October 14

Breaking the Sound Barrier

1947 — Chuck Yeager Flies Faster Than Sound

Flight time not precisely established

On October 14, 1947, Captain Charles E. “Chuck” Yeager climbed into a small orange rocket-powered airplane over the Mojave Desert of California. The aircraft was the Bell X-1. Its shape resembled a .50-caliber machine-gun bullet—an object already known to remain stable at supersonic speeds. The X-1 had not taken off from a runway. Instead, it had been carried into the air beneath a modified B-29 bomber. At approximately 20,000 feet, Yeager climbed into the X-1's cockpit. The carrier aircraft continued upward, eventually releasing the rocket plane at altitude. Yeager ignited its rocket engine. The X-1 accelerated. Then its Mach meter moved beyond 1.0. For the first time in a controlled, instrumented flight, a human being had flown an aircraft faster than the speed of sound. Yeager reached approximately Mach 1.06 at an altitude of about 43,000 feet. The “sound barrier” had been broken. The expression made the achievement sound as though an invisible wall existed in the sky. There was no physical wall. But there was a genuine aerodynamic problem. As aircraft approached the speed of sound, airflow around portions of their wings could become supersonic even while the airplane itself remained below Mach 1. Shock waves formed. Drag increased sharply. Control surfaces could behave unpredictably. Pilots had encountered severe buffeting, loss of control effectiveness, and other dangerous effects while diving at high speeds. Some wondered whether controlled supersonic flight was practical at all. The X-1 program was designed to replace uncertainty with experimental evidence. The aircraft was developed through a partnership involving Bell Aircraft, the U.S. military, and the National Advisory Committee for Aeronautics—NACA, the federal aeronautical research organization that would become the core of NASA in 1958. NACA engineers had spent years studying high-speed airflow. Wind tunnels provided essential information. Instrumentation aboard the X-1 measured what happened during actual flight. Yeager's role was to take the experimental aircraft into the region engineers needed to understand. He did so under less-than-ideal personal circumstances. Two nights before the flight, Yeager had broken two ribs in a horseback-riding accident. Concerned that he might be removed from the mission, he did not report the injury to the flight surgeon. The pain made it difficult for him to close the X-1's hatch. Fellow pilot and engineer Jack Ridley devised a solution: Yeager used part of a broom handle as leverage to secure it. Then he flew. The achievement was not immediately announced publicly because the program remained classified. But the data were clear. Controlled supersonic flight was possible. The significance extended far beyond one airplane. The X-1 became part of a lineage of experimental aircraft known as the X-planes. They explored swept wings, variable geometry, extreme altitudes, supersonic and hypersonic speeds, unusual control systems, and technologies that blurred the distinction between aircraft and spacecraft. The most famous later example was the X-15. Flying during the 1950s and 1960s, the rocket-powered X-15 reached speeds above Mach 6 and altitudes high enough that several pilots qualified for astronaut wings under the U.S. definition of space. Research from such programs contributed to knowledge used in spacecraft design, atmospheric reentry, flight controls, pressure suits, and human performance at extreme speeds and altitudes. The connection between the X-1 and the Space Age is therefore more than symbolic. Before engineers could routinely send people through the atmosphere toward space and return them safely, they had to understand what happened when vehicles crossed regimes that had once seemed nearly impassable. On October 14, 1947, one of those regimes ceased to be a barrier. It became a place where engineers knew how to fly.

Why It Matters: The Bell X-1's first controlled supersonic flight demonstrated that the difficulties encountered near Mach 1 could be understood and overcome through research, engineering, and flight testing. The X-1 program helped establish the experimental-flight tradition that led through later X-planes to the edge of space and contributed directly to the aeronautical knowledge upon which human spaceflight was built.

 

Also on This Day

1968 — Apollo 7 Makes the First Live Television Broadcast from an American Spacecraft

Approximately 72 hours after launch

Three days after Apollo 7 lifted from Cape Kennedy, Americans saw something they had never seen live before. Astronauts broadcasting from an American spacecraft in orbit. NASA had debated whether television belonged aboard Apollo 7 at all. Spacecraft mass was precious. Crew time was precious. Every task competed with engineering tests essential to proving that the redesigned Apollo spacecraft was ready for lunar missions. The crew had already declined an earlier request for a broadcast because commander Wally Schirra believed it interfered with scheduled work. But on October 14, the television camera came on. Viewers saw Schirra, Donn Eisele, and Walt Cunningham inside the command module. The astronauts called their program a transmission “from the lovely Apollo room high atop everything.” The images were crude by modern standards. The camera was small. The pictures were black-and-white. Only certain ground stations could receive and convert the spacecraft's television signal for broadcast. But the psychological effect was significant. Spaceflight was becoming something the public could experience as it happened. Previous American missions had produced photographs, film, radio communications, and extensive news coverage. Live television changed the relationship. People on Earth could watch astronauts floating inside their spacecraft while those astronauts were actually circling the planet. Apollo 7 eventually made seven television broadcasts. The broadcasts were popular enough that the crew later received a special Emmy Award. More importantly, they helped establish television as a central part of Apollo. Two months later, Apollo 8 would send live television pictures from the vicinity of the Moon. On Christmas Eve, hundreds of millions of people would watch as the crew showed the lunar surface and read from Genesis while orbiting another world. Apollo 10 would provide color television from lunar distance. And in July 1969, television would allow people around the world to watch human beings walk on the Moon. That extraordinary global experience had a modest predecessor on October 14, 1968. Three astronauts in Earth orbit turned on a camera.

