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Space Science

Solar Flares Shield Astronauts from Cosmic Rays 135

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?"
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Solar Flares Shield Astronauts from Cosmic Rays

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  • Shields up (Score:5, Interesting)

    by cy_a253 ( 713262 ) on Wednesday October 12, 2005 @08:37PM (#13778168)
    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?
    • Re:Shields up (Score:2, Interesting)

      by Anonymous Coward
      A better shield would be composed of something that is rich in hydrogen, as high velocity charges particles like those in cosmic rays will lose their energy as they intereact with the protons in the hydrogen atoms.

      Eventually, when we get to the point where we're building ships in orbit (where mass will be less of an issue than it is when you're launching it all up from Earth), you'd likey be building a vehicle out of more durable materials (mmm, cermets), with a good layer of the previously mentioned hydrog
      • with a good layer of the previously mentioned hydrogen rich material, most likely a plastic of some sort.

        How about water? It's going to be important for other reasons anyway.

      • Why Hydrogen? Cosmic particles interact just as much with collections of protons and neutrons as with single protons. In fact, your best bet for shielding, if you're going for the "let's maximize the interaction potential of the material" (also known as the "cross-section" in physics) would be to use something like lead.

        Funnily enough, that's what we already use to shield ourselves from radiation, both particle (alpha, beta) and light (gamma)!

        • In fact, your best bet for shielding, if you're going for the "let's maximize the interaction potential of the material" (also known as the "cross-section" in physics) would be to use something like lead.

          Lead is used because of its density, not its effectiveness. Other than hydrogen, basically all elements cause charged particles to lose ~ 2 MeV/cm per g/cm^3 of material present. For hydrogen it's ~ 4. Gamma ray interactions are similar as well.

          Of course, the problem with hydrogen is the fact that it'd take
    • 1/r^2 kills this (Score:5, Insightful)

      by G4from128k ( 686170 ) on Wednesday October 12, 2005 @09:11PM (#13778360)
      The Sun's magnetic field [] may be very weak (about 5 Gauss at the surface, about 0.00005 Gauss in solar wind), but it's very big. Creating a field with a compact object (say 100 meters in diameter -- quite a large space craft!) that creates a 0.00005 Gauss field at a distance of 160 million kilometers would require a field strength on the order of about 1.28 x 10^18 Gauss. This is NOT compatible with living things. Fields stronger than 100,000 Gauss can levitate living things []. I suspect that the needed deflector field would strip the electrons off the spacecraft's atoms (even a 200,000 gauss magnets have a tendency to explode).

      Even if I'm off by many orders of magnitude (IANAP), the required field strength will be unattainably high.

      • Re:1/r^2 kills this (Score:5, Interesting)

        by mattjb0010 ( 724744 ) on Wednesday October 12, 2005 @09:37PM (#13778485) Homepage
        Fields stronger than 100,000 Gauss can levitate living things.

        I've stuck the movie of the levitating frog up here []
        • I can't help but wonder just what kind of super-psychidelic-freak-out that frog must be having. First off, it is experiencing weightlessness, a phenomenon so outside of its natural environment that that alone must be super-freaky for it, especially without the ability to comprehend how or why it is happening like humans can. Second, it is immersed in a super strong 20 Tesla magnetic field and it's bouncing around in there like crazy, the resultant electric currents induced in the neurons of its brain must b
        • any video of the exploding magnets??? :D
      • Re:1/r^2 kills this (Score:5, Informative)

        by barawn ( 25691 ) on Wednesday October 12, 2005 @10:17PM (#13778684) Homepage

        The fact that the Sun's magnetic field is large isn't what protects us from cosmic rays. The Sun's magnetic field encourages particles to orbit the Sun. That doesn't help us. What helps is when a dipole field gets closer to you - like when the Sun sloughs off a bunch of plasma that drifts near you. Hence a Forbush decrease. What protects us on Earth is the Earth's magnetic field, and the atmosphere.

