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Earth to Mars in two weeks

By Dacta in MLP
Thu Jan 11, 2001 at 03:25:12 AM EST
Tags: Science (all tags)
Science

Canada's CBC is carrying a story about research into using films of americium-242m as a fission fuel instead of uranium of plutonium rods.

Using this thin-film technique, researchers can produce the same power as a uranium or plutonium reactor using only one percent of the fuel mass.


The application pointed out in this article is space travel - because of the potential weight savings, it would be possible to use this in a spacecraft. This could allow continuous power during a mission from earth to mars, rather than the "blast off and gravity-slingshot" mission profiles which are currently used. They claim this would the in-flight time from 8 months to 2 weeks. I suspect this estimate may be a little optimistic, but there is no doubt dramatic time savings are available using continuous acceraration if the power was available.

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Earth to Mars in two weeks | 32 comments (5 topical, 27 editorial, 0 hidden)
Official Press Release (5.00 / 2) (#27)
by Eloquence on Thu Jan 11, 2001 at 12:41:57 AM EST

Not much different from the article (so much for investigative journalism), but here's it anyway. Does anyone know of any fundamental arguments against this?

Department of Public Affairs
Ben-Gurion University of the Negev
P.O. Box 653
Beer-Sheva, Israel

For further information, please contact:
E. Tepper, Department of Public Affairs
Tel.: 972-8-646-1283; Fax : 972-8-647-2937
E-mail: tepperel@bgumail.bgu.ac.il

EXTREMELY EFFICIENT NUCLEAR FUEL COULD TAKE MAN TO MARS IN JUST TWO WEEKS

Beer-Sheva, December 28, 2000 -- Scientists at Ben-Gurion University of the Negev have shown that an unusual nuclear fuel could speed 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 this month's issue of Nuclear Instruments and Methods in Physics Research A (455: 442-451, 2000) by Prof. Yigal Ronen, of BGU's Department of Nuclear Engineering and graduate student Eugene Shwagerous.

In the article, the researchers demonstrate that the fairly rare nuclear material americium-242m (Am-242m) can maintain sustained nuclear fission as an extremely thin metallic film, less than a thousandth of a millimeter thick. 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 the better-known uranium-235 and plutonium-239 nuclear fuels: they require large fuel rods, which absorb fission products.

Ronen became interested in nuclear reactors for space vehicles some 15 years ago at a conference dedicated to this subject. Speaker-after-speaker stressed that whatever the approach, the mass (weight) of the reactor had to be as light as possible for efficient space travel. At a more recent meeting, Prof. Carlo Rubbia of CERN (Nobel Laureate in Physics, 1984) brought up the novel concept of utilizing the highly energetic fragments produced by nuclear fission to heat a gas; the extremely high temperatures produced would enable faster interplanetary travel.

To meet the challenge of a light nuclear reactor, Ronen examined one element of reactor design, the nuclear fuel itself. He found at the time that of the known fission fuels, Am-242m is the front-runner, requiring only 1 percent of the mass (or weight) of uranium or plutonium to reach its critical state. The recent study examined various theoretical structures for positioning Am-242m metal and control materials for space reactors. He determined that this fuel could indeed sustain fission in the form of thin films that release high-energy fission products. Moreover, he showed how these fission products could be used themselves as a propellant, or to heat a gas for propulsion, or to fuel a special generator that produces electricity.

"There are still many hurtles to overcome before americium-242m can be used in space," Ronen says. "There is the problem of producing the fuel in large enough quantities from plutonium-241 and americium-241, which requires several steps and is expensive. But the material is already available in fairly small amounts. In addition, actual reactor design, refueling, heat removal, and safety provisions for manned vehicles have not yet been examined.

"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. Indeed, Carlo Rubbia has also recognized that this is the most probable fuel that will be getting us to Mars and back. I think that we are now far enough advanced to interest international space programs in taking a closer look at americium-based space vehicles."

For photographs, please contact:

Amir Rozenblit, BGU Spokesman
Tel.: 972-8-6461802 / 972-8-6477717/6
Fax: 972-8-6472803
E-mail: rosenbli@bgumail.bgu.ac.il
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Limiting factor (5.00 / 2) (#29)
by StrontiumDog on Thu Jan 11, 2001 at 04:55:18 AM EST

I suspect the greatest contributor to the mass of a nuclear propelled rocket is not the mass of the isotopes, but the propellant mass. In a nuclear propelled rocket propellant (eg water, or liquid hydrogen) is heated by the nuclear engine and expelled to provide thrust. The Bimodal Nuclear Thermal Rocket for instance, uses only 35 kg of uranium to generate heat. Considering that the crew on such a rocket needs to be shielded against radiation from the reactor, and that an elaborate refrigeration system is needed to prevent the liquid hydrogen used as propellant from evaporating,I think the weight of the fissile fuel is not particularly significant.

[ Parent ]
potential weight savings? tell that to Oprah! (2.00 / 1) (#30)
by WinPimp2K on Thu Jan 11, 2001 at 10:18:10 AM EST

Am-242 has a half life of 16 freaking hours, given the problems in keeping H-bombs viable because their tritium tends to decay, just how long would this "thin film" of Americum remain capable of sustaining fission? I suspect you'd have to take a fuel plant to manufacure your Am-242 to order (it is a synthetic isotope after all).

Besides it is inherently obvious to all right thinking citizens of the world that Francium is far superior to Americum for this application.
Ok, this a blatant attempt to curie favor with the non-Americentric readership - so sioux me.

half-life (5.00 / 1) (#31)
by loner on Thu Jan 11, 2001 at 11:28:53 AM EST

The articles talk about AM-242m (an isomer of AM-242) which has a half-life of about 140/150 years. According to this site:
...The Am-242m isotope is produced from 241Am(n,g) and has a half-life of about 152 years...


[ Parent ]
half life (none / 0) (#32)
by WinPimp2K on Thu Jan 11, 2001 at 01:55:44 PM EST

My bad. Nookuleer fizzics isn't my strong suit
So what we gain is the ability to use a relatively unshielded reactor as we will exhaust the fission byproducts with our more conventional reaction mass? Storage of the fissile material might still be an interesting problem (maybe two rolls of tape that have offset checkerboards of Am-242m. while separate, they won' be able to sustain a chain reaction, when stuck together...

Still think Francium would be better. no wait, lets use anti matter. Surely no one could find political objections to powering our spaceship with Anti-Americum?

[ Parent ]
Earth to Mars in two weeks | 32 comments (5 topical, 27 editorial, 0 hidden)
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