[Flyndaran]

ARISE!

Okay, I've been reading up on cosmic radiation. All the many interesting ideas for shielding just don't work so well with the galactic monster rays.

So looking around I came upon this thread.

I'd like to know if my slightly different interpretation is correct.

Air is 14.7 lb per square inch.
Iron is 0.284 or so lb per cubic inch.

This sounds like it would take 49 inches to equate to the same mass as our atmosphere.
This coupled with our planet's magnetic field knocks the cosmic radiation down from 662+/-108 mSv per year it is in interplanetary space to
the 0.3 mSv per year it is at sea level.
A factor of around 2200
(I think the magnetosphere deflects some of the least powerful galactic cosmic rays, but I'm not sure.)

On habitats you can avoid our inevitable yearly exposure to radon of over 2 mSv for Americans.

That right there would allow you have the same background radiation dose as sea level Americans with only 1 over 6 2/3 the shielding.

So a mere 7.35 or so inches of iron or whatever as it's mass that matters. Times 70 for DR using rolled homogenous steel as close enough...
Gets us a mere 515 DR, 52 dDR

Even the hardest realistic future should allow you to drop that down further without any long term health risks.
As it is 50 dDR is a single armor module for SM +14, 3 for SM +13, etc. unstreamlined