nuclear space flight and solar sailing -- 8/7/19

Today's selection -- from Disturbing the Universe by Freeman Dyson. In the years before Apollo 11, Freeman Dyson envisioned space travel propelled by nuclear fuel. Subsequent space flight theorists have envisioned solar sailing:

"Ted [Taylor] started out with three basic beliefs. First, the conventional Von Braun approach to space travel using chemical rockets would soon run into a dead-end, since manned flights going farther than the moon would become absurdly expensive. Second, the key to inter­planetary flight must be the use of nuclear fuel, which carries in each pound a million times as much energy as chemical fuel. Third, a small group of people with daring and imagination could design a nuclear spaceship which would be cheaper and enormously more capable than the best chemical rocket. So Ted set to work in the spring of 1958 to create his own VfR. Freddy [Frederic de Hoffmann] allowed him to use the facilities of General Atomic and gave him a small amount of company money to get started. I agreed to come and work on [this project which was called] Orion full time for the academic year 1958-59. We intended to build a spaceship which would be simple, rugged, and capable of carrying large payloads cheaply all over the solar system. Our slogan for the project was 'Saturn by 1970.'

"Already in 1958 we could see that [Wernher] Von Braun's moon ships, the ships that were to be used for the Apollo voyages to the moon ten years later, would cost too much and do too little. ... The Apollo ships were superbly successful in taking men for short trips to the moon, and they looked beautiful on televi­sion. But as soon as mankind became tired of this particular spectacle, the Apollo ships became as obsolete as the V-2 [rocket]. There was nothing else that they could do.

"Ted and I felt from the beginning that space travel must become cheap before it could have a liberating influence upon human affairs. ... We sketched a twelve-year flight program ending with large manned expeditions, to Mars in 1968 and to the satellites of Jupiter and Saturn in 1970.

"We worked together for a year, from summer 1958 to fall 1959, as full of enthusiasm as the VfR pioneers in their great year from 1931 to 1932. We, too, were working in a hurry, knowing that we had little time before the fall of night. We knew that the government must soon decide whether to put its main effort into chemical or into nuclear propulsion, and if we were not ready with a workable design the choice would inevitably go against us.

"We worked simultaneously at four different levels: theoretical physics calculations, experiments with high-velocity gas jets, engi­neering design of full-scale ships, and flight testing of models. At the beginning we had no specialists. Just as in the VfR, everybody did a little of everything. Later we became slightly bureaucratic and di­vided ourselves into physicists and engineers.

"The most beautiful part of the project was the flight testing. We built model ships which propelled themselves with chemical high-explosive charges instead of with nuclear bombs. ...

An artist's concept of a solar sail in Earth orbit.

"In summer 1959 the decision was made not to use nuclear propulsion for the civilian space program. ... What would have happened to us if the government had given full support to us in 1959, as it did to a similar bunch of amateurs at Los Alamos in 1943? Would we have achieved by now a cheap and rapid transportation system extending all over the solar system? Or are we lucky to have been left with our dreams intact?...

"The history of the exploration of space since 1958 has been the history of the professionals with their chemical rockets. The profes­sionals have never been willing to give a fair chance to radically new ideas. Orion is dead and I bear them no grudge for that. Orion was given a fair chance and failed. But there have been several other radical schemes that came later, schemes better than Orion, schemes that could do everything Orion could do and more, schemes that do not spread radioactive debris around the solar system. None of these newer schemes has been given the chance that was given to Orion, to prove itself in fair competition with chemical rockets. ...

"The most beautiful of the unorthodox methods of space travel is solar sailing. In principle it is possible to sail around the solar system using no engine at all. All you need is a huge gossamer-thin sail made of aluminum-coated plastic film. You can trim and tack wherever you want to go, balancing the pressure of sunlight on the sail against the force of the sun's gravity to steer a course, in the same way as the skipper of an earthly sailboat balances the pressure of the wind in his sails against the pressure of the water on his keel. The idea of solar sailing has a long history. It was first imagined by the Russian pioneer of space travel, Konstantin Tsiolkovsky. It has been reinvented many times since. The latest and most elegant design for a solar sailboat is the heliogyro invented by Richard MacNeal. MacNeal's sail is a twelve-pointed star rotating like the rotor of an autogiro airplane. In 1976 the Jet Propulsion Laboratory in California made a serious attempt in cooperation with MacNeal to design an unmanned heli­ogyro ship that could be launched and flown in time to make a rendezvous with Halley's Comet when the comet comes by the earth in March 1986. Halley's Comet comes by only once every seventy-six years, and there is no possibility of achieving a rendezvous with chemical rockets. This was a unique opportunity for the solar sail to prove itself. The space program managers rejected the Halley's Comet mission as too risky. They cannot afford to take chances. The political consequences of a failed mission might be disastrous to their whole program. Consequently, they can never afford to support a serious exploration of radically new and untried technology. ...

"When will the third romantic age in the history of space flight begin?"




Freeman Dyson


Disturbing the Universe


Basic Books


Copyright 1979 by Freeman Dyson


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