Scott Carpenter wasn’t supposed to be the second American to orbit the Earth. Donald “Deke” Slayton was originally scheduled for the second orbital mission, but was grounded when doctors discovered a heart irregularity. Slayton would be the only one of the Mercury 7 to not fly a mission, though he remained with NASA for more than 30 years and finally made his one, long-delayed space flight at the age of 51, when a medical clearance allowed him to take part in the 1975 Apollo-Soyuz Project.
Carpenter took Slayton’s spot in the rotation, becoming the sixth American in space on May 24, 1962, just three months after Glenn’s flight. Riding aboard the Aurora 7 capsule (the astronauts were allowed to choose their spacecraft’s call signs, though all of them included “7” to honor the number of pilots in the program), Carpenter orbited the Earth three times during the nearly 5-hour mission, which did not go smoothly. Unlike earlier Mercury flights, which had adhered to NASA’s strict flight protocols, Carpenter quickly fell behind in completing the long list of scientific tests he was tasked with and reportedly wasted valuable time (and fuel) repeatedly rotating the capsule to get a better view of his space environment and Earth in the far distance. (Part of this constant direction shift was a necessary adjustment on Carpenter’s part, as the capsule’s attitudinal equipment malfunctioned near the end of the flight.)
The mission was further complicated as Carpenter prepared for reentry, when his three-second delay in firing his rocket boosters (combined with the equipment malfunction) resulted in his overshooting his landing spot by more than 225 nautical miles. With NASA uncertain of his exact location and the standard radio blackout lasting longer than anticipated, Carpenter’s Mercury mission—which NASA had hoped would be glitch-free—was suddenly imperiled, with space officials and the television viewing audience anxiously awaiting word of his fate. It took nearly an hour for search planes to locate him and his life raft in the Caribbean. NASA may have been nervously sweating things out, but the ultra-fit, calm Carpenter apparently was not—despite the series of glitches, the astronaut’s vital signs remained remarkably stable. It would, however, be his one and only flight. Mercury flight commander Chris Kraft, who had previously expressed his concern over Carpenter’s behavior during pre-flight training and was angered over his failure to follow directions once in space, effectively grounded him. In later years, however, NASA inquiries and additional research has laid the blame for most of the mishaps in the Aurora 7’s flight on technical malfunctions, not human error.
While Carpenter was best known for his work in space, he considered his time as an experimental underwater researcher, or aquanaut, to be of equal importance. In 1963, he took a leave of absence from NASA to work on the nascent SeaLab project, developed by the U.S. Navy to study the viability of sustained underwater diving and possibly develop training exercises for future astronauts. A serious motorcycle accident in 1964 prevented him from joining the first SeaLab expedition (and led to his resignation from NASA three years later), but Carpenter was part of the second mission, launched in August 1965. The 50-foot-long by 12-foot wide vessel was lowered 200 feet below sea level off the coast of La Jolla, California, garnering the nickname “Tilton Hilton,” due to the steep angle of landing site the vessel was cradled in. Three teams of divers rotated in and out of the capsule for stays of up to 15 day, but Carpenter remained aboard for 30 days, setting a new world record for underwater diving.
While on SeaLab, Carpenter took part in two unique phone calls, sending good wishes to fellow Mercury astronaut Gordon Cooper as he circled the Earth high above in Gemini 5, and receiving his own congratulatory call from President Lyndon Johnson after his record-setting underwater feat. This second phone call, however, did not go as planned. Carpenter was in the middle of an extensive decompression program, which included a stint in a chamber filled with helium (rather than bends-inducing nitrogen), giving Carpenter an almost unintelligibly high-pitched speaking voice during the call.
Carpenter continued his nautical work after retiring from the U.S. Navy in 1969, founding a series of underwater research companies, writing two aquatic-themed novels and an autobiography, and deep-diving the world’s oceans with friend Jacques Cousteau. It was another longtime friend that brought him back to NASA in October 1998, when John Glenn returned to space aboard the shuttle Discovery. Reprising his iconic phrase from 36 years earlier, Carpenter ushered Glenn into orbit with a simple wish of good luck, and Godspeed. When news of Carpenter’s death broke this week, the now 92-year-old Glenn returned the favor, issuing a statement that read, in part, “Godspeed, Scott Carpenter…You are missed.”