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Penumbra Station
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.

Quote:If your design needs a perfectly circular orbit, then maybe a snailshell configuration might be best. This consists of numerous objects sharing a single orbit, (basically an 'orbital band' in OA terminology)

Limiting the discussion to a single orbital band of formation flying, there's a problem with the energy-efficiency. Picture a cone right next to another cone. The surfaces of both of them are acting as radiators, giving off the station's heat into space. But being right next to its neighbor, a lot of the radiated heat will hit the neighbor's surface, thereby warming it and hurting its effectiveness (limiting the energy the station has access to). Because of this, "crowding" the orbital neighborhood defeats the point of penumbra stations. So as you approach a 2 on the Kardashev scale, it makes less and less sense.

But an orbital band leads to a fascinating revision of the concept. Instead of individual cone-shaped stations, it would be more efficient to make it a fully continuous ring with a cross-section which is a skinny isosceles triangle. It would be a wedge-shape that continues in a full circle around the sun. I believe this have slightly worse energy economics than a single penumbra station, but it would have other advantages.

As for the orientation issues...

The reason I see it as an issue is because I keep thinking of an Earth-sized station. For any small station (like the ISS size), fine-tuning attitude a few fractions of a degree over the course of a year is completely trivial. 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.

Messages In This Thread
Penumbra Station - by AlanSE - 05-25-2016, 12:43 PM
RE: Penumbra Station - by stevebowers - 05-26-2016, 07:11 AM
RE: Penumbra Station - by selden - 05-26-2016, 07:20 AM
RE: Penumbra Station - by stevebowers - 05-26-2016, 04:59 PM
RE: Penumbra Station - by selden - 05-26-2016, 07:59 PM
RE: Penumbra Station - by AlanSE - 05-27-2016, 01:22 PM
RE: Penumbra Station - by stevebowers - 05-28-2016, 01:51 AM
RE: Penumbra Station - by stevebowers - 05-28-2016, 02:07 AM
RE: Penumbra Station - by Drashner1 - 05-29-2016, 10:19 AM
RE: Penumbra Station - by AlanSE - 05-31-2016, 12:06 PM
RE: Penumbra Station - by stevebowers - 06-01-2016, 09:10 AM
RE: Penumbra Station - by iancampbell - 06-01-2016, 08:25 PM
RE: Penumbra Station - by AlanSE - 09-26-2016, 10:24 AM

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