[bprater]

Batteries are heavy. Teslas are very heavy cars. Aircraft are extraordinary light, compared to ground-based vehicles. Even in flight, large aircraft will burn a lot of their fuel during ascent. Electric powered aircraft get to drag around the heavy used batteries until recharge. And then you have to figure out how to refuel. Until a significant change in battery density, electric planes aren't going to be a thing.

[thebruce87m]

Would you class them as very heavy? Trying to find some figures to compare: https://www.quora.com/Is-a-Tesla-heavier-than-an-ICE-car-of-...

Tesla Model S - Curb weight 4,647 lbs Audi A8 - Curb weight 4,751 lbs BMW 7 series - Curb weight 4,244 - 4,848 lbs

Tesla Model 3 - Curb weight 3,627 to 4,072 lbs Audi A4 - Curb weight 3,450 to 3,627 lbs BMW 3 series - 3,582 to 4,010 lbs

[4death4]

Compare a Bolt (~3700 lbs) to a Fit (~2600 lbs).

[k4rli]

A luxury car usually weighs more due to higher quality materials, larger displacement, more overall modules and wiring. Tesla is an ecobox made with cheap materials so majority of its weight is the battery.

[GauntletWizard]

Sure, when you're comparing them to German tanks, they look pretty normal weight. How about a Kia? The K5 is comparable to a model 3, if not as nice, and it maxes out at 3,534 lbs

[scythe]

>Even in flight, large aircraft will burn a lot of their fuel during ascent.

I've been wondering if this offers any escape. Suppose that you have a power supply from the ground during the initial acceleration, and the final cruising velocity is not much higher. Or just build a huge ramp.

It sounds like a joke at first, but it might not be impossible. You just need some kind of reverse linear induction motor that doesn't require much weight on the plane side. Perhaps the fuselage is the magnet? If the takeoff acceleration is 2g, you need a 1 km ramp. The varying lift of the wings will be an obstacle, though this might be manageable with flaps. Of course, a 2g takeoff would be a dramatic experience for the passengers.

[acoard]

This principle is already in use in "Ski-jump" aircraft carriers[0] like the British and Chinese use, compared to the catapult operated American carriers. The problem is it isn't remotely high enough. It does have an effect on take off distance, so for that short amount would help for fuel efficiency, but then you still have +30,000ft to climb. 737's often cruise at 30-40k feet, as the air is thinner up there so there's less drag and you have better fuel efficiency. Even if you launched airplanes off the tallest structure ever built (Burj Khalifa, 2,700ft), you'd still have the majority of the climb ahead of you. Planes go high.

My non-credible idea would be to just use an Apple-style magsafe charger on the back of the airplane that disconnects midair at 30,000ft and falls on the helpless people below.

[0] https://en.wikipedia.org/wiki/Ski-jump_(aviation)

[scythe]

Yeah, I didn't check to consider that the specific potential energy (10 km times g = 100 kJ/kg) is actually much larger than the specific kinetic energy (200 m/s squared over two = 20 kJ/kg) so my idea of pre-charging the velocity doesn't pencil out.

I do like the magsafe charger idea. However, I anticipate some regulatory issues.

[Manuel_D]

It's not takeoff that consumes a lot of fuel, it's climbing to cruising altitude. You're not going to get much savings with a launch catapult. A catapult really only helps with shortening the runway distances required to take off (e.g. off an aircraft carrier).

[Sohcahtoa82]

You just need a fast enough catapult mounted on a slope. ;-)

An object dropped at 30,000 feet would be traveling at about 3,000 mph when it impacted the earth, ignoring the atmosphere.

Maybe launch at 4,000 mph to overcome drag to throw something into cruising altitude? We'll just wear some noise canceling headphones to block out the OVERSPEED alarms.

[Arelius]

I mean, isn't ignoring the atmosphere ignoring like 90% of the domain?

[bhandziuk]

Just for perspective this is about mach 5. But I guess there is no speed of sound if you're ignoring the atmosphere :)

[Night_Thastus]

A catapult that launches a commercial aircraft with enough force (over a typical runway length) to get it to cruising altitude with no other power source would also turn all the passengers into raspberry jam.

[Ekaros]

I wonder how much energy would be stored in that catapult and what would happen if something went slightly wrong. Like it got stuck midway... Will we have a plane left? Or how many pieces?

[vidarh]

Brush up on your Jules Verne - clearly the solution is (perhaps not so much) a giant cannon....

[njarboe]

So the ramp needs to be about 35,000 feet high?

[kirrent]

If you're going to try and get an aircraft to cruising altitude without using its own energy, surely the easiest concept is with a tug aircraft towing to altitude. Hell, there's even fairly speculative concepts like Magpie envisaging a series of tows.

[matt_heimer]

So if I understand correctly you'd like to shoot planes into the sky with a giant railgun?

[standardUser]

This is how they launch some jets on aircraft carriers. It sounds ridiculous to apply that to a passenger jet, but not really any more ridiculous than the fact that we routinely fly through the air for thousands of miles in the first place.

[Kye]

I'm no expert, but catapulting a sturdy ~30 ton fighter plane seems like a fundamentally different engineering challenge to catapulting a ~400 ton aluminum can.

