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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]

#61

Post by icc97 »

Quanttek wrote: post #17

I must say I'm against this development. First of all, even if electric, this is certainly a very inefficient way of transportation that will 'waste' a lot of energy to transport maybe 4 people. The resulting price of this technology will result in the 99% stuck on the ground while the only te 1% can afford the fare. And even if it becomes a regular mode of transportation, do you really want these planes to fly over…

If it reduces the din of the awful noise of living anywhere near to a helipad in the south west of London, just so rich kids can come and go as they please, then it's worth it.

The choppers are already there, so there's already the risk of something falling out of the sky.

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

#63

Post by jasonmaydie »

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…

The two words you need when making a justification is reliable and safe. It won't matter how innovative and energy efficient it is if it doesn't meet the above requirements. If the osprey taught as anything, flying unconventionally is hard.

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

#64

Post by danielvf »

javiramos wrote: post #52

My understanding is that a larger, slower turning propeller is more efficient than a smaller, faster propeller. If so, why do drone companies/small aircraft companies have been pushing the more and smaller propellers model? Better aircraft control? Optimizing for range and battery life doesn’t seem like a bad idea.

So there are two ways to control a rotor craft.

You can adjust the angles of individual blades, changing this angle multiple times each rotor sweep, as helicopters do. This is expensive, complex, things wear out, and a safety risk for the aircraft.

Or you can do what quadcopters do, direct drive the rotor and just adjust the speed of the entire rotor. This gets rid of both the Swashplate system and a transmission. It's lightweight, simple, and cheap. The problem is that it doesn't scale well to bigger rotors. When a rotor gets too big, it has enough inertia that you can't speed it up and slow it down fast enough to control your aircraft. Also, as you get bigger, you want a slower spinning rotor, and current electric motors aren't happy direct driving at that slower speed.

If you want to use the simple system, you have to use small rotors for now.

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

#65

Post by elago »

Jyaif wrote: post #55
JohnJamesRambo wrote: post #42

Earlier quoted context omitted.

Care to share this infinite energy idea?

You know very well which source he's talking about. And he said say near infinite, precisely to defend against obnoxious commenters.

Could you please name the technology? I work with renewable energy and I have no idea.

Are you talking about nuclear?

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

#66

Post by blocked_again »

t3po7re5 wrote: post #50
akerro wrote: post #28

Earlier quoted context omitted.

I'm personally against it because I don't want anything to fall down into my garden or on my head in case of a failure.

Can't you say the same about helicopters and airplanes?

Yup. But probability is close to Zero.

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

#67

Post by mannykannot »

SlowBro wrote: post #58
mannykannot wrote: post #54

Earlier quoted context omitted.

The key figure is the lift to drag ratio - as the lift needed is determined by the weight, then that divided by lift / drag gives you the thrust you need to keep flying. Autorotating small blades are not efficient lift generators, compared to fixed wings, which can have lift / drag ratios over 50 (though not on this machine.) Even partial lift from the rotors would reduce the overall lift / drag ratio. In addition, h…

Would a classic helicopter rotor overhead be a better solution, paired with those classic wide horizontal wings? Lift with the rotor, then thrust with the rear prop, using both wing and auto rotating overhead rotor combined for maximum lift. Requires a tail rotor or similar. Perhaps the rear thrust motor or prop can be rotated sideways for takeoff? Now we’re getting complex, but not extraordinarily so. Ape4 noted wou…

There have been several experimental aircraft like that [1] [2], but they are more like augmented helicopters than fixed-wing aircraft with VTOL. Aerodynamically, the arrangement is a biplane, and biplanes are rather inefficient because interference between the flows over the two wings reduces the overall efficiency.

Note that in the case of the Sikorsky S-72, the intent was to stop the rotor in cruise.

[1] https://en.wikipedia.org/wiki/Eurocopter_X3

[2] http://www.aviastar.org/helicopters_eng/sik_x-wing.php

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

#68

Post by blocked_again »

nl wrote: post #48
akerro wrote: post #28

Earlier quoted context omitted.

I'm personally against it because I don't want anything to fall down into my garden or on my head in case of a failure.

Do planes often fall on your head?

Nope. Given the number of planes in the world the probability of that happening is close to Zero. But a lot of birds has pooped on my head. The more KittyHwaks and other mass used flying cars in the air the more the probability of one falling on your head.

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

#69

Post by danielvf »

jasonmaydie wrote: post #63
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…

The two words you need when making a justification is reliable and safe. It won't matter how innovative and energy efficient it is if it doesn't meet the above requirements. If the osprey taught as anything, flying unconventionally is hard.

I totally agree with you - getting this to beyond current single engine aircraft safety rates is going to be the challenge.

However, they've got a far better starting platform for doing this than anything else I've seen. It's made out of simple pieces with a lot of good options when things go wrong.

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

#70

Post by ransom1538 »

Small planes have had parachutes for quite some time [1] now and have saved many lives. Why on earth would this company put people up into the air unmanned without one? [Personally, if a parachute was onboard I wouldn't mind jumping into one.]

https://www.youtube.com/watch?v=kQyrPVIIQdE

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