How an early launch delay impacted the race to space

NASA’s little known unmanned MR-BD mission had a big impact on the early Space Race.

Alan B. Shepard Jr
Due to a delay, US astronaut Alan Shepard was supplanted by Yuri Gagarin to be the first human in space [AP]

We’ve just passed one of the seldom recognized but really interesting anniversaries in the history of spaceflight. At 12:30 in the morning on March 24, 1961, an unmanned Redstone rocket launched from NASA’s Cape Canaveral Air Force Station in Florida. The eight and a half minute suborbital flight reached a peak of 113.5 miles (183km) before splashing down in the Atlantic Ocean. The mission was labelled “fully successful”, but for Alan Shepard it was a bitter disappointment. He was supposed to be on that rocket.

Men and monkeys

In the early days of the Mercury programme, NASA was still figuring out the details of the dangerous and difficult business of spaceflight. No one was entirely sure men could withstand the increased g-forces during launch or the disorienting effects of weightlessness. So the agency practiced with chimps. If a trained chimp could survive a Mercury launch and perform simple tasks during the flight, so could an astronaut.

NASA’s most famous chimp is probably Ham, the first primate to ever ride a man-rated rocket who was named for the Holloman Aerospace Medical Centre where he was trained. Ham’s flight was simple, a duplicate of the suborbital flight on which NASA was at the time planning to send all seven of its Mercury astronauts. Nestled inside a specially designed cabin that was loaded into a modified Mercury capsule, Ham’s flight plan had him launching on a Redstone rocket to a peak height of about 115 miles (185km) before falling to a splashdown in the Atlantic Ocean. Trained to pull levers, his in-flight task was to pull the lever that corresponded with a light. The correct lever gave him a banana pellet and a sip of water; the wrong lever gave him a shock to the soles of his feet.

Ham the Chimp takes flight

As Ham lifted off the launch pad on January 31, 1961, everyone was confident in the mission. Everyone except the Redstone rocket’s engineers, led by Wernher von Braun. The Redstone was plagued by what they called a hot engine; the Rocketdyne built engine had a nasty tendency to burn through its available fuel very fast. This had a serious impact on the launch abort system, the cluster of rockets designed to pull a capsule away from an exploding rocket. The abort system had to be disarmed by the time the engine shut down or the sudden loss of thrust would trigger the system’s rockets to fire, subjecting the capsule’s occupant to a painful sudden acceleration for nothing.

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For Ham’s flight, von Braun timed the launch abort system to shutdown 137 seconds after launch, two seconds before he anticipated the Redstone’s engine would run out of fuel. Unfortunately, he’d underestimated his rocket. Ham’s Redstone devoured its fuel in just 134.5 seconds, which triggered the abort system and sent the unsuspecting chimp rocketing to an altitude of 157 miles (253km) before splashing down 50 miles (80km) off target. When recovery crews reached the landing point, Ham was was irate, trying to bite every hand that came near him. Not only had the ride been rough, an electrical malfunction meant every level he pulled, right or wrong, gave him a shock to the feet.

But Ham had survived, and that’s what mattered. Particularly for Al Shepard, who had been assigned the first flight after a peer vote earlier that month. Reading the data from Ham’s flight, what he called the Great Chimp Adventure, Shepard saw that a similar malfunction on his flight would be uncomfortable but survivable. He saw no reason not to ride the next Redstone into history. But von Braun felt differently; specifically, he was uncomfortable sending a man on an imperfect rocket. He ordered a number of engineering changes to fix the hot engine and asked for one more unmanned launch. Unfortunately for Shepard, von Braun won.

The last unmanned flight of a Redstone was the mission that launched on March 24. At the insistence of Flight Director Chris Kraft, it was labelled MR-BD, for Mercury Redstone Booster Development; NASA’s official record will forever emphasise the mission as a test of the rocket, and not of the capsule or the man. Responsibility for delaying Shepard’s flight by more than a month – he finally flew on May 5, 1961 – rested firmly on von Braun’s shoulders.


It’s hard to call the MR-BD mission decision the point when NASA ceded to the Soviets in the first wave of the Space Race, particularly without being labelled a revisionist historian, but it is an interesting case.

In March of 1961, the Soviets launched two unmanned missions, Korabl-Sputnik 4 on March 9 and Korabl-Sputnik 5 on March 25. Both carried the dummy Ivan Ivanovich and a host of animals including dogs, mice, and guinea pigs into orbit on missions that tested the full Vostok flight system. Particularly important were tests of the communications system and tracking network without which they couldn’t hope to have a manned flight.

That Korabl-Sputnik 5 launched the day after MR-BD suggests that the Soviets weren’t quite ready to beat their American counterparts to a manned mission in March. But that’s not the full story. These Korabl-Sputnik missions were launched without previous all-up testing on the ground, suggesting the engineers were rushing to get a man up before the Americans. It’s likely that when NASA announced it would run one more unmanned test after Ham’s January flight, pushing the first manned flight to late April or early May, Soviet Chief Designer Sergei Korolev saw a window and exploited it. The brilliant engineer behind the Sputnik and Vostok missions had a long standing rivalry with von Braun and made no secret of his hope to beat the German into orbit. With an American launch delay, Korolev had time not only to launch his manned mission first, but to run necessary unmanned tests without fear of losing ground.

While it may not have been a linchpin mission, the story behind NASA’s MR-BD flight is one of the more interesting ones we ignore. The decision to delay Shepard’s flight certainly gave the Soviet space engineers the buffer they needed to stick to their own schedule and make Yuri Gagarin history’s first man in space. 

Amy Shira Teitel has an academic background in the history of science and now works as a freelance science writer specialising in spaceflight history. She maintains her own blog, Vintage Space, and contributes regularly to Discovery News, Scientific American, Motherboard, DVICE.

Follow her on Twitter: @astVintageSpace