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All-Electric 'Flying Car' Takes Its First Test Flight In Germany (theverge.com)
Today, Munich-based Lilium Aviation conducted the first test flight of its all-electric, two-seater, vertical take-off and landing (VTOL) prototype. "In a video provided by the Munich-based startup, the aircraft can be seen taking off vertically like a helicopter, and then accelerating into forward flight using wing-borne lift," reports The Verge. From the report: The craft is powered by 36 separate jet engines mounted on its 10-meter long wings via 12 movable flaps. At take-off, the flaps are pointed downwards to provide vertical lift. And once airborne, the flaps gradually tilt into a horizontal position, providing forward thrust. During the tests, the jet was piloted remotely, but its operators say their first manned flight is close-at-hand. And Lilium claims that its electric battery "consumes around 90 percent less energy than drone-style aircraft," enabling the aircraft to achieve a range of 300 kilometers (183 miles) with a maximum cruising speed of 300 kph (183 mph). "It's the same battery that you can find in any Tesla," Nathen told The Verge. "The concept is that we are lifting with our wings as soon as we progress into the air with velocity, which makes our airplane very efficient. Compared to other flights, we have extremely low power consumption." The plan is to eventually build a 5-passenger version of the jet.
This demo is just a hover demo, the wings are actually just pure decoration for promo purposes. Not to say that a hover demo is an easy feat, but the cool looking slippery fuselage is not doing anything useful in an aerodynamic sense, rather it is purely for social engineering at this point. Doubt me? Look at the canard, it is not even an airfoil by any stretch of the imagination. This aircraft is absolutely incapable of gliding, it would immediately dive straight down if you tried to do so, with spectacular results.
Given that this is just a hover egg, maybe optimize it for that? The concept render actually shows an airframe that could be capable of some kind of glide ratio, but from the look of it, only at really high speed. Trying to flare out for a standard runway landing would most likely be a life threatening experience. With all those ducted fans, the profile drag will be through the roof. Glide ratio, maybe 5 to 1, optimistically, unless the profile drag can be reduced by some as-yet uninvented magic. By comparison, a garden variety Cessna gets 9:1, which means that landing without power already requires some skill. With 5 to 1, you basically need to be a Chuck Yeager to walk away from it.
Might as well just be honest about it and lose the wings entirely. Simple sticks will do, like the canard, and save some weight. Then what is the remaining reason for having such small fans? Small fans are less efficient than larger ones, meaning the batteries will run out considerably faster than some more practical design.
When all you have is a hammer, every problem starts to look like a thumb.
This flying car won't fit in my garage, won't travel down the highway (or any road for that matter), won't land at the grocery store and pick up milk.
It only works if you live at an airport and your house backs up to the runway.
aren't you comparing this vehicle to a plane when perhaps it should be compared to a helicopter?
It a fuselage optimized for forward flight and it has wings. Therefore it is trying to appear to the view as a plane. It is really a helicopter, as you say, and as I implied by calling the show a "hover demo".
In that case, would the lift from the airframe moving forward would be much more than an equivalent helicopter and thus the range would be much better?
No, for several reasons. The lift from the the slippery egg shape will be roughly zero except at stupidly high angles of attack and stupidly high speeds, so forget that. The lift from the main, rear wing will be pathetic because of the massive disruption of flow causes by the ducted fan housings. And the wing loading is way too high anyway. The video optimistically implies some kind of laminar flow over the wing and through the fans, but the there is so much structural junk in that way that I will have to call that pure fantasy. That rear wing assembly has airfoil efficiency roughly equivelent to a backyard barbeque.
And that is not the worst problem. Aerodynamically, the worst (of many) problems with this concept design is, the forward canard will generate exactly zero lift. All the lift at the front comes from the vertical thrusters, which will need to stay running (at high speed and power consumption no doubt) the entire time that the plane attempts to maintain efficient horizontal flight. This issue could be somewhat fixed by changing the forward ducted fan assembly into a real canard as in the concept animation, but with all the junk attached it would be a contender for world's least efficient canard wing, and fragile to boot.
Obviously, unpowered gliding is a complete non-starter with this configuration. At best, some inefficient form of foil-assisted forward flight will be possible, most likely not efficient enough to justify the additional weight and wetted surface of the real airfoil.
if the engines die you can't "glide" it back to a landing. However the massive redundancy (36 fans) would prevent that from being the point of failure (but the battery, power electronics might be)
You might want to upgrade that "might" to a "will". Consider the case of flying over water with unexpected headwind that lengthens the trip past the battery endurance, or countless other scenarios that come up regularly in real life.
That's where the parachutes come in I guess.
I suggest, some healthy skepticism will come in even more handy in terms of minimizing loss of life.
Since I'd rather have a (safe, easy to fly) helicopter than a plane, I think I'd buy this to go (short) island hopping in the South Pacific. :)
You're a great straight man, you know that? Exactly the scenario I mentioned above...
If you plastered it with solar cells, how long would do you think it take to charge?
How much time have you got?
When all you have is a hammer, every problem starts to look like a thumb.
Yes, but a jet boat is not powered by a jet engine, that is the difference. A jet boat has a gas engine that powers the water jet.
This doofus specifically said the "car" had many jet engines. It actually has many electrically powered ducted fans. Which are not jets except in the most pedantic sense, and even then, they are not powered by engines, but by motors.
"The only good windmill is a tilted windmill."
aren't you supposed to spout this kind of: "Man will never fly!" garbage _before_ it's been clearly demonstrated. The video shows it taking off and in forward flight
To call that demonstration "forward flight" you need to be charitable or gullible. Look again. The front motors are pointed straight down. That does not qualify this thing as an airplane at all, it qualifies it as some kind of helicopter. Helicopters also can fly forward, but they are not airplanes, and they suck for fuel efficiency. Like this thing, which claims to be fuel efficient because of its wings, but don't be stupid. Look at it, it doesn't even have wings on the front and the back wing is little more than a spoiler.
You can see what is going on more clearly in this video of their 1/5th scale model (i.e., 1/125 weight) where the motors are always angled down at least 40 degrees, otherwise it will fall out of the sky. If it had proper wings the motors would point straight back. All that downward vectoring comes straight out of the battery life, which is the main selling point of this concept. Well, if you are a snake oil collector then feel free to buy this concept.
Some wise person said "an open mind is a fine thing, but let it not be gaping".
When all you have is a hammer, every problem starts to look like a thumb.
IAAEngineer. On the Lilium website, the images show the "flight mode" having all of the impellers on the top of the wings, instead of the bottom. They are all sitting on the portion of the wing where aerodynamic lift is generated. There's a wing-surface on top of the nacelles, but the design still looks like it would have negative lift. Anyone who knows how a wing generates lift will understand.
The impellers, necessarily pushing air through faster than the vehicle is traveling, would create a low-pressure zone right in front of them, where flowing air is supposed to be compressed. It's the lower air-pressure over the back of a wing that generates lift. The nacelles are sitting right in the way.
Or does their design position the front-face of the impellers right in that spot. They would have a lower relative air pressure just in front of them, of course. It's hard to tell from the few images the exact positioning, but can an Aeronautical Engineer chime in?