 From 1957 to 1961 Dyson worked on Project Orion, which proposed the possibility of space-flight using nuclear pulse propulsion.A prototype was demonstrated using conventional explosives, but the 1963 Partial Test Ban Treaty, in which Dyson was involved and which he supported, permitted only underground nuclear weapons testing, and the project was abandoned in 1965.In 1958 Dyson was a member of the design team under Edward Teller for TRIGA, a small, inherently safe nuclear reactor used throughout the world in hospitals and universities for the production of medical isotopes.