The Fluid Mechanics of Pulsed Laser Propulsion

A fluid mechanical model is developed to assess the performance of a rocket that is propelled by the absorption of radiant energy from a remotely stationed, repetitively pulsed laser. The model describes the flow within a conical nozzle that is subjected to point energy depositions at the apex of the cone. A similarity solution is obtained and the specific impulse and energy efficiencies that may be achieved with such a device are determined. Fluid mechanical constraints limit the range of pulse repetition rates that may be utilized. Preliminary design considerations indicate that a specific impulse of 800 sec or greater may be achieved with both a laboratory and a full-scale device. A two pound laboratory rocket can be accelerated at 10 g's with a 15 joule laser pulsed 25,000 times per sec. A one ton rocket will require a megajoule laser operating at 350 pulses per sec to achieve an equivalent acceleration.