While the US and the Soviet Union were beginning work on NTR systems, a group of American researchers also considered a more direct and dramatic way to use nuclear power to propel a spaceship: detonate small atomic bombs behind it. The ORION project, as it was named, seems to have originated with Dr. Theodore B. Taylor, well-known nuclear weapons designer. In 1957, he was working at General Atomic, a branch of the General Dynamics conglomerate, in San Diego, California, when the Soviet Union launched Sputnik I, the first Earth satellite. General Atomic was promoting the peaceful uses of atomic power, and Taylor thought that America could catch up with the Soviets by building a really big spacecraft, a true “spaceship”, powered by atomic bombs.
- The idea of a spaceship powered by atomic bombs had been around for a few years, but nobody had done any more than some conceptual paper studies of the idea. Taylor did some paper studies of his own and came to the conclusion that the bombs would be small as such things went, with only a few kilo-tonnes of explosive yield. Even at that size, they would be about a million times more powerful than a chemical rocket. Taylor’s initial studies led to the establishment of PROJECT ORION in mid-1958. Dr. Freeman J. Dyson, now famous both for his work in theoretical physics and for his brilliant speculative books, was then at the Institute for Advanced Studies at Princeton, New Jersey. He was contacted by Frederick de Hoffman, who had founded General Atomics, and told about the ORION concept. Dyson so intrigued that he took a leave of absence to go west and work on the ORION. Ultimately 19 people worked on the project, which was kept a deep black secret. * As Taylor explained it: “The general idea was that you if explode a bomb with roughly the yield of the one that destroyed Hiroshima or Nagasaki, then anything within a few hundred feet of that would be vaporized instantly. And that was not true.”
The ORION team visualized their spaceship as something like a giant inverted pot or metal beehive, with a heavy “pusher plate” on the bottom. A “gun” ran down the center of the ship, ejecting a sequence of small nuclear bombs through a hole in the plate. The bombs were detonated a few hundred meters behind the spacecraft, and the plasma shock wave of the explosion boosted the ship through space. The ship was seen as about 30 meters tall and 30 meters in diameter at the base. The pusher plate covered the bottom and was envisioned as about 30 centimeters (a foot) thick. The group began to conduct small-scale experiments at the Point Loma Navy Base outside San Diego, with funding provided by the new US Advanced Research Projects Agency (ARPA). The researchers focused on the construction of 1:30 scale models driven by plastic explosives. The models were known as “Put-Puts” or “Hot Rods”.
The initial experiments were intended to determine if a pusher plate could actually stand up to a sequence of explosions. The tests showed that the pusher plate tended to bend inward at the middle, and so it was redesigned to be thick at the centre and taper outward towards its edge. The next problem was “ablation” of the pusher plate, the boiling away of the surface of the plate with each atomic blast. This required appropriate selection of a plate material. A number of candidates were considered, with some sort of fibreglass heading the list. Spacing of the bomb detonation behind the ship was also important. Too close and the ship would be destroyed; too far away and the energy of the blast would be wasted. Another problem was the protection of the crew from the radiation of the blast. Surprisingly, fibreglass turned out to work fairly well as a radiation shield. The ORION design also had a special compartment that was heavily shielded where the crew would go during the intermittent “boost phases” of the ship. The ship was to be launched from a barge far out in the ocean to reduce the effects of the blasts on the environment.
Unfortunately, ORION would leave a trail of radioactive debris or “fallout” as it climbed into the sky. It was possible to design the bombs to be relatively “clean” to minimize the fallout, and they were small to begin with, but it was not possible to eliminate the fallout completely. The bombs were actually known as “nuclear pulse units (NPUs)”, and they resembled big hockey pucks. ORION would carry several thousand of them. They were stacked around the breech of the gun in the middle of the spaceship so they could be automatically loaded, ejected, and detonated. Another problem was the shock of the explosions, since the gee forces of the blasts could destroy the ship or crush the crew. Some of the subscale models were simply blown apart in tests, and the group tried to insert shock absorbers between the pusher plate and the ship. One shock absorber design consisted of a stack of inner tubes, wrapped with duct tape for reinforcement.
Developing a reliable shock absorber system proved troublesome. A particular problem in terms of shock protection was the stack of nuclear pulse units carried by the ship, since the gee forces could easily wreck their precision fusing circuitry, turning them into duds. The bombs were to be mechanically “hardened” and fitted with their own shock absorbers to protect them.
On 12 November 1959, the group successfully launched a Hot Rod flight-test prototype that reached an altitude of 30 meters and parachuted successfully back down to the ground. Films of the Hot Rod blasting up into the sky on successive explosions remain an astonishing testimonial to the ingenuity of the ORION team. Even some of the team was surprised that the thing flew. The ORION team had big ambitions. They felt that a full-scale ORION spaceship would be able to tour the Solar System, for example reaching Jupiter after a year’s flight time. The ship wouldn’t be a cramped space capsule, either. Although 30 meters doesn’t sound very tall for a rocket, unlike a chemical rocket, which is mostly fuel tanks, ORION would be mostly payload.
The ORION team envisioned their spacecraft as having a cafeteria, an observation deck, a small hydroponics greenhouse, even a barber shop. When in May 1961, US President John F. Kennedy announced that America would put a man on the Moon by the end of the decade, the ORION workers smiled, thinking they could be headed for Saturn by then. However, the visionary nature of the project and its secret status worked against it. ARPA funding had dried up in late 1959. The ORION group managed to get more money from the US Air Force, though the military was sceptical of the idea and only provided funding for feasibility studies, not for further Hot Rod flights.
The ORION group approached NASA as well. Ted Taylor briefed Werner von Braun of NASA and other NASA officials about ORION to see if he could get support from the agency. Von Braun dozed through the briefing until Taylor showed the spectacular HotRod launch film. Von Braun went immediately alert and started to shower Taylor with questions. Von Braun became a believer, but though NASA funded further studies on ORION, it wasn’t enough to save the project. The agency was simply not comfortable with the idea — it was too different, too risky.
