Kitty Hawk is accepting waiting-list signups for its electric personal aircraft
nytimes.com
nytimes.com
Is battery energy more efficient with air speed lift from a wing, like traditional aircraft, or from air suspension, like a helicopter? Does the mass/energy of a gasoline power train (including fuel & motor) exceed an electric power train?
I guess I'm wondering about the viability of electric power for flight at all. Drones are useful for some applications with light payloads and conducive environments, but when you need to lift a substantial payload, like me, isn't battery just too little power density?
Finding an engine / generator / capacitor combo which is light enough and powerful enough to work well with a multirotor is expensive.
Not to mention that such machines would be looked down on because of their use of fossil fuels.
Micro/Nano Gas Turbine Engines easily surpass batteries over 1h, but are not cheap or easy to use. And, if you only need 10 minutes at a time for testing then batteries are significantly lower weight.
EX: Wren's MW44i 46 oz (1320g) and produces almost 7 hp or ~5kw.
Above a certain size, it's simply more realistic to use variable pitch rotors that don't rely on speed changes to maintain stability, at which point the traditional helicopter design becomes more efficient.
Increasing the weight increases the engine & prop size, which increases your energy needs.
EDIT: From the few multirotors with a gas engine that I've seen, the right combination of weight - maneuverability sweet spot appears to be around the 750mm size - around 2 feet in diameter. They also tend to have good flight times, but still in the sub-one hour range. Again due to weight.
Helicopters are aerodynes just like fixed-wing aircraft, deriving lift from aerofoil speed. They are just less efficient because in traditional single-rotor designs only part of the rotor disk is generating lift at any one time ( and part is stalled ) and of that part needs to be directed as propulsive thrust.
Some helicopters have employed short wings to offload the rotor.
A wingless VTOL aircraft such as the Flying Bedstead, or the Lunar Lander testbeds, is a non-aerodyne and is even less efficient because it relies on a small volume of highly-accelerated air for lift versus displacement of a large quantity of slow ( roughly speaking ).
Still wondering if electric powered flight is commercially viable for general purpose human transport.
Since the airplane wings affect a larger air volume than the helicopter blades, the airplane accelerates a larger air mass, but to a lower speed. The helicopter: smaller air mass, higher speed.
Since energy required is proportional to the second power of speed, the helicopter requires more power for the same lift.
You could create a helicopter that was quite efficient in hover, with really big blades. It would then have some other problems, like limited speed.
Could be a reference to ground effect, and a mistaken belief that helicopter lift is driven by ground effect (ground effect does play into helicopter low-altitude behavior, but as you mention they are aerodynes.)
Check out this section on Electric/Eco friendly Planes from the famous "Sustainable Energy Without the Hot Air": http://withouthotair.com/cC/page_278.shtml
If you like mathematics you'll also enjoy the chapter on Planes: http://withouthotair.com/c5/page_35.shtml
* fixed wing flight is faster, has a longer range, and is "more efficient" than rotorcraft
* gasoline, for now, has roundabout 50x as much energy per mass ("specific energy") as batteries.
* however, electric engines are 4 to 10 times more efficient.
* so basically, with electric power for now you can only fly about 10% to 20% as long/far as with avgas - ok for a few specific applications, but not yet good enough
* on the other hand, electric engines are much simpler, lighter, and more reliable than piston engines (turbine engines are also very reliable, though)
(* note that one needs sufficient specific energy to fly long/far enough, and sufficient specific power e.g. for takeoff)
* lastly, batteries appear to improve at around 4% to 8% per year (some incremental improvements, but mostly switching to new "chemicals", eg lead to NiMH to Li-...), so electric flight could become really interesting in the next two, three decades.
Probably should be called flying motorcycle but on a marketing level doesn't have the same impact.
(At least this is what I understand the range to be.)
Why have your engine pull the extra weight of your propellers...and why have your propellers lift a drivetrain?
