This graph shows it most clearly as it gives a range of materials from hydrogen to lead.As you can see on the right, even the smallest hydrogen shield reduces the radiation dose. Whereas for aluminum, there's a large portion of the right curve where the aluminum makes you worse off, but eventually helps some as you approach 30g/cm^2. For lead, it's the entire curve to beyond 30grams/cm^2 where it makes the effective dose much worse. Carbon fiber composite would be somewhere near water as far as effectiveness. As you can see, it's better than aluminum.
Quote from: Robotbeat on 08/19/2016 12:56 pmThis graph shows it most clearly as it gives a range of materials from hydrogen to lead.As you can see on the right, even the smallest hydrogen shield reduces the radiation dose. Whereas for aluminum, there's a large portion of the right curve where the aluminum makes you worse off, but eventually helps some as you approach 30g/cm^2. For lead, it's the entire curve to beyond 30grams/cm^2 where it makes the effective dose much worse. Carbon fiber composite would be somewhere near water as far as effectiveness. As you can see, it's better than aluminum.Wow, I didn't know liquid hydrogen is such a superior shielding material. Can you post a link to that article?
Also, cosmic rays are fast protons for the most part. Many if them far higher energetic than anything we can produce in particle accelerators. Whatever atom they hit, it's going to be smashed to pieces ...
The health risks from galactic cosmic ray (GCR) exposure to astronauts include cancer, central nervous system effects, cataracts circulatory diseases and acute radiation syndromes. Cancer and cataracts are the main concern for space missions in low Earth orbit, while for long-term space missions outside the protection of the Earth’s magnetic field cancer risks are predicted to exceed acceptable risk levels, and non-cancer risks are of concern for the higher organ doses of long-term space missions compared to missions in low Earth orbit. Annual GCR organ absorbed doses and dose equivalents vary over the solar cycle between 0.1 and 0.2 Gy/y and 0.3 and 0.6 Sv/yr, respectively for average spacecraft shielding thicknesses. Protons dominate absorbed doses, while heavy ions, low energy protons and helium particles, and neutrons make important contributions to dose equivalent because of their large quality factors. The high energies of GCR limit practical shielding amounts from providing significant attenuation. The exploration of Mars will require missions of 900 days or longer with more than one year in deep space where exposures to all energies of GCR are unavoidable and doses only modestly decreased by radiation shielding.
A while back I saw a documentary about Chernobyl radiation research on TV, so no link. It was quite interesting.They researched several different populations from mice to wild horses. All at radiation levels that were expected to cause severe issues. The populations were very healthy and had no increased rate of birth defects. With one notable exception. Migratory birds who arrived in the area exhausted and with bad immune status and bred there had an increased number of birth defects. So it seems the immune system plays an important role in fighting radiation related damage.There was an interesting experiment with lab mice too. They took a batch of mice and exposed half of the batch to Chernobyl radiation for a while, several weeks. Then they exposed both the Chernobyl group and a control group to severe radiation. With present theory it was to be expected that the Chernobyl group pre exposed would fare worse because of their higher total exposure. The opposite happened. The Chernobyl mice fared significantly better. Like they developed an ability to deal with radiation better because of their pre exposure.
QuoteThe exploration of Mars will require missions of 900 days or longer with more than one year in deep space ...
The exploration of Mars will require missions of 900 days or longer with more than one year in deep space ...
Quote... where exposures to all energies of GCR are unavoidable and doses only modestly decreased by radiation shielding.
... where exposures to all energies of GCR are unavoidable and doses only modestly decreased by radiation shielding.
Quote from: Semmel on 08/19/2016 06:59 amAlso, cosmic rays are fast protons for the most part. Many if them far higher energetic than anything we can produce in particle accelerators. Whatever atom they hit, it's going to be smashed to pieces ...Unless it's a hydrogen atom, of course!
The idea that just occurred to me is that there is probably a better solution if you make a combination water bed/air mattress type unit, that can be moved around the inside of the crew section as needed. Because of this, you can keep "communal" water to a minimum, and instead make every crew member responsible for their own water store.
Quote from: mikelepage on 07/02/2017 08:38 amThe idea that just occurred to me is that there is probably a better solution if you make a combination water bed/air mattress type unit, that can be moved around the inside of the crew section as needed. Because of this, you can keep "communal" water to a minimum, and instead make every crew member responsible for their own water store.It's an interesting idea. However, you don't really need a mattress when you're in the interplanetary coast phase, which is when you need the greatest radiation shielding. Where you do need a mattress is on Mars, but it would only protect you from radiation coming from below, and that's straightforwardly dealt with anyway.
Quote from: CuddlyRocket on 08/19/2016 06:04 pmQuote from: Semmel on 08/19/2016 06:59 amAlso, cosmic rays are fast protons for the most part. Many if them far higher energetic than anything we can produce in particle accelerators. Whatever atom they hit, it's going to be smashed to pieces ...Unless it's a hydrogen atom, of course!Not at all. High-energy protons (starting with ~300 MeV) "smash to bits" even other individual protons.