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#11
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Radiation a Mars trip hazard?
"Dr. O" wrote in message ... http://www.nytimes.com/2003/12/09/sc...ce/09RADI.html The thing I don't understand is that people have been spending much more time in orbit than the round-trip to Mars. Although the upper atmosphere does shield them somewhat, the majority of the radiation is still getting through. Why are they so concerned then about radiation? Also, lead shielding will have to be installed in any Mars spaceship anyway because of the possibility of solar flares. As to the shielding, I suspect it will be a plastic or part plastic. If it contains lead or other heavier metal, they will be on the outside. And the low density materials will be on the inside. Read up on "graded shielding" for radiation. When high energy particles and high energy photons strike a thin dense shield, they liberate a "spray" of other particles and photons.While the spray will have somewhat lower energy, the beta particles will have higher linear energy transfer. In short, a thin shield of a relatively dense material even as humble as aluminum may result in a higher radiation dose to the space traveler. The inner plastic layer would absorb the betas and soft gammas and x-rays. My ideal for sheilding would be to have such a large space ship that a outer wall could like that on a battleship and still have a low overall density of structure not including the fuel. I know, I am dreamer. sleeeppy...............................William A. Noyes |
#12
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Radiation a Mars trip hazard?
[1] However, lead isn't much denser than steel. If price is not a
problem and you can waste mass on dedicated metallic shielding, use tungsten or depleted uranium for shielding. That's density. Mike Miller, Materials Engineer A radiation shield should be a graded sheild. Otherwise, since high energy particles and gamma photon interactions result in a blast of lower energy particles and x-rays some of which would have a higher linear energy tranfer (LET), a thin metallic sheilding can in theory result in more radiation exposure to the astonaut. Was my previous posting on this topic deleted by a moderator? Talking to the "ether"......... .............William A. Noyes |
#13
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Radiation a Mars trip hazard?
[1] However, lead isn't much denser than steel. If price is not a
problem and you can waste mass on dedicated metallic shielding, use tungsten or depleted uranium for shielding. That's density. Mike Miller, Materials Engineer A radiation shield should be a graded sheild. Otherwise, since high energy particles and gamma photon interactions result in a blast of lower energy particles and x-rays some of which would have a higher linear energy tranfer (LET), a thin metallic sheilding can in theory result in more radiation exposure to the astonaut. Was my previous posting on this topic deleted by a moderator? Talking to the "ether"......... .............William A. Noyes |
#14
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Radiation a Mars trip hazard?
"William A. Noyes" wrote in message om...
A radiation shield should be a graded sheild. What percentage improvement does a graded shield offer over just a tank o' water? Mike Miller, Materials Engineer |
#15
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Radiation a Mars trip hazard?
"William A. Noyes" wrote in message om...
A radiation shield should be a graded sheild. What percentage improvement does a graded shield offer over just a tank o' water? Mike Miller, Materials Engineer |
#16
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Radiation a Mars trip hazard?
"William A. Noyes" :
30 meters of water should be about equal to the shielding value of the atmosphere. Of course, the tank would also provide some sheilding. And the water could have dissolved borax in it to assist the neutron absorption. Provided you don't plan to drink it. Found a graph from which I crudely interpolate that 2.2 meters of water would decrease fast neutron flux by 12 magnitudes. I think that is 10 meters of water, or 32 feet of water. Earl Colby Pottinger -- I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos, SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to the time? http://webhome.idirect.com/~earlcp |
#17
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Radiation a Mars trip hazard?
"William A. Noyes" :
30 meters of water should be about equal to the shielding value of the atmosphere. Of course, the tank would also provide some sheilding. And the water could have dissolved borax in it to assist the neutron absorption. Provided you don't plan to drink it. Found a graph from which I crudely interpolate that 2.2 meters of water would decrease fast neutron flux by 12 magnitudes. I think that is 10 meters of water, or 32 feet of water. Earl Colby Pottinger -- I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos, SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to the time? http://webhome.idirect.com/~earlcp |
#18
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Radiation a Mars trip hazard?
"Dr. O" wrote in message ...
http://www.nytimes.com/2003/12/09/sc...ce/09RADI.html The thing I don't understand is that people have been spending much more time in orbit than the round-trip to Mars. Although the upper atmosphere does shield them somewhat, the majority of the radiation is still getting through. Why are they so concerned then about radiation? Also, lead shielding will have to be installed in any Mars spaceship anyway because of the possibility of solar flares. I always figured that shielding on a interplaneraty spacecraft should use materials usable at other moments and for other purpose in the mission. A dense outer shell should try not to stop the particules but refract or reflect them. One might conceive a outer skin made of hundreds of small panels (maybe a few centimeters accross) of light materials on which incoming high-energy particules would skim accros and mostly go back toward space, like a stealh fighter mostly reflects radar (F-117), or an X-ray telescope focuses incoming photons. For the particles which could not be be reflected due to their incident angle, a second layer would absorb some of the energy. 15 centimeters of water could be used for that purpose. Only the water would be kept as ice, providing some protection from hard impacts from debris. When needed the water could be thawed back to liquid form. Photodetectors could be installed in the ice shell, monitoring the incoming radiation. But I think it would be best to try to provide a space in which radiation would not be stopped, but directed away from. |
#19
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Radiation a Mars trip hazard?
"Dr. O" wrote in message ...
http://www.nytimes.com/2003/12/09/sc...ce/09RADI.html The thing I don't understand is that people have been spending much more time in orbit than the round-trip to Mars. Although the upper atmosphere does shield them somewhat, the majority of the radiation is still getting through. Why are they so concerned then about radiation? Also, lead shielding will have to be installed in any Mars spaceship anyway because of the possibility of solar flares. I always figured that shielding on a interplaneraty spacecraft should use materials usable at other moments and for other purpose in the mission. A dense outer shell should try not to stop the particules but refract or reflect them. One might conceive a outer skin made of hundreds of small panels (maybe a few centimeters accross) of light materials on which incoming high-energy particules would skim accros and mostly go back toward space, like a stealh fighter mostly reflects radar (F-117), or an X-ray telescope focuses incoming photons. For the particles which could not be be reflected due to their incident angle, a second layer would absorb some of the energy. 15 centimeters of water could be used for that purpose. Only the water would be kept as ice, providing some protection from hard impacts from debris. When needed the water could be thawed back to liquid form. Photodetectors could be installed in the ice shell, monitoring the incoming radiation. But I think it would be best to try to provide a space in which radiation would not be stopped, but directed away from. |
#20
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Radiation a Mars trip hazard?
On reflection, I am sure Earl is right.
"Earl Colby Pottinger" wrote in message ... "William A. Noyes" : 30 meters of water should be about equal to the shielding value of the atmosphere. Of course, the tank would also provide some sheilding. And the water could have dissolved borax in it to assist the neutron absorption. Provided you don't plan to drink it. Found a graph from which I crudely interpolate that 2.2 meters of water would decrease fast neutron flux by 12 magnitudes. I think that is 10 meters of water, or 32 feet of water. Earl Colby Pottinger -- I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos, SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to the time? http://webhome.idirect.com/~earlcp |
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