Especially if we're going to try and get by with an atmosphere only about
1/3 the density of Earth-normal.

You may well have uncovered yet another difficulty that the terraformers
tend to gloss over.

Regards,

Mike Combs

From: xenophile2002@... [mailto:xenophile2002@...]
Sent: Monday, July 16, 2001 2:40 AM
To: spacesettlers@yahoogroups.com
Subject: [spacesettlers] Not that I WANT to terraform Mars...

...but how would I go about giving the place a magnetic field? It
needs one, if people are to run around in the open.

You may well have uncovered yet another difficulty that the terraformers tend to gloss over.

Regards,
Mike Combs
From:
xenophile2002@... [mailto:xenophile2002@...]
Sent:
Monday, July 16, 2001 2:40 AM
To:
spacesettlers@yahoogroups.com
Subject:
[spacesettlers] Not that I WANT to terraform Mars...
...but how would I go about giving the place a magnetic field? It
needs one, if people are to run around in the open.

From:
To:
Sent: Monday, July 16, 2001 4:40 AM
Subject: [spacesettlers] Not that I WANT to terraform Mars...

> ...but how would I go about giving the place a magnetic field? It
> needs one, if people are to run around in the open.
>

Not exactly. The most megalomaniac terraforming plans involve dropping
comets in the Martian atmosphere instead of thickening it using local
materials only. So, using that method, you could made an atmosphere
arbitrarily thick, and block cosmic radiation with passive shielding only. A
planetary magnetic field would not be needed in that scenario.

Oh, I've just remembered that there is also a "partial terraformation" plan
that would involve vaporizing the soil (e.g., by using a giant concentrating
mirror in orbit) and dumping zillions of tons of carbon dioxide into the
atmosphere. Again, you would have a thick atmosphere made up of a greenhouse
gas. The planet would become a kind of hot, steamy planetary rainforest (or
so the terraformers hope), were plants and genetically engineered animal
could thrive, but where humans would have to use breathing masks.

Lucio Coelho

Just out of curiousity, is anyone aware of a large-engineering-project
working with a complex-poorly-understood-system where
small-scale-testing-was-impossible -- that worked the first time?

"Dr. Omni" wrote:
>
> From:
> To:
> Sent: Monday, July 16, 2001 4:40 AM
> Subject: [spacesettlers] Not that I WANT to terraform Mars...
>
> > ...but how would I go about giving the place a magnetic field? It
> > needs one, if people are to run around in the open.
> >
> Not exactly. The most megalomaniac terraforming plans involve dropping
> comets in the Martian atmosphere instead of thickening it using local
> materials only. So, using that method, you could made an atmosphere
> arbitrarily thick, and block cosmic radiation with passive shielding only. A
> planetary magnetic field would not be needed in that scenario.
>
> Oh, I've just remembered that there is also a "partial terraformation" plan
> that would involve vaporizing the soil (e.g., by using a giant concentrating
> mirror in orbit) and dumping zillions of tons of carbon dioxide into the
> atmosphere. Again, you would have a thick atmosphere made up of a greenhouse
> gas. The planet would become a kind of hot, steamy planetary rainforest (or
> so the terraformers hope), were plants and genetically engineered animal
> could thrive, but where humans would have to use breathing masks.
>
> Lucio Coelho
>

--
Al Globus
CSC
aglobus@..., (650) 604-4404
http://www.nas.nasa.gov/~globus/home.html

The dinosaurs weren't spacefaring. We are. I don't think that's an
accident. Maybe we are life's taxi to the stars.

From: "Combs, Mike"
To:
Sent: Monday, July 16, 2001 10:17 AM
Subject: RE: [spacesettlers] Not that I WANT to terraform Mars...

> Especially if we're going to try and get by with an atmosphere only about
> 1/3 the density of Earth-normal.
>

Uh, I've heard Martians talking about giving a 1/3 *bar* atmosphere to Mars.
That means an atmosphere exerting 1/3 of the atmospheric pressure of Earth
at sea level. Since the Martian gravity is around 1/3 g, then in fact you
would have to have a column of air with 10 metric tones of mass above each
square meter of the Martian surface - the same value on Earth. So, although
exerting less pressure, this atmosphere would provide as much passive
shielding as Earth's, because cosmic rays would have to pass through 10
tones of air in either planet. Or am I missing something?

