1. Field of the Invention
This invention relates to missile control or other vehicle control technology, more particularly to a missile with a lightweight pneumatic pilot valve for controlling a main valve generally via diversion of propellant thrust.
2. Description of the Related Art
Self-propelled vehicles, including missiles and the like, are generally propelled by a main engine exerting thrust rearwardly to propel the missile through a medium, such as air. The same can be said for underwater missile technology, as well as torpedoes. The use of a single engine generally means that the rearward thrust is precisely aligned with the vehicle's center of gravity. Use of a single main engine generally does not allow for the lateral control of the missile with that engine, especially in solid fuel applications. As used herein, the term “missile” is used to indicate any propelled craft subject to the consideration and constraint as indicated by context.
One way to laterally control a missile is to use side thrusters to control the roll, pitch, and yaw, movements of the missile. These side thrusters can be powered by the same engine propellant as the main rearward-thrust engine. In this arrangement, valves are used to thrust laterally so that the missile can be maneuvered. The greater the precision of the thrust application both rearwardly and laterally, the greater the accuracy of the missile. Such accuracy is of great advantage with respect to both military and possibly civilian applications.
Missile technology can be used to deliver a weapons payload for military purposes or a civilian payload for other purposes, such as to quickly deliver rescue materials to isolated locations. Missiles can deliver such payloads very rapidly and very accurately with the proper attitude control.
Pneumatic pilot valves can be used for control of the main lateral thrust valves to provide means by which these lateral thrust valves can be operated. High temperature divert and attitude control valves for missiles and spacecraft can use one or more pilot stages to achieve fast response in high mass flow valves. In certain applications, such as solid fueled rockets and missiles, pilot valves usually have small flow passages and elements that are sensitive to erosion and contamination from condensables arising from the hot gases produced by the solid propellant gas generators. In order to resolve the demands for better missile and craft technology, the present invention provides a better solution to the demand and need for missile pilot valves such as those that control lateral thrusting.
In addition to the difficulties posed by valves, solid fuel missiles in general with diameters of less than roughly 30 inches have had to depend upon fins to guide the missile. Larger missiles and rockets have used thrust diversion valves in place of fins for guidance. However, conventional thrust valves are of the size and weight that would make them impractical to use for guidance in place of fins on such smaller vehicles having solid fuel and associated high temperature operating environments. This is especially so in the area of solid fueled tactical missiles, which may have a diameter of 10 inches or less.
In view of the foregoing, a need exists for a cost effective, lightweight, pneumatic pilot valve capable of withstanding the corrosive, erosive, and other effects of hot gases produced from solid propellant gas generators. Additionally, there is also a need for a main lateral thrust control valve that sufficiently seals the lateral thrust nozzle when off or inactive yet is able to operate quickly and reliably when needed. The present invention satisfies one of more of these needs.
The present invention provides a missile craft with a new, robust, lightweight, and relatively inexpensive pneumatic pilot valve to operate a main thrust valve in a reliable and predictable manner enabling the better targeting and operation of the associated missile craft.
The general purpose of the present invention is to provide pilot valves with improved capabilities as well as providing an advantageous poppet and valve seat design in an integrated fashion with many novel features that result in pilot valves, poppet valves, and an integrated design combining the two.
By way of example only, one embodiment of the present invention includes a lightweight composite pilot valve using refractory metal valve elements in a two stage vent design that is generally insensitive to contaminants and capable of operating under high temperature (5000° F.) conditions for short duty cycles. The pilot valve set forth herein integrates refractory valve elements with composite plastic housing structures to provide a low cost and lightweight pilot valve that controls the hot gases produced from solid propellant gas generators. A porous filter screens hot gas for particulates and condensables prior to entry into the valve. Such particulates and condensables could interfere with the operation of the pilot valve due to the close tolerances used therein. The refractory metal ball shuttles between two opposing conical refractory valve seats which are trapped between fiber-reinforced ablative phenolic housings or otherwise that may be sealed with high density exfoliated graphite gaskets. A refractory pintel is affixed to an electric solenoid plunger extending through the aperture of one of the valve seats. The pintel shuttles the ball between the seats to generally provide bistable control for the pilot valve.
