Since the development of nuclear bombs in the 1940s, suggestions have been made for possible civilian peaceful uses of these powerful explosives. The United States explored some of these possibilities in Operation Plowshare and the Soviet Union worked on them in their Nuclear Explosives for the National Economy program. The primary use was for large scale earth moving but there were other uses such as seismic exploration and sealing major leaks in gas fields that were considered. Despite the hostility between these two nations during the Cold War, there were several bilateral conferences where scientists from the two nations compare notes on their experiments. After over one hundred explosions were triggered during the tests, in the end, both of these projects were cancelled due to technical problems, environmental pollutions and public opposition. Since the Soviet ended its program in 1989, there have been no other serious explorations of peaceful use of nuclear explosions.
One project that was proposed in the U.S. but never developed involved the use of nuclear explosions to power a spaceship by what was called Nuclear Pulse Propulsion. A company called General Atomics initiated research into such possibilities in what was called Project Orion in 1958.
The basic concept was to build a spaceship that would have a shock absorbing disk on the back end. Nuclear bombs, either fission or fusion, would be tossed out of a hole in the center of the disk and their explosions would accelerate the ship. Theoretically, the idea was found to be quite attractive. Space propulsion systems are rated on “thrust” and “specific impulse”. The thrust is a measure of how much force the propulsion system can generate. To launch a vehicle into space, the thrust must be greater than the force of gravity, analogous to horsepower in a car. Specific impulse is a measure of how much speed can be generated by a unit mass of propellant, analogous to miles per gallon in a car. Usually, in space propulsion systems, there is a trade-off between thrust and specific-impulse but for the proposed nuclear propulsion has both high thrust and high specific impulse.
One drawback of the NPP engine is the fact that its thrust comes in the form of explosive bursts. This means that there must be a way to absorb the shock of each blast and protect the rest of the ship from being shaken apart by changing stresses. In addition, there is the problem of intense radiation from the bomb blasts. The rest of the ship and especially the crew must be protected from the radiation. The shock absorber disk can also provide shielding. The design of such a craft would be long and thin with the engine on one end and the crew quarters as far away as possible on the other end.
With the passage of the Partial Nuclear Test Ban Treaty in 1963 which prohibited nuclear explosion in space, interest in Project Orion waned and the project was dropped in 1965. Through the years since, a number of studies have been done on different configurations of shape and nuclear propulsion for interstellar craft for exploring beyond the solar system. Some of these designs would utilize a greater number of small nuclear explosions from pellets as opposed to the nuclear bombs envisions for Project Orion.
Artist’s conception of a Project Orion vehicle from NASA:
