That video is so cringy.
It is like those kickstarter videos, except they have something other than fluff to show.
Cora – Kitty Hawk's prototype air taxi [video]
51–60 of 286 posts
Re: Cora – Kitty Hawk's prototype air taxi [video]
#52My 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.
Re: Cora – Kitty Hawk's prototype air taxi [video]
#53Re: Cora – Kitty Hawk's prototype air taxi [video]
#54It seems the vertical take off blades become dead weight and air resistance in horizontal flight. Could they auto-rotate instead, aiding lift? Similar to how an auto gyro works. The wings would be the primary lift providers but why not take advantage of the vertical blades as well?
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, having the rotors generate lift would have an effect on the airflow over the wing, and probably be detrimental to its efficiency - it is bad enough that they are there at all, especially those in front of the wing.
Re: Cora – Kitty Hawk's prototype air taxi [video]
#55I love it. Can’t wait to see the first batch of production reviews from customers. Also on energy usage: Why does it matter how much electrical energy it uses? We know how to harness a near infinite amount.
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.
Re: Cora – Kitty Hawk's prototype air taxi [video]
#56My 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.
Most likely because of better control for drones. For this air taxi it may have more to do with noise.
Re: Cora – Kitty Hawk's prototype air taxi [video]
#57They claim that it is quiet, but there is no audio to give any sense of that. I would want to hear two people having a conversation while it takes off nearby.
Even from the video, it doesn't sound too quiet to me, and I'm sure they tried to minimize how it sounds in the recording, or at least they seem to be cutting off the video quickly when there's some noise in the video.
It may be 2-3x quieter than a helicopter, which I'm sure the engineers from the project would consider it a big innovation on its own, but that's not exactly what I would consider "quiet".
But as I said in the other thread, I think this is a fine technology to have in the future, and I'm not too critical of it, like I would be if this was a hydrogen-powered air taxi for instance.
It's battery powered, it's "self-flying", and the noise should improve in the long term, even though it will never be "quiet". I think there's little not too like about it. Range is not amazing, but for a first-gen fully battery-powered air taxi, it's not bad at all. They'll probably reach 5x as much by 2030.
Re: Cora – Kitty Hawk's prototype air taxi [video]
#58It seems the vertical take off blades become dead weight and air resistance in horizontal flight. Could they auto-rotate instead, aiding lift? Similar to how an auto gyro works. The wings would be the primary lift providers but why not take advantage of the vertical blades as well?
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 would add weight and complexity. Any more than eight small electric motors and props do now?
Re: Cora – Kitty Hawk's prototype air taxi [video]
#59It seems the vertical take off blades become dead weight and air resistance in horizontal flight. Could they auto-rotate instead, aiding lift? Similar to how an auto gyro works. The wings would be the primary lift providers but why not take advantage of the vertical blades as well?
The rotate mechanism would add weight and complexity.
Disengaging the motors adds weight and complexity? Or would the props need to also be modified?
Re: Cora – Kitty Hawk's prototype air taxi [video]
#60Contrary 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…
Imagine being able to live 90 miles from a town and commuting in 30 minutes regadless of peak hours.
As for the noise, if it can land vertically, I can immagine it making a steep descent on top of a tall building, unloading passengers and then autonomously taking off to pick somone else some other place.