In one embodiment of the valve, the pilot valve redirects thrust to control the thrust valve by allowing and preventing thrust gases to seat or unseat a main valve from its valve seat. The pilot valve has a supply valve seat and a vent valve seat to define a valve chamber. The supply valve seat defines a thrust emit opening while the vent valve seat defines a pressure vent opening. A valve gate is selectively moveable between the supply valve seat and the vent valve seat in order to selectively open or close the thrust inlet opening or the pressure vent opening, respectively. The valve chamber is in fluid communication with the thrust emit opening, the associated thrust valve, and the pressure vent opening such that operation of the valve gate in the valve chamber serves to control the flow of fluid through the valve chamber. The valve gate is subject to a valve gate control mechanism operably coupled to the valve gate. In this way, when the valve gate is seated in the vent valve seat, thrust pressure is applied to the thrust valve. The thrust then ceases when the valve gate is seated in the supply seat and any residual thrust pressure present in or on the thrust valve is vented through the pressure vent.
In one detailed embodiment, the pilot ball may divert hot gas between the control volume of a second stage valve and a two-stage ambient vent. The two-stage vent, in conjunction with the insulative properties and ablative characteristics of plastic composite materials, generally prevents pressurization and overheating of the solenoid. The housings employed generally use reinforced composites for structural valve elements. The resulting pilot valve can withstand the hostile and high temperature environment generated by the combustion of solid propellant and can take the resulting blast of thrust gases in order to provide reliable operation of the associated lateral thrust valve.
In addition to the pilot valve of the present invention, a novel valve system is disclosed herein using a flat poppet in conjunction with a novel nozzle seat design. In conjunction with the pilot valve disclosed herein, the resulting lateral thrust valve system provides reliable and predictable attitude control for missiles and other propelled craft in a cost efficient and generally-achievable design.
By way of example only, one embodiment of the invention is related to a thrust valve system for solid fuel missile guidance that is enclosed in the missile's housing, which is less than 30 inches in diameter. The missile thus would not need fins as its primary steering mechanism. In more detailed aspects of the invention, the missile could have a diameter of less than 10 inches or even less than 7 inches, to provide for air launches by aircraft or to fit in other small launching systems on space, air, ground, or sea vehicles. In one preferred embodiment, six thrust valves are used and located within the body of the missile adjacent to its main propellant exhaust port.
Other features and of the present invention will become apparent from the following description of the preferred embodiment(s), taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.
The detailed description set forth below in connection with the appended drawings is intended as a description of presently-preferred embodiments of the invention and is not intended to represent the only forms in which the present invention may be constructed and/or utilized. The description sets forth the functions and the sequence of steps for constructing and operating the invention in connection with the illustrated embodiments. However, it is to be understood that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention.
The invention is embodied in a pilot valve 100. By providing a pilot valve system that can withstand the operating conditions of generally-adjacent missile thrust from solid propellant, the pilot valve 100 provides a significantly more useful pilot valve and control system for thrust nozzles, especially thrust nozzles exerting lateral control over the missile. As used herein, the term “missile” is intended to mean all thrust-propelled craft susceptible to the present invention including spacecraft, torpedoes, missiles. In addition, the pilot valve can be used in other unrelated applications for expanding gas technology, including air bag systems for automobiles.
Beginning with
An armature plunger 116 couples the rhenium pilot valve ball 110 to the solenoid 118. The solenoid is operated by a flight computer or otherwise and causes the rhenium valve ball poker 110 to move from the vent seat 114 to the supply seat 112. By default, the solenoid is not energized and the ball poker 110 and armature plunger 116 (which may also be made of rhenium or other refractory material) is able to travel into the solenoid as by the pressure from the supply gas. The pilot valve ball 110 then seats itself against the vent seat 114, sealing the associated control chamber 102 from vents present in association with the pilot valve 100. The vents are described in greater detail below.
