# 21551 byNiclas on April 5, 2007, 5:11 p.m.
Member since 2022-08-22
The whole Moon is covered with a dust layer (rigolith), varying form a few meters till 20 meters thick and is a mixture of many different minerals, nearly all of which containing oxgyen in considerable abundance. About 45% of the lunar soil and rocks is made up of oxgyen. The Sun puts out prodigious amounts of particles, called the solar wind, composed mostly of Hydrogen, helium, neon, carbon, and nitrogen and these solar wind particles strike the lunar surface and are implanted into mineral grains during billions of years. All the elements to create an earthlike atmosphere are thus given. The point is how to free these elements into gaseous form, with most of the oxygen and all of the hydrogen to form free water, without having to apply energy for it. It is to be discussed here:
It's here! Your new message!
# 21552 byjoe@... on April 5, 2007, 5:51 p.m.
Member since 2022-08-22
> The whole Moon is covered with a dust layer (rigolith)
need to look at its composition. In particular, nitrogen, which is by
far the major component of an Earthlike atmosphere, is very scarce on
the Moon; it's about 100 grams per cubic meter of lunar regolith.
That's a trace element, at best, and nowhere near abundant enough to
make an atmosphere out of. Any space settlement is going to have to
import its nitrogen from somewhere else -- probably the Earth, but
possibly from some other NEA with high volatile content.
Your notion of causing a "chain reaction" that magically creates an
Earthlike atmosphere without energy input is nonsense, too.
Joe Strout -- joe@...
# 21553 byEd Minchau on April 5, 2007, 10:13 p.m.
Member since 2022-08-22
Of course, one thing that the moon does get is plenty
of free energy from the sun. Nitrogen can be
imported, as you say - although I would tend to think
that importing it by slamming comets into the moon
might be a better option than bringing it up the
earth's gravity well.
(1.48 times the diameter) than the moon. I suspect
that tidal effects from Saturn might have quite a bit
to do with Titan's thick atmosphere.
Any body with an atmosphere will outgas over time -
the earth's atmosphere used to be 250 times the
pressure of today. The more massive the body, the
slower it will lose its atmosphere, so outgassing from
a hypothetical lunar atmosphere would be quite rapid
when compared to the Earth. So, the moon's atmosphere
would need to be replenished on a fairly regular
basis.
The questions become then, how much mass would the
moon lose due to outgassing in one year if it had a
100kPa atmosphere, could that be replenished in the
same amount of time, and would it even be worth it to
try to give the moon an atmosphere?
I am biased towards enclosed orbital colonies, which
would keep nearly all their atmosphere from year to
year and which have the combined advantages of the
full one gee (centripetal) as well as easy access to
zero gee and 24/7/365 sunlight.
Ed
# 21554 byJolly Roger on April 6, 2007, 8:25 a.m.
Member since 2022-08-22
I believe you meant to say "centrifugal" (as in 'centrifuge') instead
of "centripetal". Earth is 1 gee centripetal. The atmosphere is not
enclosed.
is they can be placed well within the Earth's magnetosphere and thus
protected from charged particles from the solar wind and extra-solar
sources. The Moon has little or no magnetosphere.
# 21555 byGARY ANSORGE on April 6, 2007, 10:27 a.m.
Member since 2022-08-22
Why would anyone WANT to screw up a perfectly good
airless body by putting an atmosphere around it? There
would go the ADVANTAGE of mag lev launchers, ready
access to lunar resources for orbital Mini earths. I,
frankly, have little use for large gravity wells. They
just get in the way of going where I want to
go,,,outwards.But they can be useful as resources,,,
I say , break them all up and make free flying
(read:orbiting) mini-earths.
# 21556 byEd Minchau on April 6, 2007, 11:37 a.m.
Member since 2022-08-22
No, I meant to say centripetal. Although a person or
object inside the rotating structure would be exerting
a centrifugal force on the structure "floor", the
structure itself would be exerting an equal and
opposite centripetal force on the person or object.
that's handy. Of course, if one makes the colony hull
out of sintercrete 5 meters thick, and/or the colony
generates its own magnetic field, then charged
particles and radiation become less of a worry.
