By Andrew Nusca
Posting in Aerospace
A panel recently concluded that NASA should consider flying to one of Mars' moons, rather than the planet itself. But the suggestion is still dangerous.
A committee tasked by the White House with reviewing NASA's plans for human space flight suggested that Mars is "the ultimate destination for human exploration; but it is not the best first destination" and suggested that sending astronauts to one of Mars's moons, Phobos or Deimos, may be a better idea.
From there, astronauts could use remote-controlled robots to explore the Martian surface and retrieve samples for study.
But the suggestion is still dangerous, according to the New Scientist.
Why? Because the galactic radiation that barrels through the solar system poses a significant health risk.
The radiation, which is made up of protons, gamma rays and cosmic rays, can slice through DNA molecules when it passes through living cells. The resulting damage can make cells behave erratically and lead to cancer.
NASA outlined the problem itself way back in 2004:
NASA weighs radiation danger in units of cancer risk. A healthy 40-year-old non-smoking American male stands a (whopping) 20% chance of eventually dying from cancer. That's if he stays on Earth. If he travels to Mars, the risk goes up.
The question is, how much?
"We're not sure," says Cucinotta. According to a 2001 study of people exposed to large doses of radiation--e.g., Hiroshima atomic bomb survivors and, ironically, cancer patients who have undergone radiation therapy--the added risk of a 1000-day Mars mission lies somewhere between 1% and 19%. "The most likely answer is 3.4%," says Cucinotta, "but the error bars are wide."
The odds are even worse for women, he adds. "Because of breasts and ovaries, the risk to female astronauts is nearly double the risk to males."
Researchers who did the study assumed the Mars-ship would be built "mostly of aluminum, like an old Apollo command module," says Cucinotta. The spaceship's skin would absorb about half the radiation hitting it.
"If the extra risk is only a few percent… we're OK. We could build a spaceship using aluminum and head for Mars." (Aluminum is a favorite material for spaceship construction, because it's lightweight, strong, and familiar to engineers from long decades of use in the aerospace industry.)
"But if it's 19%… our 40something astronaut would face a 20% + 19% = 39% chance of developing life-ending cancer after he returns to Earth. That's not acceptable."
Here on Earth, people are protected by the planet's atmosphere and magnetic field. That's also the case for astronauts in the low-Earth orbit International Space Station.
But for a Mars mission, it would take impractically thick and heavy aluminum shields to stop high-energy galactic cosmic rays. And alternative technologies -- such as a plasma radiation shield -- are still not fully developed.
NASA's existing rules stipulate that each astronaut's lifetime risk of fatal cancer from space radiation must be below 3 percent:
Shield design studies based on nominal biological response models are highly questionable in their result and may lead to designs in which astronaut risk are much higher than anticipated on the basis of such models...current technology is adequate for a single lunar mission for casual astronauts. Revolutionary technology needs to be developed for human space missions to Mars for NASA's vision.
The problem is that the White House panel expects a round-trip mission to a Martian moon to take 750 days, potentially exposing astronauts to more radiation than is currently allowed.
The panel asked NASA if it would consider accepting higher risks, but it's unclear what the agency's next move will be.
What do you think?
Sep 16, 2009
The radiation that barrels through the solar system is from the Sun. Our solar system is largely protected from galactic radiation by the heliosphere.
Other than the fuel to land and take off from the planet, why go to Mars' moons first? What sense is it to go 98% of the way there? I've read of being able to use CO2 in Mars' atmosphere to produce the necessities for return fuel, with byproducts of water and oxygen. Great! They suggest sending the first ship to do this, then send the astronauts in a second ship and return in the first. My question is why not send materials, including a half dozen of those fuel/water/oxygen generators to Mars first? Seed the planet. We can do that now... no human requirements. Then the astronauts go... later, with a lighter load (or more shield), perhaps faster... all the return materials would be already on Mars. Who says we have to carry everything along first time?
Water is one of the best radiation shields available. That is why spent nuclear fuel is kept in pools. I work in a space lab, several researchers have been investigating the radiation problem and their opinion is that water shielding is the best method for long term protection of space travellers.... ... At least, until we are able to build space "ships" of the massive types seen in science fiction. That won't happen until there is some way of getting large quantities of material to orbit cheaply and safely. Rockets are not suitable - even the ancient Sea Dragon design doesn't have enough payload capability.
I've yet to be convinced that the Apollo-series missions - with equipment comparatively "tin-can"-ish compared to today - actually took human astronauts to and around the moon. What - we are expected to believe that 3 guys in a tin can survived the deadly van Allen belt - that worries astronauts on the shuttle (that doesn't even go NEAR the belt) even today? Can anyone say "snow job"? And before anyone says the big "C" word - when is the last time any of us saw a pic of the "moon landing" sites from an earth-based telescope? Never? No, I didn't think so... And now NASA and whoever actually "owns" them wants to waste billions more on "going to mars"? I believe we COULD go (as in, we have the technology and means to do so if we wished) - but I don't think we ever will (given how little time this planet has left). NASA may do a "moon landing" snow-job to pretend they went, but humans alive during this last gasp of this universe will never set foot on mars. Not that I can think of any practical, useful reason to go, other than "it's there" (like the reason to climb a mountain)...
