Shaped Sonic Boom Demonstration shock wave by a chase plane, the SSBD demonstrated a reduction in boom by about one-third. Several of the flights included NASA Dryden's F-15B research testbed aircraft following to measure the F-5E's shock wave signature close-up. During the flights, many shock wave patterns were measured by the F-15B at various distances and orientations from the F-5E. An unmodified F-5E flew a few seconds behind the demonstration aircraft to provide a baseline sonic boom measurement to validate the reduced boom produced by the demonstrator. A U.S. Air Force Test Pilot School Blanik L-23 glider carrying a microphone on the left wingtip,
Sonic boom other's way quickly enough. Eventually they merge into a single shock wave, which travels at the speed of sound, a critical speed known as "Mach 1", and is approximately at sea level and . In smooth flight, the shock wave starts at the nose of the aircraft and ends at the tail. Because the different radial directions around the aircraft's direction of travel are equivalent (given the "smooth flight" condition), the shock wave forms a "Mach cone", similar to a vapour cone, with the aircraft at its tip. The half-angle between direction of flight and the shock wave formula_1 is