Earth to Mars In Two Weeks?

Waves writes "Scientists at Ben-Gurion University have shown that an unusual nuclear fuel could send space vehicles from Earth to Mars in as little as two weeks. Spacecraft now take between eight and 10 months to make the same trip. Instead of using Plutonium-239 or Uranium-235 The research shows a fairly rare nuclear material, americium-242m (Am-242m), when used as an extremely thin metallic film, is capable of sustaining nuclear fission at 1% of the mass of Plutonium." Interesting. But unless I'm totally mistaken, the thermal generators on spacecraft are used only for electricity, not propulsion, at the current time.

Comments

Space is too big to pollute. *think* about it.

[Christopher Thomas]

Several generations from now, will our children look back and wonder how we could have recklessly polluted space like that?

Um, if we took the entire mass of our *planet* and spread it around the inner solar system as a dust cloud, it wouldn't have any environmental effect on other planets in the vicinity.

How's the exhaust from a probe supposed to do anything?

I'm overlooking the fact that cosmic rays already send more hard radiation through the inner solar system than we could ever hope to put there.

The only legitimate concern is dumping radioactive waste just above the Earth's atmosphere. The simple solution: shield the ship until you're far away from Earth!

Pollution in deep space is a non-issue.

Exhaust radioactivity.

[Christopher Thomas]

My question is, what ARE the byproducts of this process, and are they radioactive? Would a drive based on this process wind up spitting out a radioactive plume?

That depends on which isomer of Am242 they're referring to ("m" denotes an isomer, a metastable energetic state of Am242 with its own decay properties). According to the handy description of Am242 at http://environmentalchemistry.com/yogi/periodic/Am -pg2.html , most of the decay chains involve alpha and beta emissions, which will (hopefully) leave the Americium atoms in the film on the engine. A few low-probability reactions (or one high-probability reaction for the most energetic isomer of Am242) result in spontaneous fission, which will indeed send a likely-radioactive fragment out into space.

They key words here are "into space". This drive will never produce enough thrust to be useful for lifting off of a planet; the exhaust throughput is far too low. Out in space, a few traces of radioactive atoms are a non-issue (we already have plenty streaming down in the form of cosmic rays).

I'm glad you read it; don't jump to conclusions.

[Tau Zero]

My question is, what ARE the byproducts of this process, and are they radioactive?

If they are fission products from a trans-uranic element, they will certainly include radionuclides. There's no avoiding it.

Would a drive based on this process wind up spitting out a radioactive plume?

But of course. The only way to use a foil-thin material for a fission drive would be to use it to paper the back of the ship, so that particles emitted from the fission escape backwards. There's your plume.

If so, NO THANKS.

Why? The material in said plume would be taken up by the solar wind and swept out of the solar system within a few weeks. It would be the ultimate in non-persistent problems. It would join a galaxy full of stuff being bombarded by cosmic rays and other nasties, and even if there were fleets of these things running you'd have to be looking for the tiniest of traces of stuff "downwind" to detect their exhaust. The Sun blows an amazing amount of stuff into space every second (part of it radioactive), and rockets like this would be like a fart in a hurricane.

The thing I find most interesting, and which is not addressed in the article (dammit), is whether Am-242m emits its fission/decay products in any particular direction relative to the spin axis of the nucleus. If the nucleus can be aligned with a magnetic field so that the fission products go backwards, that would be a tremendous advantage for propulsion. One more thing to look up when I get home, if it's even mentioned in my table of the isotopes...

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