How Things Work: The Concorde aircraft
The commercial airliner Concorde, commissioned in 1976, once traversed the Atlantic in a little less than three and a half hours. The result of British Airways and Air France collaboration, the supersonic plane demonstrated how small we could make the world. Achieving supersonic flight not only demanded engineering and design creativity, but also introduced a great deal of risk as well. How did the Concorde fly faster than the speed of sound, and why couldn't it last?
The jet engines that thrust the plane forward were the twin Rolls-Royce/Snecma Olympus 593s. Producing up to 142 kN, the titanium engines were designed to withstand high temperatures and pressure. It worked by taking in air at high speed and pressure, then compressing it through seven stages. The compressed air was then mixed with jet fuel and ignited. The ignition was released from the engine nozzles, creating forward thrust. The engine pushed the Concorde from takeoff speeds of 200 mph to Mach 2.04 speeds, more than twice the speed of sound (Mach 1) and almost 1,400 mph.
The Concorde’s ability to achieve supersonic speed was partially thanks to the design of its body. The aircraft sat a hundred passengers and was not as spacious as usual 100-seater planes. This is because the plane’s cabin had a small circumference, which mathematical models determined was optimal for such speeds. The wings of the plane resembled those of the Space Shuttle, yet were curved along their perimeter to reduce drag forces and generate more uplift. The plane’s long, sharp nose was a disadvantage for pilots when taking off, as it blocked their view. This was fixed by enabling the nose to adjust mechanically, referred to as a droop nose.
Supersonic speed came with many problems. The plane’s surface created so much friction with the fast-moving air molecules that passengers admitted to feeling heat on the window panes. Drag forces at such high speeds created incredible stresses and strains on the body of the aircraft, causing it to bend up to two meters during banking. Engineers solved this issue by adjusting the center of mass of the plane through the redistributing of fuel in the wings and tail.
The supersonic jet had to fly at high altitudes where the atmosphere is much less dense. At 60,000 feet, or 11 miles into the air, the plane experienced much less drag force. Passengers noted that they could see the curvature of the Earth from such a height. In comparison, subsonic commercial planes fly below 30,000 feet. An extremely disastrous consequence of the Concorde’s high altitude was the damage its exhaust had on the ozone layer.
Another issue the Concorde had to deal with was its sonic boom, the sound associated with the shock waves left behind an object traveling faster than the speed of sound. It is caused when the sound waves, which travel at Mach 1, that are emitted at the front of a supersonic object merge into one super shock wave; it is as though the waves cannot move from the object’s path quickly enough. It resembles a loud crack, capable of shattering windows below. Therefore, the airliner was not allowed to reach supersonic speeds until it was above ocean.
The Concorde is a reminder of many things. It demonstrated how engineering, and especially international collaboration in engineering, can produce cutting-edge technology. It also proved to us that the world can be made even smaller, and travel more time-effective. Yet, it reminded us that no matter how much a product pushes the envelope, it will not last if it does not have a good business model. Running a supersonic commercial jet was unimaginably costly, with many faulty parts and expensive tickets. A fatal crash of the Concorde in 2000 also withdrew public support for the plane.
Today, planes fly well below the speed of sound and, to many, it seems a downgrade. Until a supersonic jet is designed that addresses the engineering and business issues the Concorde faced, we will live in the aviation stone age, spending six hours in transit from New York to London.