Laser-powered, Multi-newton Thrust Space Engine with Variable Specific Impulse

摘要

Recently we became interested in applying previous work with liquid fueled laser powered minithrusters for spacecraft orientation to the conceptual design of a multi-newton thruster based on the same principles. Solidfuel configurations (such as the fuel tapes used in the Photonic Associates microthruster) are not amenable to the range of mass delivery rates (mg/s to g/s) necessary for such an engine. We will discuss problems for this design which have been solved, including identifying a practical method of delivering liquid fuel to the laser focus, avoiding splashing of liquid fuels under pulsed laser illumination, and avoiding optics clouding due to ablation backstreaming on optical surfaces from the laser-fuel interaction region. We have already shown that I_(sp)= 680 seconds can be achieved by a viscous liquid fuel based on glycidyl azide polymer and an IR-dye laser absorber. The final problem is mass: we will discuss a notional engine design which fits within a 10-kg "dry mass" budget. This engine, 80kg mass with fuel, is designed to fit within a 180-kg spacecraft, and use 3kW of prime power to deliver a Δv of 17.5 km/s to the spacecraft in sixteen months. Its spccific impulse will be adjustable over the range 200