Jeff Greason presented a radically new kind of power beaming. This will enable radical changes to drones, planes and eventually space launch. This presentation is at Space Access 2019.
Electric Sky will help people travel faster, cleaner, quieter, and more economically. They source power from the electrical grid, a reservoir of energy that’s less expensive than most any other, and has the potential to become the cleanest. They transport that energy up to the vehicle while in flight. As a result the vehicle can be lighter, faster, and less expensive to operate.
Electricity to work conversion is 2 to 3 times more efficient than fuel to work.
Size and cost of vehicles driven by energy storage.
If you can beam the power to the vehicle then the energy is massless and electricity costs half as much as fuel.
There has been work where a laser beam did not diffuse over short distances. There were offsetting effects that mitigated the diffusion.
Electric Sky has computer simulations using RF/Microwaves where the beam refocuses. This will allow for a small transmitter and a small receiver.
They have a very sparse array and a lot of this secret.
100-kilogram payload space launcher would need 100 Megawatt class power beamer according to Jeff. A quick check seems to indicate the need for 1.5 gigawatts for the 100-kilogram launcher.
Regular beam power has a spot size of 1.2 L/D. The baseline of the aperture in the new system is the same but the receiver can be made much sparser which makes it much cheaper.
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Beam it to a receiving antenna in space, convert it and beam it back to another antenna on earth. Either try a few geostationary satellites or a larger number of low orbiting satellites that can receive power from earth antennas, convert the power, beam the power to each other and beam it back down to the earth.
Well, NSF thread had a mention of bending airy beams around a horizon…
https://arxiv.org/abs/1801.09772
but that looks like for freespace optical, not RF, and a different kind of obstacle, so your mileage may vary…
Err, antenna orientation seems to be a problem for the receiver though, for an aircraft boost application (embedded in a tall tail would work I guess, if the beam fires from an array mounted on the control tower)(definitely not embedding in the runway). They can beam steer the transmitter (mentioned needing 3DoF)
I’ll also point out that if you can build a solar power sat complete with microwave transmitter then it would be much easier to just build an orbital microwave power relay to redirect the saharan power beam to melt… err I mean to power a Euro city.
Tesla’s famous broadcast power idea was to use the ionosphere to conduct electricity. Well conduct it through the ionosphere as one leg and back through the Earth as the other.
Of course this would mean you are pumping GW into the sky with anyone free to use it. Well “free after you’ve built a 30 km tower to reach the ionosphere”. So not THAT free.
With added unknown losses from whatever leak paths form naturally, or via innocent victims.
But he had a cool moustache. So any negative comments must be a conspiracy.
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LOL … “imagine beaming power from Sahara”, except for the curvature of Earth of course. Next a poster will reply that power might conceivably be bounced off the ionosphere. Like last-millennium amateur and military radio operators did all the time (but not to convey power!). Nah, again… the reflectivity is both poor and incoherent. Only at essentially useless wavelengths (useless for focussing) is it efficient.
As eluded to in the slide, the limit-of-beam at distance remains 1.2λ/D. Doesn’t matter if the transmitter is an ideal phased array, a parabolic reflector, or a beam focussed thru metamaterial constructs. Can’t beat 1.2λ/D.
Tom Craver’s use-case of much-nearer field gyrocraft launch power deliver is an interesting optimization. But that case is NOT the focus (pun intended) of this article’s paper.
Beam power could be used as a very long range transmission line. Imagine beaming power from the Sahara Desert to the rest of the world.
Also beam power could power space crafts.
Try Whispering gallery…
One possible use for beamed power over fairly short distances – boosting electric planes/jets up to take-off speed, maybe also helping them gain altitude. Planes could then cruise along at low power for relatively long distances. Especially good for short-haul air taxis, where nearly all power might be used for taking off. Recover a bit of power by gyro-coptering as give up altitude, then use that recovered energy for landing, maybe with another transmitted boost.
Let’s see: There are “Bessel beams”, which don’t drop off as inverse square, because there are a distribution of large beams that are focused converging at different distances, so that the energy density at the center of the beam stays constant until your most distant converging component starts diverging.
But those aren’t better than diffraction limited, they’re just weaker close up, they still drop off past the diffraction limit for the transmitting aperture. And most of the energy misses the target at all distances.
And there’s “near field”, but that’s only valid when the transmission distance is comparable to the wavelength, obviously inapplicable here.
At first I thought they were proposing some sort of self-focusing beam using the beam to alter the optical properties of the air to form a sort of free space optical wave guide. But that sort of thing tends to be unstable.
“Airy beam” was the clue: Looking it up, it’s just a special case of a Bessel beam, really.
So, not really impressed. This might let you get constant power out of a beamed power system, without adjusting the focal length as the target changes distance, but it isn’t going to improve efficiency, and it isn’t going to reduce the necessary transmitter size for a given receiver size. At best it might get you around the “sparse array” problem in antennas.
Which I guess isn’t nothing, given the need for a large transmitting aperture. But it isn’t any magic want that keeps EM radiation from diverging.