‘Worth Waiting 16 Years For’: Remembering Deke Slayton’s Unrealized Mercury Mission (Part 2)

Savoring his first experience of weightlessness, Deke Slayton traverses through the Docking Module during his one and only space mission. Photo Credit: NASA

By the middle of March 1962, Donald “Deke” Slayton—decorated U.S. Air Force fighter pilot and test pilot and veteran of the grueling Project Mercury selection campaign, during which he had proven himself as a perfect specimen for astronaut training—was dealt perhaps the most devastating card of his career. With just eight weeks to go before he was due to ride an Atlas booster to become the United States’ fourth astronaut and its second man to orbit the Earth, Slayton was grounded by a minor, yet persistent heart murmur. As outlined in yesterday’s AmericaSpace history article, his condition had been detected in summer 1959, but had not been considered serious and had lain dormant for almost three years.

All that changed in the spring of 1962, when speculation arose that Slayton’s fellow Mercury astronaut John Glenn might have a heart condition. Although this was proven to be untrue, a metaphorical can of worms was opened and NASA revealed that Slayton—who was by this point deep into training for a five-hour and three-orbit mission, dubbed “Delta 7”—suffered from a condition known as “idiopathic atrial fibrillation”. Every so often, irregularities were detectable in a muscle at the top of his heart. “I realized that every couple of weeks, I would go through a period of a day or two when when my pulse would act up,” Slayton wrote in his memoir, Deke. “I had no other symptoms. It certainly didn’t stop me from working. And I found that if I did some heavy exercise, like running a couple of miles, the thing just went away.”

Unfortunately, in a whirlwind couple of days, from 13 through 15 March, Slayton was poked and prodded by military and civilian doctors…and told, point-blank, that he was grounded. Next day, Slayton was forced to sit through a press conference, where the minutiae of the incident were played out in depth. “It was awful the way it happened,” wrote Project Mercury Operations Director Walt Williams, years later. “I don’t remember Deke being angry, as much as he was hurt—partly for the way it was handled.”

John Young, Gus Grissom and Tom Stafford, together with Deke Slayton (second from left) study orbital-track charts before the launch of Gemini 3 in March 1965. Photo Credit: NASA

Indeed, Slayton had committed months of training to the flight, which he had dubbed “Delta 7”. The name created a link between the fourth letter of the Greek alphabet with the fourth U.S. manned space mission and the numeral paid tribute to NASA’s “Original Seven” Mercury astronauts, of whom Slayton was one. By his own admission, though, Slayton had preferred his flight to focus on engineering objectives, with lesser emphasis on science. “There was a hell of a lot we still hadn’t demonstrated with Mercury,” he wrote Deke, “such as a reliable flight control system.”

In Slayton’s mind, science should take a figurative backseat to the engineering realities of a new spacecraft in a unknown and hostile environment. However, the success of John Glenn’s Friendship 7 mission in February 1962—during which he became the first American citizen to orbit the globe—caused the scientific community to increase their focus on science for Slayton’s flight in May. “Everybody and his brother came out of the woodwork with some experiment,” Slayton wrote. “One guy wanted me to release a balloon to measure air drag. Another guy had some ground observations I was supposed to make. One damn thing after another. I had my hands full trying to resist it.”

Effectively grounded from spaceflight in March 1962, Slayton found himself heading up the astronaut corps from the summer of that year as “Co-ordinator of Astronaut Activities”. A lesser man might have thrown in the towl, but not Slayton. The other astronauts loathed the idea of an outside manager or a military superior to serve as their boss. “We wanted someone who knew us,” wrote Wally Schirra in his memoir, Schirra’s Space, “who trained with us. Deke was the one and only choice.”

In this position, he became a virtual father figure to many of them. He was a man labeled “the best” by Mike Collins and described as a dependable colleague who could be trusted “to get the job done, no matter what the job was” by John Glenn. In the words of a Los Angeles Times reviewer—writing on the flyleaf of Slayton’s autobiography—it was indeed “one of the great fortunes of Apollo that [he] was grounded…for in “Father Slayton”, NASA had the man who could set the rotations, pick the teams and make the decisions the astronauts wouldn’t have accepted from a bureaucrat or a scientist.”

Even in the early 1970s, Slayton’s chances of ever regaining a pilot’s licence, let alone securing the opportunity to ride a rocket, seemed infinitesimally small. Then, one day in the summer of 1970, during an antelope hunt in Wyoming, Slayton experienced his first heart fibrillation in several months; he had not suffered one ever since flight surgeon Dr. Chuck Berry loaded him up on vitamins following a cold. As a personal experiment, he started taking the vitamins again and the fibrillations went away.

“It wasn’t the kind of thing you could use as hard medical evidence,” Slayton wrote in his memoir, “but it got me thinking that I might still have a more realistic chance.” More than a year later, Berry happened to attend a medical conference in Istanbul and broached Slayton’s case with Dr. Hal Mankin, a specialist who agreed to run tests. In December 1971, Slayton flew to Rochester, Minn., and checked into the Mayo Clinic under the false name of “Dick K. King.” Whilst there, Mankin put him through a battery of tests, hanging him upside down on a treadmill, poking holes in him, pumping dye into his system, and examining “parts of my body I didn’t even know I had.”

