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Mars is kind of short of nitrogen



 
 
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  #1  
Old February 12th 04, 03:58 PM
Sander Vesik
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Default Mars is kind of short of nitrogen

John Savard wrote:
but, as Robert Zubrin notes, it does seem to be the best place to set
up a colony.

However, are there any other alternatives that might be even more
attractive?

One of the objections Dr. Zubrin gives to O'Neill colonies is that a
mirror area comparable to the crop area is required for agriculture.
As it would seem to me that aluminized Mylar is easier to construct
than the *land area of the colony itself*, that seems to be an odd
objection.


It appears to be bar far better to use solar batteries and artifical
lightning combined with hydroponics.

[snip]

Since the gas giants have very deep gravity wells, comets and Pluto
seem to be the other potential non-terrestrial sources of nitrogen in
the Solar System.


Remember Titan.


John Savard
http://home.ecn.ab.ca/~jsavard/index.html


--
Sander

+++ Out of cheese error +++
  #2  
Old February 12th 04, 07:26 PM
Mike Combs
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Default Mars is kind of short of nitrogen

"John Savard" wrote in message
...

One of the objections Dr. Zubrin gives to O'Neill colonies is that a
mirror area comparable to the crop area is required for agriculture.
As it would seem to me that aluminized Mylar is easier to construct
than the *land area of the colony itself*, that seems to be an odd
objection.


Odd indeed, especially since later in the same book he recommends orbital
mirrors for speeding up the terraforming process on Mars.

There seems to be a general assumption that Mars colonies will obviously be
cheaper than orbital ones because where the latter are concerned you have to
build the very land underneath your feet for crying out loud. But I
question this assumption. In both cases, one must build an enormous
pressure vessel. The thin atmosphere of Mars is not going to mitigate the
expense of that by more than a percent or two. Unlike in a Mars dome, in
O'Neill habitats the "ground" rests on the inside of the pressure shell, but
any structure engineered to stand up to the air pressure can support a load
of 5 or 6 feet of soil without a lot more engineering.

So aside from "the ground under your feet", what else does Mars provide that
must be provided artificially in an orbital habitat? The only remaining
answers are gravity (the wrong amount as it happens) and a day night cycle.
Once you start that orbital habitat spinning, it's going to keep spinning
with practically zero ongoing expense. And I don't see what should be so
difficult or expensive about making a mirror tilt.

And I don't think Zubrin can even touch all of the arguments O'Neill made
regarding the advantages of orbital locations over planetary ones.

But the mirror area could be smaller if the colony was closer to the
Sun.


Very true, but given the greater presence of volatiles in the outer system,
and the simplicity and modest material requirements of space mirrors, I more
expect the opposite.

Venus' atmosphere has about the same percentage of nitrogen in it as
Mars', but it is many times denser. A well-shielded O'Neill colony - I
have a design for one, shaped like a wine bottle, with a further
shielding slab out past the mirrors putting light down the neck of the
bottle, where the shielding doesn't rotate - in orbit about Venus
might have access to a good source of biomass feedstock. (Metal and
rock would be sent from the Moon.)


I'd have a hard time seeing it being economically competitive to lift any
kind of volatiles from Venus vs. other locations we know about.

Since the gas giants have very deep gravity wells, comets and Pluto
seem to be the other potential non-terrestrial sources of nitrogen in
the Solar System.


That's where the smart money is.

--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"


  #3  
Old February 12th 04, 07:32 PM
Mike Combs
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Default Mars is kind of short of nitrogen

"Sander Vesik" wrote in message
...

It appears to be bar far better to use solar batteries and artifical
lightning combined with hydroponics.


I could believe this if I could believe that on a square-mile to square-mile
comparison, solar panels and electric lights were comparable in price to
aluminized Mylar and glass.

Remember Titan.


A good point. If it turns out that asteroids just can't provide the amounts
of nitrogen needed, export from Titan might actually help meet the demand.

--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"


  #4  
Old February 12th 04, 07:35 PM
Ool
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Default Mars is kind of short of nitrogen

"Sander Vesik" wrote in message ...
John Savard wrote:


One of the objections Dr. Zubrin gives to O'Neill colonies is that a
mirror area comparable to the crop area is required for agriculture.
As it would seem to me that aluminized Mylar is easier to construct
than the *land area of the colony itself*, that seems to be an odd
objection.


It appears to be bar far better to use solar batteries and artifical
lightning combined with hydroponics.


"Lighting."

