NASA 

National Aeronautics and 

Facts

Space Administration 

Dryden Flight Research Center 

P.O. Box 273

Edwards, California 93523 

Voice 661-276-3449 

FAX 661-276-3566 

pao@dfrc.nasa.gov FS-2003-07-0085 DFRC 

First Generation X-1 

Photo E-9. X-1/B-29. 

The first generation X-1 aircraft changed aviation history in numerous ways, and not simply because they were 

the first aircraft to fly faster than the speed of sound. Rather, they established the concept of the research aircraft, built solely for experimental purposes, and unhampered by any military or commercial requirements. 

Although subsequent X-planes were built for a wide range of purposes - technology or concept demonstrators, 

unmanned test missiles, and even as prototypes in all but name - the X-1s were built to go faster than an aircraft 

had ever flown before. 

The X-1 resulted from technological challenges facing aircraft designers in the late 1930s and early 1940s. 

Aircraft had begun to experience both subsonic and supersonic airflow over their wings. This created a range of 

undesirable characteristics - compressibility, increased drag, trim changes, severe turbulence, and loss of control 

effectiveness. Wind tunnels were affected by the same aerodynamic problems, and their data proved to be 

unreliable in this regime. As a result, a few individuals - John Stack of the NACA, Ezra Kotchner of the Army 

Air Forces, and Walter Diehl of the Navy - realized a specialized research aircraft offered the only feasible 

means of getting supersonic aeronautical data. 

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Photo E-4837. X-1 on display. 

The Army Air Forces selected Bell Aircraft to build 

three X-1 aircraft. The fuselage was the same shape as 

a 0.50 caliber machine gun bullet, which was known 

to be stable at supersonic speeds. The X-1 wings were 

straight, rather than swept back, and relatively thin for 

the time. The X-1-1 (serial number 46-062) had a 

wing with an 8 percent thickness/chord ratio. The X-1-

2 (serial number 46-063) had a 10 percent ratio wing. 

The X-1 was powered by an XLR-11 rocket engine, 

which had four chambers and burned liquid oxygen 

(LOX) and a mixture of alcohol and water. In 1945, 

rockets were viewed with suspicion by some engineers. Both the NACA and Navy preferred a jetpowered research aircraft, rather than one using a 

rocket, as the Army Air Forces had selected. 

The X-1-1 was delivered by Bell in December 1945. 

At the same time, the Army Air Forces asked that 

NACA personnel oversee the instrumentation and data 

analysis of the X-1 flights. As a result, an NACA team 

was incorporated into the program. The first glide 

flight of the X-1 occurred on Jan. 19, 1946, at 

Pinecastle Field, Fla., by Bell test pilot Jack Woolams. 

The X-1-1 was air launched from a B-29. Woolams 

made a total of 10 glide flights to test the X-1’s lowspeed handing before it was returned to Bell in March 

1946 for installation of the rocket engine. The aircraft 

was delivered to Muroc in October 1946. 

The first group of NACA engineers arrived at Muroc 

Field (now Edwards Air Force Base, Calif.), in September 1946 in preparation for the initial flights of the 

X-1-2. Bell test pilot Chalmers "Slick" Goodlin made 

the first glide flight in the X-1-2 on Oct. 11, 1946. 

After a total of four glide flights, he made the first 

powered flight on Dec. 9, reaching a speed of Mach 

0.79. By June 1947, Bell had proven the airworthiness

of both X-1s up to speeds of Mach 0.8. The contract 

freed the company from responsibility above this 

speed. 

On June 30, 1947, Army Air Forces and NACA 

representatives agreed on a two-phase flight program. 

The Army Air Forces would use the X-1-1, with its 

thinner wing, to conduct an accelerated program to 

reach Mach 1.1 as quickly as possible. The NACA 

would provide support, such as technical advice and 

data analysis. The NACA would then undertake a 

slower-paced, more detailed series of research flights 

at transonic (near the speed of sound) speeds, using 

the X-1-2 and its thicker wing. 

Capt. Charles E. “Chuck” Yeager was selected as the 

pilot for flights to Mach 1. He made his first glide 

flights on Aug. 6, 7, and 8, 1947. Yeager undertook 

his first powered flight in the X-1-1 on Aug. 29, 

reaching Mach 0.85. Over the next six weeks, Yeager 

came closer to Mach 1, reaching Mach 0.997 on Oct. 

