NASA had a problem 250 miles above Earth. Two astronauts, Luca Parmitano and Chris Cassidy, were crawling along the outside of the International Space Station, performing routine maintenance in 2013, when Parmitano noticed liquid accumulating in his helmet.
“It feels like a lot of water,” the Italian astronaut reported over the radio—a worrisome development because in microgravity, the water could float in front of his face and possibly drown him. Though he didn’t know it, Parmitano’s space suit had a blockage in a system that circulates water for cooling, spilling it into a ventilation system connected to his helmet.
“As the sun went down, the water reached over my eyes, and over my ears, and over my nose, effectively blinding me in the dark,” Parmitano recalls.
Breathing through his mouth, Parmitano fumbled along the handholds outside the space station, pulling against his safety tether to feel his way back. The water covered his microphone, cutting off his ability to speak to Houston or Cassidy. When he reached the airlock, the crew got him inside, quickly pulled off his helmet, and soaked up the water with towels.
“It took me about seven minutes to navigate back,” Parmitano says, “and even though seven minutes may not seem like a long time, it felt like a very long time to me.”
To handle emergencies in space, astronauts need to remain calm and react quickly under immense mental pressure. “You can come out with a perfect plan,” says Parmitano, a former pilot with the Italian Air Force, “and then you can rest assured that you will be executing a different one.” And just to withstand the forces of spaceflight, astronauts need to be in peak physical condition.
These attributes were at the top of the list when the United States and Soviet Union began to consider putting people in space, and, for the first time in history, had to answer a question: What makes a good astronaut? (The word itself, first used in 1928, derives from the Greek for “star sailor.”)
As spaceflight evolved, though, other skills—such as knowledge in a scientific discipline—were added to the list of astronaut qualifications. And as the culture in the United States changed, opportunities in spaceflight were opened up to a wider array of the population.
Today, humans plan to return to the moon and eventually travel to Mars, pushing the bounds of exploration out into the solar system. The spacefarers to take these journeys will share some characteristics with the astronauts who came before, but will also be selected with the benefit of knowledge built up over six decades of human spaceflight. To live and work for extended periods of time in space or on other planets, these crews of star sailors will need diverse strengths and expertise.
Lessons in spaceflight
In the 1950s, when the U.S. and Russian space programs vetted candidates, they just needed individuals who could endure the flights. Little was known then about how the human body would respond to space. NASA’s initial call for astronaut applications included virtually any man shorter than 5’11” who had engaged in dangerous and physically strenuous activities, such as scuba diving or mountaineering. But President Dwight Eisenhower intervened, deciding that only military test pilots would be eligible.
“As a military man, Eisenhower had a great understanding and respect for the process of evaluation and promotion in the military,” says Margaret Weitekamp, chair of the space history department at the Smithsonian’s National Air and Space Museum. Military officers were presumed to be disciplined, loyal to the country, and willing to sacrifice their lives if necessary. And a test pilot already had proven the unique ability “to go up in a hurtling piece of machinery and put his hide on the line and then have the moxie, the reflexes, the experience, the coolness, to pull it back in the last yawning moment,” as Tom Wolfe wrote in his 1979 book The Right Stuff.
The Soviets initially took a slightly different approach to selecting their space explorers, known as cosmonauts (Greek for “cosmos sailor”). The first cosmonauts were about 10 years younger on average than the first U.S. astronauts, with less experience and flight time. Yuri Gagarin, the first person in space, was only 27 when he orbited Earth; the first American in space, Alan Shepard, was 37 on his first spaceflight.
“They’re green,” says Fordham University history professor Asif Siddiqi of the first group of cosmonauts. “You essentially have the space program mold and shape them.”
As the U.S. and U.S.S.R. gained experience flying people in space, they began to attempt more complicated missions, such as docking in orbit and sending astronauts outside their spacecraft. In the astronaut selection process, the two space programs put more emphasis on engineering education, and the Soviet program raised its standards for flight time, making the second group of astronauts older and more experienced than the first, Siddiqui says. Buzz Aldrin, selected in the third group of NASA astronauts in 1963, was the first person to join the corps with a doctoral degree (in astronautics from the Massachusetts Institute of Technology).
