Liquid Oxygen Questions

>
> First, if we assume an atmospheric pressure, could be anything,
but
> let's work with 1 atmosphere. The effect of this atmospheric
> pressure would be to exert a force of 15 lbs/in2 against the
> pressure vessel.
>
> O'Neill assumed an atmosphere of 1/2 sea-level pressure, with the
percentage
> of oxygen doubled, and the percentage of nitrogen reduced
accordingly.
> Mostly to reduce that pressure load, which would be the lion's
share of the
> total loading, even assuming rotation for 1 G.
>

I realize that there are different schemes for atmospheric pressure
and O'Neill had written about non-earth atmospheric compositions,
but I'm a skeptic on that part of O'Neill's plan. If we're trying to
replicate a functioning environment, I don't think we can take it as
a given that changing the atmosphric ratios won't effect the
interrelationships in the biosphere.

To replicate the earths atmosphere reduces the uncertainty we'll
face while increasing the engineering cost of the habitat. Which
science do we have a better mastery of - engineering pressure
vessels or creating CELSS?

Until we increase our mastery of how to create and manage a complex
CELSS, I would argue that it makes more sense to plan to replicate
earth atmospheric composition than to base the design and
engineering of a habitat for a reduced pressure loading and hope and
pray we can create a CELSS that will function in a different
atmospheric mix.

Like O'Neill himself wrote, he'd be the first one to be surprised if
the eventual habitats were as he wrote about them. So we can't take
everything he wrote about as gospel. Though, I would welcome some
counter arguments about my concerns about the engineering vs. CELSS
question. I'm not feeling completely on solid ground about my
position until I can see what the counter arguments are.

> Now how does the radius of the cylinderical habitat
> effect the total mass of the atmospheric gases? The way I see it,
> the mass of the gases is directly proportional to the area of the
> pressure vessel and the height has no effect.
>
> Not at the kind of scales we can realistically talk about within
the limits
> of current material strengths. Air mass would roughly vary with
the cubic
> volume, as the pressure at the spin axis would be scarcely any
less than at
> the cylinder floor. O'Neill cited as one of the advantages of
Island 3 that
> mountain climbers and glider pilots would find they had no
breathing
> difficulties no matter how "high" they went, at altitudes where
here on
> Earth breathing apparatus is called for.

Ok, so the effect of the centrifugal force (gravity substitute)
being greater near the surface wouldn't draw more of the atmospheric
density down and leave less atmosphere up near the axis where there
would be zero-g.

My understanding of gas theory is very rusty. You assert that the
atmosphere, even for an Island 3 would be mostly uniform in density
without the gravity gradient effect I was referring to in the above
paragraph. Are gases less effected by gravity?
>
> But there was one guy who wrote a paper on the subject of how
diamondoid
> (would require molecular-scale manufacturing) could affect the
space
> picture. In addition to Super-Shuttles and orbital elevators, he
also
> talked about mega-cylinders. These would be so huge (1/13th the
diameter of
> the Earth if I figured correctly) that the atmosphere would pool
on the
> cylinder floor, and one would have the situation that I suspect
you've been
> visualizing.

I'm assuming that there was good physics behind his prediction. If
so, then I didn't realize that the atmospheric gradient would
require such a large radius to bring about that effect.

>
> On commenting that one wouldn't be able to strap on wings and fly
near the
> axis as had been advertised, he then scaled down his design so
that the
> pressure at the axis would be at least half of what you saw on the
cylinder
> floor. Of all the possibly sensible reasons one might have for
scaling the
> cylinder down, I wouldn't let that be one. One might imagine large
> pressurized spheres up near the axis for flying in equipped with
air
> compressors.

Yeah, that should be the last criteria for scaling down the habitat.