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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)

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

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.

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: !!!)

Here's a picture of the slide That's a real picture of a real laser.

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!)

Federated Republic of Sean @freakazoid

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"

Question about steering the beam.

You have to steer the beam in all three axes!

(Ed: seems similar to MIMO beamforming)

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"

Question about power source for a launcher.

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

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."

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."

Question about millimeter and shorter wavelengths.

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

@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.