10. For the NACA engineers, used to a more cautious 

step-by-step approach, Yeager and the Air Force 

seemed to be acting in haste. Still, on Oct. 14, Yeager 

reached a speed of Mach 1.06 at 43,000 feet, becoming the first man to fly supersonic. Air Force officials 

designated the flight and all data as Top Secret two 

hours later. Not until December 1947 would word leak 

of the achievement, and it was not until March 1948 

that the U.S. Air Force officially confirmed the 

achievement 

The NACA now began flying the X-1-2 on research 

Photo E60-6204A. X-1 in flight with copy of "mach jump" 

paper tape data record of the first supersonic flight. 

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missions. On Oct. 21, 1947, NACA pilot Herbert H. 

Hoover made a glide flight. Hoover followed this 

mission on Dec. 16 with a powered flight to Mach 

0.84. In January 1948, a second NACA research pilot,

Howard C. Lilly, joined the program. The initial 

NACA flights in the aircraft sought data on turns and 

pull ups, side slips, and elevator effectiveness at 

subsonic speeds. It was not until March 4, 1948, that 

Hoover reached Mach 1.029. Hoover became the 

second man to reach Mach 1, on the first NACA and 

the first civilian supersonic flight. Lilly flew at Mach 

1.1 on March 31.

Robert A. Champine replaced Hoover and Lilly on the 

X-1 program in November 1948, undertaking studies 

of wing pressure distribution, stability and control, and 

stabilizer effectiveness. John H. Griffith continued 

these research efforts when he replaced Champine on 

the X-1 program. Griffith flew the X-1-2 through 

October 1950, when he left the NACA for a job as a 

company test pilot. A. Scott Crossfield joined the 

research efforts in April 1951, adding Joe Walker in 

August. 

The research usefulness of the first generation X-1 

aircraft was nearing an end. The second generation X1 aircraft, then under development, would be able to 

reach twice the speed of sound. After Yeager’s Mach 

1 flight, the X-1-1 had been used by the Air Force to 

acquire data on stability and control, wing and tail 

loading, high-altitude flight, and pilot familiarization. 

After a final flight by Yeager on May 12, 1950, the X1-1 was retired and given to the Smithsonian Institution. The X-1-2 continued flying, but technical problems brought its work to a close. The X-1-1 and X-1-2 

both used a fuel system pressurized with nitrogen. The 

X-1-2’s nitrogen tanks were nearing the end of their 

fatigue life, risking a possible explosion. Consequently, NACA officials grounded the X-1-2, which 

later returned in a much modified state as the X-1E. 

The X-1-3 (serial number 46-064) represented the 

final example of first generation X-1 series. The X-1-3 

was externally identical to the other two aircraft. The 

fuel system in the X-1-3 did not rely on nitrogen 

pressure, however, but rather on a turbopump. This 

eliminated the need for the heavy nitrogen tanks, and 

resulted in a calculated maximum speed of Mach 2.4, 

Photo E49-001. X-1-2 on lakebed. 

a full Mach number higher than the X-1-1 or X-1-2 

could reach. Funding cuts and turbopump development problems, however, delayed the aircraft a full 

three years. The Air Force had also contracted with 

Bell Aircraft to develop the second generation X-1A, 

X-1B, and X-1D. Interest in the X-1-3 faded, and the 

Air Force cancelled it. The NACA, wanting its own 

Mach 2 aircraft to experiment with, picked up the Air 

Force's canceled X-1-3. 

The X-1-3 was delivered to Edwards in April 1951. 

Bell test pilot Joseph Cannon successfully made a 

glide flight in the aircraft on July 20. On Nov. 9, 1951, 

a captive flight was made by the X-1-3 aboard the B50 launch aircraft. This was to be a rehearsal for the 

first powered flight, as well as a test of the jettisoning 

system. Engineers cancelled the jettisoning tests, 

however, when nitrogen pressure fell. The B-50 with 

the fully fueled X-1-3 still attached landed back at 

Edwards safely, and preparations began to jettison the 

LOX. As Cannon pressurized the LOX tank, however, 

a dull thud was heard, followed by a hiss and a small 

cloud of white vapor escaped from the X-1-3’s center 

section. Then, a violent explosion occurred, with 

yellow flames and black smoke engulfing both the X1-3 and the B-50. Cannon escaped from the X-1-3, but 

spent nearly a year in the hospital recovering from 

severe burns on his legs, arms and body. The fire and 

subsequent explosions destroyed both the X-1-3 and 

B-50. 

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