On June 5, 1966—fifty-five years ago—Eugene Cernan became the third person to walk in space. His spacewalk took place a year and two days after fellow astronaut Ed White had gone outside the spacecraft on Gemini IV for the first American spacewalk. (Soviet cosmonaut Alexei Leonov was the first to do so, in March 1965.) Those earlier forays had made extravehicular activity (EVA), as NASA called it, look easy, at least on the surface. But Cernan’s spacewalk was nearly disastrous, appropriate for a mission plagued by bad luck.

Cernan flew on Gemini IX-A with Tom Stafford as his commander, part of a series of short missions with the two-astronaut Gemini spacecraft in 1966. These flights aimed to develop experience in EVAs and in rendezvous and docking, techniques needed if the U.S. was going to land on the Moon by the end of the decade. But Stafford and Cernan had not been the original crew of what was first called Gemini IX. (NASA used Roman numerals for missions from IV on.) In January, the space agency named Elliott See and Charles Bassett the prime crew, with Stafford and Cernan as backups.

Tragically, See and Bassett were killed in their T-38 on February 28, 1966, when they clipped a building at the McDonnell Aircraft plant outside St. Louis, Missouri, in rain and fog. They were on a trip to inspect the spacecraft at its manufacturer, McDonnell, and were landing at the adjacent city airport. Stafford and Cernan, flying in another T-38, arrived safely. Stafford, who had just flown on Gemini VI-A in mid-December of 1965, and been part of the first space rendezvous in history. He found himself suddenly, but not happily, in line to go up again in May.

The mission of Gemini IX was a lot like that of VIII, docking with an Agena rocket stage and a spacewalk to test new equipment. Sixteen days after the See and Bassett crash, Neil Armstrong and Dave Scott carried out the first docking in history on Gemini VIII, but the two made an emergency splashdown after a stuck thruster threw them into a near-fatal spin. The fact that Scott did not do his EVA would contribute to Cernan’s difficulties on the next attempt.

On May 17, 1966, Stafford and Cernan sat in the spacecraft atop their Titan II booster waiting for launch. Just as had happened to Stafford the previous October, they never got off the ground because the separately-launched Agena blew up on the way to orbit. Like Gemini VI, NASA gave Gemini IX an alternate target vehicle and attached an “A” to its number. This time, NASA’s contractors prepared a substitute called the Augmented Target Docking Adapter (ATDA), a kluge of Gemini and Agena parts half the length of Agena, with no main propulsion system. It could be thrown into orbit with an Atlas missile alone. On June 1, 1966, it was, but as the ATDA passed over Florida after one orbit, Stafford and Cernan were stuck on the ground again. For no obvious reason, ground computers lost contact with the spacecraft three minutes before launch. After five trips to the Gemini-Titan complex and only one successful launch, someone gave Stafford the nickname “mayor of pad 19.”

Finally, on June 3, 1966, he and Cernan made it into space. They immediately set about rendezvousing with the ATDA. Telemetry had signaled that the white conical shroud that covered its docking cone at the tip of the rocket may not have jettisoned successfully. Indeed, as the Gemini IX-A crew pulled up to the ATDA a few hours later, they found the shroud still attached and partially open, as the vehicle slowly rolled, unable to maintain a stable attitude. The thing looked, in Stafford’s words, like an “angry alligator.” Docking was impossible.

I’ve never forgotten the headline that ran the next day in the Calgary Herald, my hometown newspaper: “Gemini 9—Thy Name is Jinx!” That day, Stafford and Cernan carried out rendezvousing and stationkeeping exercises with the ATDA in order to gain more flight experience in techniques important to Apollo. Tired and not wanting to waste thruster propellant stationkeeping with the ATDA during Cernan’s scheduled EVA, Stafford told Mission Control that he wanted to put it off to the last day of the mission.

Gene Cernan’s planned EVA was highly ambitious, especially in view of zero spacewalking experience since Ed White’s twenty minutes. The primary task was to move to the back of the Gemini adapter section and strap into the Astronaut Maneuvering Unit (AMU), a U.S. Air Force backpack with control rockets fueled by hydrogen peroxide. Because the resulting jets were hot, Cernan’s spacesuit had metal “pants,” an extra cover layer of woven steel on its lower half. He was to connect up to the AMU, disconnect his oxygen line from the spacecraft, and attached only by a tether, fly around the Gemini.

As soon as Stafford and Cernan depressurized the spacecraft and opened the hatch above Cernan’s head, he immediately discovered how difficult it was to move. His pressure suit was hard as rock in the space vacuum and his lower half was almost immobilized by the metallic “pants.” In his memoirs he described his spacesuit as having “all the flexibility of a rusty suit of armor." Tasked with evaluating the dynamics of moving around with the umbilical that carried his oxygen and communications, he was already becoming exhausted and sweaty — the circulation of oxygen around the head and body was the only cooling mechanism in the Gemini suit. He then moved to the back of the spacecraft and tried to don the AMU. Fighting the suit and lacking proper handholds and footholds, Cernan found the task nearly impossible.

Finally, he made all the required connections, but he was sweating so profusely his visor fogged over. He could only use the tip of his nose to rub out a small zone of visibility. His heart began racing dangerously. Rather than letting him fly the AMU, Stafford ordered him to quit. Almost blind, Cernan slowly dragged himself back to the cockpit, where getting in and closing the hatch proved to be another nightmare. He was “in excruciating pain” as he bent the suit to sit down, assisted by Stafford. After a difficult struggle, they closed the hatch and repressurized after being out for two hours. When Cernan popped open his visor, he looked as red as a boiled lobster. Stafford took the water gun for drinking and rehydrating food packages and squirted him in the face, even though globules of water floated around the cockpit and could short out electronics. Before the flight, chief astronaut Deke Slayton had talked with Stafford about throwing overboard an incapacitated or dying Cernan in an emergency. Stafford later said he wouldn’t have done it, but he would have had no choice.

The next day, after they splashed down in the Atlantic, ship surgeons found Cernan had lost 13 pounds, almost all of it water. Stafford claims there was over a pound of sweat in each of his partner’s boots. Questions swirled about the nearly disastrous EVA. Was it bad procedures or equipment, or had Cernan just failed as an astronaut? The crisis forced the NASA Manned Spacecraft Center in Houston (now Johnson Space Center) to reevaluate its training methods. Underwater EVA experiments being done by a small contractor in a school pool outside Baltimore suddenly looked a lot more interesting. In July 1966, Cernan went there and simulated his walk. He found the result was essentially the same, which was a big relief — he was not at fault for what happened. By August of 1966, Houston committed to building its own pool and learned the lesson that, in weightlessness, without proper handholds and footholds, the astronaut would thrash around and quickly become overheated. Those lessons came too late for the troubled spacewalks on Geminis X and XI, but on XII in November, Buzz Aldrin demonstrated that, with carefully paced tasks and handholds and footholds, it was possible to do work in space. Apollo suits would also incorporate a liquid cooling garment, body-hugging underwear circulating water through small tubes, carrying away heat.

Cernan’s terrible experience thus became an important step on the way to the Moon. He would fly with Stafford again on Apollo 10, accompanied by John Young. They carried out a dress rehearsal in lunar orbit of the entire landing and takeoff sequence. Cernan would become one of only three astronauts to go to the Moon twice. As commander of Apollo 17, he would explore the surface for three days with Harrison “Jack” Schmitt. Cernan became the last human to walk there—so far.

Michael J. Neufeld is a senior curator in the Museum’s Space History Department and is responsible for Mercury and Gemini spacecraft, among other collections.