Thruster system, vehicle and method

Abstract

To provide an improved thruster system.SOLUTION: A thruster system includes: a tank for holding liquid propellant, a catalyst bed connected with the tank and operable to decompose the liquid propellant and generate a gas; a plenum connected with the catalyst bed for receiving the gas; a heat exchanger connected with the plenum to cool the gas to a temperature below a threshold temperature and thereby generate a cooled gas; at least one thruster connected with the heat exchanger to receive the cooled gas; and at least one control valve between the heat exchanger and the at least one thruster controlling flow of the cooled gas to the thruster. At least one control valve includes a soft material valve seal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thruster system having a control valve with a soft material seal. [Background technology]

[0002] A spacecraft may include multiple different thrusters that can be used for different types of movements. For example, a primary thruster that functions for high-speed propulsion maneuvers and one or more smaller secondary thrusters that function for precise, slower movements. Meanwhile, the ability to perform small, precise movements depends on the secondary thruster's ability to provide a small, e.g., micro-impulse bit, the smallest impulse that a thruster can reproducibly provide. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved thruster system. [Means for solving the problem]

[0004] A thruster system according to one example of the present disclosure includes a tank for holding liquid propellant, a catalyst bed connected to the tank and operable to decompose the liquid propellant to produce gas, a plenum connected to the catalyst bed to receive the gas, and a heat exchanger connected to the plenum. The heat exchanger is configured to cool the gas to a temperature below a threshold temperature, thereby producing cooled gas. At least one thruster is connected to the heat exchanger to receive the cooled gas. At least one control valve is between the heat exchanger and the at least one thruster to control the flow of cooled gas to the thruster. The at least one control valve includes a soft material seal.

[0005] In a further embodiment of any of the preceding embodiments, the soft material is AF-E-411.

[0006] In a further embodiment of any of the preceding embodiments, the heat exchanger is a phase change material heat sink.

[0007] In a further embodiment of any of the preceding embodiments, the heat exchanger is a phase change material heat sink comprising indium.

[0008] A vehicle according to one example of the present disclosure includes a tank holding liquid propellant, a catalyst bed connected to the tank and operable to decompose the liquid propellant to produce gas, a plenum connected to the catalyst bed to receive the gas, and a heat exchanger connected to the plenum. The heat exchanger is configured to cool the gas to a temperature below a threshold temperature, thereby producing cooled gas. At least one first thruster is connected to the heat exchanger to receive the cooled gas. At least one second thruster is connected to the tank to receive the liquid propellant, each of the at least one first thruster having an associated first impulse bit and each of the at least one second thruster having an associated second impulse bit, the first impulse bit being smaller than the second impulse bit. At least one control valve is located between the heat exchanger and the at least one thruster to control the flow of cooled gas to the thruster. The at least one control valve includes a valve seal made of a soft material.

[0009] In a further embodiment of any of the preceding embodiments, the associated first impulse bit is less than 100 μlbf-sec.

[0010] In a further embodiment of any of the preceding embodiments, the soft material valve seal is AF-E-411.

[0011] In a further embodiment of any of the preceding embodiments, the heat exchanger is a phase change material heat sink.

[0012] In a further embodiment of any of the preceding embodiments, the heat exchanger is a phase change material heat sink comprising indium.

[0013] A method according to one example of the present disclosure includes supplying liquid propellant from a tank to a catalyst bed connected to the tank. The catalyst bed generates gas by decomposing the liquid propellant. A plenum is filled with the gas and supplies a flow of the gas to a heat exchanger. The heat exchanger cools the gas to a temperature below a threshold temperature, thereby generating cooled gas, and supplies the cooled gas flow to at least one thruster connected to the heat exchanger. At least one control valve is disposed between the heat exchanger and the at least one thruster to control the flow of cooled gas to the thruster. The at least one control valve has a valve seal made of a soft material, and the threshold temperature corresponds to a maximum operating temperature of the soft valve seal.

[0014] In a further embodiment of any of the preceding embodiments, the soft material valve seal is AF-E-411.

[0015] In a further embodiment of any of the preceding embodiments, the heat exchanger is a phase change material heat sink.

[0016] In a further embodiment of any of the preceding embodiments, the heat exchanger is a phase change material heat sink comprising indium.

[0017] The present disclosure may include one or more of the individual features disclosed above and / or below, either alone or in any combination thereof.

[0018] The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 illustrates a thruster system. [Figure 2] FIG. 2 is a diagram illustrating an example of a control valve. [Figure 3]FIG. 10 illustrates another example of a thruster system. DETAILED DESCRIPTION OF THE INVENTION

[0020] In this disclosure, where appropriate, like reference numerals refer to like elements, and reference numerals increased by 100 or multiples thereof refer to modified elements that are understood to incorporate the same features and advantages as the corresponding elements. Terms such as "first" and "second" are used herein to distinguish between two structurally distinct components or functions. Furthermore, the terms "first" and "second" are interchangeable in that a first component or function can alternatively be referred to as a second component or function, and vice versa.

