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from the nothing-is-lighter-than-*nothing* dept.
A vacuum airship made of a homogenous material cannot withstand the atmospheric pressure on Earth for any material humans have yet discovered, which can be proven using the critical buckling load of a sphere. However, from an initial analysis of the vacuum airship structure and relationship to atmospheric conditions, Mars appears to have an atmosphere in which the operation of a vacuum airship would not only be possible, but beneficial over a conventional balloon or dirigible. In addition, a multi-layer approach, in conjunction with a lattice, would circumvent the buckling problems of a single homogenous shell. The lattice used to support the two layers of the vacuum airship shell can be made, using modulation of the lengths of the members, to fit the curvature of the vacuum airship precisely by following an atlas approach to the modulation.
The Martian atmosphere has a pressure to density ratio that is very beneficial to the operation of a vacuum airship; this is a result of the high average molecular weight of the atmosphere (relative to other planets in the solar system) and the temperature of the atmosphere, the trend for which can be observed from the ideal gas law. Through a more in-depth analysis of the vacuum airship model, it can be shown that the vacuum airship may theoretically carry more than twice as much payload as a modeled dirigible of the same size, a 40-meter radius, in the Martian atmosphere.
NASA Innovative Advanced Concepts (NIAC) Program. NBF.
(Score: 2, Interesting) by khallow on Wednesday April 19 2017, @06:04AM (6 children)
Instead, fill it with hydrogen. The atmosphere of Mars is mostly CO2. That means the average molecular mass is around 44. Hydrogen is 2. You will get more than 95% of the lifting power of pure vacuum with hydrogen at equal pressure to the atmosphere. So almost the same lift with far less structure (latex and mylar balloons on Earth already operate at pressures and temperatures similar to summer on Mars.
(Score: 1) by khallow on Wednesday April 19 2017, @01:02PM
(Score: 2) by Rivenaleem on Wednesday April 19 2017, @01:31PM (1 child)
Is there not sufficient O2 in Mars's atmosphere to make the highly combustible Hydrogen still a highly risky choice?
(Score: 2, Informative) by khallow on Wednesday April 19 2017, @02:34PM
Is there not sufficient O2 in Mars's atmosphere to make the highly combustible Hydrogen still a highly risky choice?
No. For starters, the much lower pressure just by itself would make even a pure oxygen atmosphere considerably safer than Earth's atmosphere. And actual oxygen content of the martian atmosphere is 0.15% which is way below any threshold of risk.
The real danger from combustion would be hydrogen reacting with human breathable atmosphere in habitats or perhaps the vehicle's interior. There are a variety of designs where that could be a problem.
(Score: 2) by AndyTheAbsurd on Wednesday April 19 2017, @02:58PM (2 children)
You have to add mass and structure to prevent the balloon from collapsing due to atmospheric pressure pushing in. 0.01 atmospheres or less, isn't much
Well, surface pressure on Mars is just 0.00628 atmospheres, so no problem, right?
Please note my username before responding. You may have been trolled.
(Score: 0) by Anonymous Coward on Wednesday April 19 2017, @06:26PM
Averaged over the whole surface, maybe. At the bottom of Hellas it's about twice that.
(Score: 1) by khallow on Thursday April 20 2017, @04:45AM
Well, surface pressure on Mars is just 0.00628 atmospheres, so no problem, right?
Still is a problem. Pressure to resist deflation may be much lower, but so is the lift. Meanwhile with hydrogen, you get more than 95% of the lift without that internal structure. Plus we've already flown gas-filled balloons under near Martian conditions and the balloon can expand as it rises to maintain the lift.