Pulsed Laser Propulsion for Low-cost High-volume Launch to Orbit JORDIN KARE Summary Pulsed laser propulsion offers the prospect of delivering high thrust at high specific impulse (500-1000 s) from a very simple thruster, using the energy of a remote ground-based laser to heat an inert propellant. Current analyses indicate that payloads of approximately 1 kg/MW of average laser power can be launched at a rate of one payload every 15 min and a marginal cost of US$20 to US$200 per kilogram. A 20 AfW7 entry-level launch system could be built using current technology at a cost of US$500 million or less; it would be capable of placing 600 tons per year into LEO. The SDIO Laser Propulsion Program has been developing the technology for such a launch system since 1987. The Program has conducted theoretical and experimental research on a particular class of laser-driven thruster, the planar double-pulse LSD-wave thruster, which could be used for a near-term launcher. The double-pulse thruster offers several advantages including extreme simplicity, design flexibility and the ability to guide a vehicle remotely by precise control of the laser beam. Small-scale experiments have demonstrated the operation of this thruster at a specific impulse of 600 s and 10% efficiency; larger experiments now under way are expected to increase this to at least 20% efficiency. Systems-level issues, from guidance and tracking to possible unique applications, have also been considered, and will be briefly discussed. There appear to be no fundamental obstacles to creating, in the next five to 10 years, a new low-cost ‘pipeline to space’. Introduction Most space power systems now being planned or discussed have power levels measured in kilowatts. We do not yet have space hardware that needs, or can handle, megawatts of electrical power; developing such hardware will require enormous technical development and capital investment. Yet, very high powers and power densities are required for one space use: generating thrust for high acceleration and particularly for launching payloads from Earth to orbit. Currently, these power levels can only be generated (with acceptable power-to-weight ratios) by chemical combustion: a modest solid rocket booster (106 N thrust, 250 s Isp) produces over 1 GW. Pulsed laser propulsion, unique among alternative thruster and power beaming technologies, can reach power levels and power densities comparable to chemical thrusters, with higher performance and without requiring expensive flight hardware. A price is paid, of course, in complex hardware for generating and transmitting the laser Jordin Kare, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
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