One of the first detailed design studies of an interstellar spacecraft.1 Conducted between 1973 and 1978 by a group of a dozen scientists and engineers belonging to the British Interplanetary Society, led by Alan Bond, it demonstrated that rapid, unmanned travel to the stars is a practical possibility. Certain guidelines were adopted: the Daedalus spacecraft had to use current or near-future technology, be able to reach its destination within a human lifetime, and be flexible enough in its design that it could be sent to any of a number of target stars. These guidelines ensured that the spacecraft would be practical, that those who worked on the project might live to see it achieve its goals, and that several stars could be investigated using the same type of vehicle.
The selected target was Barnard's Star, a red dwarf lying 5.9 light-years from the Sun. Although the Alpha Centauri system is closer, evidence available at the time (now considered unreliable) suggested that Barnard's Star might be orbited by at least one planet. To reach Barnard's Star in 50 years (the flight time allotted in the study), a spacecraft would need to cruise at about 12 percent of the speed of light, or 36,000 km/s. This being far beyond the scope of a chemical rocket, the Daedalus team had to consider less conventional alternatives. The design they chose was a form of nuclear-pulse rocket, a propulsion system that had already been investigated during Project Orion. However, whereas Orion would have employed nuclear fission, the Daedalus engineers opted to power their starship by nuclear fusion – in particular, by a highly-efficient technique known as internal confinement fusion. Small pellets, containing a mixture of deuterium and helium-3, would be bombarded, one at a time, in the spacecraft's combustion chamber by electron beams and thereby caused to explode like miniature thermonuclear bombs. A powerful magnetic field would both confine the explosions and channel the resulting high-speed plasma out of the rear of the spacecraft to provide thrust. By detonating 250 pellets a second, and utilizing a two-stage approach, the desired cruising speed could be reached during an acceleration phase lasting four years.
Illustrations courtesy of Adrian Mann.
1. Bond, A., Martin, A. R., Buckland, R. A., Grant, T. J., Lawton, A. T., et al. "Project Daedalus." Journal of the British Interplanetary Society, 31 (Supplement, 1978).
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