Receivers for Laser Power Beaming Summary of the Workshop at SPRAT-XII GEOFFREY A. LANDIS* SUMMARY: At the Space Photovoltaics Research and Technology [SPRAT] conference at NASA Lewis Research Center, a workshop session was held to discuss issues involved in using photovoltaic arrays ("solar cells") to convert laser power into electrical power for use as receiving elements for beamed power. Introduction Photovoltaic cells could potentially be used as power receivers for several laser sources. At NASA Langley. Conway and Walker have investigated use of space-based lasers, both direct solar-pumped [1] and diode lasers [2], for power transmission. Coomes, Bamberger, and co-workers at DOE have proposed a space-based nuclear reactor to power diode lasers which beam power to photovoltaic receivers [3]. Use of diode lasers to transmit power down optical fibers to remote GaAs receivers [4] for use on airplanes wing tips and other fiber-linked remote applications is a technology with many near-term applications. Finally, recent suggestions that adaptive optics technology could be used in conjunction with ground-based lasers to beam power to photovoltaic receivers in space [5,6] has resulted in the NASA SELENE (Space Laser Energy) project [7], SELENE has concentrated on the use of 100-kW to MW-class free- electron lasers (FELs) for transmission to geosynchronous orbit satellites, electricpropulsion orbital transfer vehicles, and (in the long term) to a photovoltaic array powering a lunar base. The consensus of the workshop was that the technology for space-based lasers would not be available until well past the year 2000, and thus the workshop focused mainly on PV receivers for ground-based laser transmitters, which were felt to have the possibility of a near-term payoff. Near-term Applications The most-discussed applications were to geosynchronous orbit satellites. The remark was made that many organizations have satellites that could possibly benefit from laser power beaming, and that the options should not be restricted only to communications satellites, or even only to U.S. satellites. A difficulty in near-term demonstrations is that only satellites in range of U.S. laser sites such as the White Sands testing range can be considcrcd.The need to make a near-term demonstration of the feasibility of the system, even if only at a low power level, was emphasized. It was suggested that operation of a single transponder on a communication satellite by laser power through a full eclipse would be a convincing demonstration. A typical satellite has 24 transponders drawing roughly 17 watts, and requires 62 watts of housekeeping power [12], Thus, operation of a single transponder would require only 9% of full * Sverdrup Technology NASA Lewis Research Center 302-121000 Brookpark Rd., Cleveland, OH 44135
RkJQdWJsaXNoZXIy MTU5NjU0Mg==