Hypersonic Experimental Analysis of Impulse Generation in Airbreathing Laser Thermal Propulsion

摘要

This experimental campaign focused on the analysis of the feasibility for impulse generation of a repetitively pulsed airbreathing laser lightcraft at hypersonic speeds. The future application of interest for this basic research endeavor is the laser launch of nano- and microsatellites (i.e., 1-100 kg payloads) into low Earth orbit, at low cost and on demand. These laser propulsion experiments employed a hypersonic shock tunnel, integrated with twin gigawatt pulsed Lumonics 620-TEA CO_2 lasers to produce the required test conditions. Time-dependent surface pressure distributions were recorded together with schlieren movies of the flowfleld structure resulting from the laser energy deposition, at nominal Mach numbers ranging from 6 to 10. The laser induced breakdown occurring off-surface and across the inlet's midchannel was analyzed and discussed against previous theoretical and experimental results. The data indicated laser induced pressure increases of 0.7-0.9 bar with laser pulse energies of -170 J, on an off-shroud induced breakdown condition and a freestream Mach number of six. The results of this research corroborate the feasibility of laser powered airbreathing flight with infinite specific impulse (Isp = ∞).