Deke Slayton works inside a mockup of the Apollo Docking Module (DM) in September 1974. Photo Credit: NASA

At last, an angiogram yielded the final judgement. “Your man,” Mankin told Berry, “is as good as gold!” Slayton had passed with flying colors, requalified for a Class I pilot’s licence, and in March 1972— now aged 48 and a full decade after being grounded from Project Mercury—he was restored to active astronaut status.

His problem now was getting a flight, and the list of options was short. Two more lunar landing missions were scheduled for April and December, both of whose crews had already been immersed in training for several months. So too had the crews for three flights to the Skylab space station in 1973. For Slayton, the Apollo-Soyuz venture with the Soviets was his last chance. As head of flight crew operations, it was nominally Slayton who oversaw the astronaut selection process, but since he now considered himself a candidate, he asked Dr. Chris Kraft—then-head of the Manned Spacecraft Center (MSC), later the Johnson Space Center (JSC) in Houston, Texas—to handle the assignment on his behalf.

Despite having never flown in space, Slayton was convinced that his seniority would be more than enough to carry him through and recommended himself for command of the mission. For his crewmates, he identified a pair of astronauts whom he held in extreme high regard: Jack Swigert, a veteran of the ill-fated Apollo 13 mission, and Vance Brand, who was at the time training for the backup command of two Skylab flights.

Swigert’s name was quickly removed from consideration and veteran astronaut Tom Stafford entered the story as a real candidate for command. In January 1973, Kraft called Stafford, Brand and Slayton into his office to formally name them as the crew for the U.S. half of the Apollo-Soyuz Test Project (ASTP). Stafford would command the mission, with Brand as Command Module Pilot (CMP) and Slayton in the new role of Docking Module Pilot (DMP).

Slayton’s euphoria at finally receiving a flight assignment after such a long wait was tempered by the disappointing news that Stafford would be in command. He remembered that the bittersweet news was “a little deflating”, but understood the reasons behind it. For his part, Stafford remembered that Slayton was eternally gracious in his new role and there was “never a moment’s tension” over the issue of command. “I told him I knew we had a good crew,” Stafford wrote, “and a good mission to fly and that was as close as we got to talking about the issue.”

Yet the fact that on Earth, at least, Slayton remained Stafford’s boss prompted a journalist in Houston to ask the obvious question: How did he feel about taking orders from a deputy?

“I see absolutely no problem with that at all,” Slayton replied. “I think there’s a lot of precedence in the country on this particular subject. Anytime you have a guy flying an airplane in the military service, he’s a second lieutenant and you got the highest general in the Air Force. The commander is the commander, and there’s no doubt in this flight who’s going to be the commander. It’s Tom Stafford. Now, when we’re on the ground, working the other programs and the other problems, then obviously we’ve got a normal and working relationship. But I see absolutely no problems at all and I’m responsible to Tom to be ready to fly this flight and he’s responsible to me to see the crew’s ready to go!”

At this irony, Slayton’s eyes twinkled and the auditorium broke into laughter.

Yet the fear of further medical problems had not disappeared. NASA’s medical staff insisted on a new flight ruling: If Slayton developed a heart fibrillation during the countdown, the clock would be held at T-4 minutes and he would be extracted from the command module. “Chris Kraft was just livid at this idea,” wrote Chuck Berry in Slayton’s autobiography. “He called me and asked me what this was all about—[because] he thought Deke was fully qualified to fly.” The rule was unnecessary, he explained, and even if anything untoward did occur, he was a slow fibrillator and would not be adversely affected.

When Deke Slayton returned to Earth in the second half of July 1975, after a mission he admitted was “worth waiting 16 years for”, he gave Berry a gift of thanks. It was the cardiac monitor from his medical harness in the command module, mounted onto a piece of tracing paper, on which was printed the readout of his heartbeat. The beat was steady, with no fibrillations, throughout the entire nine-day flight…


This is part of a series of history articles, which will appear each weekend, barring any major news stories. Next week’s article will focus on the 35th anniversary of STS-3, a March 1982 mission which saw the shuttle perform its one-and-only landing at White Sands in New Mexico.



Be sure to “LIKE” AmericaSpace on Facebook and follow us on Instagram & Twitter!


  1. Slayton’s legacy will forever be the “father figure” of the astronaut corps and Schirra said it best when stating, “He was one of us.” Great job, Ben!

  2. Slayton’s legacy will forever be the “father figure” of the astronaut corps and Schirra said it best when stating, “He was one of us.” Great job, Ben!

  3. A minor quibble: Slayton’s pilot license would not have been affected by his heart condition. Rather, his pilot’s MEDICAL would have been. The “Class I” license referenced in the text is a medical certification, not actually a license to pilot aircraft. Those are separate certifications, although only recently the FAA has been revamping some of those rules.

    Being medically unfit to fly would effectively ground a pilot who disclosed such a condition (which is required), but it would not negate holding a pilot license. With the exception of flight instructor licenses, all pilot licenses are permanent, irrespective of medical status.

Pad 39A Ready for First Night-Time Launch in Seven Years, With Heavyweight EchoStar-23 Mission

Venus Beckons Part 2: A New NASA Collaborative Mission With Russia?