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."
Havent you heard the romuor about Chinese spies steeling technology from the US. Especially its a romour about that when it comes to the military. I heard for a while ago that the Chinese probably caught up decades of worth of technology. Didnt the Chinese send a man to space a little while ago.
So I would turn into a sex?
When I was physics cosmic rays were the highest energy waves in the EMR spectrum and not charged particles.
From a NASA website:
"Galactic cosmic rays (GCRs) come from outside the solar system but generally from within our Milky Way galaxy. GCRs are atomic nuclei from which all of the surrounding electrons have been stripped away during their high-speed passage through the galaxy. They have probably been accelerated within the last few million years, and have traveled many times across the galaxy, trapped by the galactic magnetic field. GCRs have been accelerated to nearly the speed of light, probably by supernova remnants. As they travel through the very thin gas of interstellar space, some of the GCRs interact and emit gamma rays, which is how we know that they pass through the Milky Way and other galaxies. "
Interesting, it was quite a while ago that I was in physics and quite a while ago before that that the books we used were written. Other sources I'd seen put Gamma waves at the top of the EMR. That's why I hedged my statement with "when I took physics". Thanks.
Plus giving campaign donations to a certain President helps also..
Glad to see you come around, Dr. Millikan! :-)
Wow. Never saw that one. :-)
I figured I had seen every cheesy science fiction movie in history. LOL!
However, reading over the thread, I think folks are beginning to understand some of the problems of long duration spaceflight outside of the protective envelope surrounding the Earth.
No, it's a problem if you stay out there too long. Make the trip in six weeks instead of 9 months using a nuclear rocket, and the problem goes away.
Fire up a magnetic field around the ship using the massive power given by a nuclear reactor, and the cosmic rays go around the ship, and you can spend 6 months getting to Jupiter.
Cosmic radiation is only a problem in space travel if you don't use nuclear power.
How about generating a miniature Van Allen radiation belt around the ship with magnetic fields, focussing any infall at the best-shielded areas?
...My question was based on the idea that it is so hard to stop cosmic rays. If WE can't stop cosmic rays from sailing right on through us, then we aren't actually absorbing much. Damage comes from what we absorb, making energy from different particles dissimilar in effect, right?
Why put a space? The particle will just cross that space.
Well, that rather depends upon the particle. Some secondary particles will decay after travelling a certain distance (or conversely expressed, a certain duration). Others will radiate in a non-linear direction from the creation point. I wasn't familiar with the identity of the secondary particles produced when cosmic rays are absorbed into shielding.
If we had wanted to, we could have launched the Shuttle with the main tank attached and leave it up there, so that now we'd have a bunch of big empty cylinders in orbit.
I had heard that suggestion a few years ago...but apparently they decided not to for one reason or another.
Let's send Jesse Jackson and Dirtbin!
thus, in the first case, they are being emitted at a lower frequency towards us, and we are hitting them at speed, raising the apparent frequency from its lower frequency. In the second case, they are being emitted at higher frequency, and we are pulling away, which lowers the freqency...thus, in a universe where both the emitter and receiver are moving, the results are rather ambiguous.
You are right, cosmics do not deposit much energy in us. But consider the difference- a cosmic ray hitting a carbon atom in graphite, or hitting a carbon atom in your mitochondrial RNA.
Our astronauts get about three times the dose of the average nuclear worker on Earth, for a shorter time. I put up a link somewhere above to a NASA site that goes into some detail about astronaut radiation and mitigation techniques.
I also did not explain too well about the secondaries from the shielding- I provided a link to a transport calculator that showed how little the high energy particles are attenuated- but it did not show how much of that energy is converted into other radiation. If you use a high-Z shield (look at teh Bethe-Bloch stopping power equation- Hi-Z materials stop charged particles more efficiently than low Z ones) the stuff spalls off lots of neutrons that interact further, as well as showers of energetic electrons and photons. Your shield becomes a radiation source requiring more shielding.
I think the answer is to build a lunar base and build your Mars or asteriod ship there. Heck, maybe with a beanstalk launcher! A manned ship that can explore the solar system is going to be big anyway, the shielding bulks it up a bit that's all.
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