Influencing factors on propulsive performances of water droplets for laser propulsion

A transversely excited at atmospheric pressure Co₂ laser operated at 10.6 μm and 5 μs pulse width was employed to ablate atomized water droplets for laser propulsion. The momentum was derived from the force sensor data. Experimental results indicated that coupling coefficient C _m, specific impulse I_sp, and internal efficiency η were increased remarkably. The maximum value of C_m was 52.1 dyne/W. The measured value of I_sp was 102 s. Internal efficiency η of 26.1 % was achieved. Total impulse I and coupling coefficient C_m were dependent largely on the droplets' Sauter mean diameter and speed and their combined interaction. Specific impulse I_sp and internal efficiency η were dependent on the droplets' Sauter mean diameter, speed, flow rate of liquid propellant feeding system, and their combined interaction. The flow rate of the liquid feeding system dominated the influencing factors on specific impulse I_sp and internal efficiency η.