Something like that would have to be done for colonies
outside of the earth's magnetic field.
Ed
# 21557 byJolly Roger on April 7, 2007, 4:30 p.m.
Member since 2022-08-22
Ed:
For space colonies outside the Earth's magnetosphere, such as in GEO
or L4/L5, I suggest a multi-layered radiation protection scheme:
1. A mini-magnetosphere (M2P2) or other magnetic shield to deflect
charged particles,
2. A meter or two of water, polyethylene or other high-hydrogen-
content material to block neutrons,
3. Several meters of rego-crete and a few centimeters of dense metal
to block gamma, x-rays and other radiation and neutral particles,
4. Genetic and chemical agents to mitigate cellular damage from
anything that gets through.
--- In ssi_list@...
# 21558 byCombs, Mike on April 9, 2007, 8:26 a.m.
Member since 2022-08-22
> I,class5091513-09042007> frankly, have little use for large gravity wells.
> Theyclass5091513-09042007> just get in the way of going where I want to
> go,,,outwards. But they can be useful as resources,,,
> I say , break them all up and make free flying
> (read:orbiting) mini-earths. This conversation is reminding me of a proposal (well, maybe more like a thought-experiment) to squeeze the moon down to a smaller diameter such that its surface gravity would be enough to hang onto a lunar atmosphere. Here is the original article: http://www.scifi.com/sfw/column/sfw1479.html And here is my response to it:
This article amused me as an example of how much effort people will put into
something just to stick to the notion of living on something like a planet
because "how in the world could anybody live on something that wasn't like a
planet?" The far more efficient plan would of course be to dismantle the
moon and reform its raw material into trillions of rotating orbital
habitats, collectively providing many thousands of times the surface area of
the earth. The "squeezed moon" would be better at hanging onto air
molecules than the present one, but one can instead rely on the
much-stronger electromagnetic force (i.e. a pressurized hull) to hold in the
air, and centrifugal force can provide a suitable substitute for gravity.
The advantages are:
plausibly imagine.
2. It would not only provide more living space than a squeezed-down moon,
but many times more living space than the entire Earth.
3. Such orbital habitats would not only have escape velocities significantly
less than Earth's, they would have utterly insignificant escape velocities.
So why so much work to squeeze down the moon rather than live as Gerard
O'Neill recommended? A clue to his thinking can be found in the quote, "... and yet safe enough to survive a technological collapse". In his
conceptualization, living on something like a planet means zero maintenance
forever, whereas living on a man-made structure obviously means maintenance
in the exact same way that ISS requires maintenance. I have two responses
to that:
1. A planet or planet-like structure undergoing as extensive a modification
as described here (or any kind of "terraforming") would probably require
periodic maintenance of some kind. Granted the maintenance cycle might be
measured in centuries, while that for an O'Neill habitat might be more like
decades, but I think conceptualizing anything undergoing this extensive a
reengineering as being as stable as the Earth is a mistake.
2. If one designed an O'Neill habitat to be as maintenance-free as possible,
one might be surprised how much could be achieved. If we want to talk about
somebody moving in and then undergoing a technological collapse, one might
manage to keep going for centuries, if the timers and motors associated with
tilting the mirrors for the day/night cycle could hold out that long.
Yeah, I know, McCarthy is just engaging in an amusing thought experiment.
It's not a serious proposal. Still, I think it well-illustrates the
planetary bias which pervades most everyone's thinking.
