Tuesday, November 28, 2006

How To Protect Yourself From Cosmic Rays If You Ever Happen To Make It Into Space

This one is fun. Remember back in September when the poor commander got lost on Mars and couldn't understand Base's instructions? No? Okay, go here first and refresh your memory. I'll wait... Finished? Then we're ready to move on. Since you've now done your homework, you know that the reason the Mars mission was in jeopardy was that the crew's brains were being scrambled by radiation. Radiation is a big problem that scientists are going to have to figure out before humans start heading out past the protection of the Earth's magnetic field, beyond the orbit where the International Space Station flies above the Earth in relative safety. The Moon and Mars, as we all know, are on the short list for mission possibilities, and spending such long periods of time in space could do more than scramble a few brain cells; if current theories are correct, astronauts could be risking premature aging by heading out into the cosmic ray zone. (That last link leads to an interesting article about space radiation, telomeres, Einstein and pills to repair DNA damage--I followed a link from there to one about what the heck telomeres are, and how they affect aging, with possible implications for human life extension. Pretty interesting if you want to follow some rabbit trails.)

All of that aside, however, what I really want to tell you about is the idea some scientists have for blocking all that radiation, so that no astronautical DNA is damaged in the first place. Patrick L. Barry wrote an article for NASA about how they are looking to make space ships out of a revolutionary new material--you're not going to guess this one in a million years. (Well, okay, I wouldn't have guessed it in a million years.) The material? Plastic. Polyethylene, to be precise. This is what they use to make the plastic trash bags of which we all have an abundance under our kitchen sink.

Most household trash bags are made of a polymer called polyethylene. Variants of that molecule turn out to be excellent at shielding the most dangerous forms of space radiation. Scientists have long known this. The trouble has been trying to build a spaceship out of the flimsy stuff.

But now NASA scientists have invented a groundbreaking, polyethylene-based material called RXF1 that's even stronger and lighter than aluminum. "This new material is a first in the sense that it combines superior structural properties with superior shielding properties," says Nasser Barghouty, Project Scientist for NASA's Space Radiation Shielding Project at the Marshall Space Flight Center.

To Mars in a plastic spaceship? As daft as it may sound, it could be the safest way to go.

According to Barry, one of plastic's big selling points is that when radiation smashes into it, it doesn't produce nearly as much "secondary radiation" as materials like aluminum or lead. That secondary radiation can be just as much of a problem for astronauts as the cosmic rays themselves:
The advantage of plastic-like materials is that they produce far less "secondary radiation" than heavier materials like aluminum or lead. Secondary radiation comes from the shielding material itself. When particles of space radiation smash into atoms within the shield, they trigger tiny nuclear reactions. Those reactions produce a shower of nuclear byproducts -- neutrons and other particles -- that enter the spacecraft. It's a bit like trying to protect yourself from a flying bowling ball by erecting a wall of pins. You avoid the ball but get pelted by pins. "Secondaries" can be worse for astronauts' health than the original space radiation!
Barry says the lighter elements of hydrogen and carbon, the building blocks for those plastic bags, won't completely stop the space radiation, but can fragment that radiation so that it is much less harmful. He uses the example of a chain link fence blocking a snowball. Some snow still gets through, but it doesn't hurt as much. This author has a knack for making scientific-speak understandable, doesn't he? I'll let him tell you more:

Despite their shielding power, ordinary trash bags obviously won't do for building a spaceship. So Barghouty and his colleagues have been trying to beef-up polyethylene for aerospace work.

That's how Shielding Project researcher Raj Kaul, working together with Barghouty, came to invent RXF1. RXF1 is remarkably strong and light: it has 3 times the tensile strength of aluminum, yet is 2.6 times lighter -- impressive even by aerospace standards.

"Since it is a ballistic shield, it also deflects micrometeorites," says Kaul, who had previously worked with similar materials in developing helicopter armor. "Since it's a fabric, it can be draped around molds and shaped into specific spacecraft components." And because it's derived from polyethylene, it's an excellent radiation shield as well.

They're working on ways to address some of the drawbacks that come with polyethylene--like the irritating tendency it has to burn and melt and whatnot. Now, this article is over a year old, and my search on the NASA site didn't lead me to any more updated information, so I can't tell you right now how this research is progressing. Back in August of 2005, no one was sure yet whether plastic really could serve as a shield to make space travel safer, but "hypothetically" polyethylene might be "not just for trash bags anymore."

It's so interesting how many useful discoveries for right here on Earth come out of space research. Man may never fly to the Moon in a plastic rocket. We may never see plastic habitats on Mars, but--and this is important--we can be pretty sure that our garbage will never get cancer from radiation!! That's an encouraging breakthrough, right? Even more valuable, now that we've all read the reports from NASA and know how useful plastic bags can be, we can make the important fashion decision about whether we want to wear plastic bags over our clothes when we go outside, to protect ourselves from cosmic rays. Hey, come on, it's not such a bad idea. If enough of us do it, it could even become trendy. Maybe if we get some Hollywood type to do it first we can all pretend it's actually cool. Then we would just look like lemmings, and not freaks. Hmmm. Let me think about this. Somebody sci fi maybe, but with crossover appeal.... I've got it! Will Smith!! Men In Black, I Robot, Independence Day... yeah, he'd do nicely. Somebody out there want to volunteer to suggest it to him?

Note: Yes, I know I'm being goofy today. I can't seem to help myself. I start out with a perfectly reasonable piece about the science of using plastic as a radiation shield and end up looking to make Will Smith the poster boy for the tinfoil hat brigade (plastic bag, tinfoil hat--same difference.) I'll try to control myself now, but I make no promises. I have a very good excuse. The day started out with snow, and that always gets me a little giddy. Wait a minute... Snow comes from the sky. Cosmic rays come from the sky, too. Maybe I'm so goofy because the cosmic rays are making it past the Earth's magnetic field and sneaking down into my neighborhood disguised as snow!!! This could be a real problem. I better go put on some plastic bags just in case.