How Chuck Yeager Reached Supersonic Speed

“When we weren’t flying, we zipped on our leather flight jackets, crowded around the blackjack tables of the Tonopah Club, drank ourselves blind on rotgut, then staggered over to the local cathouse.”

That’s how America’s most famous fighter pilot, Chuck Yeager, describes himself and his 18-year-old pals in 1941, as they completed Army Air Corps training before taking part in World War II. By the time the war was over, Yeager had flown 64 missions, logged 13 “kills,” and had been shot down over enemy territory in German-occupied France (only to escape). His extraordinary aviation talents were evident, and he soon enrolled in the newly constituted U.S. Air Force. But his was no ordinary stint in the service. In 1947, Yeager volunteered to be the test pilot for a top-secret, rocket-powered plane dubbed X-S-1. The ‘X’ stood for experimental. The ‘S’ meant it would fly at supersonic speed. And the ‘1’ indicated that it was to be the first aircraft to break the sound barrier—if Yeager didn’t die trying.

The Flight Plan

Why would the swaggering stud from Hamlin, W. Va., risk his neck to achieve supersonic speed? Simply stated, America had to do so if it was going to compete with the Germans and the Japanese, and Yeager knew it. During the war, American fighter pilots such as Yeager would often shake enemies off their tails by diving during dogfights, sending planes plummeting at close to supersonic speeds. Military engineers feared that if the machines hit the so-called sound barrier while doing this, it would cause them to break apart. On the other hand, they also knew that if they could harness new jet engines to propel fighters faster than the speed of sound, the planes would be impossibly difficult to shoot down.

In order to create a supersonic plane, engineers faced a few problems. First, they had to build an aircraft tough enough to withstand a “sonic boom.” When a plane flies, it pushes the air in front of it, creating waves of compressed air molecules, similar to the way water waves build up at the bow of a boat and fan out on each side. But as an airplane reaches the speed of sound, it pushes these waves so hard that they actually collide, creating earsplitting shock waves, or those famous sonic booms.

While engineers reached the point at which they could build an aircraft tough enough to withstand the shock wave punch, their bigger concern was that the waves could leave a dead wake behind them. With no air for the plane’s control flaps to press against, the craft could suddenly nosedive. Facing this risk, the logical thing would be to test the experimental plane in a wind tunnel, but laboratory tunnels maxed out at 85 percent of the speed of sound, (or Mach 1, which at sea level is 760 mph.) In the end, the only way to test the X-1 was to strap Yeager into the jet and light a candle.

This is Only a Test

This was the game plan: Yeager would be piloting the carefully crafted X-1. Shaped like a bullet with two stubby wings and a high tail, the 31-foot-long plane would be loaded with 600 gallons of liquid oxygen and alcohol fuel stored (precariously) right behind the pilot’s seat. Even more risky, the X-1 wouldn’t take off on its own. It would actually be hung from the bomb-release hook inside a B-29 bomber, which another pilot would fly up to 25,000 feet. At that point, Yeager would climb down a spindly ladder to the X-1, dangling in the dark bomb bay, and crawl into its tiny cockpit. The B-29 pilot would then open the bomb door and drop Yeager into the sky. Plummeting like a rock, Yeager would fire the X-1’s four rocket engines in succession, blasting him up to nearly 40,000 feet and straight through the sound barrier. But this wasn’t a one-off attempt. Over the course of several months, Yeager was to make a series of flights, each designed to push the X-1 incrementally closer to Mach 1.

Finally, the first test day arrived. In his 1985 autobiography, Yeager admits that as the B-29 climbed into the air that day, he crawled into the X-1 cockpit “and waited to be dropped like a [expletive] bomb.” Suddenly, the bay door opened, the cable released, and Yeager fell into blinding sunlight while being chilled to the bone from the liquid oxygen tanks behind him. Now Yeager had to ignite the first rocket. “If you are gonna be blown up,” he notes, “this is likely to be when.” He threw the switch and—wham!—he was thrown back into his seat as the rocket blasted the plane skyward. Yeager ignited the other rockets and, per plan, reached Mach 0.85 at 35,000 feet.

At this point, Yeager’s instructions were to cut off the engines, jettison the remaining fuel, and sweep toward the desert floor, landing gingerly like a glider. But Yeager wasn’t one to play by the rules. Instead, he dove straight down to 300 feet, leveled off over the air base, and re-lit all four rockets. The unexpected maneuver blew a 30-foot flame out the back of the X-1 as it screamed straight back up to Mach 0.82. The next day, the highest-ranking colonel at the air base told Yeager to obey orders, or he’d be gone.

