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I couldn't read the article, but I presume it talks about transmitting power from space to the ground. My perennial question: what technology could transmit mas

I couldn't read the article, but I presume it talks about transmitting power from space to the ground. My perennial question: what technology could transmit massive amounts of power that couldn't easily be converted to a weapon? And if these solar stations could become space weapons, why would one major country allow another to launch and control them?

DennisP 4y ago
Solar power satellites would be in geosynchronous orbit. Even if we wanted a beam tight enough to be used as a weapon, that'd be very difficult to achieve. The current designs would have a footprint of several square miles. Birds could fly through the beam without harm. And that's with a phased array transmitter that uses a reference signal from the ground. If it somehow repoints somewhere without the ground transmitter, the beam would spread out much more than that. (source: the book The Case for Space Solar Power)
- dtgriscom 4y ago
  I agree that a "beam of instant death" would be unlikely due to the probable low power density. But, couldn't it be high enough to cause significant heating and health issues? As some anecdata, I remember a decades-ago report that said it would be safe to graze cattle under the receiving antennas, which suggests both that a) it wouldn't be safe for cattle above the receiving antennas, and b) it wouldn't be safe for humans even under the receiving antennas.
- ben_w 4y ago
  Putting them in GEO means that if you have more than 3 in total, you have to ask "can a malicious actor make more than one beam focus on a chosen target?" And you do have to care about malicious actors, not just accidents, on this scale. You can only guarantee to avoid this if you put them in lower orbits so that no more than one is over anyone's horizon at any moment (bonus: saving on antenna mass), and with a phased array that's basically fine; but the lower they get, the more often they're in Earth's shadow. (I really need to blog this with pictures, I don't want a repeat of last time this came up).
  - DennisP 4y ago
    Seems pretty clear. That's a decent point. According to the book, the beam spreads out a lot if you don't have the ground signal, but it didn't quantify that. And there's always the possibility of some sort of covert action putting a transmitter in the target area. If the malicious actor is hacking the satellites that power the victim's country, then the repoint gets a double whammy by cutting off power to the areas it was supposed to go.

DennisP 4y ago

Solar power satellites would be in geosynchronous orbit. Even if we wanted a beam tight enough to be used as a weapon, that'd be very difficult to achieve. The current designs would have a footprint of several square miles. Birds could fly through the beam without harm. And that's with a phased array transmitter that uses a reference signal from the ground. If it somehow repoints somewhere without the ground transmitter, the beam would spread out much more than that. (source: the book The Case for Space Solar Power)

dtgriscom 4y ago
I agree that a "beam of instant death" would be unlikely due to the probable low power density. But, couldn't it be high enough to cause significant heating and health issues? As some anecdata, I remember a decades-ago report that said it would be safe to graze cattle under the receiving antennas, which suggests both that a) it wouldn't be safe for cattle above the receiving antennas, and b) it wouldn't be safe for humans even under the receiving antennas.
ben_w 4y ago
Putting them in GEO means that if you have more than 3 in total, you have to ask "can a malicious actor make more than one beam focus on a chosen target?" And you do have to care about malicious actors, not just accidents, on this scale. You can only guarantee to avoid this if you put them in lower orbits so that no more than one is over anyone's horizon at any moment (bonus: saving on antenna mass), and with a phased array that's basically fine; but the lower they get, the more often they're in Earth's shadow. (I really need to blog this with pictures, I don't want a repeat of last time this came up).
- DennisP 4y ago
  Seems pretty clear. That's a decent point. According to the book, the beam spreads out a lot if you don't have the ground signal, but it didn't quantify that. And there's always the possibility of some sort of covert action putting a transmitter in the target area. If the malicious actor is hacking the satellites that power the victim's country, then the repoint gets a double whammy by cutting off power to the areas it was supposed to go.