[greedo]

The amount of fuel needed to become airborne is a fraction of the amount of fuel needed to achieve cruising altitude. So using a catapult would only save a puny amount of fuel, as well as add risk to takeoffs.

Plus, if you actually watch a video of a modern catapult launch, you'd realize that you're speaking out of your ass. Going from 0-170mph (the rotation speed of an A320), in a short amount of space is going to impart huge G forces on both the aircraft as well as the crew and passengers. Catapults also fail, and a "cold cat" on an airline sized plane (without zero/zero ejection seats for everyone) means a mass fatality event.

Man, HN is just full of people suffering from Dunning-Kruger.

[hef19898]

When you think about it, that attitude explains a lot of VC funding in certain companies.

[standardUser]

I'm not sure why you think this needs to be exactly like an aircraft carrier, it does not. Why in the world would it need a shorter amount of space? An electric aircraft with heavy batteries could be brought up to speed with the same acceleration as current aircraft, and all of that energy used is weight not needed for the remainder of the ascent and flight. I have no idea how much energy could be saved, but it's not nothing.

If that's not good enough for you, here's what fucking Airbus has to say:

"In the report, Airbus explains that the initial power required for a passenger plane to take-off is only needed for a brief part of the total flight. This therefore poses an opportunity for a ground-based device to provide the propulsion needed and free the plane of its additional burden. With this in mind, the engineers at Airbus came up with an idea dubbed "eco-climb" which appears to draw inspiration from the catapult-assisted take-off system utilized on aircraft carriers."

Dunning-Kruger indeed.

[greedo]

Catapults have almost always been used to minimize takeoff space, or eliminate it entirely (drone launches). The tradeoffs in using a catapult are stress on the airframe, heavier planes due to hardening the airframe to mitigate this stress, as well as an uncomfortable experience for the passengers. There's also the risk of cold cats as I mentioned. You seem to be ignoring these issues entirely.

Airbus's "Eco Climb" was greenwashing at its finest, and despite them touting it in 2012, here we are over a decade later without ANYONE doing something this dumb. The comment above misses out on some basic aircraft fundamentals. One, most of the energy used by an aircraft is in flight, not in rolling off a runway. So the amount of energy saved compared to the added complexity makes it a dumb idea.

Sure, you could make the catapult the length of a runway, mitigating the G force etc. Then you have a Rube Goldberg device that needs to accommodate every aircraft that uses the runway. And this device can't interfere with landing or taxiing either. Then you need to get this device adopted by most airports, otherwise you've immediately gimped your airliner when it lands somewhere that lacks this device.

This idea reminds me of crap I used to read in Popular Mechanics and Popular Science (RIP) that had great ideas that were never developed because their underlying assumptions didn't match with the real world.

You might as well off up the idea of using a blimp/dirigible to lift the airliner up to altitude then drop it off...

Oh and I believe referring to the Airbus quote is an appeal to authority? Considering that Airbus design flaws killed a lot of people, maybe reconsider?

[hef19898]

Yes, Dunning-Kruger indeed. Or have seen any real world use of said catapult?

Engineers come up with all kinds of ideas all the time. Most don't result in more than some PR piece, like the one you quoted above...