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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. 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.
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.
There are several ways of getting nuclear thrust effects. This method uses the energy of the atom fragments as well. In fission-fusion bombs special beryllium-copper mirrors direct these fission products, X-rays, neutrons, and etc. down beam channels to fire the secondary system.
In the ORNL fireball type reactor much of the relativistic energy is released as well, in the form of neutrons, x-rays, and gamma rays. Similarly, these emissions can be reflected using mirrors from omnidirection emissions into directed emissions. The net effect is similar to ion drive system, except vastly more powerful.
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A fission fragment engine is an interesting idea, but overall much too scarry and expensive. Americium-242m, if it does undergo fission so easily, would be very dangerous to handle and never save enough to launch into space in any useful quantity. Uranium and Plutonium will just sit there unless the reactor is carefully powerd up, even if the reactor blew up during launch. Controlling such an engine would also be a serious concern, since if you couldn't turn the thing off reliably then it isn't going to take you anywhere. It will also require seriously heavy radiation shielding most likly, the weight of which would largely counteract the efficency... this is a radiation engine after all. Oh, and it would probobly not generate very much thrust either.
And Am-242m, the metastable isotope, would be EXTREMELY expensive to make in any quantity, and it would never be cheap enough for routine flights.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Dude, people are talking about freakin ANTIMATTER in this thread are you kidding! Americium is inert compared to antimatter. It is several orders of magnitude more stable, inexpensive to produce and safer to use. Not to mention of course that Americium represents a material and related technology that actually exists in the real world and can actual be employed in the near term. At the rate things are going, we'll be lucky to do anything productive with animatter in this century. People might want to make a more serious consideration of technologies,systems and materials that have a realistic chance of being used in space travel in our lifetimes! Just a friendly suggestion!
Charlie
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