Project Orion (nuclear propulsion)

Project Orion was a study conducted in the 1950s and 1960s by the United States Air Force, DARPA, and NASA into the viability of a nuclear pulse spaceship that would be directly propelled by a series of atomic explosions behind the craft. Early versions of the vehicle were proposed to take off from the ground; later versions were presented for use only in space. The design effort took place at General Atomics in San Diego, and supporters included Wernher von Braun, who issued a white paper advocating the idea. Non-nuclear tests were conducted with models, but the project was eventually abandoned for several reasons, including the 1963 Partial Test Ban Treaty, which banned nuclear explosions in space, and concerns over nuclear fallout. Physicist Stanislaw Ulam proposed the general idea of nuclear pulse propulsion in 1946, and preliminary calculations were made by Frederick Reines and Ulam in a Los Alamos memorandum dated 1947. In August 1955, Ulam co-authored a classified paper proposing the use of nuclear fission bombs, "ejected and detonated at a considerable distance," for propelling a vehicle in outer space. The project itself began in 1958, and was led by Ted Taylor at General Atomics and physicist Freeman Dyson who, at Taylor's request, took a year away from the Institute for Advanced Study in Princeton to work on the project. In July 1958, DARPA agreed to sponsor Orion at an initial level of $1 million per year, at which point the project received its name and formally began. The agency granted a study of the concept to the General Dynamics Corporation, but decided to withdraw support in late 1959. The U.S. Air Force agreed to support Orion if a military use was found for the project, and the NASA Office of Manned Spaceflight also contributed funding. The concept investigated by the government used a blast shield and shock absorber to protect the crew and convert the detonations into a continuous propulsion force. The most successful model test, in November 1959, reached roughly 100 meters in altitude with six sequenced chemical explosions.