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Lightweight Radiation-proof Fabric?
kramer writes "New Scientist is reporting the creation of a lighweight radiation-proof fabric called Demron. Demron is being touted by its inventors as comparable to lead shielding at a fraction of the weight. Could be very useful for any future interplanetary space missions where the amount of radiation absorbed by the crew is a significant concern."
The electron clouds give an "illusion" of large atoms when viewed with gamma or X-rays. These electron configurations are just as effective for providing radiation obstruction as any heavy element such as lead or bismuth. Illusions can beget real effects if used correctly.
I'm sure you meant the fabric takes up less volume, as I would hope that weight is not an issue in space.
It seems reasonable that that gamma radiation (high energy photons) could be intercepted by a 'cloud of electrons' in the polymer in this material.
However, high energy neutrons would not interact with the electrons due to their high velocities. The relativistic effect of width/length contraction applies to these neutrons. This was the fundamental problem of early fission reactors - they had to moderate (reduce the speed of) the neutrons in order for them to appear big enough to interact with a nucleus. An electron is 1,836 times less massive than a proton. Thus you'd need 1836 electrons to equal one proton-with of neutron blocking power. I doubt they have that many electrons in the polymer's cloud!
However, any material that more effectively screens high energy photons is a welcome material. It would also be highly useful in creating X-Ray and Gamma-ray telescopes, methinks! NASA, you listening?
The article should have gone into which radiation types besides Alpha particles that it would block (Alphas I think are just Hydrogen nucleii - or is it Helium...).
Cosmic ray shielding would be useful on the ISS as well, but it would not stop relativistic particles, and it might break down under repeated insults of high energy collisions occurring regularly in space.
Any nuclear engineers out there who can comment better? go Navy?!?
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The researchers say it's comparable to lead shielding in terms of shielding radiation, but this does not quite address an important concern. Is it like lead shielding only with respect to nuclear radiation? Or x-rays and such as well?
I'm only asking because I'm trying to figure out whether Superman can see through it. Any help is appreciated.
-Lex.
Low-energy alpha & beta are easily blocked with century-old technology. Their explanation of how they block X and gamma sounds like smoke & mirrors to me.
BTW, '0.00% of gamma gets through' may be worse than nothing, since the secondary shower (from whatever the gamma ray hit) is often worse than the gamma.
It's easy to make up & spread cool- and credible-sounding stuff. Finding & checking hard facts is hard work.
I can finally look fashionable while thwarting the cia's mind readers instead of that baked potato look I had going for me.
Weight might not be a big issue once you are actually in space, however, it is a huge issue when it comes to getting there.
And once you're in orbit weight doesn't matter, but mass still does.
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I was a Navy nuke, so I know a thing or two about radiation. What people think of as "radiation suits" are not designed to shield radiation. They are used to prevent contamination. The suit prevents radioactive material from getting on your skin and clothes, so that you don't take it home with you. There are several kinds of radiation. Alpha particles are helium nuclei (He4). These particles are not dangerous unless you ingest or breathe them into your lungs. The dead layer of skin on your hand is enough to stop them. If they get into your body, they cause serious harm, as there is no "dead layer" of anything to stop them. Beta particles are electrons. They are light and fast, so they penetrate more. They will give you a dose to your skin, but not much deeper than that. A contamination suit can probably stop Betas. Even the old ones. Gammas are photons/electromagnetic radiation. Whatever you want to call them. X-Rays, microwaves, and radio waves all fall into this general category. The real biological hazard comes from the high energy particles/waves. These will pass right through your skin and can affect your internal organs. A contamination suit is not expected to reduce the dose from gammas. neutrons are produced in fission and some rare decay events, mostly shortly after a fission event. Neutrons are the only thing that can make something ELSE radioactive. Neutrons have no charge, so shielding them is difficult. It takes LOTS of lead or iron or water, etc. I don't care what their material is made of, if it's light enough to wear, it will not shield neutrons well. The web site said that it shileds low energy gammas, alphas, and betas. Low energy gammas don't cause much harm. Unless you work with a low energy gamma source on a routine basis, this material is not going to change your life. Or your life expectancy. This is my first post. Is it WAY too long? Sorry. -John
The article doesn't mention anything about the secondary emission characteristics of this fabric.
Secondary emissions are a very real bane of shielding for interplanetary travel, due to the extremely high energies of cosmic rays. Even if you could launch lead shielding for a spacecraft, manageable thicknesses would cause secondary emissions that were even more dangerous to the occupants than the original cosmic rays.
They've tried a new type of radiation shielding on the ISS made of polyethylene that is supposed to block without creating secondaries, and I see that's part of this fabric. Unfortunately the new shields don't seem to be as effective as hoped.
Radiation is anticipated to be a big problem on a Mars mission. IIRC, the radiation exposure will have a cancer risk equivalent to a lifetime of smoking.
But you really know to be scared of cosmic rays if they make rapping noises on your spacecraft, and upon return to Earth you start stretching, bursting into flame, become invisible, or turn into a pile of muscular orange bricks.
The living have better things to do than to continue hating the dead.
Check out their "test results." (PDF file) Go to page 3 to see the blocking power of their fabric.
Error #1: There is no such unit as a Kv. They mean KeV, as in Po-210 emits an alpha particle with 5,300 KeV of energy. But this is minor.
Error #2: X-rays and gamma rays are both photons; they're only distinguished by their energies. But the X-ray results and gamma ray results (which overlap in energy, which, in itself, makes no sense) contradict each other. For example, why does the fabric block only 52% of 60KeV gamma rays, but 82% and 72% of 50 and 70KeV X-rays respectively? Makes no sense, but this is nothing compared to...
Error #3: The real killer, and what makes me suspect this is fraud, rather than mere incompetence. They use 0.5 mm of lead as the comparison for their gamma emitter tests. The radiation-absorbing properties of lead are well known, and easily accessible in handy-dandy tables. For example, the half-value layer (the amount of material needed to block 50% of incoming radiation) for a Co-57 source is 0.15 mm of lead (ref here ), so 0.5 mm of lead should block more than 90% of the radiation, not just 52%. Proof positive that they're full of shit.
Fuck them, and fuck New Scientist. (Pardon my French.)