Rotating Mirrors

From: Andy Nimmo [mailto:andy-nimmo@...]

Sorry guys, but please do forget forever about both the Bernal Sphere and
the Stanford doughnut. Both were shown way back to be such that they would
drive any inhabitants crazy for psychological reasons, in next to no time.
The only one of O'Neill's habitats that really would work is the Island 3.

If you can find the cites for that study, please do post them. But I find
it odd that at least a couple of people on this maillist who, probably like
me, have voraciously read everything they could lay their hands on on High
Frontier subjects don't ever recall hearing this objection before.

I'd also have to chime in with the others who have pointed out that Island 3
was only visualized as coming about long after many Island 1's (or Stanford
Toruses) and Island 2's were in existence, and like them would also question
how any such study could arrive at definitive conclusions prior to the era
of orbital habitats existing.

You are quite correct George, that there would be several Gs at the outer
edges of the farthermost part of those mirrors - but so what? Human beings
are not going to be out there. What will be out there is glass and steel,
both of which can be made to withstand such Gs without too may problems.

But the point the critics have made (and I think it's a valid one) is that
we've never made a mirror over a mile wide which didn't sag even under the
force of only 1 G, and that any such sag would prevent the mirror from
functioning as a planar mirror.

I do think that habitats at the scale of Island One (if not the actual
geometry) will predominate once the era of orbital habitats is fully
matured. But I consider it likely such habitats will have non-rotating
primary mirrors. O'Neill himself once said that nobody would be more
surprised than he if orbital habitats, once a reality, looked very much like
the pictures currently available, and said that one should look at present
designs as proofs of concept only.

Regards,

Mike Combs

From:
Andy Nimmo [mailto:andy-nimmo@...]
Sorry guys, but please do forget forever about both the Bernal Sphere and the Stanford doughnut. Both were shown way back to be such that they would drive any inhabitants crazy for psychological reasons, in next to no time. The only one of O'Neill's habitats that really would work is the Island 3.

If you can find the cites for that study, please do post them. But I find it odd that at least a couple of people on this maillist who, probably like me, have voraciously read everything they could lay their hands on on High Frontier subjects don't ever recall hearing this objection before.

I'd also have to chime in with the others who have pointed out that Island 3 was only visualized as coming about long after many Island 1's (or Stanford Toruses) and Island 2's were in existence, and like them would also question how any such study could arrive at definitive conclusions prior to the era of orbital habitats existing.

You are quite correct George, that there would be several Gs at the outer edges of the farthermost part of those mirrors - but so what? Human beings are not going to be out there. What will be out there is glass and steel, both of which can be made to withstand such Gs without too may problems.

But the point the critics have made (and I think it's a valid one) is that we've never made a mirror over a mile wide which didn't sag even under the force of only 1 G, and that any such sag would prevent the mirror from functioning as a planar mirror.

I do think that habitats at the scale of Island One (if not the actual geometry) will predominate once the era of orbital habitats is fully matured. But I consider it likely such habitats will have non-rotating primary mirrors. O'Neill himself once said that nobody would be more surprised than he if orbital habitats, once a reality, looked very much like the pictures currently available, and said that one should look at present designs as proofs of concept only.
Regards,
Mike Combs