Nature – Fission power back on NASA’s agenda Michael Houts, nuclear-research manager at NASA’s Marshall Space Flight Center, wants astronauts to ride a nuclear reactor to Mars. He is convinced that small amounts of uranium-235 — which has an energy density one million times greater than that of liquid fuels — could power rockets efficiently, using the heat of fission to accelerate small stores of lightweight hydrogen propellant. This year, he is leading a nuclear-propulsion project with a budget of US$3 million — minuscule in comparison with the $1.3 billion that NASA will spend on space-technology research and development in the 2012 fiscal year. (H/T Hobby Space)
The US National Research Council report (Feb 1, 2012) Space Technology Roadmaps and Priorities is the first ever community-based document to set priorities for NASA’s space-technology division. Nuclear power and propulsion came high on the list.
Mason Peck, NASA’s chief technologist, says that he will use the priority list as a guide when setting funding in future. However, developing fission power for space will require not only money, but also political will: the image of a nuclear-powered spacecraft blowing up on the launch pad or on its way to orbit is a powerful deterrent. Houts says that the risk of nuclear material contaminating Earth after an accident is negligible because the reactor would not be started until the system were in orbit. Nevertheless, past attempts to demonstrate the technology have faltered. In 2003, NASA began Project Prometheus, which supported the development of a nuclear reactor that would drive an electric ion thruster to power a probe to Jupiter. The programme received as much as $430 million in 2005, but was cancelled a year later as NASA shifted its resources towards returning to the Moon — a destination for which nuclear propulsion was not needed.
Although the project has disappeared, it did support work that is now bearing fruit in the form of a new radioisotope power generator — a power source that does not use fission, but instead relies on the natural heat from the decay of plutonium. The Advanced Stirling Radioisotope Generator (ASRG) is lighter and more efficient than previous examples, and the space-technology report identified it as a “tipping point” technology that is almost ready for in-flight demonstration. Two mission proposals that include the ASRG — one to explore the hydrocarbon seas of Saturn’s moon Titan in a boat, the other to hop from comet to comet — are under consideration at NASA.