When the pilot valve ball 110 seats itself against the vent seat 114, the supply seat 112 is open and incoming gas applies pressure throughout the chamber system present on the other side of the supply seat 112. This includes passageways to the control chamber 102 as well as the control chamber 102 itself. The pressure from the incoming gas pushes the poppet 104 upwards against the nozzle seat 130 and the flat face 132 closes off the nozzle 106 by pressing against the nozzle seat 130. More about the operation of the poppet 104 is set forth in detail below.
The poppet 104 is maintained in an upper position closing the nozzle 106 so long as the pilot valve ball 110 is not seated on the supply seat 112 as when it is generally seated on the vent seat 114.
In order to activate the nozzle 106, the pilot valve 100 closes the supply seat 112 by activating the solenoid 118. When the solenoid 118 is activated, the armature plunger 116 is forced outwardly from the solenoid 118. This causes the pilot valve ball 110 to travel from the vent seat 114 to the supply seat 112, thus closing the supply seat 112 to the entry of incoming gas as well as enabling the opening of the vent seat 114 and the accompanying vent passageways.
The closure of the supply seat 112 cuts off the incoming gas and its associated pressure. The pressure then present in the control chamber 102 would be maintained thus keeping the nozzle 106 closed save for the ventilation system present in the pilot valve 100.
Upon moving away from the vent seat 114, the pilot valve ball 110 opens up a ventilation system enabling compressed gas and other pressure-exerting influences to escape from the control chamber 102 past the pilot valve ball 110 and through the vent seat 114.
The tolerances and clearances between the armature plunger 116 and the opening of the vent seat 114 are very close. Consequently, the ability to vent clean gas without the presence of occlusive or obstructing particles is significant to the proper operation and closing of nozzle 106. If a particle were to lodge between the pilot valve ball 110 and the vent seat 114, the vent seat might be held open, and incoming gas could be ventilated through the ventilation system (set forth below) and prevent the full possible pressure of the gas from being exerted upon the underside of the poppet 104.
The close fit between the armature plunger 116 and the radial vent slot 140 (circumscribing the armature plunger 116 just past the vent seat 114) may provide some back pressure against the poppet 104 in order to cushion the poppet's downward travel into the nozzle valve cylinder 142. Despite the narrow opening of the radial vent slots due to this close fit, the gas is generally still very hot and could injure the solenoid 118 upon its exit through the vent seat 114. In order to prevent or inhibit injury to the solenoid 118, a vent housing 144 is used to protect the solenoid 118. The vent housing 144 aids in reducing the vent pressure to ambient before the released thrust gasses engage the unsealed armature of the solenoid 118. Because the solenoid 118 of the pilot valve is not protected or sealed from the supply gas (gas), the solenoid is considered a “wet” solenoid as opposed to a “dry” solenoid.
The vent housing 144 defines the primary radial vent slots 140 between itself and the vent seat 114. The vent housing 144 defines secondary vent slots 146 between the vent housing 144 and the solenoid 118. These secondary vent slots 146 guide the hot gas away from the solenoid 118. In this way, the pilot valve 100 controls the operation of the nozzle 106 by exerting control over the poppet 104 and its disposition with respect to the nozzle seat 130. The gasses vented through the vent seat 114 and guided through the vent slots 140, 146 may be exhausted through the rear of the craft (FIG. 9).
