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Cosmic Rays Could Kill Astronauts Visiting Mars
jvchamary writes "Given the recent stream of reports of 10th planets and the relative success of the NASA Discovery mission, it might again be time to get excited at the prospect of visiting the Red Planet. Unfortunately, New Scientist reports that Astronauts traveling to Mars would be exposed to so much cosmic radiation that 10% would die of cancer."
Not only is it cancer, it's space cancer. That's gotta be like 10 times worse ;)
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Also, 25% will become stretchy, 25% will turn invisible, 25% will burst into flames, and 25% will have their skin replaced by an orangey rock-like substance!
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So how would this be a limiting factor for a government that still subsidizes tobacco farmers? What if we only sent smokers? TFA article says that 10% would get fatal cancer sometime in their lives. Really, how is this different from those who self select themselves for a much increased risk of cancer through smoking?
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We've known this for quite a while.
I think they'd also have to go through the Van Allen radiation belts which could also be a concern. Conspiracy theorists have argued that space travel to the moon was impossible because the Van Allen radiation would kill or incapacitate an astronaut who made the trip. In practice, even at the peak of the belts, one could live for several months without receiving a lethal dose.
Apollo had timed things however to make it accross while radiation was at a minimum. However, if they'd be on such a long trip -- timing will have to be a lot more precise.
Short of hauling up lead plates, I don't know what they'll do.
I'd be willing to take a 10% risk of cancer later in my life in order to see mars. Hell i'd take a 10% chance of not surviving the trip home.
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2.2 Sieverts is 220 rems. that's like 8-10 times previous estimates. And you've got to wonder about quotes like this:
Others suggest more radical solutions might be needed. "Radiation exposure is certainly one of the major problems facing future interplanetary space travellers," says Murdoch Baxter, founding editor of the Journal of Environmental Radioactivity. "Unless we can develop instantaneous time and space transfer technologies like Dr Who's TARDIS."
Wasn't mini-magnetospheric plasma propulsion supposed to offer robust shielding, in addition to efficient travel?
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Let's never leave our little shielded planet because we might get cancer!
Seriously, I'm sure that there are thousands of people who would line up, despite that 10% chance of a disease that some of them will get anyway. I would.
Go to Mars, keep working on cancer cure. Everybody wins.:-)
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So even if they cannot solve the cosmic radiation problem entirely, there is a possibility that could get them safely to Mars and back. Of course first we'd need that Moon base I've been reading about in SF stories written as far back as forever...
Space is dangerous?!? Wha??!!! Wow.. We better not go there then! RUN AWAY! Someone might die! *gasp* *shock* Horror!!!!!!1111one!
I think any first travelers to Mars would have far more impressive ways to die than a 10% chance of radiation damage. The ship could explode, they could run out of food, they could hit any of the various bits of rock out there, they could get abducted by the aliens that live on the other side of the moon, they could slip and fall while getting out the shower cracking their skulls open, etc.
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Seriously, though, does anyone know just how much material is needed to block these rays? Specifically, if a space habitat were constructed (along the lines of an O'Neill cylinder, for instance), how many meters of rock would we require on the outer surface to make the place long-term habitable?
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If they're talking about current chemical propulsion technologies, then yes, they'll be out there for the better part of a year. If we get dig out nuclear propulsion technology that's already been developed, such as NERVA, and other things such as gas core nuclear rockets, it's simple to cut the trip down to weeks while simultaneously packing dozens of tons of extra shielding.
Firstly, we need nuclear power. Kind of a "fight fire with fire" approach.
For mars habitation, build a base underground?
For the journey, build the spacecraft out of very, very thick material? Not some exotic material, just a thick layer of rock would suffice, yes?
use our nuclear generators to create a massive magnetic field around the spacecraft.
It must be possible to overcome these problems. After all, we are traveling on a spaceship right now, and it's doing a pretty good job of shielding us from radiation.
You have a 33% chance of contracting cancer at some point in your life, assuming you live an "average", complete, life. Let's ballpark an estimate 40% average survival rate for cancer (a good deal of them are treatable if detected in time) and we get 13.2%
Send me up there.
