The 1950s were a wild time for nuclear technology. In the decade and a half after the dropping of the first atomic bombs on Japan in August 1945, scientists and engineers explored the different ways this technology could be used for less horrific means. Atomic bombs were even studied as an alternative to dynamite in construction, but possibly the most spectacular what-if of this era of atomic possibility is Project Orion, a proposal to use the explosions from actual atomic bombs to generate thrust to send astronauts into orbit and beyond.
Before you say that this sounds outrageous (it is), the principle behind it is pretty sound — so sound, in fact, that it is very similar to how the internal combustion engine works, which powers everything from cars to emergency generators, minus the nuclear fallout and irradiated crew.
That last bit is a stickler of a problem that Project Orion could never really overcome; but for a time, the possibility of atomic bomb-powered spaceships wasn't just a possibility, it was seriously researched by the US government, and for good reason.
The state of the world in the late 1950s
When most people see an image of an atomic mushroom cloud, it understandably elicits an almost primal fear. As the most visible demonstration of nuclear power, watching entire cities being obliterated in a flash is a legitimately terrifying thing, but for some, this wasn't the only thing they saw.
Thinkers like famed theoretical physicist Freeman Dyson also saw that the potential energy of the atomic bomb could be harnessed for truly peaceful purposes, and he wasn't alone. Stanislaw Ulam and Cornelius Everett actually conducted the first serious investigation of atomic propulsion for space flight in 1944, while they were working on the Manhattan Project.
In the 1950s, US President Eisenhower, the allied commander during World War II, introduced his "Atoms for Peace," plan which attempted to redirect atomic power towards peaceful applications that would benefit humanity, rather than threaten to destroy it.
While there were always going to be military applications for atomic energy, scientists like Dyson saw that the energy released from atomic fission wasn't any different from the energy released from chemical processes, at least in a practical sense. The amount of energy might be orders of magnitude larger than that produced in chemical combustion, but energy was energy.
At the same time that scientists were searching for peaceful applications of this technology, the Soviet Union had successfully launched Sputnik, the first artificial satellite humanity ever put into orbit, to the shock and humiliation of the United States.
Most Americans believed the Soviet Union to be a technological backwater. How the hell did they beat the United States into space? Worse still, what were their intentions?
Coming out of the darkest days of the Red Scare in the early 1950s, very few in America thought that Soviet plans for space were benign, so there was enormous pressure to catch up with the Soviet space program, especially since the American program was largely a hodgepodge of alphabet soup agencies and the United States Air Force (USAF), with little coordination.
In response, the US Government consolidated the American space effort under the umbrella of the National Aeronautics and Space Administration (NASA), which worked hand in hand with the USAF and the Advanced Research Projects Agency (ARPA), later renamed the Defence Advanced Research Projects Agency (DARPA). The very first space project that ARPA researched was a plan by General Atomics to use nuclear power to put American astronauts into orbit.
General Atomics had been founded by Frederick de Hoffman to develop commercial nuclear reactors. It was De Hoffman who persuaded Dyson, then at the Institute for Advanced Study in Princeton, New Jersey, to come to San Diego in 1958 to work on Orion, which would be led by Theodore Taylor, another veteran of Los Alamos and an expert at making small bombs.
Taylor and Dyson were instrumental in developing the plan to launch humanity not just into orbit, but to the outer reaches of the solar system itself.
The idea behind Project Orion was pretty simple, at least conceptually: Use atomic bombs to generate thrust that could lift a ship into space. This was the original challenge that General Atomics hoped to overcome. The project decided to develop a concept proposed in a 1955 paper by Stanislaw Ulam and Cornelius Everett. They suggested that bombs could be ejected backwards from the vehicle, followed by solid-propellant disks. The explosions would vaporize the disks, and the resulting plasma would impinge upon a pusher plate.
Using this nuclear pulse propulsion, Dyson and Taylor's design for the ship envisioned a large plate, a "pusher", beneath which an atomic bomb would detonate. The energy released by this explosion would drive the pusher away from the blast at a speed fast enough to achieve escape velocity.
Of course, one bomb wouldn't be enough to get a ship fully into space, so a chain of atomic explosions would be needed in quick succession to keep the ship from falling back to earth.
How many? The Orion and Super Orion-class ships needed about 800 bombs about the size of a small compact car, exploding beneath the ship at a rate of about one every second, to push it into orbit.
