The future of supersonic transport
American Airline’s Chief Financial Officer . 12 However, before these supersonic jets take flight, it is necessary to solve two of the biggest problems faced by SST, namely, a) the physical phenomenon of ‘sonic boom’, an impulsive noise similar to thunder, a shockwave caused by objects moving faster th an the speed of sound; 13 b) the immense drag due to high-speed flying, and the fact that supersonic aircraft engines are not fuel efficient, especially when the world is tackling climate change and energy crisis.
Sonic boom
Sonic Boom occurs when objects are moving at a speed faster than the speed of sound. When an aircraft cuts through the air, there are always waves propagating away from the point of impact, i.e. the nose of the aircraft. 14 However, when the aircraft is flying supersonically, and the waves are not fast enough to
Figure 1: Boom's Flagship Aircraft – Overture
‘move out of the way’, it produces wake, 15 and a sonic boom is a form of wake. In other
Figure 1: Comparison of Wave Diagram under Different Conditions
words, a sonic boom is a single shock wave formed by many small pressure waves, and it creates a quick expansion and contraction of air when it reaches the ground, 16 creating sounds as loud as thunder, around 110 decibels, 17 affecting areas within 30 miles. 18 Most of the countries in the world have banned supersonic flights on land, after claims of damaged properties, animals dying or ‘gone insane’ were made. 19 This was why the Concorde was limited to trans-oceanic flights.
Figure 2: A pressure-time graph of a sonic boom caused by an SR-71 supersonic flight
For this ban to be lifted, it is evident that the industry will need to come up with a solution to minimize the effect of a sonic boom. NASA and Lockheed Martin
12 Boom, ‘ American Airlines Announces Agreement to Purchase Boom Supersonic Overture Aircraft, Places Deposit on 20 Overtures, ’ Boom , August 16, 2022, https://boomsupersonic.com/news/post/american-airlines- announces-agreement-to-purchase-boom-supersonic-overture-aircraft-places-deposit-on-20-overtures. 13 ‘ Sonic Boom, ’ Air Force, accessed August 21, 2022, https://www.af.mil/About-Us/Fact- Sheets/Display/Article/104540/sonic-boom/. 14 ‘ What Causes a Sonic Boom?, ’ HowStuffWorks.com, accessed August 22, 2022, https://science.howstuffworks.com/question73.htm. 15 Ibid. 16 ‘ Why Are Sonic Booms So Loud?, ’ BoldMethod, accessed August 22, 2022, https://www.boldmethod.com/blog/2013/11/why-are-sonic-booms-so-loud/. 17 ‘ Taming the BOOM, ’ NASA, accessed August 22, 2022, https://www.nasa.gov/feature/glenn/2022/taming- the-boom. 18 ‘ Quick and Quiet: Supersonic Flight Promises to Hush the Sonic Boom, ’ Lockheed Martin, accessed August 22, 2022, https://www.lockheedmartin.com/en-us/news/features/2016/webt-supersonic-flight-hush-sonic- boom.html. 19 Matthew Hutson, ‘ Will we ever Fly Supersonically Over Land?, ’ New Yorker , June 25, 2021, https://www.newyorker.com/tech/annals-of-technology/will-we-ever-fly-supersonically-over-land.
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