In order to provide equal distribution of pressure from the gas or otherwise, the supply seat 112 and vent seat 114 define between them a radial control port slot 150 which communicates from the central pilot valve chamber 152 to a control flow annulus 154. The control flow annulus then communicates with the control chamber 102 via ductwork, quills, or otherwise. The use of a radial control port slot 150 enables a very thin cross section to be distributed over a wider space to allow the transmission of gas from the pilot valve chamber 152 to the control flow annulus 154 and onto the control chamber 102. This allows the passageway for pneumatic conduction from the pilot valve chamber 152 to the control chamber 102 to take up less space and to make more efficient the use of space inside the tail cone section or otherwise in a thrust propelled craft. Exfoliated graphite gaskets may be used between the refractory rhenium supply and vent seats 112, 114 and the insulating or housing elements in which the pilot valve 100 of the present invention is set.
Generally, a titanium or other motor closure 160 provides a basic structural element to which the other parts of the missile, such as the pilot valve 100, may be attached. Insulating with housing phenolic or other materials may then be used to fill empty space, provide ductwork, quills, or structure to which the other operating elements of the missile control systems may be attached. Carbon-carbon or other composite materials may be used in order to provide a housing for the pilot valve 100 and/or the poppet 104 and entire nozzle 106.
In one embodiment, gas enters the pilot valve 100 via a valve supply annulus 170 that circumscribes the top of the poppet 104 when the poppet 104 is closed. Gas enters the valve supply annulus 170, passes past the top of the poppet 104 and into a pilot valve supply port 172. The pilot valve supply port 172 transmits the gas and its accompanying pressure to a porous filter 174. The porous filter filters out condensables and particulates from the gas so that they do not interfere with the operation of the pilot valve 100. After passing through the porous filter 174, the thrust then enters the pilot valve inlet 176 and depending upon the position of the pilot valve ball 110, through the supply seat 112 and into the control chamber 102.
In operation, the solenoid 118 is energized and de-energized at a rapid rate when the nozzle 106 is to be operated. This generally provides a bistable control for the pilot valve ball 110 and allows the poppet 104 to oscillate rapidly within the confines of the nozzle valve cylinder 142. By providing short bursts of thrust, the attitudinal control of the associated missile is subject to accurate adjustment and may provide better directional control than continuous operation of the nozzle 106.
The nozzle 106 and its associated poppet/piston 104 operate in conjunction to control the lateral emission of thrust gases through the nozzle 106. The poppet 104 generally travels or oscillates coaxially with the nozzle 106 inside a rhenium sleeve-lined nozzle valve cylinder 142. The construction and operation of a rhenium sleeve-lined nozzle valve cylinder 142 is set forth in U.S. patent application Ser. No. 10/216,622 filed on Aug. 9, 2002 entitled Missile Thrust System And Valve With Refractory Piston Cylinder, and is incorporated herein by reference. The use of a rhenium-lined sleeve in the nozzle valve cylinder 142 provides for greater and more reliable and predictable operation of the poppet 104 and consequently better control of the thrust through the nozzle 106.
The flat poppet face 132 is generally circular in nature and has a diameter that is coaxial with the body of the poppet 104. The diameter of the flat poppet face 132 is generally smaller than that of the main poppet body 180 but is generally larger than the diameter of the nozzle 106 at its closest point to the poppet 104 when the poppet 104 seats against the nozzle 106. The throat 182 of the nozzle 106 has an even smaller diameter than the inlet mouth 184 which is sealed by the poppet 104. An annular region having a width indicated by reference number 186 in
As can be seen in comparing
In
As indicated above, missile diameter is a significant limitation on the guidance systems carried by a missile. Generally, solid fuel missiles in general with diameters of less than roughly 30 inches have had to depend upon fins to guide the missile. Larger missiles and rockets have used thrust diversion valves in place of fins for guidance. However, conventional thrust valves are of the size and weight that would make them impractical to use for guidance in place of fins on such smaller vehicles having solid fuel and associated high temperature operating environments. This is especially so in the area of solid fueled tactical missiles, which may have a diameter of 10 inches or less.