[standardUser]

The E-2 Hawkeye is one of the largest plane that regularly uses catapult takeoff and it has a wingspan of 92' and weighs about 43,000 lbs.

A220 and 737 both carry roughly 100-150 passengers and have wingspans of 115-120' and the lightest versions weigh around 130,000 lbs.

Seems doable if the jet and catapult system were specifically designed for this purpose. Maybe less plausible for jumbo jets.

[greedo]

Catapults just shorten the runway needed. The plane still needs a ton of fuel to climb to altitude. Plus, I doubt you'd ever get a lot of civilians to fly off a catapult...

[greedo]

It sounds ridiculous because it is ridiculous.

[baz00]

I think getting the passengers to flap has a similar physics outcome.

[hef19898]

Sometimes passengers clap already, we are one letter away from harvesting that energy!

[ramesh31]

>Until a significant change in battery density, electric planes aren't going to be a thing.

There's a big caveat there though. Current aircraft engines are extremely expensive to operate and maintain, regardless of fuel costs. Even a simple GA piston engine would cost more to operate than a small commercial EV aircraft's motors. Replacing turbines with electric motors will provide cost savings that actually make small commuter flights economical again. Kerosene and jet engines aren't going anywhere for the long haul flights. But the future for electric aviation is in the sub 300 mile regional commuter market, where it's faster than a train and has the simplicity of catching a bus.

See Eviation Alice for an example: https://www.popularmechanics.com/flight/a41453056/eviation-e...

Today's battery tech is just barely good enough at this point to start becoming useful for these kinds of flight profiles.

[bluGill]

Sub 300 miles the train should be faster door to door. Trains a better able to get into the middle of a city - airports both take a lot of space and are noisy so they get pushed to the edge of the city. Trains are also better able to integrate with a public transport system so they are easy to get to. Trains don't have the silly security lines (normally - though planes don't need them either). Trains also don't have large economic benefits from every seat full, so they can better handle someone making a last minute decision to go.

Note that I said should above. The reality is North America has terrible train service, and management (congress!) doesn't care: so airplanes end up better despite all reasons they are worse for short trips.

[majormajor]

It's hard for me to imagine (in the US) the government allowing an explosion in small commercial flights w/o TSA and all that rigamarole. If you get 10x, 100x the volume today, with a less upper-crust passenger base, the perceived security/terrorism risk probably starts getting talked about.

[JakeTheAndroid]

and there is already a massive shortage of ATC employees right now. At minimum this would need to be addressed and more than double the workforce of ATC. That's without accounting for any additional infra that might be needed to support a 10x or 100x in traffic.

[ramesh31]

>That's without accounting for any additional infra that might be needed to support a 10x or 100x in traffic.

The TSA requirement is nil for 10 person flights and these would be VFR only anyways. You would avoid a vast majority of the need for added ATC by operating between uncontrolled fields and relying on enhanced automation. The traditional airport model doesn't really apply when flights can be made so casually. Imagine a world where tiny runways that only service EVs are integrated into the city and you can hop between them as easily as catching a bus. Crosscountry travel would be also be possible via smaller hops, and cost less than a direct long haul jet liner ticket.

All of that is enabled by the orders of magnitude reduction in operating costs. EV Alice is claiming $200/hr to operate an aircraft that has the equivalent performance to a $1k+/hr turbine within the range limitation.

[JakeTheAndroid]

> Imagine a world where tiny runways that only service EVs are integrated into the city and you can hop between them as easily as catching a bus.

I mean, that sounds like a massive shift in infrastructure and city planning. I am not sure how efficient and affordable this would need to be to achieve that level of integration into daily society. Currently nothing, in the US at least, is setup to function this way. Whereas rail and roads are already deployed.

And again, this ignores any of the issues brought on by scale. If this is the way we want people traveling at a 10x or 100x rate, the airspace is going to be busier and likely will need some sort of coordination, whether ATC or some other mechanism.

[ToucanLoucan]

I struggle to conceive of a green future for aviation. I'm not saying we can't have planes, we absolutely should and for many applications they are the only answer: but high speed rail could offer a lot of what airlines currently do at significantly lower cost to both passengers and to the environment, and with less need for such extensive and radical safety features as are required for aircraft.

But just like, reading this comments about everything from batteries to from-ground power sources for ascent to dragging dead batteries after use... like, what if we just flew less? Yes for international travel that needs to happen at speed, a plane is basically the best option. But for... basically everything else, what if we just sacrificed some convenience to not be dumping industrial amounts of waste into the atmosphere?

I'm reminded of how much air quality improved almost worldwide when covid first hit and offices were shut down, offices that, I remind you, continued to function largely just fine after a period of adjustment to remote work. I'm obviously extremely for making all transportation tech more efficient, but an under-discussed element I feel in this is just... doing less shit? Moving fewer people when moving said people isn't really needed? Maybe not growing all the pineapple in one country and shipping it over to a different country to be packaged in plastic and then shipping those all over the world so everyone on the planet has ready access to pineapple, a ton of which is just going to go straight in the garbage because we don't actually need all that damn pineapple?

[hef19898]

Where do you confidently take the idea from, that electro motors for electric aircraft are cheaper to maintain than piston engines?