The Bell X-1 was the rocket-powered aircraft that exceeded the speed of sound in level flight while piloted by legendary test pilot Chuck Yeager on 14 October 1947.
The aircraft, developed largely during World War II by Bell Aircraft along with the National Advisory Committee for Aeronautics (NACA) and the U.S. Army Air Forces (USAAF) and later the US Air Force (USAF), subsequently flew at nearly 1,000 miles per hour (870 knots or 1,600 kilometers per hour) during continued testing in 1948. But did you know that the British might have been able to break the sound barrier first, or that they might have solved a sticky engineering wicket with the X-1?
As early as 1942, the United Kingdom’s Ministry of Aviation (Air Ministry) was working with Miles Aircraft on a top-secret project to design and build the world’s first aircraft capable of breaking the sound barrier in level flight. The turbojet-powered Miles M.52 was designed to reach 1,000 miles per hour, which was more than twice the existing airspeed record at the time in level flight. The aircraft was also expected to be able to climb to an altitude of 36,000 feet (10,973 meters) in just 1 minute and 30 seconds.
The design of the M.52 was 90 percent complete by 1944, and Miles was directed to build three prototypes. Also in 1944, the Air Ministry signed an agreement with the United States to exchange high-speed research and data. Supposedly, the Brits provided drawings of the M.52 and research data to Bell Aircraft, but Bell provided nothing in return.
Bell was already working on a rocket-powered design similar to the M.52, but tail design issues were holding up its development. Miles Aircraft believed a variable-incidence tail design would solve the problem.
The USAAF Flight Test Division and the NACA contracted with the Bell Aircraft Company on 16 March 1945 to build three XS-1 (for “Experimental, Supersonic”) aircraft to obtain flight data on conditions in the transonic speed range. The designation was later changed to X-1.
In simplest terms, the X-1 was a bullet with wings. The shape of the fuselage resembled nothing as much as a .50 caliber bullet- a shape that was known to be stable while flying at supersonic speeds. This created design challenges for the cockpit of the aircraft, which had no room for an ejection seat.
During early testing in 1947, the X-1 experienced in-flight compressibility problems. The tailplane was redesigned to incorporate variable-incidence or “flying” one-piece horizontal stabilizers. This sparked controversy over the potential British contribution to the X-1 design, but in the end, Yeager’s flight tests confirmed that the “flying” tail worked. If it had not, the design of the X-1 would have been radically altered to include delta wings. As it turned out, every experimental “X plane” would be equipped with a flying tail or delta wings from then on.
Reaction Motors Incorporated was one of the very first companies to build liquid-propellant rocket engines in the U.S. They provided the four-chamber rocket engine capable of 6,000 pounds of thrust for the X-1. This rocket engine burned ethyl alcohol diluted with water with a liquid oxygen oxidizer. Thrust could be incrementally increased by using additional chambers.
The first two X-1 engines were equipped with fuel and oxygen tanks pressurized with nitrogen, but the remainder utilized gas-driven turbopumps- necessary to increase the chamber pressure and thrust while making the engine lighter.
The first person to fly the X-1 was Bell Aircraft chief test pilot Jack Woolams. He made the first of ten unpowered glide-flights over Pinecastle Army Airfield in Florida (later McCoy Air Force Base (AFB) and now Orlando International Airport) on January 25th 1946. Powered flights were all flown at Muroc Army Airfield (now Edwards AFB), first by Bell test pilots Woolams and Chalmers “Slick” Goodlin. 26 successful powered flights were conducted between September 1946 and June 1947. But when the USAAF expressed concerns about the cautious pace of Bell flight testing and then Goodlin demanded $150,000 for a first supersonic flight, he was out. And Yeager stepped in. Broken ribs and all.
Just a month after the USAAF became the USAF, on October 14th 1947 Captain Chuck Yeager famously borrowed a stick of Beeman’s and then drop-launched out of the bomb bay of a specially modified Boeing B-29 Superfortress in Bell X-1 USAF serial number 46-062. The all-orange aircraft was named Glamorous Glennis after his wife as all of his USAAF-assigned aircraft had been. On this 50th X-1 flight the aircraft reached Mach 1.06 or 700 miles per hour (610 knots or 1,100 kilometers per hour) at 43,000 feet (13,106 meters). After “breaking the Mach meter” the rocket engines burned out and Yeager glided the now-famous Bell X-1 down to land on the dry lake bed.
The 1947 National Aeronautics Association Collier Trophy went to the three primary participants in the X-1 Program for their supersonic flight. Honored at the White House by President Truman were Larry Bell of Bell Aircraft, pilot USAF Captain Charles “Chuck” Yeager, and John Stack of the NACA. The NACA would eventually become the core of the National Aeronautics and Space Administration- NASA. Although the Air Force tried their best to keep a lid on the story, Aviation Week magazine had it by their December 22nd 1947 issue. The supersonic flight was finally announced to the public on June 10th 1948 by Air Force Secretary Stuart Symington.
Chuck Yeager used X-1 USAF serial number #46-062 to perform the only conventional (runway) launch of the X-1 program, reaching an altitude of 23,000 feet (7,000 meters) in only 90 seconds on January 5th 1949. Later variants of the X-1 were built to test different aspects of supersonic flight. While flying the modified X-1A Yeager experienced inertia coupling and nearly lost the aircraft. The research techniques used for the X-1 program became the pattern for all subsequent X-plane programs. The flight data collected by the NACA from the X-1 tests was used to develop many of the fighter designs designed and built throughout the latter half of the 20th century.
