On a gusty March day in 1969, the future of air travel was revealed.
A spontaneous burst of applause could just be heard over the deafening roar of the plane’s four giant engines as they sped the sleek aircraft into the sky. Twenty seven minutes later the screech of wheels and a whoosh of a parachute, signaled the end of the maiden voyage of Concorde, one of only two supersonic passenger planes to ever fly.
When the slender, beak-nosed aircraft entered service seven years later they whisked champagne-sipping passengers across the Atlantic in just three and a half hours. The twenty craft went on to fly routes for another 27 years to South America, Malaysia and beyond, proving a hi-tech vision of glamorous, fast-living. But it all came to an end in 2003, when the fleet was retired over concerns about high operation costs, limited demand for the expensive tickets and the jets’ safety, following a deadly crash three years earlier.
But supersonic, commercial air travel still holds an allure for passengers, pilots and engineers alike. And now, with the help of modern materials and advanced computer simulations, aerospace researchers hope they will be able to overcome some of the issues that Concorde faced, providing a blueprint for the next generation of supersonic planes.
Big bang theory
Two of the main problems facing any supersonic aircraft are increased drag, meaning increased fuel consumption, and that famous “sonic boom”, a loud gunshot-like noise that disturbed anyone unfortunate to be under the flight path.
The blast, which occurs when the plane breaks the sound barrier, is why Concorde was limited to routes over the ocean. You could travel from London or Paris to New York at high speeds, but there was no onward connection to Los Angeles. And several other countries were forced to ban the plane from its airports or even airspace, for the disturbance it caused.
“Although the aircraft is moving faster than the speed of sound, it generates pressure waves that only move AT the speed of sound” explains Professor Karthik Duraisamy, from Stanford University, an expert in modeling this type fluid flow.
“The pressure waves start bunching up together, and create a so-called shockwave. If you’re standing on the ground and the plane flies above you, the wave passes over you. That’s the sonic boom.”
Big names in the aviation industry are trying to find solutions, including Boeing, Lockheed Martin, and Nasa. The space agency recently conducted wind tunnel tests of designs from both manufacturers that showed the showed the boom could be reduced to levels that are generally thought to be acceptable for routine overland flights. But an engineer at MIT, believes that a radical idea from the 1950s may hold the key to ‘boomless’, fuel-efficient craft.
Professor Qiqi Wang is part of a team that has shown that a bi-plane – essentially two, stacked wings - could bring huge improvements over the traditional delta-wing seen on Concorde. The idea was first proposed by German engineer Adolf Busemann, an influential aerospace designer who among other things first proposed the use of ceramic tiles to protect the Space Shuttle on reentry. According to theory, the Busemann bi-plane, when travelling at supersonic speeds, should produce less drag meaning it should use less fuel. Plus, the triangular wings can be “tuned” so that sonic boom is almost entirely eliminated.
“When we have two wings, if we place them in a carefully designed manner, the shockwaves from the two wings can cancel each other” says Prof. Wang.