OpenGov - Open Government Brainstorm

Back in the 1960s NASA experimented with the idea rocket engines powered by a nuclear reactor. The original prototype was crude and would have emitted radioactive material into the air, but the basic idea was sound -- using the energy of nuclear fission to heat your propellant instead of using chemical combustion.

The original prototype was based on a conventional reactor with a core of plutonium. Such solid-core reactors can only operate at about 3500 degrees before melting. But there's a newer concept for a Gaseous Core reactor that hasn't been explored. In this model a cloud of gaseous uranium is held compressed in the center of a transparent sphere by another gas swirling around the inside of the sphere. Because the fissioning uranium isn't touching anything it can be allowed to get up to 25,000 degrees, emitting intense ultraviolet light. Ordinary hydrogen pumped past the outside of the sphere absorbs the ultraviolet energy, heats and expands, and exits through the rocket nozzle, propelling the rocket.

About radiation: The exhaust from this rocket would be non-radioactive hydrogen. The radioactive nuclear fuel stays sealed inside the sphere, and there isn't that much of it. Even if one of these rockets blew up in the atmosphere, it would release less than 1% of the nuclear material released by a typical 1950 A-bomb test. It's simply not a concern.

A nuclear rocket the size and weight of the Saturn V model that was used in the Apollo moon program, could carry one thousand tons of payload into Earth orbit (more than 30 times what the space shuttle can carry), then return to make a powered landing on Earth, where it would be refueled and used again. This would mean carrying up entire space hotels in a single launch, or powering heavily equipped Mars missions with large crews and ample supplies. No more disposable rockets or tanks. No more scrimping on every gram of weight. Actual space ships.