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The USAF Research Laboratory's (AFRL) Electric Propulsion Group is developing an Advanced pulsed-plasma thruster (PPT) technology demonstration for small satellites. The initial flight opportunity was on MightySat 11.2 - a satellite bus specifically designed to advance AFRL-developed technologies and serve as a risk reduction mission for systems required for TechSat 21. This experiment will demonstrate a high performance PPT, making it a viable thruster for various applications such as orbit raising and initiating and maintaining clusters of small satellites. The experiment will also be the first flight of a new micro-propulsion thruster - a miniaturized version of the PPT, known as the micro-PPT (%-PPT). The u-PPT is ideal for very precise attitude control and pointing, formation flying, and for primary propulsion on microsatellites. A novel on-board diagnostic package will be used to assess the contamination of optical and thermal control surfaces as a result of firing the PPTs. Ground-based observations will also be conducted to assess the on-orbit performance and possible communication impacts of the thruster firings., Performed in collaboration with CU Aerospace, Champaign, IL and W.E. Research, Rosamond, CA.

An overview of the current state of electric propulsion technology development efforts within the United States Air Force is presented. Air Force Mission Needs Statements which call for electric propulsion are likewise discussed. Two groups within the Air Force Research Laboratory contribute to the electric propulsion program: Propulsion Directorate and Air Force Office of Scientific Research (AFOSR). The Propulsion Directorate is conducting electric propulsion efforts in basic research. engineering development as well as an Advanced Technology Development effort that will result in a space flight experiment of a 30 kilowatt arcjet system. AFOSR funds basic research in electric propulsion throughout the country in both academia and industry., Pres: 34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 12-15 Jul, Cleveland, OH.

The focus of the PPT basic research program at AFRL has now shifted to understanding the sources of the low energy efficiency. Based on previous research modifications such as changing the electrode geometry, discharge frequency, and discharge energy may all result in moderate increases to the energy efficiency. What is required from a basic research standpoint is a diagnostic capability that can acquire information with sufficient accuracy to enable PPT designers to understand why certain influences increase performance - and then design PPTs which maximize these effects. To model a fluid description of the PPT plasma, the critical measurements are magnetic field and density. Temperature, composition and charge state also become critical as the models become more detailed. This paper describes a magnetic field probe array used at AFRL to map the magnetic fields in a laboratory model PPT. The paper focuses on determining to what extent the probe perturbs the plasma, the measurement limitations. Also discussed are options towards making this critical measurement with increased accuracy., Presented at the AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit (34th) Held in Cleveland, OH on July 12-15, 1998.