Flying cars; a new dawn in automobile technology.

Automobile technology had just begun another phase of its revolutionary development with the emergence to reality, the long-awaited dream of automobile designers and technological inventors- a dream to see cars taking off from the road and float in the air, flying above ground surface. Brad Templeton, with due reference and acknowledgment, wrote extensively on the advent of flying cars, their types and the technologies used in their production. He described a number of the many different designs of vehicles being developed. ‘Here I want to go over some of the key design choices being made, and the merits of them, to help understand who is most likely to win.   There are a lot of variants, a sort of Cambrian explosion, which breaks down on the following choices.

Designs from just rotors, or rotors with fixed wings

The multirotor "drone" is now well understood and "solved." We know how to build it. It's not very efficient, because the range is limited on batteries. Because this is well understood, the first vehicles getting off the ground are just pure multirotors, such as the Volocopter (with 18 rotors) and the eHang. There's also a sub-category of this, the "hoverbikes" which are even more like a consumer drone as they only have a basic single seat which is exposed, often above the rotors. This includes Kitty Hawk's first vehicle, the "Flyer."

You'll see more early press for these because it's a lot easier to make one. While it's not quite that easy, it can be viewed as scaling up existing multirotor work to build something that can handle 200-400lbs of "payload" and fly for 30 minutes. There is a limit, because as the battery gets bigger (to carry more payload and get more range) it gets heavier, reducing payload and range while increasing cost.

The biggest problem is that a pure multirotor, even worse than a helicopter, just isn't that efficient. The designs with decent range tend to be hybrid-electric powered flying crafts, as shown below.

The volocopter is an all-rotor ("drone") style vehicle that's actually flying. It has a shorter range but the design is simpler.

 CREDIT: NIKOLAY KAZAKOV FOR VOLOCOPTER

That's why a large fraction of teams are working on dual-approach vehicles, which take off as multi-rotors, but also have wings and convert once off the ground to regular fixed-wing flight. The wings are not needed for traditional take-off, don't need to be nearly as big as they are on traditional aircraft.   In addition, with the rotors running, they don't stall.

Tiltrotor (and other directed thrusts)

Airbus Vahana fixed/rotor tilt-wing in test flight

 CREDIT: AIRBUS

The oldest design for dual rotor/wing flight is the tilt-rotor. Big rotors point up, and can be tilted forward.   The V22-Osprey is infamous for this design due to its fatal accidents. Nonetheless, the expertise learned from building that at Bell Helicopter has led them to their Nexus design which uses tilting enclosed fans. Other designs mount the rotors on wings, and tilt the whole wing assembly. The Lilium Jet puts them in a tail assembly and tilts them.

Lilium Jet's vision has a large array of tilt-able ducted fans and a claimed very high speed and range

 LILIUM

The trick -- you must safely tilt the rotors at take-off and landing.  It's not easy.

Pusher prop

If you don't tilt the rotors, you can also fly by adding an additional more traditional propeller, usually at the back. This is the design of the Kitty Hawk Cora, and several other aircraft, including the Elroy cargo plane. The latter (a hybrid fuel design) uses the gasoline engine to drive the pusher prop directly.

Kitty Hawk "Cora" in a test flight with 12 rotors for VTOL and a pusher prop for fixed-wing flight. It's testing in New Zealand

 CREDIT: KITTY HAWK

This design has a simple -- no tilting, which can be a big problem if it fails. It does mean all the rotors stay still for most of the flight, providing drag instead of thrust or lift.

The Opener "Blackfly" is flying today, and they claim it will be for sale in 2019. The design is very simple, with 8 rotors. The whole aircraft tilts for fixed-wing flight.

 CREDIT: OPENER

All-electric or hybrid technologies

Central to the VTOL revolution is the use of electric propulsion. This allows a whole new kind of VTOL different from old-school helicopters. Today, batteries are only barely good enough, so range and size are limited. One alternative is to install a generator, usually gasoline or Jet fuel powered, in addition to the batteries. You still need the batteries for the peak power of VTOL, and to get you down safely if the generator should fail. Because you now are less concerned with generator failure, you can have a motor that's not nearly as robust and expensive as regular aircraft engines.

Gasoline is popular choice because of its availability. At the same time, it's not as easy to put gasoline re-fuelling stations everywhere, including on the tops of buildings and at private landing spots. Electrical recharge stations are easier to get approval for.

One concern and disadvantage of this approach is that, it is hardly green. People don't want to develop new transportation that pollutes more than what we used before.

Another alternative, not yet common, is the use of fuel cells. Hydrogen is a very dense fuel when it comes to weight, though it does require bulky tanks. It's also not easy to find it or refuel with it. Today, fuel cells are quite expensive, so you still need batteries for the VTOL and emergency landings.

Design thoughts, Big, Small or no Wheels

Some teams are taking the term "flying car" literally -- they want a vehicle that can move on the ground on wheels, and get small enough to drive on roads and park in automobile parking facilities and even home garages. Others want the vehicle to be able to just make small movements at the landing port, for example to move to parking facilities or charging facilities. Others plan for no wheels -- the vehicle sits where it lands.

There are complex trade-offs. One big issue is where you put all the vehicles if they don't have the ability to drive. Many of the designs, while not large, still are the size of 4 or 6 cars. If there are a million of them in a city, there's no place to easily put them. Even if there are 100,000 it's an issue. They can move in open areas, hover-flying to the charging or refueling ports, but can't be anywhere they can't land at. They can take off and go to other lots when they need to wait if they need to clear a heliport, but they can't take you on the road.

On the other hand, wheels and the ability to drive add moving parts, complexity and worst of all, weight. Weight is precious. Every kg costs a kg of payload or battery. We're right on the edge with giving these things a decent range and payload, and wheels, motors and everything needed to be road legal create a serious challenge.

