And accept the constantly shifting shadows of night life in the city.
Somewhere above LEO but below GSO will give you an orbital period of several hours. It should only take a few satellites for near-continuous coverage.
You can also play around with eccentricity and inclination to optimize the orbit.
Like a death ray? 1920’s style?
This is basically the equivalent of their proposal to put in a train across the Bering Straits to connect China to the US, or, maybe a better example is their proposed rail line linking central China to London so that you could trans-ship cargoes in a few weeks as opposed to a several weeks by boat. I wouldn’t put any sort of great CT on the reasons why the CCP is doing this…if they wanted to just put up a spy satellite they would, basically, just put one up. This is part of their continual efforts to convince the west (especially western journalists, and their own people) that China is great and the leader of the world in all things cool.
I saw a video from Scott Manley going over some of the high level technical details of this, and it’s basically what others have said…because of the low orbit it would be basically useless as anything but a fast moving bright light in the sky. You could, of course, put a satellite up at a much higher, geosynchronous orbit and get some utility out of the concept, but it would have to be pretty big and you’d have to either constantly refuel the thing or it would become defunct after a few years.
It should be mentioned that an orbital “sun gun” would need to be a lot bigger than 100 meters to be useful as a weapon. A solar focuser can’t increase the effective temperature of the Sun, and so looking at the mirror would be (even assuming perfect efficiencies) like looking at the surface of the Sun. To burn things with that, you’d need the “second sun” to have a significantly greater angular size than the Sun, which means that a mirror a few hundred kilometers up would need to be several kilometers across.
Just drop the damn thing on your enemy’s city.
Good point, Oberth was a rocket visionary, but apparently didn’t appreciate the finer points of thermodynamics/etendue.
I’m not sure if I’m reading this right. Are you saying one of these things in geosynchronous orbit would need constantly refueling? Why would that be?
Not sure about constantly, but yeah, you’d need to refuel it periodically to keep it in it’s proper orbit. You are talking about a giant mirror reflecting down on a specific point on earth, at least at night presumably, so you are going to have solar pressure alone pushing on it (not all that much, true, but not zero either). You are also going to need to do some maneuvering just to keep it’s orientation correct to hit your target. The thing is going to have to be pretty big as well…I think you will basically get half a degree of arc or less out of something at geosynchronous orbit, so you can do the math, but my wag is you are talking about a mirror of a few hundred meters at least.
There would be all sorts of other issues with this, and I don’t think it’s feasible btw, but if the Chinese were really serious about this I’d think this is where they would put it to actually do what they are talking about doing, i.e. lighting one of their northern cities at night to save electricity or whatever non-sense they are using to justify this scheme.
yes