March 20, 2023
March 6, 2023
February 20, 2023
February 6, 2023
Throughout history, exceptional people have sought to break with conventional barriers. Prior to May 6, 1954, conventional wisdom said that a human could not run a mile in less than four minutes—Roger Bannister proved on that day the fallacy of this notion and since that day, many have conquered the mile in less than three-minutes. In similar fashion, the speed of sound was treated to the same conventional wisdom until Chuck Yeager made his famous jet flight.
Just like the 4 minute mile, traveling at the speed of sound was thought to be impossible to achieve by human kind. The problem that became the ‘stumbling block’ of this kinetic energy of 760 miles per hour at sea level (Sound travels at different speeds at different altitudes and at different temperatures or air density) were the questions of what happens next. The engineers, physics experts, and scientists were uncertain of the consequences that would envelope objects moving or approaching the incredible speed of sound. The trusted laws of aerodynamics suddenly seemed to go ‘out of whack’ when they were met with the sound barrier.
The first plane that was built to sustain controlled flight in 1909 was chugging along at 42mph and within 60 years, planes were moving at speeds of 1500mph easily. Taking the gigantic leap within this short period of time, it was no wonder that these exceptionally minded individuals were perplexed. The tests on planes approaching the speed of sound revealed planes losing control, severe vibrations, tendencies to nose over; thus the term was coined ‘the sound barrier’ to consolidate the problems they faced into one seemingly accurate phrase. To flight engineers, it seemed as if there was an invisible wall or force field in the sky that restricted objects moving at this speed. Countless fatal accidents transpired during this period. The pilots that that took part in these extreme experiments signed on dotted lines that stripped them of any rights, should anything go awry.
To break this wall and penetrate the ‘force field’ of sound aircraft engineers ventured deeper into the woods to study and understand the physics of sound and the unexplored realms of aerodynamics. They soon realized that they were looking at the problem through a keyhole instead of breaking the door down. Aerodynamics was not the only problem. The problem was ‘all of the above’ including the fact that any plane that is flying through air displaces the air that it is flying through, creating pressure waves that radiate from various points on the plane’s surface like ripples that are formed by a boat moving through water. At subsonic speeds these waves dissipate harmlessly out, ahead of the plane, but at sonic speeds the situation changes drastically.
The waves are not able to move ahead for the aircraft is actually moving at the same speed as the waves. What starts happening at this point is that these waves start “piling up,” reinforcing one on top of the other, rapidly creating a high pressure shock wave. The first of these shock waves are always formed on a plane’s wings as the curve of the wings causes air to travel faster and as such, the wings of a plane approach sonic speed before any other segment of an aircraft. This realization cleared ‘the air.’
Since the primary shockwaves were formed on the wings, the problem therefore was clearly in the design of the wings. Eventually the designers became aware that the shockwaves could not be avoided, but they could minimize it via 3 methods. The first was by making the wings thinner with sharper leading edges; the second was by making the wings shorter and wider; and the third involved sweeping the wings backward in a ‘V’ shape to allow air to pass over the wings at an angle which lessens the ‘speedup’ of the airflow.
The sound barrier was finally conquered when the designers threw another 3 final factors into the mix, which were basically strength, lightness, and heat resistance. The final frontier was stability at supersonic speeds which were managed efficiently with more sensitive and powerful control systems that enabled the pilot to have more control over the craft than the external factors that barrage the plane as it travels faster than we could ‘listen’.
As I continue to explore the history of flight through this blog, I must take my hat off to all the pioneers such as Chuck Yeager who officially “broke” the sound barrier, Harold Comstock and Roger Dyer who laid claim to that feat in 1942, and Hans Guido Mutke in 1945. Regardless of who actually broke the barrier first, all were men of extraordinary courage who deserve our gratitude. The lessons learned in the aviation industry by the engineers who designed and the brave men who flew the aircraft in the tests have led us to where we are today. Because of their efforts, whether we are chartering a private business hopper along the coast from San Francisco to Los Angeles or booking a private jumbo airliner for our conference to Las Vegas, we can do so swiftly and safely.