Fly me to the moon

Scientists at Ben-Gurion University of the Negev have shown that an unusual nuclear fuel could power space vehicles from Earth to Mars in as little as two weeks.

Standard chemical propulsion used in existing spacecraft currently takes from between eight to ten months to make the same trip. Calculations supporting this conclusion were reported in Nuclear Instruments and Methods in Physics Research A (455: 442-451, 2000) by Professor Yigal Ronen, of BGU’s Department of Nuclear Engineering and graduate student Eugene Shwagerous.

In the article, the researchers showed that the relatively rare nuclear material, americium-242m (Am-242m), can maintain sustained nuclear fission as an extremely thin metallic film.

In this form, the extremely high-energy, high-temperature fission products can escape the fuel elements and be used for propulsion in space. Obtaining fission-fragments is not possible with uranium-235 and plutonium-239 nuclear fuels, as they require large fuel rods, which absorb fission products.

To meet the challenge of a light nuclear reactor, Ronen examined reactor design and the use of nuclear fuel within it. He found at the time that of the known fission fuels, Am-242m requires one percent of the mass of uranium or plutonium to reach its critical state.

The study examined differing theoretical structures for positioning Am-242m metal and control materials for space reactors and determined that this fuel could sustain fission in the form of thin films that release high-energy fission products.

Ronen also showed how these fission products could be used as a propellant, or to heat a gas for propulsion, or to fuel a unique generator that produces electricity.

‘There are still many hurdles to overcome before americium-242m can be used in space,’ said Ronen. ‘However, I am sure that americium-242m will eventually be implemented for space travel, as it is the only proven material whose fission products can be made available for high speed propulsion. ‘