Launching swarms of microsatellites using a 100 kW average power pulsed laser

Abstract

Transferring small payloads from Earth to low Earth orbit (LEO) and to interplanetary space using laser ablation propulsion is a new application of pulsed laser ablation propulsion, which offers parameters not available with chemical propulsion. In earlier work, we showed how to use a 1 MW average power pulsed laser to launch a 25 kg satellite from LEO to a Mars Hohmann transfer orbit in 18 minutes. Here, we discuss a lower-power application that can achieve the same result, and also cheaply and rapidly launch swarms of microsatellites into geosynchronous orbit (GEO) for communication, Earth observation, and observation of assets in GEO. The result will be a network of satellites with different functions that is robust to failures. Laser propulsion offers orbit/launch mass ratio m/M impossible with chemical rockets as well as low launch cost/kg. The main purpose in this paper is to illustrate satellite launch with repetitive pulse lasers at realistic laser average power levels. The benchmark laser has 80 ps pulsewidth, 5 kJ pulse energy, 355 nm wavelength (third Nd harmonic), and 20 Hz pulse repetition rate, using the “L’ADROIT” laser station design. To minimize laser power, we employ eight loops of steadily increasing apogee, propelled at perigee by a L’ADROIT laser in LEO, followed by a circularization “burn” at apogee using a second L’ADROIT in GEO with similar laser power. We estimate the final mf/M ratio for these maneuvers to be 43%–53%, delivering 10.8 kg into a Mars Hofmann transfer orbit and 13.2 kg to GEO. The ablated mass is contained in a spherical shell surrounding the satellite payload composed of a mixture of metal powder and polyoxymethylene. The mixture is tailored to the mission to give a matched specific impulse Isp and momentum coupling coefficient Cm. For the GEO insertion, the ablation shell splits and is re-entered after one orbit by a final “burn” from the GEO laser.