When will we see hypersonic flight?

Imagine being able to go from New York to Los Angeles in half an hour, or from New York to Sydney in just four. That is the promise offered by hypersonic aircraft, which travel at least five times faster than the speed of sound (Mach 5). These speeds are made possible by the use of Scramjet technology, a 1950s concept where aircraft take in oxygen from the atmosphere to create combustion, thus heavy oxygen tanks are no longer needed on board.

Unfortunately, hypersonic flights are still “mostly wishful thinking”, according to Wayne Plucker of Frost & Sullivan. The g-force generated would not be easy to bear for most customers, and the technology is not fully ready yet. Hoping to speed up development, the US Air Force just partnered with DARPA to deliver a manned hypersonic aircraft by 2023.

Meanwhile, aircraft manufacturers are focusing on bringing back supersonic aircraft able to reach between one and two times the speed of sound (Mach 1-2). “We moved away from supersonic with the Concorde because it only made sense with a huge amount of taxpayers’ dollars,” says Richard Aboulafia of the Teal Group. “But with businesses, money isn’t the object, so supersonic may be useful in business jets.”

Among the supersonic aircraft being developed for commercial flights are the Aerion AS2, developed jointly by Airbus and Aerion, and Lockheed Martin’s N+2. The first will have a capacity of 10-11, while the N+2 would carry around 35 passengers. Airbus’s patent for a hypersonic commercial jet design was approved by the US patent office in July.

According to David Richwine of NASA, Airbus and Aerion want the AS2 to fly supersonic over water, but subsonic over land, to address problems with sound and air traffic control—a supersonic aircraft would have problems joining a queue for landing if it is flying at higher speeds. Lockheed Martin, by contrast, aims to fly supersonic over land.

NASA, which is working with all three companies in their supersonic endeavors, aims to help them by overcoming two important barriers to commercial supersonic flight: reducing the noise of the sonic boom to decrease noise pollution, and improving cruise efficiency to reduce fuel consumption and carbon emissions.

“The Concorde had a sonic boom that was 2 pounds per square foot of overpressure. We’re looking to design a sonic boom that’s 0.3 pounds per square foot, which would make them almost inaudible,” says Mr Richwine. NASA, which started its work on reducing sonic booms in 2001, has already managed small reductions by modifying the nose of supersonic jets, but more remains  to be done to achieve the 0.3 target.

As for fuel efficiency, NASA has been testing ways to reduce drag on wings. Because of the travel speeds of supersonic aircraft, the wings experience significant friction and turbulence in the air, both of which increase fuel consumption. To address this problem, NASA and Aerion have developed wings with very sharp edges and angles, resulting in a laminar flow that causes the air to move smoothly over the surface of the wing and thus reduce drag.

Beyond technical challenges, regulation may also be an issue. Aircraft regulations in the US, for example, are now much stricter than they were in the Concorde’s day. NASA says that although the supersonic technologies are close to being able to get a regulatory change, it could take at least six years.

Price should be less of an issue. Despite a price tag of $120m, the AS2 should be able to find buyers in the business community. “Subsonic flights will still be a large portion of the market as people want to fly for the cheapest rate,” says Mr Richwine. “Supersonic will be for people who want to pay for speed.”

This article is published in collaboration with GE Look Ahead. Publication does not imply endorsement of views by the World Economic Forum.

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Author: Mary-Ann Russon is a Technology Reporter with International Business Times UK.

Image: An EasyJet aircraft comes into landing during sunset at East Midlands airport, central England. REUTERS/Darren Staples