The first high speed frontier.

260 years of unsolved and unknown regime of high speed dynamics of gases were broken with the significant flight of the Bell X-1 research vehicle installed under the B-29 bomber of World War II vintage, on October 14, 1947 in the Mojave Desert in California.

X-1 on the Ramp with the B-29. Source: Nasa

At an altitude of 25,000 feet the X-1 was dropped from the mothership B-29 and Captain Charles E. (Chuck) Yeager was at the controls of the X-1. At a speed of 250 miles per hour the X-1 dropped into free fall and with reaction Motors XLR-11, the aircraft was powered and climbed rapidly similar to a rocket. In this ascend, the X-1 approached Mach 0.85, a speed where there is no scientific data and even in wind tunnels.

When the X-1 reached over 0.95 Mach, shock waves were shaping over the top surface of the wings. At an altitude of 46,000 feet, the aircraft started to level off while the Mach number reach to 1.02 Mach. Yeager in control, the first man controlling an airplane in those speeds, witnessed what happened to the plane, a stronger bow shockwave formed ahead of the needlelike nose of the airplane, a velocity of 700 miles per hour, Mach 1.06, at 43,000 feet. At that moment Yeager became the first pilot to fly faster than the speed of sound and the Bell X-1, became the first successful supersonic airplane.

Bell X-1. Source: Nasa

We call the speed range just below and just above the sonic speed-Mach number nearly equal to 1-the transonic range. Dryden [Hugh Dryden, well-known fluid dynamicist and past administrator of the National Advisory Committee for Aeronautics] and I invented the word ‘transonic’ We had found that a word was needed to denote the critical speed range of which we were talking. We could not agree whether it should be written with one s or two. Dryden was logical and wanted two s’s. I thought it wasn’t necessary always to be logical in aeronautics, so I wrote it with one s. I introduced the term in this form in a report to the Air Force. I am not sure whether the general who read it knew what it meant, but his answer contained the word, so it seemed to be officially accepted. . . . I will remember this period (about 1941) when designers were rather frantic because of the unexpected difficulties of transonic flight. They thought the troubles indicated a failure in aerodynamic theory.

Theodore von Kármán, Aerodynamics.

A sonic boom was propagated in the California desert by the high speed flight (supersonic) of the X-1, that was a dramatic event and significant for the aerodynamics. Isaac Newton hundreds years before had studied the first calculation of the speed of sound on air, that gives an idea where the sound was taking importance and defining the speed of sound.

The flight of The X-1 was kept secret and it would fly more than a hundred more times, reaching a speed of Mach 1.45.

X-1 dropped. Source: U.S. Air Force/

The X-1 was design in such a way that it could withstand the unknown regime of high speed, and taking into account it was crewed. So, aspects of safety and high engineering applied in the construction and flight testing program of this outstanding airplane were key, and Bell Aircraft Corp was awarded. NACA was responsible for the instrumentation that was housed inside the Bell X-1, an unique instrumentation of that time.

Instrumentation of the X-1. Source: Nasa

That represented one of the most important stories in the history of aeronautical engineering, the data provided was very technical, the history of the aerodynamics was broaden, new doors were open, and the X-1 helps to the NACA approves the already studied theories about the high speed aerodynamics, a very different field from the subsonic fluid dynamics.


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