Given the enormous start-up costs of the O'neill vision, it seems unlikely that
Island one will be the first colony to be built. I have been looking at a
different approach. My idea centres around placing a workshop in L5, that is
specifically designed to construct SPS modules. For lack of a better name, I
will call this island A. The basic element of the workshop is an iron sphere,
approximately 40 metres in diameter. The sphere rotates twice per minute. The
sphere is divided into cylindrical floors. The floors are divided into crew
quarters, manufacturing workshops, ore processing facilities, a hydroponics bay
and a satellite assembly hall. The satellite assembly hall is a cylinder that
lies along the axis of rotation. At each end of this assembly hall, there lies
an airlock. These are used both during the launch of finished SPS modules and
for the docking of supply ships, ore carrying ships and various other
spacecraft. The assembly hall is 10 metres in diameter and 40 metres long.
Lunar ores are delivered to the facility through its axial airlocks. The
ores are then taken to a small workshop, where they are processed into
manufacturing materials such as Calcium, Titanium, Iron, Aluminium, Magnesium,
Silicon, Rutile, Ilmenite, e.t.c. These materials are then used in various other
small workshops for the manufacture SPS parts.
The assembly hall is far too small to house a full scale SPS satellite. For
this reason it may be easier to produce the SPS in modules and assemble them
tele-robotically outside of the habitat. If a 20MWe SPS can be manufactured and
assembled in one week, then a 1000MWe SPS could be built in 1 year. If we assume
a 40 year life time, and a 0.1$/KWhr rate of return, the SPS will be produce
$35billion through out its life time. This amount would certainly exceed the
cost of producing it.

Rotation seems to me to be a nice-to-have rather than a minimal requirement
for an initial orbital workshop.

Rotation seems to me to be a nice-to-have rather than a minimal requirement
for an initial orbital workshop. Maybe, but if he's intending duty shifts of a year or more, some level of artificial gravity would be good. But with a rotation rate the same as Island 1, but with only a fraction of the diameter, I'm thinking the centrifugal force produced would be much less than a G. "How much is enough" is still an open question, but I suspect some gravity will be better than none. The kind of thing he's talking about is what they called the SpaceManufacturing Facility or SMF(or sometimes the "construction shack") back in the old studies.
Regards,

Valery Polyakov spent 437 days on Mir. So we have proof positive that a
duty stay of 437 days followed by return to Earth is acceptable. I
speculate that that could be stretched to a yet even longer period of time.
Let's suppose that a duty stay of two years is acceptable. How necessary
is rotation?

>>>>Rotation seems to me to be a nice-to-have rather than a minimal requirement
for an initial orbital workshop.>>>>

>>>Valery Polyakov spent 437 days on Mir. So we have proof positive that a
duty stay of 437 days followed by return to Earth is acceptable. I
speculate that that could be stretched to a yet even longer period of time.
Let's suppose that a duty stay of two years is acceptable. How necessary
is rotation?>>>

The volume of a shuttle external tank is approximately 2000m2 or 68600 cubic
feet. Does anyone know what its exact dimensions are?

Rotating or non-rotating, it stretches imagination to believe that people
would continue to be productive beyond 437 days couped up inside a tin can
40 meters in diameter. If a 40-meter sphere is their entire world, then
probably psychological factors will dominate physiological factors once we
get above a year duty stay. We have to bring these people back down to
Earth so they don't go crazy. People are not robots.

Given that, I wouldn't expect duty stays much longer than 437 days or so
anyway. If a person is not going to stay for years and years, then I
don't see why we have to design for rotation. We know already that people
can survive a 437-day stay in microgravity and return safely to Earth. We
really don't need to make an orbital workshop any more complicated than it
minimally needs to be. Then let's say that one might expect the initial SPS construction workersto work duty shifts from a year to 400 days duration and then get rotated back to Earth. Than at a later point, after accumulation of significant experience in space construction, we might expect a newer SMF with large, rotating crew quarters or perhaps even an Island 1 in order to reduce transportation costs by extending duty shifts to several years. Of course Island 1 offers the prospect of reducing "commuting costs" to essentially 0 by providing the option of having workers who live in space full time. But I think everyone's in agreement that Island 1 won't get built at the onset of the program, and even O'Neill agreed with this point.