> You may well have uncovered yet another difficulty that the terraformers
> tend to gloss over.
>

Even if the passive atmospheric shielding is really not enough, I think that
a terraformer could argue that a radioactive surface is not exactly an
unsolvable problem. People could live in underground houses and so get
exposed to cosmic rays only during brief periods of time (after all, most
people spend the vast majority of their time indoors). As for agriculture,
well, plants don't care about cosmic rays. However, I think that polar bears
and seals crawling over Mars, like K.S. Robinson imagined, would not be a
likely sight...

> Regards,
>

Regards,

> Mike Combs
[snikt]

Lucio Coelho

From: Dr. Omni [mailto:dromni@...]

Uh, I've heard Martians talking about giving a 1/3 *bar* atmosphere to Mars.
That means an atmosphere exerting 1/3 of the atmospheric pressure of Earth
at sea level. Since the Martian gravity is around 1/3 g, then in fact you
would have to have a column of air with 10 metric tones of mass above each
square meter of the Martian surface - the same value on Earth. So, although
exerting less pressure, this atmosphere would provide as much passive
shielding as Earth's, because cosmic rays would have to pass through 10
tones of air in either planet. Or am I missing something?

Ah. Thanks for making an important distinction here.

What I didn't appreciate until now was that when the Mars terraformers
proposed a 1/3 bar atmosphere for Mars, they were still having to talk about
making just as much air per square meter as covers the Earth. I'll bet many
Mars advocates, like myself, considered a 1/3 bar atmosphere for Mars an
easier proposition than it really is, mistakenly assuming much less air
would be needed.

It then seems to follow that in order to get a totally Earthlike Mars (one
where people can live out in the open and not just under Saran-wrapped
cities with greatly enhanced O2 percentages) will require around 3 times as
much air per square meter than is the case for Earth. Things keep getting
more difficult...

Even if the passive atmospheric shielding is really not enough, I think that
a terraformer could argue that a radioactive surface is not exactly an
unsolvable problem. People could live in underground houses and so get
exposed to cosmic rays only during brief periods of time (after all, most
people spend the vast majority of their time indoors).

If they did make this argument, I think it would be a very poor one. Living
underground even after terraformation is certainly not what most people are
visualizing when considering the concept.

Regards,

Mike Combs

From:
Dr. Omni [mailto:dromni@...]

Uh, I've heard Martians talking about giving a 1/3 *bar* atmosphere to Mars.
That means an atmosphere exerting 1/3 of the atmospheric pressure of Earth
at sea level. Since the Martian gravity is around 1/3 g, then in fact you
would have to have a column of air with 10 metric tones of mass above each
square meter of the Martian surface - the same value on Earth. So, although
exerting less pressure, this atmosphere would provide as much passive
shielding as Earth's, because cosmic rays would have to pass through 10
tones of air in either planet. Or am I missing something?

Ah. Thanks for making an important distinction here.

What I didn't appreciate until now was that when the Mars terraformers proposed a 1/3 bar atmosphere for Mars, they were still having to talk about making just as much air per square meter as covers the Earth. I'll bet many Mars advocates, like myself, considered a 1/3 bar atmosphere for Mars an easier proposition than it really is, mistakenly assuming much less air would be needed.

It then seems to follow that in order to get a totally Earthlike Mars (one where people can live out in the open and not just under Saran-wrapped cities with greatly enhanced O2 percentages) will require around 3 times as much air per square meter than is the case for Earth. Things keep getting more difficult...
Even if the passive atmospheric shielding is really not enough, I think that
a terraformer could argue that a radioactive surface is not exactly an
unsolvable problem. People could live in underground houses and so get
exposed to cosmic rays only during brief periods of time (after all, most
people spend the vast majority of their time indoors).

If they did make this argument, I think it would be a very poor one. Living underground even after terraformation is certainly not what most people are visualizing when considering the concept.

Regards,
Mike Combs

From: "Combs, Mike"
To:
Sent: Wednesday, July 18, 2001 6:07 PM
Subject: RE: [spacesettlers] Not that I WANT to terraform Mars...

