Mars colonization versus Stanford Torus

Regarding the below, perhaps I should more open-minded about the possibility
of Martians selling nitrogen to orbital habitats. K. Eric Drexler discusses
this very possibility here (http://www.foresight.org/nano/Mars.html), and
this in an article which is otherwise very critical of Mars as a location
for settlement.

"Mike Combs" wrote in message
news:...
"John Savard" wrote

It just seems to me that there is still a definite advantage of Mars
over the Earth as the supplier to space habitats of resources in short
supply on the Moon.

The right question to ask is not which is better, Mars or the Earth. The
right question is which is the best source of all those potentially
available. We shouldn't leave out the NEAs. On a travel-time basis
they're
comparable to Mars. But the clincher is their shallow gravity wells.
CC-types will definitely supply all the carbon one could want. Hydrogen
would exist certainly in the form of hydrated minerals and potentially in
the form of deep core ice. Nitrogen would probably require a bit of
digging
and processing, but I think avoiding the gravity levy associated with the
Martian gravity well would pay for a good deal of processing. Where
nitrogen is concerned, I think there are sources available short of Oort
cloud frozen amonia, or the atmosphere of Titan.


--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

Mike Combs wrote:
Regarding the below, perhaps I should more open-minded about the possibility
of Martians selling nitrogen to orbital habitats. K. Eric Drexler discusses
this very possibility here (http://www.foresight.org/nano/Mars.html), and
this in an article which is otherwise very critical of Mars as a location
for settlement.

He quotes:
The martian atmosphere does contain about 2.5 percent nitrogen - an element rare in asteroids. Thus, it may someday prove desirable to build a polar processing plant to concentrate nitrogen (by freezing out carbon dioxide) and to ship it into space. There, it would find use as an oxygen diluent in the atmosphere of large-scale settlements.

Earth's atmosphere is some 79% nitrogen, which seems more promising
than Mars' 2.5%. If we need Nitrogen in large quantities* then scooping
it out of the Earth's upper atmosphere might be a better bet.

*Note, requirements are approx:
Mini torus: 240 tons
Stamford Torus: 24,000 tons
4km diameter, 12km long O'Neill cylinder, 1 Bar: 120 million tons

I susepct by the time we have the Stamford Torus we'll have rotovators
able to throw up 60 tons of every 30 minutes. Atmospheric scooping
could get something similar.

"Alex Terrell" wrote in message
oups.com...

4km diameter, 12km long O'Neill cylinder, 1 Bar: 120 million tons

I noticed you were citing 1 Bar for the atmosphere of an O'Neill Cylinder.
It's true that is the assumption in O'Neill's first paper in Physics Today
(http://members.aol.com/oscarcombs/TCoS.html), but it's an assumption that
he later called "naive". He later recommended an atmosphere of 1/2 the
pressure, with the percentage of oxygen doubled, and the percentage of
nitrogen reduced accordingly. That not only reduces the pressure load on
the structure by half, it significantly reduces the amount of nitrogen we
need, first by a half, and then further by reducing the relative percentage.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

Good point,

0.2 Bar Oxygen
0.3 Bar Nitrogen

3/8 the nitrogen requirement.

I did a quick analysis on a "Profac" base. This would be suspened from
an orbiting mother ship and fly through the upper atmosphere at some
6km / second, scooping and liquifying air. A 5m diameter scoop, flying
at 85km altitude, could capture 100 tons per day of air, or about 80
tons per day of nitrogen. This would be enough for a Stamford Torus
after 1 year of operation.

Unfortunatley, an O'Neil cylinder, even at lower pressure, still needs
some 1500 years of operation. Of course, the technology would be
scalable and repeatable.

"Alex Terrell" wrote in message
oups.com...

