Sharp Blue: Project Orion

In 1958, a group of General Atomic (now General Atomics) scientists and engineers led by Ted Taylor began working on a spaceship propelled by nuclear bombs. Freeman Dyson was one of them. In another history, Dyson, Taylor and the others would go on to explore the solar system in Orion spaceships as large as ocean liners. The first expedition to Mars would have been in 1965. By 1970, astronauts would have been exploring the moons of Saturn. It was not technical problems that cost us this future, or expense, but bureaucracy and politics. In his Project Orion: The Atomic Spaceship 1957-1965, George Dyson tells the story of Orion’s physics and politics, and of his father’s dreams of a Space Age that never was.

In essence, an Orion ship is a hydrogen bomb turned inside out. A hydrogen bomb uses the pressure of the x-ray output from a fission bomb to compress and heat fuel to temperatures at which it can undergo fusion. In an Orion pulsed nuclear drive, small fission bombs are detonated a small distance behind the ship. The x-ray flux from the bomb is used to fire a disc of propellant against a “pusher plate” at the back of the ship. The impact and reflection of this propellant in turn gives the ship a burst of acceleration. One of the fission pulse units is detonated every second or so and the acceleration smoothed by shock absorbers between the pusher plate and the rest of the ship. It sounds crazy now, and it sounded even crazier in the 1950s, but the initial studies showed that it might just work. Furthermore, the performance of an Orion ship would be much, much better in terms of both thrust and specific impulse than both chemical rockets and nuclear thermal rockets.

The combination of nuclear bombs and spacecraft caused most of Orion’s political problems. General Atomic was supposed to be developing civilian uses of nuclear technology. Los Alamos resented any encroachment on their control of bomb design. The USAF loved the concept but didn’t have any need to launch thousands of tons across the solar system. After NASA was formed, it certainly would’ve liked to have launched thousand ton ships to Saturn, but its administrators really didn’t like the idea of using thousands of nuclear bombs to do so. The nuclear rocket researchers inside NASA were already heavily involved with nuclear thermal rockets, which offer only a relatively small performance improvement over chemical rockets. Surprisingly, Werner von Braun fell in love with Orion and was one of its staunchest supporters inside NASA. Not even his support was enough to get the space agency to adopt a launch vehicle powered by nukes though. In its final incarnation, Orion was reduced in scale enough to be launched by a Saturn V rocket or one of the even more massive Nova boosters (which were never built). Landing on Enceladus had drifted beyond our grasp, but even then we could’ve had Mars. Soon, that too was to be a lost.

Dyson describes the struggle against the technical and political challenges facing Orion in an engaging and evocative manner. It is a story full of hope and disappointment, of how physicists could move mountains and bureaucrats not even mole-hills. By the time the Orion project was wound down, the concept looked considerably more plausible than it had in the beginning. It would’ve worked. And NASA still thinks it could still work: EPPP, a new Orion-derived propulsion project has recently begun. Perhaps the Orioneers will live to see astronauts exploring the outer planets after all.

The most striking fact in the book is that the Orion study cost only $10 million over eight years. The movie 2001: A Space Odyssey (whose spacecraft, Discovery, was an Orion vessel in the first draft) cost $10 million over four years. In 1965, the Apollo programme spent $10 million a day.