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Comment by reitzensteinm | Hacker News Reader

The author replaced the 25 tonnes of fuel a 737 carries with 25 tonnes of batteries, which is generous towards the electric jet (as the fuel burns during the trip).

Edit: It looks like you deleted the post I was replying to, but a 737 with 72 tonnes of MTOW does not carry just 17 tonnes of fuel; you can easily look up the product matrix on Wikipedia.

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The author doesn't really state that he did that, but I ran the numbers, and it seems he's doing that indeed. Not sure how he came to the conclusion that 25T fuel is in the 737, as that doesn't seem to be the case. He still didn't consider the engines that would be almost completely gone weightwise, and of course the main point stands -- the 737 is a specific model, with specific tradeoffs, to handle specific cost variables, including engines and fuel. If one is considering a new design, with drastically different variables, different cost of fuel (almost 1/5th or less) different weight distribution, different acceleration capabilities, different aerodynamics (no more bulky engines at the wings), different takeoff strategies, then this kind of "what if I flipped the fuel on the 737 for a battery" approach cannot be used as proof that an idea is "ridiculous". The author comes to the fight extremely underprepared, and honestly if we all reasoned like that we'd still be in caves. I'm all for calling Elon out on things he's more vulnerable on, but the author tips his hand with shoddy work like this.

I don't think the author is saying the plane has to be like a 737 with the batteries removed; the argument is more like: a 737 with battery replacement is an order of magnitude away from being viable, so the design is going to have to close that gap, and that's a pretty tall order.

It's a fairly lazy argument, but also one that effectively illustrates the challenge.

>The author replaced the 25 tonnes of fuel a 737 carries with 25 tonnes of batteries, which is...

...disingenuous because that's a 35% battery mass fraction, and Musk has already revealed that he's assuming a 70-80% battery mass fraction at 400 Wh/kg[1].

So this 'argument' boils down to, "some numbers that Elon says don't work... don't work."

[1] https://www.youtube.com/watch?v=yx3auTD85Fw

Also note that landing a 737 with a full load of fuel is... not normal.

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