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By 1962, both sides had rocketed men into orbit. The next beachhead was the moon. Here the U.S. had an advantage. After World War II, Wernher von Braun had brought Hitler’s rocketeers to America. German ideas profoundly influenced American conceptions of manned spaceflight.

In a series of articles in Collier’s magazine in the early 1950s, von Braun inflamed popular anxiety about Soviet intentions for space by describing space stations as platforms for spying and launching nuclear weapons. The space race guaranteed that von Braun – first as director of the U.S. Army’s missile program, and then as head of NASA’s Marshall Space Flight Center – would see his giant Saturn boosters built. But because national security drove the U.S. space program, von Braun’s master plan, in which Saturn rockets would be cannibalized while in orbit and refitted as assembly stations for fleets of interplanetary ships, was discarded by NASA for the lunar-orbit rendezvous scheme chosen for the Apollo program. By landing a couple of astronauts in a lunar excursion module, Apollo offered the fastest route to the strategic high ground.

Apollo remains human history’s most brilliant project. Yet in the long term, it offered nothing that made space more accessible. If NASA had gone with von Braun’s initial plan, an array of space stations might have been orbiting Earth by the 1970s. And there were other beckoning paths that NASA, shaped by the shifting exigencies of the Cold War, chose not to follow.

For instance, the nuclear-test-ban treaty of 1963 halted the United States’ Project Orion, a top-secret effort to develop massive spaceships – on the order of thousands to mil­lions of tons – propelled by nuclear detonations. In terms of its physics, Orion wasn’t neces­sarily insane. Stanislaw Ulam, the coinventor of the hydrogen bomb, had conceived the idea the day after the first U.S. atomic-bomb test in 1945. Project Orion was led by Ted Taylor, designer of the U.S. nuclear arsenal’s largest and smallest bombs, and included Freeman Dyson, an architect of quantum electrodynamics theory.

To understand how Orion might have worked, imagine an enormous external-combustion engine. First, a nuclear bomb would be ejected through a hole in the bottom of Orion’s hull and detonated. Matter packed around the bomb would become exploding plasma. A thousand-ton aluminum pusher plate, fixed to the ship’s stern on giant shock absorbers, would shield and cushion the ship from the blast. The shock would have propelled Orion through space.

Asked today how he could have proposed using several hundred nuclear detonations to launch the Orion spacecraft into orbit 500 kilometers above the earth, Dyson is sanguine: “The worldwide fallout from Orion would have been only about 1 percent of the fallout from atmospheric bomb tests then.” Orion would have been a Faustian bargain, but the payoff was raw power: nuclear fission releases a million times as much energy as burning chemical rocket fuel. Dyson, for one, expected to be junketing around the solar system with a crew of 40 by 1970.

Fuel Deficiency
The central claim of Orion still stands today: chemical rockets are ill-suited to deep-space exploration. “Already in 1958,” Dyson has written, “we could see that von Braun’s moon ships would cost too much and do too little.” For chemical rockets, metallurgical physics is destiny. The melting temperature of the engine’s alloys limits the velocity of its ejected gas to between three and five kilometers per second. The only way to make a rocket reach even low earth orbit – which takes a velocity of eight kilometers per second – is to use booster stages. By this method, however, lifting one ton of payload into orbit requires about 16 tons of chemical rocket. To make a round trip to the moon, as Apollo did, meant five stages and almost 1,000 tons of chemical rocket for every ton of crewed module.

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