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Astronauts traveling to Mars would be exposed to so much radiation that 10% would die of cancer.
For once I'm glad I have a tinfoil hat!
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Basically, yeah - we have several miles of comparatively dense atmosphere (or the entire bulk of the earth) protecting us from cosmic rays. Future Mars astronauts will pretty much have a few layers of tinfoil.
Still, it is possible to design ships which will shield passengers from the worst of the rays, but these tend to be prohibitively heavy (= prohibitive amounts of fuel) because of all the additional shielding.
The best alternative I've seen yet were plans to build a ship where all the water and other supplies were stored around the outsides of the ship, and the actual crew living compartment was a small space right in the middle - this uses water and fuel (the bulkiest of the supplies) as additional shielding, but it still carries a much elevated risk of irradiation and/or cancer than staying put on earth.
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No, lead is insufficient. They'll need something heavier, like Urani... oh.
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I know you're joking, but I think a number of slashdot readers are thinking, "yeah, why can't they just shield them".
I'm not sure I see the point of even going to Mars in the first place; like Kennedy's moon trip, going to Mars will get us nothing. Things are just too impractical to get anything useful done on either planet. The futurists all argue, "well, SOME day it'll be practical". Wasn't this the same group that predicted we'd have, ten years ago, flying cars, transporters, faster than light travel, etc?
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Permanent settlers, while having a significanly shorter life expectancy, would also undergo slightly excelerated evolution :)
Seriously though, what about the first europeans to the Americas. They were at least as likely to dye from malnutrition during the trip, not to mention all the hardships they faced when they got there. That is what it means to be a pioneer - to take risks and pave the way so others after you can go more safely.
Again, I'm reminded of stories of voyages of discovery from 200 years ago. The crew sailing with Captain James Cook actually fared better than most, according to Wikipedia:
At that point in the voyage, Cook had lost no men to scurvy, a remarkable and unheard-of achievement in 18th century sea-faring. He forced his men to eat such foods as citrus fruits and sauerkraut -- under punishment of flogging if they did not comply -- although no one yet understood why these foods prevented scurvy. Unfortunately, he sailed on for Batavia, the capital of the Dutch East Indies, to put in for repairs. Batavia was known for its outbreaks of malaria, and, before they returned home in 1771, many in Cook's crew would succumb to the disease, including the Tahitian Tupaia, Banks's secretary Herman Spöring, astronomer Charles Green, and the illustrator Sydney Parkinson.
Would it be that much worse to be afflicted with cancer in the 2000's than with malaria in the 1700s? At least we have morphine now.
The suggestion that brain ailments might afflict spacefaring explorers strikes a familiar chord as well:
Cook returned to Hawaii in 1779. On February 14 at Kealakekua Bay, some Hawaiians stole one of Cook's small boats. Normally, as thefts were quite common in Tahiti and the other islands, he would have taken hostages until the stolen articles were returned. However, his stomach ailment and increasingly irrational behaviour led to an altercation with a large crowd of Hawaiians gathered on the beach. In the ensuing skirmish, shots were fired at the Hawaiians and Cook was speared to death.
Another factor to keep in mind is the motivation of the sailors. For one thing, conditions at home didn't offer much better chance at longevity. But perhaps more importantly, Captain Cook believed in the medicinal value of large quantities of beer:
The custom of allowing British seamen the regular use of fermented liquor is an old one. Ale was a standard article of the sea ration as early as the fourteenth century. By the late eighteenth century, beer was considered to be at once a food (a staple beverage and essential part of the sea diet), a luxury (helping to ameliorate the hardship and irregularity of sea life) and a medicine (conducive to health at sea).
It sounds like we won't be exploring Mars until we have a population of would-be explorers that is 1) worse off here than in space, 2) led by a captain with a penchant for the lash, and 3) drunk off their arse.
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Basically this study is saying that with our current technology, it would be difficult to go to Mars or anywhere beyond. That itself wouldn't be so bad if the tone of the article made it sound impossible to do at all.
