L5 satellite workshops.

This is exactly the sort of thing I had in mind. You mentioned a
construction technique by Zubrin - but there is a potentially better
one which was mentioned in the NASA AMES study of 1975 led by O'Neill.

The method is to melt metal in a vacuum. The metal then evaporates
and deposits itself on any intercepting surface (This technique is
already used to silver telescope mirrors on Earth).

What you could do is melt the metal at the centre of a light
spherical form and after a few months or even years a thick layer of
metal will have deposited itself to form the shell of a spherical
habitat.

Also some of the habitats in the AMES studies were only hundreds of
tonnes in structural mass (without shielding). I'm sure that a modest
habitat of just a few thousand tonnes could be home to the first
workers.

Also the first SPS's could be built on a small scale and sold to
smaller entrepeneurs on the Earth instead of going straight for the
biggest style SPSs. This has been done with wind farms on the Earth.
(Or alternatively a larger SPS could be built in modular form and
smaller parts of it sold off to smaller businesses/individuals).

With less mass to launch the lunar base/NEA operation could be
suitably scaled down.

Mark
>
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> I also agree that to start things off we need something on a far
> smaller scale than the proposed Island One concept - I also said
> that. I know that we will probably never see funding on the scale of
> Apollo either.
> What we will see though is something on the funding scale of the
> ISS - and yes it will be a money sink for a decade or two - BUT, and
> this is the big difference - if people see that there is some direct
> benefit to people back down on Earth (i.e. SPS) then there will be a
> stronger argument for the spending.
> An Initial demonstration SPS will most likely be launched from
> Earth anyway - once the technology is proven to work we can move
> forward from there.
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>
> In Zubrins book, 'the Case for Mars', details were given on the
construction
> of pressurised habitation domes, on the Martian surface. The idea
was, to use a
> polymer like Vectran or Kevlar, to form an inflatable sphere,
within which,
> large amounts of habitation space would be available. The
inflatable structure
> would be protected from micro-meteors, UV light, and abrasive
Martian dust, by a
> hard, UV resistant, un-pressurised shield dome. On Mars, one could
use these
> pressurised domes to grow food for a Martian colony. Although the
Martian
> atmosphere and surface, would cut solar flare doses by a factor of
4 (compared
> to free space) and cosmic ray doses by a factor of about 3, this is
not enough
> to ensure safety for people living on the Martian surface. Even
when one takes
> the shielding effect of the Martian atmosphere into account, people
living in
> one of zubrins domes, would take about 10 rem per year, in combined
solar flare
> and cosmic ray doses.
>
> However, although Zubrins idea has limited use on the Martian
surface, it has
> tremendous value as one of the building blocks for an Earth
orbiting, or L5
> workshop. According to Zubrin, a pressurised Vectran or Kevlar
sphere (inflated
> to 1/3rd atm pressure), 50 metres in diameter, would weigh as
little as 4
> tonnes. The internal volume of the sphere would be approximately
65450 cubic
> metres. The hard, un-pressurised sphere, that encases the
pressurised sphere,
> would weigh about 16 tonnes. The un-pressurised outer sphere could
be covered
> with lunar material. This would shield out solar flares and the
vast majority of
> cosmic rays. Within the inner, pressurised sphere, light weight
dividers could
> be used, to divide the habitation space into various compartments.
The
> compartments would be used as workshops, for the production of
various satellite
> and SPS components from lunar materials.
>
> It would even by possible to spin the inner-dome, in order to
produce
> artificial gravity. If rotation is used, then the central axis of
the sphere
> would function as a satellite assembly hall, with airlocks at both
sides. A 1000
> MWe SPS, could be constructed within the assembly hall, from
components produced
> within the workshops. The SPS would be constructed with its solar
wings folded
> up, so that it fits into the assembly hall. Upon completion, the
SPS would
> launched out of one of the axial airlocks. With its solar wings
unfurled, the
> SPS would power its own electric thrusters, and within a few
months, it would be
> positioned into GEO, ready to produce power. The SPS would produce
88 billion
> Kw-hrs of power over a 10 year life time. If power is sold at 5c/Kw-
hr, this
> represents 4.38 billion dollars worth of power.
>
> The completed hab/workshop might weigh as little as 100 tonnes,
minus
> shielding of course. The hab could be launched into LEO, using a
single Russian
> energia. The hab kit, would be assembled by astronauts working out
of the
> international space station, in LEO. It would then be carried to
L5, by a Solar
> electric propulsion craft, over a timescale of many months. The
shield dome
> would weigh in at around 20,000 tonnes, but would consist almost
entirely of
> imported, unprocessed lunar material. This assumes the existance of
a lunar
> base, capable of operating a mass-driver.
>
> Much equipment would need to be imported from Earth, in order to
manufacture
> the various satelite and SPS parts. This would weigh many hundreds
of tonnes,
> but would, for the most part, be a one-time investment. It would be
delivered to
> LEO by energia, and loaded into the hab by the crew of ISS, prior
to the habs
> departure for L5. So, if we estimate the total mass of the hab to
be 100t, and
> the equipment and furnishings mass 900t, the whole thing could be
launched to
> LEO, using 10 energias. At 250m each, that gives us a launch price
of $2.5Bn.
> The SEP would probably weigh about 100t, and if we assume
construction and
> development to cost $250m, that gives us a round $500m for the SEP
ferry.
>
> There are other costs that haven't been taken into account, and the
> off-the-head estimates could vary by a fair bit, in reality. But
such a scenario
> seems profitable to me. In fact, if 1 SPS could be produced per 6
months, and
> lunar material costs are assumed to be 10$/Kg (Zubrins pessimistic
estimate),