Slashdot Mirror
Star Trek Shields Now a Possibility?
An anonymous reader writes "British scientists have announced their intent to build a Star Trek-style magnetic shielding system to help protect astronauts from radiation. 'There are a variety of risks facing future space explorers, not least of which is the cancer-causing radiation encountered when missions venture beyond the protective magnetic envelope, or magnetosphere, which shields the Earth against these energetic particles. The Earth's magnetosphere deflects many of these particles; others are largely absorbed by the atmosphere.'"
This was reported on slashdot three years ago. The space.com article linked to from the 2004 slashdot summary is actually much more detailed in terms of the science. The big engineering problems with this approach still have not been solved. (1) If you're not using superconducting magnet coils, a large, static magnetic field requires a huge power supply to keep it going. That's not practical for foreseeable, near-future technologies for going to Mars, which will need to use very small payloads. (2) Superconducting magnets are unreliable, finicky beasts, at least from my experience here on earth. You need big, heavy cryostats full of liquified gases. It's not necessarily a good idea to have a vital piece of safety equipment for your spaceship depend on an inherently high-maintenance, low-reliability technology. (3) Large electric fields are hard to maintain because you get arcing and discharges. I used to work at an electrostatic accelerator that used megavolt potentials, and it would start sparking at the most inopportune times, for reasons like, e.g., someone leaving behind a speck of lint inside the accelerator. When a spark would happen, you could hear it all through the building, and the energy released was equivalent to dropping a VW bug off the roof of a building. Again, low-reliability, high maintenance. (4) Although it's possible to use tricks to get rid of some of the particles, or channel particles to a place where they're not as harmful, you still have to deal with the fact that you have particles with both signs of charge, which feel forces in opposite directions from the same field. What repels one attracts the other. Also, if the particles get channeled to a certain place, and impact on something solid, then you get extremely intense secondary radiation at that spot.
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So does that mean when went sent people to space before, they got exposed to all kinds of particals and stuff? Are they still ok? If so, then do we really need this? Or....did we fake the moon stuff?
Galactic cosmic rays are the biggest, most difficult problem. For a variety of reasons, explained in the WP link, they're not a big problem for low-earth orbit space stations like the ISS. The Apollo astronauts did get exposed to a lot of radiation, but they were only out for about a week, whereas an elliptical transfer orbit to Mars takes 1.4 years round trip in interplanetary space. For anyone who's actually had to wear a radiation badge to work, the integrated dosages they've estimated for a Mars issue just sound nuts, like somebody moved a decimal place over three places by mistake. It's a huge amount of radiation, roughly on the right order of magnitude to kill a human being. The Apollo astronauts got dosages at the level where there's speculation they may be getting cataracts at a significantly higher rate than normal. Scale that up by a ratio of 1.4 years to 1 week, and you get effects that are just not on the order of magnitude that you could laugh off heroically.
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