Even so, through the Apollo moon landings from 1969 to 1972, the qualifications to be an astronaut remained largely the same, focused on the pilot astronaut. Scientists were selected as part of NASA’s fourth astronaut group in 1965, but only one of them flew to the moon: geologist Harrison “Jack” Schmitt, who flew on the last human flight to the lunar surface, Apollo 17.
“I think if it were up to NASA, they would have never done it,” says John Logsdon, a space historian and professor emeritus at George Washington University. “There was so much external pressure from the scientific community that NASA felt obligated to fly at least one of the people who had been selected as scientist astronauts.”
Schmitt, who helped train other astronauts to identify geologic features on the moon, finally got a chance in 1972 to inspect the lunar surface, where he discovered patches of orange soil comprised of volcanic glass from a 3.5-billion-year-old eruption. Most of the scientist astronauts, however, would have to wait until the U.S. deployed its first space station.
Skylab, launched in 1973, was visited by three crews who spent a total of about 24 weeks on board. The first crew included the first physician astronaut, Joseph Kerwin. During 28 days in space—the longest mission up to that time—Kerwin monitored the crew, who remained healthy but lost weight and muscle mass. Those findings prompted NASA to increase the calorie intake and exercise time for future crews.
On Skylab 3 and 4, the other two crewed missions to the station, more strains of extended spaceflight began to reveal themselves. “Those early missions were really learning more about the effect of the zero-gravity environment, extended duration missions, on the human body,” says George Abbey, former director of NASA’s Johnson Space Center and a senior fellow in space policy at the Baker Institute of Rice University. “It was a learning experience.”
The crews, including the first electrical engineer and physicist astronauts, continued to monitor the medical effects of microgravity. Among them were “space sickness,” caused by seeing but not feeling movement while floating in space, and “puffy face syndrome,” caused by accumulating fluids.
The Soviets, meanwhile, were learning similar lessons about long-term spaceflight on their Salyut space stations. Both countries redoubled their efforts to study the physiological and psychological effects of long-duration stays in space. Team dynamics were studied as the astronauts underwent survival training in extreme environments, such as the deserts of Nevada and the winter forests outside Star City in Russia.
Women were still excluded from the NASA astronaut corps during the Apollo and Skylab programs. The first female cosmonaut, Valentina Tereshkova, flew on the Soviet Union’s sixth human spaceflight in 1963, spending nearly three days in space and orbiting Earth 48 times.
“In the Soviet Union, there had been such loss of life during the Second World War that you had many more women in professional roles,” Weitekamp says. “What you find is an interest in having a woman fly because it achieved the public relations, international diplomacy first of demonstrating that they could. And then you don’t find any sustained interest in having women as equal participants in the cosmonaut program.”
The requirement that astronauts had experience as test pilots effectively blocked women from flying on NASA missions, Weitekamp says, as women were not allowed to become jet pilots in the military at that time. Although a group of American women underwent tests and training, demonstrating that they could perform as well as men in spaceflight, and even scoring better on cardiopulmonary and eyesight tests, they were never given the chance to fly.
Part of astronaut selection, and some of the early prejudice, had to do with the kind of person who U.S. and U.S.S.R. leaders wanted to present as the ideal citizen, understanding that the astronauts would become global representatives of the nation. Gagarin was what Siddiqi calls “classic Russian.” He was “ethnically Russian, grew up on a farm, came up through Word War II, got educated,” and went on to join the military. Likewise, the first seven U.S. astronauts were all “college-educated white men, married with children,” Weitekamp says.
This archetype held through the Skylab missions. “The real change in personnel came in the run-up to the space shuttle,” Abbey says.
