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It's long been proposed to build rotating colonies (ring worlds) in outer space.

That concept can also be applied to surface colonies in low-g environments. (Luna is at 1/6th of Earth gravity; Mars is at 1/3.)

Conceivably, spacecraft built for long trips could rotate to provide artificial "gravity" as well. Creating a large cross-section might not be so great in light of the idea of collision with space debris, but at present I choose not to make a thorough evaluation of the practical concerns of that. Acceleration could also be produced by attaching a tether and counterweight to the habitable module. This would reduce cross-sectional area.

But, what is possible is not necessarily what is the best solution. Are rotating habitats considered the standard solution for long-term human habitations in low-g environments? If not... why not?

rotating moon habitat

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  • $\begingroup$ Related: "Why are there no spacecraft rotating for artificial gravity?" space.stackexchange.com/questions/1308/… $\endgroup$ – DJG Jul 21 at 1:41
  • $\begingroup$ The ultimate solution (outside of sci-fi gravity generators) is genetically engineering people to handle low gravity better. For example, increased bone and muscle density or more hand-like feet for navigation in low-g enviorments $\endgroup$ – Dragongeek Jul 21 at 10:50
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The current consensus is that living in zero G long term will have side effects, possibly lethal ones.

The current known ways to not have people exposed to zero G are:

  1. Have sufficient mass there is useful amounts of gravitation attraction
  2. Thrust continuously during travel
  3. Spin things up

Option one means that large amounts of energy are required arriving and departing, and is not very portable

Option two involves drive performance well outside anything feasible in physics as currently known, and may also have civilization ending side effects if built.

Option three is therefore the only one left hence showing up in designs. Even if the health effects can be managed there are tasks and processes easier to do with a defined 'down' (like eating, washing and using a toilet) that may justify the engineering complexity listed in DJG's answer.

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"Centripetal" section of Wiki article on Artificial Gravity says:

This form of artificial gravity has additional engineering issues:

  • Kinetic energy and angular momentum: Spinning up (or down) parts or all of the habitat requires energy, while angular momentum must be conserved. This would require a propulsion system and expendable propellant, or could be achieved without expending mass, by an electric motor and a counterweight, such as a reaction wheel or possibly another living area spinning in the opposite direction.

  • Extra strength is needed in the structure to keep it from flying apart because of the rotation. However, the amount of structure needed over and above that to hold a breathable atmosphere (10 tons force per square meter at 1 atmosphere) is relatively modest for most structures.

  • If parts of the structure are intentionally not spinning, friction and similar torques will cause the rates of spin to converge (as well as causing the otherwise stationary parts to spin), requiring motors and power to be used to compensate for the losses due to friction.

  • A traversable interface between parts of the station spinning relative to each other requires large vacuum-tight axial seals.

Possible solution to first bullet: Keep it spinning

... second bullet: Build it strong

... third bullet: maintain magnetic separation to reduce friction to near-zero, OR completely separate the spinning part from the non-spinning part, then spin down the spinning part if/when docking is required.

... fourth bullet: See third bullet, part 2, and/or exit to other parts of system through tunnel which goes parallel to and is concentric with axis of rotation... kind of like the hole in a toilet bowl. Use a magnetic bearing for the seam.

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    $\begingroup$ re fourth point, magnetic bearings may help for low friction physical loads but will not form an air tight seal. If you have a non rotating section with a pressurized connection there will be some form of physical contact there both generating friction and needing maintenance. Not insolvable but adding complexity. $\endgroup$ – GremlinWranger Jul 21 at 0:01
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Space habitats do rotate, but not for artificial gravity.

  • The ISS rotates to face the Earth. The Shuttle also did this. This means one rotation per day, which does not create significant artificial gravity.

  • Rotation also prevents one side from staying in the sunlight and getting too hot. Apollo rotated specifically for this reason (the "barbecue roll").

  • Solar panels need to face sunlight (although usually just the panels are rotated, not the whole spacecraft).

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