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Title:
A MICROWAVE ELECTROTHERMAL THRUSTER ADAPTED FOR IN-SPACE ELECTROTHERMAL PROPULSION
Document Type and Number:
WIPO Patent Application WO/2017/085746
Kind Code:
A4
Abstract:
The present invention relates to a Microwave Electrothermal Thruster(MET) adapted for in-space electrothermal propulsion comprising a tunable frequency Microwave Electrothermal Thruster propulsion module enabling primary propulsion and altitude control of a satellite/spacecraft wherein RF Semiconductors is introduced for the first time as microwave generator inside cavity body to increase its efficiency and respond time and to make the thruster capable of operating in two frequencies by mechanically tuning its cavity making such thruster compact and light weight. The free-floating plasma within the resonant cavity couples the incident electrical power directly to the tangentially injected propellant gas. The plasma forms by focusing the microwave energy into the first transverse magnetic mode and operates independent of the type of propellant gas used. Also, for the first time, Shape Memory Alloy is introduced into the thruster cavity to enable faster and effective tuning of the resonant cavity diameter, when switching between two operational frequencies.

Inventors:
GANAPATHY, Rohan M (H. No. J-55, Vidyanagar Township,P.O.-Vidyanagar,Toranagallu,,Dist.-Bellary,Karnataka, Bellary 5, 583275, IN)
NOWAL, Vinod (Deputy Managing Director, JSW Steel Limited,P.O.-Vidyanagar, Toranagallu, Dist.-Bellary,Karnataka, Bellary 5, 583275, IN)
Application Number:
IN2016/050409
Publication Date:
August 03, 2017
Filing Date:
November 17, 2016
Export Citation:
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Assignee:
JSW STEEL LIMITED (JSW Centre, Bandra Kurla Complex,Bandra, Mumbai, Maharashtra, Mumbai 1, 400051, IN)
International Classes:
B64G1/40; B64G1/42; F03H1/00
Attorney, Agent or Firm:
SEN, Anjan (ANJAN SEN & ASSOCIATES, 17 Chakraberia Road, South,west Bengal, Kolkata 5, 700025, IN)
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Claims:
AMENDED CLAIMS

received by the International Bureau on 14 June 2017 (14.06.2017)

1. A Microwave Electrothermal Thruster adapted for in space electrothermal propulsion comprising, atleast one tunable primary resonant cavity with tunable resonant cavity matching to variable frequency operation and nozzle for exiting generated heated plasma in said tunable primary resonant cavity to create desired thrust; said tunable primary resonant cavity having injector port opening for injection of propellant/fuel including water based fuel ;

RF semiconductor based microwave generator for generation of microwaves for emitting into the said tunable primary resonant cavity body for interaction with said fuel to create heated gas plasma for generating said thrust when exiting through said nozzle.

2. A Microwave Electrothermal Thruster as claimed in claim 1 having a tunable variable frequency based operation comprising : mechanically tunable variable size of said tunable primary resonant cavity matching to variable frequency operation; actuator for selectively opting for a desired variable size of said tunable primary resonant cavity; said tunable primary resonant cavity of any selected desired size for selective frequency of operation having injector port opening for injection of propellant gas/ water based fuel ;

RF semiconductor based microwave generator for generation of microwaves for emitting into the said tunable primary resonant cavity for interaction with said fuel to create heated gas plasma; electromagnets surrounding atleast a part of said resonant cavity to aid rotation of plasma inside cavity and enable effective convective heat transfer between plasma and propellant gas; nozzle means operatively connected to said tunable primary resonant cavity for exiting the generated heated plasma to create desired thrust.

3. A Microwave Electrothermal Thruster as claimed in claim 2, comprising switching means for switching the electromagnets on and off around the primary resonant cavity in a clockwise manner.

4. A Microwave Electrothermal Thruster as claimed in claim 2, wherein the external electromagnets have variable field strength to favour selectively position the plasma axially centered to the nozzle avoiding the plasma to contact the primary resonant cavity surfaces.

5. A Microwave Electrothermal Thruster as claimed in claim 2, which is a dual low and high frequency mode operable thruster comprising : mechanically tunable variable size of said resonant primary cavity having a first cavity body and a second cavity body matching to said low or high frequency mode operation constituting

(i) a low frequency operation mode primary resonant cavity of larger diameter and length defined by said second cavity body and said first cavity body in combination surrounded by the external electromagnets or

(ii) high frequency operation mode primary resonant cavity of relatively smaller diameter and length having defined by said cavity body only and surrounded by the external electromagnets.

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6. A Microwave Electrothermal Thruster as claimed claim 5, wherein the first cavity body surrounded by the external electromagnets is configured to move coaxially by the actuator with respect to the second cavity body to change length of the primary resonant cavity; said second cavity having smaller diameter with respect to the first cavity body being configurable to reside within the first cavity body firmly attached to a base plate.

