Diode laser-driven microthrusters - A new departure in high specific impulse, long life engines

Abstract

The move toward micro- and nano-satellites in the 1 to 10-kg mass range places severe challenges on conventiona! technologies for orientation thrusters. It is obvious that these need to be efficient, extremely lightweight, long-life devices with high ISp. An additional requirement posed by the Air Force Office of Scientific Research - a minimum impulse bit (MIB) of 1 nano newton-second - has not been met by standard technologies. We developed a completely new type of thruster which has demonstrated a 1 nano newton-s MIB in a lOOjis pulse. The thruster can operate continuously, though repetitively-pulsed operation is convenient for programming force output. Single impulse dynamic range is nearly 5 orders of magnitude. This device is a Laser Plasma Thruster (LPT). It is based on the relatively recent commercial availability of diode lasers with sufficient brightness to produce a vapor or plasma jet on a surface in vacuum. It uses a simple low voltage semiconductor switch to drive the laser. A lens focuses the laser diode output on the ablation target within a very small spot, producing a spark or miniature jet that produces the thrust.