[snikt]
> If they did make this argument, I think it would be a very poor one.
Living
> underground even after terraformation is certainly not what most people
are
> visualizing when considering the concept.
>

Yes, I agree - I realized that just after sending my previous message. I was
thinking with *my* head - the head of a wannabe space settler who does not
care if he will live in a spinning can or in a habitat buried in regolith,
as long as he is off-Earth. But then I remembered that the typical Zubrinite
wants to practice hiking in Olympus Mons and make marathons along the
Martian equator and appreciate the blood red sunset from his porch
everyday - stuff like that. ;-)

> Regards,
>

Regards,

> Mike Combs

Lucio Coelho

Yes, yes, but wasn't there something in here a month or so agao about
the solar wind doing nasty things to the atmosphere if you don't have
a magnetic field? And if we assume that one is needed (for whatever
reason), how do we go about putting it there?

--- In spacesettlers@y..., "Dr. Omni" wrote:
> From: "Combs, Mike"
> To:
> Sent: Wednesday, July 18, 2001 6:07 PM
> Subject: RE: [spacesettlers] Not that I WANT to terraform Mars...
>
> [snikt]
>> If they did make this argument, I think it would be a very poor
>> one.
>> Living underground even after terraformation is certainly not what
>> most people are visualizing when considering the concept.
>>
>
> Yes, I agree - I realized that just after sending my previous
> message. I was thinking with *my* head - the head of a wannabe
> space settler who does not care if he will live in a spinning can
> or in a habitat buried in regolith, as long as he is off-Earth.
> But then I remembered that the typical Zubrinite wants to practice
> hiking in Olympus Mons and make marathons along the Martian equator
> and appreciate the blood red sunset from his porch everyday - stuff
> like that. ;-)
>
> Regards,
>
> Lucio Coelho

Xenophile (who would rather live in an O'Neill cylindar -- made up to
look like ERB's Barsoom!)

For everyone who is not yet convinced the magnetic field is necessary
go to google or your favourite search engine and type von allen belt.

The von allen belts is the belts of cosmic rays that get trapped above
the atmosphere by the earth's magentic field and is disappiated at
the north and south pole.

The erath's magnetic field traps over 90% of the cosmic rays. With out
it the earth's atmosphere would have to be 10 times as thick.

--- In spacesettlers@y..., xenophile2002@y... wrote:
> Yes, yes, but wasn't there something in here a month or so agao
about
> the solar wind doing nasty things to the atmosphere if you don't
have
> a magnetic field? And if we assume that one is needed (for whatever
> reason), how do we go about putting it there?
>
> --- In spacesettlers@y..., "Dr. Omni" wrote:
> > From: "Combs, Mike"
> > To:
> > Sent: Wednesday, July 18, 2001 6:07 PM
> > Subject: RE: [spacesettlers] Not that I WANT to terraform Mars...
> >
> > [snikt]
> >> If they did make this argument, I think it would be a very poor
> >> one.
> >> Living underground even after terraformation is certainly not
what
> >> most people are visualizing when considering the concept.
> >>
> >
> > Yes, I agree - I realized that just after sending my previous
> > message. I was thinking with *my* head - the head of a wannabe
> > space settler who does not care if he will live in a spinning can
> > or in a habitat buried in regolith, as long as he is off-Earth.
> > But then I remembered that the typical Zubrinite wants to practice
> > hiking in Olympus Mons and make marathons along the Martian
equator
> > and appreciate the blood red sunset from his porch everyday -
stuff
> > like that. ;-)
> >
> > Regards,
> >
> > Lucio Coelho
>
> Xenophile (who would rather live in an O'Neill cylindar -- made up
to

From:
To:
Sent: Wednesday, July 18, 2001 11:25 PM
Subject: [spacesettlers] Re: Not that I WANT to terraform Mars...

Yes, yes, but wasn't there something in here a month or so agao about
the solar wind doing nasty things to the atmosphere if you don't have
a magnetic field? And if we assume that one is needed (for whatever
reason), how do we go about putting it there?
[snikt]

I remember that I heard somewhere that solar wind can "erode" an atmosphere.
However, I much doubt that this process is quick - my gut feeling is that it
would take millions of years for an atmosphere to be completely blown away
by the solar wind. And, since geological timescales are meaningless for
human civilizations, that would not be an unavoidable obstacle for a Mars
terraformation project - people would be content in living in a planet for
mere tens of thousands of years, which by the way is many times the whole
human history so far.

