What You May Not Know About Breaking The Sound Barrier

On October 14, 1947, history was made when U.S. Air Force Capt. "Chuck" Yeager flew the rocket-powered Bell X-1 to Mach 1.06 (700 mph) at an altitude of 45,000 ft. over Muroc Army Airfield in California. This was the first manned aircraft flight faster than the speed of sound. Seventy years later, the flight still ranks as one of the most significant milestones in aviation history.

Behind every great paradigm shifting moment like this are the interesting details that rarely see the light of day. Here are some things you may not have known about the pilots, aircraft and research program that made this event possible.

Bell X-1A, mach 2+ rocket plane with Chuck Yeager. Circa 1953

  • There were a total of six Bell X-1s built: three first-generation aircraft like Yeager's, and three second-generation aircraft that were bigger, faster, and higher flying. Of the three first-generation aircraft, Yeager's - bearing the serial number 46-062 - was the first.
  • The X-1 was built for research purposes. The fuselage was modeled after a .50 caliber bullet. It was powered by a single Reaction Motors XLR-11 four-chamber rocket engine that produced 6,000 pounds of thrust (each chamber produced 1,500 pounds of thrust). The propellants for the engine (water/alcohol mix and liquid oxygen) were carried in two large tanks in the fuselage.
  • A total of eighteen pilots flew the three first-generation Bell X-1s. Air Force pilot "Chuck" Yeager logged the most flights with 34; a Bell test pilot, "Slick" Goodlin, had the second greatest number of flights with 26.
  • The fastest speed achieved by any of the first-generation Bell X-1s was Mach 1.45 (957 mph). Yeager made that flight on March 26, 1948.
  • There were three different wings built and flown on the three first-generation Bell X-1s. Each differed in thickness with the thinnest being the fastest and the one utilized on Yeager's aircraft.
  • Instead of taking off under their own power, the Bell X-1s had to be carried to launch altitude by a specially-modified Boeing B-29 "mother" plane and dropped. Rocket power is relatively short lived and propellants are consumed in prodigious quantities, thus requiring the X-1s to be carried to launch altitude (usually around 20,000 feet). The X-1's powered endurance was around five minutes following launch.
  • The X-1 took off under its own power only once during the course of its flight test program. The flight took place on January 5, 1949, again with Yeager at the controls. The aircraft reached an altitude of 23,000 feet before the engine was shut down. After dumping residual fuel, the X-1 glided back to its takeoff spot and landed.
  • Two days before Yeager became the world's fastest human, he broke two ribs as a result of being thrown from a horse while riding with his wife, Glennis. Knowing he wouldn't be allowed to fly if his injury was discovered, he visited a doctor off-base to be examined and have his ribs taped. He later used a broom handle to close and latch the X-1's cockpit hatch since he was unable to reach it without suffering excruciating pain.
  • The Bell X-1 that "Chuck" Yeager broke the sound barrier in was delivered to the Smithsonian Institution on August 6, 1950. It has been on public display there ever since - though it now hangs from the ceiling of the main entrance hall to the Smithsonian's National Air & Space Museum. It is considered a national treasure.

Bell X-1