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Cora – Kitty Hawk's prototype air taxi [video]

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Re: Cora – Kitty Hawk's prototype air taxi [video]

#121

Post by madamelic »

Kequc wrote: post #107

I don't like that they're touting no emissions. Electricity has to be generated and in the US that's mainly coal. Hybrid vehicles are closer to having it right where running the car charges it and you can get by burning significantly less fuel. Strictly electrical has not been shown to be an energy saver or a flag bearer of emissions reduction. In many cases so far it has been a cause of more pollution than modern en…

You're talking like renewable energy isn't taking over everything.

Let's build everything together because if we assume electric cars will never work because energy sources suck right now, our planet is definitely going to be worse off.

Re: Cora – Kitty Hawk's prototype air taxi [video]

#123

Post by Someone1234 »

assblaster wrote: post #119
syntaxing wrote: post #106

Can anyone chime in how this aircraft is so energy efficient? It seems like the props on the wing will give a ridiculous amount of drag. Also, one of the key requirements for an energy efficient rear prop plane is super laminar air going to through the rear prop for efficient thrust. The wing design seems to remove this advantage. Edit: Also, I thought smaller props for vertical flight is significantly less efficient…

I don't know for sure, but I think that autorotation of the multiple vertical rotors provide substantial lift even if they're not being actively driven, similar to the tree seeds that autorotate as they fall.

Auto rotation converts air speed (i.e. drag) into lift. That may slightly reduce the relative costs of drag (by providing benefit) but it still has to be overcome by forward momentum.

Re: Cora – Kitty Hawk's prototype air taxi [video]

#124

Post by danielvf »

cowsandmilk wrote: post #85
danielvf wrote: post #47

Contrary to almost every comment here so far, this is both innovative and energy efficient. Let's talk energy efficiency first. Once it's up in the air, it's has a similar profile to a normal single engine airplane. A Cirrus SR22 can go 1,200 miles on 80 gallons of gas. That's roughly speaking 15 miles per gallon - better than many pickup trucks or large SUVs. And that's while going 180 mph. Slower is more fuel effic…

> A Cirrus SR22 can go 1,200 miles on 80 gallons of gas. That's roughly speaking 15 miles per gallon - better than many pickup trucks or large SUVs. Sure, let's take the most energy efficient aircraft and compare it to the least energy efficient passenger vehicles??? I mean, how can one even pretend that is a fair comparison. More generally for energy efficiency, it is well known that the most efficient trip is a sho…

We do seem to have different value systems. I believe applying energy to make human lives better is a great thing! Electricity usage in the western world is getting greener fast. Total usage is going down, not up. This isn't going to reverse either of those trends.

There's a popular perception that all aircraft burn energy like an oil refinery on fire. The reality is that small piston aircraft are approximately as fuel efficient as the vehicles around you on the highway (at least where I live) while getting you there a whole lot faster.

A Cirrus is a good comparison stand in for the KittyHawk aircraft because it has a similar design and construction style (ignoring the dodeca-props), four seats, and is the most common general aviation aircraft not designed in the 1950's. A Cirrus isn't even close to the most energy efficient aircraft - that would be more like 60 mpg, nor is it the most efficient in its class.

Re: Cora – Kitty Hawk's prototype air taxi [video]

#125

Post by FidelCashflow »

Am I the only one who finds it endlessly annoying to refer to anything that's primarily (or exclusively) powered by a battery as "green" or "emissions free" or "pollution free" or anything else?

What about the energy to manufacture, ship, assemble, design, test (or clean up when it fails), etc. That all takes energy and most of that energy probably comes from coal or some other environmental nightmare resource.

