Do you know what the speed of sound is? The distance travelled by a sound wave as it propagates through an elastic medium per unit of time is the speed of sound and it varies considerably in the Earth’s atmosphere. While the speed of sound in dry air at 20 °C is 343 m/s, this number can vary anywhere between 295 and 355.
When an object approaches the speed of sound, also known as Mach 1, it experiences a sudden increase in aerodynamic drag. This is referred to as the sound barrier or sonic barrier, though there is no physical or solid barrier involved. When an aircraft’s speed goes past that of the speed of sound, it is then said to have broken the sound barrier.
Yeager was the first
The first person to break the sound barrier was U.S. Air Force Captain Chuck Yeager. Not long after Yeager became the first person to break the sound barrier in October 1947, Herbert H. Hoover joined him on March 10, 1948. Hoover was not only the second person to achieve the feat, but also the first civilian to break the sound barrier.
Born in Knoxville, Tennessee, U.S. on May 18, 1912, Hoover lived in the Homberg area and earned a degree in Mechanical Engineering, graduating from the University of Tennessee in 1934. After serving in the Army briefly after college, Hoover took a job as a pilot with Standard Oil in South America in 1937. He spent the next three odd years flying hospital patients, staff, and equipment between camps in Venezuela, sharpening his flying skills, even in bad weather.
Fearless flyer
By the time Hoover accepted a position with the National Advisory Committee for Aeronautics (NACA) in Hampton, Virginia, U.S. in 1940, he already had plenty of flying time under his name. In the years that followed, he built himself a solid reputation as he went on to become a chief test pilot with NACA.
He did this by fearlessly volunteering himself for experimental test flights. On more than one occasion, Hoover proved to be a cool pilot in tight situations, overcoming tremendous adversity to safely perform emergency landings.
Transonic flight research
It was in 1947 that Hoover joined the U.S. Air Force-NACA joint transonic (speeds close to that of sound) flight research program at the Muroc Flight Test Unit in California, now known as the Neil A. Armstrong Flight Research Center. Yeager served as the lead pilot for the Air Force and Hoover for the NACA for the program, which used the XS-1 rocket engine powered aircraft built by Bell Aircraft.
More popularly referred to as the Bell X-1, the aircraft was dropped from a B-29 carrier aircraft during flight. The X-1 would then light up its rocket engines and accelerate to transonic speeds, before eventually reaching supersonic levels.
Achieves Mach 1.065
Less than five months after Yeager had made his mark, Hoover got his chance. During his 11th flight on March 10, 1948, Hoover powered his Bell X-1 to reach Mach 1.065, approximately 365 m/s. With that, Hoover made it to the history books as the first civilian to break the sound barrier.
Herb Hoover in his jumpsuit, ready to pilot an aircraft in December 1948. | Photo Credit: WIKIMEDIA COMMONS
Before moving on to other programs, Hoover made four more flights on the XS-1. As a pilot with NACA, he flew more than 100 different aircraft. He ultimately lost his life during one such flight.
While piloting a B-45A Tornado Jet Bomber on August 14, 1952, Hoover and his copilot had to parachute from an exploding aircraft. While it was initially believed that both survived the crash, Hoover’s body was found in the woods later the same day. Hoover’s hand was still on the ripcord of an unopened parachute and further investigations revealed that he had been hit by pieces of the aircraft, which had suffered two separate explosions.
