Electric Planes on the Way With Greener, Cheaper Flights

NASA and other aircraft developers are looking for ways to drop the cost of fuel and lower the emissions for short-haul flights.

The test flight of two small electric aircrafts earlier this month across the English Channel has got us wondering about when we'll get to ride in one of these clean, green planes.

While it may be a while before we board a cross-country electric flight, a short hop to the islands off Cape Cod may be more realistic. Engineers at NASA are working with Barnstable, Mass.,-based Cape Air to develop an Cessna 402 9-passenger electric airplane suitable for the short hops to the islands of Nantucket and Martha's Vineyard, a flight of less than an hour from airports in New York or Massachusetts.

NASA officials say they still have a way to go however before they start selling tickets. They are working on a prototype at the Armstrong Flight Research Center at Edwards Air Force Base. It's a strange-looking device that resembles the old-fashioned flying wing developed after World War II. A row of electric motors line the front-edge of the wing, providing lift power.

"We can make the wing smaller and more aerodynamically efficient," said Matt Redifer, chief engineer for NASA's Scalable Convergent Electronic Propulsion Technology Operations Research (SCEPTOR) project. "We then use motors across the leading edge as a lift device and you get a much larger benefit from electrifying the aircraft."

The wing is a testbed for a bigger prototype aircraft. Redifer and his colleagues are transforming an existing aircraft into an new electric one, using an Italian-made twin-engine, four-passenger Tecnam P2006T.

"We are looking at the whole system, instead of just replacing engines with electric motors, we are looking at a design that couples electric propulsion with a redesign of the wing."

Using multiple motors on the wing gives more efficient lift and propulsion, he said. The NASA project is currently testing the new wing design mounted on top of a big truck that is driving around the dry lakebed near Edwards AFB, the same areas where the space shuttle used to land.

In contrast, the Airbus E-Fan that made the Channel crossing on July 9 was a single-seat aircraft. The push for electric drive propulsion is coming from aircraft manufacturers who anticipate more rules cutting back on carbon pollution from jet aircraft.

The Environmental Protection Agency said in June that carbon emissions by airlines contribute to climate change, and new regulations could be ready by 2017. The European Union has started charging some airlines for CO2 emissions.

NASA's research could pave the way, according to Redifer, and its aircraft is scheduled to be ready for flight testing in 18 months.

"What we are looking at with this four passenger aircraft, expecting anywhere form 800 pounds of batteries with takeoff weight of 3000 pounds," he said. "That gives us enough range to prove that we can get this five times energy reduction (over existing jet propulsion)."

Redifer and others admit that the big issue to overcome for electric airplanes, just like electric cars, is battery life.

Aircraft fuel is more efficient since the airplane gets lighter over time as the gas is burned. Electric airplanes will have to haul around large packs of lithium iron batteries, a scenario that has caused aircraft fires in the past and led to warnings by the FAA.

"The idea of an electric plane is attractive," said John Hansman, director of the International Center for Air Transportation at the Massachusetts Institute of Technology. "But electric cars can only go a couple hundred miles, and electric planes will have about same range as electric cars."

Hansman and others foresee an electric hybrid drive using a small amount of fuel to generate electricity that powers the electric motors. This, coupled with the steady improvements in battery technology could lead to a real change in transportation, according to Brian German, associate professor of aerospace engineering at Georgia Tech.

In the long run, the combination of electric propulsion and automatic flight controls and self-guided navigation will make flying an aircraft much cheaper and easier. Call it the Uber of airplanes.

"With new technology, the cost drops out the bottom and maybe we open new markets," German said. "If you can reduce the pilot workload and degree of training with autonomy, then you open the possibility for on-demand aviation. The airplane flies to the airport and picks you up and takes you somewhere."

Within a few years NASA hopes to fly a piloted X-plane, replacing the wings and engines of a Tecnam P2006T with an improved version of the LEAPTech wing.

Technology moves faster every day. But commercial air travel hasn't changed as quickly as some industries in recent years. Experts project big changes in the next few decades, though, especially as aviation companies deploy significant innovations in design, material sciences and alternative energy sources. Here we take a look at some of changes on the horizon for commercial, cargo and experimental aircraft.

The N3-X concept aircraft, from Boeing and NASA, is based on a blended wing body (BWB) design intended to improve aerodynamics, fuel efficiency and noise emissions. The ultra-wide fuselage would greatly expand carrying capacity for commercial flights.

Developed by a research team from the Massachusetts Institute of Technology (MIT), the D8 "Double Bubble" aircraft would be used for domestic flights and is designed to fly at Mach 0.74 carrying 180 passengers in a coach cabin roomier than that of a Boeing 737-800. The D8 could enter service as soon as 2030, NASA says.

From Lockheed Martin, this concept design for a future supersonic aircraft is focused on reducing emissions and creating a quieter boom. A quieter craft would allow supersonic flights over land, where they are currently prohibited.

Meanwhile, over on the cargo plane tarmac, the GIGAbay concept envisions a ginormous aircraft powered by four hybrid fuel/electric engines, with supplemental energy provided by hydrogen fuel cells, wind generators and solar panels. The cargo area of the GIGAbay design is so large it could carry other jumbo aircraft, or even mobile field hospitals.

Powered by two superconducting electric motors, the concept plane known as the VoltAir (get it?) is a proposed all-electric airliner out of Europe. The engines would draw from next-generation lithium ion batteries -- really big ones -- that would be simply swapped out between flights.

Some cutting-edge technologies on the horizon are actually modifications of existing designs that have been around for more than a century. To wit, the illustration above imagines the closed-wing "PrandtlPlane" design applied to commercial passenger aircraft. Closed-wing planes have smaller wingspans than traditional aircraft, relative to fuselage size, allowing larger planes to operate out of smaller airports.

Another sort of hybrid, the E-Thrust design -- from Rolls-Royce and several European partners -- uses a combination of gas-turbine engines and battery-powered fans. The jet engines would only kick in when needed, similar to gas/electric hybrid cars. The fans would also be used, on descent, as built-in windmills to recharge the onboard batteries.

And from the ultralight division, we have the Solar Impulse 2, the latest iteration of the world's most advanced solar-powered, single-seat aircraft. The Swiss team behind the project plans to circumnavigate the planet in 2015, using a team of pilots flying in shifts over the course of about five months.

Finally, from the designer who brought us the GIGAbay cargo plane, the mighty Sky Whale also subscribes to the concept that bigger equals better -- and greener. The Sky Whale is a largely theoretical vision for a passenger plane that could seat 755 passengers on three floors, using a combination of alternative power sources. The upshot? More passengers per flight means fewer flights, and fewer emissions.