With 1960 technology it wouldn't have been possible to go to the moon. But with 1969 technology, it sure was. In 2005, we might lack radiation shielding that makes interplanetary distances hard to traverse without killing you 50 years from now. But in 2015, it might very well be easy to have lightweight material shield you adequately.
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Just call it "whole body radiation therapy."
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I don't want to get into a particle vs wave debate, but at the energy level of gamma rays (photon-like particles), I don't think you have to worry about changing their momentum much so they "bounce" with a some weak lead shielding resulting in a ping-pong game...
If the gamma photon gets through the lead (and it usually's got lot of momentum/energy), it'll get to the person and have some probablity of hitting one of the atoms in the person (resulting in the atom decaying and causing ionizing radiation damage). Since a person is usually thicker than the shield, the probability of hitting an atom in the person's body is much higher than hitting an atom in the lead shield. For alpha and beta radiation, they are charged and also usually have lower energy/momentum and as you mentioned can be mostly stopped with thin layers of material...
And cosmic rays (which mostly originate outside the solar system, but some come from the sun) are about 10-1000x more energetic than typical gamma rays (since both cosmic and gamma rays are techically photons they are only distinguished by energy level anyhow, a rose is a rose).
As for slowing down these highly energetic photons, well, there's not much a lead plate in a space-suit (or in a space-ship) is gonna do about that. Particles with that much energy/momentum aren't easy to stop with a few inches of any material, but if a "peice of radiation decided to stop", the photon would have zero rest mass and you wouldn't notice it (except for the residual path of damage it made in the attempt to stop)...
For current astronauts "near" earth, they of course have this big shield that protects us from about 1/2 of this radiation (the technical name of the shield is called earth), for someone far away from a big planetary body to shield them, they'll get at least a double dose of cosmic rays. For those of us on earth we get protection from both the earth on one side and atmosphere on the other, but of course mars's atmosphere is thinner (and doesn't have any ozone, although there may be some other thing there that helps)...
Another solution to the cancer risk is to send older astronauts. The older you get, the lower the risk that a cancer is going to significantly shorten your life. That is why the treatment for slow growing prostate cancers is often to do nothing. Someone in their 50s, in good shape, would be up to the rigors, but not going to (or at least shouldn't) feel cheated when cancer strikes 15 years later.
The situation is a lot more complicated than that. High atomic mass elements are great at causing collisions with the particles composing the radiation that you're trying to shield against. However, a direct collision isn't always the best thing.
Case and point: The best way to shield against solar radiation is high atomic mass materials. Even moderate materials, such as aluminum, should work quite well if you plate it on thick enough.
But what happens when GCR (Galactic Cosmic Radiation) strikes that shielding? You often get bremsstrahlung ("braking radiation") - the single particle is instead replaced with a shower of much more dangerous particles. Even worse, these particles are released partway or even all the way through the shielding.
The best way to shield against GCR is hydrogen in huge quantities to decelerate the particles - this generally means either your fuel or plastics in the skin. But that doesn't shield well against solar radiation. In short, what you end up needing is a complex layered system. The exact design? That's still a wide-open question. We know we can pack enough aluminium to stop solar-radiation-only (including a small shelter for storms) without having too heavy shielding requirements. Factor in bremsstrahlung, however, and it's a wide-open question.
By the way, to those who suggest "active shielding" (creating a magnetic field around the craft to deflect radiation) - studies show that it won't work to stop GCR (only solar).
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Let them breed. The 90% that survives are obviously more cancer-resistant than the others. In a few generations, cancer rates will be at acceptable levels.
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Could someone please explain to me what astronauts are doing with anvils in space? Perhaps they're using them to hammer out tools to gouge out shuttle tile filler strips?
"It felt almost as good as stealing cars from grandma." -- Margaret Thatcher, probably.
Seriously, this is one of the same arguements from those who don't believe we ever visited the moon: The cosmic rays would kill you.
It's an interesting theory, but also one which must be answered before long term/distance space travel will be possible. Or even short term travel, if the conspiracy theorists are to be believed.