A trip to Mars is nothing but a ridiculous waste anyways. They thought that the moon missions would have us out exploring the universe like in "Star Trek" by now, but the best they can come up with, almost a half century later, is "lets go to Mars"? Why are we even debating the possibility of wasting time and money to send a few fools to Mars, when there is so much more that needs fixed here on planet earth?
Looks like a lot of people aren't reading prior comments here, especially about the nature of the radiation. Moving on, while the posts here might sound overly casual, volunteers could be found that would accept the greater risk of contracting cancer. There's polls that support that. But even if all the technical issues are solvable or acceptable, the primary problem is funding.
@zclayton3: Thanks for the info about particle radiation. I was under the impression that it was solar wind radiation that created the danger, and I assumed that solar wind had a frequency just as everything in the Universe has a frequency. As they say, it's all "vibes." :-) That is, unless there are anti-vibes.
The discussion so far has covered every day radiation. But how can we possible account for a coronal mass ejection that accompanies violent solar flare activity? Even if you could line a ship with lead, could there possibly be enough physical shielding without the development of some kind of radiation -based force field to augment it. By the time we can harness that degree of power, we' may be on the verge of a breakthrough to FTL travel. Mars will no longer be relevant-- it simply cannot sustain life as we know it on Earth. We'd be better off going to other star systems in search of another "Goldilocks" planet. Let's keep exploring with robots. So far it's been enlightening and there have been tremendous strides made in the supporting science and technology. Aren't the serendipitous rewards enough for now?
We really need to get more of the population off Earth and onto another planet. All it takes is a Big enough Volcano or a big rock or ice cube dropping on us to extinguish our species for all time. Space exploration is needed for the future of our species. Now in the short term, what we learn from space has tended to have many applications on earth. So we benefit in many ways. I still think we need to build a permanent base on our moon first. That will teach us many important skills that will help any long term mission to other planets like Mars.
What we do on Mars? The safety of the cosmic journey is the most important problem which arises if exploration of other planets.A technology based on wires and screws not set too high expectation in depth exploration of space because of high costs and high risks for cosmonauts.Research supported in plasma physics could give answer to effective protection from cosmic radiation.Do not forget the Earth is full of life,poorly researched - I refer to the major problem of cancer also -and that the recovery of raw materials and development of appropriate technologies for Space Exploration might be effective to a stable base on Moon.I think efforts should be focused in this direction until the development of appropriate and secure technologies.
Sitting there reading this at your PC, you're getting radiation. In fact, the biggest dose you'll likely get across your whole life is from the person you're married to, from their Potassium-40, a natural isotope. You're also eating and breathing in radon and other "daughters" of uranium, carbon-14, and every time you take a cross-country flight up above most of our shielding atmosphere, you get a nice dose of cosmic rays. It sums up to between 100 and 200 milli-rem or mrem (0.1 rem) each year, depending on where you live. Double your dose if you live at higher altitudes. We try and limit your dose to 5 REM per year. *Don't sweat it*. Your body handles it just fine. This article has problems because Astronauts Up There simply do not get this yearly dose. P-40, yes; radon, nope. That has to be subtracted out first, and "background" radiation is the most radiation that people ever encounter. We simply do not understand the link between ionizing radiation and cancer very well. The happy reason is that we haven't had a nuclear war to give us a good statistical base of victims to study. If we choose to send people on a 1,000 day mission (2.7 years) there are other hazards, like them driving each other crazy, that have to be looked at; radiation is just one of them. Choosing an extremely low-energy chemical oxidizer drive forces that trajectory. Each atom only gives up a few electron volts. Switch to nuclear power, and each atom now gives up about 200 million electron volts. 10^8th difference. We've used nuclear reactors in space; they've powered the deep space exploration vehicles for decades. And, of course, Project Orion from long ago (1962) was the best of all. That was 3 months to Mars, and if they had to turn around, they could. If you have sufficient power, then you build the craft on the Moon, and surround the crew area with three feet of, well, dirt. Yep. Good old dirt. Dirt is astonishingly good at stopping gamma radiation. If it can be poured into concrete, so much the better. Launching from the Moon is simple compared to Earth. Lay out a few miles of track, accelerate it until it lifts off the track. Anywho, that's my two cent's worth. -- Dave
Why can't we let the people going decide what risk is acceptable? That makes the most sense to me. I mean, the chance to go see Mars is well worth the risk of cancer to many people. What level of risk is worth it? Have we really become that pathetic? I don't think the problem is the risk of cancer, I think the problem is the risk of liability. People are exposed to carcinogenic chemicals every day, most of us don't even know, and there isn't any payoff there. At least there is a payoff of going down in history as the first person to Mars! We're ready when we decide we're ready. We weren't ready to send people to the moon until we thought the soviets were. We have no ideology anymore. Everyone is so skeptical such a dangerous mission would never survive. I mean consider the world wars where tens of thousands died in a single day. And we have the world screaming about a few thousand dying over years in Iraq. We've become a nation terrified of death, like thats the worst thing in the world. So much taken for granted.