Re: Cora – Kitty Hawk's prototype air taxi [video]

#126

Post by Kequc »

seanmcdirmid wrote: post #114
Kequc wrote: post #107

I don't like that they're touting no emissions. Electricity has to be generated and in the US that's mainly coal. Hybrid vehicles are closer to having it right where running the car charges it and you can get by burning significantly less fuel. Strictly electrical has not been shown to be an energy saver or a flag bearer of emissions reduction. In many cases so far it has been a cause of more pollution than modern en…

> Electricity has to be generated and in the US that's mainly coal. Huh? Coal is only 30% of the USA’s energy production, natural gas is higher at 34%. https://www.eia.gov/energyexplained/index.cfm?page=electrici... The other points in your post are equally dubious, do you have sources?

Wikipedia lists energy consumption being 70% coal, I'm not sure why the large discrepancy there. I got my information about electrical engines from a website trying to talk up how great it was that we were moving away from oil based engines, but even there they admitted that until more power generation is switched over to renewable that emissions are higher with electric cars. Which makes perfect sense and is not dubious, the fewer times you need to convert energy the less energy wasted. Electricity does not store well, additionally.

Re: Cora – Kitty Hawk's prototype air taxi [video]

#127

Post by davidedicillo »

Kequc wrote: post #107

I don't like that they're touting no emissions. Electricity has to be generated and in the US that's mainly coal. Hybrid vehicles are closer to having it right where running the car charges it and you can get by burning significantly less fuel. Strictly electrical has not been shown to be an energy saver or a flag bearer of emissions reduction. In many cases so far it has been a cause of more pollution than modern en…

Fortunately, the US isn't the only country on the planet. We could, for instance, get inspiration from those countries that heavily invest in renewable energy.

Re: Cora – Kitty Hawk's prototype air taxi [video]

#128

Post by Beltiras »

ethagknight wrote: post #71
danielvf wrote: post #47

Contrary to almost every comment here so far, this is both innovative and energy efficient. Let's talk energy efficiency first. Once it's up in the air, it's has a similar profile to a normal single engine airplane. A Cirrus SR22 can go 1,200 miles on 80 gallons of gas. That's roughly speaking 15 miles per gallon - better than many pickup trucks or large SUVs. And that's while going 180 mph. Slower is more fuel effic…

Agree with most of what you say, but two open questions- debt alone on $500k amounts to $180/day (10yr am, 6%). Then there’s cost of energy, dead time during recharge, dead leg trips to the next customer, dead let to charge port, maintenance will be rigorous even if the plane doesn’t need it because FAA. Landing fees while be high for urban landing points, plus ground crew at some locations. “Max $100/hr” is way low,…

You can use battery swapouts instead of grounding the vehicle.

Re: Cora – Kitty Hawk's prototype air taxi [video]

#129

Post by Anderkent »

FidelCashflow wrote: post #125

Am I the only one who finds it endlessly annoying to refer to anything that's primarily (or exclusively) powered by a battery as "green" or "emissions free" or "pollution free" or anything else? What about the energy to manufacture, ship, assemble, design, test (or clean up when it fails), etc. That all takes energy and most of that energy probably comes from coal or some other environmental nightmare resource.

>That all takes energy and most of that energy probably comes from coal or some other environmental nightmare resource.

Maybe, but it's easier to replace centralised pollution from something like a coal electricity plant, than decentralised pollution of every appliance generating it's own power.

A battery appliance doesn't care if the electricity that coms to it is from a hydroplant, a nuclear facility, or coal. It's decoupled from the source, and so allows you to improve things iteratively.

Re: Cora – Kitty Hawk's prototype air taxi [video]

#130

Post by seanmcdirmid »

kazinator wrote: post #105
melling wrote: post #76

Earlier quoted context omitted.

Yeah, now imagine tens of thousands people an hour being able to do that. I hear they have trains that can do this in far away lands. Trains that go 180 mph. Not in my backyard.

Trains that go 180 mph have a way of draining your pocketbook. If you don't work near a station, or live near one (or, worse, both) you face commuting hassles. You may have to take a train that averages 30 mph as it makes all stops to get to the 180 mph express one.

It actually works well enough in japan: 15-20 minutes on a local to get to the Shinkansen station, then an hour on that, then another 15-20 minutes to get where you are going. Not really in daily commute range, but definitely viable weekly.
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