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by willyt 4679 days ago
Why would you put solar panels up there? Why couldn't you just focus the energy into a beam and point it towards earth like space based mirrors for one of these solar power stations[0] where sunlight is focused on a 'boiler' which generates steam for a conventional turbine. I've no idea if the physics works out but i'd be interested to hear from someone who does. [0] http://en.m.wikipedia.org/wiki/PS20_solar_power_tower
2 comments
Gravityloss 4679 days ago
Quite unintuitively, you can't really focus light from the sun to a long distance, since the sun is not a point source.

Basically, you can't exceed the power per steradian of the sun with mirrors. So you would have to fill a large portion of the receiving end's sky to transmit any real power. Which means the mirrors would have to be really close (like they are in heliostats) or if they're far away, they would have to be really huge.

Does not work.

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schiffern 4679 days ago
>Basically, you can't exceed the power per steradian of the sun with mirrors.

This is something I've wondered about. It seems like one should be able to make a counterexample by focusing an enormous area on a tiny one. Is it just because due to "fuzzy focus," the concentrated focus volume unavoidably grows as the mirror size grows?

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tripzilch 4679 days ago
well, first thing that comes to mind is, with that anyone that builds a device that focuses a large amount of solar energy into a tight beam aimed at the Earth, I'll have a hard time believing that's going to be used for some benevolent energy-harvesting purpose.

And even if it is intended to, what will be the accuracy of this beam? what's to say some orbital junk won't crash into it and "oops" scribble a nice kilometres-wide Lissajous figure of scorched Earth onto our planet, like a hit and run graffiti tag?

Even if, according to WP, NASA is "a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science", the US government has proven itself rather incapable of keeping itself in check, so the odds of it going to turn into "hey we could also turn it into a gigantic solar death ray space weapon", somewhere, at some point given its life cycle, seem pretty high to me?

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zxcdw 4679 days ago
I'd be surprised if most didn't think of this at some point when reading the original article, let alone when talking about concentrating huge energies from space in general.

That said, perhaps people don't consider it feasible, as in, "not in MY world". Sounds dystopian sci-fi and so on.

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