From: Dennis May

I assume a Stanford Torus is small and intended to
be pre-built on Earth with the Moon resources
providing only shielding.

Fine, but that's contrary to the recommendations of the NASA-Ames/Stanford
Summer Study Group. They assumed the metal and glass structure of the
habitat as well must come from space-derived resources to be economical.
For myself, I'd have to say that building such a torus at even 1/2 or 1/3 of
the scale but entirely from Earth-boosted components doesn't sound very
likely to me, even if the shielding did come from space resources (but
granted, that's the lion's share of the total mass).

How you get from where we are to where you want
to be is very much the point. The huge infrastructure
required for such building projects will mean dealing
with human health issues on a large scale before the
even larger scale becomes possible.

The NASA studies assumed that we could get to the Stanford Torus stage of
operations with just a few people on the moon who would presumably get
rotated back to Earth at regular intervals. Orbital workers were assumed to
have small, shielded, rotating habitats available to them well before
completion of the first Stanford Torus.

A very small shielded habitat can only house
a very small work crew. The kind of habitats
some have envisioned will require work crews
in the hundreds or thousands working for many
years. You would not want this structure
rotating while being constructed.

Agreed, but again, the NASA experts seemed to feel that small, shielded,
rotating habitats could be built with sufficient capacity to house all of
the workers needed to build the first large, Earthlike habitat.

Until you have produced a large habitat with
sufficient mass for protection from radiation a
rotating habit is only fixing one of two health
problems.

There was a "construction shack" design published in one of the SSI
Conference Reports that was based on clusters of Space Shuttle ETs. They
were surrounded by radiation shields derived from the very first lunar
materials retrieved to HEO. They rotated to provide a full 1-G. This can
be done on a scale much smaller than Island One.

A circular track on the moon sheltered
from radiation fixes both problems.

Again, you seem to proceed from the idea that this circular track and large,
high-speed vehicle is going to be easier to construct than a small,
rotating, shielded habitat in orbit. Both construction programs would take
place in vacuum, and well away from the Earth. I don't see the lunar track
being all that much cheaper. Once a small habitat is set rotating in orbit,
it basically will rotate forever.

Those working
on the habitat during construction will need to go
somewhere to regain health, the infrastructure on
the moon or asteroids will need workers also, so
rotating crews would solve both problems.

Perhaps, but I have a very difficult time seeing regularly rotating orbital
workers to the moon and back as ever being economical. Less expensive than
rotating to Earth and back, granted, but the cheapest solution of all is to
provide them with spin and radiation shielding at the construction site, and
letting them stay put.

Mass drivers or light gas guns can push out projectiles
with ablation noses and steering rockets to put them
into whatever corrected orbits they later require.

Certainly true, but we're now discussing projectiles (and launchers) of much
greater complexity and size than what O'Neill proposed for his lunar
operation. To me, getting needed water from the lunar poles or NEOs is many
times easier and more economical. I can't see Martians ever making a profit
from the export of water when they reside at the bottom of such a steep
gravity well, are so distant from the initial markets, and must compete with
both lunar ice and water-bearing NEOs.

Mars has the raw materials, the deep gravity well is
not much of a consideration once a nuclear/electric
infrastructure is built up.

I'm of the opinion that deep gravity wells will continue to be a significant
economic issue for a good time to come.

The small amount of ice
or water available from the moon means finding the
resources elsewhere shortly after the Moon has an
industrial infrastructure.

And if there were no such thing as CC type NEOs, I'd agree that Mars would
be next.

Regards,

Mike Combs

From: Dennis May
I assume a Stanford Torus is small and intended to
be pre-built on Earth with the Moon resources
providing only shielding.

Fine, but that's contrary to the recommendations of the NASA-Ames/Stanford Summer Study Group. They assumed the metal and glass structure of the habitat as well must come from space-derived resources to be economical. For myself, I'd have to say that building such a torus at even 1/2 or 1/3 of the scale but entirely from Earth-boosted components doesn't sound very likely to me, even if the shielding did come from space resources (but granted, that's the lion's share of the total mass).
How you get from where we are to where you want
to be is very much the point. The huge infrastructure
required for such building projects will mean dealing
with human health issues on a large scale before the
even larger scale becomes possible.

The NASA studies assumed that we could get to the Stanford Torus stage of operations with just a few people on the moon who would presumably get rotated back to Earth at regular intervals. Orbital workers were assumed to have small, shielded, rotating habitats available to them well before completion of the first Stanford Torus.
A very small shielded habitat can only house
a very small work crew. The kind of habitats
some have envisioned will require work crews
in the hundreds or thousands working for many
years. You would not want this structure
rotating while being constructed.

Agreed, but again, the NASA experts seemed to feel that small, shielded, rotating habitats could be built with sufficient capacity to house all of the workers needed to build the first large, Earthlike habitat.
Until you have produced a large habitat with
sufficient mass for protection from radiation a
rotating habit is only fixing one of two health
problems.