Regards,
Mike Combs
# 21559 byjoe@... on April 9, 2007, 9:36 a.m.
Member since 2022-08-22
> For space colonies outside the Earth's magnetosphere, such as in GEO
> or L4/L5, I suggest a multi-layered radiation protection scheme:
>
> 1. A mini-magnetosphere (M2P2) or other magnetic shield to deflect
> charged particles,
>
> 2. A meter or two of water, polyethylene or other high-hydrogen-
> content material to block neutrons,
>
> 3. Several meters of rego-crete and a few centimeters of dense metal
> to block gamma, x-rays and other radiation and neutral particles,
>
> 4. Genetic and chemical agents to mitigate cellular damage from
> anything that gets through.
of dirt will block everything (at least to Earth-normal standards), and
you're going to want that much to grow trees and such in anyway. So
it's really not a big issue -- you have your strong structural support
on the outside, a few meters or more of dirt on the inside, and you're
done.
Best,
- Joe
Joe Strout -- joe@...
# 21560 byGARY ANSORGE on April 9, 2007, 12:07 p.m.
Member since 2022-08-22
Small towns on earth(10,000 people or so) tend to be
friendly, interlaced communities where everyone knows
everyone. Unfortunately, they also tend to be nosy and
often require access to a larger city for specialized
services. I live in a town of about 65,000. Small
enough to get anywhere in a reasonable amount of time,
very friendly people,yet big enough to have most of
the infrastructure needed to provided services and
provide a reasonable degree of individual privacy.
interact with your next door neighbors, but the
museums and such were astonishing, while traffic is
horrendous. I think colonies of 10 to 100 thousand
would be very pleasant and yet still have the
infrastructure necessary for livability. A trillion
such colonies could provide for a population of,,,,a
lot of people,,,
GAry 7
GAry
> [mailto:ssi_list@... On
> Behalf Of GARY ANSORGE
>
> > I, frankly, have little use for large gravity
> wells.
> > They just get in the way of going where I want to
> > go,,,outwards.But they can be useful as
> resources,,,
> > I say , break them all up and make free flying
> > (read:orbiting) mini-earths.
>
> This conversation is reminding me of a proposal
> (well, maybe more like a
> thought-experiment) to squeeze the moon down to a
> smaller diameter such
> that its surface gravity would be enough to hang
> onto a lunar
> atmosphere.
>
> Here is the original article:
> http://www.scifi.com/sfw/column/sfw1479.html
> http://www.scifi.com/sfw/column/sfw1479.html>
>
> And here is my response to it:
>
> This article amused me as an example of how much
> effort people will put
> into
> something just to stick to the notion of living on
> something like a
> planet
> because "how in the world could anybody live on
> something that wasn't
> like a
> planet?" The far more efficient plan would of
> course be to dismantle
> the
> moon and reform its raw material into trillions of
> rotating orbital
> habitats, collectively providing many thousands of
> times the surface
> area of
> the earth. The "squeezed moon" would be better at
> hanging onto air
> molecules than the present one, but one can instead
> rely on the
> much-stronger electromagnetic force (i.e. a
> pressurized hull) to hold in
> the
> air, and centrifugal force can provide a suitable
> substitute for
> gravity.
> The advantages are:
>
> 1. It could be done without resorting to
> technologies beyond anything we
> can
> plausibly imagine.
> 2. It would not only provide more living space than
> a squeezed-down
> moon,
> but many times more living space than the entire
> Earth.
> 3. Such orbital habitats would not only have escape
> velocities
> significantly
> less than Earth's, they would have utterly
> insignificant escape
> velocities.
>
> So why so much work to squeeze down the moon rather
> than live as Gerard
> O'Neill recommended? A clue to his thinking can be
> found in the quote,
> "... and yet safe enough to survive a technological
> collapse". In his
> conceptualization, living on something like a planet
> means zero
> maintenance
> forever, whereas living on a man-made structure
> obviously means
> maintenance
> in the exact same way that ISS requires maintenance.
> I have two
> responses
> to that:
>
> 1. A planet or planet-like structure undergoing as
> extensive a
> modification
> as described here (or any kind of "terraforming")
> would probably require
>
> periodic maintenance of some kind. Granted the
> maintenance cycle might
> be
> measured in centuries, while that for an O'Neill
> habitat might be more
> like
> decades, but I think conceptualizing anything
> undergoing this extensive
> a
> reengineering as being as stable as the Earth is a
> mistake.
