Electrical/chemical thruster using the same monopropellant and method

Patent metadata

Field	Value
Publication number	US-10180118-B2
Application number	US-201615391430-A
Country	US
Kind code	B2
Filing date	Dec 27, 2016
Priority date	Dec 31, 2015
Publication date	Jan 15, 2019
Grant date	Jan 15, 2019

Abstract

A thruster operable in a chemical mode or in an electrospray mode using the same liquid monopropellant for operation in both modes is described having a multiplicity of a microthrusters made of a catalytic material having a bore therethrough, where, when operated in the chemical mode, the microthrusters are heated to decompose the monopropellant the monopropellant flows therethrough to generate relatively high thrust. An extractor is positioned downstream of the outlet ends of the microthrusters, such that when the system is operated in its electrospray mode the flowrate of the monopropellant through the microthrusters is substantially lower than in the chemical mode and the extractor is energized with an electric field so that ions and droplets are discharged from the microthrusters and accelerated so as to yield a relatively high specific impulse.

First claim

What is claimed is:

1. An electrical/chemical thruster for a spacecraft operable in a chemical mode and in an electrospray mode that utilizes a liquid monopropellant for operation in both of said chemical mode and said electrospray mode, said electrical/chemical thruster having a plurality of microthrusters, each microthruster of said plurality of microthrusters comprising a microtube having a bore therethrough and having an inlet end and an outlet end with each inlet end being in communication with a supply of said liquid monopropellant, each microtube comprising a catalytic material capable of being heated to a preheat temperature sufficient to decompose said liquid monopropellant as said liquid monopropellant flows therethrough at a first flowrate so as to generate relatively high thrust when operated in said chemical mode as compared to when operated in said electrospray mode, and wherein said electrical/chemical thruster further includes an extractor proximate each outlet end, whereby when said electrical/chemical thruster is operated in said electrospray mode with said extractor being energized to produce an electric field so that as said liquid monopropellant flows through each microtube at a second flowrate less than said first flowrate, ions and charged droplets discharged from each microtube are accelerated so as to yield a relatively high specific impulse as compared to operation of each microtube when operated in the chemical mode.

2. The electrical/chemical thruster as set forth in claim 1 wherein said liquid monopropellant comprises a mixture of one or more nonvolatile fuels and an oxidizer, wherein at least one of said one or more nonvolatile fuels and the oxidizer is an ionic liquid.

3. The electrical/chemical thruster as set forth in claim 2 wherein said liquid monopropellant has a fuel/oxidizer mixture ratio such that solid carbon forms are oxidized after chemical decomposition.

4. The electrical/chemical thruster as set forth in claim 2 wherein said liquid monopropellant comprises [Bmim][NO.sub.3] and hydroxyl ammonium nitrate (HAN).

5. The electrical/chemical thruster as set forth in claim 2 wherein said liquid monopropellant comprises [Emim][EtSO.sub.4] and hydroxyl ammonium nitrate (HAN).

6. The electrical/chemical thruster as set forth in claim 3 wherein each microtube is a capillary emitter having an inner diameter of 100 .mu.m, plus or minus 50%, and having a length of 30 mm., plus or minus 50%.

7. The electrical/chemical thruster as set forth in claim 6 wherein catalytic material is a catalytic metal.

8. The electrical/chemical thruster as set forth in claim 7 wherein each microtube, when operated in the chemical mode, is heated to said preheat temperature by an electric current.

9. The electrical/chemical thruster as set forth in claim 8 wherein said preheat temperature is 300.degree. C., plus or minus 50.degree. C.

10. The electrical/chemical thruster as set forth in claim 8 , wherein said first flowrate when each microtube is operated in the chemical mode is 20 .mu.L/second/microtube, plus or minus 10 .mu.L/sec/microtube such that each microtube will generate a thrust of 50 .mu.N, plus or minus 50%.

