4 ms·

Any aerospace engineering grad could design a flying car tomorrow if the energy source existed in such a density that would make it feasible. Beamed power?

pdelbarba 10y ago
How would this work through clouds? The water vapor would in theory block or scatter everything from UV to microwave radiation. Also, I don't want to be near a 1W laser/maser, and if our energy budget is 100kW, you'd need at least a 100,000W laser pointed at your tiny air taxi.
- jacquesm 10y ago
  That's called target practice. These guys do it all the time: https://www.youtube.com/watch?v=JtxwT6PQIw8 https://www.youtube.com/watch?v=JtxwT6PQIw8
nradov 10y ago
Impossible for safety reasons in populated areas. And even ignoring safety issues, the conversion efficiency on beamed power is so low as to make it uneconomical.
- stcredzero 10y ago
  I thought the conversion efficiency for microwaves was 80%.
  - nradov 10y ago
    Maybe in a kitchen microwave oven. You're not accounting for transmission path losses and receiver conversion efficiency.
    - stcredzero 10y ago
      Actually, I think that's a figure including transmission and receiver conversion efficiency, but it doesn't include path losses. That's still quite impressive, though. http://spectrum.ieee.org/energywise/green-tech/solar/japan-demoes-wireless-power-transmission-for-spacebased-solar-farms http://spectrum.ieee.org/energywise/green-tech/solar/japan-d...
      - nradov 10y ago
        That's for short range transmission to a fixed receiver. So not really relevant for powering aircraft.
        stcredzero 10y ago
        Such microwave systems have been proposed for solar power satellites. They have useful ranges up to 100's of miles.
andars 10y ago
Maybe, but unlikely. Lasers need line of sight and would generally be a bad idea at the power levels required (basically a weapon), and microwave power transmission requires large receiving apertures. Current "wireless charging" technologies are pretty much universally near field.

pdelbarba 10y ago

How would this work through clouds? The water vapor would in theory block or scatter everything from UV to microwave radiation. Also, I don't want to be near a 1W laser/maser, and if our energy budget is 100kW, you'd need at least a 100,000W laser pointed at your tiny air taxi.

jacquesm 10y ago
That's called target practice. These guys do it all the time: https://www.youtube.com/watch?v=JtxwT6PQIw8 https://www.youtube.com/watch?v=JtxwT6PQIw8

nradov 10y ago

Impossible for safety reasons in populated areas. And even ignoring safety issues, the conversion efficiency on beamed power is so low as to make it uneconomical.

stcredzero 10y ago
I thought the conversion efficiency for microwaves was 80%.
- nradov 10y ago
  Maybe in a kitchen microwave oven. You're not accounting for transmission path losses and receiver conversion efficiency.
  - stcredzero 10y ago
    Actually, I think that's a figure including transmission and receiver conversion efficiency, but it doesn't include path losses. That's still quite impressive, though. http://spectrum.ieee.org/energywise/green-tech/solar/japan-demoes-wireless-power-transmission-for-spacebased-solar-farms http://spectrum.ieee.org/energywise/green-tech/solar/japan-d...
    - nradov 10y ago
      That's for short range transmission to a fixed receiver. So not really relevant for powering aircraft.
      - stcredzero 10y ago
        Such microwave systems have been proposed for solar power satellites. They have useful ranges up to 100's of miles.

andars 10y ago

Maybe, but unlikely. Lasers need line of sight and would generally be a bad idea at the power levels required (basically a weapon), and microwave power transmission requires large receiving apertures. Current "wireless charging" technologies are pretty much universally near field.