Supersonic aircraft

Supersonic aircraft are planes capable of traveling faster than the speed of sound. This threshold is known as Mach 1. When an object moves faster than sound, it creates shock waves. These waves result in a loud noise called a sonic boom.

Engineers study the aerodynamics of this flight as compressible flow. This is because the air is squeezed or compressed by the shock waves. If an aircraft reaches speeds above Mach 5, it is classified as a hypersonic aircraft.

Designing these aircraft is a massive technical challenge. As a plane enters the transonic regime, which is roughly Mach 0.85 to Mach 1.2, aerodynamic drag rises sharply. This is often called wave drag. To fight this, engineers use the Whitcomb area rule to minimize sudden changes in the plane's size. A successful design often looks long and slender. This shape is similar to a Sears-Haack body or a von Karman ogive. Such shapes help the aircraft slice through the air more efficiently.

Wing design must also balance different needs. Wings used for supersonic flight often have a limited wingspan to reduce drag. However, short wings are not efficient for slow speeds like takeoff or landing. One solution is the variable-geometry wing, or "swing-wing." These wings spread wide for low speeds and sweep backward for high speeds. Another common design is the delta wing, which is a large triangle shape. The Concorde used delta wings to create a vortex. This vortex helps keep air flowing smoothly over the wing at high speeds.

Heat is a major obstacle for sustained high-speed flight. Friction from air flowing over the plane and the compression of air both create intense heat. Most planes use aluminum alloys like Duralumin. However, Duralumin loses its strength at high temperatures. This limits most aluminum planes to speeds below Mach 2.2. To fly faster, engineers must use materials like titanium or stainless steel. The Lockheed SR-71 Blackbird used titanium to cruise at Mach 3.1. At that speed, parts of the aircraft could exceed 315 °C.

Engines must also be specially designed to provide enough thrust. Early supersonic planes used rocket power, but rockets burn fuel very quickly. Later, engineers developed the afterburner. This device burns extra fuel directly in the jet exhaust to increase power. Modern supersonic aircraft often use low-bypass turbofans with afterburners. These engines are efficient both above and below the speed of sound. Some planes, like the SR-71, used Pratt & Whitney J58 engines. These engines could act as turbojets during takeoff and then bypass air to the afterburner at high speeds.

History shows the rapid progress of supersonic technology. The first aircraft to achieve supersonic speed was the American Bell X-1. It was a research rocket plane powered by liquid oxygen and ethyl alcohol. On October 14, 1947, pilot Chuck Yeager performed the first recognized controlled level flight above Mach 1.

Later, Jacqueline Cochran broke the sound barrier as a female pilot in an F-86 Canadair Sabre. In 1961, a Douglas DC-8-43 also achieved supersonic speed during a controlled dive. These milestones proved that humans could master high-speed flight.

While most supersonic flight is military or experimental, some reached civilian service. Only two supersonic passenger airliners have ever been used commercially. The Soviet Tupolev Tu-144 first flew on December 31, 1968. The Anglo-French Concorde first flew on March 2, 1969.

These planes were incredible feats of engineering. However, they faced many obstacles. Political, economic, and environmental issues prevented them from reaching their full potential. Despite this, they remain famous examples of how fast humans can travel.