Micropropulsion using a Nd:YAG microchip laser

Small, lightweight, low power solid state and semiconductor lasers are enabling the development of a new class of thruster systems for micro- and nanosatellites. These devices generate thrust by laser ablation of a solid propellant using on-board lasers and permit small satellites to perform maneuvers such as orbit maintenance, precision pointing, and formation flying. In this work we present a concept for micropropulsion called the microchip laser thruster (MLT) that is based on laser ablation by a passively Q-switched Nd:YAG microchip laser. The microchip laser enables on-board ablation by sub-ns, high peak power, high repetition rate Gaussian pulses. A propellant feed concept is proposed that consists of a cylindrically shaped solid propellant and a single drive motor. Based on measurements of single pulse laser ablation in aluminum, copper and indium targets, we find that aluminum provides the best overall thrust and specific. impulse (I-sp). Specifically, for a MLT system employing a 10 muJ/pulse, 10 kHz, 1064 run microchip laser. and Al propellant, we report the following system parameters: thrust range = 0.5 nN - 5 muN, I-sp = 4900 s, system mass = 455 g, and maximum required power = 6.5 W. Atomic force and scanning electron microscope images of craters formed by single and,multi-pulse ablation are shown to provide insight into effective propellant feed mechanism designs.