Effects of single pulse energy on impulse coupling coefficient in air-breathing laser propulsion

A lens and a paraboloid nozzle were used to focus pulsed CO2laser and generate impulse. Effects of single pulse energy on impulse coupling coefficient was studied with a high-accuracy compound pendulum and a light figure system. Extension range of pulse energy from 5 J to 70 J was obtained through adjusting working voltage of the laser and energy attenuation of silicon combinations in the experiment. In addition, schlieren photographs were taken by a nanosecond framed high speed camera at the pulse energy of 24 J. The results indicate that the impulse coupling coefficient kept constant when pulse energy ranged from 4 J to 9 J and from 32 J to 70 J respectively. From 9 J to 32 J, it changed between 6.5 and 21×10-5N·s· J-1following a linear increment. The schlieren photographs show that the flow field fell into three phases: laser-supported detonation wave, laser-supported combustion wave and blast wave. Various energy deposition ratios at different pulse energy resulted in the trend of the impulse coupling coefficient.