Hacker News Reader

Hacker News

Comment by other_herbert | Hacker News Reader

Parent Full thread

other_herbert

The key thing they aren't saying is how much power it took to "send" 800 watts 5.3 miles...

View on HN

They mentioned that it was 20% efficient at a closer distance.

So likely much lower than that.

Wow that's a long way from the proposals for sending GW of microwave power from satellites.

Laser power beaming from space could be useful at lower power levels than that, for example for powering aircraft.

But pretty close to powering drones from ground stations

Those sat to ground power sources use gallium arsenide switched FETs = synchronous rectification, avoiding the voltage drop of diodes has been tested on a small scale, the 10GW orbital 35% efficient solar arrays, maybe next week... Solar boilers, end to end, are more efficient than solar cells, but mechanical complexity(leaks, corrosion, worker avarice) made one US plan in the South West non viable. As we sit silicon-perovskite tandem solar cells will top out around 42-45% - unless Schockley is end runned? Ternary -??. A good lecture = https://www.youtube.com/watch?v=Ft0VJX0_Td0&t=2s&ab_channel=...

Solar thermal as well as solar-chemical systems have the problem of start-up.

PVs do not have any problem starting up, they produce less than full power with less than full illumination but they produce something and once the illumination is full they produce full power immediately.

Many solar thermal power plants are fired with natural gas in the morning to get them spun up to the point where they can take advantage of the solar energy. Without that they'd probably lose a few hours of production.

20% efficiency in terms of light -> electricity. A 50% laser efficiency (electricity -> light) is really good, possible for some diode lasers, if you pump a fiber laser with diodes to get a high quality beam for cutting materials or weapons purposes maybe you get 25%.

That demo would require about 45 kW of laser power with good beam quality which would be totally possible with a fiber laser

https://www.rp-photonics.com/wall_plug_efficiency.html

I was thinking of"how much is enough" so they can power 'instruments'. I am also thinking of 'how can we use this tech to revive space-instruments (the next generation of 'Voyagers' may be equipped with such receivers?)

I also wonder how difficult/impossible would it be, and the 'throughput'. Assuming that you want to recharge a recon drone (or the 'next generation of Voyagers flying in space) that flies over XYZ area/country/etc. Would it take 1sec or 10seconds 'of beam', and the accuracy/waste/total amount one would have to 'dispense' in order to give that drone the X seconds of 'juice' to keep it running for 1000x X seconds of flight duration. And what about clouds/mist/rain/snow/birds/etc.

'Infinite energy' for a drone (I mean no dependency to come down to refuel) is a game changer.

Would that work with 'instruments buried underground? And at what depth? ('War of the worlds' scenario). Could someone bury a device, with only the receiver protruding from the ground, with a battery to keep it alive, and waiting to be activated by a satellite passing by giving it the "10 seconds beam" to fully charge it and.. (I am thinking of the recent drone-related incidents/attacks within Russia and Iran)(if you park a drone for 10 months, its battery will deplete, right?)(I don't have a drone, but batteries are batteries).

A second thought on the matter, can one 'program' the light to be also transferring data? Park the drones in <insert foreign territory>. No programming. In the middle of nowhere (no 4G-5G). You fly a satellite over it, beam down the 'juice' (together with the instructions - no interception of the transfer is possible). Someone finds it 'before', they only get the hardware but no info/intel.

"The possibilities are endless" (and so are the nightmares)

Reply on news.ycombinator.com