Instead, it may be best to say a flying vehicle should be a flying vehicle and a car should be a car. The flying vehicle can land and you step out of it into a robotaxi. It's not a big inconvenience. The car is a car and the plane is a plane.

One odd hybrid approach from Airbus is to have a "passenger pod" which can either be picked up by the flying part, or be deposited on a driving cradle with wheels. So your pod flies with gear above it, and then it is landed by placing into the driving base. The rotors detach and fly away to land on another vehicle, while the pod clamps into the base and can drive away. This solves the problems of weight but has a lot of complexity, and you can only land where there are pods.

A full road vehicle faces a major challenge that road vehicles must be certified for safety on the road, and this requires a lot of weight.

Some designs, like the Opener Blackfly, can also land on water and grass. They have no wheels and can't move on land at all.

The Terrafugia Transition is a traditionally fixed-wing airplane that flies on gasoline, except it folds up to drive on the road

 TERRAFUGIA

One of the oldest designs, the Terrafugia Transition, flies strictly as a fixed-wing airplane whose wings fold up so that it can drive on roads with its wheels. This is the old-school (practical) idea of a flying car but due to e-VTOL, even Terrafugia has moved to other designs.

At present, only a very few designs have wheels or seem to have a plan for them.

Runway or not

Some vehicles still want to use a runway. After all, airplanes that use runways are a solved problem, and they can be efficient. The original Terrafugia named above is a classic example. Multirotor takeoff is loud and uses a ton of energy. Runways use a ton of land, and they are few. One answer here is the combination of robotaxis with autonomous fixed wing planes. The Robotaxi takes you right to the plane, you do a very quick switch, and off you go. Same at the other end. This allows vehicles with high efficiency and long range, nothing to be sneezed at.

The Pal-V gyrocopter/car shown with rotor folded and parked in a garage.

 PAL-V

A few other players are interested in autogyro designs. Autogyros are also very old technology, and they are available today. They need a very short runway to lift off and land. So short that many parking lots or even tops of buildings can suffice. They are not as efficient as fixed-wing

aircraft, though, and the fact that they are more efficient than helicopters used to be a selling point for them, but it's not as much of one today.

Nonetheless, the Pal-V Autogyro/flying car is actually taking orders today, which is more than most vehicles can say.

Exposed blades, protected blades or ducted fans

Some designs have exposed rotor blades, and some try to embed them in the body, in shields, or inducted fans. Protecting them can reduce risk to pedestrians and noise, but can add weight and interfere with airflow. Ducted fans can produce strong thrust if you do them right, but it's difficult to achieve

Bell Helicopter nexus, with six giant tilting, enclosed fans

It is unclear if safety regulators will tolerate exposed blades which could hurt people, particularly if vehicles are landing in driveways and uncontrolled parking lots as many people wish them to.

Licensed pilot, drone operator or autonomous

Everybody hopes to make fully autonomous taxi vehicles eventually. There's no way to do that under current law, and it's also not a solved problem. Some vehicles will be released first for use only with a licensed pilot. Due to battery weight, it is hard to qualify them as "light sport airplanes" that need a lesser pilot's license, or as ultra-lights, but there are suggestions the FAA may change the weight rules to deal with battery-electric vehicles that were never anticipated. If they do, this will let these vehicles get "off the ground" and into the hands of customers before automation is ready or legal.

There is some speculation that the ones that are most like drones might be flyable with the basic drone pilot's license meant for remote-controlled drones, but I'm not sure if that will apply beyond testing.

Multi-passenger taxi or private vehicle

A few years ago, the transport company uber announced a major initiative to get companies to develop air taxis that Uber could run to move people from heliport to heliport. Uber Elevate specified vehicles with 4 passengers and a pilot (no automation for now) and mostly flying from building rooftops in denser cities to get over traffic. That's one vision -- and has resulted in many vehicle designs. Doing this with just batteries is a challenge. At the same time, many others have had focus on the personal vehicle, with 1-3 passengers and autonomous flight. These are intended either for private ownership or short urban taxi service.

Flying, model, prototype or dream

The Hoversurf is a great example of the hoverbike design -- minimalist and for one person. Here they demo for the Dubai police.

 HOVERSURF

While there are close to 100 projects out there, and more in stealth mode, they are at different stages of development. Just 3 are taking orders or selling. Only a handful have full-sized flying vehicles capable of traveling any distance. A few more have full-scale prototypes but have only done the vertical flight. On the other hand, some of the companies involved like Airbus, Boeing, Bell Helicopter and Embraer have extensive resources and aviation experience. A few more companies have flying scale models. The rest of the 81 companies transport up listed have only engineering designs and computer models. The first vehicles to go into production are the older designs (like the Pal-V and the Terrafugia,) the rotor-only vehicles (like the Volocopter and some of the hoverbikes) and quite possibly the Blackfly, which claims it will be for sale this year in the range of $70,000.

So what wins?

There are arguments behind all these choices. However, I believe the likely winning designs will be:

1.    Dual multirotor and fixed wing, to provide efficiency and range

2.    Small and able to move to some extent to places where they wait for passengers, but not able to drive more than a short distance on roads

3.    Protected blades so they can land in a wide variety of places and be quieter

4.    1-2 passengers to stay small and light

5.    Tilt plane or push rotor to avoid the complex moving parts of tilt-rotor

6.    Initially needing a pilot, ideally a limited pilot's license.

But for now, let a thousand designs flourish. let me guide you on more innovative designs from spontaneous thoughts of modern designs and production of automobiles that would amaze the world. then we shall be discussing what problems or challenges are we as human and the society like to face with the advent of this modernity in the world of the automobile. You can post your comments and let's share ideas together.