Radiation shielding vs. size

Oh, there's another aspect of this issue of radiation shielding
requirements when scaling upward in habitat size I should mention.

There was a reason why O'Neill was so optimistic that habitats would
quickly graduate up from Island 1 to Island 3 scales. In a Stanford
Torus or Bernal Sphere design, there's a separate radiation shield, and
that's a separate line-item in the overall construction budget. But
when you scale up to Island 3 dimensions, the greater thickness of
structure underfoot (and maybe a bit more soil thickness) along with the
greater thickness of air overhead eliminate the necessity for a separate
radiation shield. That line-item drops from the budget. So that's one
of the reasons why building a habitat for a thousand times bigger
population won't cost anywhere close to one thousand times as much.

I've had people argue to me that space habitats will get built alright,
but they'll always be cramped and crowded like Hong Kong or worse,
reasoning that more living space means more expensive construction so
obviously the builders will be saving money by cramming the people in.
But I don't think they're thinking about the square-cube law
relationship that Dan brings up.

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of Combs, Mike

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of Dan Wylie-Sears

> And if it turns out that passive-mass radiation shielding is a major
> part of the cost, doubling the size will get you eight times the space

> for four times the shielding cost; doubling again will make it 64 for
> 16. Additional room keeps getting cheaper, up to the largest size
> that's structurally feasible with your materials.

I would expect the pressure-vessel hull to be a much pricier item per
square meter. But your overall point still holds in that case as well.

Regards,

Mike Combs

Regards,

Mike Combs