Comment by zaarn
8 years ago
Solar light isn't that strong once you go beyond mars.
Earth gets 1400 W/m^2, at Saturn only 16 W/m^2 and on Neptune maybe 1.5 W if you get lucky.
60 days of continous harvesting, assuming the spacecraft doesn't use any power (which is not true in reality), is about 2 kWh at Neptune. Not that much. Saturn would be 23 kWh.
Yuck, that’s miserable.
It's the inverse square law that bites you here as the same amount of energy gets stretched out into a larger sphere as it travels outwards (at earth the energy is 1.4kW for a square meter, when going outwards, this square meter gets stretched)
Double the distance and you get 1/4th the energy.
Saturn is 9AU or 9 times as far as earth; 1/81th the energy. (1400 / 9^2 = 17, so math checks out; roughly)
We're quite lucky to be close enough for solar energy to be a viable source of energy.
[*]: https://en.wikipedia.org/wiki/Inverse-square_law
> We're quite lucky to be close enough for solar energy to be a viable source of energy.
If solar energy were not viable, this form would not exist.
2 replies →