Surely, the most practical shape for a pressure vessel is a sphere? You get
the maximum possible internal volume, for the minimum possible surface
area.

Incidentally, it occurs to me that the first islands to be built in space
will be more expensive than following ones. The capital costs of developing
ISRU techniques and setting up the moon base, mass catcher, mass driver
tugs and manufacturing facilities, will tend to make lunar materials much
more expensive than the few cents per kilo that is generally assumed. For
initial habitat construction, it makes sense to consider using the entire
internal volume of our habitat, rather than just the inner surface.
Island one, for example, weighs in at 3 million tonnes, shielding
included. With an initial materials cost $5/Kg, materials costs alone will
put the price of Island One at $15 billion or about $20,000
dollars/Sq-metre of internal surface area. And that figure does not take
into account the fabrication costs of island one.
What we are really paying for is not internal surface area, but internal
volume. One square metre of internal surface area might cost $20,000, but
one cubic metre would cost only $229. Having gone to so much trouble
fabricating a pressure vessel and importing millions of tonnes of material
as shielding, we waste most of the habitable volume. If we were to use the
habitat as O'Neill suggested, the materials cost of island-one alone, would
be around $2,000,000 per inhabitant.

Given the large initial costs of construction, it would make sense to
divide Island One into internal decks, thereby making use of the full
internal volume. If we were to grant each inhabitant a generous 400m3 of
living volume, the cost of housing him would be a more modest $92,000
(materials costs alone). This estimation is over simplistic, since it
assumes that the internal structure costs nothing. But even if the internal
structure doubles the weight of island one, it still makes much more sense
to consider using the entire internal volume, rather than just its inner
surface.

The larger the initial habitat becomes, the more significant the argument.

Tony

> What we are really paying for is not internal surface area, but
internal
>volume.

I couldn't agree more. I have never understood why it was so necessary
to have a long viewing distance in the island designs.

Mitchell James
mejames@...
http://www.InnerTransit.net (Email distribution for multilevel organizations)
http://www.InnerTransit.org (Homebase for collaborative engineering)

I couldn't agree more. I have never understood why it was so necessary
to have a long viewing distance in the island designs. It's not necessary if your design goal is to house acertain number of people in space. It is necessary if your design goal is tore-createsome of the more pleasant areas of the Earth's surface in space. O'Neill's design goal was the latter.

Regards,

Mike Combs

> > What we are really paying for is not internal surface area, but
> internal
> >volume.
>
> I couldn't agree more. I have never understood why it was so
necessary
> to have a long viewing distance in the island designs.
>
> Mitchell James
> mejames@...
> http://www.InnerTransit.net (Email distribution for multilevel
organizations)
> http://www.InnerTransit.org (Homebase for collaborative engineering)

I think you are missing the point of O'Neill type colonies here. They
are designed to house people for years, maybe even lifetimes, the
long lines of sight and spacious living conditions are obviously of
psycological benefit. O'Neill habitats are designed to be as Earth-
like as possible in the given volume. I think this it what makes them
so exciting and more desirable than the old idea of packing people
into rooms like a hotel in space.

Also don't forget, they are also designed to be as self-sufficient as
possible, if you start packing more people in multiple floors then
you will need more agricultural rings (in the case of island one) and
hence will increase the total mass of the colony.

Regards

Mark

> Given the large initial costs of construction, it would make sense to
> divide Island One into internal decks, thereby making use of the full
> internal volume. If we were to grant each inhabitant a generous 400m3
> of
> living volume, the cost of housing him would be a more modest $92,000
> (materials costs alone). This estimation is over simplistic, since it
> assumes that the internal structure costs nothing. But even if the
> internal
> structure doubles the weight of island one, it still makes much more
> sense
> to consider using the entire internal volume, rather than just its
> inner
> surface.

My town house occupies approximately 50% more volume than that. People
are going to need "outdoors", common areas (e.g., bars, restaurants,
gyms, libraries, meeting areas -- or at least their analogs) -- in
space as well. I wouldn't want to live in a colony where the
inhabitants had only 400m3 of volume each. Maybe prisoners wouldn't
mind -- but I sure as hell would.

