3 ms·

Optical isn't particularly power-inefficient, is it? The equivalent of an optical magnitude +5 star, in 500 km low orbit, is (if I didn't err) only 1 kilowatt o

Optical isn't particularly power-inefficient, is it? The equivalent of an optical magnitude +5 star, in 500 km low orbit, is (if I didn't err) only 1 kilowatt of isotropic power in a solar spectrum. Much less if it's a non-isotropic beam pointed towards earth. +5 is the brightest ~1,600 stars, likely similar to whatever any star tracker would be using.

sneak 1y ago
24kWh daily is a lot of energy. For reference, the current GPS satellites are 1000kg and transmit with 50W (1.2kWh daily). Here on the ground, for rough calculations, 50kWh is around 450kg in batteries alone. There might be lighter chemistries but this is just to get you in the ballpark. I think a 1kW light on 24/7 in orbit would need to be a very large vehicle (2-4x the size of the current Navstar satellites) with huge batteries and gigantic solar arrays. Falcon 9 can probably do it, FH definitely can. An RTG might work but those are out of fashion near Earth these days for obvious reasons. In any case it would be quite costly (you’d need lots) and its resistance to jamming would benefit your adversaries just as much as it would benefit you. Not to mention, the astronomers would hate you.
- perihelions 1y ago
  I don't know why you're worrying about batteries; LEO satellites spend only a few minutes in Earth's shadow at a time. The current model (v2 mini) Starlink satellite has 105 meter^2 solar arrays, and there's thousands of those orbiting already. That should be in the 10's of kilowatts on each Starlink. (Those solar arrays are so large they're already artificial stars of their own, though they're not designed to be). https://en.wikipedia.org/wiki/Starlink#v2_(initial_deployment) https://en.wikipedia.org/wiki/Starlink#v2_(initial_deploymen... And to repeat what I might have underemphasized: this is an estimate of isotropic power, if you were radiating uniformly in all 4pi directions.

sneak 1y ago

24kWh daily is a lot of energy. For reference, the current GPS satellites are 1000kg and transmit with 50W (1.2kWh daily). Here on the ground, for rough calculations, 50kWh is around 450kg in batteries alone. There might be lighter chemistries but this is just to get you in the ballpark. I think a 1kW light on 24/7 in orbit would need to be a very large vehicle (2-4x the size of the current Navstar satellites) with huge batteries and gigantic solar arrays. Falcon 9 can probably do it, FH definitely can. An RTG might work but those are out of fashion near Earth these days for obvious reasons. In any case it would be quite costly (you’d need lots) and its resistance to jamming would benefit your adversaries just as much as it would benefit you. Not to mention, the astronomers would hate you.

perihelions 1y ago
I don't know why you're worrying about batteries; LEO satellites spend only a few minutes in Earth's shadow at a time. The current model (v2 mini) Starlink satellite has 105 meter^2 solar arrays, and there's thousands of those orbiting already. That should be in the 10's of kilowatts on each Starlink. (Those solar arrays are so large they're already artificial stars of their own, though they're not designed to be). https://en.wikipedia.org/wiki/Starlink#v2_(initial_deployment) https://en.wikipedia.org/wiki/Starlink#v2_(initial_deploymen... And to repeat what I might have underemphasized: this is an estimate of isotropic power, if you were radiating uniformly in all 4pi directions.