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[-] Knock_Knock_Lemmy_In@lemmy.world 4 points 13 hours ago
[-] captain_aggravated@sh.itjust.works 3 points 11 hours ago

No, what I'm talking about isn't steaming bullshit fresh from the bovine's ass.

What is the major complaint people have about electric cars? Range, right? Because lithium ion or lithium polymer batteries do not have the energy density per unit volume or unit weight of gasoline. Electric cars are often heavier than their ICE counterparts because they're crammed with so many batteries to make up for the relative lack of energy density, and they benefit from things like regenerative braking. Electric motorcycles often don't have regenerative braking, which is why Kawasaki is right now advertising a $7000 sport bike with a 55mph top speed (65 if you push the boost button) and a range of 41 miles (if you don't push the boost button). The Ninja 250 I bought in 2007 could do 120mph and I routinely went 300 miles between fill-ups with it's ~5 gallon tank.

Meanwhile these folks have a hexacopter that will out-carry and out-run a Robinson R-44 piston-powered helicopter, on Lithium batteries.

Actually just right there, they say a 200 mph cruise speed and a 100 mile range. So that's a 30 minute endurance. To legally fly cross country in the United States, you need to have enough endurance to make it to your first intended point of landing PLUS 30 minutes, and that's day VFR minimum fuel when operating under Part 91. Are you telling me it has an hour of battery life but half of that will be in reserve? In something like a Cessna Skyhawk a half hour of fuel is something like 4 gallons of gasoline, or about 24 pounds. How much lithium battery do you need to make ~100 horsepower for half an hour? And mind you, that's cruise power, NOT takeoff power. Which will be a LOT greater than cruise power especially in a VTOL aircraft. I get that it's a tiltrotor and would have airplane-like performance in cruise, but it'll still be more of a bitch to get airborne than a conventional plane.

Anybody want to see me plan a 100 mile flight in a Cessna Skyhawk, figure up how much gas the trip would take, convert that amount of gas to kilowatt-hours and then look up the weight of a Li-Ion battery with that capacity?

I'd also be real interested to know what the secret sauce is to make those propellers that quiet. Yes, electric motors are quieter than gas engines, but the noise from something like an airplane or helicopter is mostly made by the propeller/rotor blades, especially at the tips. By what physics are you going to make something with 6 propellers quieter than something that has one? I bet that thing is going to be louder - and shriller - than an equivalent helicopter. Stand next to a toy drone in flight and explain to me by what magic they're going to make one that seats four make "a barely perceptible sound."

If you're going to tell obvious lies, just say I'm pretty.

[-] Knock_Knock_Lemmy_In@lemmy.world 1 points 8 hours ago

I'm suggesting these flying transport firms may be lobbying for change, not that they have a viable business/technology.

[-] oyo@lemm.ee 2 points 9 hours ago

The lack of imagination in this post is astounding. In this wall of gibberish you only really made three points: range, excess range, and noise.

Range: evtols are not trying to replace GA aircraft, at least initially. They will start out as air taxis and toys for the ultra rich, but most people dramatically underestimate the rate at which battery technology is improving. Being able to travel 100 miles in 30 minutes without spending an hour on each end dealing with the airport is something unavailable today.

Minimum fuel requirements: rules are meant to serve us, not be handed down from on high. If this does apply to evtols it will be changed. It's a completely different use case. For example the emergency landing options for an evtol are vastly more available than for a Cessna.

Noise: I mean, agreed overall if not in detail. Realistically these things are going to be quieter than a traditional helicopter for sure, but will be higher pitch and swarming around in greater numbers. Annoying AF.

this post was submitted on 11 Oct 2024
129 points (98.5% liked)

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