>
> 2. If one designed an O'Neill habitat to be as
> maintenance-free as
> possible,
> one might be surprised how much could be achieved.
> If we want to talk
> about
> somebody moving in and then undergoing a
> technological collapse, one
> might
> manage to keep going for centuries, if the timers
> and motors associated
> with
> tilting the mirrors for the day/night cycle could
> hold out that long.
>
> Yeah, I know, McCarthy is just engaging in an
> amusing thought
> experiment.
> It's not a serious proposal. Still, I think it
> well-illustrates the
> planetary bias which pervades most everyone's
> thinking.
>
> Regards,
>
> Mike Combs
>
TV dinner still cooling?
# 21561 byNiclas Jacobsz on April 11, 2007, 6:21 p.m.
Member since 2022-08-22
See my comments in Ed's message to Joe below:
tend to think that importing it by slamming comets into the moon
might be a better option than bringing it up theearth's gravity well.>
How you're gonna do that Ed? I think you read too many Sci-Fi books?
might have quite a bit to do with Titan's thick atmosphere.>
No, it more likely has to do with temperature. Titan's gravity btw is
LESS than the Moon, just 0.14 G against the Moon having 0.16 G. It is
bigger, but has a lower mass density and that's why the lower
gravity. However, Titan is very cold and thus the air molecules have
a low speed, that prevents them from escaping into space. On the
other hand, Venus, having almost the same size and gravity as Earth,
is very hot and has yet a very dense atmosphere, with 90 times
Earth's atmospheric pressure ( 9 MPa ). Mars on the other hand, has
0.4 G gravity, 2.5 times stronger than the Moon and is much colder
than Earth, but yet only a very thin atmosphere, a 170 timmes
thinner than Earth ( 6 mbar = 600 Pa ). I think the Moon has a
chance, but the only the experoiment can show for sure.
ny body with an atmosphere will outgas over time -the earth's
atmosphere used to be 250 times the pressure of today. The more
massive the body, the slower it will lose its atmosphere, so
outgassing froma hypothetical lunar atmosphere would be quite rapid
when compared to the Earth. So, the moon's atmosphere would need to
be replenished on a fairly regular basis. The questions become then,
how much mass would the moon lose due to outgassing in one year if it
had a 100kPa atmosphere, could that be replenished in the same amount
of time, and would it even be worth it to try to give the moon an
atmosphere?>
I once read that the Moon could hold a dense atmosphere during ca 100
years. If true, than there would be plenty of time to build an infra-
structure on the Moon under far more favourable conditions than
today. Possibly replenishment could be provided from processing the
bedrock material, but how would I, or anyone know the viability of
such a project today? More geological studies have to be done.
nearly all their atmosphere from year to year and which have the
combined advantages of the full one gee (centripetal) as well as easy
access to zero gee and 24/7/365 sunlight.>
How would these colonies be build on what basic design?
Niclas
# 21562 byJolly Roger on April 12, 2007, 5:46 a.m.
Member since 2022-08-22
Joe,
space colonies in which the mass is just not there yet, and for
spaceships in which it is necessary to keep the mass down.
Your soil shield is a good idea, but we are still going to need a
water tank beneath the soil and it could be metal lined with plastic.
For simplicity we may just go with a porous gravel layer below the
soil for an aquifer.
The soil shield will only work on the outside/bottom of a spinning
colony. For maximum surface area, I envisioned a long cylinder like
the alien whale probe in Star Trek IV (Save The Whales). However, it
was pointed out in another thread that this design is inherently
unstable, as a long cylinder will tend to spin end-over-end like a
cheerleader's baton.
I now envision a double-hulled colony consisting of a cylinder
containing several spheres. (Think of a mailing tube full of ping pong
balls.) Each sphere would be at least as large as the Epcot Center at
Disney World Orlando. Here is a crude drawing of a cylinder with 11
spheres:
^===========================================v
|(5a)(4a)(3a)(2a)(1a)(0)(1b)(2b)(3b)(4b)(5b)
^===========================================v
The cylinder rotates around Shuttle Bay Sphere 0 at a rate that
simulates 1 gee in Spheres 5a&b. Spheres 3a&b would be at about 1/3
gee (Martian). Spheres 2a&b would be at about 1/6 gee (Lunar).
