NASA has made a series of critical strides in developing new nuclear reactors the size of a trash can that could power a human outpost on the moon or Mars.

Three recent tests at different NASA centers and a national lab have successfully demonstrated key technologies required for compact fission-based nuclear power plants for human settlements on other worlds.

"This recent string of technology development successes confirms that the fission surface power project is on the right path," said Don Palac, NASA's fission surface power project manager at the Glenn Research Center in Cleveland, Ohio, in a statement.

Power on the moon

NASA's current plan for human space exploration is to return astronauts to the moon by 2020 on sortie missions that could lead to a permanent outpost for exploring the lunar surface and testing technologies that could aid a manned mission to Mars.

The space agency has been studying the feasibility of using nuclear fission power plants to support future moon bases. Engineers performed tests in recent weeks as part of a joint effort by NASA and the Department of Energy.

Nuclear fission power plants work by splitting the nuclei of atoms in a sustainable, controllable reaction that releases heat, which can then be funneled through a power converter to transfer that energy into usable electricity.

A small fission-based nuclear reactor coupled with a Stirling engine could provide up to 40 kilowatts of usable energy, enough to support a moon base or Mars outpost, project scientists said. That's about the same amount of power needed to supply eight houses on Earth, NASA officials have said.

For comparison, the four giant solar arrays on the International Space Station can generate up to 120 kilowatts of usable power - about the equivalent to support 42 average-sized homes. They extend from a main truss as long as football field and make the space station easily visible at night on Earth to the unaided human eye.

Key milestones

In one of the recent tests, Palac's team subjected a lightweight radiator panel prototype to the vacuum conditions it would experience in space, as well as extreme cold (minus 125 degrees Celsius, or about minus 193 degrees Fahrenheit). The radiator is about 6 feet wide and 9 feet long, and one of 20 that would be required to keep a lunar fission reactor cool, project officials said.

A second fission power milestone included pumping molten liquid metal through a Stirling engine, an engine driven by heat, to simulate how heat from a nuclear reactor could be shunted to a converter to generate power. The test was carried out at NASA's Marshall Space Flight Center in Huntsville, Ala.

The third test bombarded a Stirling engine alternator with radiation, up to 20 times the cumulative dose allowed for today's fission power plants on Earth, to see how it would hold up. It passed with flying colors, NASA officials said. Engineers performed the 26-hour endurance test at the Sandia National Laboratory in Albuquerque, N.M.

"The pace of progress exhibited by these three achievements in the same time period is exciting," said Lee Mason, NASA's principal investigator for fission surface power at the Glenn Research Center. "It has built the team's confidence and prepared them for challenges that lay ahead."

The next step for NASA's fission power project is to combine its radiator, engine and alternator successes into a single non-nuclear power plant demonstration. That test is slated to begin in 2012, NASA officials said.