[0021] 1 illustrates a schematic diagram of an example thruster system 20. The thruster system 20 is part of a vehicle 22. It will be understood that not all systems of the vehicle 22 are shown, and the vehicle 22 may further include, for example, one or more additional thrusters and associated hardware. For example, the vehicle 22 may be a spacecraft, such as, but not limited to, a telescope, a satellite, or other spacecraft that would benefit from ultra-fine micro-impulse control.

[0022] In the illustrated example, thruster system 20 includes a tank 24 that holds a liquid propellant, such as hydrazine. Tank 24 is connected to a catalyst bed 26 operable to decompose the liquid propellant to produce a gas. Catalysts for hydrazine and other liquid propellants are well known, such as, but not limited to, supported iridium catalysts. In addition to the catalyst, catalyst bed 26 (e.g., catalyst system) may include one or more heater elements 26a, thermistors 26b, filters 26c, and valves 26d. Unless otherwise stated or implied, the term "connected" as used herein to describe a relationship between two or more components refers to the components being fluidly connected.

[0023] The thruster system 20 further includes a plenum 28 connected to the catalyst bed 26 to receive the gas. For example, the plenum 28 is a chamber generally larger in diameter than the lines connecting the tank 24, the catalyst bed 26, and the plenum. A heat exchanger 30 is connected to the plenum 28. The decomposition reaction of the liquid propellant on the catalyst bed 26 is exothermic, and therefore, the resulting gas may initially be at a temperature of 800°C or higher. The heat exchanger 30 is configured to cool the gas below a threshold temperature, thereby producing a cooled gas. For example, the heat exchanger 30 includes a phase change material that acts as a heat sink, removing heat from the gas to the surrounding environment. For example, one useful phase change material for hydrazine includes indium, which melts at approximately 157°C. The composition of the phase change material can be tailored to the outlet temperature of the gas from the catalyst bed 26 and the desired threshold temperature below which the gas should be cooled.

[0024] At least one thruster 32 is connected downstream of the heat exchanger to receive the cooled gas. In the illustrated example, there are four such thrusters, although there may alternatively be one, two, three, or more than four thrusters 32. A control valve 34 is located between the heat exchanger 30 and each thruster 32. For example, for four thrusters 32, there are four control valves 34. Each control valve 34 controls the flow of cooled gas to its respective thruster 32. The control valves 34 are connected to a controller, such as a microprocessor, which controls the opening and closing of the control valve 34 with respect to the desired amount of thrust provided by the release of cooled gas through each thruster 32.

[0025] FIG. 2 shows a representative example of a control valve 34. The control valve 34 includes a valve body 34a that defines a flow path 34b between an inlet 34c and an outlet 34d. A valve armature 34e having a valve head 34f is disposed within the flow path 34b. The valve armature 34e is movable, as indicated by arrow A, to move the valve head 34f relative to a valve seal 36. When the valve is in the closed position, the valve head 34f abuts and seals against the valve seal 36, blocking flow through the flow path 34b. When the valve is in the open position, the valve head 34f moves away from the valve seal 36, allowing flow through the flow path 34b.

[0026] The valve seal 36 is formed of a soft material. A soft material is a flexible, non-metallic material. A soft material has a low hardness (e.g., a hardness of less than Shore A 100). Soft materials include elastomers and plastic materials. Related materials include neoprene, butyl, nitrile, silicone, EPT, EPDM, EPR, FFKM, PTFE (Teflon), and AF-E-411. A soft valve seal 36 is resilient, and the force of the valve head 34f against the valve seal 36 causes the valve seal 36 to compress and deform against the valve head 34f, blocking the leak path through the passage 34b.

[0027] The use of soft materials for the valve seal 36 is made possible by cooling the gas in the heat exchanger 30. For example, the gas is cooled to a temperature corresponding to the maximum operating temperature of the soft seal, e.g., below approximately 149°C. In contrast, if the gas were not cooled, the operating temperature of the soft material would be exceeded, thus requiring a more heat-resistant material that would also provide an insufficient seal. However, by ensuring that the gas temperature remains below a threshold, a soft material can be used for the valve seal 36 to achieve a good, substantially leak-free seal. The leak-free seal ensures zero thrust when the valve 34 is closed, i.e., when the thruster 32 is off, and ultra-fine impulse bit control. For example, the valve 34 can facilitate impulse bit speeds of less than approximately 100 μlbf-sec.

