Discussion in 'Hangar Flying' started by Aerowerx, Jan 24, 2019.
Boeing has allegedly successfully tested a flying car.
Here's a link to a Reuter's story on it. Talks about the goal being an autonomous vehicle. 1 photo.
Here's a PC magazine story, with a 19 second video. (complete with "dynamic music!") The car/pusher airplane (?with some type of detachable drive-on VTO framework with electric vertical lift motors?) is shown hovering. I'll wait to start clearing out a space in the garage.
This is the kind of story best covered by the "technical press" (Aviation Week, etc). I'll look forward to reading something a bit more meaty.
Mmm, whirling blades at knee height. I bet you could mow grass with a bit of practice.
I wonder the price?
I'm afraid I've gotten to be very cynical about these sorts of announcements. Usually they're just company PR campaigns, to keep the company's name in the news and to show that they're "leading edge innovators." IMHO, this program is more about supporting their stock prices than developing a new product for sale.
Wake me when I can buy one for my own garage.
Can some of you smarter and more educated folks here explain to dim-wit old me why a small coaxial helicopter with 16 foot rotors, fitted with the same amount of computerized autonomous stability/flight controls, would not be able to meet this VTOL commuter mission using existing technology, with a far greater level of efficieency?
My limited understanding of VTOL is that blade aspect ratio (rotor diameter) is every bit as important for efficiency and lifting ability in rotary wings as it is in fixed wings, which is every bit as important as it is for thrust and efficiency in aircraft propellers.
The leading mass-production personal VTOL aircraft currently available appears to be the Robinson R22 helicopter, which can safely and reliably fly two people 240 miles on 150HP, using 1970's technology in the airframe and 1940's technology in the powerplant. No computerized controls, no high tech materials, no Unobtanium Magnet electric outrunners, no Dilithium Crystal battery.
Pardon me if I have misunderstood some of the Laws of Nature, but for every electric motor, every set of rotor blades, every wiring loom, and every speed controller... there is some amount of loss or entropy. So for a given output or performance you need to achieve, the more devices, components, and systems you use to achieve it the less energy efficient it is going to be. As we have discussed here on HBA, a hundred tiny electric motors and propellers HAS to be less efficient than one or two larger motors and rotors.
Other than the public's current fascination with multi-rotor toy drones, why isn't a modern technology coaxial helicopter configuration being chosen for the VTOL "flying car" ?
Two reasons, in my opinion:
1) The "perceived danger" of helicopters. Our aviation culture has spent decades teaching that "Rotors are dangerous!! Keep your head down!!!", successfully. Multi-copter "little" rotors are perceived as being less dangerous, because the little R/C ones can only cut your hand. It's not rational, but there it is.
2) You're still thinking this is a project that's intended to develop an actual product that will be for sale. Helicopters are soooooo last century. Multicopters are TODAY, man! (Ahem.) This project is a couple million dollars spent pumping up Boeing's perceived "cutting edge technology" image, which can result in hundreds of millions of dollars (if not a few billion) in stock revenue. You don't think it's a coincidence that this press release came out on the perceived "recovery" side of the recent market downturn, do you? Everyone who panicked and pulled their money out of the market at the end of last year is going to be looking to buy back in. "Why not buy Boeing?" is what this flying-car press release is all about.
Maximizing disk area (not maximizing prop/rotor diameter per se) is the way to get the most thrust per HP. With electric motors, it is practical to have a lot of small ones to get a lot of rotor area. This is far less practical with IC engines, because they don't scale down well (their mass per HP increases as they get smaller, and they also burn more fuel per HP).
I think the main thing Boeing is working on is autonomy and integration into an airspace control system that doesn't yet exist. The flying part is easy, it is doing it without a pilot and in a high-traffic density environment that is the biggest challenge, and potentially a huge game-changer.
Maybe they'll hire Moeller next.
Which, as I stated in the previous thread, is why "bottom of the hour" reports (particularly on technical matters) is not too far above used toilet paper, IMHO.
I'm waiting for one that fits in the same footprint as a standard size early 21st century SUV. Oh yes, with no external moving parts.
Can you say "anti-gravity propulsion"? I actually invented it once, but when I woke up I couldn't remember the secret.
