Can vertical takeoff planes replace cars?

The end of the jet age could be in sight. Innovative new electric aircrafts are starting to find their way off the drawing board and onto runways, funded by start-ups, government agencies and the world’s biggest jet makers. They promise flights that are cleaner, quieter and safer than today’s jets, and with a fraction of their carbon footprint.

Earlier this month, Nasa announced that it would be building a high-speed research aircraft called Maxwell that would use electric motors to drive 14 propellers. The four-seater aircraft should be able to fly at speeds of up to 280 kmph (about as fast as many small aircrafts), using a fifth of the energy of a normal private plane.

“Eventually, Nasa would love to replace airplanes like the Boeing 737 or Airbus A320 that represent a large fraction of civil aviation,” says Jack Langelaan, a professor of aerospace engineering at Penn State University. “A huge proportion of today’s emissions and fuel burn comes from these kind of planes.”

Commercial aviation already accounts for 2 per cent of all man-made CO2 emissions, a figure that could rise to 22 per cent  by 2050. Electric aircrafts could slow this trend, or even roll it back.

For a start, electric motors are about twice as efficient as internal combustion or jet engines. “All you’re doing is running wires to motors,” says Carl Schaefer of Aurora Flight Sciences, an aerospace company developing an electric drone called Lightning Strike for the US military. “So instead of one large propeller, you have the freedom to place small motors anywhere on the aircraft.”

Maxwell will have 12 propellers on the wing, and two more mounted on its wingtips — each with its own motor. This configuration enables it to boost fuel efficiency even further — and adds safety. “Having one engine fail during takeoff when you’re using 14 is much less severe than having one fail when you only have three,” says Sean Clarke, one of Maxwell’s designers.

Aviation start-ups have also been quick to realise that electric motors can enable new vertical takeoff and landing (VTOL) aircrafts to replace cars rather than planes. “Vertical takeoff is popular because if we’re going to use these vehicles for commuting, no one wants to land at an airport five miles away from work,” says Langelaan.

German start-up Lilium’s two-seater needs a landing zone no larger than 15 square metres, while Joby’s S2, under development in California, tilts 12 rotors to take off vertically, then converts into a conventional plane. Joby claims the 321 kmph plane will use five times less energy, door to door, than a petrol-driven car.

The Volocopter, another German prototype, has 18 helicopter-style rotors, while Chinese firm EHang’s 184 aircraft resembles an oversized single-person drone. The ultimate aim of such aircrafts is on-demand aviation, an Uber for aircraft that provides automated pilot-less aerial transport around, and between, congested cites.

EHang has already got permission to start testing its autonomous 184 aircraft in Nevada, although not with passengers on board.

“There are a lot of things we need to get sorted out to make this work,” says Langelaan. “Collision avoidance and traffic management are important. It’s a big sky but once a lot of these little airplanes start flying around, the sky will start looking an awful lot smaller.”

— Source: www.guardian.com