4 ms·

The interesting thing about space-based solar power is that you do not need to direct the beam at the earth. You can also use it to beam energy to remote probe

by evgen 5y ago

The interesting thing about space-based solar power is that you do not need to direct the beam at the earth. You can also use it to beam energy to remote probes and robotic installations. If you want to mine asteroids you are better off beaming the energy from earth orbit than you are trying to capture solar on site. Sending the energy from earth makes it much easier to fix/replace the power generation satellite if your remote mission is going to depend on that for power generation.

blacksmith_tb 5y ago
Aiming a tight beam any significant distance would be tough though? I am sure you could hit the moon (not too far) but trying to push a solar sail or the PV on a probe in the outer solar system seems like a very small target (plus there are other bodies in between, sometimes...)
- evgen 5y ago
  It is not easy, but the energy density of that beam will vastly exceed sunlight at any significant distance. If you are no longer concerned with getting the beamed energy through a wet atmosphere you can also use better frequencies (e.g. visible light lasers or even higher frequencies that might have better margins when it comes to conversion losses.)
  - ben_w 5y ago
    The extra power density of the beam is only useful if you’re capturing a significant fraction of the beam at the far end, which implies both ends have big parabolic mirrors for whatever wavelength you’re using (because that’s the limiting factor in how tight you can focus photons), and if you’re doing that then you could skip the transmitter and point the receiver at the sun to greater effect — you’d need a 100m mirror on the transmitter to hit an Apollo-lander-sized receiver 1.3 light-seconds away — and if you’re concerned about different solar radiation flux at different points, you’re talking about beaming power over multiple light-minutes, main asteroid belt starting about 2 AU from the sun, about 8 light minutes from Earth at minimum. The distance is also large enough you need to be very certain about what’s going on outside your light cone.

by evgen 5y ago

blacksmith_tb 5y ago

Aiming a tight beam any significant distance would be tough though? I am sure you could hit the moon (not too far) but trying to push a solar sail or the PV on a probe in the outer solar system seems like a very small target (plus there are other bodies in between, sometimes...)

evgen 5y ago
It is not easy, but the energy density of that beam will vastly exceed sunlight at any significant distance. If you are no longer concerned with getting the beamed energy through a wet atmosphere you can also use better frequencies (e.g. visible light lasers or even higher frequencies that might have better margins when it comes to conversion losses.)
- ben_w 5y ago
  The extra power density of the beam is only useful if you’re capturing a significant fraction of the beam at the far end, which implies both ends have big parabolic mirrors for whatever wavelength you’re using (because that’s the limiting factor in how tight you can focus photons), and if you’re doing that then you could skip the transmitter and point the receiver at the sun to greater effect — you’d need a 100m mirror on the transmitter to hit an Apollo-lander-sized receiver 1.3 light-seconds away — and if you’re concerned about different solar radiation flux at different points, you’re talking about beaming power over multiple light-minutes, main asteroid belt starting about 2 AU from the sun, about 8 light minutes from Earth at minimum. The distance is also large enough you need to be very certain about what’s going on outside your light cone.