“The dream is alive”
For the shuttle, a new space plane designed to land on a runway and fly again, NASA would need bigger crews with a wider range of skills. The 122-foot- long orbiter was unlike anything launched before: It could carry between two and eight people, stay in space for weeks, deploy satellites, host large experiments, and dock to space stations.
“We were looking for people that had good engineering and science backgrounds and had performed in high-stress environments and worked well with team members,” says Abbey, who was in charge of astronaut selection, training, and flight assignments during the shuttle era. “That opened it up considerably … and we were also able to open it up to include a lot more women and include minorities that had the backgrounds we were looking for.”
The 1978 class of NASA astronauts was the biggest yet: 35 people including the first women, African Americans, and Asian Americans. In addition to pilot astronauts, NASA began to fly “mission specialists” who performed science or engineering tasks. By the ninth shuttle flight, “payload specialists” were flying as well, responsible for an experiment or piece of equipment.
In 1983, Sally Ride, the first American woman in space, flew on the seventh shuttle flight, a six-day mission to deploy multiple satellites. The next shuttle flight included the first African-American NASA astronaut, Guion Bluford, who returned to space on three subsequent launches. Additional women and people of color would follow, as efforts within NASA to increase the diversity of the workforce—particularly in the early days at the Marshall Space Flight Center in Alabama—reflected the civil rights progress of the country.
The model for shuttle astronauts established in 1978 held throughout the program, Abbey says. Space shuttles flew missions to repair malfunctioning satellites in space, including the Hubble Space Telescope. These repair missions were a first, and required veteran astronauts who could perform long and strenuous spacewalks. Shuttles also carried a science module called Spacelab built by the European Space Agency. The orbital lab provided a platform for astronauts to carry out microgravity experiments in physics, astronomy, materials science, Earth observations, and more.
Sending citizens to space
As NASA gained confidence in low-Earth orbit, another new kind of astronaut emerged: the ordinary citizen. Politicians got to tag along first, with Utah Senator Jake Garn and Florida Congressman Bill Nelson flying on the shuttle in 1985 and 1986, respectively.
“They did that for, I guess, their own reasons,” Abbey says, referring to NASA headquarters. “Congressman Nelson and Senator Garn were involved in overseeing the NASA activities, so, in a sense, I guess it gave them a personal experience of what was being done and how it was being done.”
Immediately following Nelson’s flight, a true member of the general public was slated to fly as a payload specialist on the space shuttle: Christa McAuliffe, a schoolteacher from New Hampshire. The mission ended in tragedy in January 1986 when space shuttle Challenger broke apart during launch, killing McAuliffe and the rest of the seven-member crew.
“That was the end of the citizen space program,” Logsdon says. “The second citizen would be a journalist and could well have been [Walter] Cronkite.” But after the loss of Challenger, NASA reverted to selecting only career astronauts to fly.
The next generation of space stations
In the Soviet Union, the space program continued to develop orbital stations. It made major strides with Salyut 6 and 7, which were occupied for a total of 683 and 816 days, respectively. The work led directly to one of the triumphs of the Soviet/Russian space program: Mir.
“Mir is a multi-modular, sort of monster of a space station,” Siddiqi says. “In 1989, they begin the permanent human presence in space on Mir, and they keep it occupied for 10 years straight.”
Not everything went smoothly, however. In 1997, while testing a new remotely piloted docking system, a cargo spacecraft about the size of a bus slammed into some of Mir’s solar panels and breached one of the station’s seven modules. The two cosmonauts and one NASA astronaut on board were able to sever the connections to the breached module and seal it off. Later, two of them ventured into the depressurized module in space suits to perform repairs.
These types of incidents, though at times straining the cooperation between the U.S. and post-Soviet Russia, were critical to establishing an international partnership in space. “The two sides have to work together. They have to be transparent, you know, you have to share what’s wrong,” Siddiqi says. Part of that openness involved the astronauts learning about the other country’s culture. Beginning with the Apollo-Soyuz docking mission in 1975, cosmonauts lived and trained in the U.S., and NASA astronauts did the same in Russia.