11. The electrical/chemical thruster as set forth in claim 8 , wherein said second flowrate when said microtube is operated in the electrospray mode is 3 pL/second/microtube, plus or minus 1 pL/second/microtube, and wherein when so operated in the electrospray mode each said microtube generates a specific impulse of 800 seconds, plus or minus 90%.

12. The electrical/chemical thruster as set forth in claim 7 further comprising additional microthrusters.

13. The electrical/chemical thruster as set forth in claim 1 wherein said electrical/chemical thruster is supplied with said liquid monopropellant from a monopropellant tank, and wherein said electrical/chemical thruster has a propellant manifold in communication with said monopropellant tank, said propellant manifold containing the supply of said liquid monopropellant so that when said electrical/chemical thruster is actuated, said liquid monopropellant is supplied to each inlet end such that liquid monopropellant flows through substantially all of said microthrusters at said first flowrate when operated in said chemical mode.

14. The electrical/chemical thruster as set forth in claim 1 wherein said first flowrate is sufficiently low to initiate decomposition of the monopropellant prior to exiting the end of the emitter, and wherein said first flow rate is sufficiently high to prevent the reaction front from propagating back into said supply of said liquid monopropellant.

15. The electrical/chemical thruster as set forth in claim 1 wherein said monopropellant flows through substantially all of said plurality of microthrusters at said second flowrate when operated in said electrospray mode.

16. A thruster for use in a spacecraft propulsion system that is operable in a chemical mode and in an electrospray mode and that utilizes a liquid monopropellant for operation in both the chemical mode the electrospray mode, said thruster having a plurality of microthrusters, each microthruster of said plurality of microthruster comprising a microtube having a bore therethrough and having an inlet end and an outlet end with said inlet end being in communication with a supply of said liquid monopropellant, each microtube comprising a catalytic metal that is capable of being heated to a preheat temperature sufficient to decompose said liquid monopropellant in each microtube as said liquid monopropellant flows therethrough at a first flowrate so as to generate relatively high thrust when operated in the chemical mode as compared to when operated in the electrospray mode, and wherein said thruster further includes an extractor downstream of the outlet end of each microtube, which, when said thruster is operated in the electrospray mode, is energized to produce an electric field such that as said liquid monopropellant flows through each microtube at a second flowrate less than said first flowrate so ions and droplets discharged from each microtube are accelerated so as to yield a relatively high specific impulse as compared to operation of each microtube in the chemical mode.

17. The thruster as set forth in claim 16 wherein said liquid monopropellant comprises a mixture of one or more nonvolatile fuels and an oxidizer, wherein at least one of said one or more nonvolatile fuels and the oxidizer is an ionic liquid.

18. The thruster as set forth in claim 17 wherein said liquid monopropellant comprises [Bmim][NO.sub.3] and hydroxyl ammonium nitrate (HAN).

19. The thruster as set forth in claim 17 wherein said liquid monopropellant comprises [Emim][EtSO.sub.4] and hydroxyl ammonium nitrate (HAN).

20. A multimode propulsion system for a spacecraft that may be operated in a chemical mode and in an electrospray mode using the same monopropellant, said multimode propulsion system having at least one thruster having a plurality of microthrusters, each microthruster of said plurality of microthrusters comprising a microtube of a suitable catalytic metal and having an inlet end and outlet end with a bore therethrough, with the bore having an internal diameter of 100 .mu.m, plus or minus 50%, said microtube having a length of 30 mm., plus or minus 50%, a monopropellant system for supplying said monopropellant from a monopropellant supply to each inlet end at a first flowrate for operation of said plurality of microthrusters in either said chemical mode or at a second flowrate for operatio

Assignees

• Univ Missouri

Inventors

• Berg Steven P
• Rovey Joshua L

Classifications

• F02K9/52

  Injectors · CPC title

• F02K9/425 Primary

  Propellants · CPC title

• F02K9/94

  Re-ignitable or restartable rocket- engine plants; Intermittently operated rocket-engine plants · CPC title

• F03H1/0012

  Means for supplying the propellant · CPC title