5 ms·

> Powering cargo planes seems like a niche market that would be suitable FTA: Most designs aim to produce a beam kilometers wide so that any spacecraft, plane,

> Powering cargo planes seems like a niche market that would be suitable FTA: Most designs aim to produce a beam kilometers wide so that any spacecraft, plane, person, or bird that strays into it only receives a tiny—hopefully harmless—portion of the 2-gigawatt transmission 2 GW on a _single_ km² is 2kW per m², about twice what solar power provides. “Kilometers wide” could easily mean 10km², or 200W/m². ⇒ it will be difficult to get the power density to power an airplane, even if it’s only for flying at height.

robbiep 4y ago
I think your maths is off - there are 1m square metres in 1 sq kilometre, but 2000 kW in a GW, meaning approx 0.002 kW per square meter. Which kind of makes this whole thing a weird economic proposition. You’re beaming energy from space at a density that approximates solar insolation, and still have to build the collector and convert it back - wouldn’t it be easier to just collect the solar insolation?
- IanCal 4y ago
  > I think your maths is off - there are 1m square metres in 1 sq kilometre, but 2000 kW in a GW, meaning approx 0.002 kW per square meter. That's not right. There's 2000 kW in a MW, not GW. 2GW is 2e9W, so over 1e6,^2 that's 2e3W/m^2 or 2kW/m^2.
  - robbiep 4y ago
    Ahh thankyou for sorting me out. My apologies OP
- pencilguin 4y ago
  There are, in fact only 1000 kW in a MW, or 1,000,000 kW in a GW. Where is this factor of 2 coming from?
Schroedingersat 4y ago
There are already planes that can fly (and do nothing else useful) on 300W/m^2 Solar panels already have sufficient mass power density. There's a pretty big gap between the 10s of MW a jumbo needs and the 700m^2 of area it has. If you were willing to trade some flight speed you could increase wing area 5x or so, and maybe make it work in the 2-4kW/m^2 range if all of the photons were at your bandgap.
zinodaur 4y ago
It sounded like the reason for making it km wide was to avoid creating a gigawatt death laser - I assume if they were doing a flight assist thing they would send less total power and could concentrate it more
- speleding 4y ago
  There are probably more than a few people at the Department of Defence that get very exited about the prospect of having access to a death ray that could fry anyone we happen to have the coordinates for. Getting funding out of the military budget could speed this up immensely. So you went into green-tec to improve the world? Sigh.

robbiep 4y ago

I think your maths is off - there are 1m square metres in 1 sq kilometre, but 2000 kW in a GW, meaning approx 0.002 kW per square meter. Which kind of makes this whole thing a weird economic proposition. You’re beaming energy from space at a density that approximates solar insolation, and still have to build the collector and convert it back - wouldn’t it be easier to just collect the solar insolation?

IanCal 4y ago
> I think your maths is off - there are 1m square metres in 1 sq kilometre, but 2000 kW in a GW, meaning approx 0.002 kW per square meter. That's not right. There's 2000 kW in a MW, not GW. 2GW is 2e9W, so over 1e6,^2 that's 2e3W/m^2 or 2kW/m^2.
- robbiep 4y ago
  Ahh thankyou for sorting me out. My apologies OP
pencilguin 4y ago
There are, in fact only 1000 kW in a MW, or 1,000,000 kW in a GW. Where is this factor of 2 coming from?

Schroedingersat 4y ago

There are already planes that can fly (and do nothing else useful) on 300W/m^2 Solar panels already have sufficient mass power density. There's a pretty big gap between the 10s of MW a jumbo needs and the 700m^2 of area it has. If you were willing to trade some flight speed you could increase wing area 5x or so, and maybe make it work in the 2-4kW/m^2 range if all of the photons were at your bandgap.

zinodaur 4y ago

It sounded like the reason for making it km wide was to avoid creating a gigawatt death laser - I assume if they were doing a flight assist thing they would send less total power and could concentrate it more

speleding 4y ago
There are probably more than a few people at the Department of Defence that get very exited about the prospect of having access to a death ray that could fry anyone we happen to have the coordinates for. Getting funding out of the military budget could speed this up immensely. So you went into green-tec to improve the world? Sigh.