I did a quick analysis on a "Profac" base. This would be suspened from
an orbiting mother ship and fly through the upper atmosphere at some
6km / second, scooping and liquifying air. A 5m diameter scoop, flying
at 85km altitude, could capture 100 tons per day of air, or about 80
tons per day of nitrogen. This would be enough for a Stamford Torus
after 1 year of operation.

What do you plan to use for heat exchange? There'll be a lot of heat
associated with the ram intake, and then you have to get from that to (mild)
cryogen temps, and fairly quickly.

Unfortunatley, an O'Neil cylinder, even at lower pressure, still needs
some 1500 years of operation. Of course, the technology would be
scalable and repeatable.

I'll tell you what I always tell people abou the O'Neill Cylinder. We don't
have to worry about building it because it won't be built by Earth
civilization. It will be built by a future space-based civilization which
will get its start in much more modest habitats. By the time they're ready
to graduate up to an Island 3, material from the outmost parts of the
asteroid belt will be available, and that might include decent amounts of
ammonia ice. If not, we might even be harvesting material from the Trojans
by that point, and they should be a lot "juicier" than Main Belt asteroids.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

Mike Combs wrote:
"Alex Terrell" wrote in message
oups.com...

I did a quick analysis on a "Profac" base. This would be suspened from
an orbiting mother ship and fly through the upper atmosphere at some
6km / second, scooping and liquifying air. A 5m diameter scoop, flying
at 85km altitude, could capture 100 tons per day of air, or about 80
tons per day of nitrogen. This would be enough for a Stamford Torus
after 1 year of operation.

What do you plan to use for heat exchange? There'll be a lot of heat
associated with the ram intake, and then you have to get from that to (mild)
cryogen temps, and fairly quickly.

That is indeed the biggest challenge. I estimated the average surface
temperature at 740 degrees C. However, the intake would probably be
much hotter (1500 C) so the back end with the compressors could be
easier.

The original proposal for PROFAC had a nuclear reactor and an ion
engine. My idea is to have it suspended on tethers, which also supply
electricity, so no need for the engine or the power plant.

"Alex Terrell" :

The original proposal for PROFAC had a nuclear reactor and an ion
engine. My idea is to have it suspended on tethers, which also supply
electricity, so no need for the engine or the power plant.

TANTAAFL - What do you think happen when a tether genarates electric power?
The tether's orbit starts to drop as the energy has to come from somewhere.
No nuke/solar for power means you are going to crash and darn soon too!

Earl Colby Pottinger

--
Cruising, building a Catamaran, Rebuilding Cabin, New Peroxide Still Design,
Writting SF, Programming FOSS - What happened to the time?

"Alex Terrell" :

The original proposal for PROFAC had a nuclear reactor and an ion
engine. My idea is to have it suspended on tethers, which also supply
electricity, so no need for the engine or the power plant.

TANTAAFL - What do you think happens when a tether generates electric power?
The tether's orbit starts to drop as the energy has to come from somewhere.
No nuke or solar-cells for power means you are going to crash and darn soon
too!

Earl Colby Pottinger

--
Cruising, building a Catamaran, Rebuilding Cabin, New Peroxide Still Design,
Writting SF, Programming FOSS - What happened to the time?

Earl Colby Pottinger wrote:
"Alex Terrell" :

The original proposal for PROFAC had a nuclear reactor and an ion
engine. My idea is to have it suspended on tethers, which also supply
electricity, so no need for the engine or the power plant.

TANTAAFL - What do you think happen when a tether genarates electric power?
The tether's orbit starts to drop as the energy has to come from somewhere.
No nuke/solar for power means you are going to crash and darn soon too!

Let me clarify. The tethers don't generate electric power. They supply
power from a large mother ship in a 1000* km orbit. The mother ship has
lots of power generation (might need to be nuclear as solar may not
work too well at 1,000km), and electric propulsion.

*Actually, a 400-500 km orbit would make the design easier. However, I
would expect some rotovators to be around, and I think long cabled
structures ought to be in the same orbit.

Mike, can you write a short story based on this?