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"on Mars, a pressurized dome actually supports its own weight and then some. As a result, the structure is under tension and the dome is attempting to tear itse

"on Mars, a pressurized dome actually supports its own weight and then some. As a result, the structure is under tension and the dome is attempting to tear itself out of the ground. Since lifting force scales with area, while anchoring force scales with circumference, domes on Mars can’t be much wider than about 150 feet, and even then would require extensive foundation engineering." Huh, I always knew you could "float" domes from reading Red Mars but the lifting force sounds pretty gnarly. Boring rectangular boxes for all!

gpm 6y ago
Boxes face the same lifting force problem. Burying it (dome or box) below enough dirt can alleviate the problem, but it's a lot of dirt. Or you just make the structure with a lot of tensile strength. Run wires from the floor to the ceiling to hold the ceiling down.
- bloopernova 6y ago
  I've read "somewhere" that hollow lava tunnels/tubes could be used. Coat the inside with the plastic mentioned in the blog shared in another comment, and you possibly have an airtight (except for the soil) massive habitat. Although you'd have to string big lights along the top to grow plants.
  - gpm 6y ago
    This is a common idea - in a way it is as a shorcut to piling dirt on top of a structure that you make. Critics often bring up that exerting a huge force on the inside of lava tunnels might destabilize them in bad ways, and that sealing rough surfaces might be harder than just building a pressure vessel of your own.
pjc50 6y ago
Oh I see - the natural shape for a pressure vessel is a sphere, after all, so a dome will be constantly trying to make itself spherical. That does suggest that on Mars we should just make them spherical in the first place...
nickparker 6y ago
Casey Handmer argues [0] that The best solution is an “air mattress” structure where anchor cables are spaced throughout the structure to resist the pressure load. The anchor cables can scale linearly with area just like the pressure does, while a perimeter wall anchor scales with radius and therefore sets a limit on enclosure size. The cable anchor approach also lets you build arbitrarily high ceilings, like kilometers up hypothetically. I really wish someone would build one of these on Earth. It would actually be easier because you’d just set the pressure high enough to resist wind loads. You could make an incredibly gigantic greenhouse in some otherwise inhospitable climate [0]: https://caseyhandmer.wordpress.com/2019/11/28/domes-are-very-over-rated/amp/ https://caseyhandmer.wordpress.com/2019/11/28/domes-are-very...
- gpm 6y ago
  > I really wish someone would build one of these on Earth. It would actually be easier because you’d just set the pressure high enough to resist wind loads. You could make an incredibly gigantic greenhouse in some otherwise inhospitable climate This would require 2atm pressure (to be equivalent to mars) - how well do humans react to that sort of pressure for long periods of time?
  - DarthGhandi 6y ago
    Humans do remarkably well at high pressures. 2 atm pressure is the equivalent of being 10m underwater. If you go a lot higher you run into some issues and need to modify the gas composition/ratio, this has been thoroughly studied for diving purposes.

gpm 6y ago

Boxes face the same lifting force problem. Burying it (dome or box) below enough dirt can alleviate the problem, but it's a lot of dirt. Or you just make the structure with a lot of tensile strength. Run wires from the floor to the ceiling to hold the ceiling down.

bloopernova 6y ago
I've read "somewhere" that hollow lava tunnels/tubes could be used. Coat the inside with the plastic mentioned in the blog shared in another comment, and you possibly have an airtight (except for the soil) massive habitat. Although you'd have to string big lights along the top to grow plants.
- gpm 6y ago
  This is a common idea - in a way it is as a shorcut to piling dirt on top of a structure that you make. Critics often bring up that exerting a huge force on the inside of lava tunnels might destabilize them in bad ways, and that sealing rough surfaces might be harder than just building a pressure vessel of your own.

pjc50 6y ago

Oh I see - the natural shape for a pressure vessel is a sphere, after all, so a dome will be constantly trying to make itself spherical. That does suggest that on Mars we should just make them spherical in the first place...

nickparker 6y ago

Casey Handmer argues [0] that The best solution is an “air mattress” structure where anchor cables are spaced throughout the structure to resist the pressure load. The anchor cables can scale linearly with area just like the pressure does, while a perimeter wall anchor scales with radius and therefore sets a limit on enclosure size. The cable anchor approach also lets you build arbitrarily high ceilings, like kilometers up hypothetically. I really wish someone would build one of these on Earth. It would actually be easier because you’d just set the pressure high enough to resist wind loads. You could make an incredibly gigantic greenhouse in some otherwise inhospitable climate [0]: https://caseyhandmer.wordpress.com/2019/11/28/domes-are-very-over-rated/amp/ https://caseyhandmer.wordpress.com/2019/11/28/domes-are-very...

gpm 6y ago
> I really wish someone would build one of these on Earth. It would actually be easier because you’d just set the pressure high enough to resist wind loads. You could make an incredibly gigantic greenhouse in some otherwise inhospitable climate This would require 2atm pressure (to be equivalent to mars) - how well do humans react to that sort of pressure for long periods of time?
- DarthGhandi 6y ago
  Humans do remarkably well at high pressures. 2 atm pressure is the equivalent of being 10m underwater. If you go a lot higher you run into some issues and need to modify the gas composition/ratio, this has been thoroughly studied for diving purposes.