Those cosmic rays can mess you up!
Wouldn't want to be confusing comic rays with cosmic rays, now would we?
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."
"Which is equal to 33 feet of water or 3 feet of lead."
Or somewhere inbetween for fused lunar rock!
The problem can be solved. We can go to Mars if we want to!
People have posted about solar sails and bringing back Orion (yay for Orion and hang the Limited Test ban Treaty!) to cut the transit time.
There are lots of ways!
I will volunteer for a manned mission to Mars.
So what if I die from cancer in 20 or so years.
My name would become immortal as the first man on Mars.
We are all born terminally ill anyway, so might as well make something of the life we have.
If I can get a cool superpower, I'd do it!
Hell, even unfit, 59, and asthmatic, I would still risk it just to get to the moon, let alone Mars.
A whole new meaning to "once in a lifetime". Some things are worth whatever the cost.
Cosmic rays are killing all of us ... right now. The human body is self repairing. It just can't keep up with the ray bombardment.
Back when the 'firmament' was still in place folks lived hundreds of years.
Wouldn't want to be confusing comic rays with cosmic rays, now would we?
Tinfoil hats, "sunglasses", and lead jockstraps for the crew.
Why in the world would you even think of trying to shield the entire ship?
Hey, Einstein. Over here.
First step, a political campaign to get us out of the Space Treaty so that there can be extra-terrestrial private property.
Not yet. They are still 30 years behind. But seeing that we haven't done much in 30 years, we might as well be 30 years behind ourselves. Still, they have nothing to match the throw weight of the Space Shuttle. They will have to develop the BDB if they expect to compete or even to meet the goals they have laid out for themselves. It's still Long March over there.
At that level, do we absorb?
As far as shielding, if radiation occurs within the shielding, then it seems obvious that spaced shielding would work better than just more thickness, where you have an open buffer zone before reaching the inner shielding.
No biggie in the long run. If we can't solve the problem from one direction - properly shielding the spaceships - then we'll eventually solve it from the other: repairing the physical damage. Everyone seems to be fixated on the former, but the latter would be far more widely useful in any event.
Ping to myself
Yes, we absorb energy from these hot nuclei. We are thick slabs of water that can slow a cosmic ray, and that means it deposits energy in us. If you look at the chart from the transport calculator, you see the flux is not high, but it is constant. Also the transport calculator does not include secondaries like mesons and neutrons or brems photons that come from the shielding itself. You need to use a code like MCNP for that, and that's not free on the web. So the transport calculator does not do doses, just attenuation of the incident without considering secondaries or absorption in people.
Why put a space? The particle will just cross that space.
Shielding is done in layers, though. Typically a plastic layer for real light stuff and to slow neutrons, an aluminum shield to stop light particles, then a denser shield to stop more particles and the bremstrahlung radiation, then sometimes a plastic type again for neutrons. It cuts weight; the low-Z materials stop the light particles OK. For electronics there are very small very dense shields (like the tantalum Rad_Pak) that are small. You could not make a personnel shield.
On the lighter side, a few years ago National Geographic had a shot of NASA's Janet Barth, from the "Living With A Star" program, wearing corrugated plastic sleeves filled with water for a wearable shield. Actually it was a bunch of gadjets for making tubular ice in your freezer stapled together but it sure looked cool.
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. Tie them together and fill them with water and you have a big habitat and shield. It would help to find water on the Moon, but if we wanted to we could boost a couple tons a year, if we had a good ongoing space program.
I am wondering if lead would protect them. Certainly though, by the time we develop a ship that can make the journey, a shielding material will have been invented. Human ingenuity. Of course, the space program being turned over to the private sector would make it happen faster.
Well that sounds right but the question we were originally addressing was whether this is a net increase in the hazard of the cosmic rays themselves. That is still not clear.
And I'm still not convinced that you are right (although I'm leaning in your direction.) What you are saying is that as I increase my velocity I will see a different spectrum when I look at the cosmic ray environment. It seems to me that this violates the principle that the laws of physics are the same in all inertial reference frames. There just seems to be a conflict here. I understand that relative motion between you and a source will redshift or blueshift the energy. When there are thousands or millions of surces of the cosmic rays and you must be looking at averages it just seems to me that you cannot equate this to what would happen between you and a single source. The rules just have to be different. If not, it seems like the measurment of the cosmic ray spectrum would provide a universal speedometer and I don't think there is such a thing.
Or is there?
Please enlighten me. This is a very interesting subject.
Cosmic rays will keep democrats from thinking
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