I get your point that "flying car" may be a tad misleading, but my guess is that they made this first iteration a "water vehicle" to get around the majority of regulations while still getting a product into the field to test and (perhaps) make some money while they're at it.
You may be right technically, but there are practical reasons why flying cars may not travel over land for a very long time. I suspect noise is one of those reasons, it's why planes are limited to certain speeds despite being able to travel faster at higher efficiencies. It would be a great disturbance to the residents living below.
Hard problem.
>personal aircraft
Much harder problem, if by that they mean "flyable without a pilot's license". You need to tackle reliability, then AI on the order of self-driving cars, then regulators, then infrastructure. Even Tesla is having a hard time making a slightly different kind of car.
Why tackle all the hard problems at once? Why not make a self-landing helicopter, or a "normal" electric aircraft (like Tesla but for planes), or a reliable and cheap (!) experimental VTOL craft? I can't help but think that the only reason to do it this way is because you're selling sizzle, not steak.
Also, at this point of time, maybe we can engineer good specs and good price into the product, but we cannot overcome human factors.
- Riding in strong winds. - Loss of control over populous areas. - Higher risk of crime in a vehicle that has no boundaries like roads and dividers.
The most likely solution is to make a cloud connected one which refuses to fly in or into bad weather, automatically lands during emergencies etc. But then that will necessitate some sort of remote control over the vehicle, leading to a host of other issues related to lack of privacy.
http://www.volocopter.com/index.php/en/
(Disclaimer: I have crowd-funded invested a modicum in it)
That appears to be underway in Germany (though bureaucracy moves slowly...). USA/FAA, of course, remains to be seen, though the general move to performance-based certification makes me a bit more optimistic.
At any rate, the two major roadblocks are regulation and battery, as ever.
Also, not looking forward to the headlines about disputes[0] about airspace over people's property.
Edit: clarification
[0] Dude with a shotgun vs dude on a flying "car".
What does the Kitty Hawk compete with?
- small helicopters cost $XX.XXX and have been available for many years. Proven technology, though unsafe. E.g. https://en.wikipedia.org/wiki/Mosquito_Aviation_XE
- small airplanes for the crazy? https://www.youtube.com/watch?v=KLgR3Ipo-Ng
- flying cars that can actually drive on the road? https://www.aeromobil.com/flying-car/
It looks like a toy in comparison, to be operated by quadcopter enthusiasts for 5 minutes ... Perhaps they should call it "flying golf cart"?
I speculate the kitty hawk vehicle will have 10-15 minutes airtime and will cost around $100k
Fixed wing is the only way to go for efficiency and I can't imagine anything other that a hybrid having more than 45minutes flight time @ <40knots.
It's deffo possible to make a high lift, low speed fixed wing that has a short takeoff/landing requirement. There are elec ultralights that do this today.
This whole obsession with elec/'coter design baffles me - even with the most optimistic math assumptions it is a terrible product.
In short, if the video had shown ascent to an altitude of, say, 100 feet, I would be much more impressed.
ps: lakehawk
I wonder why Google is doing all this pre-launch marketing hype. Usually this is the playbook that startups use to hype up VCs for funding rounds. Maybe just for PR and branding?
Reminds me of UBeam's "we plan on launching publicly this year!" (said in 2015, 2016, and now 2017)
I expect it will barely be a product when it launches, certainly not one with wide appeal.
I speculate the kitty hawk vehicle will have 10-15 minutes airtime and will cost around $100k.
It will appeal to a very niche market of deep pocket hobbyists.
There goes my dream of commuting to work like a boss in half the time.
You can try your luck and fly around with this thing as you would with any other ultralight.
a good post on the subject http://eaaforums.org/showthread.php?5261-Part-103-quot-conge...
It can be adapted with floats if you wish.
"The focus on over-water flights is intentional -- it's meant to reassure Federal Aviation Administration officials worried that unlicensed pilots will be flying over populated areas. The company wants to work with the FAA to enable more ambitious vehicles, but it would rather play it safe in the early stages."