--- In , "Combs, Mike" wrote:

> From: Michael Capriola:

>> And the reason we can't say for sure what happens at 3 rpm or 2
>> rpm is that we haven't tested it.

> Well, let's say we haven't tested it in space. There have been
> Earthbound experiments. The question is to what extent the
> experimental results we get here on Earth would apply in space.
>
> Personally, I can't help but wonder if we'll find that adapting to
> spin in space is easier than on Earth. On Earth, gravity is an
> additional force acting on the inner ear. In space, that'd be one
> less force to complicate things.
>
> Regards,
>
> Mike Combs

Let's design the experiment that lets people be Human Space Guinea
Pigs, and see what happens at full-G, but 5 rpm, or 4, or 3, or 2 or
1 rmp. Let's come up with something that NASA, the Russians, or even
some non-governmental group could do to answer these questions.

And not only these, but other questions could be answered as well.
For instance, we all seem to assume that spending large amounts of
time in full gravity will allow us to stay in space indefinitly, even
if we do most of our work and some of our play in low- or zero-G. Is
that true? These experiments could answer this.

It needs to be cheap (building a full-fledged habitat is out for
now). It needs to be easy (no bucky nanotubes, diamondoid, etc.).
It needs to be soon (no waiting for a new launch vehicle or those
afore-mentioned nanotubes, etc.).

I propose the No-Prize!(*) We should come up with three ideas, each
more expensive than the other.

1) The first is something that could be done with a single dedicated
Shuttle launch, and should cost less than a billion (counting the
Shuttle launch itself).

2) The second should be something that could be done with two, maybe
three dedicated Shuttle launches, and costs less than 3 billion
(counting the Shuttle launches themselves).

3) The third would be something that takes a few of years before the
first chunk of hardware is launched, take a few years to assemble,
and costs up to 6 billion (counting the Shuttle launches themselves).

Xenophile

(*) because no matter how good a job you do, you get no prize!

From: Xenophile [mailto:xenophile2002@...]

> Let's design the experiment that lets people be Human Space Guinea
> Pigs, and see what happens at full-G, but 5 rpm, or 4, or 3, or 2 or
> 1 rmp. Let's come up with something that NASA, the Russians, or even
> some non-governmental group could do to answer these questions.

Yes, I'd like to see that (I don't think the Mars Society is going to
get that spinning capsule with the mice up, which is a shame). I'd like
to see a system where we start out at a rotation rate producing 1/6th of
a G, and leave an astronaut there for 6 months or more. Then change
crew and increase rotation rate to 1/3rd of a G. Then a full 1 G. At
the same time we accumulate data on what long-term exposure to lunar and
Martian gravity levels would be like, we get data on increasing RPMs.
Should be all things to all people.

> It needs to be cheap (building a full-fledged habitat is out for
> now). It needs to be easy (no bucky nanotubes, diamondoid, etc.).
> It needs to be soon (no waiting for a new launch vehicle or those
> afore-mentioned nanotubes, etc.).

I once went through the mental exercise of trying to design the simplest
experiment one could perform. It was surprising how quickly the
complexity went up when you factor in power, life-support, heat
rejection, etc. It's hard to design a facility that's any less
complicated than a full-up multi-purpose space station facility.

Regards,

Mike Combs

Hello, everyone... I'm Dave. I just joined this list, but I see a few names
I recognize from some other space-related lists, so I'm just going to dive
off into the deep end of the pool, into the middle of an existing thread. ;)
Two questions...

From: Xenophile [mailto:xenophile2002@...]

> Let's design the experiment that lets people be Human Space Guinea
> Pigs, and see what happens at full-G, but 5 rpm, or 4, or 3, or 2 or
> 1 rmp. Let's come up with something that NASA, the Russians, or even
> some non-governmental group could do to answer these questions.

There were studies at the U.S. Naval Medical Center, at Pensacola, Florida,
and at the Soviet ORBIT centrifuge facility, in the `60s/`70s. Other tests
were being examined as late as July of this year. I'm certainly not claiming
those tests were all-inclusive, but is there something specific, beyond
those studies, that you're looking for?

From: Combs, Mike [mailto:mikecombs@...]

I'd like to see a system where we start out at a rotation rate producing
1/6th of a G, and leave an astronaut there for 6 months or more. Then
change crew and increase rotation rate to 1/3rd of a G.

