On Oct. 14, 1947, 24-year-old U.S. Air Force officer Chuck Yeager became the first pilot in human history to reach – and importantly, survive – supersonic flight. That means he flew faster than the speed of sound, or roughly 768 mph (1,236 kph) at sea level, also known as Mach 1.
Yeager flew straight into the record books aboard the legendary Bell X-1 rocket plane that he named the Glamourous Glennis, after his wife. His neck-snapping ride was kept under wraps by the government until the following year. But when the news broke, he become an international celebrity.
"When Yeager made his flight, he demonstrated that supersonic flight was possible, and that there was no barrier," says Bob Van der Linden, curator of Air Transportation and Special Purpose Aircraft at the Smithsonian National Air and Space Museum via email. "To paraphrase Yeager, the only barrier was in our lack of knowledge."
Following his first sonic boom (the crash created by planes breaking the sound barrier), Yeager continued his career as a test pilot, surviving incredible "Mission Impossible"-worthy near-death accidents, time and again.
And he did all of this after enduring World War II (WWII) where early on he was shot down over enemy territory. With the help of the French Resistance, he evaded capture and returned to base.
His war should have been over, as U.S. Air Force regulations specified that anyone assisted by the resistance would not be allowed to fly again. The idea was that because these rescued pilots were familiar with resistance routes and tactics, they could potentially be tortured into giving up secret information.
But Yeager appealed that decision all the way up to Allied commander Gen. Dwight Eisenhower, and eventually got his wish. He ultimately recorded 11.5 victories— at one point downing five enemy aircraft in a single day, an act that vindicated his reinstatement.
"Yeager was an exceptional, highly intelligent pilot who possessed a remarkable, innate understanding of machines," says Van der Linden. "A World War II ace, he was a quick study who was able to translate what he experienced in the cockpit to the engineers on the ground in the days before computers."
Without his return to combat, Yeager said, he probably never would've been the pilot who broke the speed of sound. He was selected for the test pilot program because of his instinctive flying skills and his ability to remain calm under enormous pressure.
Before Yeager did it, it was commonly thought that you couldn't break the sound barrier. Pilots during WWII had reported that their planes ripped apart when they approached that speed, as if hitting a "wall." Later on, engineers realized breaking the wall depended on plane design.
The engineering component of Yeager's feat cannot be overstated. His aviation acumen was unmatched, but so too were the skills of the teams that designed and built the X-1. Together, they did things no human had before.
"Yeager's achievement (and that of the engineers who designed his aircraft, the X-1) took a critical step not only in high speed and high-altitude flight, but in space exploration and aviation safety," says Matthew Hersch, science history professor at Harvard University, via email. "Throughout World War II, airplanes that accelerated too quickly sometimes disappeared or shattered in mid-air, torn apart by aerodynamic shockwaves. Figuring how to achieve transonic flight was of critical importance to making aircraft not just faster, but safer."
Hersch adds that earlier aircraft powered by propellers and the first turbojet engines could achieve near-supersonic speeds during steep dives but had fuselages and wings that were particularly vulnerable to transonic instability. "Compressibility," he says, killed many pilots but proved difficult to remedy. "Bell Aircraft's X-1 was modeled on a .50 caliber bullet, which was known to fly at supersonic speeds without deforming. The addition of thin wings, a rocket engine, and a tail design borrowed from British research gave the plane the speed and stability it needed to break the sound barrier in level flight ... outrunning the shockwaves that had destroyed earlier aircraft."
Yet for all its technological innovations, the X-1 couldn't fly itself. Bell needed someone who could safely guide their rocket plane into the thinnest of air. Yeager was sure he'd emerge unscathed.
"He was confident that his aircraft would survive the flight because he knew that bullets fired across the desert managed to break the sound barrier and hit the sand undamaged, and the X-1 had the same shape," says Hersch. "He also adapted quickly to the counterintuitive effects transonic speeds had on the X-1's flight controls, and kept his head throughout dangerous, difficult flight. The fact that he fractured two ribs while horseback riding the night before the flight didn't slow him down, either."
Guts and Grit
Nothing in life seemed to slow Yeager down. He was born in poverty in West Virginia. But he was a quick study in the lessons his father taught him, particularly with regards to self-sufficiency and mechanical work.
After mediocre grades in high school, he opted to join the Air Force as a mechanic, hoping to see more of the world. But during WWII, fate intervened with the "Flying Sergeants" program that offered flight training.
After the war, he stayed with the Air Force, becoming a test pilot, breaking the sound barrier as well as performing other amazing feats.
In 1953, he set out to break Mach 2 aboard the X-1A. He succeeded at hitting Mach 2.44 – but then the plane flew violently out of control, losing 50,000 feet (15,240 meters) of altitude in just 60 seconds. Miraculously, he regained control of the aircraft and landed without further problems.
Ten years later, Yeager took a Lockheed F-104 Starfighter to 104,000 feet (31,700 meters). Then, he lost control and began gyrating in every direction, dropping like a granite rock toward certain death. He managed to eject and was struck in the face by his rocket seat, breaking his helmet visor and igniting the pure oxygen inside, severely burning his face and neck. He endured multiple skin grafts to repair his injuries.
In 1960, Yeager was appointed director of the Space School at Edwards Air Force Base. In 1966, he went to Vietnam as a wing commander where he flew more than 120 combat missions. But despite all his heroics, much of Yeager's legacy always goes back to his sound-shattering ride in 1947.
"I think people overlook the fact that this flight was not about setting records, but about exploring the unknown, confronting a problem and solving it," says Van der Linden. "The data gathered by the X-1, and the solutions that Bell, the Air Force, and the NACA found, made supersonic flight not only possible but commonplace, at least in the military."
Knowledge is power, he adds.
"What was learned from the X-1 gave the United States an important lead in the Cold War and helped to keep the U.S. in the forefront of aeronautics."