There was a "construction shack" design published in one of the SSI Conference Reports that was based on clusters of Space Shuttle ETs. They were surrounded by radiation shields derived from the very first lunar materials retrieved to HEO. They rotated to provide a full 1-G. This can be done on a scale much smaller than Island One.

A circular track on the moon sheltered
from radiation fixes both problems.

Again, you seem to proceed from the idea that this circular track and large, high-speed vehicle is going to be easier to construct than a small, rotating, shielded habitat in orbit. Both construction programs would take place in vacuum, and well away from the Earth. I don't see the lunar track being all that much cheaper. Once a small habitat is set rotating in orbit, it basically will rotate forever.

Those working
on the habitat during construction will need to go
somewhere to regain health, the infrastructure on
the moon or asteroids will need workers also, so
rotating crews would solve both problems.

Perhaps, but I have a very difficult time seeing regularly rotating orbital workers to the moon and back as ever being economical. Less expensive than rotating to Earth and back, granted, but the cheapest solution of all is to provide them with spin and radiation shielding at the construction site, and letting them stay put.
Mass drivers or light gas guns can push out projectiles
with ablation noses and steering rockets to put them
into whatever corrected orbits they later require.

Certainly true, but we're now discussing projectiles (and launchers) of much greater complexity and size than what O'Neill proposed for his lunar operation. To me, getting needed water from the lunar poles or NEOs is many times easier and more economical. I can't see Martians ever making a profit from the export of water when they reside at the bottom of such a steep gravity well, are so distant from the initial markets, and must compete with both lunar ice and water-bearing NEOs.
Mars has the raw materials, the deep gravity well is
not much of a consideration once a nuclear/electric
infrastructure is built up.

I'm of the opinion that deep gravity wells will continue to be a significant economic issue for a good time to come.

The small amount of ice
or water available from the moon means finding the
resources elsewhere shortly after the Moon has an
industrial infrastructure.

And if there were no such thing as CC type NEOs, I'd agree that Mars would be next.

Regards,
Mike Combs

From: Ryan Healey [mailto:bestonnet_00@...]

It would be made almost entirely of lunar materials with only a very small
amount bought up from earth (I can't seem to get to the study on the net but
from what I can remember it is less then 100 kT coming up from earth that
actually goes into the station).

52.6 kT. This includes hydrogen, nitrogen, biomass, furnishings, and even
the colonists themselves.

Regards,

Mike Combs

From:
Ryan Healey [mailto:bestonnet_00@...]
It would be made almost entirely of lunar materials with only a very small
amount bought up from earth (I can't seem to get to the study on the net but
from what I can remember it is less then 100 kT coming up from earth that
actually goes into the station).

52.6 kT. This includes hydrogen, nitrogen, biomass, furnishings, and even the colonists themselves.
Regards,
Mike Combs

From: Ian Woollard [mailto:ian.woollard@...]

> As for Mars it isn't really all that good. Gravity well too steep,

It's not THAT bad, it's a bit stronger than the moon, but much less
than the earth.

It would be close to twice as strong, yes? Lunar gravity is 1/6th, Mars
gravity is a bit over 1/3rd.

Yeah, it's a rotten radiation shield, practically a vacuum at 1% of
earth normal.

That's a point that I don't think many Mars advocates appreciate. The
radiation problem on Mars would still be around 1/3 as bad as in free space,
and only a bit better than that on the lunar surface.

Still, atleast the atmosphere contains CO2: 2CO + O2 is a rocket
fuel although not a fantastic one; and there are traces of water
vapour.

An undeniable advantage.

And
Mars is closer to the asteroid belt, and Deimos is near the edge of
Mars's gravity field, so you could probably go there, refuel and
head off for the belt, come back, have a great time.

I always argue with the notion of Mars as a way station to the belt (being
at the bottom of a gravity well makes you "further away" even if you're
closer in actual distance), but I think a much better case can be made for
Deimos as a way station. I think you're onto something here.

Regards,

Mike Combs

From:
Ian Woollard [mailto:ian.woollard@...]
> As for Mars it isn't really all that good. Gravity well too steep,
It's not THAT bad, it's a bit stronger than the moon, but much less
than the earth.

It would be close to twice as strong, yes? Lunar gravity is 1/6th, Mars gravity is a bit over 1/3rd.
Yeah, it's a rotten radiation shield, practically a vacuum at 1% of
earth normal.

That's a point that I don't think many Mars advocates appreciate. The radiation problem on Mars would still be around 1/3 as bad as in free space, and only a bit better than that on the lunar surface.
Still, atleast the atmosphere contains CO2: 2CO + O2 is a rocket
fuel although not a fantastic one; and there are traces of water
vapour.

An undeniable advantage.
And
Mars is closer to the asteroid belt, and Deimos is near the edge of
Mars's gravity field, so you could probably go there, refuel and
head off for the belt, come back, have a great time.

I always argue with the notion of Mars as a way station to the belt (being at the bottom of a gravity well makes you "further away" even if you're closer in actual distance), but I think a much better case can be made for Deimos as a way station. I think you're onto something here.

Regards,
Mike Combs