Astronomy / Space China Plans To Launch Artificial Moon Bright Enough to Replace City's Streetlights By 2020

cmdr underhill

C
Hmm, 500km orbit? Seems like a weird choice, why not GEO? It may save on electricity, but when you have a cloudy night I'm pretty sure street lighting will still be necessary.
 

Flimley

Flimley
Reminds me of the time the Russians were going to put into orbit a giant mirror. It was to illuminate disaster areas on the night time side of earth. ...for a fee no doubt.

Will these ‘moons’ lighting be omnidirectional ? If so the light pollution police will be going insane.

Flimley
 

Manticore

Manticore
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Shadowdancer

Shadowdancer
cmdr underhill said:
Hmm, 500km orbit? Seems like a weird choice, why not GEO?
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Because focusing light you don't have on such a small area is even more impossible at 50000km.

On the other hand, it would mean that the satellites wouldn't be moving at ridiculous speed and have only about an hour more of sunlight than the area they're trying to illuminate.

OK, let's do some napkin maths with numbers from [sedation needed]. We have around 1361W/m² total irradiance at the top of the atmosphere, not all of which is useful visible light, and want to light up 50km². Now let's say that we want 1W/m² of that to hit the ground and don't have an atmosphere to deal with that would eat a lot of that. We are looking at a perfect(!) mirror surface of around 37000m², or a circle of around 210m diameter. (Just for the heck of it, let's say that we could get 500W/m² of visible light hitting the ground out of that and we're well above 300m.) But of course that's only valid for the fraction of a second when the satellite is straight over the target and gets a lot worse as it continues in its orbit, to return in that perfect position... later to provide full output without inconvenient shadows. Ask Scott Manley how often that particular combination would happen when the target area is already in the dark, but the satellite is perfectly overhead in the very short window where it would still be in the light.

I love those obviously idiotic ideas.
 

Zak Gordon

Zak Gordon
I'm sure they are just trolling Trump, to see what reaction they can get from him ("I want the usa to build the first artificial moon, beat those chinese now!" etc).
 

lokvette

lokvette
Zak Gordon said:
I'm sure they are just trolling Trump, to see what reaction they can get from him ("I want the usa to build the first artificial moon, beat those chinese now!" etc).
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Is that after or before he builds his wall, sorry mods Ill stop there, as for the OP; its one of thosse I will belive it when I see it. :p
 
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