Spheres 1 & 4 are optional.
The spheres would be attached to the cylinder wall at appropriate
distances from the center of rotation using a loop or basket
arrangement. Soil in the 'bottom' of each sphere would be shaped to
provide a 'level' surface, with 'hills' around the outside, forming a
circular/eliptical 'valley'. The cylinder could be pressurized with a
breathable atmosphere to provide backup in case of leakage of the
spheres, and for easier maintenance (jet-packed repairmen)
Well, it's just an idea I'm putting out for discussion, and like my
cylinder, it may be full of air.
Jolly Roger ;-)X
>
> You're making the problem seem much harder than it is. A couple
meters
> of dirt will block everything (at least to Earth-normal standards),
and
> you're going to want that much to grow trees and such in anyway. So
> it's really not a big issue -- you have your strong structural
support
> on the outside, a few meters or more of dirt on the inside, and
you're
> done.
>
> > For space colonies outside the Earth's magnetosphere, such as in
GEO
> > or L4/L5, I suggest a multi-layered radiation protection scheme:
> >
> > 1. A mini-magnetosphere (M2P2) or other magnetic shield to deflect
> > charged particles,
> >
> > 2. A meter or two of water, polyethylene or other high-hydrogen-
> > content material to block neutrons,
> >
> > 3. Several meters of rego-crete and a few centimeters of dense
metal
# 21563 byjoe@... on April 12, 2007, 9:35 a.m.
Member since 2022-08-22
> My multilayered approach is more appropriate for smaller and earlier
> space colonies in which the mass is just not there yet, and for
> spaceships in which it is necessary to keep the mass down.
issue. If the Polywell reactor pans out, we will have plenty of energy
available, so an EM shield might make sense in that case.
For space colonies, though, I think even the early ones will find it
cheapest to just dump a few meters of soil (probably based on lunar
regolith) on the ground deck. If you don't have that, then you're
going to have a hard time growing trees, anchoring flagpoles, etc. And
don't even get me started on an external non-rotating radiation shield.
;)
> Your soil shield is a good idea, but we are still going to need a
> water tank beneath the soil and it could be metal lined with plastic.
> For simplicity we may just go with a porous gravel layer below the
> soil for an aquifer.
I like the idea of an aquifer, but -- why do we need it? I feel I've
missed your point here.
> The soil shield will only work on the outside/bottom of a spinning
> colony. For maximum surface area, I envisioned a long cylinder like
> the alien whale probe in Star Trek IV (Save The Whales). However, it
> was pointed out in another thread that this design is inherently
> unstable, as a long cylinder will tend to spin end-over-end like a
> cheerleader's baton.
Right. I much preferred that geometry too (I even have some fairly
detailed designs of a colony based on it), but alas, it doesn't seem
workable.
> I now envision a double-hulled colony consisting of a cylinder
> containing several spheres. ...
> The cylinder rotates around Shuttle Bay Sphere 0 at a rate that
> simulates 1 gee in Spheres 5a&b. Spheres 3a&b would be at about 1/3
> gee (Martian). Spheres 2a&b would be at about 1/6 gee (Lunar).
> Spheres 1 & 4 are optional.
So this is basically a multi-deck baton design. (What's neat is that
my earlier cylinder design, mentioned above, was also multi-deck, with
a "Martian" and "lunar" deck plus a couple others. That one spun
around its long axis though, which we now know is unstable, unlike
yours.)
I'm not sure I see the point of the spheres, though -- why not just put
in flat decks? Those would be simpler and provide slightly more living
area.
Anyway, you're quite right that in a baton design, soil doesn't help
much with the shielding problem, since most of the radiation would be
coming in from the side. In that case you do need some other strategy
(or combination thereof).
Best,
- Joe
Joe Strout -- joe@...
