The Return of Supersonic Passenger Aircraft

Imagine being able to have breakfast in London and lunch in New York just a few hours later. This idea has led to the revival of supersonic passenger jets after the failure of the Concorde project. Many individuals, such as businessmen and politicians, need to travel intercontinental distances in a short time, which is why several companies, including Boeing, have pursued the design of a new supersonic passenger aircraft in recent years. Most of these projects were abandoned due to reasons such as flight safety, high fuel consumption, lack of economic viability, excessive noise, and high aircraft costs. Finally, Aerion, in collaboration with Airbus, has managed to design a passenger aircraft capable of reaching speeds over one and a half times the speed of sound. Aerion hopes to conduct test flights by 2021 and publicly launch its jets in 2023. With this jet, named AS2, flight times between Europe and America will be reduced to about three hours and up to six hours for routes to Australia and East Asia. Typically, modern aircraft take about seven hours to cover the distance between New York and London, but with AS2 jets, passengers can arrive in four hours and 24 minutes. However, this aircraft has a capacity of about 12 passengers and costs around 100 million dollars, which is close to the price of a Boeing 737 that can carry over a hundred passengers. But how does this aircraft differ from Concorde, and why did Concorde fail? Concorde first flew in 1969 and was retired in 2003. It, along with the Tupolev 144, were the two supersonic passenger aircraft that were retired for various reasons. Concorde, a joint product of France and Britain, could fly at speeds of about twice the speed of sound. It utilized four turbojet engines with afterburners capable of supersonic flight, but these powerful engines had high fuel consumption. Concorde's wings were triangular in shape to overcome the severe airflow at supersonic speeds. After a crash in Paris in 2000 that resulted in the deaths of all on board, engineers identified a technical problem in the aircraft's engine design that was not economically feasible to fix, leading to its retirement in 2003. For over a decade after Concorde, various designs failed due to technical issues and high costs associated with designing supersonic aircraft. But why is designing a supersonic aircraft so costly and technically challenging? Simply put, compressible fluids like air become aware of the flow path through sound waves and adjust themselves accordingly. When speeds exceed the speed of sound, the aircraft encounters the air before it can adjust, creating shock waves known as sonic booms. Contrary to common misconceptions, breaking the sound barrier does not only occur when the aircraft exceeds the speed of sound; it creates pressure waves that produce explosive sounds while flying at supersonic speeds. Additionally, when speeds exceed the speed of sound, many fluid physics laws behave inversely. This necessitates different wing and body designs for supersonic aircraft compared to conventional planes, requiring stronger structures and better engineering due to shock wave formation, which also significantly increases fuel consumption. Currently, due to high noise production, most countries do not allow supersonic passenger aircraft to operate. Regulations in the United States prohibit supersonic flight. Concorde primarily operated in areas without sonic boom regulations, which is why most of its routes were over oceans. To address this issue, many aerospace companies are conducting various tests. For example, NASA has been testing a modified airframe that significantly reduces the explosive noise from sonic booms. Aerion has also stated that it has reduced the noise of supersonic aircraft through the design of the nose, fuselage, engine inlets, and wings. The wings of this aircraft are designed in a dual manner, with about 30% resembling conventional aircraft and 70% resembling fighter jets but with a new geometry. The sharp nose, mid-curvature, and elongated fuselage can also help in airflow separation and reducing sound waves. To achieve supersonic speeds, three engines are planned, but using three engines can increase fuel consumption. Another drawback of the aircraft is its need for long runways for landing, meaning it cannot land at every airport. Although this aircraft can only carry 12 passengers, its length is similar to that of aircraft designed to carry about 250 passengers. Regarding fuel consumption, engineers claim that through boundary layer methods and special fuselage design, high fuel consumption has been somewhat reduced. Aerion engineers have presented a design and construction model that was previously challenging for aircraft designers, creating a thin layer of air known as the boundary layer between the atmosphere and the aircraft body. When there is no turbulence in this layer and a smooth airflow is passing around it, fuel consumption decreases. However, if regulations are not amended, this aircraft can only fly at speeds exceeding 1.5 times the speed of sound over oceans, but must reduce its speed below the speed of sound over land.