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Radiation a Mars trip hazard?



 
 
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  #11  
Old December 13th 03, 09:07 AM
William A. Noyes
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Default 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  
Old December 14th 03, 03:35 AM
William A. Noyes
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Default 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  
Old December 14th 03, 03:35 AM
William A. Noyes
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Default 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  
Old December 15th 03, 01:49 PM
Mike Miller
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Default 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  
Old December 15th 03, 01:49 PM
Mike Miller
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Default 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  
Old December 22nd 03, 03:44 AM
Earl Colby Pottinger
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Default 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
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  #17  
Old December 22nd 03, 03:44 AM
Earl Colby Pottinger
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Default 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  
Old December 24th 03, 02:40 AM
Remy Villeneuve
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Default 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  
Old December 24th 03, 02:40 AM
Remy Villeneuve
external usenet poster
 
Posts: n/a
Default 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  
Old December 25th 03, 12:34 AM
William A. Noyes
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Default 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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