A joint space programme involving NASA and the Atomic Energy Commission (AEC) 1959–72 to develop nuclear propulsion for a rocket. NASA and the AEC oversaw the building of 20 nuclear-reactor rocket engines that were tested at the US government's Nevada Test Site. The programme was slowed in the 1960s by public reactions against nuclear power, resulting in its cancellation in 1972. NERVA was an outgrowth of the Project Rover nuclear rocket programme begun in 1955 by the AEC and the US Air Force.