This is a great idea, if we assume there's anything worth spending our time
on with either the Moon *or* Mars. But so far, the best information I've
seen says we need to aim for the NEOs, and either build the classic,
`constructed' O'Neill's, or hollow out asteroids. Why spend all the effort
to break free of Earth's gravity well, just to dump ourselves back down in
another one?

Dave
"Is a planetary surface the right place for an expanding technological
civilization?" Dr. Gerard K. O'Neill

Hi Dave, have you read the book "Mining The Sky" by JOHN S. LEWIS -
Perseus Books. It contains some quite interesting reasons for going to
the Moon and Mars. On the Moon we might build Lunar solar power
stations and process the regolith for helium-3 to use as a fuel in
fusion reactors and on Mars we could build a very interesting device
called a sky hook which would turn Mars into a very important base for
the exploration and exploitation of the asteroid belt and the outer
solar system.

Regards, David

--- In spacesettlers@yahoogroups.com, "Dave Logsdon"
> Hello, everyone... I'm Dave. I just joined this list, but I see a
few names
> I recognize from some other space-related lists, so I'm just going
to dive
> off into the deep end of the pool, into the middle of an existing
thread. ;)
> Two questions...
>
> From: Xenophile [mailto:xenophile2002@y...]
>
> > Let's design the experiment that lets people be Human Space Guinea
> > Pigs, and see what happens at full-G, but 5 rpm, or 4, or 3, or 2 or
> > 1 rmp. Let's come up with something that NASA, the Russians, or even
> > some non-governmental group could do to answer these questions.
>
> There were studies at the U.S. Naval Medical Center, at Pensacola,
Florida,
> and at the Soviet ORBIT centrifuge facility, in the `60s/`70s. Other
tests
> were being examined as late as July of this year. I'm certainly not
claiming
> those tests were all-inclusive, but is there something specific, beyond
> those studies, that you're looking for?
>
> From: Combs, Mike [mailto:mikecombs@t...]
>
> I'd like to see a system where we start out at a rotation rate producing
> 1/6th of a G, and leave an astronaut there for 6 months or more. Then
> change crew and increase rotation rate to 1/3rd of a G.
>
> This is a great idea, if we assume there's anything worth spending
our time
> on with either the Moon *or* Mars. But so far, the best information I've
> seen says we need to aim for the NEOs, and either build the classic,
> `constructed' O'Neill's, or hollow out asteroids. Why spend all the
effort
> to break free of Earth's gravity well, just to dump ourselves back
down in

--- In spacesettlers@yahoogroups.com, "sardonius2000"
wrote:
>
> Hi Dave, have you read the book "Mining The Sky" by JOHN S. LEWIS -
> Perseus Books. It contains some quite interesting reasons for going to
> the Moon and Mars. On the Moon we might build Lunar solar power
> stations and process the regolith for helium-3 to use as a fuel in
> fusion reactors and on Mars we could build a very interesting device
> called a sky hook which would turn Mars into a very important base for
> the exploration and exploitation of the asteroid belt and the outer
> solar system.
>
> Regards, David

If you compare Lunar Solar Power to SPS, SPS wins hands down. Beaming
from GEO to a fixed earth-based rectenna is much simpler than beaming
from a rotating moon across 250,000 miles to a rotating earth and
having to contend with the angle of the beam shifting with the
rotations, night on the moon (2 weeks) and "dark side" on earth. Now
you're introducing beam coherence issues, GEO reflectors, and much
more complexity.

Andrew already posted his thoughts on the problems of He-3 fusion,
beyond it not being possible at this time. Search the archive for details.

Why go to Mars and build a skyhook in order to explore the asteroids?
This sounds like it comes straight from Robinson's RED MARS. What is
the provenance of this idea, for it should be put out of its misery,
tout suite.

Lewis is aware of O'Neill's work, but most likely didn't want to take
up the battle of planetary chauvinism, for The High Frontier covers
the issues in depth, so he appealed to the planetary chauvinists, but
that doesn't mean any of these three ideas is really feasable.

TangoMan

Hi Tangoman, I don't think you can say SPS beats LSPS hands down, SPS
might be more efficient and less complicated but it will be far
cheaper to build solar panels out of available lunar materials than to
transport those materials from the Moon (with a mass driver) or an NEO
to an SPS construction site. If you've got any definitive data which
proves SPS is superior to LSPS I'd very much like to read it.

I've got to admit that I didn't research Helium-3 Fusion, I just took
it for granted Lewis knew what he was talking about but I'll check out
the posting you mentioned.

