Thinking out of the box: The case for flying car

I have been thinking what would make “flying cars” feasible. I think the answer is pretty much that it needs to be VTOL. Anything that lands on runway will become very complex design mechanically. A real solution would be to land on the car anywhere, e.g. shop parking lot.

So what are the breakthroughs needed for this? I doubt that the internal combustion engines can do this ever very well and turbines are out of question as well because nobody can afford flying to shop with turbine power. So I think this will require electric motors and advanced battery technology. Hybrid design could possibly work too.

Large helicopter propeller blades will become a problem when landing on congested place and it would cause also safety issues. You could hit something with the rotating prop and newspapers would be full of horrific accidents very soon. Someone sliced somebody or sliced somebody’s house or whatever. The props should be shrouded for safety of general public. Then how many props? One prop and it will require tail and tail rotor. Not so nice. Coaxial rotors, that would be better but still will require one to be helicopter pilot. I think the case of how it would work is very simple, and the case example already exists in small scale as sort of “RC copter”:
http://ardrone.parrot.com/parrot-ar-drone/usa/

So computer controlled fly by wire and the user would be just selecting to go forward or backward or up or down or to rotate. Computer handles the rest. Each prop would have electric motors, big ones instead of the small ones found from the little thing. This plane could even have small wings, which could be optimized for cruise only (and not for landing at all) and could be possibly pivoting – when airspeed increases less vertical thrust would be needed. This could be “the flying car” that everybody can control. Not everybody can become a helicopter pilot or even airplane pilot – requirements are all the time becoming more and more and less and less will ever succeed to become pilots (from those who dared to start the training), but anybody that can drive a car, can select up, down, turn left, turn right, go forward, go backwards. This thing could be done so that all “flying cars” would have a data link to other “flying cars” nearby. The computer could automatically avoid collisions without the need of centralized air traffic control at all. Actually air traffic control is a system that can not scale to the level of cars are used on the roads, no matter what. The only way to manage the huge amount of traffic is to not have centralized control at all, but the control would need to be between the aircraft and it would need to be automatic data link, not this antiquated AM radio we are using to call ATC. I think it would be reasonable to make the system such that there could be as many flying cars in the air than there are cars on the ground now. Traffic congestions could be easily avoided because there is lots of space in the vertical plane in the air (when we forget about airspace altitudes and minimum altitudes etc.).

The four rotor configuration would also solve the problem of placing ballistic parachute. It could be directly at the CG and it could be even made automatic, if something fails, parachute would be pulled right away.

So what would be needed:
– lightweight electric motors with high power (already possible with today’s technology)
– fly by wire system (already possible with today’s technology)
– data link to other aircraft (would be already possible with today’s technology)
– combustion engine to charge batteries (already possible with today’s technology)
– high capacity light weight batteries (this might require next generation batteries to have good enough usefulness)

For these to be good for mass market, the following points must be considered:
– it must not require pilot’s license
– it must not require medical of any kind
– it must not be over-regulated, otherwise it will never gain any popularity
– it needs to be very much automatic and very easy
– there must not be super-restrictive regulation where one can land and take off, the usefulness of this concept depends on possibility take off and land from and to everywhere, it would make no sense to take off from airport and to land to airport
– it would not replace airplane, instead one could fly with this kind of machine to airport to get far away with the airplane, I don’t see that this kind of design could be made ultra long range and super fast.
– it is unavoidable that this design actually requires more space still than a car, quite large diameter props needs to be used for efficiency. However, each of them would be more reasonable size compared to one helicopter rotor and less expensive to manufacture. Also four rotors provide more thrust and lower disc loading than a single rotor.

Then how these could be manufactured?
– For mass market I think they should be pressed with 3d molds from aluminium with monococue type construction like cars are made of steel. This should be feasible with today’s technology because Piaggio P-180 Avanti is manufactured from this type of aluminium construction.
– There could be no rivets and there could be no hand layup in anywhere in the structure to make the price down
– The price of high capacity batteries must drop to get the price down
– the electric motors are inexpensive to manufacture in great volumes

So I don’t believe in Möller’s design as such (combustion engines driving ducted fans), but this slightly different version (with helicopter like but shrouded rotors) could possibly be feasible. And these could be made aesthetically to look very stylish unlike helicopters, and they could have bigger mass market appeal also because of that.

