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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: 0) by Anonymous Coward on Wednesday April 19 2017, @06:17PM
I'm not sure that's a big deal, really -- you just put much bigger fans on the same motor. Thrust, drag, and buoyancy all scale with atmospheric density, so while the thing will be freaking big for a given payload capacity, it shouldn't take inordinate power to push through the thin atmosphere at blimp-like airspeeds. (Of course, blimp-like airspeeds may be a problem if you need to travel upwind...)
I'm not sure what the scaling law for payload vs. length looks like -- obviously total buoyancy scales with the cube of length, but you have to subtract the structural weight, and I don't know how that varies. Should be no worse than squared, though, right? So if you figure thrust, drag, and payload all scale linearly with density, and with the square of length, then you can just scale an Earth blimp up 10x in every direction. And since they say their vacuum airship design can carry more payload for a fixed size, it would be a smaller envelope for the same payload, thus less drag, and either less thrust required, or more speed available.
(I'm sceptical of the whole vacuum-airship thing -- the idea of being able to repair it and re-evacuate with no need for a supply of lifting gas is nice, but I'm suspicious of how much damage the "lattice" can take before field repairs become impossible. Patching a blimp, on the other hand, is trivial for small punctures, and manageable for large tears; same goes for damage to the envelope in a semi-rigid airship, although a damaged keel puts you in the same fix as the vacuum airship.)