Best,

Chuck Divine

>>>My town house occupies approximately 50% more volume than that. People
are going to need "outdoors", common areas (e.g., bars, restaurants,
gyms, libraries, meeting areas -- or at least their analogs) -- in
space as well. I wouldn't want to live in a colony where the
inhabitants had only 400m3 of volume each. Maybe prisoners wouldn't
mind -- but I sure as hell would.>>>

The first manufacturing facilities are likely to be expensive and
difficult to set up and unfortunately, labour intensive. Under those
conditions, it would be unreasonable to expect that we can create an
environment that is every bit as luxurious as we have come to expect in the
US and Europe. Certainly, after 20 years or so, when the price of lunar and
asteroidal material in HEO has fallen, we could create such places. But, in
the first 10-15 years, construction materials are likely to cost at least
$5/Kg and fabrication costs are likely to push the price up a lot more.
Under these conditions, habitable volume is very expensive and must be used
efficiently. If we were to try and create a spacious Earth analogue
environment in the first ten years of operations, it would certainly be for
Bill Gates and friends, only.

It must be remembered that the average household includes more than just 1
person. A house of volume 600m3 could easily accommodate a family of 4
people. Thats an average of 150m3 each of personal living space. Thats
certainly a lot more than most students get in university halls. During my
first year of university, I cohabited a house of about 500-600m3 volume,
with 7 other students. There were occasional tensions, but as long as
people have a room that they can call their own, there are seldom any
serious problems. Kitchen and washroom facilities were shared evenly
between the 8 of us. It wasn't ideal, but there were no problems.
Accommodation like this is fine, for single, unmarried people, who are
interested in working in space for a few years, earning a fortune, and then
returning to Earth.
For small families, an apartement of perhaps 400m3 would work just fine.

In the initial Space Manufacturing Facilities, individual kitchens are not
going to be a requirement. Small restaurants and common mess-halls are
likely to suffice. It is far more efficient in terms of 'use of space' and
manpower, to have a single kitchen, serving up to 2000 people and working
continuously, on a 24 hour, 3 shift basis.

We should also remember that space colonists would not function on a
night-day system, as do people on Earth. Workers are likely to be divided
into 3 shifts. While one shift is working an 8 hour stretch, another is on
8 hour relaxation time, while yet another is probably sleeping. Dining
facilities and recreational areas would be in 24 hour use, but would not
seem over-crowded.
Even in initial SMF's we could incorporate small parks, illuminated by
natural but concentrated sunlight, reflected through floor panels. An
opaque, blue glass ceiling would help give the illusion of natural skies.
Small bars, restaurants, meeting areas, take up a surprisingly small amount
of space, when taken in context with the number of customers that they
serve. The average English or Irish pub, is perhaps 500m3 in volume. If
operated on a 24 hour, 3 shift basis, it might serve 1000 people per day,
especially when you consider that most people will sit down for 20 mins,
have 1 drink and then leave.

Tony

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If we were to try and create a spacious Earth analogue
environment in the first ten years of operations, it would certainly be for
Bill Gates and friends, only. True, and I don't think O'Neill expected us to try and create such environments in the first 10 years of operation. It's important to remember that Island One was projected for an era of permanent settlement in space. It's fine to talk about small metal rooms with artificial lighting for workers who might live in space for a 1-2 year tour of duty and then get rotated back "home", which is presumed to be some place on Earth. But would you try to raise a family in a small metal room? The entire notion of the "Island" scale space habitats was to raisefamilies away from Earth in such a way that you didn't need to feel like they were deprived just because they weren't on the surface of the Earth.

Regards,

Mike Combs

in space.

[snikt]
> My town house occupies approximately 50% more volume than that. People
> are going to need "outdoors", common areas (e.g., bars, restaurants,
> gyms, libraries, meeting areas -- or at least their analogs) -- in
> space as well. I wouldn't want to live in a colony where the
> inhabitants had only 400m3 of volume each. Maybe prisoners wouldn't
> mind -- but I sure as hell would.
>

This perception varies from culture to culture. I live in an apartment with
about 150 m^3 and I, as well as all of my friends, think that it is very
spacious and comfortable. A 400 m^3 space would suffice for my residential
space and (probably) any common areas that I might use. Supposing that
people would be evenly distributed across the volume, each person would be
at more than seven meters from his/her neighbor; I would not call this
environment "overcrowded". (However, I would not be so sure about
agricultural space. Does anyone know how many cubic meters one needs to pack
crops for a person?) I think that most other Brazilians like me, as well as
Europeans and Asians, who usually live in very "concentrated" cities, would
feel right in such a place. However, Americans, who are in general used to
urban sprawls, might feel that this environment is uncomfortably cramped.

I think that even people with claustrophobia would not feel that nervous
given some architectural tricks. For example, shopping malls often are
completely closed environments, but we don't see people freaking out inside
them; probably because they are designed to have "open" spaces with
promenades and saccades, even though those open spaces do not occupy too
much volume.

> Best,
>

Best,

> Chuck Divine
[snikt]

Lucio Coelho

space.

