Pictures: Five Future Techs for Passenger Air Travel

The Next Concorde?

Illustration courtesy Lockheed Martin/NASA

Shaped like a giant dart, Lockheed Martin's Supersonic Green Machine, illustrated here, would be capable of cruising at speeds of more than Mach 1.6, or nearly twice the speed of sound.

If built, planes such as the Supersonic Green Machine would be the successors of the Concorde and the Tupolev Tu-144, the only supersonic plane designs to fly commercially. The Concorde, however, was an economic failure because of its expensive upkeep and the high cost of a ticket, which could run to several thousands of dollars.

Due to engineering advances, a supersonic airplane could be built better and more cheaply today, IMechE's Oldham said. "The Concorde was ahead of its time in terms of its engine design and the materials it was using," she said. "I think we could make it more affordable now."

Also, today's increasingly global economy could make the idea of supersonic aircraft popular again, said David Gillen, a transportation policy expert at Canada's University of British Columbia (UBC).

"If you look at the growth of the Indian, Chinese, and Brazilian markets, those are going to require a degree of connectivity" that would benefit from faster travel times, said Gillen, who was not involved in the IMechE report.

(Also see "First Green Supersonic Jet Launches on Earth Day.")

Published November 10, 2011

Scrambling for Power

Photograph courtesy NASA

A SJX61-2 scramjet engine is tested in a wind tunnel simulating flight conditions at Mach 5, or five times the speed of sound, at NASA's Langley Research Center in Virginia in 2008. (See "U.S. Developing Jets That Fly Five Times the Speed of Sound.")

Scramjet engines have no moving parts and instead simply suck in all the oxygen they need from the air to burn hydrogen fuel. However, to gather air that is compressed and hot enough for ignition to occur, scramjets work only at very high velocities—Mach 5 or greater.

(Related: "Fuel Cells-Energy Source of the Future.")

Because of the huge technical hurdles that still need to be overcome, UBC's Gillen said he doesn't expect to see scramjet-powered commercial planes any time soon. "We don't even see those kinds of things in the military, at least not publicly," he said.

Oldham agreed that hypersonic aircraft are probably a long way off, but she thinks there might one day be a scramjet-powered commercial airplane, with production beginning as soon as 15 years from now.

"Everything tends to flow into the commercial and civil aviation market from the defense market," she said.

Published November 10, 2011

Taking a Page From Nature

Photograph by Paul Bowen, Science Faction/Getty Images

Four corporate jets fly in close formation above New Jersey in this undated photograph. In the future, planes on overseas or long-haul flights could fly in V-shaped formations for fuel savings of up to 12 percent, according to the IMechE report.

Geese and other birds use this strategy to save energy on long flights. As air hits a bird in flight, it flows down the wings and creates vortices, which impose drag on a lone flyer. When flying in formation, the birds behind can ride on top of the vortices created by those in front, reducing drag on the overall formation. (Related: "Quieter Aircraft to Take Cues From Birds, NASA Expert Says.")

Engineers have long wanted to try out formation flying with planes, but the difficulty has been gauging lateral distances between the planes well enough for them to safely fly so close together.

"I think we have very good instruments for understanding vertical distances" between stacked planes or between planes and the ground, Gillen said. "We're improving a great deal with lateral distances, but there's still a certain amount of variability."

IMechE's Oldham thinks the technology to enable formation flying is almost ready: "Due to the advancement in avionics technology, airplanes can now almost lock on to the plane in front of them through remote-sensing infrared cameras," she said.

Long-distance flights would benefit the most from formation flying, she added. "If, say, you had several flights leaving from London, they would all join up over the Atlantic into a formation, and as they fly across the ocean, they would all benefit from the fuel savings," Oldham said.

"And then one could break off and fly to New York, another to Boston, and so on."

Published November 10, 2011

Mid-Air Refill

Photograph by Shane A. Cuomo, DOD/AP

A U.S. Air Force B-2 Spirit stealth bomber is refueled mid-flight by a KC-10 Extender aircraft over Australia in July 2006.

A common practice in the military, mid-air refueling has not spread to the commercial aviation industry yet, in part because of the vast infrastructure that would be required to support it. "There would need to be a global network of tankers" to serve as fuel stations for planes on overseas flights, Oldham said.

One argument for commercial mid-air refueling is that it would help make planes more energy-efficient, because they wouldn't have to take off with full tanks.

UBC's Gillen, however, is skeptical of this argument. "My view is that you're not necessarily saving any money, because the fuel is going to have to be brought up into the air somehow," he said. "You're either paying for it on the aircraft you're on, or you're paying for it on the fueling aircraft. So I think the net effect is zero, if not negative."

Even if the technical challenges could be overcome, it's not clear whether passengers would be comfortable with refueling during flight.

"We've seen it demonstrated in the defense and military markets for many years, but I think it's very different when you're in a [commercial] plane and you can see the refueling plane in front of you," Oldham said. "The technology is a reality, but are we ready for it psychologically?"

(Also see "Future Tech May Reduce Bird-Plane Collisions.")

Published November 10, 2011

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Photograph by Jorge Estévez García

Published November 10, 2011