7. A Microwave Electrothermal Thruster as claimed in claims 6, wherein the actuator for selectively opting for the high frequency operation mode primary resonant cavity of relatively smaller diameter and length enabling coaxially moving the first cavity body surrounded by the external electromagnets to move whereby the second cavity body of relatively smaller diameter enters into said first cavity body and telescopically nest therein for effective desired reduction in length of said primary resonant cavity for desired plasma generation and exiting through said nozzle.

8. A Microwave Electrothermal Thruster as claimed in claim 6, wherein the actuator for selectively opting for the low frequency operation mode primary resonant cavity of relatively large diameter and length enabling coaxially moving the first cavity body surrounded by the external electromagnets to move whereby the first cavity body mates with fixed circular O-ring section of the second cavity body forming the prima ry resonant cavity defined by the second and the first cavity body in combination for the low frequency operation mode.

9. A Microwave Electrothermal Thruster as claimed in claim 5, wherein the first cavity body includes a separate propellant injection unit for its operation in the low frequency mode operation and the second cavity body includes its separate propellant injection for its operation in the high frequency mode operation.

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10. A Microwave Electrothermal Thruster as claimed in claim 5, wherein the first cavity body comprises viewing window to view the plasma formation in the primary resonant cavity.

11. A Microwave Electrothermal Thruster as claimed in claim 5, wherein the microwave generator comprising the RF semiconductor includes a coaxial output stub inserted with respect to the adjacent second cavity body to excite a transverse magnetic, azimuthally symmetric, bisymmetrically along the axis of the second cavity body for heating the plasma with sole impedance matching element between the microwave generator and the primary resonant cavity comprising an antenna attached to said output stub, said antenna projecting into the said second cavity body close to said base plate also supporting said RF semiconductor and adapted such that: when the thruster operates in low frequency the primary resonant cavity is activated through injection of the propellants through the injection unit of the first cavity body and activation of the microwave generator involving said RF semiconductor with the cooperative antenna to thereby generate the heated plasma; or when the thruster operates in high frequency the primary resonant cavity is activated through injection of the propellants through the injection unit of the second cavity body and activation of the microwave generator involving said RF semiconductor with the cooperative antenna to thereby generate the heated plasma.

12. A Microwave Electrothermal Thruster as claimed in claim 5, comprises means to reduce the primary resona nt cavity d ia meter when the thruster operates in high frequency mode, comprising an electrically actuated heat resistant Shape Memory Alloy (SMA) sheet attached to second end plate of the second cavity body, said second end plate includes inner guide rails/groove to guide the SMA during its actuation such that the SMA self-actuate to increase and decrease the diameter of the second cavity wall for desired for optimum tuning whereby the actuator

28 enabling the first cavity body to move coaxially governed by electrically actuated co-axial tube and actuator obstruction free insertion of the second cavity body into said first cavity body along its lower end facing said second cavity body alongwith open multiple cylindrical plates disposed in inner wall of the first cavity body separated from the each other providing larger diameter in the first cavity body allowing the second cavity body to nest within the first cavity body.

13. A Microwave Electrothermal Thruster as claimed in claim 12 wherein the cylindrical plates of said first cavity body are actuated automatically towards its center by solenoid actuators closing inter cylindrical plate gap to form a circular cavity when the first cavity body mates with the fixed circular O-ring section of the second cavity body to increase in co-axial length and diameter of the cavity and aid in the low frequency high power mode operation.

14. A Microwave Electrothermal Thruster as claimed in claim 2 wherein said propellant/fuel includes selectively inert gases, water and ammonia which upon injection into the select resonant cavity in its liquid or gaseous state get vaporized by the microwave fields and low pressure which then breaks down electrically and forms desired plasma in the microwave discharge which upon heating forms high velocity rocket exhaust.

15. A Microwave Electrothermal Thruster as claimed in claim 5 wherein said low and high frequency operation comprises of low frequency of 2.4 GHz and high frequency of 7.5 GHz.

16. A Microwave Electrothermal Thruster as claimed in claim 11, wherein the microwave antenna is of predetermined wavelength and is carried by a first end of the second cavity body, said microwave antenna coupled to a RF semiconductor for generation of microwaves for interaction with said fuel such as to heat fuel and generate said heated gas plasma preferably having said predetermined wavelength of less than 2 wavelength.

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17. A Microwave Electrothermal Thruster as claimed in claim 2, comprising a secondary resonant cavity between the nozzle and said primary resonant cavity to aid secondary plasma formation and increase exhaust temperature and speed of exiting gas.

18. A Microwave Electrothermal Thruster as claimed claim 17 wherein the nozzle is made of titanium fused with refractory oxides to withstand high temperature of exhaust gas and to minimize nozzle erosion.

19. A Microwave Electrothermal Thruster as claimed in claim 16, wherein the microwave antenna comprises of fused RF semiconductor with tunable frequency.

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