When an object moves through the air, it vibrates the air molecules. This vibration is so weak for slow-moving objects, that the strength of the airwave is below the human audible limit. That is why we hear a swooshing sound when something moves fast. But when the speed of the object is more than the speed of the sound itself, things get loud fast.
The speed of sound is 343.2 m/s or 767.26 mph. Speed faster than this is called a supersonic. When an object moves at supersonic speed, the air reacts like a fluid to that object. As that object moves, the air around it is suddenly pushed or expanded at a great force. Then instantly contracted to fill the gap created by the expansion. It creates a shockwave. In the case of a supersonic aircraft, this shockwave travels to the ground and creates a thunder-like loud sound — a sonic boom.
Supersonic flights without the boom
Sonic booms are very loud and can be an uncomfortable nuisance for people. It can also cause damage to structures. In extreme cases, a sonic boom can cause harm to wildlife as it can disorient or even kill birds or other sound-sensitive animals. In 1966, a boom from a supersonic aircraft dislodged tons of rock. These rocks crushed the archaeological sites in the Canyon de Chelly National Monument.
Scientists have been working on a boom-free supersonic flight to prevent the bad effects of a sonic boom. It is still a new technology and there aren’t many examples of it. NASA has been working on this technology for a few years now. This technology works mainly by changing the design of aircraft so that they cause minimum shock waves in the air via sock-absorbent materials.
NASA is currently focusing on developing new technology and materials that can bring the shock waves of a supersonic flight to a minimal level. They conducted a few unmanned test flights to refine this technology. The X-59 is NASA’s current prototype of boom-free supersonic aircraft. It is built with Lockheed Martin for the Quesst mission to create a boom-free supersonic aircraft. The aircraft can reach up to 1.4 Mach and creates sounds of 75 PLdB, which is, according to the aerospace company, the sound of a car door closing. Boom-free supersonic flight can result in faster travel with no noise pollution. Also, NASA is working to make this technology fuel efficient by reducing drag as well.
YouTube: Tail Installed on NASA’s X-59
Photo credit: The feature image and second image within the body of the article have been provided by NASA for press usage. The first image within the body of the article has been taken by Defence-Imagery from Pixabay.
Sources: National Park Service / NASA / Lockheed Martin