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Old 11-29-2021, 03:48 AM   #7
whswhs
 
Join Date: Jun 2005
Location: Lawrence, KS
Default Re: vehicles on Mars: lifting capacity

Quote:
Originally Posted by Anthony View Post
Interesting, it turns out that pretty much every variable other than molar weight can be ignored when figuring out the amount of payload a given quantity of lifting gas can lift.
Indeed, and that was what I relied on in figuring the relative weights of hydrogen and the hypothetical Martian atmosphere. You'll note that my answer for 9.5M cf of lifting gas was "a bit over 5000 pounds," which is quite close to your answer of 5000 pounds exactly, so we're working on the same basic logic and getting comparable results.

I would attribute the discrepancy to my not following your suggestion that "storage and production of lifting gas should both be dependent on the number of mols, not some theoretical volume." GURPS doesn't use this approach; it uses a fixed number of cubic feet of various lifting gases per pound of lift, disregarding differences in temperature. Since I'm looking for an order-of-magnitude answer to "Can this thing get off the ground?" I went along with that as a gamable abstraction. I don't plan to be looking up exact altitudes, figuring exact local pressure, estimating exact local temperature, and so on during play; rather, I'm going to assume that managing gas volume and ballast falls under the skill of Piloting (Lighter-than-Air, Mars).

For what it's worth, my estimate was that artificial greenhouse gases had given Mars a mean temperature that worked out to a few degrees below freezing (at least by Earth standards of freezing; Mars's lower pressure may change that). The difference is probably not great enough to change your result substantially.
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