Hacker News Reader

Comment by Nokinside | Hacker News Reader

Energy density of jet fuel and gasoline is something like 45-46 MJ/kg. All rechargeable lithium-whatever batteries have less than MJ/kg.

Turboprops are efficient and reliable. They have good power-to-weight ratio. Currently electric motors are good only for things like gliders that need relatively little power.

View on HN

This link (recently on HN) provides an interesting analysis of the options: http://spectrum.ieee.org/aerospace/aviation/how-i-designed-a...

It seems like a fuel cell could be a viable option in the not-too-distant future, but still comes with a good number of trade-offs...

If self-flying taxi average flight times are 15 min, does this matter?

It does if you want to operate your self-flying taxi in an economically sound manner. All the time that it is on the ground it is not making money. Which means you'll be charging it when the number of requested rides is low, so you'll need to make a number (possibly quite a large number) of 15 minute rides before you get to recharge.

15 minute flight, 15 minute back to depot, 5 minute battery swap, charge batteries at the depot.

Blimps would also be viable. You can significantly reduce the required energy to get them to move

I love blimps. Even more so the semi-rigid ones. We can even get some of them solar powered now.

However, have we solved all the mooring requirements? I can't envision blimps used by individuals until they can self-moor or something.

You could hold the hydrogen or helium as liquid prior and post use. There's a bunch of stuff we would have to figure out to make it work, but it doesn't seem entirely impractical.

Yes, I know, jet fuel is one of the most energy dense things out there. But the article talks endlessly about electric power being the key to a self flying car, so I assumed the whole discussion was contingent on that being practical.

Reply on news.ycombinator.com