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The year was 1957. The power of the atom had been unleashed upon the world. Technology⁠—along with just about everything else⁠—was booming. Safe, plentiful nuclear energy promised to be too cheap to meter, and radioactive waste seemed only a minor concern. It was an age of optimism and naiveté; a time of action without consequences.

Though man was the master of the Earth, only once had he managed to explore beyond the confines of the atmosphere, in the form of a beachball-sized spacecraft called Sputnik. Werner von Braun’s rocket men had drawn up plans for spacecraft that would launch humans into orbit, but even then it was clear that inefficient chemical rockets would allow only a few to enter space; the rest of mankind would be mere spectators. Fresh from their success with the atomic bomb, a small team of Manhattan Project physicists gathered to try and change all that. Working in secret within the brand new Advanced Research Projects Agency (ARPA, now called DARPA), they designed and tested an enormously ambitious nuclear spaceship concept that would have made everything the Soviets and NASA were doing seem like hobby rockets in comparison. The codename was Project Orion.

Project Orion was intended to harness nuclear energy in its rawest form: by detonating a series of nuclear bombs in rapid succession to propel enormous spaceships from the Earth into the heavens. The largest of the Orions was to be seven million tons⁠—more than 7,000 times more massive than the Space Shuttle⁠— and powerful enough to launch a small city. Provided sufficient numbers of bombs, an Orion spaceship theoretically could have reached 1/10th the speed of light, enabling interstellar travel. The motto of Project Orion was “Mars in 1965, Saturn in 1970.”

When General Atomics (GA) pitched the idea behind Project Orion to ARPA in 1958, the concept of a nuclear-propelled spaceship was nothing new. Pulp science-fiction invoked a vague “atomic drive” as early as the mid-1930s. Yet until the Manhattan Project, atomic energy was the stuff of the future. That all changed in late August 1945 when the United States opened the nuclear Pandora’s box, and the entire world stood aghast. As the dust was still settling over Hiroshima and Nagasaki, scientists and engineers almost immediately began working to harness nuclear energy for non-destructive purposes. Atoms for Peace exported civilian nuclear reactors across the world, and few companies stood to gain as much from increased use of nuclear technology as GA. The California-based company positioned itself as one of the gatekeepers of the Atomic Age, and in the process they snapped up many of the brilliant Manhattan Project minds.

Two of those men⁠—physicists Stanislaw Ulam and Freeman Dyson⁠—came to GA with an Earth-shaking idea. Intoxicated by the heady aroma of a new Age, GA hired Ulam and Dyson to study their idea for the nuclear spaceship. On its face, the very idea of nuclear explosions being harnessed for useful purposes seemed ridiculous. Many GA employees had seen the awesome specter of mushroom clouds first-hand, and the entire world had witnessed the destruction wreaked upon Japan. But Ulam and Dyson reasoned that properly shaped nuclear explosions could yield most of their energy to the propulsion of a spacecraft while leaving the ship and its occupants intact.

The fundamental design of a Project Orion spacecraft consisted of four parts: a payload of nuclear bombs, propellant, a pusher plate, and a spaceship. During launch from the Earth’s surface, the nuclear bombs would be rapidly detonated behind the Orion craft at pre-calculated distances. A disk of propellant material attached to each bomb would be vaporized to a plasma by the explosion. This plasma would expand into a cigar shape while being propelled at astounding velocities toward a heavy metal plate at the base of the ship. That pusher plate, attached to enormous hydraulic shock absorbers, would absorb the momentum of the plasma and propel the Orion spaceship forward.

Time-lapse image sequence running from bottom to top of the flight of "Hot Rod"

Project Orion was fueled by the raw intellectual prowess and unerring faith in technology held by some of the world’s most brilliant people. Its budget was tiny compared to that of the defense conglomerate General Dynamics in which it existed. Nevertheless, within a year the Orion team had completed calculations that indicated the project was feasible. In the next few months, a series of scale-model experiments called “putt-putts” were conducted with the high-powered chemical explosive C4. The first few designs were destroyed, but in November 1959 a putt-putt called Hot Rod flew to an altitude of 100 meters. The flight was surprisingly stable, and the craft nearly unscathed, lending strong evidence to the feasibility of the entire project.