The problem is that with the efficiency of these, which is limited by
the laws of physics, you'll always lose at least around 80% of the
original energy by converting light to electricity and back.

Since the gas giants have very deep gravity wells, comets and Pluto
seem to be the other potential non-terrestrial sources of nitrogen in
the Solar System.


Remember Titan.


I think many regions of the outer Solar System will become sources of
volatiles and light elements for the inner planetary orbits. And
heavy elements will become the prime trading goods for the outer ones.
Once humanity splits into societies inhabiting many different worlds
then many will have what others need and vice versa.

It's gonna be interesting...



--
__ “A good leader knows when it’s best to ignore the __
('__` screams for help and focus on the bigger picture.” '__`)
//6(6; ©OOL mmiv :^)^\\
`\_-/ http://home.t-online.de/home/ulrich....lmann/redbaron \-_/'

  #6  
Old February 12th 04, 10:02 PM
Joe Strout
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Default Mars is kind of short of nitrogen

In article ,
"Ool" wrote:

It appears to be bar far better to use solar batteries and artifical
lightning combined with hydroponics.


"Lighting."

The problem is that with the efficiency of these, which is limited by
the laws of physics, you'll always lose at least around 80% of the
original energy by converting light to electricity and back.


First: so what? Gather more energy. One of the primary points of
colonizing space is that energy is cheap and abundant.

Second: it doesn't even mean you need more light-gathering area (even
assuming solar power), because light in orbit is available 24/7 and at
much higher intensities than here on Earth.

Quick calculation: if we assume 20% efficiency for light-electricity,
and 55% efficiency for electricity-light (which is the current best
rate, in sulfer discharge lamps), the product is 11% efficiency.
Multiply by 7, for amount of sunlight available in GEO vs. the ground,
and you have 77% as much light available in this way as compared to
using the light directly.

But this does not take into account that the artificial light generated
might be more efficiently used for photosynthesis. Take that into
account, and I bet you could grow MORE crops per square meter of solar
panel than you could grow per square meter of dirt on Earth.

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'
  #7  
Old February 12th 04, 10:17 PM
Alex Terrell
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Default Mars is kind of short of nitrogen

lid (John Savard) wrote in message ...
but, as Robert Zubrin notes, it does seem to be the best place to set
up a colony.

However, are there any other alternatives that might be even more
attractive?

One of the objections Dr. Zubrin gives to O'Neill colonies is that a
mirror area comparable to the crop area is required for agriculture.
As it would seem to me that aluminized Mylar is easier to construct
than the *land area of the colony itself*, that seems to be an odd
objection.

That is about as stupid an objection as the rest of his objections,
which are only raised to push the case for Mars. The mirrors would
weigh less than the crop structure right out to Neptune.

But the mirror area could be smaller if the colony was closer to the
Sun.

Not worth it, since the mirror mass is trivial. Better to put them
close to Earth, within 3 days flight, where they can particpate in
Earth's economy.

Venus' atmosphere has about the same percentage of nitrogen in it as
Mars', but it is many times denser. A well-shielded O'Neill colony - I
have a design for one, shaped like a wine bottle, with a further
shielding slab out past the mirrors putting light down the neck of the
bottle, where the shielding doesn't rotate - in orbit about Venus
might have access to a good source of biomass feedstock. (Metal and
rock would be sent from the Moon.)

This is a good design, but a bigger challenge will be heat disipation
through the shield.

Since the gas giants have very deep gravity wells, comets and Pluto
seem to be the other potential non-terrestrial sources of nitrogen in
the Solar System.

Comets, and former comets, some of which have recently become NEOs.
They may well have ammonia deposits. It is also possible that the
lunar poles have frozen ammonia, though probably not enough for a few
O'Neill colonies. At worst, we'll need to go to the asteroid belt.

Medium term, it might be possible to scoop Nitrogren out of the
Earth's atmosphere. This wouldn't be enough for O'Neill colonies, but
would sufffice for large Torus stations).

John Savard
http://home.ecn.ab.ca/~jsavard/index.html
  #8  
Old February 13th 04, 12:32 AM
Hop David
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Default Mars is kind of short of nitrogen



John Savard wrote:
but, as Robert Zubrin notes, it does seem to be the best place to set
up a colony.

However, are there any other alternatives that might be even more
attractive?

One of the objections Dr. Zubrin gives to O'Neill colonies is that a
mirror area comparable to the crop area is required for agriculture.
As it would seem to me that aluminized Mylar is easier to construct
than the *land area of the colony itself*, that seems to be an odd
objection.


