Center for Laser Applications

Advanced Space Propulsion

Research in advanced space propulsion systems has been a part of CLA since its inception. Research projects have included laser thermal propulsion, ion engines and arcjets. Recent experimental projects have involved diagnostic measurements of both arcjets and ion engines in the large CLA vacuum chamber. During the past year a new Russian-made Hall Thruster was operated in the Large CLA vacuum chamber under sponsorship of Lockheed Martin Astronautics. A new CLA sponsored research effort has been initiated to study pulsed microthrusters for use on small communication satellites.

A new type of ion engine under development at NASA Jet Propulsion Laboratory (JPL) was tested in our chamber in support of ERC, Inc. located in Tullahoma, Tennessee. The new engine design utilizes a third grid in an attempt to limit erosion of the accelerator grid. Extensive Langmuir probe measurements were made to establish the values of electron temperature and plasma potential in the exhaust plume. These parameters affect the way in which charge exchange ions produced in the exhaust interact with the accelerator grid of the engine. These charge exchange ions are responsible for erosion of the accelerator grid which eventually limits the useful life of the engine.

It became clear through our experimental results and computational analysis that a critical issue for the development of improved arcjet engines was the nonequilibrium nature of arcjet plasmas. Codes to simulate arcjets must include finite rate kinetic models and nonequilibrium transport properties to model adequately the behavior of these nonequilibrium plasmas.