"Spell checking aint what it used to be."
Posted on 08/01/2005 1:19:26 PM PDT by LibWhacker
The radiation encountered on a journey to Mars and back could well kill space travellers, experts have warned. Astronauts would be bombarded by so much cosmic radiation that one in 10 of them could die from cancer.
The crew of any mission to Mars would also suffer increased risks of eye cataracts, loss of fertility and genetic defects in their children, according to a study by the US Federal Aviation Administration (FAA).
Cosmic rays, which come from outer space and solar flares, are now regarded as a potential limiting factor for space travel. "I do not see how the problem of this hostile radiation environment can be easily overcome in the future," says Keran O'Brien, a space physicist from Northern Arizona University, US.
"A massive spacecraft built on the moon might possibly be constructed so that the shielding would reduce the radiation hazard," he told New Scientist. But even so he reckons that humans will be unable to travel more than 75 million kilometres (47 million miles) on a space mission – about half the distance from the Earth to the Sun. This allowance might get them to Mars or Venus, but not to Jupiter or Saturn.
Risky business
Helped by O'Brien, the FAA's Civil Aerospace Medical Institute in Oklahoma City investigated the radiation doses likely to be received by people on a 2.7-year return trip to Mars, including a stay of more than a year on the planet. The study estimated that individual doses would end up being very high, at 2.26 sieverts.
This is enough to give 10% of men and 17% of women aged between 25 and
34 lethal cancers later in their lives, it concludes. The risks are much higher than the 3% maximum recommended for astronauts throughout their careers by the US National Council on Radiation Protection and Measurements.
The risks are smaller for older people because cancers have less time to develop. But women are always in more danger than men because they live longer and are more susceptible to breast and ovarian cancers.
The study warns that cosmic rays would also increase the risk of cataracts clouding the eyes. Furthermore, men exposed to a solar flare might suffer a temporary reduction in fertility, and the chances that any children conceived by travellers to Mars will have genetic defects are put at around 1%.
Serious brain damage
The study's lead author, the FAA's Wallace Friedberg, highlights other work suggesting that heavy nuclei in cosmic radiation cause "serious brain damage" in mice, leading to memory loss. "Heavy nuclei exposure must be a serious consideration for space missions such as a trip to Mars," he says.
Improving spaceships' shielding by using water, hydrogen or plastics can protect astronauts to some extent. But this is limited by the constrictions of craft weight and design, Friedberg points out.
"Increased speed would also reduce radiation exposure" by reducing journey times, he notes. "And drugs or food supplements that can reverse radiation damage are being considered."
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."
Not my idea...read it in a book...but they could use huge tanks of water. Maybe get the water from the moon now that they've found some. Then once your at Mars and have buried your habitat beneath a suitable amount of dirt to block most of the radiation....BOOM....you have enough water to for the mission and beyond. The necessary thickness of water is more than lead....but there will be a use at the end....plus can even the environuts whine about using water?
They will as soon as they have the freedom to do so. That freedom will come with the recognition of private property rights in outer space. Maybe it is still a hobby. So was the West at every stage when it was just fur trapping.
Yuppers.
Why the Tigers version of Aloysius? I know I'm biased, but Bucketfoot Al would look so much better in his White Sox garb. And the A's would admittingly be the most appropiate.
Secondary emissions. I can post more this evening.
That's an interesting comment. I assume you are serious. Why would relativistic speed make a difference?
Never went to West Point or anything, but personally I believe it's an urgent matter of national security. In the short term at least, we should seize cislunar space and deny it to the other major powers.
Give me a few hours, I am up to my a$$ in alligators at the moment. :-)
This is 226 REM, or, assuming that a midsection CAT scan gives you 5 REM, about 45 CAT scans and as far as chest plates, more than 2000.
Typically there are minor blood changes seen at 50 REM whole body, and an acute dose of 300 is life threatening. If this analysis is correct, getting 226 REM over a year represents a serious dose.
Space radiation is difficult to shield. The low energy stuff, slow propons and electrons, get shielded easily. The high energy stuff generates braking radiation (bremsstrahlung) IN the shielding, so at some point doubling the shielding no longer cuts the radiation in half.
This is a factor in Shuttle and space station operations. While nuke plant workers are limited to an occupational dose limit of 5 REM annually and rarely come close to that, the limit for astronauts was increased to 15 so they can continue to fly. Astronauts get lots of radiation compared to nuke plant workers or medical isotope workers.
There are solutions- massive ship with an outer annulus of lunar rock or water is one, as is a lighter craft with a solar sail to reduce transit time.
http://www.space.com/scienceastronomy/radiation_evarm_020716.html
NASA's been thinking about this for a long time, but rarely discusses it as a problem- I'm guessing that they feel they'd lose support from the public given the average American's fear of ionizing radiation.
http://www.sirr.unina.it/Asi/collegamenti/Introduction/NASA/NASA_Strategic_Plan.pdf
They're getting nowhere near relativistic speeds, unless you mean the impacing particles.
Thanks for the reminder of the sorry-*ssed state we find ourselves in these days. I wonder what the Founding Fathers would say.
I think it may be a very real problem too.
I have a couple of old cans of lead paint in my garage. Maybe NASA could paint the spaceship to Mars with it. (hope they like skyblue pink)
Yeah, but earth ain't the same as Jupiter or Saturn.
"Spell checking aint what it used to be."
But, if you're flying though space at 95% of the speed of light, those same cosmic rays will suddenly have an average relative speed of, say, 99% the speed of light wrt your ship. They'll have much greater penetrating power and your old shielding, designed for slow speeds, will no longer be sufficient.
According to Einstein, the laws of physics are the same in any inertial reference frame, that is for anyone going at constant velocity and not accelerating. If so then the velocity of incoming cosmic rays should be independent of the velocity of the platform you are on. If that wasn't the case then you could measure the average velocity of these incoming high speed particles and calculate your actual speed relative to ... to what, that's the problem. There isn't any what. So your velocity can't make a difference.
OTOH, feel free to educate me on what really happens.
Personally, I believe the fact that we're sending billions of $ to people who want us dead -- Arabs, China, take your pick -- is a tad more urgent than claiming a rock in outer space.
The moon obviously belongs to us. As for the cislunar space, wouldn't that be something akin to Columbus claiming the Atlantic Ocean for Spain? Seems like space is something like international waters, except maybe the space above our territory, to some degree.
According to Robert Zubrin in "The Case For Mars," you can shield a small portion of the spaceship with enough lead to create a safe environment. The astronauts would have to reside inside this safe zone for the duration of a solar outburst.
But there's no predicting when a flare up will occur or how long it will last.
It seems totally do-able, but a bit of a pain.
Murdoch Baxter is _no_ Whovian.
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