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    • slobeachboy
    • October 16th, 2010

    I hate to burst your bubble but the reason we don’t have “flying cars” has nothing to do with technology. The technology has been around for 40 years and I myself designed a workable personal VTOL electric hybrid over 20 years ago. The problem is liability issues. Unlike conventional airplanes or even helicopters a flying car will drop like a stone if there is an engine failure. Of course a VTOL airplane can still glide somewhat if the power fails during normal flight but take offs and landings are still extremely dangerous. If all the cars in Los Angeles today were flying cars, even extremely reliable ones, there would be dozens, if not hundreds, of cars dropping out of the sky and killing people every single day. Of course these vehicles would have parachute recovery systems but these are useless below about 700 feet. The bottom line is, flying cars will NEVER be legal to use over populated areas in my lifetime. Maybe in 100 years when ground traffic is so bad that we have no other choice then we will be allowed to use small personal VTOL aircraft to zoom around town like the Jetsons but not before then. If you want proof just look at the Moller Skycar and similar vehicles that have been around for over ten years. These vehicles all work fine but they have yet to fly any of them untethered. This is because their insurance companies will not allow them to. And as for flying over populated areas the government will not allow it. Even IF they were to miraculously get FAA approval you would still have to take off and land at an airport which kind of defeats the whole purpose of having a flying car in the first place. I’m still planning on building mine someday but it will never be legal so I will have to fly it secretly and only over unpopulated areas and hope I dont get caught. I’m afraid that’s just the way it is and it’s not going to change anytime soon.

  1. Karoliina,The power required to hover is inversely proportional to the swept area of the rotor. That's why Moller's tiny ducted fans need to be powered by 8 screaming RX-7 engines, while homebuilt helicopters with long rotors can be powered by converted Volkswagen Beetle engines (maybe not all that reliably, but they'll get off the ground on less than 75KW.At least in the USA, a "car" must be less than 2.6m wide. If you're going to put the rotor in a duct (and I agree that makes a lot of sense) that limits your rotor diameter to be somewhat less than that — which then means that the power required will be high.This vehicle, the X-Hawk is probably the closest thing to what you have described. It has twin (instead of four) rotors, is a legitimate car-sized vehicle, and has actually flown to a limited extent.

  2. Karoliina,The power required to hover is inversely proportional to the swept area of the rotor. That's why Moller's tiny ducted fans need to be powered by 8 screaming RX-7 engines, while homebuilt helicopters with long rotors can be powered by converted Volkswagen Beetle engines (maybe not all that reliably, but they'll get off the ground on less than 75KW.At least in the USA, a "car" must be less than 2.6m wide. If you're going to put the rotor in a duct (and I agree that makes a lot of sense) that limits your rotor diameter to be somewhat less than that — which then means that the power required will be high.This vehicle, the X-Hawk is probably the closest thing to what you have described. It has twin (instead of four) rotors, is a legitimate car-sized vehicle, and has actually flown to a limited extent.

  3. I was thinking 4 rotors, and 3 needed to keep it up. The disc loading should not be much higher than that of helicopter. The electric motors on each rotor are very reliable and on the other hand can have lots of excess power for emergency (if one motor would fail). The idea is to have on these four rotors equal disc area than a helicopter has or at least close to that.It really does not make sense to limit to 2.6m wide because the idea is not to drive on road ever. The idea of this is that it replaces car, but is not a car that is driven on a road. The only "car" requirement was to be able to fit to a parking place of some sort and to not require airport for takeoff and landing was a car style requirement. However, I was not thinking about needing to drive these on road.The idea is not to use ducted fan, but rather shrouded prop. However, it might after all make sense to not have this shroud at all because it causes drag on cruise. At least three rotors are needed to keep the craft stable on hover.