As for going to Mars, It looks like a nice place to visit but I'm not
sure I'd want to live there, however there do seem to be rather a lot
of Mars nuts who do. Building domes on Mars would be a lot cheaper
than space habitats. And if the sky hook is practicle it will
undoubtedly be built. And yes I do seem to remember the sky hook idea
from Robinsons Mars trilogy, I think he called it the Mars elevator,
but it was Konstantin Tsiolkovskii who first thought of it in 1895.

I think you're being a little unfair to Lewis as regards planetary
chauvinism, I didn't get that from the book at all. Lewis speaks of
quadrillions of people inhabiting the solar system and I know he
didn't think they'd all be living on Mars. If Lewis doesn't go into
detail about space habitats its because he thought the subject had
already been covered by O'Neil and Happenheimer.

Regards, David

> > solar system.
> >
> > Regards, David
>
> If you compare Lunar Solar Power to SPS, SPS wins hands down. Beaming
> from GEO to a fixed earth-based rectenna is much simpler than beaming
> from a rotating moon across 250,000 miles to a rotating earth and
> having to contend with the angle of the beam shifting with the
> rotations, night on the moon (2 weeks) and "dark side" on earth. Now
> you're introducing beam coherence issues, GEO reflectors, and much
> more complexity.
>
> Andrew already posted his thoughts on the problems of He-3 fusion,
> beyond it not being possible at this time. Search the archive for
details.

From: sardonius2000 [mailto:sardonius2000@netscape.net]

"Hi Tangoman, I don't think you can say SPS beats LSPS hands down, SPS
might be more efficient and less complicated but it will be far cheaper
to build solar panels out of available lunar materials than to transport
those materials from the Moon (with a mass driver) or an NEO to an SPS
construction site. If you've got any definitive data which proves SPS is
superior to LSPS I'd very much like to read it."

It's true the issue very much turns on transportation costs for lifting
lunar materials up to HEO. But personally, my bets are still on
lunar-derived SPS in GEO. I just can't see how power plants which are
only operational half the time can compete economically with ones
operating 99% of the time, even if they are cheaper to build. The
construction cost is a one-time expense. The 50% duty cycle is an
ongoing disadvantage for the life of the power plant.

"Building domes on Mars would be a lot cheaper than space habitats."

Are you sure? This is majority thinking, but it could simply be a bias.
I talk about that a bit here:
http://members.aol.com/howiecombs/somewhere_else.htm

"And if the sky hook is practicle it will undoubtedly be built."

It can't be denied that a skyhook would be an easier proposition for
Mars than for Earth. Which is a darn shame since Earth is where we
presently sit.

I think the notion that a Mars skyhook will be invaluable to Belt
development and exploration of the outer system proceeds from an
assumption that humans can only be properly supported on planetary
surfaces. So the notion goes that a Mars skyhook combines the planetary
surface with the ease of access to space. But I think the best solution
of all to planetary gravity wells is to not get into them in the first
place. I'm convinced that the people who will develop the Belt will not
commute but live there, and call it home.

Regards,

Mike Combs

From: sardonius2000 [mailto:sardonius2000@...]

"Hi Dave, have you read the book "Mining The Sky" by JOHN S. LEWIS"

One of my favourite books! But my take on it, and everything else Lewis has
written, is that if you look at the best, most optimistic examples of what
we could do with the Moon, or Mars, the NEOs are still, by far, the best
choice.

"On the Moon we might build Lunar solar power stations ..."

Which, as Lewis points out, will only work half the time. 14 Earth-days of
light, followed by another 14 Earth-days of dark, no matter what part of the
Moon you put the solar panels on.

Unless you're referring to Solar Power Satellites (SPS), put into GEO? In
that case, the NEOs still provide a far greater variety of materials to work
with, and avoid the penalty of boosting the materials out of a major gravity
well.

"and process the regolith for helium-3 to use as a fuel in fusion reactors"

Which no one has ever created yet, and no one knows how long it'll take to
do so. *IF* (and it's still a really big *IF*) someone ever gets some sort
of affordable fusion system going, we can re-visit the issue. If that ever
happens, the He3 in the regolith might be one of the most valuable things we
know of. Until then, it's worthless.

"and on Mars we could build a very interesting device called a sky hook"

Some folks use the term "skyhook" to refer to a `space elevator', attached
to the surface. Some others refer to a spinning tether. Either way, it can
be used on/near the Earth; we don't have to go to Mars to do it. Look at the
work of Dr. Bradley Edwards. Read his book, `The Space Elevator'. Or, you
can check out the various YahooGroups discussing either topic. Mars is
actually more difficult to use *either* plan on, because of the very low
orbit of it's `moons'.

