Different Sound Barrier in Planes
Sound is made up of molecules of air that move. They push together and gather together to form sound waves . Sound waves travel at the speed of about 750 mph at sea level. When a plane travels the speed of sound the air waves gather together and compress the air in front of the plane to keep it from moving forward. This compression causes a shock wave to form in front of the plane.
In order to travel faster than the speed of sound the plane needs to be able to break through the shock wave. When the airplane moves through the waves, it is makes the sound waves spread out and this creates a loud noise or sonic boom. The sonic boom is caused by a sudden change in the air pressure. When the plane travels faster than sound it is traveling at supersonic speed. A plane traveling at the speed of sound is traveling at Mach 1or about 760 MPH. Mach 2 is twice the speed of sound.
Regimes of Flight
General Aviation(100-350 MPH).
Most of the early planes were only able to fly at this speed level. Early engines were not as powerful as they are today. However, this regime is still used today by smaller planes. Examples of this regime are the small crop dusters used by farmers for their fields, two and four seater passenger planes, and seaplanes that can land on water.
Supersonic (760-3500 MPH - Mach 1 - Mach 5).
760 MPH is the speed of sound. It is also called MACH 1. These planes can fly up to 5 times the speed of sound. Planes in this regime have specially designed high performance engines. They are also designed with lightweight materials to provide less drag. The Concorde is an example of this regime of flight.
Subsonic (350-750 MPH).
This category contains most of the commercial jets that are used today to move passengers and cargo. The speed is just below the speed of sound. Engines today are lighter and more powerful and can travel quickly with large loads of people or goods.
Hypersonic (3500-7000 MPH - Mach 5 to Mach 10).
Rockets travel at speeds 5 to 10 times the speed of sound as they go into orbit. An example of a hypersonic vehicle is the X-15, which is rocket powered. The space shuttle is also an example of this regime. New materials and very powerful engines were developed to handle this rate of speed.