Fermi estimation says…

The internet says the energy of a cloud to earth lightning strike is 10^9 joules. A gallon of jet fuel contains about 10^8 joules of energy. A strike would provide the equivalent of 10 gallons of fuel.

A 737 would need to be struck at least once every 10 miles to keep going.

Sadly, that lightning power number is for cloud to earth, a cloud to airplane is going to be far less. If you try to extract too much power from the bolt it will just go around you.

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Meta comment: I like the breadth of this comment's peers. We have this one about the scale of energy, one commenting that it doesn't help range because you can't rely on it, one about the disparity of power between charging and discharging, and one about avoiding complexity and mass in airplanes. All good points. I hope in 12 months we hear back from the lunatic that ignores them and makes a functioning prototype.

This is essentially impossible.

Yes a single lightning strike contains roughly a similar order of magnitude of energy as an entire charged flight battery would but it is delivered in microseconds. That comes out to hundreds of terawatts of power while in comparison the new Tesla supercharger charges at an incredibly high rate of hundreds of kW. That's 1 Million times lower than lightning! There is no substance on earth that can absorb and store energy at that power rating.

On top of all of that, even if you could get it to work it would be such an unreliable source of energy that it would never make any economical sense to deploy on plane if you could just capture it on the ground and charge the plane from there.

They have static discharge wicks to let the lightning pass through. Newer carbon aircraft integrate copper mesh to conduct the current through the hull. The aircraft must be flyable following a strike, the ones I worked on were basically only able to protect the crew and land safely in that event. After that, it was expected the aircraft would be fully torn down, inspected, and rebuilt.

The idea that a lightning bolt could be used as a power up source has been thoroughly debunked by myself and others in this thread already, but I thought I’d take another angle in response, just using electricity in general.

A single GE90 aircraft jet engine used in the 777 is up to 111,000 horsepower[0]. So for the Boeing 777, that’s ~220,000HP. Converting horsepower to megawatts, that’s 164MW of power during takeoff (and approximately half that during flight). There’s approximately 500-1000 B777s (very rough, but educated guess) in the air at any given moment during the day. That’s 82.5 gigawatts of power just for the 777 flights alone, not counting all the other commercial aircraft in use.

So how much is 82.5GW?

> The Palo Verde nuclear power plant in Arizona is the largest nuclear power plant in the United states with three reactors and a total electricity generating capacity1 of about 3,937 MW.

So 40+ of the largest nuclear power plants in the US?

> average wind turbines produce 1.5MW of power at 100% efficiency

So 55,000 wind turbines at minimum? Better hope it’s windy!

Flipping it another way:

> an average LCD TV uses 200W of power

So in other words, turn off 400M TVs around the globe to offset the power needs of up to just 1,000 planes.

Now finally...

ignoring the electricity generation needs, let’s talk about just battery storage on the plane itself. A typical 18650 (the battery that is commonly used to make large cells, for example in your electric cars) is something like 9W of power. So you’d need something like almost 20,000,000 batteries just for a short flight. Each 18650 weighs about 45g (not including wiring harnesses and safety gear). That’s 200,000 pounds of batteries. The batteries alone for a short flight is multiples of the weight needed in fuel for an international flight.

[0] https://www.bangaloreaviation.com/2009/10/worlds-largest-air...

Utilizing the energy in lightning is hard, the voltage involved are hard to contain without damaging equipment and you can't charge batteries directly from the strike so it must be buffered somewhere.

People say it's already useless on solid ground. I suppose we can forget that on moving objects.

That said I wonder if helium filled balloons with extremely capacitors could absorb some of the voltage difference in the atmosphere and act as mini batteries.

Some people already tap into atmospheric voltage near ground with drones carrying long wires.

I'm not sure about if its possible, but in the context of where this plane is flying, there is only lightning once or twice per year.

Even if you could, how could that even be useful?