A full-size Orion vehicle would have had a mass of 4,000 tons,⁠— about 40 times that of the Space Shuttle⁠— and would include a “pusher plate” about 1-meter thick at the center. This solid mass of metal served to reflect the Orion craft away from the nuclear explosions, while at the same time protecting the passengers from the neutron radiation. The enormous shock absorbers between the pusher plate and the crew module would then distribute the 10,000 G’s of each nuclear blast to something much more comfortable for Orion’s passengers. In fact, an Orion launch would probably be much more comfortable than a conventional chemical rocket because of the sheer mass of the vehicle.

Consider the launch of a hypothetical 4,000 ton Orion spaceship propelled by four-kiloton bombs. The need for protective eye wear would immediately become evident as the enormous ship would become engulfed in a fireball more intensely bright than the surface of the sun. A rapid series of blossoming explosions would push the first expanding ball of plasma skyward, though the ship would be completely invisible against the blinding glare. Within one minute, the chain of blasts would start to become visibly separate as a new flash of light would appear every few thousand feet. This pace would continue, gradually slowing until Orion reached orbit several minutes later. The final flash would then expand into the cap of a hundred-mile-long string of enormous, fiery pearls that would seem to ooze out of the ground into the atmosphere and arch gracefully into space. For observers at a safe distance, the entire launch would be completely silent. But when the pressure wave reached them a few seconds after the Orion completed its launch, the long series of thundering explosions would have sounded like the coming of the Apocalypse.

Perhaps, then, it is small surprise that the launch of the Orion was the greatest technical hurdle to its success. A single Orion launch would have left a trail of fallout across a tremendous swath of the land or sea, the radiation from its bombs would have charged the ionosphere and the Van Allen belts around the Earth, and its series of electromagnetic pulses would have destroyed all electronics within hundreds of miles of the launch site with the larger designs. It became clear to the GA physicists that solving these problems was crucial for the viability of the Project.

While they worked feverishly at overcoming the technical challenges, political forces were moving against the Project. The young NASA had the ear of the President, and parts of the agency fiercely opposed Project Orion. Werner von Braun, the German head of NASA’s manned space rocket effort was supportive of the Project and visited GA several times to confer with managers and physicists. Collaborations involving smaller Orions launched atop modified Saturn V vehicles were proposed by both parties. In early 1963, it seemed that NASA might support Orion, but the agency’s administration never came around to the idea and Project Orion was soon orphaned.

Rendering of an Orion launch by Rhys Taylor

After years of steadily declining budgets, 1965 brought the end of Project Orion. A powerful quartet of forces had aligned against it including the Defense Department, NASA, supporters of Nuclear Test Ban and Outer Space treaties, and much of the scientific establishment. While opposition from agencies and individuals may have been the immediate cause of its cancellation, the ultimate cause of its demise was probably the inability for most people to grasp how such a vehicle could ever be made safe. In addition, it was clear that every launch of an Orion would have had a massive impact on the environment.

Though Project Orion is long dead, the idea of a pulse-detonation nuclear spaceship is still alive. To some, the idea of discarding our flimsy aluminum/carbon rockets in favor of such battleship-sized behemoths is deeply romantic. More pragmatic supporters suggest a version of Orion assembled in orbit, thus avoiding most of the environmental dangers. Some have also suggested using massive, unmanned Orion craft mounted to the surface of an asteroid to push it away from collision course with Earth. One thing is certain: Orion and its nuclear-pulsed propulsion is one of the only technologies capable of reaching the speeds necessary for real-live humans to explore the outer solar system. Moreover, if mankind wishes to penetrate the frontier of interstellar space, this mothballed Atomic-Age technology may be our best chance.