Space Settlement FAQ's]

Forwarding Dennis May's response to Mike Combs.

Monart Pon

Subject: [Starship_Forum] Re: Space Settlement FAQ's
Date: Wed, 14 Nov 2001 12:23:02 -0600
From: Dennis May
Reply-To: Starship_Forum@yahoogroups.com
To: Starship_Forum@yahoogroups.com

I wrote:

>At some point hundreds of people will be involved
>in mining on the moon and asteroids before an
>orbital habitat is constructed.

Mike Combs wrote:

>I would disagree with "hundreds" (the NASA-Ames Space Settlement studies
>assumed a lunar crew of only around a dozen or so supporting the
>construction of a Stanford Torus), but agree the mining camps will
>certainly precede the large, orbital habitats.

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

The large orbital habitats are quite a different
thing. They will require a real industrial
infrastructure.

I am an engineer at a custom metal fabricating
facility. Several of my relatives have worked in
mining or been engineers in heavy industry.

For real factory type settings they will necessarily
have to have almost daily shipments of spare parts.
Weekly shipments will cause work stoppages, monthly
shipments would likely cause the entire project to
collapse. Once you have mining and fabricating underway
it will still take a large number of people to do the many
other tasks real factory work requires. The Soviets
spent nearly all their time keeping their space stations
repaired much less produce anything with them. Real
world fabricating requires a great deal of down time
for repairs, if spare parts are not instantly available
even more down time is involved. Efficiency suffers
if you don't have the right tool for the right job or
the right repair person for the needed repair. I
would expect a dozen fabricators would be needed just
to keep the mining equipment and vehicles hauling miners
and supplies maintained. You would still need miners,
raw material production workers, finished metal
production workers, metal product fabricators, supply
and ordering specialists, habitat maintenance, supply
receiving, shipping out [launch specialists], repair
and refurbishing of incoming and outgoing space
vehicles, medical/dental, non-metal fabricating and
repair, food production/preparation, waste recycling,
etc. Every time you pull someone off production to do
the twenty other jobs needing to be done you have
stretched the time factor to useful production.
A dozen people may know how to do all the jobs needing
to be done but they do not have the critical mass
necessary to do the work efficiently or in a timely
manner.

I wrote:

>For reasons of efficiency and health these people should spend as much time
>as practical under a 1 G environment.

Mike Combs wrote:

>Unless one can build habitats on the moon or Mars which spin around on
>circular tracks and can
>accommodate 10,000 to 10,000,000 people, then there's no use in arguing
>with the original point.

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.

I wrote:

>Those constructing the orbital habitats can be shuttled
>to a Moon base for 1 G time more efficiently than
>traveling back to the Earth.

Mike Combs wrote:

>Perhaps, but the transportation costs of this would still be significant.
>This cost could be eliminated entirely by building structures in orbit
>which rotate for artificial gravity. The transportation costs for
>shuttling hundreds of
>people back and forth from the moon could pay for a great deal of space
>construction.

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.

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

I wrote:

>Mars has water-ice ready to be mass driven to wherever needed.

Mike Combs wrote:

>Mars would be a poor choice as a source of needed water. The gravity well
>is much steeper than that of the moon, and we don't have a vacuum at the
>surface
>which means mass driver operations will be problematic.

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.
Mars has the raw materials, the deep gravity well is
not much of a consideration once a nuclear/electric
infrastructure is built up. The small amount of ice
or water available from the moon means finding the
resources elsewhere shortly after the Moon has an
industrial infrastructure.

I see the entire buildup of space industrialization
as a series of tradeoffs involving lost time versus
up front expenses. The slower the build up the cheaper
it is but the longer it takes. Time is money so
building up slowly involves unseen losses. The
up front money will come slowly unless big government
gets off our backs. Only time will tell how much
we have lost by building up slowly. If the money
isn't coming or isn't reliable a small shielded
near Earth orbit rotating habitat may be the best
we can expect for a long time. If the resources
were available I would rather see an industrial
infrastructure built up on the Moon and Mars
prior to or in parallel with building space habitats.
The free market should decide the priorities and
what is actually built but we are far from a
free market situation.

Dennis May