A Suggested Program of Space Settlement]

> As I see it, when an O'Neill settlement finally comes to fruition,
I
> don't think it would be something O'Neill would recognize. I
haven't
> read O'Neill's work myself, but as I understand it, an O'Neill
colony
> is envisioned as a giant construction project using more or less
> conventional assembly techniques, but vastly scaled up. E.g. the
> pictures of giant "wheel"-type space stations being assembled in
> orbit by astronauts and a swarm of space shuttle/Venture Star type
> spacecraft and/or orbital shipyards found in many of the books
> about "our future in space."
>
> Even if launch costs could be dramatically reduced, say, to $100 a
> pound or so, I do not see such construction ever being economically
> feasible.

Assessing the viability of space habitats (O'Neill colony) through
only the ISS construction technique is not useful. Regardless of the
goal; whether Mars, Luna or space, NASA (given it's track record)
will not be the prime mover. Private economics will be. The
economics and physics, it seems to me, are inescapable: Delta-v = $.

> In terms of delta-V, construction difficulty/danger, etc.,
> it would be far easier and cheaper to build a city on Mars. For
> example, large habitable structures could be built on Mars out of
> locally-produced bricks and/or concrete (thick walls and arched
> roofs), then buried under a few feet of soil for radiation
protection
> and airtightness, with doors and windows being the only parts of
the
> building requiring anything the Romans couldn't have done.
> Transparent geodesic domes could contain greenhouses and open-air
> environments (parks, etc.), and could be produced from local
> resources. No giant orbital shipyard or complicated microgravity
> construction process necessary.

Parts of this argument are backwards, I think. Whether a factory or
construction machine, the delta-v factor is very much in favor of
space and NEO's. Same for the variety and availability of
materials. We'll know the location and type of material before we
expend the effort ($, delta-v) to go get them. And since
the "machines" need not be constructed with gravity in mind, are thus
less massive, it adds even more to the delta-v argument.

The availibility of energy (not mentioned) is at least a factor of 4
greater in near Earth space than it is on the surface of Mars.

Time delay - a significant factor for Mars, insignificant near Earth.

LACK of gravity - completely in favor of space.

I agree with all the later discussion regarding the innovative
approaches towards construction and habitation in space. I'm sure
that part or perhaps all will eventually be utilized for space, Luna
and Mars. But, IMO, near Earth space, using materials from NEO's, is
where we'll start.

And private economics will be the driver.

I say again - What imaginable scenario results in a product made on
Mars and sold on Earth for a profit?