# On Building a Lunar Ringway. . . **URL:** \ **Category:** Factual Questions\ **Created:** [November 14, 2019, 12:30pm UTC](https://boards.straightdope.com/t/on-building-a-lunar-ringway/843407 "2019-11-14T12:30:29Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 17, 2019, 3:05pm UTC](https://boards.straightdope.com/t/on-building-a-lunar-ringway/843407/21 "2019-11-17T15:05:45Z")
[Egon]Don’t cross the hoops.[/Egon] Any attachment that isn’t fairly close to the plane of orbit is going to be bad. An entire hoop perpendicular to the main ring had better not be attached. It needs to rotate on it’s own in an entirely different direction to stay up. Masscons and gravity from the Sun and Earth will cause more than up-down perturbations. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [November 17, 2019, 6:38pm UTC](https://boards.straightdope.com/t/on-building-a-lunar-ringway/843407/22 "2019-11-17T18:38:25Z")
> [@RioRico](#): > > I’m envisaging a giant hula-hoop of a space station circling Luna. Two nested hula-hoops of different circumferences actually, cross-section **8** , with the outer hoop spun to a desirable gravity, and the inner hoop hosting movable ballast weights that are shifted to counter any perturbation. That way, stability needn’t exhaust reaction mass. The obvious question: Would shifting ballast be enough to keep the station from crashing down? Or would interlocked crossing polar and equatorial hoops work? Did you watch the video by Isaac Arthur, or read the description on Wikipedia? The dynamic orbital ring concept allows you to compensate for the effects of perturbation, by adjusting the strength of the magnetic fields deflecting the mass particles. In theory, anyway. ---
**Author:** ![tampora](https://avatars.discourse-cdn.com/v4/letter/t/9de0a6/32.png) [@tampora](https://boards.straightdope.com/u/tampora)\ **Post date:** [November 18, 2019, 1:27am UTC](https://boards.straightdope.com/t/on-building-a-lunar-ringway/843407/23 "2019-11-18T01:27:46Z")
If Earth’s tidal forces are a problem, couldn’t you position the ring so everywhere on the ring is equidistant from Earth at all times? Since the moon is tidally locked, shouldn’t that part be easy? Earthlings would see the entire ring circumscribe the moon at all times. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 18, 2019, 6:31pm UTC](https://boards.straightdope.com/t/on-building-a-lunar-ringway/843407/24 "2019-11-18T18:31:47Z")
> [@tampora](#): > > If Earth’s tidal forces are a problem, couldn’t you position the ring so everywhere on the ring is equidistant from Earth at all times? Since the moon is tidally locked, shouldn’t that part be easy? Earthlings would see the entire ring circumscribe the moon at all times. An unattached ring will circle in the same plane. Since that plane is not rotating wrt Earth, then it will appear to turn around the Moon once a (lunar) month. It’s little different from a Foucault pendulum but keeping in mind that a day on the Moon lasts a month. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 19, 2019, 6:18pm UTC](https://boards.straightdope.com/t/on-building-a-lunar-ringway/843407/25 "2019-11-19T18:18:16Z")
> [@ftg](#): > > An unattached ring will circle in the same plane. Since that plane is not rotating wrt Earth, then it will appear to turn around the Moon once a (lunar) month. It’s little different from a Foucault pendulum but keeping in mind that a day on the Moon lasts a month. Things to realize at 5:14 in the morning. It turns around the Moon once per sidereal month. It is always in a fixed plane wrt the stars, not the Moon. [Previous page](https://boards.straightdope.com/t/on-building-a-lunar-ringway/843407.md?page=1)