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while the overall concept is very interesting, many of the more challenging technical aspects are not discussed in detail. Even if laser-triggered fusion had proven (or does some day prove) viable, the application to a space vehicle capable of reaching orbit or perhaps the Moon would present many sci- entific and engineering challenges that will remain beyond our reach for some decades to come. Beamed Power The first proposals to transmit power to an air- craft were made by the scientist and inventor Nikola Tesla (1856-1943) during the early years of the last century. While discussing his earth-resonant wireless power concept dur- ing a lecture, Tesla reportedly said, ‘with an industrial plant of great capacity, sufficient power can be derived in this manner to pro- pel any kind of aerial machine. This | have always considered the best and permanent solution to the problems of flight. No fuel of any kind will be required as the propulsion will be accomplished by light electric motors operated at great speed’. Tesla’s plans came to nothing, but a some- what simpler method of transmitting energy to an aircraft was studied in 1959 when Raytheon investigated the use of a microwave beam to power a small, high-alti- tude, unmanned helicopter. This was fol- lowed in 1964 by a_ proof-of-concept demonstration and Raytheon hoped to develop this technology into a means of pow- ering satellites or vehicles in near space, but the project went no further. During the early 1970s, Dr Arthur Kantrowitz (who founded the Avco-Everett Research Lab in Everett, Massachusetts) began to promote the rather different idea of using a laser to power a spacecraft by means of ablation. This would generate a stream of plasma behind the vehicle and create thrust, while eliminating the need for a large onboard propulsion system. The notion of using microwave and laser beams to transmit high levels of power to an aerospace vehicle and convert the energy into propulsive plasma was soon being studied by Professor Leik Myrabo of Rensselaer Polytechnic Insti- tute in Troy, New York. Myrabo then turned Kantrowitz’s idea around, envisaging a series of massive orbital solar energy collectors called Powersats, which would transmit microwaves down- wards towards the Earth in tightly focussed Although the technology was unproven, — shaped flying saucer with a diameter of 120ft Charles Osmond believed that laser-triggered — (36.58m), which was capable of carrying fusion would be possible within a short twenty-two passengers. period of time. As a consequence he applied Beneath the craft was what Osmond it to the design of a flying saucer-shaped described as a thermonuclear fusion zone, space vehicle. This utilised some elements of _ where pressurised liquid fuel would be the EHD-powered concept proposed by _ ignited by a ring of high-energy lasers and Townsend Brown over a decade earlier. energised by a homo-polar generator using a Osmond’s design was for an almost classic- large spinning disc or contra-rotating discs located above the vehicle’s underside. This would assist in shielding the upper cabin from radiation and was expected to provide the vehicle with some gyroscopic stability. To avoid structural vibration the lasers would operate at a pulsed rate of 1,000Hz. At the same time powerful magnetic fields would contain and direct the thermal energy beneath the vehicle, providing directional control. Presumably, the flow of fuel was expected to regulate thrust. Osmond hoped that the magnetic contain- ment would also help to shield the occupants of the vehicle from charged particles, although he proposed the use of heavy mate- rials above the thermonuclear zone. Once in operation electrical energy would be drawn from the fusion reaction by a number of radi- ally dispersed electrodes and this would power the lasers. Excess thermal energy would be carried to the upper surface of the flying disc by cooling tubes. Throughout the available documents there is no discussion of what fuel Osmond envis- —~e - Dr Nikola Tesla, the Serbian-American physicist, 7 . mathematician, inventor, and electrical engineer. aged for this vehicle, although he was proba- Bill Rose Collection bly considering liquid hydrogen. However, Dr Nikola Tesla, the Serbian-American physicist, mathematician, inventor, and electrical engineer. Bill Rose Collection 168 A planform drawing of British Rail’s design for a nuclear fusion-powered flying saucer. British Rail Secret Projects: Flying Saucer Aircraft