For more than 22 years, astronauts and cosmonauts have continuously inhabited the International Space Station, making the orbital laboratory the longest flying spacecraft ever. But it’s an achievement that would be impossible if not for an earlier space station, NASA’s Skylab, launched 50 years ago on May 14, 1973.
Born out of the disappointment and leftovers over the canceled Apollo moon missions, Skylab never captured the public imagination the way the space race had during the decade prior. But the mission was crucial to all human spaceflight that came after, teaching NASA valuable lessons about how to build spacecraft safe for long-term habitation, and how to design missions around the humans that would fly them.
“Every corner of the ISS has a lesson that’s grounded in Skylab,” says NASA’s Chief Historian Brian Odom. “Skylab is the turning point where humanity says, ‘We’re going to become a species that lives off of Earth for long periods of time.”
Moonshots and space stations
NASA had always wanted a space station. The plan, according to Odom, was to learn to get off Earth with Project Mercury—in which Alan Shepard became the first American to fly in space—then to rendezvous and dock in orbit with Gemini, and “the next stop from that would be to build a space station,” he says. That space station would be the waypoint from which humans could venture farther out to the moon, and later to Mars.
But everything changed with President John F. Kennedy’s 1961 speech announcing a race against the Soviet Union to land on the moon.
“Some people talk about Apollo as leapfrogging what was expected, as the natural process or the natural progression in spaceflight,” says Teasel Muir-Harmony, a space historian curator of the Apollo collection at the National Air and Space Museum. “Instead of building a space station, we went right to the moon.”
Immense amounts of money and political capital were spent so Americans got to the moon first. But public support—and congressional funding—began to wane almost immediately after the July 20, 1969, Moon landing. Apollo missions 18, 19 and 20 were canceled by 1971, and the crew of Apollo 17 would be the last humans to touch the moon for decades to come.
The idea for Skylab originated in 1965, when NASA budgets were plump. The agency decided the program could go forward even after money tightened up, in part because the satellite would use existing Apollo infrastructure. A Saturn V rocket, originally intended to launch the Apollo 12 mission, could place Skylab in orbit. And the space station itself would be constructed out of a rocket’s third stage.
“It was a really ingenious and practical approach to creating a space station,” Muir-Harmony says.
[Related: A brief history of space stations before the ISS]
The architecture of Skylab wasn’t the only creative use of materials. During the May 14 launch, Skylab’s micrometeorite shield, which also functioned as a sun shade, was shorn off, leaving the newly orbital space station to roast in the direct sunlight. NASA’s “Mr. Fix It,” Jack Kinzler, officially the chief of the Technical Services Center at Johnson Space Center, used telescoping fishing rods to develop a prototype parasol-like sunshield astronauts could deploy through an airlock on Skylab. They did this in just six days, saving the space station. It was one of the first important lessons of Skylab, according to Odom.
“It’s one of these remarkable moments that teaches us that you can respond in a crisis” Odom says.
The lessons of Skylab
Skylab hosted three crews from 1973 through 1974. The Skylab I crew flew for 28 days, while the Skylab II mission lasted 59 days.
But Skylab 3, the third and final crew to fly aboard the space station, lasted 84 days, launching on November 16, 1973 and returning to Earth on February 8, 1974.
This was a huge deal at the time. Later NASA astronauts, such as Scott Kelly and Peggy Whitson, would work for hundreds of days aboard the ISS, but in 1973, no one knew if humans could actually live in space for such a period. The Skylab III crew’s stay was longer “than all of earlier spaceflight combined,” Odom says.
Skylab affirmatively answered the question of whether humans could endure long-term spaceflight, but it also made clear there were costs.
“They noticed increased calcium in the urine of the astronauts, tied to bone loss,” Muir-Harmony says, which highlighted the importance of movement while in space. Exercise is now considered a key part of an ISS astronaut’s schedule.
Skylab also identified small quality-of-life changes that could make orbit more comfortable, such as the cuisine. “The food was generally considered a bit too bland,” Muir-Harmony says. “Your ability to taste is limited by how the fluid in your body blocks your nasal cavity [in microgravity], so it’s important to have more flavorful food in space.”
And Skylab’s supposedly water-tight microgravity shower, a cylindrical tent-like contraption, will likely be the last shower on a space station, according to Muir-Harmony. “It didn’t work all that well,” she says. “That was an important lesson to learn, that it was better to use wet wipes as opposed to trying to shower in space.”
Another lasting lesson was that all the clever engineering in the world won’t help you if you don’t pay attention to your crew’s human needs. The Skylab III crew nearly burned out, with barely any time between tasks or to rest, forcing NASA to reassess their work schedule. “You can’t task people with just working themselves full on and then falling asleep, sleeping eight hours, waking up, and immediately going back to work,” Odom says. “They learned those lessons the hard way on Skylab by putting people to some degree through the wringer.”
[Related: 11 of NASA’s most out-of-this-world illustrations]
Skylab’s final teaching might be the most important for anyone operating in space today, particularly as the number of satellites and other spacecraft in low Earth orbit increase. Unlike the ISS, Skylab was not equipped with thrusters. It could not manage its own altitude, because it was assumed that the Space Shuttle would be operational by 1977 and could boost the station higher when necessary. But the development program dragged, and the first shuttle didn’t fly until 1981. With Skylab’s orbit degrading, NASA decided to allow the station to reenter Earth’s atmosphere on July 11, 1979, hoping the station would burn up over the Indian Ocean. Pieces of debris ended up scattered over parts of Western Australia, though no one was hurt.
The NASA of today would consider such a reentry reckless. It’s a problem, Odom says, if you don’t know exactly where your spacecraft is going to come down. “NASA has definitely learned that lesson from 1979, in a big way.”
Skylab’s enduring legacy
Without regular rides to space, Skylab crews had only what they brought with them. Astronauts flying aboard the ISS today face fewer constraints than Skylab crews did. The ISS recycles most of its water, for instance, and regular cargo resupply missions deliver food to the astronauts there. There are now exercise facilities and more thoughtfully planned out work schedules.
“Skylab was just a massive step forward from what anyone had experienced before,” Odom says. “Somebody’s got to be the pioneer and put the risk on. And Skylab was all about risk.”
The ISS has hosted astronauts for more than 350 days at a time—a remarkable achievement, and one that would not be possible without Skylab’s experience.
