If I told that here was a plan to launch a spacecraft the size of an ocean liner, that would weigh 130 times more than the Space Shuttle, could travel with unrivalled speed across our Solar System and was powered by riding on a series pulses created by exploding thousands of miniature atomic bombs, one after another, another behind the ship, you would probably say that I’d been reading too many sci-fi books or websites.
However, in the 1950’s and 60’s just such an idea was taken very seriously. ‘Project Orion’ was a classified American project to harness the power of the atom to lift extreme payloads into Earth orbit and beyond.
After the launch of Sputnik by the Soviet Union, the shock to the US establishment was so great that almost any idea to catch up and overtake them was up for grabs.
The first calculations into ‘Nuclear Pulse Propulsion’ appeared in a 1947 memo co-written by the famous physicist Stanislav Ulam, who had worked on early nuclear tests at the Los Alamos laboratory. His idea was to detonate a nuclear device in a combustion chamber and inject water as a propellant. By 1955 the concept had developed, and a report co-authored by Ulam set out a better model: to propel a ‘projectile’ by the external detonation of nuclear bombs.
The government agency ‘ARPA’ (the ‘Advanced Research Projects Agency’) gave a million dollar contract to the General Atomics lab, near San Diego, to develop the idea into a working concept. General Atomics was set up after the Second World War to explore peaceful ways to use nuclear energy. The project was led by physicist Ted Taylor, with a team of scientists, many of whom had worked on the hydrogen bomb, including Stanislav Ulam himself, and the renowned British mathematician Freeman Dyson.
Although these physicists admittedly ‘enjoyed playing around with bombs’, they also dreamed of using their discoveries for constructive and humanitarian purposes. ‘Project Orion’ had obvious military uses, but the team focused on their vision for travelling to the far reaches of the Solar System: to transport a crew of hundreds of scientists to explore Mars, Venus and the moons of the gas giants.
The concept was simple and based on technology that was already available to the US military in the 1950s. A series of small nuclear bombs, each equivalent to 5 kilotons of TNT, would be ejected from the back of the ship, at a rate of 2 to 4 times per second. These bombs would be made to direct most of their energy towards the ships 1000-ton steel ‘pusher plate’ and this series of pulses would propel the huge spaceship forward.
To demonstrate the concept, the team at General Atomics built a 1 metre (or 3 foot) diameter model, shaped like a bullet, which they loaded with conventional explosive charges. Sure enough, the model cruised up into the sky, riding the chain of explosions with surprising stability. According to the calculations, the forces on a full-sized ‘Orion’ would be similar: between 2 and 4 ‘g’, comparable to a conventional rocket launch.
Nuclear Pulse rockets offered some significant advantages for spacecraft design. With this kind of propulsion, it would not only be possible to build heavier spaceships: it would become an advantage to ‘go big’. The ‘Orion’ spacecraft would already need to be heavy, to be able to absorb the forces of the nuclear ‘pulse’ through its pusher plate and giant shock absorbers.
So rather than using lightweight composite materials like the Apollo spacecraft, the payload and living quarters of ‘Orion’ could be made from ordinary steel. In the words of the physicist Harris Mayer, this would become a project of standard engineering, ‘like the Brooklyn Bridge’. To illustrate just how revolutionary this ‘space hotel’ would be, Ted Taylor suggested putting an ordinary barber’s chair on board.
The ‘Orion’ spacecraft would be constructed in submarine shipyards, and would be similar in many ways to the nuclear submarines already being built by General Atomics sister company General Dynamics. Both had to be able to support a crew for an extended trip, and withstand pressure: the vacuum of space being less punishing than the compression of a deep-sea dive.
Appropriately, the plan was to launch the ‘Orion’ spaceship at sea, just like the concept for the ‘Sea Dragon’ rocket, which was in development at the same time. Launching at sea removed the need for a huge launch pad, and avoided issues with deflection of debris during the first moments after launch. The sea-launch of ‘Orion’ would have been a spectacular sight: a succession of larger explosions lifting the giant spaceship up vertically, above a series of fireball clouds.
However, the General Atomics engineers faced unique and significant challenges. One of which was that the shock of each explosion could not so large as to injure the human occupants or shake the craft apart.