But okay, lets assume that, for some obscure reason, people could not live
in a planet without a magnetic field and the terraformers would have to
build one from scratch. Well, I am kind of short in wacky ideas right now,
but anyway it seems to me that a way to do that would be to build a gigantic
superconducting ring in orbit around the planet (perhaps Phobos and Deimos
could be consumed to do that, perhaps they would need a whole bunch of
asteroids, I don't know). This Ring of Power (sorry, I could not avoid a
reference to Tolkien ;-) could be powered by hundreds of solar power
stations connected to it, and then it would soon be teeming with a really,
really huge electric current. As a consequence, it would generate a magnetic
field of planetary scale. Since the ring would be superconducting, the
energy losses would be extremely small (compared to the total energy stored
in the Ring) and mainly due to deceleration of charged particles, I think;
the SPSs could easily replenish those losses. And, as a result of this weird
planetary magnetic field architecture, I doubt that there would be auroras
over the Martian poles; instead, perhaps there would be a toroidal aurora
around the planet during solar storms...

Lucio Coelho

Such a ring would be structurally impossible. Even if we found some
magic material with that kind of strength, superconductors can't
really store as much power as everyone believes. The same magnetic
field that you are trying to create will cause decoupling of electrons
in the superconductor making it lose superconductivity. The magnetic
field for complete decoupling is not very high and is normally
measured in the micro-Teslas.

Consider the problem of active shielding in colonies and then scale it
up to planetary levels.

What most terraforming enthusist believe is that planets are easier to
work with, because they happen to live on one. In reality all the
problems associated with space colonization (except possibly gravity)
would have to be solved on a planetary level. This includes atmosphere
retention, passive and active shielding, temperature control,
maintenance and control of the biosphere.

Stop thinking of Mars as that planet over there ready to be colonized,
and start thinking of it as a very large colony that has to be
actively managed like any other complex none self-regulating system.

Most people dismiss timescales of geological eras, but is anyone sure
that the timescales required to create a self-regulating planet wide
system is significantly smaller. Life on earth is about 4 billion
years old, and for 3.4 billion of those years the highest life form
was blue green algea. What if it takes a million years for the
equivalent organism on Mars to get to a self-regulating stage that
allows more complex life forms to exist on the surface? Can human
interference significantly decrease the time, or are we simply
producing a system that has to be maintained and regulated by us for a
million years while that organisms do what it has to do to make Mars
habitable.

Finally even if we were successful in producing a self-regulating
bio-sphere on Mars, why is anyone so sure that humans would be able to
live there?

Bill
--- In spacesettlers@y..., "Dr. Omni" wrote:
> From:
> To:
> Sent: Wednesday, July 18, 2001 11:25 PM
> Subject: [spacesettlers] Re: Not that I WANT to terraform Mars...
>
> Yes, yes, but wasn't there something in here a month or so agao
about
> the solar wind doing nasty things to the atmosphere if you don't
have
> a magnetic field? And if we assume that one is needed (for whatever
> reason), how do we go about putting it there?
> [snikt]
>
> I remember that I heard somewhere that solar wind can "erode" an
atmosphere.
> However, I much doubt that this process is quick - my gut feeling is
that it
> would take millions of years for an atmosphere to be completely
blown away
> by the solar wind. And, since geological timescales are meaningless
for
> human civilizations, that would not be an unavoidable obstacle for a
Mars
> terraformation project - people would be content in living in a
planet for
> mere tens of thousands of years, which by the way is many times the
whole
> human history so far.
>
> But okay, lets assume that, for some obscure reason, people could
not live
> in a planet without a magnetic field and the terraformers would have
to
> build one from scratch. Well, I am kind of short in wacky ideas
right now,
> but anyway it seems to me that a way to do that would be to build a
gigantic
> superconducting ring in orbit around the planet (perhaps Phobos and
Deimos
> could be consumed to do that, perhaps they would need a whole bunch
of
> asteroids, I don't know). This Ring of Power (sorry, I could not
avoid a
> reference to Tolkien ;-) could be powered by hundreds of solar power
> stations connected to it, and then it would soon be teeming with a
really,
> really huge electric current. As a consequence, it would generate a
magnetic
> field of planetary scale. Since the ring would be superconducting,
the
> energy losses would be extremely small (compared to the total energy
stored
> in the Ring) and mainly due to deceleration of charged particles, I
think;
> the SPSs could easily replenish those losses. And, as a result of
this weird
> planetary magnetic field architecture, I doubt that there would be
auroras
> over the Martian poles; instead, perhaps there would be a toroidal
aurora

Such a thing could probably be done on mars, because of the lower gravity to
get the same pressure as earth at the surface there would have to be more mass
in the atmosphere.