Breaking Waves

Plenty went wrong during subsequent runs. On Flight 7, as Yeager reached Mach 0.94, he lost all control of the plane’s tail due to the compression waves. Design changes were made, and on Flight 8, Yeager hit Mach 0.955. The plane shook violently, but the new tail controls held up. Yeager, however, was sweating so profusely as he fought the buffeting that his evaporating body moisture frosted the inside of his windshield—meaning he essentially had to land the X-1 blind.

Exhausted and tense, Yeager knew he was getting closer to the goal, and that his next flight might be “the one.” To let off some steam, he took his wife, Glennis, out to Pancho’s, the lone establishment at the edge of the air base where test pilots raised hell. Florence “Pancho” Barnes, the female proprietor and self-described desert rat, kept some horses out back, and after dinner, Chuck and Glennis raced after one another on horseback under the pitch-black sky. Unfortunately, Yeager didn’t see the oncoming fence until his horse suddenly veered off. He was thrown to the dirt, and cracked two ribs in the fall. Knowing he’d be grounded if he reported to the base doctor, Yeager had his wife sneak him out of town where a local doc taped him up.


Yeager knew he could still fly, but there was one thing those cracked ribs wouldn’t allow him to do: close and latch the cockpit door after climbing into the plane. So the night before he was scheduled to fly, Yeager called his project engineer, Jack Ridley (pictured with Yeager), and the duo slipped into the X-1 hanger. The ingenious Ridley sawed off a broomstick that Yeager could jam into the door as a lever, and they hid the stick beside the seat.

The next morning, on October 14, 1947, Yeager climbed aboard the mothership, and its pilot took them up to 25,000 feet. Yeager struggled down the ladder, crumpled into the X-1 seat, felt for the broomstick, and locked the door. After the B-29 dropped him, Yeager fired two rockets and raced upward. At Mach 0.96, the plane buffeted strongly, and he fired the third and fourth rockets. The speed gauge fluttered, then tipped right off the scale. Suddenly, Yeager’s ride was smooth as silk. Shock waves were forming behind the plane, and Air Force personnel on the ground were pounded with sonic booms. Yeager maxed out at Mach 1.07, then glided the X-1 in. “After all the anticipation,” Yeager would write later, “it really was a letdown. It took a damned instrument to tell me what I’d done. There should have been a bump on the road. Something to let you know you had just punched a nice clean hole through that sonic barrier.”

All Quiet on the PR Front

Despite his achievement, Yeager couldn’t really celebrate. The feat had to be kept secret because spies were always lurking around. It wasn’t until months later that the military announced the record-breaking flight, managing to obscure the technical details from the public. The secrecy worked. Several years later, when the newest American fighter planes, the F-86s, engaged Soviet MiGs over Korea, the superior speed advantage resulted in a kill rate of 10-to-1.

Yeager’s career, however, was far from over. The gutsy pilot had plenty of white-knuckle sessions after the historic flight, including his very next trip on the X-1. Just after being released from the bomb bay, the plane lost all electrical power, and Yeager dropped like a boulder toward the Earth. Fortunately, he managed to dump the 5,000 pounds of explosive fuel he had onboard and manually level the barreling bullet—just seconds before it would have plowed into the ground.

Yeager spent seven more years as a test pilot, and in 1953, he reached Mach 2.44. He also trained military pilots to become some of the first astronauts, but was never chosen himself—an irony dramatized in the 1983 movie, The Right Stuff. Yeager retired in 1975 as a brigadier general.

The next year, the Concorde SST became the first commercial airliner to fly passengers at Mach speeds. A decade later, inspired by the posh plane and space shuttle flights, President Ronald Reagan proposed a hypersonic “space plane” that would fly from Washington to Tokyo in two hours. The notion evolved into an embattled NASA program, the X-43A. On March 27, 2004, the needle-nosed bullet was dropped from a B-52B bomber and its novel “scramjet” engines fired it to Mach 7 at the incredible altitude of 95,000 feet. But there was no Yeager-esque cowboy at the controls; the test flight went unmanned.


This article by Mark Fischetti is from the July-August 2004 issue of mental_floss magazine. It is reprinted here with permission.

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The excellent kill ratio of the F-86 over the MiG-15 wasn't because of a speed advantage (the MiG was actually slightly faster). It was due to the better training of the US pilots. Chuck Yeager proved this by "shooting down" a fellow US pilot flying a captured enemy plane in mock combat. After they landed the two pilots swapped planes and Yeager shot his opponent down again.
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