        Anyway, it's relatively easy to craft magnetic fields to any shape you want. So high magnetic field on the outside, zero magnetic field on the inside. We're really good at that. And 5 tesla (50,000 gauss) should be about enough []. It has been studied.

        The reason it's not ideal is because cosmic rays aren't all charged. Gamma rays make up a component of solar cosmic rays, and okay, there may (should) be a few neutrons from the Sun as well (though that part is really new and not well studied).

        But magnetic shielding is very actively being looked at. It's just not an easy problem - we don't have very much experience with superconducting magnets in space, for instance.

        Interestingly, one of the best things about this is that you don't really have to worry about the highest energy particles which will get through. Not only is the flux far, far lower, but they deposit less energy than lower energy particles which stop in your body. So it's pretty easy to figure out how high a magnetic field you need.

        And smartass comment: magnetic fields don't drop like 1/r^2. Electric fields do. For a simple magnetic dipole, the field strength drops like 1/r^3. Different configurations drop differently, as well.
        • If I could transfer my mod points from my post to yours, I would. Thanks for the info.
        • "The reason it's not ideal is because cosmic rays aren't all charged. Gamma rays make up a component of solar cosmic rays, and okay, there may (should) be a few neutrons from the Sun as well (though that part is really new and not well studied)."

          That doesn't sound quite right. Why would free neutrons (half life 15 minutes) be an issue coming from the sun? Besides, fusion does not occur to any appreciable degree in the corona, it only occurs deep within the inside of the sun, neutrons produced this way would
          • a half life of 15 minutes means just that, half of them will decay in the first 15 minutes. Half of what is left will decay in the next 15 minutes. The sun is 8 light minutes away from us, If the neutrons go at a speed of about c/2 then half will get here. An hour after departure there will be 1/16th of the neutrons left. The inverse square law also applies as they will be getting more spread out radially. Assuming constant speed, combining the halflife decay and the inverse square I think the decay is prop
            • Re:1/r^2 kills this (Score:2, Interesting)

              by Anonymous Coward
              Relativistic effects also alter the apparent half-life of free neutrons. Neutrons traveling at relativistic speeds will have significantly longer lives relative to us. Particle accelerators rely on this effect to work with short-lived particles.
            • and what would mechanism would accelerate neutrons to 100's of MeV energies (below which they are not relativistic) from the sun?
              • Fragmentation of accelerated heavy nuclei, or proton-proton collisions. You can't easily accelerate neutrons, but you can create or free them at high energies.
          • That doesn't sound quite right. Why would free neutrons (half life 15 minutes) be an issue coming from the sun?

            Sun's only about 8 light-minutes away, so even a moderate-energy neutron - say, 1 GeV - is going to reach us well before it decays. (*) A higher-energy neutron - say, tens of GeV - with a time dilation of about a factor of 10 - won't have decayed appreciably at all before it reaches us.

            This is of course akin to atmospheric muons - with a lifetime of 2.2 microseconds, they shouldn't reach the surfac
      • Hm... 100 000 Gauss is only 10 tesla. We stick rats in that all the time (no floating). The floating requires a strong field gradient, but not really that strong a field. The 17T (170 000 Gauss) MR spectrometers that most university chem departments have don't seem to explode that often. Or DO they? I'll have to sneak up behind a chemist and yell BOOM and see how high he jumps!

        1.28x 10^18 Gauss is a little over the top though. But why so much? You don't need to create a field 160 million kms away, y
    • Re:Shields up (Score:4, Interesting)

      by shokk ( 187512 ) <> on Wednesday October 12, 2005 @09:32PM (#13778459) Homepage Journal
      You mean like a hot hydrogen plasma confined in a toroid shaped magnetic field similar to what they use for fusion research? Maybe it doesn't need to be quite that hot to protect the astronauts, but keeping it moving around the outside of the craft may produce the same benefit.
    • There has been some discussion on this already from the 50's. I asume creating a magnetic field is somewhat simulare to creating a charged( i guess charged is redundant) ion field. I have seen drawings of what it might look like but fail to find references to them at the moment. The references i have seen were based on the moon but apear as they should be capable of working on a ship or space station.