One embodiment of the present thrust valve system is related to a thrust valve system for solid fuel missile guidance that is enclosed in the missile's housing, which is less than 30 inches in diameter. The missile thus would not need fins as its primary steering mechanism. In more detailed aspects of the invention, the missile could have a diameter of less than 10 inches or even less than 7 inches, to provide for air launches by aircraft or to fit in other small launching systems on space, air, ground, or sea vehicles. In one preferred embodiment as shown in
As shown in the drawings, the poppet 104 is shown in an open nozzle position in
The novel reaction jet control system concept disclosed herein and shown in
A six (6) valve radial thruster assembly (
Gas pressure from the generator is supplied to the valve seat 130 at all times. Through the action of an electrically driven pilot valve 100, gas can be supplied or released from the opposite side, or control chamber side, of the poppet 104. A differential pressure area exists between either end of the poppet 104 in such a manner that pressure supplied to both ends of the poppet forces the poppet face against the flat seat 130 to close the valves 230. When gas pressure is released from the control chamber 102, the poppet 104 opens to produce radial thrust.
The piston 104 contains at least two graphite piston ring seals 240 (
The housing 246 may be assembled into the aft end of the rocket motor chamber and retained by an insulated motor closure 160. In the preferred method, the motor closure 160 is constructed from titanium to reduce weight and is held onto the rocket motor case with a circumferential thread. Radial orientation of the valves 230 relative to the rocket motor can be controlled with an adapter ring (not shown) if required. The piston housing 246 is constructed from non-eroding reinforced structural composite materials such as carbon-carbon or carbonsilicon-carbide. It can also be constructed from ablative reinforced structural composites such as carbon-phenolic or silica-phenolic. The motor closure 160 is insulated from the extreme temperature of the hot gases with carbon-phenolic or silica-phenolic reinforced insulator. Other suitable materials may also be used.
The piston bores 142 may be oriented axially or radially. In one embodiment, the piston bores 142 are oriented axially and parallel to the missile thrust axis to minimize size, weight, and envelope. For such radial bore structures, the associated nozzles may still be disposed radially. Hot gases are transferred from the motor chamber, through the titanium closure 160 and into axial passages in the exhaust nozzle assembly and provide an insulated flow path that prevents overheating of the titanium motor closure. The transfer quills contain O-rings on the outside diameter or may be retained with high temperature epoxy or silicone rubber adhesive.
The aft nozzle 222 (
In
Transfer quills 320 guide the incoming thrust 322 from the valve mouth 324 to the nozzle 106. Thrust 322 is diverted past the poppet 180 in a manner that becomes then parallel but offset from the main thrust plume 326 generated by the burning propellant 332, onto the nozzle throat 328 and ultimately out the nozzle 106. The nozzle throat 328 may be reinforced by a refractory nozzle throat insert 330 to prevent erosion at the nozzle throat and better maintain the integrity of the nozzle 106. The nozzle 250 may be made of phenolic as may be the phenolic insulator 340 which acts in conjunction with the phenolic housing 342 to define the throat 344 or the main nozzle 250. Nozzle attachment bolts 346 serve to attach the phenolic nozzle to the titanium motor closure 348. The titanium motor closure 348 may be threaded via attachment threads 354 onto the main missile body 350 with wrench holes 352 serving as means by which the titanium motor closure 348 may be engaged for threading on the main missile body 350. A gasket 358, such as an exfoliated graphite gasket, may be used to seal the interface between the phenolic nozzle 250, the phenolic insulator 340, and the titanium motor closure 348.
Valve seats 360 may be made of carbon and/or silicon carbide and serve to establish the nozzle inlet mouth 324. The valve seats 360 also define the flat annular area circumscribing the nozzle inlet mouth 324 to engage the flat poppet face 132 of the poppet 180. The operation of the valve 230 is the same as for the other embodiments disclosed herein as such operation does not involve gravity, but only the allocation of thrust pressure on either side of the poppet 180.
