Laser-sustained argon plasmas, for thermal rocket propulsion

The results of the ongoing investigation of laser-sustained argon plasmas in the forced convective flow regime are reported. Plasma absorption and thermal efficiency are the key parameters measured. Flow velocities of up to 30 m/s at one atmosphere, and up to 13.6 m/s at 2.5 atmospheres are imposed upon plasmas sustained at 2.5 kW, 5.0 kW, and 7.0 kW input laser powers, using either f/4 or f17 beam focusing geometries. Absorption ranged from 55% to 97% and thermal efficiency ranged from 11% to 46% depending upon the operating conditions. Absorptions and efficiencies this high have never before been reported and demonstrate that laser propulsion could be a practical orbital transfer concept. Spectroscopic analysis of the plasma core is used concurrently with conventional temperature and calorimetric diagnostics to determine absorption and efficiency independently.