快猫短视频

鈥楳ark my word: a combination airplane and motorcar is coming. You may smile, but it will come.鈥� Henry Ford, 1940

SOMETIME in the next few weeks, an unusual car will make its maiden journey in the grounds of Moller International, an aviation company based in Davis, California. Like most cars it has room for four passengers, and like some gas guzzlers it travels just 8 kilometres on a litre of petrol (roughly 20 miles to the gallon). But unlike any road-going vehicle, it has the shape of a Batmobile and a top speed of over 600 kilometres per hour. There is one other unusual thing about the 鈥淪kycar鈥�: it takes off and lands vertically. On its first flight, the Skycar will rise to a height of 2 metres or so, hover for one minute and then land, just like the Harrier jump jet.

Flying cars have been the stuff of dreams since the Wright brothers took off in 1903. Many people have tried to build them and a few have even created working vehicles, such as Robert Fulton鈥檚 1946 鈥淎irphibian鈥�, a plane whose wings and tail could be removed, leaving a car. However, these craft could only be flown by somebody with a pilot鈥檚 licence, and even then only from one licensed airfield to another. Such limitations have always killed the dream in the past.

But things are different this time round. The US is examining ways of setting up an advanced control system for small aircraft that would allow them to be flown entirely by computer. With this infrastructure in place, passengers will not need to know how to fly at all but will travel in the hands of a computer from take off to landing.

Once this is possible, the Skycar will be the answer to the world鈥檚 traffic problems, say its makers. Commuters will no longer sit nose to tail on gridlocked roads but fly effortlessly above them, like the characters in Blade Runner or The Jettsons. And with a 200-kilometre journey taking just 20 minutes, the company believes that flying cars, or volantors, will radically alter the way people choose where to live. Skycars could change the nature of cities and the lifestyles of those who live in and around them.

The man behind the Skycar is Paul Moller, the engineer who founded and runs Moller International. Moller鈥檚 fascination with aircraft began as a boy, when the darting movements and agility of hummingbirds caught his attention. While growing up on a farm, he built many machines, including a car and even a Ferris wheel.

Moller began building vertical takeoff and landing vehicles in 1963, soon after he started teaching engineering at the University of California, Davis. His first attempt was a flying saucer-like craft he called the XM-2. Although powerful enough to take off, it was unstable in flight. His next attempt was another circular vehicle in which the pilot sat at the hub of a giant fan.

Moller soon realised that the biggest obstacle to making a practical flying car was power. What he needed was a small, light engine that could produce a lot of thrust for its weight. The engine would also have to be fuel-efficient and vibration-free. But such an engine simply didn鈥檛 exist. 鈥淎s far as getting something into the air that carries a decent payload, it鈥檚 really about developing engines. I鈥檇 say that has plagued me since 1963,鈥� he says.

In 1965, Moller plumped for the Wankel rotary engine, in which a triangular rotor turns inside a combustion chamber, instead of having pistons pumping up and down inside cylinders like a normal engine. This engine operates with only a couple of moving parts and so has the potential to be extremely reliable. In Moller鈥檚 design, the rotor turns a shaft connected directly to the blades-or the fan-that generate thrust. The rotation rate is controlled by throttling the engine but the optimum rate for both engine and blades is about 6000 revolutions per minute. So there is no need for gears, which would reduce the engine鈥檚 efficiency. To cap it all, Wankel rotary engines are clean and lightweight, and can be modified to run on natural gas or alcohol as well as petrol.

It has taken Moller more than thirty years to come up with the Skycar design, and he is still tweaking it. In 1985, he bought the technology behind a Wankel engine made by the Outboard Marine Corporation in Waukegan, Illinois. Four years later, he used the engines to create a circular two-passenger aircraft called the M200X. Moller has flown this vehicle more than 150 times at altitudes of up to 20 metres. 鈥淭his is truly a magic carpet ride, because you are sitting on top of it and it lifts you up,鈥� he says. During each flight, the M200X has to be attached to a crane, by a wire because neither Moller nor the vehicle are licensed to fly. 鈥淵ou can still do pretty much what you want,鈥� he says. 鈥淵ou can take your hands off the controls and stay where you are. You can decide where you want it to go and it鈥檒l go exactly where you want it.鈥�

His most recent version of the Wankel rotary engine is about the size of a bucket. Moller places two engines, along with their fans, inside streamlined housings known as nacelles. The fans rotate inside the housing creating an airflow that generates thrust. At the rear of each nacelle is a set of vanes that can be angled downwards to generate lift as well as forward thrust.

A single fan tends to make the airflow rotate, which reduces their efficiency. But this can be offset by mounting the two engines back to back in each nacelle, so the two fans counter-rotate. 鈥淭his straightens out the flow,鈥� says Jack Allison, an engineer at Moller International. It also provides some of the redundancy needed to make flying cars safe: if one engine fails, there is always another to provide power.

The four-passenger M400 Skycar has four nacelles, which provide plenty of power. The eight engines generate about 12 000 newtons of thrust altogether, which is more than enough to lift 1000 kilograms, which is about what a fully laden Skycar will weigh.

Beetle shell

During flight, however, the M400鈥檚 body will provide most of the lift. The vehicle is slightly wider than an average car, about as long and tall as a medium-sized van. To save weight, instead of having an internal airframe, the shell of the vehicle bears all the forces during flight-a bit like the exoskeleton of a beetle, Moller points out.