  4. Karoliina,I love the thought of the type of society that you have in mind. Less regulation would work only if laws for corporations were no longer promoted over laws for the good of the people by governments. What about sea-based shopping villages, accessible by watercraft, hovercraft, ground effect craft, or personnal commuter aircraft?What if you had 1-2-3 or 4 'frisbys' with a hole in the middle of the top of the frisby and with a fan in each and a slightly conical solid surface above the frisby (separate from and over the top of the frisby), with enough speed & volume of air moved between the solid top surface and the top of the "frisby" that a greater air pressure would exist below the 'frisby' than on top of the craft, sufficient to provide at least ground-effect lift. Craft would look similar to the "inexpensive" personnal aircraft in your blog a few posts down, but modified to provide VTOL (so it won't end up cutting any fences on landings and take-offs) and without the fuel cost of a kerosene-guzzler vectored jet engine. Fans could be vectorable, but they needn't be. Like Thad's X-Hawk, separate fan(s) could be provided for the forward vector (push or pull) and use the unibody wing/cockpit for lift with simple rudder(s) for changing direction. Once the vehicle sustains it's own lift feather the fans under.Has anybody mentioned the obvious advantages of using Aerogel as the main construction material for such a craft? http://www.youtube.com/watch?v=kHnen2nSmDYProvide smaller pieces of Aerogel (like the bones of the skull or shell of the turtle) which stay in place but are flexible enough to take some localized impacts without fracturing, covered with (carbon-fiber?) skins top and bottom. Provide two such composite surfaces separated by a 3D frame to create the unibody craft, similar to the top & bottom shell surfaces of a crab. Frame members constructed as compression struts capable of absorbing impacts. Modify shape of unibody to closer approximate NACA 66-020 airfoil, also as you have previously mentioned.If going with battery + electric motors, maybe the sodium ion batteries would be worth looking into? http://renovomedia.com/technology/new-sodium-ion-battery-promises-cheap-energy-storage/ Cover upper surfaces of craft with flexible laminated photovoltaic membrane. Like: http://www.uni-solar.com/wp-content/uploads/pdf/PVL-144_EN.pdf orhttp://www.bigfrogmountain.com/PowerFilmSolarProducts.htmlMain thing I'm not understanding is the electric motors. Motor efficiency, drawing fewer input amps to do more output work, especially considering constant duty and potentially adverse conditions, is associated with those big, heavy, multi-phase beasties. http://www.baldor.com/products/detail.asp?1=1&page=46&catalogonly=1&catalog=EFM2543T&product=AC+Motors&family=Premium+Efficiency%7Cvw%5FACMotors%5FPremiumEfficiency&winding=42WGW387&rating=40CMB%2DCONTThat is only a 50 HP motor, half the power of the 75KW VW engine Thad mentioned. Don't the lighter electric motors sacrifice both efficiency and durability? Are there motor improvements you all are aware of that I haven't heard of yet? There's an Advanced Power Technology (APT) group in Bend, Oregon that designs, manufactures, and markets high performance power semiconductors for electrical power conversion, control, and amplification. http://www.chipdocs.com/manufacturers/ADPOW.html My brother worked there for awhile, and as I understood it, one way they were able to power motors more efficiently was by taking normal AC line current and converting it into whatever number of phases you want, with a simple switch, without wasting any of that input current. Are there other motor designs or technologies effecting motors that exist these days?

  5. >Hello Karoliina,This flying car as you are thinking I guess should work and would be great. But I believe that there are just to many of us and this device would just be to big & noisy & “windy” for daily common use. I rather think that the near the future of personal air travel will be multimodal use/integration of mobility devices used at their optimum in terms of efficiency. Helicopters, whatever their configuration, will never be very efficient. The corner stone could be automated & shared cars (autonomous cars). They would allow to connect the STOL site you have flown to fast & efficiently with your next gen airplane (for instance the Twin R Dynaero or the 4 seater pipistrel is developing) in semi-automatic mode (and with Gps-IFR approach) and then easily ride to your final destination (the autonomous car waiting for you at less cost than a taxi or current rental car). For shorter trips & shopping these autonomous & shared cars will be unbeatable (your personal cars stand still in the street 90% of the time). My point is that these cars will make personal airtravel time-economics feasible/interesting even for small aircraft and on small/little equipped airfields and thus fully deploy its time saving potential.See also: http://en.wikipedia.org/wiki/Driverless_carGreat out of the box blog you are doing.MichaelI fly Robin DR250 (&love the MCR01)

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