When will NASA develop a true 'nuclear' rocket engine?
We already have, in fact several times. All rockets work the same way. They throw things out one end of the spacecraft and this causes the spacecraft to move the opposite direction to conserve momentum. A nuclear reactor makes heat, and this can be used to drive a turbine to produce electricity, or to vaporize a fuel and expel it as rocket momentum (Nuclear Thermal Rocket Engine). In the former case, the electricity can be used to drive an ion engine, or a Mini-Magnetosphere Propulsion System. In 1959, NASA had a program called NERVA (1955-1961), but it was canceled soon after the 900-megawatt 'KIWI' nuclear rocket was test-fired. This was replaced by the Phoebus engine in 1965, which operated at 1,500 megawatts. The most powerful engine of all was the 5,000-megawatt Phoebus 2A tested in June 1968, which ran for 12 minutes at a temperature of 2310 K. The problem that engineers encountered with all of these engines was the erosion of the nuclear core by the flowing rocket gases. About 20% of the core would be ejected out the nozzle every 5 hours in a highly radioactive plume. Forty years later, Project Prometheus has been funded by Congress to develop a high-yield satellite nuclear power in the next 5 years at a cost of $3 billion. It is not specifically a plan to design a new rocket engine, but to create small reactors to power satellites and planetary rovers in deep space. As Ed Weiler, Chief of the Office of Space Science at NASA puts it, “For 40 years, NASA has been doing planetary science in the same way. That is, you accelerate for 5 to 10 or 15-minutes and then you stop…and you coast, and you coast, and you coast. Occasionally, Jupiter will be just in the right spot and you can get a little slingshot effect, but it’s not always there. That’s not the way to do exploration. That’s exploring the west by going in covered wagons,” NASA now has the green-light to build state of the art nuclear-electric generators that will carry us to the outer solar system, or to a new world of sophisticated energy-hungry planetary rovers. They will also be used to generate power for sophisticated high-acceleration ion engines.
