Engineering challenges of supersonic transport
Clinton Chan Cheuk Wang
Nowadays, supersonic aircrafts are mainly used for military purposes, such as fighter and bomber
aircrafts; it is uncommon to use supersonic aircraft for commercial flights. While supersonic flight can
greatly reduce the time of travel, it is important to explore the challenges and possibilities of applying
supersonic flight to civilian transportation. Supersonic aircrafts are aircrafts that fly faster than the
speed of sound (1236 km per hour), 1 and can reduce the time needed to travel from New York to London
3 hours. However, there are lots of challenges to supersonic flight, mainly in three areas: aerodynamics,
engines and noise.
Firstly, the flexibility of supersonic flight is restricted by aerodynamics to a large extent. The huge
resistive force due to the high speed has brought a lot of limitations to its application. The resistive force
experienced by an aircraft is greatly affected by the drag coefficient, which will spike when the Mach
number (ratio of aircraft speed to the speed of sound) of an aircraft reaches a specific value, resulting in
a dramatic increase in drag. While the value of drag coefficient peaks at Mach 1, supersonic aircrafts
which have a Mach number larger than 1 will suffer from a high drag force. The reason for this is the
formation of a shock wave. When supersonic aircrafts are moving at the speed of sound, the pressure
waves produced will overlap, forming shockwaves and additional drag called wave drag, resulting in
the drastic increase in drag. 2
To confront this problem, the first supersonic transport aircraft Tu-144 from the Soviet Union used
aluminium alloy VAD23 in order to reduce drag. At the same time, in order to produce enough thrust
to encounter the drag, engines with afterburner are used to achieve supersonic speed. 3 This has led to
another problem: engine efficiency. Compared to the subsonic aircraft mainly used in commercial
flights, supersonic aircraft require engines that provide a higher thrust. Engines with high efficiency,
such as turbofan engines, are not able to create sufficient thrust for supersonic flight. Apart from the
1 Glenn Research Centre. Speed of Sound. https://www.grc.nasa.gov/www/k-12/airplane/sound.html. 2 Glenn Research Centre. Factors that affect Drag. Motion of the Air. https://www.grc.nasa.gov/www/k-
12/airplane/factord.html.
3 Skybary. Afterburner Description https://skybrary.aero/articles/afterburner.
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