Lightweight Radiation-proof Fabric? 92
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."
Re:Imaginary Particles? (Score:5, Informative)
No, weight (Score:3, Informative)
Testing (Score:5, Informative)
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?!?
Re:Testing (Score:1, Informative)
radiation suits is a misnomer (Score:5, Informative)
Secondary emissions? (Score:4, Informative)
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.
Some Additional Information (Score:3, Informative)
Re:Testing (Score:5, Informative)
As it turns out, sometimes you can pack lighter weight nuclei close enough together that you get a similar electron density to metals (or even higher sometimes). this is probably what they've done with this 'polymer'. Althogh on a mailing list I'm on, someone mentioned that the material was just fabric that had been soaked in a barium solution and dried. Whether that was true or not was never establised though.
There is one incorrect statement in the article though.
Alpha particles can be emitted with extremely high energies, upwards of 10 MeV. What makes alpha particles so non-penetrating is their charge. Their +2 charge causes them to interact very strongly with neighbouring electrons, which causes them to lose energy quickly. That's also the reason why there isn't any special shielding necessary for alpha particles. Most alpha particles will be stopped in the dead layer of your skin, and therefore pose little external hazard. What makes alpha particles dangerous is if they become internalized (inhaled or ingested). The fact they lose energy quickly means that energy is transferred to whatever material it happens to collied with, causing much damage in the process.
Re:Underwear (Score:3, Informative)
This is bullshit and I can PROVE it. (Score:4, Informative)
Check out their "test results." [radshield.com] (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 [stanford.edu] ), 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.)
Re:Testing (Score:2, Informative)