# 21564 byGARY ANSORGE on April 12, 2007, 10:56 a.m.
Member since 2022-08-22
I just read the Wikipedia dedscription of the Polywell
reactor design. I had read the excerpt of Dr. Bussards
talk at Google, but missed the important reference to
the electron trapping at the reactor core. Wikipedia
did a really good job clarifying that concept. Dang,
if I only had a couple of million to invest,,,
High Frontier or he would already know the answer to
most of his tirades. I regularly read the Bad
Astronomer Blog and love Phil Plaits efforts to debunk
pseudoscience. It's been a life time endeavor on his
part. Now he has a new book in the works, titled Death
from the Skies, that should go a long way toward
showing just how foolish some of these doomsday
scenarios are. I point this out just to note SSI isn't
alone in trying to wake people to REAL world
possibilities.
I'm trying to figure out a way to show some of my
design ideas for Colonies. They're very clear in my
mind, but I have a hard time converting those internal
images into the real world, having little skill at
technical drawing. I asked my son to check out the
availability of design/graphic software to assist me
in this regard, but he hasn't got back to me yet. I
may just have to get down and dirty, drawing the
colonies on drafting paper, photographing the
resulting images and uploading to my computer. I hope
I can accomplish this in some reasonable time and
upload the images,then I hope SSI can provide some
critical input. Maybe from such critical analyses I
can develop some real designs that would work,,,
GAry 7
# 21565 byjoe@... on April 12, 2007, 11:39 a.m.
Member since 2022-08-22
> I just read the Wikipedia dedscription of the Polywell
> reactor design. I had read the excerpt of Dr. Bussards
> talk at Google, but missed the important reference to
> the electron trapping at the reactor core. Wikipedia
> did a really good job clarifying that concept. Dang,
> if I only had a couple of million to invest,,,
this concept (including the original papers from 1991-92) and I've
grown convinced that he's on to something important. But there isn't
much I can do except cheer from the sidelines, and gather resources
like this:
http://www.strout.net/info/science/polywell/>
> Joe, I expect Nicklas hasn't even read Dr. O'Neill's
> High Frontier or he would already know the answer to
> most of his tirades.
Agreed -- as far as I can tell, he hasn't read anything related to
space development at all. But we've already pointed out several
resources for him; maybe he'll spend the summer catching up.
> I regularly read the Bad
> Astronomer Blog and love Phil Plaits efforts to debunk
> pseudoscience. It's been a life time endeavor on his
> part. Now he has a new book in the works, titled Death
> from the Skies, that should go a long way toward
> showing just how foolish some of these doomsday
> scenarios are. I point this out just to note SSI isn't
> alone in trying to wake people to REAL world
> possibilities.
It's an ongoing battle. :) I know of that blog but haven't read it
too often; thanks for pointing it out.
> I'm trying to figure out a way to show some of my
> design ideas for Colonies. They're very clear in my
> mind, but I have a hard time converting those internal
> images into the real world, having little skill at
> technical drawing.
I find just a good drawing program (on the Mac, I prefer OmniGraffle)
makes it pretty easy to make a clear "blueprint" style drawing. For
real visualization, like this
http://www.strout.net/info/science/settlements/>, you have to work
harder of course. But on the other hand, images like that are made (in
POV-Ray) entirely with math and simple code -- you don't really need an
artistic hand. So maybe that would suit you.
> I hope
> I can accomplish this in some reasonable time and
> upload the images,then I hope SSI can provide some
> critical input. Maybe from such critical analyses I
> can develop some real designs that would work,,,
I'd certainly enjoy kicking some ideas around with you, and I'm sure
others here would as well.
Best,
- Joe
Joe Strout -- joe@...
