What is the best axis of rotation for an Earth-orbiting rotating space station?

[T.C.]

If humans ever do build a rotating space station in Earth orbit, is there a scientific consensus on the best choice for the axis of rotation?

The default choice, I suppose, would be the axis perpendicular to the plane of orbit, but I can't think of any reason that axis would be "better" than any other (Unless maybe the angular momentum calculations are easier, perhaps?).

I cannot think of any reason why any axis would be better than any other for orbital stability, ease of docking, or crew vertigo.

However, I think there would be some advantage to choosing an axis of rotation which intersects the Sun. That orientation would result in the most natural daylight cycles for the crew. It would also make the solar panels easy to manage. And perhaps there are some design advantages which result from knowing that one side of the station will always be in shade (e.g. thermal generators). However, is such an axis feasible? You'd have to rotate the axis a full 360 degrees once per year. My sense is that you could do that easily through the minor adjustments you'll be doing anyway, but I really don't know.

Does anyone else have any thoughts on the matter?

-TC

[Sirrobert]

By 'rotating', I asuming you mean 'rotating to simulate gravity'?

[T.C.]

Yes, Sirrobert, that's what I mean. Thank you for pointing that out.

-TC

[ThermalShark]

I also think the best axis would be perpendicular to the orbital plane (assuming equatorial orbit), because that way the whole station gets equal sunlight. Some parts of the station getting more light than others is not good. This axis also ensures all windows gets an view to Earth, except those 'pointing' along the axis.

And an axis intersecting the Sun will result in daylight cycles in which one day lasts an year...

[KvickFlygarn87]

As for the "pointing one side away from the sun" part, that's called a sun-synchronous orbit and is not possible in KSP since all planets are perfectly spherical.

[SirusKing]

Why would you want windows? Solar panels, sure, but with a window, since you are spinning, would probably make you incredibly motion sick.

[T.C.]

You raise a good question, SirusKing: What environment is more comfortable -- one with spinning scenery, or one with no windows?

My instinct is that the spinning would be disturbing at first, but the astronauts would get used to it and prefer it to a windowless environment.

This is something that can easily be tested on the ground. It would not surprise me if NASA has already done experiments of this kind, and already has an answer. I just don't know what it is.

-TC

[Vanamonde]

Since you are talking about real stations rather than KSP ones, the thread has been moved to Science Labs.

[Nibb31]

Docking is easier on the orbital vector. That's how it's done in real life. They even rotate the ISS so that the docking ports face retrograde.

Approaching from above or below means that you are effectively in a different orbit with a different speed, which complicates things.

[T.C.]

Nibb31, I'm not sure the implications of your comment. Do you believe it would be best to choose an axis of rotation in the orbital plane so that, twice per orbit, the axis would align with the orbital vector and facilitate docking?

-TC

Edited May 26, 2014 by T.C.

[Sirrobert]

How fast would such a station have to rotate, to simulate 1G?

[softweir]

Nibb31, I'm not sure the implications of your comment. Do you believe it would be best to choose an axis of rotation in the orbital plane so that, twice per orbit, the axis would align with the orbital vector and facilitate docking?

-TC

So long as there was a docking port parallel to the prograde of the station then it doesn't matter - you could put docking ports on a non-rotating hub and keep them pointing for the convenience of ships. You wouldn't want to rotate them unless you could ensure their CoM was aligned with the axis of the station, as that would cause stresses on the dockin mechanism.

How fast would such a station have to rotate, to simulate 1G?

It depends on how big the station is. The image linked below shows (yellow line) how fast the station has to rotate to achieve 1g.

http://en.wikipedia.org/wiki/File:Calculated_rotation_speed_of_a_centrifuge.png

For a 10m centrifuge you need to spin at nauseating 9.5 rpm, for a 1000m centrifuge a comfortable 1 rpm will do.

[Chris P. Bacon]

This is something that can easily be tested on the ground. It would not surprise me if NASA has already done experiments of this kind...

-TC

They sure have!

[Capt. Hunt]

Also, you probably wouldn't need to simulate full Earth gravity. I'm sure NASA has more firm data on this, but from what I understand, Lunar gravity would probably be enough to counter the effects of microgravity on the astronauts.

[T.C.]

They sure have!

Thank you for posting that link. The video was fun to watch. To be clear, however, I wasn't wondering whether NASA had experimented with centrifugal force; I was wondering whether NASA had experimented with the effects of spinning scenery on human health. For instance, they could put someone in an ordinary room with no windows except one simulated window showing a distant Earth rotating once every 10 seconds. Over the course of a few days, would the subject get used to it, or would they continue to suffer ill effects? Earlier in this thread, SirusKing opined that windows in a spinning space station "would probably make you incredibly motion sick", but I'm not so sure.

-TC

[Camacha]

You raise a good question, SirusKing: What environment is more comfortable -- one with spinning scenery, or one with no windows?

I think the answer would be neither of those. You take out the real windows, which are annoying from a safety and engineering point of view anyway, and put in virtual ones. This provides the most natural environment for the occupants of the station.

[Chris P. Bacon]

Well I did a little more digging on the 'window' question, and came up with this paper http://adsabs.harvard.edu/full/2002ESASP.501..151H (explanation starts end of this page/beginning of next page on this topic) and it seems that having a window to the stationary(or rotating depending on your perspective) outside world.. vs blocked off windows or even complete darkness seems to have made no difference in adaptation for their experiment. It sounds like the largest factor in adapting to a rotating habitat is the Coriolis effect on the fluid in the inner ear, in that, anytime you turn your head, look up or down, or move along the radius of the habitat, in invokes a sensation of spinning or falling, which leads to motion sickness.