Micro Laser Plasma Thrusters for Small Satellites

The growing market for repositioning small satellites requires the development of flexible, energy-efficient, robust but microweight thrusters. Microthruster concepts are scaledowns of conventional thruster designs to very small physical scale, e.g., chemical rockets, pulsed gas thrusters and plasmajets. However, behavior of at small scales is not predicted by behavior at larger scales. We propose a new departure in microthrusters, in which thrust is generated by the plasmajet induced by an onboard high-brightness diode laser focused to a tiny spot on a plane target. No nozzle is required because of electrostatic forces involved in the plasma expansion. No new physics is required at small scales. The energy efficiency of the device is similar to that of pulsed plasma thrusters, and the electronics simpler. Specific impulse Isp is adjustable, and Isp=7000 sec has been measured. The plume produced by this interaction will be a high-velocity, electrically neutral, directed plasma jet, not a cloud of chemical compounds that can condense on the spacecraft. The most difficult part of this project is not making the thruster, but measuring impulses as small as 100 udyn-s [lE-9 n-s] . A mosquito in flight has 10 times this momentum.