PERFORMANCE EVALUATION AND OPTIMIZATION OF HIGH POWER 14.5-GHz MINIATURE MICROWAVE ELECTROTHERMAL THRUSTER

Open Access
Author:
Adusumilli, Rohit Prasad
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 29, 2011
Committee Members:
  • Michael Matthew Micci, Thesis Advisor
  • Sven G Bilen, Thesis Advisor
Keywords:
  • Microwave Electrothermal Thruster
Abstract:
This work discusses the design and testing of a high power 14.5-GHz Miniature Microwave Electrothermal Thruster (MET) currently under development at The Pennsylvania State University. The purpose of the MET program is to develop a functional propulsion device that could be used on-board future spacecraft for functions such as attitude control. The current version of the MET was based on an existing lower power (< 20 watts) version with various modifications. Studies were performed in the areas of antenna design, RF inputs, and dielectric shape. In order to assure high coupling efficiency, the cavity was attached to a network analyzer to measure the absorbed power at various antenna lengths. Results showed that antenna protrusions between 0.3 mm to 0.7 mm resulted in the highest absorbed power and provided the highest coupling efficiency. Second, in order to accommodate the requirement for higher power, the antenna’s coaxial RF connector was changed from an SMA to an N-type connector. The N-type connector raised the maximum forward power to 100 W. Finally, due to the high temperatures that would be present at the tip of antenna, the insulating Teflon material surrounding the conductor was removed and replaced with boron nitride. Hot fire testing using helium as propellant resulted in coupling efficiencies as high as 96%. Theoretical analysis of data showed that the MET achieved a maximum thrust of 11 mN with specific impulse as high as 422 s. Recommendations to further improve the functional power range of the MET are also discussed.