Variable Impulse Hall Thruster

"Fleets of small satellites flying in precise formation require on-board propulsion for orbit initialization, on-orbit maneuvers and to maintain relative positioning. The first scheduled on-orbit demonstration of formation flying is the AFRL/VS TechSat 21mission to demonstrate sparse aperture phased array sensing from a formation of three (170 kg) satellites.In our TechSat 21 and Phase I SBIR program we demonstrated the feasibility of operating our Hall thruster in the pulsed mode to deliver precisely controllable, repetitive and/or single impulse bits of arbitrary magnitude. The thruster was powered fromeither a PPU or a capacitor depending on the desired mode of operation.In Phase I we repetitively pulsed the thruster with the length and frequency of the discharge pulses varied depending on the capacitor size and the available charging power. Near steady state (>80%) thrust and Isp was obtained during discharge pulses asshort as 25 msec. Also, we developed plasma, electrical and flow transient models to develop a basic understanding of the initiation and evolution of the plasma discharge.In Phase II, Busek will optimize the propulsion system while powered from a PPU. Design modifications will be incorporated into the thruster, cathode and Xe feed system to minimize the required Xe flow to start the cathode and thruster. At the conclusionof Phase II, Busek will deliver to the Air Force an integrated propulsion system for variab