Jeff Greason, Chairman of the Tau Zero Foundation (formerly of X-Cor, formerly of Rotary Rocket) is talking about Electric Sky: A Long-Range Wireless Power Transmission System Enabling Orbital Launch Vehicles, with Terrestrial Commerical Applications

Questions Driving Electric Sky"
* Is there any way to bring the cost of a passenger ticket to orbit below $10,000?
* Is there any technology which would allow for high speed point-to-point transport which is both faster and cheaper than subsonic aviation?
* Is there one technology that might do both things?

(Jeff is speaking as an employee of Electric Sky, I think, not as chairperson of Tau Zero)

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The Promise of Beams
* Size and cost of vehicles driven by energy storage
* Mature operating cost driven by the price of energy
* If you can beam the power to the vehicle, then
- The energy is massless
- Electricity costs about half as much as fuel
- Electricity-to-work conversion is 2-3 times more efficient than fuel-to-work

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Table showing different wavelengths, cost per watt, area of transmitter, and receiver. UHF is super cheap and the receivers are efficient, but the area is HUGE.

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There are other practical "beam like" solutions to Maxwell's equations!

A class of Airy solutions in particular has relevance for power beams (Chremmos 2011)

Tight focus a long way from the transmitter AND the beam in the middle is diffuse, which greatly reduces worries about accidental exposure.

(Ed: !!!)

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Next slide: 915 MHz, 740km transmission (i.e. satellite).

Following slide: 915 MHz, 125 km transmission. Sparse array for launch vehicle first stage, 40% of power in 12m radius.

(Ed: Holy shit this is exciting!)

Lot of other markets for beamed power: UAVs, UAMs (flying cars), electric aircraft (propeller and eJets)
* Exploring a range of frequencies
* Receivers are smaller, concerns over accidental beam exposure higher
* Looks doable but still work to be done

For meter-to-50m ranges
* Spinoff beam receiver work
* Extends inductive near field coupling
* Pursuing that as early revenue
* Wireless power at kW scale
* Breadboarding in the lab now (picture of a literal breadboard with LEDs)

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21st century propulsion

100 years ago, people weren't sure what to do with electricity. "Light without smoke"

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Question about steering the beam.

You have to steer the beam in all three axes!

(Ed: seems similar to MIMO beamforming)

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Dave Weinshenker asked about what he can say about their transmitter array.

Jeff: "It's a very sparse array, but that's all I can say, because not everything has been filed in a patent yet"

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Question about power source for a launcher.

A: "It's in the 100 megawatt class."

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Question about space-based solar power, which made Jeff giggle.

Jeff: "I don't think anyone else is working on this technique. I think there will be challenges to adapt it to space-based solar."

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Question about how far you can place the focus. "Can you place a spot on the moon from the earth?"

A: "I haven't simulated yet". Looking at applications nearer to Earth "unless somebody pays me."

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Question about millimeter and shorter wavelengths.

Jeff: very hard to do anything at the receiver with those wavelengths other than make something hot.

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@freakazoid the question really should be what happens in sub-mhz wavelengths. a hot enough wave at long wavelengths (1mhz = 300 meters) could provide both energy as well as provide an assist for propulsion.
@freakazoid I assume this company is talking about beaming power as a propulsion method, right? longer wavelength is more efficient for that.

@kaniini Yes but the wavelength cannot be significantly larger than the vehicle if you want any of the energy transferred to the vehicle in any fashion.

@kaniini Longer wavelengths means bigger transmitters and receivers.

They're not talking about using photon pressure for propulsion if that's what you mean.

@freakazoid nah i am talking EM, i guess 900mhz provides a good balance between efficiency and receiver size

@kaniini Yeah the table said 97% receiver efficiency, which of course needs to be multiplied by whatever amount of the energy is actually hitting your antenna array.

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