      Here []is a site explaining somethign simular to what i have read. Maybe i'm think of two different things. May
  • let's not forget what it did for jean grey...
  • Not very pratical for commuting ...
  • by aussie_a ( 778472 ) on Wednesday October 12, 2005 @08:41PM (#13778193) Journal
    If I'm understanding this right, the magnetic properties of the solar flare cause the decrease in CME's? If so, couldn't ships magnetize their hull to shield the people inside? It obviously won't stop all the CME's, but it will decrease it.

    Might turn out Enterprise's "ionize the hull" isn't as much sci-fi nonesense as it first sounds.
  • by ScottSCY ( 798415 ) on Wednesday October 12, 2005 @08:42PM (#13778199)
    "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.
  • by Bananatree3 ( 872975 ) * on Wednesday October 12, 2005 @08:46PM (#13778229)
    "So, I guess it would be safer to plan a manned Mars mission to coincide with peak sunspot activity?"

    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.

    • by saskboy ( 600063 ) on Wednesday October 12, 2005 @09:07PM (#13778334) Homepage Journal
      You're correct. The submitter didn't realize that cosmic radiation and solar radiation are not the same thing, since solar radiation is the stuff that comes from our sun, and cosmic radiation comes from sources outside of our solar system like other stars, black holes, pulsars, nova, and other big bad radiation machines out there.

      There may be a decrease in radiation coming from elsewhere, but the ship would still be hammered by high speed Coronal Mass Ejection particles. Radiation sheilding is essential; Bring your polyethylene, in other words.
      • Actually, the submitter understands this perfectly. In the first place, the comment was a joke. In the second place, if you read the article, you would see that they mention we can shield against excess solar radiation far easier than cosmic rays, so the joke is half serious. So there...phttttttt!
        • I see. I should have remembered the "joke appears in the last line of article" rule, on Slashdot. Unfortunately, some people would read it and think you were being completely serious. I guess only time and experience will tell if constant cosmic radiation is a greater threat to human health than sporadic solar radiation.
    • An excellent point, and one that probably will mean that it is, in fact, safer to try and avoid spaceflight during high solar activity (when possible). On the other hand, the danger is only there if the CME is directed in your general vicinity. Sure, the Earth gets hit with a solar flare (or its remnants, actually) from time to time, but it does not get hit with every solar flare the Sun produces.
    • Coronal mass ejections send huge numbers of high energy protons into space. These are far more easily shielded by standard spacecraft construction techniques than cosmic/gamma rays. No contest between which scenario is more dangerous. The main danger during CMEs is to EVA (spacewalks), since the pressure suits are not easily shielded to a sufficient degree.
  • So how about I use the cheap solar energy to run a Van de Graff generator and put about 167TeV into a metal shell around my ship?
  • by Pottsynz ( 756353 ) on Wednesday October 12, 2005 @08:47PM (#13778240) Journal
    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.
  • by uncoveror ( 570620 ) on Wednesday October 12, 2005 @08:49PM (#13778255) Homepage
    Solar flares may protect astronouts from cosmic rays, but will provide no defense against death rays [] or destructo-rays! []
  • why not plan a trip to the sun, she be nice and safe there....
  • NASA source (Score:4, Informative)

    by saskboy ( 600063 ) on Wednesday October 12, 2005 @09:00PM (#13778306) Homepage Journal
    NASA Science News for October 7, 2005

    Another source:

    Strange, but true: Solar flares can be good for astronauts. []

