PROTOTYPING AND OPTIMIZATION OF A MINIATURE MICROWAVE-FREQUENCY ION THRUSTER

Open Access
Author:
Asif, Mohammed
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 22, 2018
Committee Members:
  • Sven Bilen, Thesis Advisor/Co-Advisor
  • Michael M. Micci, Thesis Advisor/Co-Advisor
  • Amy Ruth Pritchett, Committee Member
Keywords:
  • space propulsion
  • plasma propulsion
  • propulsion
  • electric propulsion
  • rocket propulsion
  • ion engines
  • microwave thruster
  • ion thruster
  • experimental research on electric propulsion
  • computational research on electric propulsion
  • miniaturization of electric propulsion
  • ion thrusters for CubeSats
  • electric propulsion for CubeSats
Abstract:
This thesis presents progress on the development of the Miniature Microwave-Frequency Ion Thruster (MMIT), currently being developed at Penn State as a microthruster with high specific impulse that can be used on small satellites for station keeping, attitude adjustments, and modest delta-V maneuvers. The MMIT works by generating a microwave electron cyclotron resonance (ECR) discharge plasma, then accelerating ions through a series of electrostatic grids. Using argon as the propellant, the MMIT can start with as low as 2.6 W of total absorbed power from a 4.98-GHz coaxial input power source. For the current MMIT iteration, our research thrusts have been threefold: demonstrating plasma generation; sustaining and containing the plasma; and extracting the ion beam. We have largely focused on optimizing the geometry of the magnets and antenna used for ECR plasma generation; defining the geometry of the chamber for containment of the plasma; and developing grid geometries for efficient beam extraction. Progress to date toward a functional prototype has leveraged numerical simulations and experimental measurements on the proof-of-concept design, which we are currently further optimizing. A Langmuir probe is used to measure ion density and temperature in the plume as well as beam current, and a Faraday cup is used to measure the current density of the beam. The measurements obtained from these probes are used as the basis for determining a calculated thrust for the MMIT.