Having a higher pressure atmosphere would make that effect even more
pronounced.

If we do decide to put a magnetic field around mars then we may have to dump
large amounts of radioactive substances into its core to get some heat needed
to make it liquid and flow.

--- Bill wrote:

From: Bill [mailto:qwerty172@...]

The erath's magnetic field traps over 90% of the cosmic rays. With out
it the earth's atmosphere would have to be 10 times as thick.

Wow. So if this is right, then even the 3x thickness atmosphere we earlier
said would be necessary for sea-level pressure air on the surface of Mars
would be inadequate. Interesting.

Regards,

Mike Combs

From:
Bill [mailto:qwerty172@...]
The erath's magnetic field traps over 90% of the cosmic rays. With out
it the earth's atmosphere would have to be 10 times as thick.

Wow. So if this is right, then even the 3x thickness atmosphere we earlier said would be necessary for sea-level pressure air on the surface of Mars would be inadequate. Interesting.

Regards,
Mike Combs

From: Bill [mailto:qwerty172@...]

What most terraforming enthusist believe is that planets are easier to
work with, because they happen to live on one.

I think this statement hits the nail on the head more squarely than just
about any other statement I've seen on this subject.

In reality all the
problems associated with space colonization (except possibly gravity)
would have to be solved on a planetary level. This includes atmosphere
retention, passive and active shielding, temperature control,
maintenance and control of the biosphere.

Stop thinking of Mars as that planet over there ready to be colonized,
and start thinking of it as a very large colony that has to be
actively managed like any other complex none self-regulating system.

I've been arguing this point in the space newsgroups on Usenet for several
years now. I've become convinced that my chief difficulty is the unspoken
(and thus unquestioned) assumption that Mars "meets us halfway". But some
thoughtful and informed analysis will quickly show that this is not the
case.

Regards,

Mike Combs

From:
Bill [mailto:qwerty172@...]
What most terraforming enthusist believe is that planets are easier to
work with, because they happen to live on one.

I think this statement hits the nail on the head more squarely than just about any other statement I've seen on this subject.

In reality all the
problems associated with space colonization (except possibly gravity)
would have to be solved on a planetary level. This includes atmosphere
retention, passive and active shielding, temperature control,
maintenance and control of the biosphere.
Stop thinking of Mars as that planet over there ready to be colonized,
and start thinking of it as a very large colony that has to be
actively managed like any other complex none self-regulating system.

I've been arguing this point in the space newsgroups on Usenet for several years now. I've become convinced that my chief difficulty is the unspoken (and thus unquestioned) assumption that Mars "meets us halfway". But some thoughtful and informed analysis will quickly show that this is not the case.

Regards,
Mike Combs

Hey!

YOUR head is great!! =)
I definatly think so too!!
And I read KS Robinsons Mars trilogy, I loved it, since that I wanna
go to Mars, maybe I can =)

cu,
Juxi

--- In spacesettlers@y..., "Dr. Omni" wrote:
> From: "Combs, Mike"
> To:
> Sent: Wednesday, July 18, 2001 6:07 PM
> Subject: RE: [spacesettlers] Not that I WANT to terraform Mars...
>
> [snikt]
> > If they did make this argument, I think it would be a very poor
one.
> Living
> > underground even after terraformation is certainly not what most
people
> are
> > visualizing when considering the concept.
> >
> Yes, I agree - I realized that just after sending my previous
message. I was
> thinking with *my* head - the head of a wannabe space settler who
does not
> care if he will live in a spinning can or in a habitat buried in
regolith,
> as long as he is off-Earth. But then I remembered that the typical
Zubrinite
> wants to practice hiking in Olympus Mons and make marathons along
the

From: "Bill"
To:
Sent: Thursday, July 19, 2001 1:38 AM
Subject: [spacesettlers] Re: Not that I WANT to terraform Mars...

Such a ring would be structurally impossible.

I can't see why. The *entire* ring would be in circular orbit around Mars -
that is, the ring would be spinning in orbital velocity around Mars - and
so gravity would be counteracted by centrifugation, as in the case of any
satellite. As for tidal effects, I don't think that the ring would be more
than a few kilometers thick, and so the tidal effects would as negligible as
they are in Phobos and Deimos.

