The second possible cause is changes to aircraft stability, which can over stress the aircraft to the point of failure. Flutter can occur almost instantaneously once a certain critical speed is reached, and in a split second the vibrations on the aircraft will exceed the strength of the aircraft - and the structure will catastrophically fail. Flutter is very sensitive to speed, and can be further exaggerated by the effects of shock waves forming on the wings and control surfaces. Flutter is an unstable coupling of the aerodynamics of the aircraft and the natural vibration modes of the aircraft structure. There are two other failure modes that likely caused the destruction of aircraft trying to break the sound barrier in this timeframe. Increase in drag itself is not likely the cause of the structural failures, as drag forces on an aircraft typically do not critically affect the structure. Further, there was skepticism that aircraft propulsion systems could ever propel an aircraft to the speed regimes in the same way that a projectile achieves this speed by being shot from a gun.ĭid drag cause structural failures in WWII aircraft when approaching the speed of sound? While bullets and cannonballs had exceeded the speed of sound for years, conventional wisdom held that humans could not exceed it. At the time, no aircraft had successfully overcome this drag rise, so some predicted that it might not be possible.ĭid anything else break the sound barrier prior to 1947? This shock formation and increase in drag is very sudden and large, and tends to be a “barrier” to any further acceleration of the aircraft. Both of these phenomena can create significant aircraft drag. These shock waves cause pressure fields on the wing (and the rest of the aircraft) and can lead to significant flow separation behind the shock waves. This increase comes from shockwaves forming in the accelerated flow over a wing, even though the aircraft itself is not yet exceeding the speed of sound. Aircraft that are not specifically designed to fly supersonically - those having little or no wing sweep and that have thick wings with blunt leading edges - exhibit a sharp rise in aircraft drag as they approach the speed of sound. In the 1940s, the proper design techniques and aerodynamic details for a successful supersonic aircraft were unknown. It was described as hitting an invisible wall. Why did people believe the sound barrier was a physical wall?ĭuring World War II, pilots reported aircraft tearing apart and instruments freezing when they dove during combat - possibly at the moment they approached the speed of sound. It’s approximately 770 mph or 1,239 kmh at sea level. The speed at which you break the sound barrier depends on many conditions, including weather and altitude. The moment an aircraft’s speed exceeds the speed of sound, it is said to have broken the sound barrier.Īt what speed do you break the sound barrier?
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