[0028] In a further example, the plenum 28 also contributes to controlling the impulse bit. For example, the amount of gas, and therefore the pressure, supplied to the plenum 28 is controlled to control the magnitude of the pressure supplied to the thrusters 32. For example, a relatively high-pressure gas is supplied to the plenum 28 to generate a high-impulse bit, and a relatively low-pressure gas is supplied to the plenum 28 to generate a low-impulse bit. In this regard, the plenum 28 functions as a charging plenum, charging the plenum with gas at a desired pressure to generate a desired impulse in one or more thrusters 32. Additionally, the residence time of the gas within the plenum 28 is controlled to further adjust the gas pressure and the magnitude of the gas pressure supplied to one or more thrusters 32. By way of example, a relatively long residence time allows the gas to further cool and lose pressure, while a relatively short residence time allows the gas to maintain pressure without substantially cooling. Thus, the pressure and temperature within the plenum 28 and the outlet temperature from the heat exchanger 30 are used to control the gas to obtain a desired impulse bit.

[0029] 3 shows another example thruster system 120 that is similar to the system 20 described above, except that there is an additional primary thruster 40 also connected to the tank 24. For example, the primary thruster 40 is a high-specific-impulse thruster having a specific impulse substantially greater than each of the thrusters 32. In this regard, the primary thruster 40 is useful for high-speed propulsion maneuvers, while the smaller gas thrusters 32 are useful for fine-tuning and / or slow-speed control displacements.

[0030] Although combinations of features are shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of the present disclosure. In other words, a system designed in accordance with an embodiment of the present disclosure need not include all of the features shown in any one of the figures or all of the portions shown schematically in the figures. Furthermore, selected features of one example embodiment may be combined with selected features of other example embodiments.

[0031] The foregoing description is illustrative, not limiting. Variations and modifications to the disclosed examples will be apparent to those skilled in the art that do not necessarily depart from the disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.

Claims

1. a tank for holding a liquid propellant; a catalyst bed connected to the tank and operable to decompose the liquid propellant to produce a gas; a plenum connected to the catalyst bed to receive the gas; a heat exchanger connected to the plenum, the heat exchanger configured to cool the gas to a temperature below a threshold temperature, thereby producing a cooled gas; at least one thruster connected to the heat exchanger to receive the cooled gas; at least one control valve between the heat exchanger and the at least one thruster for controlling the flow of the cooled gas to the thruster, the at least one control valve including a soft material seal; A thruster system equipped with

2. 2. The thruster system of claim 1, wherein said soft material is AF-E-411.

3. 10. The thruster system of claim 1, wherein the heat exchanger is a phase change material heat sink.

4. 4. The thruster system of claim 3, wherein the heat exchanger is a phase change material heat sink comprising indium.

5. a tank for holding a liquid propellant; a catalyst bed connected to the tank and operable to decompose the liquid propellant to produce a gas; a plenum connected to the catalyst bed to receive the gas; a heat exchanger connected to the plenum, the heat exchanger configured to cool the gas to a temperature below a threshold temperature, thereby producing a cooled gas; at least one first thruster connected to the heat exchanger to receive the cooled gas; at least one second thruster connected to the tank to receive the liquid propellant, each of the at least one first thruster having an associated first impulse bit and each of the at least one second thruster having an associated second impulse bit, the first impulse bit being smaller than the second impulse bit; at least one control valve between the heat exchanger and the at least one thruster for controlling the flow of the cooled gas to the thruster, the at least one control valve including a soft material valve seal; A vehicle equipped with the above.

6. 6. The vehicle of claim 5, wherein said associated first impulse bit is less than 100 μlbf-sec.

7. 6. The vehicle of claim 5, wherein said soft material valve seal is AF-E-411.

8. 6. The vehicle of claim 5, wherein the heat exchanger is a phase change material heat sink.

9. 10. The vehicle of claim 8, wherein the heat exchanger is a phase change material heat sink comprising indium.

10. delivering liquid propellant from a tank to a catalyst bed connected to the tank and adapted to produce gas by decomposing the liquid propellant; Filling a plenum with said gas; providing the gas flow from the plenum to a heat exchanger connected to the plenum and configured to cool the gas to a temperature below a threshold temperature, thereby producing a cooled gas; delivering the cooled gas flow from the heat exchanger to at least one thruster connected to the heat exchanger; using at least one control valve between the heat exchanger and the at least one thruster to control the flow of the cooled gas to the thruster, the at least one control valve having a soft material valve seal, the threshold temperature corresponding to a maximum operating temperature of the soft material valve seal; A method comprising:

11. 11. The method of claim 10, wherein the soft material valve seal is AF-E-411.

12. 11. The method of claim 10, wherein the heat exchanger is a phase change material heat sink.

13. 13. The method of claim 12, wherein the heat exchanger is a phase change material heat sink comprising indium.

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