Even if we found some
magic material with that kind of strength, superconductors can't
really store as much power as everyone believes. The same magnetic
field that you are trying to create will cause decoupling of electrons
in the superconductor making it lose superconductivity. The magnetic
field for complete decoupling is not very high and is normally
measured in the micro-Teslas.

That seems a more plausible objection. I agree that the terraformers would
need a magical superconducting material (stable metallic hydrogen), not a
magical *structural* material.

[snikt]
Stop thinking of Mars as that planet over there ready to be colonized,
and start thinking of it as a very large colony that has to be
actively managed like any other complex none self-regulating system.

Hey, I never thought of Mars "as that planet over there ready to be
colonized". Remember, I'm the guy who created this group and who wrote at
the home page that this is for people who believe that space settlements are
a better option than terraformation ;-).

Anyway, I like to think about terraformation just because I think that it is
an amusing mind exercise. It is like thinking about interstellar travel: it
is something that you know will probably never be viable, but anyway it is
an interesting puzzle to solve. That's what I'm playing with in this thread.

[snikt]
Bill

Lucio

I'm still unconvinced that a magnetic field is indispensable. Even if
without the magnetic field the radiation level is ten times higher, as far
as I know the radiation level at Earth's surface is so low that a level 10
times higher would not be dangerous yet. Perhaps it would be less than that
experienced by someone who works with radioisotopes.

Eventually, I'll check this information at my "The Higher Frontier", but
right now I'm too sleepy to do that ;-). By the way, if your reasoning is
correct, it would also imply that space settlements would have to have a
passive shield 100 meters thick, instead of just 10 meters thick.

Lucio Coelho

From: "Bill"
To:
Sent: Thursday, July 19, 2001 12:41 AM
Subject: [spacesettlers] Re: Not that I WANT to terraform Mars...

For everyone who is not yet convinced the magnetic field is necessary
go to google or your favourite search engine and type von allen belt.

The von allen belts is the belts of cosmic rays that get trapped above
the atmosphere by the earth's magentic field and is disappiated at
the north and south pole.

The erath's magnetic field traps over 90% of the cosmic rays. With out
it the earth's atmosphere would have to be 10 times as thick.
[snikt]

--- In spacesettlers@y..., "Dr. Omni" wrote:

> Anyway, I like to think about terraformation just because I think
> that it is an amusing mind exercise. It is like thinking about
> interstellar travel: it is something that you know will probably
> never be viable, but anyway it is an interesting puzzle to solve.
> That's what I'm playing with in this thread.

I can't help but think that interstellar travel will be viable before
terraformation is. Not that BOTH will nessesarily be impossible
forever.

From: "Dr. Omni"
To:
Sent: Friday, July 20, 2001 12:10 AM
Subject: Re: [spacesettlers] Re: Not that I WANT to terraform Mars...

[snikt]
> Eventually, I'll check this information at my "The Higher Frontier", but
> right now I'm too sleepy to do that ;-). By the way, if your reasoning is
> correct, it would also imply that space settlements would have to have a
> passive shield 100 meters thick, instead of just 10 meters thick.
[snikt]

Well, I have just checked the Scriptures ("The High Frontier" - does anyone
doubt that O'Neil is our Prophet? ;-) and in "Chapter 7: Risks and Dangers"
it is written (page 52, 2nd paragraph, in the 3rd Edition):

"When all the sources of natural radiation, internal, external and cosmic,
are added, they amount to an average dose of about a third of a rad per year
for a typical Earth dweller. After a great deal of testing and years of
discussion, to which many physicists and biologists contributed, the Atomic
Energy Comission (in the days long before it was called ERDA) settled on an
allowable anual dose for its workers of five rad per year, and of a tenth
that for the total U.S. population".

That is, even though the radiation levels on Earth were increased ten times,
the average radiaton level would be about 3 rads/year per person, which is
lower than the maximum level still considered safe.

More down the road, O'Neil makes a series of considerations about habitats
outside the magnetosphere, cosmic rays, solar flares and stuff like that and
concludes that (page 53, 3rd paragraph in the 3rd Edition) "When the numbers
are worked out, we find that the shielding needed is substantial -
equivalent to about two meters (over six feet) of soil.". Well, that means
something about four or five metric tons per square meter of the shield, I
guess, and therefore a 1/3 bar Martian atmosphere, with 10 tons per square
meter, would be more than enough.