If I'm not mistaken, even the high-energy particles that make up the solar wind carry a charge of some kind, hence the auroras here on Earth. The magnetic field of Earth causes those particles to curve down towards the poles, thus they can be deflected/diverted. The gamma rays are more of a problem in that they are rays and not particles. They also cover more than a single frequency making it difficult to deflect or disrupt them. Perhaps the UHMW-PE (Ultra High Molecular Weight PolyEthylene) mentioned by boothby in the first post would help. There is also a product called "decayed uranium" that we used for storage of a radioactive medical product as lead was not sufficiently dense. What about a "sandwich" of foil made from the uranium and the polyethylene to create a denser shield without too much additional weight?
People are missing something when talking about mass and energy to move a craft from Earth to Mars... The Moon. Built the shields and craft there, removing the need to "BLAST" from earth. The moon has all the raw material need to make most of what is needed. If the govt didn't abandon moon flights and research into using the moons resources back in the 70's we probably would have already been on Mars!
Currently, the only way to shield astronauts is with mass, and lots of it. Moving tons of mass to Mars and back requires thousands of tons of fuel. That's the way it is . . . laws of nature and such. Creating some kind of magnetic shield requires gigawatts, and we don't know how to generate that in a portable package. It's gotta be low mass, remember? And then there's the problem of astronauts living in this magnetic field for years. Is that safe? I don't know, and neither does anyone else. We are not ready to send men to Mars.
Technologically we are simply not at the point of a Mars Mission. Getting there and back is not all the problem. Doing so at an acceptable risk is the rest of the problem. A Mission to Mars would be a stunt, a bragging event like being first on the moon. Returning to the Moon would allow us to acquire some badly needed knowledge while exploring what it would take to effectively travel to the other planets.
Sooo.... establishing a foothold in a new frontier poses some risks... huh? Offhand, I would say that today's astronauts probably stand a slightly better chance than when people were doing this sort of thing with only a covered-wagon, and a couple of sickly horses. So, has humanity lost all of it's gumption... or what? Myself... well given the opportunity to die in space, as opposed to finally slowly rotting away in some convalescent home while being force-fed massive doses of pharmaceutically-approved drugs by beauty-college trained nurses and staff bent on job security?.... Let me at it!
Earth's field is one Tesla but it's hundred of miles thick. To make our shuttle safe we would need a high frequency field equivalent to 1,000 or 1,000,000 Teslas. It doesn't mean we should give up on space exploration, we just need to better way of producing power than boiling water with nuclear power.
@ gusherod The radiation in question is particle radiation, not gamma or x-ray frequencies. The issue is highly ionized nuclei such as iron with a plus 5 to 10 or higher charge on it. This is a heavy particle with a lot of energy and inertia to deflect. Collision with other atoms such as an aluminum skin on a ship causes showers of other ions to break free of the aluminum along with some additional x-rays. A heavy plastic layer inside the aluminum skin may stop these less energetic showers but more research needs to be done. Shielding ultimately adds mass to move and currently there is only so much you can do with materials. The final answer will probably be a combination of a magnetic field and physical shielding.
Today, I think a trip to mars is several decades away (if we are lucky at that). Logistics such as energy, health, and consume-ables are not there for the length of days needed for the trip. Too many things go wrong and when you're far from mother earth, not much you can do about it and hope that you have a escape pod.
Trying to use physical matter to create shields seems old fashioned. Surely radiation has a frequency, so the way to conquer radiation is to attack it with back-fire radiation, and thus neutralize it, or muffle it.
They need to create a magnectic field around the ships hull to protect. It can be done.A pos.Or. neg field.That is the ?
They need to create a magnectic feild around the ships hull,to stop the radiation.Yes, It can be done.
Surrounding the living quarters with water or UHMW-PE (Ultra High Molecular Weight PolyEthelyne) would ruther reduce transmitted radiation through the hull--perhaps to reduce the risk to acceptable levels. What has not yet been addressed (well, it certainly was only poorly addressed as of a 2004 space exploration conference I attended) is muscle atrophy for such long duration missions. Remember--once you've got these guys out to Mars, they've been in zero-G for almost a year. How are they going to be able to stand up and walk around? Now, Mars' gravity is only about 3/8 of Earth gravity, but these guys are going to be wearing heavy space suits, life support gear, and be carrying equipment. Having them ride makeshift stationary bicycles, ellipticals and treadmills will not be sufficient. They'll need a large, habitable centrifuge.