beam transmitters (also being designed today for other purposes) and energy receivers, a space power utility concept evolves where a central power system provides power to multiple users. Although tailor-made power systems will still be required for activities beyond the power grid, just as remote systems are required on Earth, major space activities, such as low Earth orbit space commercialization and the colonization of the Moon or Mars, would benefit significantly from a central power generation and transmission system. Several options exist for linking power systems to the users. For close proximity users a tether could be used to provide the power link. For multiple users with varying separation distances, microwave or milliwave links could be used. For those beyond the viable range of micro or milliwave links, optical frequency links could be used. This paper presents the uses, benefits, and limitations of power beaming for microwave, milliwave and laser power systems. Power systems are postulated which could supply power in the kilowatt through the gigawatt range for the various scenarios. (Paper number IAF-ICOSP89-10-3.) 10-6. Pulsed Laser Propulsion for Low Cost, High Volume Launch to Orbit Jordin Kare Lawrence Livermore National Laboratory, Livermore, CA, USA. Pulsed laser propulsion offers the prospect of delivering high thrust at high specific impulse (500-2000 seconds) 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 per megawatt of average laser power can be launched at a rate of one payload every 15 minutes and a marginal cost of $20 to $200 per kg. A 20 MW entry-level launch system could be built using current technology at a cost of $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 seconds 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 ten years, a new low-cost ‘pipeline to space'. (Paper number IAF-ICOSP89-10-6.) 11. NUCLEAR SAFETY 11-1. Nuclear Space Power Systems: Ensuring Safety from Beginning to End Joseph A. Sholtis, Jr., Lt Col, USAF Directorate of Nuclear Surety, Air Force Inspection and Safety Center, Kirtland Air Force Base, NM 87117-5000, USA (Tel: 505 846-9897). Although nuclear space power systems offer distinct advantages, they also pose significant safety challenges. Stringent design and operational flight safety measures are required to ensure protection of the public and the environment under both normal and accident conditions [1]. Moreover, formal safety reviews are mandatory for ground test and flight approval [2]. Therefore, nuclear space power system safety cannot be treated as an afterthought—it is, and
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