The conclusion: the Martian atmosphere imagined by the Zubrinites is a nice
passive shield. A magnetosphere is not really needed: the question is that
Earth's active and passive shielding is not just enough, it is *far more*
than enough.

Lucio Coelho

Sorry didn't mean to offend you. I was talk you(plural) for anyone
with dreams of going to Mars and walking out the space ship.

If you want terraforming as a mind exercise. I can see some problems
that need to be solved.

Physically
Gravity is to low to retain an atmosphere. You can add gases to the
existing atmosphere but they will leak out. How much air pressure do
you want? If earth normal, how fast will this leak away. Is it slow
enough that replenishing the atmosphere is possible, remembering that
you can't wait until 10% is gone before adding more.

Gravity is low. What effect will this have on plants and animals?

Temperature. How do you increase the temperature of the planet to
livable levels. Can this be done with green house gases alone, or will
you need large numbers of mirrors to increase the amount of sunlight
hitting the planet.

Cosmic Rays. Can life exist in say 2 or 3 times the amount of cosmic
rays hitting the earth?

Biosphere. Can a biosphere be created on Mars? Will it be self
sustaining or will it need constant vigil on part of human beings?

Timescale. Can this be done in the time an average civilization
exists. If it take a million years or hundred thousand years to get
something stable enough that people want to live there, will it ever
happen?

Bill

> Stop thinking of Mars as that planet over there ready to be
colonized,
> and start thinking of it as a very large colony that has to be
> actively managed like any other complex none self-regulating system.
>
> Hey, I never thought of Mars "as that planet over there ready to be
> colonized". Remember, I'm the guy who created this group and who
wrote at
> the home page that this is for people who believe that space
settlements are
> a better option than terraformation ;-).
>
> Anyway, I like to think about terraformation just because I think
that it is
> an amusing mind exercise. It is like thinking about interstellar
travel: it
> is something that you know will probably never be viable, but anyway
it is
> an interesting puzzle to solve. That's what I'm playing with in this
thread.

The Earth normal assumption is what the 10 m thick shield was designed
for. In fact the design requirement was half the radiation level in
Denver Colorado. I'm not sure why by the way. I also don't remeber it
being 10 m. Are you sure it was 10 m and not 10ft? The study I
normally quote is the AMES study that brought out the Standford Torus
as the design.

As for what is the maximum amount radiation that can be acceptable is,
I don't know. I would go with the radiation levels allowed by the
nuclear industry as a guideline myself, but are they to high or to low
is anyones guess.

Bill

--- In spacesettlers@y..., "Dr. Omni" wrote:
> I'm still unconvinced that a magnetic field is indispensable. Even
if
> without the magnetic field the radiation level is ten times higher,
as far
> as I know the radiation level at Earth's surface is so low that a
level 10
> times higher would not be dangerous yet. Perhaps it would be less
than that
> experienced by someone who works with radioisotopes.
>
> Eventually, I'll check this information at my "The Higher Frontier",
but
> right now I'm too sleepy to do that ;-). By the way, if your
reasoning is
> correct, it would also imply that space settlements would have to
have a
> passive shield 100 meters thick, instead of just 10 meters thick.
>
> Lucio Coelho
>
> From: "Bill"
> To:
> Sent: Thursday, July 19, 2001 12:41 AM
> Subject: [spacesettlers] Re: Not that I WANT to terraform Mars...
>
> For everyone who is not yet convinced the magnetic field is
necessary
> go to google or your favourite search engine and type von allen
belt.
>
> The von allen belts is the belts of cosmic rays that get trapped
above
> the atmosphere by the earth's magentic field and is disappiated at
> the north and south pole.
>
> The erath's magnetic field traps over 90% of the cosmic rays. With
out

From: Dr. Omni [mailto:dromni@...]

Well, I have just checked the Scriptures ("The High Frontier" - does anyone
doubt that O'Neil is our Prophet? ;-)

Which would make us his disciples. Heh.

I just call myself one of "Gerry's Kids".

Regards,

Mike Combs

From:
Dr. Omni [mailto:dromni@...]
Well, I have just checked the Scriptures ("The High Frontier" - does anyone
doubt that O'Neil is our Prophet? ;-)

Which would make us his disciples. Heh.

I just call myself one of "Gerry's Kids".

