Testing and optimizaton of a miniature microwave ion thruster

Open Access
Author:
Taunay, Pierre-Yves
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 03, 2012
Committee Members:
  • Michael Matthew Micci, Thesis Advisor
  • Sven G Bilen, Thesis Advisor
Keywords:
  • microwave ion thruster
  • MMIT
  • electric propulsion
  • electron cyclotron resonance heating
  • miniature microwave ion thruster
Abstract:
Ion thrusters are able to provide low thrust and high specific impulse, making them suitable for station keeping missions and interplanetary travel. One important feature of this type of space propulsion is the emission of charged particles away from the spacecraft, requiring the use of a neutralizer emitting electrons in order to ensure thrust. This thesis presents the design and testing of a microwave miniature of ion thruster using an electron cyclotron resonance discharge. The propellant (argon or xenon) flows inside a discharge chamber at an operational mass flow rate of 0.15 sccm and is then ionized by the coupling between an oscillating electromagnetic field of frequency 5 GHz fed by a ring-type antenna and a permanent magnetic field created by two concentric magnets. Only 4 W of total absorbed power is required to obtain ionization of the plasma, and 0.4 W to sustain it. The plasma created then is accelerated through a pair of grids that have a given potential across them. Our device can operate either in an ion thruster mode, accelerating the argon or xenon atoms, or in an electron emission mode, accelerating only electrons. In the ion thruster mode the thruster is predicted to produce a thrust of 217 μN with a mass utilization efficiency of 46% and a total efficiency of 75% if the propellant used is argon. A numerical analysis of both the permanent magnetic fields and electromagnetic radiation inside the discharge chamber was also conducted. It was found that the thickness of the yoke plate to which the magnets are connected does not have any effect on the magnetic field inside the chamber and that the the antenna had to be positioned 2 mm away from the magnets in order to provide the best permanent magnetic field-electromagnetic radiation coupling. The electromagnetic radiation simulation also allowed us to validate the design of the microwave antenna.