    • Re:NASA source (Score:3, Interesting)

      by Jeff DeMaagd ( 2015 )
      True, sadly, Slashdot is reposting yubanet's repost of NASA's story of last week. Even worse, Slashdot will repost this story within 24 hours.
      • If you want to continuously refresh hundreds of sites to get your news quicker, then you'll get your news quicker. Or hey, you could watch the news or listen to the radio. Most of us, yourself included, come here for the conversation.
  • I knew there must have been a flaw in the Fantistic 4 movie. This is it!
  • Nothing is more Airwolf than Airwolf! Cheers!
  • Except that... (Score:2, Interesting)

    by Anonymous Coward
    The reason for this decrease in galactic cosmic rays is that the solar flares and coronal mass ejections themselves emit relativistic electrons and solar cosmic rays (mostly protons) which are responsible for pushing the galactic particles back. The number of solar energetic particles emitted during flares is much larger than the galactic source. In addition to the energetic particles, the sun also emits copious amount of hard and soft X-rays during solar flares.

    I don't think that it matters much to an astr
    • The ISS is in Low Earth Orbit, deep inside the Earth's magnetic field. Solar flares dump huge amounts of energy into the Earth's magnetic field. The more engergy, the further south the Aurora Borealis appears, as the magnetic field pulls particles from the solar wind to larger circles further away from the poles. The temporary increase in the strength of the Earth's magnetic field protects astronauts in the ISS; astronauts on their way to Mars, unprotected by the Earth's magnetic field, would have both t

      • Re:Except that... (Score:2, Interesting)

        by Anonymous Coward
        "Solar flares dump huge amounts of energy into the Earth's magnetic field. The more engergy, the further south the Aurora Borealis appears, as the magnetic field pulls particles from the solar wind to larger circles further away from the poles."

        Not exactly. What happens is that with the increased solar wind pressure the magnetosphere becomes distorted, the auroral oval expands equatorwards, and electric currents start flowing. "Magnetic reconnection" events in the magnetotail energize magnetospheric (not so
  • Isn't this the same phenomena that cost Gore the election in 2000? - ME -
  • It's a tough job shielding those astronaughts between my attempts to destroy the worlds electronics.
  • Not saying the bone loss problem can't be solved, but ever since hearing about the bone loss problem I've felt that radiation would be easier to solve than bone loss.

    A simplistic source, ( []) has this easy to digest quote
    "... And because the gravity on Mars is only 38% of Earth's, ways to counteract any damaging effects of the weak gravity on their bodies, such as progressive bone loss and muscle atrophy, will have to be found. Currently, there is no fully effectiv
    • Actually, what happens if all three are used in tandem?

      Use magnetic fields to shield the ship from plasma by funneling it into a reactor rather than repelling it.

      The solar flare blocks radiation, fuels the ship, and could potentially provide enough fuel to solve the bone mass issue.

      The bone mass issue is caused by being in zero G, but if you're constantly under acceleration, you don't suffer from being in zero G. You also go places much faster than if you allow yourself to travel in free fall.

      Accelerate th
    • I say we breed martians on our martian colony and let evolution take its course, really. Hmm, we'd have green midgets, right? Well maybe not green.
    • From the abstract (the full paper doesn't seem to be online) he's assuming the bone loss on Mars will be the same as it is in zero-G. There is, however, AFAIK currently zero experimental data to support that assumption.
      There are any number of possible models for bone loss on partial gravity. It might be that there's no accelerated bone loss at all once gravity is above some minimum value. It might be a linear relationship. Or something more complex again.

      The MarsGravity biosatellite [] will hopefully provid

      • Actually, speaking of the MarsGravity biosatellite, I have an odd question.

        Why don't they just develop the little spinny thing to hold and feed the mice and send it up on the next Progress Drone to the ISS? Why are they developing their own satellite with it's own life-support system when we have a perfectly good space station that has a life-support system, as well as a couple of guys to monitor the experiment and the mice and potentially fix anything that goes wrong.