Freeman Dyson’s calculations showed that the manned ‘Orion’ spacecraft could absorb increments of around 10 metres per second of ‘delta v’, or speed change. Given that it takes a little less than 10 kilometres per second of ‘delta v’ to get a spacecraft into Earth orbit, ‘Orion’ would need to carry almost a thousand bombs to achieve this, and many more for interplanetary travel.
The effect of these bombs exploding in the atmosphere would be a lot of nuclear fallout: enough to directly cause up to 10 deaths worldwide, per launch. Unless a solution could be found to ‘clean-up’ the radioactive debris, this was a major obstacle in the way of ‘Project Orion’ becoming reality.
The high stakes of the Cold War pushed the development of the project onwards, towards potential military applications. Thomas Powers, second in command of Strategic Air Command reportedly said, “Whoever controls Orion will control the world.” However, when President Kennedy was shown a model of a militarised ‘Orion’ complete with nuclear missiles and atomic cannons as a monstrous orbital battleship, he was horrified, to Kennedy, the last thing the world needed was a huge nuclear weapons race in space.
‘Orion’ had been touted as an alternative to the Saturn rocket for the moon missions but NASA was a civilian and open organisation and Orion was still top secret and under control of the US air force. In fact many parts of the Orion project like the construction of the small cheap atomic bombs are still classified so as to keep the technology from falling in to the wrong hands.
Public mood was also shifting against the emerging nuclear-powered future. Strontium-90, a by-product of fission, had been detected in milk and in babies’ teeth. In the face of these health concerns, and the global panic of the Cuban missile crisis, Kennedy signed the Partial Nuclear Test Ban Treaty in 1963. This ruled out all above-ground nuclear testing, and effectively made ‘Project Orion’ unworkable – at least, in its original form.
To the scientists who had already spent five years working on the project, the technology was too powerful to ignore. After all, no other technology offered the same potential for taking large payloads to other planets. In 1964, NASA considered a smaller Nuclear Pulse rocket that could be launched aboard a Saturn V, and assembled in orbit. This would be an 8-man vehicle to go to Mars, or a 20-man vehicle to go to Jupiter. However, by this time, the Space Race was fully focused on a Moon landing, a job that didn’t need a rocket nearly as powerful as ‘Orion’.
Finally, in December 1964 the project was terminated. Chemical rockets, inefficient but relatively safe, would become the only option for getting off the Earth. For the time being, man’s course in space would follow a less ambitious trajectory.
Since ‘Project Orion’, the principles of Nuclear Pulse propulsion have been revisited many times. In 1968, Freeman Dyson wrote a paper entitled ‘Interstellar Transport’, in which he calculated that a version of the ‘Orion’ ship could travel to Alpha Centauri, our nearest star, at 10% of the speed of light, taking 44 years to arrive.
Five years after Dyson’s paper, the British Interplanetary Society conducted a study into a potential mission using Nuclear Pulse Propulsion. Known as ‘Project Daedalus’, the concept envisioned building a 190-metre (620-foot) long robotic spacecraft in Earth orbit, which would then travel to Jupiter to scoop 50,000 tons of Helium-3 fuel from the gas giant’s atmosphere. The fuelled ‘Daedalus’ would then accelerate out of the Solar System, reaching 12% of the speed of light, on a 50-year voyage to Barnard’s Star. However, unlike ‘Project Orion’, ‘Daedalus’ relied on nuclear fusion, a technology that is still out of reach.
According to George Dyson, son of Freeman Dyson, a team at NASA have a contingency plan to put Nuclear Pulse technology into action, if a large asteroid is discovered on a collision course with Earth. In such a situation, a version of ‘Project Orion’ might be our only chance, to deflect the asteroid earlier and with greater velocity than we could with conventional spacecraft.
With the cancellation of NASA’s Asteroid Redirect Mission in President Trump’s budget, a version of ‘Project Orion’ could still appear if the need arose in the future to change the course of human history.
This episode’s shirt was the Peacock fan shirt in Yellow by Madcap England and is available from www.atomretro.com/madcap_england with worldwide shipping from here in the UK.