|
Post by Count Zero on Feb 14, 2006 8:20:56 GMT -4
I think that if lead was a good shield for particle radiation, it wouldn't do too well in this alternate role...
|
|
|
Post by PhantomWolf on Feb 14, 2006 10:08:33 GMT -4
your URL is wrong. FixedAs to lead, it's the worst idea possible to use as particle shielding because as a dense metal it produces high levels of Bremsstrahlung (Braking Radiation.) This is why I find the "six feet of lead" argument the funnist of the HB's claims. Their way of "shielding" the Astronauts from the particles of the VA-Belts would actually fry anyone inside with the Bremsstrahlung X-Rays produced by the particles slamming into the shielding. Just by common sense, a low desity metal (Aluminium for example) or a high density polymer are far better shields because they have low to no Bremsstrahlung but still stop the particles, and that's exactly what Apollo used.
|
|
|
Post by JayUtah on Feb 14, 2006 10:22:04 GMT -4
Well, six feet of the stuff would work. Bremsstrahlung occurs in the outer layers, but would be absorbed by the inner layers. It would take only a fraction of a centimeter of lead to attenuate the particle flux to practically zero, but too thin and you get secondary radiation.
If you draw a graph of measured dose from charged particles versus shield thickness, the curve goes up slightly and then drops off rapidly. The rise is due to Brehmsstrahlung that is not abosrbed.
No engineer ever has suggested six feet of lead. Mauldin, whose book originated this claim, recommends six feet of "shielding" and you have to read elsewhere in the book to discover he's talking about rocks or gravel.
|
|
|
Post by sts60 on Feb 14, 2006 10:57:55 GMT -4
And that was for an interstellar voyage, right? Do you have title/document number handy, by any chance?
|
|
|
Post by JayUtah on Feb 14, 2006 11:02:58 GMT -4
Yes, that was for a generation ship in interstellar space achieving velocities of approximately 0.3 c. That means nothing for cislunar exploration.
Mauldin, John H. Prospects for Interstellar Travel. Univelt, 1992. ISBN 0877033447.
|
|
|
Post by sts60 on Feb 14, 2006 11:33:22 GMT -4
You da man. Thanks.
|
|
|
Post by Count Zero on Feb 14, 2006 17:37:07 GMT -4
|
|
|
Post by Count Zero on Feb 15, 2006 2:44:05 GMT -4
OK, now the link is really fixed. I still think it's a cute story.
|
|