Supersonic flight is one of the four speeds of flight. They are called the regimes of flight. The regimes of flight are subsonic, transonic, supersonic and hypersonic.
Vehicles that fly at supersonic speeds are flying faster than the speed of sound. The speed of sound is about 768 miles per hour (1,236 kilometers per hour) at sea level. These speeds are referred to by Mach numbers. The Mach number is the ratio of the speed of the aircraft to the speed of sound. Flight that is faster than Mach 1 is supersonic. Supersonic includes speeds up to five times faster than the speed of sound, or Mach 5.
In 1947, Air Force Capt. Charles E. "Chuck" Yeager became the first person to fly an aircraft faster than the speed of sound.
What Flies at Supersonic Speeds?
A bullet fired from a gun is an example of an object that flies at supersonic speeds. Military fighter aircraft also fly this fast. The space shuttle orbiter flies at supersonic speeds during portions of its mission.
An airplane called the Concorde was the most notable passenger airplane to travel at supersonic speeds. The Concorde's maximum speed was more than twice the speed of sound. It could fly people from London to New York in less than 3 1/2 hours. That is about half the amount of time it would take typical airliners to fly the same distance. The Concorde is no longer in use. It flew for the last time in 2003.
What Is a Sonic Boom?
A sonic boom is a loud, thunder-like noise heard by a person on the ground when an aircraft flies overhead at supersonic speeds. Air reacts like a fluid to supersonic objects. As objects travel through the air, the air molecules are pushed aside with great force. This force forms a shock wave, much like the wave created by the front, or bow, of a boat moving in water.
The shock wave forms a cone of pressurized air. A sharp release of pressure after the buildup of a shock wave is heard as a sonic boom. It is similar to the sharp release of pressure when a pin pops a balloon and makes a loud noise.
NASA is studying and testing devices that could be used on aircraft to lessen the noise and window-rattling effects of supersonic flight.
Why Does NASA Study Supersonic Flight?
NASA studies supersonic flight as part of its aeronautics research. Aeronautics is the study of the science of flight. NASA studies flight in support of the nation's air transportation system and the development of future air and space vehicles.
Learning more about supersonic flight helps NASA design aircraft to perform better at supersonic speeds. It can also help in the design of new vehicles used to explore space. Space vehicles fly at supersonic speeds too.
Rockets like the space shuttle fly at supersonic speeds after liftoff. From about 45 seconds after launch until about two minutes after launch, the shuttle accelerates from Mach 1 to Mach 5.
Launch vehicles fly at hypersonic speeds - greater than Mach 5 - while in Earth's upper atmosphere. During atmospheric re-entry, spacecraft slow to supersonic speeds. The space shuttle is flying at supersonic speeds when it reaches the lower part of Earth's atmosphere as it approaches for landing.
How Does NASA Study Supersonic Flight?
NASA studies supersonic flight in three ways.
NASA researchers can simulate supersonic flight by using small models of aircraft in wind tunnel experiments. Wind tunnels are tube-shaped facilities that move air over a vehicle as if it were flying. They help researchers to learn more about how an aircraft will fly and to test new designs.
Researchers also fly actual supersonic aircraft that have been modified for research experiments. NASA has been involved in supersonic flight experiments since the 1940s. NASA partners with the U.S. Air Force or U.S. Navy and aircraft manufacturers to build experimental aircraft. These aircraft are called X-planes because the aircraft are used for experiments. The "X" in X-planes comes from the letter "x" in the word "experiments." X-planes test new designs and new technologies to improve flight.
In 1947 the first X-plane, called X-1, was the first aircraft to break the sound barrier. Nine years later, in 1956, the X-2 became the first aircraft to reach Mach 3, or three times the speed of sound. Aircraft such as the XB-70 (also called the Valkyrie) and the X-29 tested new wing designs. Other experimental aircraft tested new materials that could be used to make faster airplanes.
A third way NASA learns about supersonic flight is through computer simulations. The computerized simulations are commonly referred to as computational fluid dynamics, or CFD.[image-110]
Words to Know (based on Earth's atmospheric conditions):
Subsonic flight: Less than Mach 1. This is the speed traveled by most of the commercial airplanes that carry people and cargo.
Transonic flight: At or about Mach 1.
Hypersonic flight: Greater than Mach 5. This is more than five times the speed of sound. It is the speed traveled by rockets and the space shuttle as they go into orbit.
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Heather R. Smith/NASA Educational Technology Services