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Bell X-1

On October 14, 1947, Captain Charles ‘Chuck’ Yeager of the United States Air Force achieved the historic milestone of becoming the first pilot to exceed the speed of sound while piloting the Bell XS-1 #1 aircraft.

The XS-1, later known as the X-1, attained a speed of Mach 1.06, equivalent to 700 miles per hour, at an altitude of 43,000 feet above the Mojave Desert in close proximity to Muroc Dry Lake, California.

This groundbreaking flight not only showcased the possibility of designing aircraft capable of surpassing the speed of sound but also shattered the long-standing belief in the existence of a so-called ‘sound barrier’.

The XS-1 project was established through a collaborative effort between the National Advisory Committee for Aeronautics (NACA) and the U.S. Army Air Forces (later the U.S. Air Force) in 1944 to create specialised manned transonic and supersonic research aircraft.

A contract was granted to the Bell Aircraft Corporation of Buffalo, New York, by the Army Air Technical Service Command on March 16, 1945, to construct three transonic and supersonic research aircraft as part of project MX-653.

The Army designated these aircraft as XS-1, with the ‘XS’ standing for Experimental Sonic-i.

Bell Aircraft successfully constructed three rocket-powered XS-1 aircraft.

The XS-1 #2 (46-063) underwent flight testing by NACA and was subsequently converted into the X-1 “Mach 24” research aircraft.

The X-1 #3 (46-064) featured a low-pressure fuel feed system driven by a turbopump.

Referred to as the X-1-3 Queenie, this aircraft met its demise in 1951 due to a ground explosion that caused injuries to its pilot.

Following these events, three more X-1 aircraft were manufactured and subjected to test flights.

Unfortunately, the X-1A and X-1D were lost due to explosions in their propulsion systems.

Both XS-1 aircraft were constructed using high-strength aluminium, while their propellant tanks were made of steel.

Unlike the first two XS-1 aircraft, they did not rely on turbopumps for fuel feed to the rocket engine, opting instead for direct nitrogen pressurisation of the fuel-feed system.

The streamlined appearance of the XS-1, modelled after the contours of a .50-calibre machine gun bullet, hid a compact fuselage housing two propellant tanks, twelve nitrogen spheres for fuel and cabin pressurisation, the pressurised cockpit for the pilot, three pressure regulators, a retractable landing gear, the wing carry-through structure, a 6,000-pound-thrust rocket engine from Reaction Motors, Inc., and more than five hundred pounds of specialised flight-test instrumentation.

Originally intended for conventional ground take-offs, all X-1 aircraft were actually air-launched from Boeing B-29 or B-50 Superfortress aircraft.

Due to the performance drawbacks and safety risks associated with launching rocket-propelled aircraft from the ground, mission planners opted for air-launching as a safer alternative.

However, on January 5, 1949, the X-1 #1 Glamorous Glennis managed a successful ground take-off from Muroc Dry Lake, with Chuck Yeager at the controls.

The X-1 #1 achieved a maximum speed of Mach 1.45 at 40,130 feet, which is approximately 957 mph, during a flight by Yeager on March 26, 1948.

Then, on August 8, 1949, Maj. Frank K. Everest, Jr., of the USAF, reached an altitude of 71,902 feet, marking the highest flight ever made by a small rocket aeroplane.

The flight test operations of the X-1 continued until mid-1950, during which it successfully completed a total of nineteen contractor demonstration flights and fifty-nine Air Force test flights.

On August 26, 1950, Air Force Chief of Staff Gen. Hoyt Vandenberg officially presented the X-1 #1 to Alexander Wetmore, who was then serving as the Secretary of the Smithsonian Institution.

General Vandenberg emphasised that the X-1 marked the transition from the subsonic era to the supersonic era, signifying the beginning of a new chapter in aviation history.

Prior to this event, Bell Aircraft President Lawrence D. Bell, NACA scientist John Stack, and Air Force test pilot Chuck Yeager were honoured with the 1947 Robert J. Collier Trophy for their groundbreaking achievement of breaking the sound barrier and paving the way for practical supersonic flight.





30 ft 11 in (9.42 m)

X-1A, X-1B, X-1D

35 ft 8 in (10.87 m)


35.0 ft (10.67 m)


28 ft 0 in (8.53 m)


22 ft 10 in (6.96 m)


10 ft 10 in (3.30 m)

Wing area

130 sq ft (12 m2) ⠀


115 sq ft (10.7 m2)



NACA 65-110 (10% thickness)


X-1A, X-1B, X-1D

NACA 65-108 (8% thickness)


NACA 64A004

Empty weight

7,000 lb (3,175 kg)

X-1A, X-1B, X-1C, X-1D

6,880 lb (3,120 kg)


6,850 lb (3,110 kg)

Gross weight

12,250 lb (5,557 kg)

X-1A, X-1B, X-1C, X-1D

16,487 lb (7,478 kg)


14,750 lb (6,690 kg)


1 × Reaction Motors XLR11-RM-3

4-chamber liquid-fuelled rocket engine,

6,000 lbf (27 kN) thrust


Reaction Motors RMI LR-8-RM-5 6,000 lbf (27 kN)


Maximum speed

1,612 mph (2,594 km/h, 1,401 kn)


1,450 mph (1,260 kn; 2,330 km/h)

Maximum speed

Mach 2.44




5 minutes powered flight

X-1A, X-1B, X-1C, X-1D

4 minutes, 40 seconds powered flight


4 minutes, 45 seconds powered flight

Service ceiling

70,000 ft (21,000 m)

X-1A, X-1B, X-1C, X-1D

90,000 ft (27,000 m)


75,000 ft (23,000 m)


Bell X-1 Concept Aircraft, Prototypes, X-Planes and Experimental Aircraft-J Winchester.

The X-Planes: X-1 to X-45-J Miller.

Aerofax Datagraph 3-Bell X-1 Variants-B Guenther & J Miller.

X Planes 1, Bell X-1-P Davies.

Bell X-1 | Smithsonian Institution

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