Direct Drive Unit with Autonomous Cathode Current Regulation

An approach for maximizing Hall thruster electrical system efficiency is to power the thruster directly from a high voltage solar array by a method commonly referred to as direct-drive. These direct drive system designs eliminate the power processing unit (PPU) and therefore have a substantial advantage in terms of overall electrical efficiency and mass savings.This Phase I/II proposal effort is comprised of the development of a Hall thruster direct drive unit (DDU). The DDU will include a method for cathode current sharing such that multiple thrusters can be operated in parallel from a single power source. In Phase I cathode current sharing approaches will be experimentally investigated. Approaches to be evaluated include passive and active methods of cathode current control. Active approaches involves independently controlled voltage sources placed in series with each cathode while passive approaches involve controlling cathode emission using heater and keeper power. In Phase II we will develop a nominal 15kW proto-flight brassboard level DDU and deliver it to NASA for additional characterization testing. The DDU unit will include the balance of PPU per specifications provided by NASA for thruster magnets, cathode heater and keeper etc. operation.