Preliminary Testing of a 17.8-GHz Microwave Electrothermal Thruster for Small Spacecraft

Open Access
Author:
Abaimov, Mikhail D
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Sven G Bilen, Thesis Advisor
Keywords:
  • microwave
  • electrothermal
  • thruster
  • CubeSat
  • small
  • spacecraft
Abstract:
CubeSats are small satellites that conform to combinations of a standard 10×10×10 cm form factor. Currently, CubeSats have limited propulsion options because their restrictive size. This thesis details the design and initial testing of a CubeSat-scale microwave electrothermal thruster. The goal of this research was to lay the groundwork for future thruster designs that could be incorporated into CubeSat propulsion modules. As part of this work, a prototype thruster head with a 17.8-GHz microwave resonant cavity was designed per dimensions determined from previous research and machined for experimentation. The candlestick antenna used in the design was optimized by varying its height above the bottom of the cavity and examining the reflected power measurements on a network analyzer. The rest of the testing setup was assembled for use with helium propellant. The power system consisted of a microwave signal generator driving a traveling-wave tube amplifier. Both cold and hot fire test results were performed. Cold flow maximum theoretical thrust was 4.77 mN, compared to a hot fire maximum theoretical thrust of 6.68 mN for the same flow rate of 2.15 mg/s. The maximum cold flow theoretical specific impulse was 225 seconds, and a maximum hot fire theoretical specific impulse of 349 seconds were achieved. The experimental setup was upgraded to allow use of anhydrous ammonia vapor as propellant. Ammonia testing was delayed, however, due to problems with the ammonia cylinder. Further work required to move the project forward is also discussed.