Digest Number 1288

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of ralph buttigieg

> Mars comes ready made water, in the atmosphere, in the
> ground and properbly even as liquid form .

It's not the same advantage as easy water availability on Earth. I see
only a small advantage to mining Martian permafrost vs. mining hydrated
minerals from an asteroid.

> It has an
> atmosphere which provides oxygen, nitrogen and CO2,

Yes, but what percentage of the total that we need is made up of
nitrogen and CO2? (I leave off O2 because any operation engaged in
refining ores is going to be producing more oxygen than what's needed.)

I once engaged in a debate with someone who insisted that the ability to
pump in carbon from the atmosphere of Mars was what made settlements on
the Martian surface easier than orbital habitats. I went back to the
Stanford Space Settlement study to determine, of all the things we need
for an independent 10,000 person habitat, what percentage of it is the
carbon. I found the below mass breakout.

>From Earth:
Gas and hydrogen: 21,100 tons ("Gas" probably includes nitrogen)
Biomass: 5,900
Furnishings: 25,000
Colonists: 600

Lunar-derived:
Soil: 220,000 tons
Structure: 500,000
Shield: 10,000,000

So the total for lunar-derived is: 10,720,000
and overall habitat mass is: 10,772,600 tons

Even if we exclude the mass for soil, and the mass for the radiation
shield (a Mars habitat might get by with a radiation shield of 1/3 the
mass, but would still require one), we see that biomass (which would
include more than just the carbon) only represents a hair over 1% of the
total mass required.

What we can get from these mass ratios is that if it might be easier to
process large amounts of steel, aluminum, and glass in HEO than on the
surface of Mars, this could totally overwhelm any slight advantage to
being able to simply pump in some CO2 from the outside. And given the
greater availability of sunlight in HEO and the practicality of large,
flimsy concentrating mirrors in that location, there's every reason to
suppose the first assumption is valid.

> dirt
> for radiation shielding is outside your door .

It must be granted that is a good advantage for Mars (or the moon).

> You can
> build regolith covered vaults for habitation and avoid
> pressure vessels.

They would still be pressure vessels. "Pressure vessels" doesn't
necessarily mean steel or glass skins. (But I should interject that the
demands of local agriculture will still necessitate huge glass-skinned
pressurized structures.) The engineering requirements for containing a
given air pressure are the same regardless of the building materials
chosen.

> Now I'm not saying large space colonies will never be built.
> Never is a long time. I am saying its far more likely the
> first permaanant colonies off Earth will be built on a
> planetery surface, not orbit.

I know that's conventional wisdom, but I don't happen to agree with it.
I don't think it takes into account the economic improvements which can
be had by the horizontal EM launching of raw material off an airless
surface.

Regards,

Mike Combs