“They were able to speak to each other in their native tongues, and that turns out to be really important when you’re in a spacecraft,” Weitekamp says. “One of the things they often ask astronauts to do is to speak their less familiar language, because you’re less likely to make assumptions.”
Both the U.S. and Russia flew astronauts from other countries as well, such as England, France, Germany, Poland, Hungary, Mexico, Canada, and India. Budding space programs around the world were beginning to contribute research and hardware, and the next great space station began construction with the launch of the Russian Zarya module in 1998.
At the end of October, the International Space Station will celebrate 20 years of continuous human habitation. Circling Earth every 90 minutes, the space station is often held up as a triumph of international cooperation, having hosted 240 astronauts from 19 countries. Thousands of experiments in everything from astronomy and physics to botany and medical science have been conducted in orbit.
The first taikonauts
The modern era of human spaceflight has also welcomed a new nation to orbit: China. In the 1990s, China’s space program took advantage of improving relations with Russia after the collapse of the Soviet Union, says Brian Harvey, a historian and author who writes about China’s space program.
“The Chinese were able to benefit from all the experience that the Soviet Union has built up with Soyuz” by sending instructors to train in Russia and buying technology from its space program, Harvey says. In 2003, Yang Liwei became the first Chinese citizen in space. Because the country was not caught in a space race, China was able to take a slow, methodical approach to human spaceflight, studying maneuvers like docking extensively before carrying them out.
As for its astronauts, China followed the standard model, selecting first from a pool of military pilots. But the country also learned from some of the astronaut challenges in the U.S. space program. “If you look at the Mercury 7, these were people of strong conviction who wanted to do their own thing,” Abbey says. “I think the Chinese may have looked for people who would not present any of the types of difficulties of management.”
Like the U.S., China now is planning to send people to the moon. For missions like NASA’s Artemis program, which aims to establish a long-term presence on the lunar surface, the psychological effects of isolation and the dynamics of teamwork will be even more critical to consider when selecting astronaut crews, Abbey says.
The qualifications for astronauts will likely continue to evolve as space agencies turn their attention toward scientific goals such as establishing a radio telescope on the far side of the moon to observe the early universe or searching planetary bodies for signs of life. NASA has also pledged that a woman will be on the first U.S. flight back to the lunar surface.
Zena Cardman was selected as an astronaut candidate in 2017, making her a possible crewmember for flights to the moon. Before becoming an astronaut, she spent her career studying microorganisms in extreme environments.
“One of my favorite parts of this job is everyone is learning everything,” says Cardman, who has been training in jets and conducting simulated lunar spacewalks underwater in NASA’s Neutral Buoyancy Laboratory. For any astronaut, one of the most important qualities is “a willingness to get involved in disciplines apart from their own specific discipline,” Abbey says.
Beyond the individual qualifications of astronauts, the world is also facing a philosophical question about who should venture to space. Private companies are beginning to launch astronauts for NASA, and soon anyone with enough money could buy a rocket ticket.
James Jennings, the former deputy director of NASA’s Kennedy Space Center and an early member of the agency’s Equal Employment Opportunity board, says that if the vision of humans continually living and working on other worlds is to come to pass, we need a space program that exposes kids, particularly in underprivileged areas, to STEM disciplines.
“You’ve got to have a lot of people involved in science and technology,” Jennings says, adding that the biggest source of untapped potential is the “underserved population,” particularly people of color. “If you leave that segment behind, then as a country we’re going to be really behind the rest of the world,” he says.
During nearly 40 years at NASA, Jennings saw firsthand how outreach programs could give talented people the opportunity to work at the space agency—something he says has been de-emphasized as NASA’s education programs suffered budget cuts. In the future, efforts to expose young people to space science could be critical to the success of NASA and other space agencies. To expand beyond Earth in a meaningful way, the world will need all the talent it can get.