The pilot valve assembly 100 that controls gas flow to actuate the piston poppet 104 is comprised of rhenium valve elements captured in structural insulator, and electrically activated against supply pressure using a conventional solenoid 118. The use of phenolic insulator reduces weight and cost. The pilot valve 100 contains a two-stage vent to provide a frictionless seal that isolates the solenoid 118 from pressure and temperature of the hot gas.
The pilot valve elements are comprised of a rhenium ball 110 trapped between opposing conical rhenium valve seats 112, 114. The seats are sealed against their respective housing using exfoliated graphite gaskets. In the pilot valve disclosed herein, EGC grafoil gaskets may be used.
The valve seats 112, 114 may be retained in phenolic housing with the application of axial preload provided by solenoid retention screws or solenoid housing threads. The axial preload compresses the grafoil gaskets beneath the rhenium valve seats 112, 114, and retains the valve elements.
Supply gas pressure may be bled from the annulus 220 upstream of the piston poppet seats 130 and delivered to the inlet 176 of the pilot valve 100. Gas pressure is then fed to the pilot valve ball 110 through a porous zirconia oxide or other filter 174, which is used to trap motor exhaust condensables and particulates that could impede pilot valve function. Hot gas passes through the conical supply seat 112 past the ball 110 and flows radially outward via the port slot 150 to an axially-oriented phenolic quill 154 that transfers control pressure into the control chamber 102 of the main poppet valve 230. The pilot ball 110 acts as a thrust gas pressure gate and is normally pressurized against the opposing valve seat 114 when the solenoid 118 is in the de-energized position. A rhenium plunger 116 affixed to an electric solenoid protrudes through a small close fit hole and contacts the ball 110. The plunger 116 is attached to the solenoid armature that is displaced away from the pole face in the de-energized position.
Electrical power supplied to the solenoid coils from the flight computer or control system (not shown) provides an electromagnetic force to close the armature gap and force the ball 110 off the vent seat 114 and onto the supply seat 112. In this position, the gas supply to the piston poppet 104 is cut off, and the control chamber 102 is opened to radial vent slots 140 that release the piston poppet control chamber pressure to ambient. The pilot valve radial vent housing 144 is constructed of phenolic, which encourages ablation and thermally isolates the solenoid 118 from convection and conduction of heat into the solenoid 118. Venting the control chamber 102 causes the valve 230 to open and produces radial thrust.
Excessive pressure beneath the armature could impede pilot valve function, overheat the solenoid 118, and prevent the main valve 230 from opening. Gas vent pressure is isolated from the solenoid armature by means of the small diametrical clearance between the rhenium plunger 116 and the vent seat 114. A second series of smaller radial vent slots 146 exists between the diametrical clearance gap and the solenoid 118, to assure that all pressure exposed to the solenoid armature is vented to ambient. The two-stage vent eliminates friction associated with direct contacting seals on the solenoid armature plunger 116. Additionally, it reduces static pressure exposed to the solenoid armature and minimizes heat transfer to the solenoid 118.
In operation, the pilot valve 100 receives pulse width modulated commands to alternate movement of the pilot ball 110 from supply seat 112 to vent seat 114. The erosion resistant rhenium pilot ball 110 reciprocates between opposing rhenium seats 112, 114 to pressurize or de-pressurize the control chambers 102 of the axially or radially mounted piston poppets 104. The alternating pressurization and de-pressurization of control chambers opens and closes the poppets 104. The piston poppets reciprocate in rhenium sleeve liners 244 assembled into composite structures 246, enabling a compact, lightweight and low cost means of producing radial thrust pulses for missile directional control.
A sponge like porous filter 174 is bonded into a phenolic cartridge with ablative adhesive to provide a tortuous path for propellant gas contaminants to condense and become trapped prior to entry into a housing containing a ball poppet valve. The conical seats 112, 114 which capture a refractory ball 110, are trapped in a phenolic housing sealed with high density exfoliated graphite gaskets. The phenolic housings are retained by the solenoid housing or retention screws. The solenoid may be threaded or flange mounted. The ball stroke results from the dimensioning scheme of the valve seats and ball, which are machined to close tolerance dimensions. The solenoid stroke is larger than the ball stroke to assure the ball. seals properly on either seat after adjustments to remove assembly clearances are made. The solenoid plunger length is adjusted to remove dimensional stack up clearances when the solenoid is energized to drive the ball 110 against the gas supply seat 112.
