hot, high-pressure products of N
2
O decomposition can themselves be useful to drive prime movers, inflate bladders or balloons, etc. Although the invention provides a method of obtaining continuous N
2
O decomposition for such uses, it also includes a use of greater interest. That use is as an oxidizer in a hybrid gas generator or rocket motor. In this use N
2
O is injected into a gas generator or rocket motor chamber containing a solid fuel or fuel-rich solid propellant grain, and subsequently decomposed to initiate combustion of the grain. After ignition, by varying the flow of N
2
O into the process, the temperature of the gases produced and their rate of production can be controlled. If enough N
2
O is used, the fuel gases liberated from the solid fuel grain will be completely oxidized and the product gases will generally have temperatures over 5000° F. If the N
2
O flow is reduced, the fuel gases will not be completely oxidized and the exhaust temperature will be lower. Exhaust temperature is lower also because the pyrolysis of fuels off the grain surface absorbs heat from the N
2
O mixture. Gas temperatures below 2000° F. can probably be produced. The gases thus produced can be put to various uses, depending on their temperature, such as inflation, thrusting from a rocket nozzle, driving pneumatic systems, driving turbines, driving expander prime-movers, extinguishing fires, etc. Conversely, the gas temperature and flow rate can be tailored to the function required at any given time. That is, for example, hot gases in large quantities can be used to produce rocket thrust for a time, then cooler gases can be produced at lower flow rates to drive a turbine, from the same gas generator. The cycle can be repeated as often as needed. Also, with gas generator reignition capability, the gas generator can be turned off and on as necessary, executing even complex duty cycles, as could a bipropellant liquid gas generator.
In both batch and continuous modes of operation, a key element of the invention is a “dump valve” whose purpose is to provide rapid extinguishment of the solid propellant's combustion by rapidly depressurizing the gas generator chamber Moreover, the dump valve can be used repeatedly for multiple ignition/extinguishment cycles. This is in contrast to earlier devices, which provided only one extinguishment. The same dump valve can be configured to regulate the gas generator chamber pressure and resultant exit flow rate.
REFERENCES:
patent: 3065596 (1962-11-01), Schultz
patent: 3557556 (1971-01-01), Muzzy
patent: 3698191 (1972-10-01), Ebling
patent: 3732693 (1973-05-01), Chu et al.
patent: 3908358 (1975-09-01), Sutton et al.
patent: 5715675 (1998-02-01), Smith et al.
patent: 5727368 (1998-03-01), Wernimont et al.
patent: 6016652 (2000-01-01), Smith et al.
Burgner Gary R.
Jacobson Michael D.
Miller Edward A.
Pritchard Kenneth G.
Quoin, Inc.
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