I can't be the only one that remembers how it is done can I? Once you get into the "Zen State" you can float as long as you can hold your breath.
Oh, I just realized that was the same time I was learning how to swim. I could jump up on the diving board and float in the air until about to take a breath. Then I would fall into the water and come up for a breath of air.
Ok, it works much better when you are dreaming but it still works somewhat in reality.
As I understand it, it's all about achieving a functional compromise in the 3D space of complexity, efficiency, and modularity.
Yes, a single large rotor is probably the most efficient way to turn power into vertical thrust. Or any kind of thrust, really. And when your source of power is heavy, inefficient, and rife with vibration modes on and around every axis, a single large rotor plus maybe one auxiliary rotor is probably the way to go. But the reality of such machines is that delivering such ungainly power into the rotor, and then delivering the rotor's power into the air in a stable and controllable fashion, requires very complex transmissions and even more complex control articulations. The inevitable result is a very high parts count, a large number of critical assemblies, and many opportunities for defects of concept, design, engineering, manufacturing, or maintenance to result in plummeting flight modes. And plummeting is bad, very bad. So such machines are very expensive to make, and they must be tested, inspected, and, maintained very carefully in order to operate with any reasonable degree of safety.
The alternative approach being explored and demonstrated by the current crop of jumpers (a jumper crop, get it?) uses the combined advantages of high energy density lithium chemistry batteries and high power density brushless DC motors to vastly simplify the delivery of power into the air, and to an even greater degree simplify control over the power delivery. Using a lot of distributed motors and rotors instead of one big rotor means that no single motor is critical, at least not once you're up over about five motors. If one craps out, you simply modulate the power delivered by the remaining ones as appropriate to maintain controlled flight. If you need to turn or accelerate laterally, you just modulate differential thrust to achieve the necessary acceleration. None of this jittery flappy pitchy collective stuff, just power to direct drive motors, each with a fixed pitch rotor. Furthermore, the impression I get is that a field of small rotors clustered together can approach the efficiency of a single large rotor.
Of course, the argument might made that the multiple motors and rotors and their support infrastructure might actually represent a higher parts count than a single rotor and its collective monkey motion. The obvious counterargument is that there might be more parts, but many of them are identical duplicates of each other that leverage economies of scale in development and manufacturing. And many of them are functionally redundant, such that their failure would not be a critical event.
Interesting. There is no need for a flying car to be street legal or even within the "Oversize Load" limitations. Doesn't that make it just another aircraft, UAV.
Also of note the "flying Car" does not meet the minimum specifications of the Boeing GoFly Prize competition.
"I think" the GoFly is a one person vehicle? Whereas the Flying Car is multiperson?
Actually, I have had several dreams on the same topic. Started out experimenting with levitating a non magnetic object (bowling ball to be specific). For the first vehicle I built it into the old full size dodge van my brother used to have---the only thing big enough to hold all the batteries. Then as the technology improved it got smaller until it would fit in a standard size car. What would be the parking brake between the seats became the "lift" control and the steering wheel did the, well, steering. For some reason it always worked better when going over the crest of a hill. Start lifting the lever as you reached the peek.
Looks like a 30 foot span "convertiplane". Boeing is a major helicopter manufacturer, they know what a convertiplane is.
It is not a "Flying car." (that drives on roads and flies sometimes)
Mine is a personal bullet proof express vehicle, which wanders the globe with impunity to authority.
Parts count. And parts count's effect on reliability and cost.
A helicopter rotor and its associated control system (swash plate, linkages, etc., etc.) has hundreds of precision moving parts which all must keep moving. A multicopter, OTOH, has a fixed pitch fan bolted directly the shaft of a brushless motor: two moving parts, times whatever number of fans you have.
The Boeing design, which is certainly not a "flying car" (though it might be an "airborne taxi"), also has a pusher propeller and fixed wings, implying that the lift fans will be lightly loaded or completely off during cruise flight. Managing small fans during the transition has got to be a lot easier than a 30' rotor.
But I picture mine as being a primitive sub-light warp drive. Can't get enough energy out of old car batteries to go much faster than 0.0001 warp.
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