September 1974
From The Space Library
Large-scale verification tests of the "rectenna" receiving system for microwave energy transmission were run at Jet Propulsion Laboratory for NASA. A microwave energy transmission system was being developed to determine the possibility of transmitting energy through space. The tests established a new record for microwave power transmission, delivering one kilowatt over a 1.6-km range. The 10-yr program had increased DC-to-DC efficiency of transmissions from 17% to 50% and efficiency of the rectenna in converting radio frequency to DC from 25% to 78%. (NASA Gen Mgt Rev Rpt, 15 Oct 74, 57-60)
Interstellar space flight appeared possible, British Interplanetary Society engineers and scientists concluded after the first 15 mos of a study to establish the feasibility of flight outside the solar system. Costs would be high, but so far none of the engineering difficulties seemed insoluble. The chief limitation that might delay such a project was the low natural abundance of helium 3 for the nuclear microbombs proposed for propulsion.
The Project Daedalus study had taken the star Barnard, six light years away, as a theoretical target. The journey was to be limited to 30-40 yrs, a working lifetime. To achieve the necessary 51 000-km-per-sec velocity, BIS scientists proposed a starship driven by a series of con-trolled nuclear explosions-each equivalent to 90 tons of TNT-occurring at the rate of 250 per sec. Microbombs, small pellets of nuclear fuel, would be compressed and heated to detonation point by electron beams. The rocket-powered boost phase would last 5 yrs, followed by a 35-yr coast. During flyby of Barnard, 10-20 probes would be released to search for inner planets and moons, sending back information to the mother ship for transmission to the earth.
NASA had studied the nuclear-pulse propulsion concept for interplanetary exploration through a General Dynamics Corp. contract in 1963, but had suspended the study because of costs and the Nuclear Test Ban Treaty. (Gatland, SF, Sept 74, 356-358; A&A 1963, 1964, 1965)
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