The future of supersonic transport
as short as that of a conventional passenger aircraft, the actual fuel consumption might be lower, but the passenger capacity makes a huge difference – 100 passengers on a Concorde 30 versus 400 on a Boeing 747. 31 However, these data are nothing compared to a modern-day aircraft. An Airbus 350-1000 consumes only 6,300 Litres of fuel per hour. 32 Therefore, for future SST to be sustainable, manufacturers will need to come up with solutions to lower fuel consumption to meet up with modern- day standards.
When supersonic jets are cruising at such high speed, drag is a huge concern. Wave drag is caused by the formation of shock waves, and since waves radiate energy, this disrupts the airflow around the aerofoil. 33 Supersonic flights experience a significantly larger amount of wave drag than subsonic flights (Mach 0.7- 0.8, speed of conventional passenger aircraft). When designing the aircraft, there are a few ways to lower the coefficient of drag ( 𝐶 𝐷 ). 𝐶 𝐷 is especially important as the drag force increases
Figure 3: A diagram depicting the wave drag caused by shock wave
with the square of velocity, as given by 𝐹 𝐷 = 𝜌𝑣 2 𝐶 𝐷 𝐴 , 34 where 𝐹 𝐷 is the drag force, 𝜌 is the density of the medium, 𝑣 2 is velocity squared, and 𝐴 is the cross- sectional area. The first solution is, to avoid sudden changes in the cross- sectional area. 35 According to the 1 2
Whitcomb Area Rule, ‘ to avoid the formation of strong shock waves, the total area distribution must be smooth ’ . 36 Therefore, the ideal design would be a narrow and slender fuselage, with less sharp edges and ensuring that the total area of the fuselage does not change much. We can see this clearly from both the X-59 and Overture Figure 4: Diagram and a 𝐶 𝐷 against Mach number graph for visualizing the Whitcomb Area Rule
30 ‘ Celebrating Concorde, ’ British Airways, accessed August 23, 2022, https://www.britishairways.com/en- gb/information/about-ba/history-and-heritage/celebrating-concorde.
31 2007 Schools Wikipedia Selection, Wikipedia , s.v. ‘ Boeing 747, ’ last modified 2007, https://www.cs.mcgill.ca/~rwest/wikispeedia/wpcd/wp/b/Boeing_747.htm.
32 Danny Lee: quarantined again (@AirEVthingTRNSP), ‘ One reflection on my @British_Airways LHR-YYZ A350- 1000 flight recently was the fuel saving (we knew it was super-efficient already), ’ Twitter, December 4, 2019, 3.24 a.m., https://twitter.com/AirEVthingTRNSP/status/1202066015892336641/photo/1. 33 ‘ Wave Drag, ’ ChemEurope.com, accessed August 23, 2022, https://www.chemeurope.com/en/encyclopedia/Wave_drag.html. 34 ‘ The Drag Equation, ’ NASA Glenn Research Centre, accessed August 23, 2022, https://www.grc.nasa.gov/www/k-12/airplane/drageq.html. 35 Real Engineering, ‘ Boom: The Future of Supersonic Flight?, ’ May 15, 2017, video, 10:54, https://www.youtube.com/watch?v=R43gKMWAPco. 36 ‘ Area Rule, ’ SKYbrary, accessed August 23, 2022, https://skybrary.aero/articles/area-rule.
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