Regards,
Mike Combs

Dr. Omni wrote:

> From: "Bill"
> To:
> Sent: Thursday, July 19, 2001 1:38 AM
> Subject: [spacesettlers] Re: Not that I WANT to terraform Mars...
>
> Such a ring would be structurally impossible.
>
> I can't see why. The *entire* ring would be in circular orbit around Mars -
> that is, the ring would be spinning in orbital velocity around Mars - and
> so gravity would be counteracted by centrifugation, as in the case of any
> satellite. As for tidal effects, I don't think that the ring would be more
> than a few kilometers thick, and so the tidal effects would as negligible as
> they are in Phobos and Deimos.

I think this can be done. There are some big issues though.

Rings like that are in unstable equilibrium. You give them
the slightest nudge and a few days later they impact the planet.
(The instability is somewhat counterintuitive.) [If you want to
know why or how, check the web for references to instability and
'Ring World' by Larry Niven.]

This isn't to say that rings in general are unstable (Saturn doesn't
have any worries), but continuous rings have this issue.

Anyway- the ring is stabilisable, but it would take quite careful
design to do that. It's not a trivial problem.

> Even if we found some
> magic material with that kind of strength, superconductors can't
> really store as much power as everyone believes. The same magnetic
> field that you are trying to create will cause decoupling of electrons
> in the superconductor making it lose superconductivity. The magnetic
> field for complete decoupling is not very high and is normally
> measured in the micro-Teslas.
>
> That seems a more plausible objection. I agree that the terraformers would
> need a magical superconducting material (stable metallic hydrogen), not a
> magical *structural* material.
>
> [snikt]
> Stop thinking of Mars as that planet over there ready to be colonized,
> and start thinking of it as a very large colony that has to be
> actively managed like any other complex none self-regulating system.
>
> Hey, I never thought of Mars "as that planet over there ready to be
> colonized". Remember, I'm the guy who created this group and who wrote at
> the home page that this is for people who believe that space settlements are
> a better option than terraformation ;-).
>
> Anyway, I like to think about terraformation just because I think that it is
> an amusing mind exercise. It is like thinking about interstellar travel: it
> is something that you know will probably never be viable, but anyway it is
> an interesting puzzle to solve. That's what I'm playing with in this thread.
>
> [snikt]
> Bill
>
> Lucio
>

--
- Ian Woollard (ian.woollard@...)

"Is a planetary surface the right place for an expanding technological
civilization?"
- Gerard O'Neill

From: "Bill"
To:
Sent: Friday, July 20, 2001 2:57 PM
Subject: [spacesettlers] Re: Not that I WANT to terraform Mars...

The Earth normal assumption is what the 10 m thick shield was designed
for. In fact the design requirement was half the radiation level in
Denver Colorado. I'm not sure why by the way. I also don't remeber it
being 10 m. Are you sure it was 10 m and not 10ft? The study I
normally quote is the AMES study that brought out the Standford Torus
as the design.

According to a geographic atlas that I'm checking just now, Denver seems to
be located in a very high place (over 3 Km?); hence, they have less passive
shielding from the atmosphere, like anyone living in high mountains or
plateaus (e.g., in the Andes). The fact that people living there do not have
remarkably high cancer or mutation rates is an indication that the radiation
level is ok even though it is higher than at sea level. So, in the AMES
study, they assumed a passive shield equivalent to the one provided by the
atmosphere in high places.

Yes, I remember that in the AMES study the thickness of the shield was 4
meters or so (about 12 feet - close to your 10 feet figure). I mentioned a
radiation shield 10 m thick because this thickness would provide, I think,
about the same shielding that people have at sea level (assuming a linear
relation between thickness and shielding). Again, a case of "more than
enough shielding".

[snikt]
Bill
[snikt]

Lucio

From: Dr. Omni [mailto:dromni@...]

Yes, I remember that in the AMES study the thickness of the shield was 4
meters or so (about 12 feet - close to your 10 feet figure).

I was thinking that it was closer to 2 meters. And that was what produced
the "safer than Denver" conditions.

Regards,

Mike Combs

From:
Dr. Omni [mailto:dromni@...]
Yes, I remember that in the AMES study the thickness of the shield was 4
meters or so (about 12 feet - close to your 10 feet figure).

I was thinking that it was closer to 2 meters. And that was what produced the "safer than Denver" conditions.

Regards,
Mike Combs