Laser Powered Launch Vehicle Performance Analyses

INTRODUCTIONCurrently, NASA's aim of operating low cost launch and space vehiclesrequires the research and development of advanced propulsion technologies andconcepts. One plausible advanced concept is the utilization of off-board pulsedlaser power source to propel small payload (e.g. 100kg) into earth orbit. Themerit of the laser-propelled vehicles is in its high efficiency (do not need to carryfuel) and high specific impulse. Previous SDIO research led to the invention ofthe one of the laser powered launch vehicle concept - the Laser Lightcraftconcept, currently being tested at the High Energy Laser Test System Facility,White Sands Missile Range, New Mexico. Although the spin-stabilized smallscale Lightcraft model (invented by Myrabo) has been flown successfully up to analtitude of 30 meters using a 10 kW pulsed-laser at 10 Hz, many technical issuesneed to be addressed before an optimized design of the vehicle and its operationcan be achieved.The purpose of this study is to establish the technical ground for modelingthe physics of laser powered pulse detonation phenomenon. The principle of thelaser power propulsion is that when high-powered laser is focused at a smallarea near the surface of a thruster, the intense energy causes the electricalbreakdown of the working fluid (e.g. air) and forming high speed plasma (knownas the inverse Bremsstrahlung, IB, effect). The intense heat and high pressurecreated in the plasma consequently causes the surrounding to heat up andexpand until the thrust producing shock waves are formed. This complexprocess of gas ionization, increase in radiation absorption and the forming ofplasma and shock waves will be investigated in the development of the presentnumerical model. In the first phase of this study, laser light focusing, radiativeabsorption and shock wave propagation over the entire pulsed cycle aremodeled. The model geometry and test conditions of known benchmarkexperiments such as those in Myrabo's experiment will be employed in thenumerical model validation simulations. The calculated performance data (e.g.coupling coefficients) will be compared to the test data. Plans for the numerical