[snikt]
> Given the large initial costs of construction, it would make sense to
> divide Island One into internal decks, thereby making use of the full
> internal volume. If we were to grant each inhabitant a generous 400m3 of
> living volume, the cost of housing him would be a more modest $92,000
> (materials costs alone). This estimation is over simplistic, since it
> assumes that the internal structure costs nothing. But even if the
internal
> structure doubles the weight of island one, it still makes much more sense
> to consider using the entire internal volume, rather than just its inner
> surface.
>

I have made the same point earlier in the Space Settlers list. For instance,
I think that the internal volume of a toroidal colony should be occupied by
tall buildings stretching almost as far as to the roof of the torus. That
would provide a near-optimal ocupancy of the internal volume while giving to
the colonists the comforting illusion, almost completely convincing, that
they are living in a conventional city. Some suggested that the spikes of
the torus could be the tallest buildings in the city...

For a spherical colony, I think that your design with the multiple coaxial
layered levels would be the best option. Put the commercial and residencial
levels close to the equator of the sphere, and the agricultural levels close
to the axis. (I think that plants will not care that much about lower
gravity, but people certainly will.) Of course, this design could make it
difficult (or impossible) to use reflected sunlight to lit the colony, but
then the solution would be artificial lighting.

O'Neil thought of space habitats as a way for multiplying land area
available for humans. On the other hand, *I* think of space habitats as a
way for multiplying resources for human beings - no matter if those
resources are distributed in a plane or in a volume. The ultimate metric for
measuring how efficient an habitat is is not the land area that it provides,
but how much people it can sustain. If you can make a "volumetric" island
one able to hold a population over 100,000 , then it is certainly better
that the original "superficial" island one for about 10,000 people.

> The larger the initial habitat becomes, the more significant the
argument.
>

Ok. My only concern with the volumetric approach is heat dissipation.
Although the volume increases with the cube of the dimensions of the colony,
the surface increases only with the square of the dimensions. So, the larger
the colony, the more difficult it is to get rid of the waste heat.
"Superficial" colonies would have basically the same ratio waste
heat/surface, but that ratio would increase linearly with the dimensions for
"volumetric" colonies. That possibly limitate the maximum size of a
"volumetric" habitat, but my first wild guess is that that maximum size
could hold a population of millions...

>
> Tony
[snikt]

Lucio Coelho

>>>>Ok. My only concern with the volumetric approach is heat dissipation.
Although the volume increases with the cube of the dimensions of the
colony,
the surface increases only with the square of the dimensions.>>>>

This is really an air conditioning problem. Another potential problem
would be the buildup of CO2 within individual rooms. The easiest solution
would be to remove stale air from each individual compartment, cool it and
pass it through the agricultural rings. A water cooled system would seem to
be the easiest solution. It is reasonable to assume that one end of the
habitat would permanently face the sun, while the other is in perpetual
darkness. We would put our radiator on the dark side of the Hab. In order
to achieve a reasonable heat dissipation rate, we would probably require a
heat pump.

>>>>If you can make a "volumetric" island
one able to hold a population over 100,000 , then it is certainly better
that the original "superficial" island one for about 10,000 people.>>>>

It also reduces the scale of the project by a factor 5 or more. The
habitat can be assembled in a much shorter space of time. An individual
government, like that of Brazil, would probably want to expand its space
infrastructure as quickly as possible. The more rapidly you expand your
facilities, the harder it becomes for a potential rival to undercut your
operation. With an impatient electorate, the race is on to produce a
return before the next election. In Brazil, as in many nations, the term of
office lasts 4 years, I believe.

>>>>For a spherical colony, I think that your design with the multiple
coaxial
layered levels would be the best option. Put the commercial and residential
levels close to the equator of the sphere, and the agricultural levels
close
to the axis. (I think that plants will not care that much about lower
gravity, but people certainly will.) Of course, this design could make it
difficult (or impossible) to use reflected sunlight to lit the colony, but
then the solution would be artificial lighting.>>>>

The axis is probably about the only place where it would be practical to
use reflected sunlight. None the less, it may be easier for us to locate
the agricultural modules outside of the hab, given that they would not
require anywhere near as much shielding. A Human rated garden of some sort,
might be well suited for the central cylindrical corridor. Concentrated
light could enter the garden through circular mirror at one end of the
axis. At the other end of the axis, would almost certainly be the main
airlock. On first arrival at the station, it would certainly be much more
pleasing to be greeted by the sight of a garden, than a cold, grey
construction bay.

Tony

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>>>Concentrated
light could enter the garden through circular mirror>>>

Did I say mirror? I meant window.