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In the question Wind turbines in space

The user asks about using solar wind to rotate turbine like things in order to get energy. Most answers say that using them to get energy would not work because you would need to have a counter rotating turbine and it would be useless, but what if you used the solar wind in that way to accelerate a space station that created artificial gravity using centrifugal force? (I mean using solar wind from the initial acceleration up until the correct speed.) Would this be in any way more efficient that just simply strapping a few rockets onto it?

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    $\begingroup$ Not really, solar wind push will be tiny. Once you get your space station rotating, you don't need any additional push to keep it spinning. $\endgroup$
    – Alexander
    Apr 23, 2018 at 20:43
  • $\begingroup$ I am talking about the initial acceleration. You probably would not build the space station while it is spinning, at least in my mind. $\endgroup$
    – Sievert
    Apr 23, 2018 at 20:45
  • $\begingroup$ Your entire Space Station is a giant Crookes Radiometer. You just need a way to fine tune the speed of rotation, so you absorb just enough energy to compensate for any losses in angular momentum from other sources. $\endgroup$
    – cobaltduck
    Apr 23, 2018 at 20:47
  • $\begingroup$ It would be very impractical to use giant solar sails instead of compact rocket engines. What you can gain by using solar sails is reactionless acceleration, but for rotating space station you'll need to burn your engines just once. $\endgroup$
    – Alexander
    Apr 23, 2018 at 21:11
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    $\begingroup$ @cobaltduck The difference is there isn't a fixed axis for a space station. It's going to "roll away" from the star, not spin in place. $\endgroup$
    – Samuel
    Apr 23, 2018 at 21:38

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As other said, Solar sails for rotation are not practical, sail will need to be huge, the structure to hold it at correct angle will add to weight, and you will not need nearly as much power once the station is spinning (you will still need a bit to compensate for distortions from landing/launching ships, and people moving inside.

But here is another setup: The Shkadov thruster. A giant solar sail, "hovering" above a star as solar wind compensates for gravity pulling it to towards the star. The main effect is the thrust in the direction opposite of the sail, moving the star through space.

But the secondary effect is gravity on the outer (dark) side of the sail.

You can probably have a scaled-down setup where size of the sail is large enough to create gravity for a small station, but not enough to actually move the star.

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  • $\begingroup$ Hadn't heard of the Shkadov Thruster before - interesting, thanks. $\endgroup$
    – StephenG - Help Ukraine
    Apr 24, 2018 at 9:02
  • $\begingroup$ You will move the star, even if only slightly. To avoid it, make sail compensate only some % of gravity pull, and take the rest from pseudo-orbital motion. That way you will be moving it in direction that changes constantly, creating little oscillation but no net movement. $\endgroup$
    – Mołot
    Apr 24, 2018 at 12:03
  • $\begingroup$ Considering the question wants to spin up a space station for internal centrifugal gravity, building a massive structure to generate gravity for a space station seems unorthodox and more than slightly improbable. Solar-wind powered spin-up would be very, very slow & difficult, but seems more practical by comparison. While I like heroic technological applications, this doesn't seem most practical. Full marks for imagination. $\endgroup$
    – a4android
    Apr 24, 2018 at 13:04
  • $\begingroup$ Thank you. I very much like large, unheard of structures to do things that I ask about. I remember hearing about something like this, I even saw that picture of the website, but I never knew what it was and what it could do. Once again, thank you. Sidenote: The website also says that it has the capability to move the planets along with the star. Wouldn't the thruster create an artificial night and day on tidally locked planets as well? $\endgroup$
    – Sievert
    Apr 25, 2018 at 2:54

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