# 21566 byEd Minchau on April 12, 2007, 1:09 p.m.
Member since 2022-08-22
I have to agree about using a drawing program like
POV-Ray, one can do rather a lot with that (or Moray,
or 3D Canvas, or any of a myriad of other such
programs).
it looks pretty good. I was thinking that if the
mirror was missing 1/3 of its reflective surface -
that is, a 120 degree wedge removed, replaced by an
equivalent counterweight - then if the station rotates
1440 times every 24 hours, the mirror could rotate
1439 or 1441 times in 24 hours. Thus, every window
would have light shining in for 16 hours, and darkness
for 8 hours, with the dark portion slowly migrating
around the torus once every 24 hours.
One might also want to extend the "spike" portion of
the hub out to the axis of rotation of the mirror,
which would rotate on magnetic bearings - that's my
first guess as to how to keep the mirror in a fixed
position relative to the station, as otherwise over
time the masses of the station and mirror would
gravitationally attract.
Ed
# 21567 byjoe@... on April 12, 2007, 2:07 p.m.
Member since 2022-08-22
> Joe, I took a look at the design you have there, and
> it looks pretty good.
Best,
- Joe
Joe Strout -- joe@...
# 21568 byJolly Roger on April 14, 2007, 4:08 p.m.
Member since 2022-08-22
> I like the idea of an aquifer, but -- why do we need it? I feel I've
> missed your point here.
animals need liquid water. Liquid water requires storage. An aquifer
is the simplest water storage method, and also provides filtration.
Also, many tree species have a long tap root, and a aquifer would give
them a little more room before hitting bedrock (concrete). Besides,
the question is not why we need an aquifer, but how we would avoid
one. It would form naturally at the bottom of the soil anyway.
> > I now envision a double-hulled colony consisting of a cylinder
> > containing several spheres. ...
> So this is basically a multi-deck baton design.
> I'm not sure I see the point of the spheres, though -- why not just
put
> in flat decks? Those would be simpler and provide slightly more
living
> area.
I also thought about flat decks. I got a mental picture of the
skyscraper in "Volcano" that Tommy Lee Jones dropped in front of the
lava. Spin something like that end-over-end.
But I wanted this to be a double-hull design with each deck able to
handle depressurization of the outer hull. A sphere is the strongest
shape with the minimum of materials and encloses the most volume. The
upper half provides an open "sky" and the lower half has enough room
for infrastructure below the soil and aquifer.
I was inspired by Harlan Ellison's "The Starlost" and "Silent Running"
(w/Bruce Dern). I would consider lenticular or semi-lenticular domes
instead of spheres.
I also wanted the decks to be independent so that a rupture of a
sidewall and deck would compromise only one deck, not two.
;-)X
# 21569 byJolly Roger on April 14, 2007, 4:38 p.m.
Member since 2022-08-22
The simplest variant of my sphere/cylinder idea would be two spheres
and no external cylinder, just a tether or access tube. That would
basically be the barbell that someone previously mentioned. I guess
that would be an old-fashioned circus barbell!
What happened to the wheel-shaped space station, a la "2001: A Space
Odyssey"? Is it unstable? Would it tend to tumble? Would a disc
also be unstable and tumble?
# 21570 byjoe@... on April 15, 2007, 3:44 p.m.
Member since 2022-08-22
> The simplest variant of my sphere/cylinder idea would be two spheres
> and no external cylinder, just a tether or access tube. That would
> basically be the barbell that someone previously mentioned. I guess
> that would be an old-fashioned circus barbell!
station than a colony I'd say). A variant of this is to have a habitat
in only one end, and some other heavy mass (the power plant, etc.) at
the other.
> What happened to the wheel-shaped space station, a la "2001: A Space
> Odyssey"? Is it unstable? Would it tend to tumble?
No, a wheel or torus is perfectly stable.
> Would a disc also be unstable and tumble?
Discs are fine too. If you want an intuition for it, imagine that the
greatest mass of the station "wants" to spin slowly around the largest
path it can. So in a cylinder, that'd be spinning end over end, rather
than around the long axis. But in a torus or disc, it'd be spinning
around the short central axis.
Best,
- Joe
Joe Strout -- joe@...
