Compact vacuum arc thruster for small satellite systems

Summary form only given, as follows. Unlike present electric thrusters that are difficult to scale down in size, thrust and power, a vacuum arc thruster (VAT) is a good candidate for micro-spacecraft propulsion. In the VAT, highly ionized plasma is produced by an arc discharge from a cathode and propagates downstream generating thrust. The VAT is operated in a pulsed mode with an average power of /spl sim/1-100 watts and an overall efficiency of 16-20%. We have developed a compact inductive energy store driver that allows the VAT to be scaled down even further. The arc source of the VAT was characterized using a conventional multi-stage pulse-forming network as a driver. Several cathode elements have been evaluated. The measured arc plasma resistance is /spl sim/40 mohm, and the cathode voltage is 18 V. The arc plasma streaming velocity is in the range of 1-3e4 m/s, depending on the arc material. The ion current of the arc plasma is roughly 8% of the cathode current with an ion mean charge state of 1+ to 3+. From the tungsten arc measurements, the ion streaming velocity, arc voltage (at 50 A), cathode erosion rate and propellant utilization rate are 1.4e4 m/s, 20 V, 60e-9 kg/C and 80%, respectively. Beside the arc plasma studies, we have made a breakthrough of an inductive energy store power processing unit (PPU) that can deliver /spl sim/10-100 A pulses to the thruster at firing rates up to 600 Hz, from a package that has <100 g mass. The efficiency of this PPU is >=90% as measured. Using this PPU the overall efficiency is estimated to be /spl sim/20%. These results imply that the VAT is a promising new candidate for small spacecraft propulsion applications.