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If only humans worked that way. The biggest leaps forward in technology have been due to catalysts of some sort. Be it war, arms races, space races... oh, and porn ;)
The problem is, of course, that it's not just the scientists that have to be on board, but the funding as well. Funding only comes when there is a serious problem that enough people want to address.
How exactly do you plan to get all the legislators, corporations, and stockholders to all agree to this massive R&D effort?
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The easy solution would be to take some digging and tunneling equipment then use that to create an underground Mars station....thus using the billions of tons of existing rock & dirt to sheild you. You could also take melting aparatus and make an under-ice cave in the new lake.
You often get bremsstrahlung ("braking radiation") - the single particle is instead replaced with a shower of much more dangerous particles. Most galactic cosmic rays have energies between 100 MeV (corresponding to a velocity for protons of 43% of the speed of light) and 10 GeV (corresponding to 99.6% of the speed of light). The number of cosmic rays with energies beyond 1 GeV decreases by about a factor of 50 for every factor of 10 increase in energy. Over a wide energy range the number of particles per m2 per steradian per second with energy greater than E (measured in GeV) is given approximately by N(>E) = k(E + 1)-a, where k ~ 5000 per m2 per steradian per second and a ~1.6. The highest energy cosmic rays measured to date have had more than 1020 eV, equivalent to the kinetic energy of a baseball traveling at approximately 100 mph! (So should shielding be wood? ;))
Note that 100MeV is about 30X Gamma Ray Energy so even with the loss of energy in the collision (it's not 100% transfer of energy) with the shielding there is a lot of energy left over to cause havoc in the material used as the shielding.
Dunno how dangerous "ionized" water is - certainly not as dangerous as letting the radiation hit the water in your body, and I believe that there are standard techniques for creating "deionized" water or bleeding off the extra charge from arriving beta particles.
:-)
As far as radiation goes, I believe you are talking about the radioactive particles from space that are left in the water after they have been slowed down, or perhaps the creation of deuterium & tritium from high-energy collisions? Again, I believe that the results are pretty low level - hydrogen & oxygen don't exactly fission into radioactive particles easily (unlike stuff like uranium).
I think the primary byproduct of the captured particles from space will probably be alpha (bare helium nuclei) and beta (high-energy electronics) particles, so you could probably harvest the resultant accumulated helium gas over time.
As far as gamma rays are concerned, I don't think they can fission hydrogen & oxygen atoms (unless you're talking energy levels high enough to reduce basic particles to quarks, in which case your spaceship/spacestation has bigger problems), so a thick enough wall of water with an inner wall of lead or something similarly dense should be enough to protect against almost anything. (I guess it would be a bad idea to have your water in direct contact with lead
Of course, there's always the possibility of a neutrino blast (like when a star goes nova or supernova), but we don't really have any way of defending against that whether we are in a spaceship/station or on a planet.
One thing this and most other articles fail to mention is that radiation exposure on the Martian surface is about 75% of that in space. The thin Martian atmosphere offers little protection, and when particles get through and strike atoms in the soil they create a scatter of secondary radiation, some of which scatters upward.
One of NASA's Design Reference Missions to Mars involves a total mission duration of 900 days with a 500 day stay on the surface. This mission would expose the crew to more than their allowable lifetime radiation dosage. Another mission profile involves a 435-day duration. Both of these missions involve a year's round trip travel time, and virtually doom the crew to early cancer deaths after their return to Earth.
Gaseous Core Nuclear Rockets would make Mars missions truly feasible. For reasons discussed in detail here, here and here, among other places, GCNR rockets would get a mission to Mars and back in 270 days, with 7 months travel time and 60 days on the surface. Additionally, the GCNR rocket would have huge carrying capacity, enough for the craft to carry a foot-thick water shield in a double hull. Such a ship would reduce the crew's total radiation exposure to about 1/5 of the 435-day mission and 1/10th of the 900 day mission. The water layer would also act as a giant passive heat sink, eliminating the need for a complex refrigeration system. It would also be a self-sealing micrometeorite shield -- the outer few inches of water would freeze, and if a micrometeorite punctured the hull the escaping water would refreeze over the hole immediately.