Penumbra Station

[stevebowers]

Reading the last batch of comments here, I see some very valuable feedback. First, let me cover some of the sun-shading physics, as per stevebowers comments.

Why 1 degree? Because that's roughly the angle that the sun occupies in our field of vision. That's the entire point. The "dark" portions of the station, which radiate heat, will see absolutely no light from the sun. That means that your radiator is exposed to a perfectly cold vacuum, as if it were in the middle of space.

Get closer to the sun, and this angle increases (and the penumbra cone becomes a fatter shape). Go to a larger radius, and the angle decreases. At every given radius, the taper angle of the penumbra station is proportional to the angle that the sun occupies in the field of vision at that radius. A penumbra station is also the coldest possible temperature that something can be at that radius, given a constant efficiency of their energy conversion systems from the sun-facing side. The maximum energy the station can consume is limited by the Carnot efficiency, which is hyper-sensitive to the temperature of their heat reservoir.

I see. Ingenious. No wasted energy.

For a large station, I don't think you even need gyroscopes per-se (like Island Three, that's a big gyroscope after all). You just need a superstructure that is tidally-locked, and then some counterweights that can move in the opposite direction of what you need. Gyroscopes (momentum wheels) would still work, and so would a number of technologies, so it's just hard to say what would be best.

Orbital rings could act as counterweights; these are masses of magnetic material that orbit the centre of gravity of an object, constrained by magnetic tracks. It should be fairly easy to add and subtract angular momentum from a structure that includes an orbital ring somewhere in its design.

[iancampbell]

To improve tidal locking if that's what you want: Incorporate a long tether (maybe 5x the length of the station) with a big mass at the end, on the side facing the star. Either a big dumb mass, or perhaps put your transit port there with a maglev line running towards the inhabited portion. The latter configuration would probably improve safety, because incoming ships wouldn't be coming close to inhabited and other important areas.

Naturally, this would only work in an orbit that's as close as possible to circular.

[AlanSE]

To improve tidal locking if that's what you want: Incorporate a long tether (maybe 5x the length of the station) with a big mass at the end, on the side facing the star. Either a big dumb mass, or perhaps put your transit port there with a maglev line running towards the inhabited portion.

This is almost exactly what I had imagined. I was musing about the idea that the far-side would have a large tether and counter-mass attached. There might be some stability arguments for far-side versus near-side, but they are probably unimportant compared with logistical concerns.