When Yeager Eased Through the Sound Barrier

Yeager in the cockpit of the Bell XS-1. Credit: National Air and Space Museum Archives, Smithsonian Institution

It’s an interesting historic parallel. Weather permitting, Austrian daredevil Felix Baumgartner is set to break Joe Kittinger’s high altitude jump record this morning by sky diving from 120,000 feet. On the way down he’s going to break the sound barrier without the benefit of an aerodynamic shell like a fuselage, 65 years to the day that Chuck Yeager broke the sound barrier in the Bell X-1. On October 14, 1947, Yeager ushered in a new era of supersonic aviation where faster planes started reaching the fringes of space. 

For decades, the sound barrier had been a problem for pilots and aeronautical engineers. Air builds up in front of and around an aircraft as it approaches the speed of sound; it can’t move out of the way fast enough. The air in front of the aircraft increases drag and reducing lift. At the same time, the air traveling over the top of the wing reaches the speed of sound and forms shockwaves that move back and forth. This disrupts the airflow and causes the aircraft to buffet and shake.

Pilots typically lost control in this transonic region – traveling between Mach 0.8 and Mach 1.2 – and in many cases couldn’t recover the aircraft. In many cases, they approached or broke the speed of sound in a dive, meaning they were in a bad situation already.

A model Bell XS-2 tested in a wind tunnel. In addition to the wind tunnel’s walls disturbing airflow around the models, the struts that held a model up created problems for engineers. Credit: NASA

The National Advisory Committee for Aeronautics attempted to gather data on the transonic flight problem in wind tunnels but the data was no good. The same shockwaves that buffeted the aircraft in flight bounced around inside the wind tunnel. The only solution was to build a research aircraft and just fly it through Mach 1 in level flight.

The NACA and the U.S. Air Force took up the challenge, awarding the contract for the aircraft’s construction to Bell Aircraft. Bell took its inspiration from a bullet since bullets flew faster than sound leaving the barrel of a gun. The XS-1 (for Experimental, Supersonic) was looked like a swollen torpedo with stubby wings and a long tapering nose painted bright orange so ground observers could track it in the sky. It held 8,000 pounds of fuel, but that still wasn’t enough to reach supersonic speeds after a runway takeoff. The solution was to launch it from a mothership in the air, conserving all its fuel for the short powered flight. It would, by default, make an unpowered landing on the dry lakebed at Muroc Air Field (later renamed Edwards Air Force Base). And Yeager was the man to fly it.

Yeager was like some sort of airplane whisperer. He had no formal education in aeronautical engineering but could feel when something as wrong. When a flight didn’t go well, his instinctual analysis of the problem was often the same conclusion engineers came to after a lengthy assessment. Yeager knew that when he was in an aircraft he was the one in charge, not the machine, and he knew he could control the XS-1.

Roll-out of the Boeing B-29A mother ship with a variation of the XS-1, the X-1-2, mated and ready for flight in September, 1949. Credit: NASA

The morning of October 14, 1947, Yeager was in the cockpit of B-29 with his good firend and longtime sidekick Jack Ridley and Bob Cardenas in the pilot’s seat. Underneath the bomber’s belly visible through its open bomb bay doors was the orange XS-1, its cockpit open waiting for a pilot. The flight plan that day called for Yeager to take the X-1 to Mach 0.97, which he was happy to do; he’d broken two ribs the night before after being thrown from a horse and suspected a gentler flight would be safest. But he was tired of conservative flights, edging close to but never reaching Mach 1. This was his ninth flight in the XS-1. He knew how to fly it. Climbing down the ladder through the B-29’s bomb bay doors into the orange aircraft’s cockpit that morning, he decided that unless some unexpected problem developed on the morning’s flight he’d take the XS-1 to Mach 1 on his next flight. Yeager closed the X-1’s cockpit with a sawed off broom handle Ridley had left on the seat – his broken ribs stood in the way of regular procedure. At 20,000 feet, Cardenas released the XS-1.

But the B-29 was flying a little too slowly, and the instant it was free the XS-1 started to stall. It fell more than 500 feet before Yeager managed to get the nose pitched over, forcing air over the wings for lift and regained control. He lit the four rocket chambers of the XS-1’s XLR-11 engine in rapid sequence and accelerated easily to Mach 0.88. The aircraft started to vibrate; flipping on his stabilizer control system smoothed the flight right out. He shut off two of the rocket chambers but kept accelerating past Mach 0.92 and ascending into thinner atmosphere. When he turned his third rocket chamber back he hit Mach 0.96.

A close up of a later X-1′s cockpit; Yeager’s plane, nicknamed Glamorous Glennis for his wife, was moved to the Smithsonian Air and Space Museum after his flight. Note the Machmeter, which has been updated to show speeds up to Mach 1.5. Credit: NASA

Then he reignited his fourth rocket chamber and the XS-1’s Machmeter failed. The needle fluctuated then tipped right off the scale.

After all the anxiety about a pilot’s ability to control an aircraft breaking the sound barrier, the controversy over whether anything even existed beyond Mach 1, Yeager was there. And hadn’t felt a thing. Observers on the ground got the sonic boom as confirmation of the XS-1 supersonic flight, but for Yeager in the cockpit it was a bit of a let down. He’d expected something, a bump or shake in the flight, to tell him he’d gone supersonic. He felt nothing. It was less like breaking through a wall and more like poking through Jello. He didn’t even know how fast he’d gone. His Machmeter stopped at 1 – it was an interesting measure of how little faith the XS-1’s designers had in its ability to fly supersonic.

