In OTL, a nuclear propulsion project from the 1950's called Project Orion was in development. It would have used nuclear explosions to power a spacecraft, faster and more efficiently than chemical rockets. Lack of funding slowed the project and it was finally canceled due to the Partial Test Ban Treaty of 1963 (hereafter referred to as PTBT), which banned nuclear explosions in space, in the atmosphere, and underwater. What would have happened had Orion reached its potential?