You aren't the first (or the last, I imagine) to raise this point. There
are many things Zubrin says I disagree with. (Although I still admire
the man).


But the mirror area could be smaller if the colony was closer to the
Sun.

Venus' atmosphere has about the same percentage of nitrogen in it as
Mars', but it is many times denser. A well-shielded O'Neill colony - I
have a design for one, shaped like a wine bottle, with a further
shielding slab out past the mirrors putting light down the neck of the
bottle,


Described on this page?:
http://www.hypermaths.org/quadibloc/science/spaint.htm

You call your mirror system "Cassegrain"?
After the parabolic mirror concentrates it into a focus
it looks like a convex mirror redirects the converging rays
back into parallel rays.

My system is somewhat similar:
http://clowder.net/hop/railroad/ChengHo.html
But where you have a convex mirror redirecting converging rays to
parallel, I have a smaller parabolic mirror sharing the larger
parabolic's focus.

Also I have a 4th mirror that reflects the parallel rays onto the sides
of the cylindrical hab. It seems to me your system would also need such
a mirror as parallel rays would just pass through the bottle's neck and
land on disk at the bottom instead of illuminating the bottle walls. Or
am I missing something?

In my design the hab is built from asteroidal materials atop the north
pole of the asteroid. So the asteroid provides radiation shielding over
almost 2 pi steradians. The walls of the hab have a mixture of water and
dirt that I hope would be adequate radition shielding from those
directions. The the 4 mirrors (including the axial mirror) would shield
some from the top. The top is the most vulnerable radiation leak in this
colony, I believe.

In future drawings I plan to make 2 habs spinning in opposite directions
- one on the north and the other on the south pole. The net angular
momentum is zero and so the entire mass would be more manueverable. (I
stole this idea from Mike combs who has imagined two linked Bernal
spheres spinning in opposite directions. His structure would also have
zero net angular momentum)

Also in my colony the atmosphere doesn't fill the entire cylinder - just
a cylindrical shell. Less nitrogen would be needed.

here the shielding doesn't rotate - in orbit about Venus
might have access to a good source of biomass feedstock. (Metal and
rock would be sent from the Moon.)


Asteroids could also be a source of metal and rock.


Since the gas giants have very deep gravity wells, comets and Pluto
seem to be the other potential non-terrestrial sources of nitrogen in
the Solar System.


We still know very little about the composition of most asteroids.
Perhaps some have ammonia or other nitrogren compounds. Especially the
outer main belt and the Trojans.


John Savard
http://home.ecn.ab.ca/~jsavard/index.html



--
Hop David
http://clowder.net/hop/index.html

  #9  
Old February 13th 04, 04:35 AM
Joe Strout
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Default Mars is kind of short of nitrogen

In article ,
Hop David wrote:

Joe Strout wrote:


but, as Robert Zubrin notes, it does seem to be the best place to set
up a colony.


All other factors (such as distance and travel time) being equal,
certainly so.

But those other factors are most decidedly NOT equal. It may still be a
great place to set up a colony one day, but definitely not the best
place to set up our *first* colony.


You like the moon, right?


Yep, it's true, we're very lucky to have such a large moon -- we're
practically a double planet, so we can make our first offworld colonies
right next door instead of halfway (or more!) across the solar system.
Moreover it's a great source of raw materials for orbital colonies, too.
If I believed in an intelligent Creator, I'd be thanking him for this
boon of a moon which so obviously means we're meant to colonize space.

To try and pass it up and dash directly for the planets is just
foolishness (backed by mostly foolish arguments, as we're seeing in this
thread).

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'
  #10  
Old February 14th 04, 06:55 AM
Sander Vesik
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Default Mars is kind of short of nitrogen

Mike Combs wrote:
"Sander Vesik" wrote in message
...

It appears to be bar far better to use solar batteries and artifical
lightning combined with hydroponics.


I could believe this if I could believe that on a square-mile to square-mile
comparison, solar panels and electric lights were comparable in price to
aluminized Mylar and glass.


covering square kilometers with thick layers of ultraclear glass so that you
both have radiation protection and not too bad light losses won't probably
be cheap either.

I'm quite sceptical of designs that have there be rolling fields of
agriculture hapenning inside O'Neill colonies - it seems like both not overly
thought out and very wasteful of space.


--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"



--
Sander

+++ Out of cheese error +++
 




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