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Solar Flares Shield Astronauts from Cosmic Rays
It doesn't come easy writes "Considering all of the research into better shielding for astronauts, it's interesting to note that solar flares can help shield space travelers from dangerous cosmic rays. From the article: "The crew of the ISS absorbed about 30% fewer cosmic rays than usual [during this last month of high solar activity]," says Frank Cucinotta, NASA's chief radiation health officer at the Johnson Space Center. "The storms actually improved the radiation environment inside the station." Scientists have long known about this phenomenon. It's called a "Forbush decrease," after American physicist Scott E. Forbush, who studied cosmic rays in the 1930s and 40s. So, I guess it would be safer to plan a manned Mars mission to coincide with peak sunspot activity?"
So, I guess it would be safer to plan a manned Mars mission to coincide with peak sunspot activity?"
How about having the spacecraft generate its own external magnetic field? How effective would that be?
"So, I guess it would be safer to plan a manned Mars mission to coincide with peak sunspot activity?"
No, the real answer is to have space missions start on Sun-days. har har har har.
Well, that could be a logical conclusion from the article. BUT, what also occurs during major sunspot activity?. Mondo solar flares! Yes, they may help suppress the Cosmic Radiation. But, I sure wouldn't want to be stuck somewheres in the vast space between Mars and Earth with one of these monsters heading for me. The spaceship would be hit like a rowboat in a hurricane, in terms of solar radiation.
Hence its hardly a perfect testbed for radiation effects regarding long-term space flights. You have to wonder if the factored in the change solar activity makes to the earth's magnetic field when putting this all together.
NASA Science News for October 7, 2005
Another source:
Strange, but true: Solar flares can be good for astronauts.
Saskboy's blog is good. 9 out of 10 dentists agree.
Even if I'm off by many orders of magnitude (IANAP), the required field strength will be unattainably high.
Two wrongs don't make a right, but three lefts do.
I once had a chat with a NASA biomedical researcher who told me that astronauts in space occasionally see flashes of light. These flashes coincide with cosmic rays destroying cones and/or rods in their retina. Not a pleasant thought if you ask me.
Of course, these same cosmic rays will also destroy cells in the brain and fragment DNA, potentially generating damage which could either lead to cancer or lead to genetic problems which could be passed on to future generations.
Although I can't quantify the risk associated with the latter phenomena, knowing that every time I see a little flash I have suffered a small but permanent loss of vision would make space travel less appealing.
The problem with going at solar minimum is that more galactic cosmic rays make it inward to the inner solar system, increasing radiation dose. The problem with going at solar maximum is occasional sudden death from energetic proton streams. Solar flares cause three main hazards: gamma rays from the flare itself (a problem but not a lethal one for most events); energetic protons that are accelerated by the flare and any post-flare coronal mass ejection; and bulk clouds of material that are thrown off by the Sun and that entrain magnetic fields.
The energetic protons are a real problem for man and machine. They arrive minutes to hours after the flare itself is seen. They have a high "quality factor", meaning they do a lot more biological damage than an equivalent ionizing dose of X-rays or gamma rays; and they tend to embed themselves in insulators, developing a humongous static charge that screws with electronic circuits and can burn out components. The clouds are more of a problem for planet-sized bodies (like the Earth) than for astronauts, but they do have some potential health consequences. They travel at "only" 1-4 million miles per hour, arriving at Earth about 1-4 days after the solar event.
Over the last three years we've had six or seven large flares that could have caused radiation sickness or death for Apollo astronauts (or Mars-bound astronauts with similar amounts of shielding to a mere Apollo capsule). That's enough that you'd have to expect at least one such event during a Hohmann transfer orbit to Mars, if you travelled at this phase of the solar cycle (declining).
The space station is largely shielded from the energetic protons, because it stays in low Earth orbit, underneath the Van Allen radiation belts -- Earth's magnetosphere diverts the protons away from the station. But the high energy galactic cosmic rays have no trouble passing through and hitting the station. So station astronauts are (probably somewhat) safer during solar maximum, but interplanetary astronauts are (probably) safer during solar minimum. Either way the radiation dose is a problem that has to be designed around.
Incidentally, the largest effect of solar activity on the space station is orbital decay! During solar maximum, the increased far-ultraviolet brightness of the Sun heats the outer layers of the atmosphere (the "thermosphere"), making them expand significantly -- that increases orbital drag a LOT. It's one reason (the other being delays in the Shuttle program) that Skylab re-entered the atmosphere before the Shuttle came on-line to provide additional boost. Skylab was launched during solar minimum in the mid 1970s, and the orbital decay projections were based on solar minimum conditions. It re-entered several years earlier than initially expected, because the atmosphere (and hence orbital drag) got larger in the solar maximum period of the late 1970s. The space station has similar orbital-decay issues; if you Google for the altitude-versus-time plots, you'll see that at its chosen altitude, the ISS needs to be boosted every six months or so, or it will spiral in and re-enter the atmosphere.