The NTR, or nuclear thermal rocket, was a propulsion system technology first tested in the 1960s by NASA and the Atomic Energy Commission (AEC). But it is a concept that traced its origins back to rocket pioneers Robert Goddard and Konstantin Tsiolkovsky.
The rocket known as NERVA (Nuclear Engine for Rocket Vehicle Applications) developed by United States scientists in the late 1960s and early 1970s worked by pumping supercold liquid hydrogen (-400┬║ F) into a chamber heated to 5,000┬║ F by a nuclear reactor. Once there, the scorched hydrogen atoms would instantly jump several thousand degrees, accelerate to supersonic speed, and explode out the engine's nozzle, creating enormous thrust - a pound of nuclear fuel contained 10 million times more power than a pound of conventional propellant.
NERVA rockets could, theoretically, have reduced the size, weight, cost and flight-time of long missions, all highly attractive qualities for the big dream, big business space age, but nuclear thermal rockets didn't get the chance to fly. When tight budgets struck NASA after the Apollo lunar missions, NERVA got the ax in favor of the flashy and reusable Space Transportation System shuttle.
