When floating inside a large space station, while away from its center of mass and without touching the structure of the station, the person floating and the station will have slightly different orbits, so the person will slowly move inside the station, and either end up near the starting position after one orbit or hit a wall.

Has this phenomenon ever been a problem, or an inconvenience?

Examples I can think of were it might be significant:

  • While doing experiments, you keep stable with your feet holding down on the station rails/handles, but the upper part of your body slightly tilts (could be uncomfortable?)
  • While sleeping, this presses you against a wall, which might be annoying if it's not the side you're used to sleeping on back on earth?

This question is about people and objects inside a space craft. Answers about EVAs and objects parked outside are welcome, but will not be marked as accepted.


1 Answer 1


Short answer: probably not, because tidal force resulting from slightly different orbits in spacestation-type distance scales is really small, likely smaller than plenty other disturbances.

If you calculate a circular orbit 6700 km from Earth centre and then move extra 100 m radially keeping the original angular speed, resulting force due to orbit "misalignment" on 100 kg body will be only about 40 mN. Barely noticeable, I believe. For comparison, it is a force in range which is exerted on your body by air flow (wind) speed fraction of m/s (less then what you would call for a breeze on Earth, or probably even notice).

  • 1
    $\begingroup$ OTOH, in the absence of other forces In your example, the off-centre individual will move 200 metres sideways in 45 minutes, and then start back... $\endgroup$
    – DJohnM
    Commented Sep 14, 2020 at 21:30
  • $\begingroup$ @DJohnM Or to make it even simpler, if you are above/below/left/right of the station and at rest with the station, you will be on the (roughly) opposite side 45 minutes later (unless the station gets in your way) $\endgroup$
    – asdfex
    Commented Feb 9, 2021 at 17:32

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