This report analyses and discusses the discovery of high-speed manned flight and ‘Mach’ - in particular research and aviation breakthroughs relating to the specified topics.
High-speed speed flight is technically defined as ‘flight near, but below the speed of sound’ [1A]. This begins at an airspeed of around 250 mph, or 400 kph. Properties regarding the airflow around an object at low speed or below this threshold of 400 kph are relatively straightforward, and can be compared to that of an aircraft moving through a body of water. This is due to the negligible change in air density at these speeds, and conducting calculations without factoring in the compression yield remain accurate.
However as the speed surpasses 400kph, some of the energy from the aircraft is used to compress the air in front - increasing the air density in a local area around the object[2A]. This is known as “compressibility”, and is a key factor in high speed flight. The pilot of an aircraft such as a Cessna with a top speed of 302 kph can ignore compressibility altogether, however faster aircraft must be able to factor this in.
Ernst Mach and Christian Doppler, are among the main contributors regarding research and theoretical work towards the current understanding of supersonic flight. In 1842 Christian Doppler proposed the widely known “Doppler Effect”. He theorised that if the source of a sound that is emitted is moving towards the observer, the frequency of the sound will increase due the sound waves emitted being closer together in the medium they travel through - in Earth’s most common scenario air. For the source travelling away from the observer, the inverse is true. This can be directly related to the effect of compression that air undergoes in front of an aerofoil moving at high speed.
In 1887 Ernst Mach, an Austrian physicist and philosopher published a photograph depicting the shockwave of a supersonic projectile using schlieren type photography. The photograph provided the first visible evidence of a shock wave and supported theories and research associated with the behaviour of compression shockwaves and the doppler effect.
More than three decades later on the 4th May, 1929, a Swiss aeronautical Engineer named Jacob Ackeret conducted his first lecture at Zurich’s Federal Institute of Technology. In the lecture, he noted that “it would be very convenient to have a special name for the important ratio of flow speed (or flight speed) to sound speed. He proposed the designation ‘Mach Number’” and credited Mach for his studies and research. To this day, the term ‘Mach’ used to name the ratio of speed to the speed of sound is used globally.
The first published and official data that displayed the adverse compressibility effects of high-speed flow over an aerofoil was collected by Frank Cadwell and Elisha Fales in 1920. While working for the National Advisory Committee for Aeronautics (now NASA), Cadwell and Fales constructed America’s first high-speed wind...