Whether we get into space via a `space elevator', a RLV, or any combination,
the resources of Mars, and/or the Main Belt asteroids, could be centuries
away. The Moon, so far, doesn't offer anything we can use. The NEOs can
provide all we could possibly use for generations.

Dave
"Is a planetary surface the right place for an expanding technological
civilization?" Dr. Gerard K. O'Neill

From: Dave Logsdon [mailto:templar@...]

"This is a great idea, if we assume there's anything worth spending our
time on with either the Moon *or* Mars. But so far, the best information
I've seen says we need to aim for the NEOs, and either build the
classic, `constructed' O'Neill's, or hollow out asteroids. Why spend all
the effort to break free of Earth's gravity well, just to dump ourselves
back down in another one?"

Oh, believe me, you're preaching to the choir here. :) I only bring it
up to make the point that an experiment which seems to also offer
something up to the moon and Mars enthusiasts out there might see
broader support across the space advocacy community than one which only
seems to offer something to the O'Neillians.

Another point is that for any design with a fixed diameter, starting out
with smaller rotation rates and then incrementally working your way up
to greater ones would by necessity start out with lower G values and
incrementally work up to larger ones.

Regards,

Mike Combs

Hi Dave, It would have been nice if you'd left a reference to the post
I was replying to. In my reply to your comments I was essentially
trying to act as devils advocate by suggesting a few possible uses for
the Moon and Mars which I thought you were dismissing a bit too
quickly. I happen to agree with you that NEO's are probably the way to
go as far as construction of SPS and space habitats go but there still
seem to be many questions unresolved.

What's the timetable for NEO exploitation?

How long would a round trip to an NEO take?

How much could you bring back in one trip?

How many ships will you need?

Where will the ships be built and out of what?

And how does the cost of Asteroid mining compare to O'Neill's scheme
for launching the materials from the Moon with a mass driver. I know
in the long run Asteroid mining will win out but can we really do it
without using the Moon as a springboard?

As far as LSPS goes, I'm not wedded to the concept but I'd really like
to see a cost comparison before I dismiss the idea. The fact that half
the LSPS is in darkness at any one time is irrelevant if the price is
right.

I have to admit to being very new to most of these ideas so perhaps
someone can put me out of my misery on this, would it be possible to
illuminate just one string of LSPS with a lunar orbital mirror?

As far as Mars and the Asteroid belt being out of reach for centuries
is concerned, all I can say is that we can't know that. We can't
predict the future, perhaps people will choose to go sooner to get
away from Earth or more correctly Earth's wretched governments, or
maybe just for the hell of it. If people do choose to go to Mars it
will be in thier interests to build a skyhook.

Lewis does suggest a solution to the problem of the orbits of Phobos
and Deimos, he suggests moving them to MSO to serve as an MSO platform
and a source of construction materials for the Mars skyhook.

Thanks for the heads up on "The Space Elevator", I haven't been able
to track down a coppy yet but I will do in the next couple of days.

Just for the record I'm not a proponent of settleing Mars or any
planetary surface but I still think it's a strong possibility that
others will choose to do so and that discussion of such subjects
remains relevant.

If you haven't read the other posts you probably don't know that
Tangoman already picked me up on the viability of Helium-3 fusion.

Regards to all, David

--- In spacesettlers@yahoogroups.com, "Dave Logsdon" wrote:
> From: sardonius2000 [mailto:sardonius2000@n...]
>
> "Hi Dave, have you read the book "Mining The Sky" by JOHN S. LEWIS"
>
> One of my favourite books! But my take on it, and everything else
Lewis has
> written, is that if you look at the best, most optimistic examples
of what
> we could do with the Moon, or Mars, the NEOs are still, by far, the best
> choice.
>
> "On the Moon we might build Lunar solar power stations ..."
>
> Which, as Lewis points out, will only work half the time. 14
Earth-days of
> light, followed by another 14 Earth-days of dark, no matter what
part of the
> Moon you put the solar panels on.
>
> Unless you're referring to Solar Power Satellites (SPS), put into
GEO? In
> that case, the NEOs still provide a far greater variety of materials
to work
> with, and avoid the penalty of boosting the materials out of a major
gravity
> well.
>
> "and process the regolith for helium-3 to use as a fuel in fusion
reactors"
>
> Which no one has ever created yet, and no one knows how long it'll
take to
> do so. *IF* (and it's still a really big *IF*) someone ever gets
some sort
> of affordable fusion system going, we can re-visit the issue. If
that ever
> happens, the He3 in the regolith might be one of the most valuable
things we
> know of. Until then, it's worthless.
>
> "and on Mars we could build a very interesting device called a sky
hook"
>
> Some folks use the term "skyhook" to refer to a `space elevator',
attached
> to the surface. Some others refer to a spinning tether. Either way,
it can
> be used on/near the Earth; we don't have to go to Mars to do it.
Look at the
> work of Dr. Bradley Edwards. Read his book, `The Space Elevator'.
Or, you
> can check out the various YahooGroups discussing either topic. Mars is
> actually more difficult to use *either* plan on, because of the very low
> orbit of it's `moons'.
>
> Whether we get into space via a `space elevator', a RLV, or any
combination,
> the resources of Mars, and/or the Main Belt asteroids, could be
centuries