While this seems like overkill, the chemical rockets we're accustomed to seeing ferrying people and cargo into orbit are actually far less efficient from a practical standpoint.
According to historian George Dyson, Freeman Dyson's son who wrote a definitive history of the project, in order to accomplish what Project Orion would have been capable of using a conventional chemical rocket, would have required a rocket the size of the Empire State Building.
What's more, the incredible speed that all those atomic bombs generate would have been two to three times faster than what you could get out of conventional rockets. Once the ship reached the vacuum of space, that speed would be preserved as momentum, with any further propulsion adding to what it had already achieved once it had broken free of Earth's gravity.
While President John F. Kennedy might have been exhorting Americans to reach the Moon by the end of the 1960s, Dyson and his colleagues were aiming a little further out, hoping to have Americans reaching the moons of Saturn in roughly the same timeframe. Dyson has said that the project's motto was, "Mars by 1965, Saturn by 1970".
While initially funded by ARPA, the agency soon lost interest and General Atomics shopped it around to other agencies, finally getting some funding from the USAF, who took on the project on the condition that some military applications might be studied as well.
Specifically, the USAF was interested in developing an atomic bomb platform over the North Pole that could drop a bomb at any point on Earth while remaining out of the reach of an enemy. The military's involvement, however, meant that much of the research was then classified going forward, keeping its details secret for decades.
Once the early Minutemen rockets proved to be a much more effective delivery system for nuclear weapons, though, interest in a space-based bombing platform fell out of favor and the USAF passed the project off to NASA, who had very little interest in the project, despite some high profile backers like Wernher von Braun.
Obvious Problems with Project Orion proved insurmountable
Back in the heady days of the 1960s, when no expense was spared to ensure America didn't fall behind the Soviets again, there were certain things money just couldn't fix — namely, radiation.
Dealing with the radioactive fallout from one atomic bomb is probably about as difficult an engineering challenge as there is, so dealing with hundreds of them detonating once a second in a towering column of atomic fire dozens of miles high could be considered an impossible task. This plan raised other objections as well: What if the module, with its hundreds of bombs aboard, should explode on launch or just after? What if a bomb ruptured?
The other major concern was for the crew, who would actually have to ride all that nuclear fire into the heavens. The crew would have been exposed to as much as 700 rads of radiation each time a bomb went off beneath Orion.
For perspective, this is 10 times the minimum dose needed to trigger acute radiation syndrome in your typical human. Simply keeping the prospective astronauts alive long enough to make it to orbit would be difficult, to say the least.
The hope among the Project Orion team was that somewhere down the line a "clean" atomic bomb could be developed that didn't irradiate everything in sight, but such a bomb never materialized.
The political winds were also changing in the early 1960s. As the Cold War dragged on, a mushroom cloud was something no one on Earth ever wanted to see under pretty much any circumstances, so Project Orion fell out of favor pretty quickly.
In 1963, the signing of the Nuclear Test Ban Treaty between the US and USSR effectively cut off research into ground-based nuclear pulse propulsion, and for the final few months of development, NASA stepped in and commissioned a feasibility study for launching parts of the Orion spacecraft into orbit using Saturn V rockets and assembling the ship in space, which simply wasn't, well, feasible, so NASA finally killed the project in 1965.
Could Project Orion ever see a comeback?
In March 1961, the Gardiner Committee — a gathering of American military officials, scientists, and other experts organized in response to the Sputnik launch — issued a report which argued: "Nuclear propulsion may more than double the specific impulse attainable while still maintaining high thrust-to-weight ratios and could make possible the utilization and exploration of space on a truly vast scale.”
It's that possibility, of seeing the rings of Saturn in person or even setting foot on Pluto, that keeps Project Orion alive in the imaginations of so many scientists and engineers.
As humanity begins its crewed trek back to the Moon with NASA's Artemis program this decade — with preliminary plans for a crewed Mars mission in the 2030s — and increased interest in the industrial exploitation of space in the form of asteroid mining and space colonies, the challenges of radiation exposure will have to be addressed eventually if we ever hope to exist outside of Earth.
If we were able to come up with a solution to that problem, however, then one of the biggest challenges of Project Orion might be overcome and the dream of actual humans exploring the solar system might not be so farfetched. After all, if we can build a colony on Mars someday, we can build an Orion-style spacecraft in orbit and outside of our atmosphere, eliminating the threat to people living on Earth from radioactive fallout.
From there, the stars' the limit.