# 21571 byJolly Roger on April 16, 2007, 9:27 a.m.
Member since 2022-08-22
Joe,
get into instability problems is roughly when the thickness of the
disc is equal to the diameter. If we keep the thickness down to, say,
the same as the radius, we should be okay. We still have to keep the
mass loads balanced around the outside of the disc.
I am beginning to see where you are coming from with your torus
model. The path of two spheres rotating around a common center of
mass describes a torus. If I take my cylinder full of spheres, bend
it around and connect the ends, I get a hollow torus containing
spheres.
You may ask, "Why retain the spheres? Why not go with flat vertical
bulkheads?" That might be fine for a smaller space station of less
than 100 meters torus thickness, but for a colony larger than one
kilometer thickness we need curvature on the pressure bulkheads. A
sphere is the ultimate curvature.
There can be multiple decks within each spherical pressure vessel, and
and also in the spaces between them. A ring of smaller spheres may be
built in the gaps between the larger spheres.
We may not be on the same page, but I think I am now in the same
chapter.
> ... a wheel or torus is perfectly stable. ... Discs are fine too.
If you want an intuition for it, imagine that the
> greatest mass of the station "wants" to spin slowly around the
largest
> path it can. So in a cylinder, that'd be spinning end over end,
rather
# 21572 byjoe@... on April 16, 2007, 10:49 a.m.
Member since 2022-08-22
> Thanks for the explanation. I take it then that the point we start to
> get into instability problems is roughly when the thickness of the
> disc is equal to the diameter.
the situation. A disc implies flat endcaps, which are about as good as
you can get (except maybe concave ones!), and in that case, you need to
keep the cylinder length (i.e. thickness, if you're thinking of it as a
disc) to 1.3 times the radius or less.
> If we keep the thickness down to, say,
> the same as the radius, we should be okay.
Yes, that'd be length = 1.0 r, which is fine.
> I am beginning to see where you are coming from with your torus
> model.
Well, Stanford's torus model, yes. :) All I did was render it.
> If I take my cylinder full of spheres, bend
> it around and connect the ends, I get a hollow torus containing
> spheres.
True.
> You may ask, "Why retain the spheres? Why not go with flat vertical
> bulkheads?" That might be fine for a smaller space station of less
> than 100 meters torus thickness, but for a colony larger than one
> kilometer thickness we need curvature on the pressure bulkheads. A
> sphere is the ultimate curvature.
I think you're overestimating the importance of that. Containing 1
atmosphere of pressure isn't all that hard -- spacecraft do it all the
time. The Apollo spacecraft did it with walls not much thicker than
aluminum foil in some places, IIRC.
Granted, on a larger scale it's more difficult, but not all that much
more. A torus is a good shape for containing pressure -- like at a
bicycle tire for an example.
Best,
- Joe
Joe Strout -- joe@...
# 21573 byEd Minchau on April 16, 2007, 4:32 p.m.
Member since 2022-08-22
> You may ask, "Why retain the spheres? Why not go
> with flat vertical
> bulkheads?" That might be fine for a smaller space
> station of less
> than 100 meters torus thickness, but for a colony
> larger than one
> kilometer thickness we need curvature on the
> pressure bulkheads. A
> sphere is the ultimate curvature.
>
surfaces anywhere.
Ed
# 21574 byJolly Roger on April 17, 2007, 8:21 a.m.
Member since 2022-08-22
>
> > ... for a colony
> > larger than one
> > kilometer thickness we need curvature on the
> > pressure bulkheads.> >
>
> Roger, a torus is already a curved hull - no flat
> surfaces anywhere.
>
Ed,
smaller sections so that if the outer hull is punctured only a small
part is depressurized, not the whole volume. The shape of a bulkhead
is a flat circle.
Thanks, Joe, for pointing out that the bulkheads need not be very
massive. Transparent plastic sheeting a few mils thick (visquene)
will do just fine.
My naval experience taught me that compartmentation and double-hull
construction are good safety factors to incorporate into a space
colony. I just forgot that water is a much denser fluid than air, and
building to withstand high pressure is just overkill in space.
For this reason I withdraw my sphere design.