Underwhelming though it might have felt, the importance of the flight and its impact on aviation were significant. Yeager, who reached Mach 1.06 at 43,000 feet opened the skies. In the decade that followed, pilots pushed later X-aircraft – modified X-1s and its successor the X-2 – to altitudes of 126,000 feet and speeds a shade over Mach 3. Not until the X-15 were these records broken in the 1960s.

The Bell XS-1. Credit: NASA

Suggested Reading:

Chuck Yeager and Leo Janis, Yeager. Bantam Books. 1985.

Comments

  1. Markus says

    It should be noted that unlike what tends to be “common knowledge”, Yeager was not the first pilot to break the sound barrier. That mark belongs to the F-86, probably flown by George Welch, albeit it’s considered “unofficial” for various reasons – for one, it took taking the plane into a dive to go supersonic. Nevertheless, supersonic booms were heard by locals significantly before Yeager’s flight. Commemorative plaques (in museums, etc.) have been quietly altered some years ago to reflect that, now reading “first to achieve Mach 1 in level flight” or variations thereof.
    Similarly, unlike what press releases like to claim, Felix Baumgartner will not be the first man to go supersonic in free fall. For all intents and purposes, Joe Kittinger did in fact break the sound barrier too.

  2. mithril says

    according to his autobiography, Yeager broke 2 ribs before the historic fight. he and the flight crew hid the fact from the higher ups so he wouldn’t get bumped from the mission, the injury didn’t prevent him from flying the craft itself, but he had to learn how to use a length of broom handle to close the hatch since he couldn’t turn in his seat to do it.

    there was also the fact that the fuel they carried was highly sensitive. if the X-1 had too much left in its tanks when it landed, it would have blown up.

  3. David Shomper says

    “…he’d broken a rib the night before…”

    “…he’d broken two ribs the day before…”

    So which is it?

  4. Mark R. says

    @ Markus: as impressive as Kittinger’s highest jump was, he does not claim to have gone supersonic, and the records show that he achieved Mach 9. Of course many pilots dove faster than the speed of sound before Yeager (I’d be surprised if Welch was the first to live through that), but achieving sustained, controlled level flight in the transonic/supersonic range was the goal at the time.

  5. justin says

    nice! I’m just finishing up Tom Wofle’s “The Right Stuff” and I thoroughly enjoyed the stories about the drawlin’ hot shot Yeager

  6. Markus says

    @Mark R:: The goal at that moment was to “break the sound barrier” for the first time, plain and simple. And that’s what, to this day, Yeager is being remembered for first and foremost. That’s the historic record. And it simply isn’t correct. The team at the time was considerably miffed that they apparently had been beaten by another team that wasn’t even using a specifically designed experimental airplane, while in turn getting mocked (unfairly, I’d say) for the fact that the X-1 wasn’t as much a “real plane” because it had no jet engine and had to be dropped from a carrier plane for its flight. (Subsequent supersonic flights with advanced X-1 versions were done, in part, specifically to prove exactly that point, that it could in fact take off from the ground under its own power and then go supersonic.)

    Kittinger indeed doesn’t claim to have gone supersonic. Breaking that particular speed record wasn’t the mark he tried to achieve anyway (altitude was), and I’m not sure if they even measured his velocity. But if you crunch the numbers, like plenty of people have done in the 50+ years since then, it’s pretty clear that he almost certainly did go supersonic for a short while. I mean, that isn’t exactly news.

    • mithril says

      to be honest, i think the Bell X-1 and Yeager deserve the fame they got because of flight plan. the F-86 exceeded mach 1 in a very steep dive, while the Bell X-1 did it in level flight. doing it in level flight is the more noteworthy achievement, because it requires more effort. not to mention the fact that the F-86 pulling it off was unintentional, while the Bell X-1 flight set out with that as its goal.

      doesn’t change the reality of the timing, but i think nitpicking about who did it first detracts from the praise Yeager and the X-1 crew deserve for pulling off their goal.

Trackbacks

  1. [...] During Baumgartner’s more-than-two-hour-long ascent to jump altitude, Red Bull could have told Kittinger’s story. The announcer could have talked about the technology keeping Baumgartner alive, what made his suit different or special, told us how he was able to break the sound barrier in a free fall, talked about problems like aerodynamic heating in atmospheric entry. Instead, RedBull held an audience captive and offered them almost nothing but shots of Baumgartner in a suit and Kittinger at the capcom console. Even when the announcer talked about the possibility of Baumgarner entering a spin during his fall, he failed to mention the parallel that Kittinger had proved the graduated parachute system that stabilized a pilot’s fall. He didn’t even mention that Baumgartner’s supersonic jump came on the 65th anniversary of Chuck Yeager’s first supersonic flight. [...]

  2. [...] And while I thought the event showed the power of streaming an event solely online, others thought the mission was more or less, a flop.  Discover Magazine said the publicity stunt wasted a huge opportunity by not teaching any historic context to its estimated eight million person audience on YouTube. Freelance space writer Amy Shira Teitel also believed that the project didn’t “transcend human limits” like the project advertised. Teitel argues that technology was what kept Baumgartner alive during his jump, not his human limits. In addition, she pointed out that during the nearly two-hour ascent Red Bull failed to do anything besides shots of Baumgartner on the way up and failed to talk about how the jump was happening on the 65th anniversary of the first human breaking the sound barrier. [...]

  3. […] In 1945, the US Army Air Force and the National Advisory Committee for Aeronautics contracted the Bell Aircraft Company to build an experimental supersonic aircraft. Taking its designation from its “experimental supersonic” description, the XS-1 – later renamed the X-1 – took to the air in 1946. A year later, Chuck Yeager flew the aircraft on the history’s first level supersonic flight. […]

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