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Comment by anonymousiam | Hacker News Reader

The lightning "strike" mentioned in the article was probably not a direct hit. Nothing can really survive >30kA of current. I recall concerns from Boeing engineers when they switched to carbon fiber fuselages, that a strike would be far more serious than before, with Aluminum fuselages.

https://www.weather.gov/safety/lightning-power

https://aviation.stackexchange.com/questions/35493/are-carbo...

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> I recall concerns from Boeing engineers when they switched to carbon fiber fuselages, that a strike would be far more serious than before, with Aluminum fuselages.

It's a serious problem for carbon-fiber wind turbine blades. Fiberglas is an insulator, and doesn't have lighting problems. Aluminum is a good conductor, and doesn't have lighting problems as long as there's a good a path to ground through the hub. But carbon fiber is a resistor, so conducting a lightning strike generates heat. Some copper or aluminum wire has to go into the turbine blades to bypass this.

I believe Boeing puts a conductive mesh into the carbon fiber fuselages, but there is still a trade between conductive capacity and weight. Guess which one wins?

There's 2 kinds of CG and there's long-line-induced EM.

Ordinary -CG is 30 kA / 30 C / energy of 1 t of TNT. +CG is 10x that.

Direct hits are survived all the time by lightning rods for the past 275 years.

Long, unshielded lines of any sort can induce massive transient voltage transients (low current) that need to be protected with appropriate TVS circuits that will wear more in storm-prone areas. EMI from nearby lightning in unshielded computing systems with antennas or even without antennas can also be a factor.

A lightning rod is copper the thickness of your thumb. Anything thinner would melt. Lightning rods are expensive because thick pieces of copper cost a lot.

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