>>>>Given that, I wouldn't expect duty stays much longer than 437 days or so
anyway. If a person is not going to stay for years and years, then I
don't see why we have to design for rotation. We know already that people
can survive a 437-day stay in microgravity and return safely to Earth. We
really don't need to make an orbital workshop any more complicated than it
minimally needs to be.>>>>

>>>>>Rotation seems to me to be a nice-to-have rather than a minimal
requirement
>for an initial orbital workshop.>>>>
>
> The idea of keeping a large number of workers in zero-g for months
or years at
>a time, seems a bit dubious to me. When they get back to Earth and
suddenly find
>that their bones are brittle due to de-mineralisation, are we likely
to get
>sued?

There was a back of the envelope design by O'Neill shortly before his death.
It called for 6-8 Shuttle external tanks to be tethered together and spun
providing necessary volume for a small 100 person colony, workstation place.
SSI

There would be much more architectural freedom to choose alternative
configurations of the tanks if they did not rotate. For example, seven
tanks could be arranged in hexagonal closest packing arrangement if that
were desired (just an example --- I don't know whether hexagonal closest
packing arrangement would be good or bad, but at least you'd be able to
consider it in a non-rotating design).

I concur with the need to design for significant teleoperation. Whether
humans could be entirely absent from an orbital workshop is an open issue.
I suspect that for any significantly complicated thing that we wish to do
in the near future, humans will be required to some extent. Should the
orbital workshop be continuously crewed, or should it be occasionally
human-tended when there is a need to do especially complicated tasks.
Unknown.

>>>There would be much more architectural freedom to choose alternative
configurations of the tanks if they did not rotate. For example, seven
tanks could be arranged in hexagonal closest packing arrangement if that
were desired (just an example --- I don't know whether hexagonal closest
packing arrangement would be good or bad, but at least you'd be able to
consider it in a non-rotating design).>>>

>>>>Why the assumption that workers are required for this operation?
Couldn't be same thing be done by semi telerobotic operation with
only a common support structure and minimal sheilding. Every machine
and process used for the construction shack will be specially designed
so why not design for zero human presence?>>>>

There would be much more architectural freedom to choose alternative
configurations of the tanks if they did not rotate. For example, seven
tanks could be arranged in hexagonal closest packing arrangement if that
were desired (just an example --- I don't know whether hexagonal closest
packing arrangement would be good or bad, but at least you'd be able to
consider it in a non-rotating design). It's funny you should use this as an example. I remember one of the space manufacturing reports which included a paper on a SMF design which used a rotating baton shape with 7 clustered tanks at each end, with each tank pointing "upward". Each tank was split into 7 levels, each of which was divided into 3 pie-shaped wedges. So each tank in both clusters could provide 21 apartments. Interior space planning would be less constrained if the workshop did not
rotate. The inside of a tank is curved. Only certain orientations of
the tanks will allow efficient use of that space when there is gravity.
If the workshop doesn't rotate, then curved walls aren't that constraining. I've always felt that there would be lots of wasted space inside the kind of tank stations advocated by the Space Islands group, where they're trying to join the tanks end-to-end to form a torus. (Or at least one would have to choose between wasted spaceor decks which were not level in most locations.) In the baton type approach I mentioned, where the tanks are vertical instead of horizontal, I think there would be less wasted space, even with concentric-arc shaped decking.

In a message dated 04/20/2001 6:34:26 AM Pacific Daylight Time,
rmenich@... writes:

>>>Consequently, upon his return to Earth he was walking unaided on his first
day back Earthside.

