A remarkable reunion occurred recently at Edwards AFB, California when the two key veterans involved in the breaking of the sound barrier in 1947 returned to celebrate the 70th anniversary of the achievement. Meeting on stage on October 13, the day before the anniversary, were 94-year-old Brig. Gen (Ret.) Chuck Yeager, pilot of the experimental Bell XS-1 and 97-year-old Brig. Gen. (Ret.) Bob Cardenas, the pilot of the specially modified Boeing B-29 carrier aircraft which launched Yeager on his historic flight.
Kept secret at the time, news of the record speed achievement of Mach 1.06 was broken by Aviation Week two months later, marking one of the industry scoops of the 20th century. At the time, the pursuit of high-speed flight in excess of the speed of sound had become a serious technical challenge for the early jet designers. Teams across America, Britain and France were racing to be the first to push a manned aircraft beyond Mach 1.
On the day of the flight, Cardenas piloted the B-29 to 23,000 ft. over Muroc Dry Lake, California, before releasing the XS-1, later simply designated the X-1. Dropping clear of the bomber Yeager ignited the XS-1’s Reaction Motors XLR11 rocket engine and climbed to 43,000 ft. The rocket accelerated the aircraft to Mach 1.06, or 700 mph, making the XS-1 the first aircraft to fly faster than the speed of sound. The small aircraft, shaped after the contours of the .50 caliber bullet, went on to fly 78 times, and on March 26, 1948, with Yeager in the cockpit, it reached Mach 1.45. This marked the highest speed reached by a manned aircraft up to that time.
Source: http://aviationweek.com/blog/living-sound-barrier-legends