        And rather than developing the heat sh
        • I agree that on the surface it sounds like a good idea, but I think the problem is that you need a certain radius of the rotation or the rotation rate will be so high as to make the mice permanently seasick from the Coriolis forces. That tends to rule out conducting it within the interior of the ISS.
          • Well, arguably, mice would need a smaller radius of rotation because they're smaller and closer to the ground than humans. Of course, one of the intriguing concepts is that--with human beings on hand--I'm sure you could adjust this. Start with a 6-inch radius. "Nope, the mice are tossin' their cookies." How about a foot? "Less cookie tossin'--we're on the right track." :^)

            Heck, even if it goes outside ISS, I imagine there's some way to get oxygen and power out there for experiments. I know they can do
            • After I posted the above reply, I was reading somewhere on the MarsGravity site (too lazy, Google it yourself) that NASA actually had such a lab to go on the ISS, but it's going to get canned because of the well-known difficulties facing that station. An editorial in the New York Times caned them for doing so, wondering how the heck they were planning to do long-term stays on the moon without collecting data on what low-G does to the body.
  • by Dr. Zowie ( 109983 ) <(slashdot) (at) (> on Wednesday October 12, 2005 @11:18PM (#13778955)
    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.
  • Either way, seems like a horrible way to "DIE". It's like getting lethal injection but 1 million watt electricity rid of 30% of the lethal chemical in your body.

    hmm.. did I just invented a new way to execute people?
  • Without properly tuned shields the astronauts may turn to stone, or become invisible, or get really stretchy, or turn into fireballs.
  • So, I guess it would be safer to plan a manned Mars mission to coincide with peak sunspot activity?

    Peak sunspot activity means peak coronal mass ejection (solar flare) activity. A really large solar flare can inflict thousands of rems in a short period of time, while you'd be reducing cosmic ray exposure by tenths of a rem per week. Even smaller flares will influct tens or hundreds, and at any reasonable interplanetary speed, you'll get hit by several during a sunspot peak.

    If you've got the Van Allen belt
  • Don't Forget To Pack Your SPF 1,000,000 !
  • by Scott7477 ( 785439 ) on Friday October 14, 2005 @02:58AM (#13788599) Homepage Journal
    The Association of Space Explorers is holding their 19th Planetary Congress here in Salt Lake City this week. The theme of the conference is "Our Destiny in Space: Worlds without Borders". I took my son downtown and we got to meet Don Lind, one of the space shuttle astronauts. I thought it was pretty awesome. Thanks, Don. I'm curious to know how many folks have actually met an astronaut...

    Some of the things they are talking about(from the official program):

    The Genesis of Cooperation in Space: The Apollo-Soyuz Program
    Tom Stafford

    Panel Discussion (ASE Founders)
    Loren Acton, Bertalan Farkas, Georgi Ivanov, Alexei Leonov, Vladimir Lyakhov, Dorin Prunariu, Rusty Schweickart, Vitaly Sevastyonov

    Technical Session: International Space Programs Review
    Chairs: Chris Hadfield, Leroy Chiao

            NASA Headquarters Update: The ISS Program and Future Issues
            Bill Readdy, NASA

            Life on Station
            Leroy Chiao, NASA

            Report on the Canadian Space Program
            Chris Hadfield, CSA

            Report on the Russian Space Program
            Yuri Usachev, RSC Energia

    Technical Session: Crew Safety & Technical Issues
    Chairs: Sergei Avdeev, Charlie Precourt

            Shuttle Derived Vehicles
            Mike Conn, ATK Thiokol

            Maintaining On-Orbit Crew Proficiency
            Chris Hadfield, CSA

            Electromagnetic Radiation and Crew Health
            Alexander Serebrov

    Technical Session: Future Programs
    Chairs: Michel Tognini, Yuri Usachev

            Beyond the Moon: The Asteroid Option
            Tom Jones

            Yuri Usachev, RSC Energia

            Russia's Future in Space
            Georgi Grechko

            The Aurora Program
            Piero Messina, ESA

    There's some pretty big names in there, also note that they are talking about astronaut safety with regard to electromagnetic radiation.

    I submitted this to /. and got rejected, so take that, CmdrTaco!

If you suspect a man, don't employ him.