Constant‐Fluence Area Scaling for Laser Propulsion

A series of experiments was conducted on polyoxymethylene (POM, trade name Delrin®) propellants in air at atmospheric pressure. A TEA CO2 laser with maximum output power up to 20 J was used to deliver 300 ns pulses of 10.6 μm radiation to POM targets. Ablation at a constant fluence and a range of spot areas was achieved by varying combinations of the laser energy and spot size. Relevant empirical scaling laws governing laser propulsion parameters such as the momentum coupling coefficient (Cm) and specific impulse (Isp) for spot areas within a range of about 0.05–0.25 cm2 are presented. Experimental measurements of imparted impulse, Cm, Isp, and ablated mass per pulse were made using dynamic piezoelectric force sensors and a scientific balance. Finally, Schlieren ICCD imaging of shock waves and vapor plumes was performed and analyzed.