/ NASA In this image taken from NASA video Italian astronaut Luca Parmitano (lower right) holds a bundle of new pumps for the Alpha Magnetic Spectrometer outside the International Space Station on Dec. 2, 2019. One of the paradoxes of spacewalking is that, although space is cold, the lack of atmosphere around the suit can actually cause heat to build up inside. As Cernan struggled to move, he ended up overexerting himself. “He started to sweat profusely and the moisture in the suit started to fog his vizor,” Margolis says. With his visibility severely impaired, his crewmate cut the EVA short and brought him back inside. When Cernan returned to Earth, Margolis says, it was determined he’d lost 13 pounds over the mission. “It’s believed that most of that was water weight from the amount that he was sweating during this EVA,” she says. Spacewalks have become more routine since then, but they remain risky, according to Jonathan Clark, a physician at Baylor College of Medicine who has consulted for both NASA and SpaceX on spacesuits. By his count, around one in five spacewalks encounter some sort of problem. “Sometimes you can adapt to it, but a lot of times you’ve got to stop the EVA and come back in,” he says. In the case of Luca Parmitano, the astronaut whose helmet began filling with water, he had little choice but to cut the spacewalk short. Because he couldn’t see, he had to work his way back to the airlock from memory. Eventually fellow spacewalker Chris Cassidy helped him get back inside and close the hatch. “I don’t take any specific credit for keeping my cool because I’d been trained my whole adult life to perform in relatively risky situations,” says Parmitano, who is also a colonel and test pilot in the Italian Air Force. New challenges Clark notes that the Polaris Dawn crew has had far less experience. Of the four crewmembers, only Isaacman has actually been to space. Beyond that, “none of the crew has done an actual spacewalk before,” he says. “It’s going to be a first for everybody.” The crew will be wearing new SpaceX suits that in some ways resemble those worn by earlier generations of astronauts. They will be fed oxygen by an umbilical cord connected to the spacecraft, and the suits themselves will be passively cooled with air from the umbilical. That means there’s no chance of a water leak, like what happened to Parmitano, but overheating similar to the Gemini missions could become an issue, as could fogging of the astronaut’s visors. Moreover, the Dragon Capsule itself will have to continue to operate smoothly under vacuum. Without air circulating, the capsule’s onboard computers will have a harder time keeping cool. “The challenges are certainly there,” Clark says. But newbies can do tough things in space. Sian Proctor was the pilot of Isaacman’s first mission to orbit the earth in 2021. Until six months before launch, she’d never flown a rocket. “I basically went from being a geoscience professor to being a mission pilot of a spacecraft,” she says. Proctor says SpaceX got her ready. In fact, Sarah Gillis helped train her for her mission. Another member of this latest crew, Scott Poteet, was the mission director for her launch. While Proctor’s brief flight took only six months to prepare for, this latest mission has been in the works for more than two years, allowing for much more training. Proctor says, If anyone can carry out the first commercial spacewalk, it’s this team. “The crew is amazing,” she says. “They are so competent at what they do.” Copyright 2024 NPR