--- In spacesettlers@yahoogroups.com, "sardonius2000"
wrote:

> How long would a round trip to an NEO take?

What are your variables? What ISP does your propulsion put out? Are
you hauling your own return fuel? ARe you hauling equipment out and
deadheading back? Are you bringing back material? etc.

> How much could you bring back in one trip?

In broad brushstrokes, there are basically two ways to go about this.

1.) Bring the whole asteroid back to cislunar space; and
2a.) Bring back ore
2ai) Take your equipment out and refine there
2b.) Bring back chunks of the NEO.

> How many ships will you need?

What I favor is to send out on a low energy orbit a high mass refinery
and then months to years later launch a high delta-v crew vehicle to
rendevouz at the NEO with the refinery and set things up. Then the
crew returns and automated packages are launched back to cislunar
space. Replenishment of the automated ore delivery vehicles takes
place on a regular basis.

> Where will the ships be built and out of what?

TangoMan Orbital Shipyards, of course. The first ones will be entirely
Earth sourced because we have absolutely no industrial infrastructure
in orbit.

> And how does the cost of Asteroid mining compare to O'Neill's scheme
> for launching the materials from the Moon with a mass driver. I know
> in the long run Asteroid mining will win out but can we really do it
> without using the Moon as a springboard?

I don't think so because you need to factor in the cost of capital. To
go to an NEO you'll need to factor in a few year supply line and your
money isn't earning a return during the voyage out. Secondly, if you
need to modify your supply line from the moon you only have a few days
of raw material in the transit pipeline. From an NEO you could have a
lag of months to contend with. Let's say you have a storage problem or
a lack of fuel for your capture vehicles, or whatever, and you have
these payloads arriving and can't accomodate them. Think of trying to
stop a pipeline with a band-aid. Most likely the payloads won't have
on-board propulsion because that means you need to equip each vehicle
with rockets and fuel and you need to transport them to the NEO so
that they can ferry material back to cislunar space. Quite redundent.

> As far as LSPS goes, I'm not wedded to the concept but I'd really
> like to see a cost comparison before I dismiss the idea. The fact
> that half the LSPS is in darkness at any one time is irrelevant if
> the price is right.

True, but the complexity of the scheme is, IMHO, it's glaring flaw.

With SPS at GEO the rectenna farm has a fixed point in the sky to
align to. With the Lunar system you have to contend with the Earth's
rotation and the moon's rotation. One station on the moon can beam to
a rectenna farm for at best 12 hours per day (due to Earth's rotation)
14 days out of 28 (due to moon's rotation). Further, you need to have
orbital reflectors at GEO to redirect the Lunar beams down to the
Earth rectenna. Where will these HUGE reflectors come from?

There are a host of other infrastructure issues about the lunar
scheme, which when solved also support the SPS scheme, so all of the
advantages of lunar power seem to vanish.

> I have to admit to being very new to most of these ideas so perhaps
> someone can put me out of my misery on this, would it be possible to
> illuminate just one string of LSPS with a lunar orbital mirror?

Nope.

> As far as Mars and the Asteroid belt being out of reach for centuries
> is concerned, all I can say is that we can't know that. We can't
> predict the future, perhaps people will choose to go sooner to get
> away from Earth or more correctly Earth's wretched governments, or
> maybe just for the hell of it. If people do choose to go to Mars it
> will be in thier interests to build a skyhook.

Who'll pay for that massive project and WHY?

> Lewis does suggest a solution to the problem of the orbits of Phobos
> and Deimos, he suggests moving them to MSO to serve as an MSO
> platform and a source of construction materials for the Mars
> skyhook.

