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On 2018-08-09 16:52, Fred J. McCall wrote:

It's all about time scales. Can you add enough gas fast enough and
will it lose it slowly enough to be worthwhile.


You don't build and then board a leaky lifeboat unless you are damned
sure another boat will come in before it sinks.

All inflatable life boats have a leak rate that's non-zero. The point
is that the leak rate is far less than what would impact the use of the
life boat. Since a life boat will be used for days (or perhaps weeks at
most) as long as the leak rate is low enough, the boat is never in any
danger of sinking.

Also, life rafts quite often come equipped with manual air pumps to make
up for any losses caused by leaks caused by debris or other incidents
which happen after deployment. This is akin to adding a bit more
atmosphere when necessary.

Why spend the money/effort to add atmpsphere to Mars knowing that it
will be lost and you'll either have to continuously add to it, or
eventually leave Mars to get onto another planet?

Nothing humans build lasts on the timescales we're talking about here.
The oldest human artifacts are on the order of thousands of years old.
Mars lost its atmosphere over millions and millions of years.

Much simpler to build a domed city then to terraform Mars.

No one is saying otherwise, but eventually domes just aren't good enough
to contain your expanding population and another long term solution is
needed.

And on a more basic question: assuming unlimited supply of compressed
air being shipped to Mars, is it realistic to expect liveable air
pressure at ground when you consider Mar's reduced gravity and how much
more air your would need above you to achieve anything near 14.7psi ?

Look at Venus. This isn't a problem. One earth standard atmosphere of
pressure is actually very little.

If you can't achieve proper air pressure at ground, it is worth the
effort to try to terraform the planet since you wouldn't be able to go
outside without a space suit ?

You can. You just have to drop enough Kuiper belt objects on it. This
is an engineering problem, not a physics problem. Nothing in physics
prevents this from happening.

Jeff
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