Why It Matters: Apollo 7's first live television broadcast from an American spacecraft helped transform spaceflight from something the public learned about afterward into something people could witness while it was happening. The broadcast established a communications tradition that would culminate in live pictures from lunar orbit and the surface of the Moon.

2012 — Felix Baumgartner Breaks the Sound Barrier in Free Fall

Jump began shortly after 18:00 UTC

Exactly 65 years after Chuck Yeager exceeded the speed of sound inside the Bell X-1, Austrian skydiver Felix Baumgartner stood outside a capsule suspended beneath a helium balloon high above New Mexico. Below him was approximately 39 kilometers—24 miles—of atmosphere. Then he stepped off. The project was called Red Bull Stratos. Baumgartner had ascended in a pressurized capsule carried by an enormous high-altitude balloon. The surrounding atmosphere was so thin that an unprotected person could not survive. He therefore wore a full-pressure suit similar in principle to equipment developed for high-altitude aviation and spaceflight. Once outside the capsule, Baumgartner began accelerating under gravity. At ordinary skydiving altitudes, increasing air resistance eventually limits a falling person's speed. But at nearly 39 kilometers altitude, the atmosphere was extremely thin. There was much less aerodynamic drag. Baumgartner accelerated to approximately 1,358 kilometers per hour—844 miles per hour, reaching about Mach 1.25 according to the final official analysis. He had become the first person to exceed the speed of sound in free fall without propulsion or a vehicle. For a short period during the descent, Baumgartner entered a dangerous spin. He recovered. After several minutes of free fall, he deployed his parachute and landed safely in the New Mexico desert. The jump set several records at the time, although some were later surpassed. But the scientific and engineering interest went beyond record-setting. The project gathered information relevant to high-altitude pressure suits, human physiological response, parachute systems, and emergency escape from extreme altitudes. Those questions have long been connected with spaceflight. Before astronauts could ride rockets safely, engineers had to understand how people survived at high altitude. Pressure suits developed for aviation helped lead to spacesuits. High-altitude balloon flights helped researchers understand the environment near the edge of space. Emergency escape systems remained a concern for crewed spacecraft. Baumgartner's jump therefore belonged to a much older experimental tradition. And the date created an extraordinary historical symmetry. On October 14, 1947, Chuck Yeager became the first person to travel faster than sound in controlled aircraft flight. On October 14, 2012, Felix Baumgartner became the first person to travel faster than sound while falling through the atmosphere without a vehicle. Sixty-five years separated them. The atmosphere connected them.

Why It Matters: Felix Baumgartner's supersonic free fall demonstrated the capabilities of modern pressure suits and high-altitude life-support systems while providing data relevant to human survival and emergency escape in the upper atmosphere. Its occurrence exactly 65 years after Yeager's historic X-1 flight creates one of the most striking anniversary connections in aerospace history.

 

The Bigger Picture

October 14 is about a boundary that was never really a boundary. The speed of sound once seemed to represent a dividing line. As aircraft approached it, aerodynamic behavior changed dramatically. Shock waves appeared. Control became difficult. Drag increased. The difficulties were real enough that the phrase “sound barrier” entered popular language. But the solution was not simply courage. Chuck Yeager's willingness to fly the X-1 mattered enormously. Yet courage without engineering would not have carried him safely through Mach 1. Scientists had studied compressible airflow. Engineers had designed an aircraft specifically for the transonic region. Wind tunnels had produced data. Instrumentation measured the actual flight. The pilot and machine were parts of a larger scientific experiment. That pattern appears repeatedly in the history of space exploration. What looks impossible often becomes possible when an unknown environment becomes a measured environment. The upper atmosphere was once mysterious. Then balloons, sounding rockets, research aircraft, and satellites measured it. Orbital flight seemed extraordinarily difficult. Then engineers learned how to calculate trajectories, build guidance systems, and protect spacecraft during reentry. Traveling to the Moon required capabilities no human possessed in 1947. Twenty-two years after Yeager's X-1 flight, astronauts were walking there. Felix Baumgartner's 2012 jump brought the story back to the atmosphere. He relied upon technologies descended partly from the same high-altitude research tradition that had connected experimental aviation with early spaceflight. Pressure suits. Life-support systems. High-altitude balloons. Telemetry. Tracking. Medical monitoring. Parachutes. The achievement looked like one person falling from the sky. Behind it stood decades of aerospace engineering. Apollo 7 adds another dimension to the day's theme. Its television broadcast crossed a different kind of boundary. The physical distance between people in space and people on Earth began to feel smaller. Spaceflight became something millions could experience simultaneously. October 14 therefore reminds us that boundaries can take many forms. Some are aerodynamic. Some are technological. Some are psychological. And some exist simply because no one has yet gathered enough knowledge to cross them. The history of astronomy and space exploration is filled with such boundaries. Again and again, humanity approaches one and discovers that what appeared to be a wall was actually a problem waiting to be understood.

At a Glance

1947 — Flight time not precisely established — Chuck Yeager pilots the Bell X-1 beyond Mach 1 over California, achieving the first controlled, instrumented supersonic aircraft flight and opening a new era of high-speed flight research.

1968 — Approximately 72 hours after launch — The Apollo 7 crew conducts the first live television broadcast from an American spacecraft, beginning a communications tradition that will soon bring live pictures from the Moon to audiences on Earth.

2012 — Shortly after 18:00 UTC — Felix Baumgartner jumps from approximately 39 kilometers above New Mexico and becomes the first person to exceed the speed of sound in free fall without propulsion or a vehicle.