Quiet Supersonic Commercial Aircraft; A Transformation in Air Transportation?

Several companies are currently seeking to commercialize supersonic aircraft again. One of the biggest challenges in this endeavor is the high and non-standard noise produced by such aircraft. To address this issue, NASA, in collaboration with Lockheed Martin, aims to introduce a quiet supersonic aircraft by 2021, named QueSST. If NASA succeeds in developing such an aircraft, air transportation worldwide could undergo a significant transformation. Due to high noise production, most countries do not allow supersonic passenger aircraft to operate. The Concorde, as a supersonic passenger aircraft, faced various challenges during its operational period. The Concorde first flew in 1969 and was retired in 2003. Along with the Tupolev 144, they were the two supersonic passenger aircraft that were retired for various reasons. The Concorde, a joint product of France and the UK, could fly at speeds of about twice the speed of sound. It utilized four afterburning turbojet engines, which allowed it to fly at supersonic speeds but had high fuel consumption. The wings of the Concorde were triangular in shape to overcome severe airflow at supersonic speeds. Following a crash in Paris in 2000 that resulted in the deaths of all onboard, engineers discovered a technical issue in the aircraft's engine design that was not economically feasible to rectify, leading to its retirement in 2003. Regulations in the U.S. prohibit flying at supersonic speeds. The Concorde operated in areas where such regulations did not exist, which is why most of its flight paths were over oceans. To solve this problem, many aerospace companies are conducting various tests. NASA has signed a $247 million contract with Lockheed Martin to develop such an aircraft, with plans for it to fly by 2025. The goal of this program is to create a supersonic aircraft that does not disturb residents in the areas it flies over; therefore, specific designs must be implemented in the aircraft's structure. By designing the nose, fuselage, engine inlets, and wings, the high noise levels of supersonic aircraft can be reduced. A pointed nose, a streamlined fuselage, and specific wing shapes can effectively reduce shock waves. But why is designing a supersonic aircraft so costly and technically challenging? Simply put, compressible fluids like air become aware of the sound waves in their flow path and adjust accordingly. When speeds exceed the speed of sound, the aircraft collides with the air before it can adjust, creating shock waves, commonly known as breaking the sound barrier. Contrary to popular belief, breaking the sound barrier does not only occur when an aircraft exceeds the speed of sound; it generates pressure waves that create an explosion-like sound while flying at supersonic speeds. Additionally, when speeds exceed the speed of sound, many fluid dynamics principles behave oppositely. Due to these conditions, the design of wings and fuselages in supersonic aircraft differs from conventional aircraft. The formation of shock waves at supersonic speeds necessitates stronger structures and better engineering, which also significantly increases fuel consumption. For the new aircraft, dimensions of 28 meters in length and 9 meters in width are planned, and it will use an engine similar to that of the F-18 fighter jet. The maximum speed for this aircraft is set at Mach 1.5. According to the planned schedule, the design of this aircraft will be completed by 2021, with various ground tests scheduled for 2022, and if everything goes successfully, the aircraft will conduct its first test flight in 2025.