The shell consists of a honeycomb structure sandwiched between two layers of carbon fibre. Extra layers can be added depending on the vehicle鈥檚 purpose. For example, a military vehicle such as a flying jeep could be reinforced with more Kevlar.

The Skycar鈥檚 unusual shape (see Diagram) is the result of thousands of hours of testing in wind tunnels. The goal was to make every part of the vehicle generate lift as it moves through the air. At a speed of 250 kilometres per hour, the engines produce only a tenth of the lift. Nearly half of the lift comes from the four nacelles鈥揺ven the vanes that direct the airflow generate lift. Another 16 per cent comes from the fuselage and about a third comes from the rear wing.

The first Skycars will be fly-by-wire vehicles. In other words, while the pilot tells the craft what to do, a computer will actually do the flying, taking the vehicle鈥檚 rate of turn, its altitude and attitude into account when it responds to instructions. The pilot controls the altitude and rate of climb with the left hand, while the right hand controls the direction of flight and airspeed.

In future, the designers intend to add infrared and low-light video sensors, and a headset that beams images directly into the pilot鈥檚 eyes. This would show pilots an enhanced image of the scene ahead if visibility is poor. This kind of system is already being designed for the military by aerospace companies such as Allied Signal. 鈥淲e want to be able to land in grandma鈥檚 backyard at night, in thick fog, without hitting the clothesline,鈥� says Allison.

Safety, of course, is vital if the Skycar is to succeed. With eight engines, the M400 can still fly even if one or more fail. There are also two independent computers in case one malfunctions. And in addition to all these backup systems, the Skycar will have two parachutes. It will also have airbags both inside and outside to soften emergency landings.

And a Skycar can fly without power to some extent, Moller says. 鈥淚t has a good glide path, but not one that you could land with, because it鈥檚 too fast. You can glide around until you find a place where you can pull the parachute.鈥�

Moller and his colleagues intend to test the M400 behind closed doors in the next few weeks and hope to demonstrate it to the press before the end of the year. During the first flight with Moller at the controls, the Skycar will rise to a height of two metres or so, hover for one minute then land. Later flights will be more ambitious. Once the aircraft receives a licence from the Federal Aviation Administration (FAA) anybody with a pilot鈥檚 licence will be able to fly one in the US.

The first Skycars will be hand-built and so will sport price tags of about $1 million. But Moller believes that mass production, Henry Ford-style, will bring the price down. He reckons that a four-seater could eventually cost as little as $60 000.

Another problem that Moller must tackle is noise. Residential areas usually tolerate noise levels about the same as background traffic-up to 70 decibels-but the Skycar generates about 85 decibels. Moller is looking at ways to reduce noise, by carefully avoiding resonances and by using noise cancellation techniques. Even so, Moller admits it will be difficult to reduce noise levels to below 70 decibels.

So the vehicles will initially have to take off and land at tiny airports-or vertiports-far enough away to reduce the noise. City centres are likely to tolerate more noise but will also need vertiports to handle this traffic. Since vertiports could be so small, Moller believes it will be easy to set up thousands of them all over the country.

Moller鈥檚 ultimate goal, an entirely computer-controlled Skycar, will require a more advanced flight-control system. According to Bruce Holmes, manager of the General Aviation Program Office at the NASA Langley Research Center in Hampton Virginia, such a system is on the way. Various organisations, including NASA, the FAA, the Department of Transportation, individual states and aviation-industry groups, are developing a small-aircraft transportation system, or SATS.

The idea is to create a system that would allow aircraft to keep track of their location and the location of other planes by using the Global Positioning System to determine their position and broadcasting this information to a central computer. This computer could then tell one aircraft where others are.

SATS is not being created for flying cars, of course. Its aim is to allow conventional aircraft to use small airports without radar or control towers and in all kinds of weather, to relieve larger airports of some air traffic. Nevertheless, the technology behind SATS could eventually be used to create Skycars that could fly from one spot to another without a human pilot. Passengers could simply tell the onboard computer where they want to go and sit back.

鈥淭he technology, relatively speaking, is the easy part of this,鈥� Holmes says. 鈥淭he hard part is going to be public policy. How do you get Americans to realistically look at small aircraft for transportation like they look at their cars, like they look at the airlines?鈥� Right now, no one knows the answer to that question. And without widespread backing the Skycar could fade into obscurity like all its predecessors.

Some of that support could come from other users. Dennis Bushnell, chief scientist at the NASA Langley Research Center, believes the Skycar could have a big impact in the developing world, where it could make expensive roads and bridges redundant. It could also act as a robotic delivery vehicle that might be used by, say, an overnight carrier. 鈥淎nd for years the army has tried to develop a flying jeep. Moller has a flying jeep, which is automatic so you don鈥檛 have to train soldiers to be pilots,鈥� says Bushnell. 鈥淭he combined market for this is estimated at, at least, $1 trillion a year.鈥�

As prices fall and automated flight-control systems come on line, Skycars could quickly become a popular form of transport. Nobody can say exactly when-or if-that will happen. But when the first Skycar takes off in the next few days, Henry Ford won鈥檛 be the only one smiling.