5 ms·

Wouldn't solar radiation pressure blow them all over the place?

• raducu 7y ago
  There would be a "unnatural" orbit where solar radiation pressure would cancel the mismatched orbit, I think. So the shades would stay in equilibrium in a bit higher solar orbit than their velocity would permit without the light pressure.
  • gbrown 7y ago
    I'm having trouble visualizing how this would be stable - from their reference frame (orbiting a Lagrange point), the pressure is coming unidirectionally. They'd be accelerated in one direction constantly, which seems like it couldn't possibly be stable.
    • raducu 7y ago
      Actually, you are right, I was talking as if the shades are just orbiting the Sun. L1 orbits do require station keeping. Perhaps you could cheat a bit by making the shades black or oscilating/slanting them a bit forward/rearwards as to do the station keeping with very little fuel? Or shaping them like a lense to direct most light away from Earth, but not to experience too much net force? Or they are just designed to be expendable?
      • gpm 7y ago
        For what it's worth, Wikipedia suggests making them shaped like a lens.
• jagger27 7y ago
  Yes. They need serious stationkeeping.
  • CydeWeys 7y ago
    Do they? It seems to me that it'd be a lot simpler to send up dumb sunshades, and then simply keep launching more as previous ones drift. The linked sunshades would only weigh a gram each. How much would a sunshade weigh if it had to be an entire spacecraft capable of stationkeeping? Many orders of magnitude more. You can't station-keep indefinitely anyway (your fuel will run out), so just launching lots more dumb sunshades seem like the more effective and cheaper solution.
    • beerandt 7y ago
      While I think x,y,z will be an issue, I think the bigger problem is orientation. Any sort of station keeping is going to add significant mass, complexity, and cost.
      • CydeWeys 7y ago
        Why does orientation matter? Just throw up enough dumb sunshades. It costs a lot more in station-keeping to get the orientation correct than to just let it be random. And keep in mind that, absent active station-keeping, you need a mix of many different orientations to block out the Sun throughout the year. And you're not going to perfectly remove any spin anyway.
        • beerandt 7y ago
          I agree that would be the smart way to do it, but that would at least double the scope, probably more, since orthogonal area is a cosine function. There's also oblique reflection to consider.
          • CydeWeys 7y ago
            Why do you assume that the linked paper hasn't already taken this into consideration? They know that they're basically just structured aluminum foil, weighing in at 1 gram each, and completely dumb; why would they be assuming orientation at all? The reasonable thing to do would be to assume random orientation (especially over time, i.e. rotation, and over the orbit).
• DennisP 7y ago
  Not as much as you'd think, because they're actually lenses. They just redirect the light away to miss Earth, rather than blocking it entirely.