Radiation a Mars trip hazard?

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.

In article ,
Dr. O wrote:
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?

Most flare radiation and cosmic radiation is blocked by Earth's
magnetosphere, not by the atmosphere. LEO is inside the magnetosphere.

Also, lead shielding will have to be installed in any Mars spaceship anyway
because of the possibility of solar flares.

No, 10-20cm of water around a small "storm shelter" area will suffice --
the only flares of concern are the giant ones, which are rare and brief --
and that can almost certainly be arranged using things like food supplies
(even dehydrated food has a high water content) which have to be there
anyway.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

In article ,
Dr. O wrote:
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?

Most flare radiation and cosmic radiation is blocked by Earth's
magnetosphere, not by the atmosphere. LEO is inside the magnetosphere.

Also, lead shielding will have to be installed in any Mars spaceship anyway
because of the possibility of solar flares.

No, 10-20cm of water around a small "storm shelter" area will suffice --
the only flares of concern are the giant ones, which are rare and brief --
and that can almost certainly be arranged using things like food supplies
(even dehydrated food has a high water content) which have to be there
anyway.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

On Fri, 12 Dec 2003 03:36:56 GMT, (Henry Spencer)
wrote:

In article ,
Dr. O wrote:
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?

Most flare radiation and cosmic radiation is blocked by Earth's
magnetosphere, not by the atmosphere. LEO is inside the magnetosphere.

Also, lead shielding will have to be installed in any Mars spaceship anyway
because of the possibility of solar flares.

No, 10-20cm of water around a small "storm shelter" area will suffice --
the only flares of concern are the giant ones, which are rare and brief --
and that can almost certainly be arranged using things like food supplies
(even dehydrated food has a high water content) which have to be there
anyway.

Would a magnetic bubble provide protection, as if NASA's plans are
anything to go by the Mars ship will have a nuclear reactor for power
and propulsion, so wattage will be no so critical as if they were just
going to use solar panels.


Christopher
+++++++++++++++++++++++++
"Kites rise highest against
the wind - not with it."
Winston Churchill

On Fri, 12 Dec 2003 03:36:56 GMT, (Henry Spencer)
wrote:

In article ,
Dr. O wrote:
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?

Most flare radiation and cosmic radiation is blocked by Earth's
magnetosphere, not by the atmosphere. LEO is inside the magnetosphere.

Also, lead shielding will have to be installed in any Mars spaceship anyway
because of the possibility of solar flares.

No, 10-20cm of water around a small "storm shelter" area will suffice --
the only flares of concern are the giant ones, which are rare and brief --
and that can almost certainly be arranged using things like food supplies
(even dehydrated food has a high water content) which have to be there
anyway.

Would a magnetic bubble provide protection, as if NASA's plans are
anything to go by the Mars ship will have a nuclear reactor for power
and propulsion, so wattage will be no so critical as if they were just
going to use solar panels.


Christopher
+++++++++++++++++++++++++
"Kites rise highest against
the wind - not with it."
Winston Churchill

"Dr. O" wrote in message ...

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?

Because the trip to Mars is outside Earth's magnetic field, just like
most sources of radiation in space. Space craft and space stations in
low Earth orbit receive an enormous amount of radiation protection
from Earth's magnetic field.

Also, lead shielding will have to be installed in any Mars spaceship anyway
because of the possibility of solar flares.

No, it doesn't have to be lead. Any mass will do. Lead just puts a lot
of mass in a small volume, so lead shielding is not thick. [1] Ten to
eleven centimeters of water shielding is just as good as 1cm of lead
plate, and you can use the water for a lot of things (drink it, wash
in it, make oxygen out of it, use it for reaction mass, etc.) Lead
isn't useful for much on a ship.

[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

"Dr. O" wrote in message ...

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?

Because the trip to Mars is outside Earth's magnetic field, just like
most sources of radiation in space. Space craft and space stations in
low Earth orbit receive an enormous amount of radiation protection
from Earth's magnetic field.

Also, lead shielding will have to be installed in any Mars spaceship anyway
because of the possibility of solar flares.

No, it doesn't have to be lead. Any mass will do. Lead just puts a lot
of mass in a small volume, so lead shielding is not thick. [1] Ten to
eleven centimeters of water shielding is just as good as 1cm of lead
plate, and you can use the water for a lot of things (drink it, wash
in it, make oxygen out of it, use it for reaction mass, etc.) Lead
isn't useful for much on a ship.

[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

In article ,
Christopher wrote:
Would a magnetic bubble provide protection, as if NASA's plans are
anything to go by the Mars ship will have a nuclear reactor for power
and propulsion, so wattage will be no so critical as if they were just
going to use solar panels.

The idea has been explored a bit in the past. Unfortunately, you need
either a tremendously strong magnetic field, or one that spreads over a
huge volume of space (which is hard to do if it must be generated by
equipment on a small vehicle), to fend off high-energy particles well.
It's a possibility in the long term, but not something that will be
practical soon.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

In article ,
Christopher wrote:
Would a magnetic bubble provide protection, as if NASA's plans are
anything to go by the Mars ship will have a nuclear reactor for power
and propulsion, so wattage will be no so critical as if they were just
going to use solar panels.

The idea has been explored a bit in the past. Unfortunately, you need
either a tremendously strong magnetic field, or one that spreads over a
huge volume of space (which is hard to do if it must be generated by
equipment on a small vehicle), to fend off high-energy particles well.
It's a possibility in the long term, but not something that will be
practical soon.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

"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