With the solenoid de-energized, gas supply pressure forces the ball off the supply seat 112 and seals it against the vent seat 114, which diverts gas to the control chamber 102. Gas supply pressure lifts the ball 110 and pushes on the solenoid plunger 116, which translates the solenoid armature away from the pole face of the electromagnetic coil, thus increasing the armature air gap. Solenoid force is inversely related to the armature air gap. An adjustment to limit the maximum gap provides assurance of adequate force margin at worst case design conditions. Energizing the solenoid 118 to close the air gap forces the ball 110 against the supply seat 112, permitting the control chamber 102 to vent to ambient.
A refractory extension affixed to the solenoid plunger 116 may protrude through a close clearance bore in the phenolic housing that retains the valve seat downstream of the primary vent. A small annulus formed by the close fitting phenolic bore and refractory extension connect to a volume of air beneath the solenoid, which is also vented to ambient through secondary vent holes. The two stage vent design results in negligible pressure force and heat transfer to the solenoid 118.
Other embodiments of the present invention may include the use of a variety of materials that perform similar or the same operations as those set forth herein. Additionally, alternative structures, geometries, and configurations may be used to achieve the present invention.
The embodiments described herein provide one or more advantages in missile control technology, such as including the more reliable operation of divert, attitude, and/or thrust vector control valves for the diversion or use of propellant. Additionally, the flat poppet face 132 in conjunction with the flat nozzle seat 130 enable the valve system 230 to provide better and more reliable valve closure in order to ensure that stray thrust is minimized. The pilot valve system 100 also provides efficient and reliable means by which propellant gas (that by necessity creates a hostile operating environment) may be harnessed for use in the control of a lateral thrust or other thrust diversion.
Note should be taken that the pilot valve 100 and thrust valve 230 do not require sensors or springs in order to operate. This provides a significant advantage in construction and operation as such additional parts are not needed as would be less likely to survive the hot, corrosive thrust gas environment. By exploiting pressure forces, no springs are needed.
While the present invention has been described with reference to a preferred embodiment or to particular embodiments, it will be understood that various changes and additional variations may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention or the inventive concept thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to particular embodiments disclosed herein for carrying it out, but that the invention includes all embodiments falling within the scope of the appended claims.
This patent application is related to U.S. patent application Ser. No. 10/216,622 filed on Aug. 9, 2002 entitled Missile Thrust System And Valve With Refractory Piston Cylinder, and is incorporated herein by reference. This patent application is related to U.S. patent application Ser. No. 10/138,090 filed May 3, 2002, now U.S. Pat. No. 6,773,663 entitled Oxidation and Wear Resistant Rhenium Metal Matrix Composite; U.S. patent application Ser. No. 10/138,087 filed May 3, 2002 entitled Oxidation Resistant Rhenium Alloys; U.S. Provisional Patent Application Ser. No. 60/384,631 filed May 31, 2002 entitled Use of Powdered Metal Sintering/Diffusion Bonding to Enable Applying Silicon Carbide or Rhenium Alloys to Face Seal Rotors; and U.S. Provisional Patent Application Ser. No. 60/384,737 filed May 31, 2002 entitled Reduced Temperature and Pressure Powder Metallurgy Process for Consolidating Rhenium Alloys, which are all incorporated herein by reference.
The U.S. Government may have certain rights in this invention, which was developed under contract no. F08630-99-C-0027 awarded by the Air Force Research Lab/AFRL.
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Number | Date | Country | |
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20040041058 A1 | Mar 2004 | US |