Over the weekend, I made some rough calculations for the pressure vessel that we
would need, for the outer hull of Island A. I assumed an Iron pressure vessel.
This would be constructed from lunar Ilmenite derived Iron, that was processed
in a small initial facility, within a shuttle external tank. Depending upon how
the Iron is treated, a wide range of material properties are possible. So I
assumed that we would be dealing with a soft, pure iron, purified using the
Carbonyl process. In this case, the tensile strength of the soft iron would be
about 500MN/m2, and its properties would closely resemble those of mild steel. I
assumed a safety factor of 8. This probably is not excessive, given that the
pressure vessel is all that stands between the crew and oblivion. I also assumed
that the facility would be pressurised to 1/2 atm. The thin walled pressure
vessel equation, yields a wall thickness of 0.8cm. Given that the density of
pure iron is 7900Kg/m3, and the radius of our pressure vessel is 20m, the mass
of the vessel comes out to be 317.677 tonnes. In order to produce this much
Iron, we would need to reduce 862 tonnes of Ilmenite, into Fe, TiO2 and O2. The
pressure vessel itself could be formed using vacuum deposition, so the initial
external tank facility would only need to reduce and purify the the iron. This
could be achieved by hitting lunar Mare soil, with hot carbon monoxide and
passing the resulting vapour through a fractionating column. The pure iron
carbonyl, will condense out at its own specific temperature. It could then be
decomposed into carbon monoxide and pure iron. The depleted lunar soil residue
from the process, can be used as a shielding material.

>>>A submarine is a small self contained little world where
people are constantly in each other face and would not have much more
room than a SMF is likely to have. Just like an SMF you can't step
outside to get away from it all for a little while. ( granted the SMF
crew could go for a spacewalk ) In thinking about lengths of stays you
have to remember that the people who crew an SMF will be there primarily
to build things, they will not be astronauts in the original sense of
the word . They will not be doing research.>>>

I can see that we are talking at partly crossed purposes here. The SMF I
am considering would be in Earth Orbit, be it high or low and be used as
a stepping stone to building bigger facilities. The one that you are
talking about appears to me to be a somewhat ideal one that could be
sent out on a voyage to the asteroids ( wherever they are ) in which
case yes there would have to be long stays. For the type I am talking
about fresh fruit and Vegetables would be brought up on the supply
vessels. As for financial incentives I imagine that any initial job will
be highly paid no matter how long you are up there for. Green Plants
would be nice, but in a zero G ( or almost ) environment does anyone
know what will happen to them ? I know there have been experiments on
germinating seeds, but larger plants ? ( I realise that that is a
separate discussion in itself ) Also separate quarters / bed chambers
would be nice but impractical at the beginning. Of course once the
facility is running they could expend some time on expanding the
facility so that it could incorporate these things. The first facilities
are likely to be Rough and Ready. In other words quickly built with a
minimum of comforts, just enough to get the work done with minimum
expense. They will be cramped, smelly, crowded and most likely partly
dangerous and most definitely ugly, but they will get the job done. Not
everyone will want to or be able to work in those conditions but they
will pave the way for bigger and better facilities. If we try and go
for the better facilities straight away all we will be doing is
hampering ourselves.( both mentally and financially )

I found an on-line illustration of the ET station configuration I was trying to describe below. This is from Al Globus' website. http://lifesci3.arc.nasa.gov/SpaceSettlement/spaceres/images/figII2-1.GIF

Thanks for the reference. Kind of makes one want to cry. In 14 tanks
could live 252 people comfortably; so says the site you reference. In 100+
Shuttle flights so far, our government has not seen fit to deliver even one
external tank to orbit. Potential orbital housing for over 1500 people
sits at the bottom of the Atlantic. We're currently $4 billion over
budget on a Space Station that at max would house only a handful or two of
people. And NASA says that Tito needs an armed guard to go pee in the
middle of the night while he's on it, despite joy rides it gave to Jake
Garn, John Glenn, and others on the Shuttle in years past.

Looks like they have done some major renovations to the site since the
last time I looked at it. Much better now than it used to be.
B