If you're willing to go to the trouble of MOVING A MOON then surely
building orbital infrastructure in cislunar space will be a walk in
the park.

For a more comprehensive look at the process of industrializing space
look here for my thoughts and you can follow up on the discussion by
searching the archive for posts that follow this one that are on the
same theme (bootstrapping - step 1, step 2, step xx.)

Regulars will have already seen my Bootstrapping post (arghh, not
again, LOL :)

TangoMan

"sardonius2000" wrote:

"Just for the record I'm not a proponent of settleing Mars or any
planetary surface but I still think it's a strong possibility that
others will choose to do so and that discussion of such subjects
remains relevant."

There will always be people who look at a piece of real estate that no one
else wants and then say, "What can I do with this property? Can I make it
profitable?" Or, "No one will bother me if I go live there."

"Just for the record I'm not a proponent of settleing Mars or any
planetary surface but I still think it's a strong possibility that
others will choose to do so and that discussion of such subjects
remains relevant."

If Mars has water it certainly is worth settling. It has 0.4 Earth g; period of rotation is the same; solar illumination is enough for agriculture, even without intensifiers. I don't fully understand the objection to planetary surfaces as space habitats. What's wrong with Earth? Island type habs which we are discussing are also great.

Selvaraj

From: Michael Capriola
To: spacesettlers@yahoogroups.com
Sent: Wednesday, October 20, 2004 5:58 PM
Subject: [spacesettlers] RE: Spinning [WAS] Re: Island One, Two and Three

"sardonius2000" wrote:

"Just for the record I'm not a proponent of settleing Mars or any
planetary surface but I still think it's a strong possibility that
others will choose to do so and that discussion of such subjects
remains relevant."

There will always be people who look at a piece of real estate that no one
else wants and then say, "What can I do with this property? Can I make it
profitable?" Or, "No one will bother me if I go live there."

On Wed, 20 Oct 2004 22:50:10 +0530, sraj wrote:
> If Mars has water it certainly is worth settling.

Ahh! You positively *like* nuclear power!

> It has 0.4 Earth g; period of rotation is the same; solar illumination is enough for
> agriculture, even without intensifiers.

Quite possibly not. One of the things that failed in Biosphere II was
lack of light- the glass and support beams blocked out too much light,
as well as it being cloudy.

So, it isn't clear how well this really works. The only attempt to do
this, large scale on Earth failed.

Whilst it presumably won't be cloudy on Mars, the sun is only giving
half the sunlight to begin with, and the glass and support beams will
need to be very much thicker than Biosphere II to support 1 bar of
pressure difference.

Note that orbital habitats have similar problems in principle, however
they are likely to be closer to the Sun, above Earths atmosphere, and
they can position the beams to block less light as the habitat always
points directly towards the Sun.

> I don't fully understand the objection to planetary surfaces as space habitats.

It's more that they have advantages as well as disadvantages; and we
tend to forget the disadvantages.

The high escape velocity of Mars is a bad thing- exports to Earth are
going to be expensive from there, but exports to Earth from Earth
orbit and to Mars from Mars orbit are cheap. Exports to Earth from
Mars orbit are also going to be cheap.

Ultimately, exports tend to move money from the place being exported
to, from the place exported from. This seems to imply that Mars and
Earth are going to be poor in the very long term.

> Selvaraj

--
-Ian Woollard

"In theory there is no difference between theory and practice, but in
practice there is."
"a society in which people can do and say what they want will also
tend to be one in which the most efficient solutions win" - Paul
Graham

From: sraj [mailto:sraj@...]

> I don't fully understand the objection to planetary
> surfaces as space habitats. What's wrong with Earth?

http://members.aol.com/oscarcombs/spacsetl.htm#advantages

Regards,

Mike Combs

> As far as Mars and the Asteroid belt being out of reach for centuries
> is concerned, all I can say is that we can't know that.

I think this was in reference to a post of mine. I wasn't trying to say that
Mars and the Belt would be out of reach that long, but that the NEOs offer
enough resources that we won't *NEED* to go further for a long time. If the
NEOs are developed the way I, and a lot of other folks, think they should
be, I wouldn't be surprised to see somebody heading off to use the same tech
and start mining the Belt just a few decades later. As far as Mars is
concerned, you'll have to ask somebody who actually thinks we ought to
bother. You should know by now planets just ain't my thing...

Dave
"Is a planetary surface the right place for an expanding technological
civilization?" Dr. Gerard K. O'Neill