The making of an astronaut: 3 space fliers show what it takes

This is chapter one of a four-chapter story.

Every astronaut has a number and knows it: his or her place on the short list of those who have launched into space. The first American astronaut to ride a rocket, Alan Shepard, got #2 just three weeks after Russian cosmonaut Yuri Gagarin (#1) kicked off the era of human spaceflight in 1961. Neil Armstrong was #26 when he stepped off the lunar lander in 1969, creating some of the most famous boot prints in history. Sally Ride snagged #120 when she led American women into space in 1983. A few months later, Guy Bluford took the same giant leap for African-Americans at #125.

The most recent addition to the list, Jack Fischer, brought the current tally to 553 just a few weeks ago. Eight times more people have reached the summit of Mount Everest.

Countless Americans have dreamed of joining NASA's exclusive club — and the dream extends to citizens of other countries. When the space agency last asked for applications, in 2015, more than 18,000 hopefuls applied, shattering the previous record. But 99.9 percent of those aspirants walked away with rejection letters; Harvard's acceptance rate is roughly 78 times higher. Just 12 people were named astronaut candidates and summoned to Johnson Space Center, the sprawling 1,620-acre campus in Houston that is home to America's astronaut corps. Former astronaut Terry Virts, who learned of his selection in 2000 during a telephone call from NASA, describes the call as "one of the most wonderful and surreal events of my life."

NASA is so selective for two reasons. First, it can be. With so many wannabes, the federal agency doesn't have to settle for anything less than the best of the best of the best. After all, the government entrusts astronauts not only with the lives of their crewmates, but also with hardware worth hundreds of billions of taxpayer dollars — and with the United States' reputation as the world leader in space exploration.

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Second, the job is way harder than you think. Flying space missions demands a rare combination of intellectual and physical skills, plus special personality traits. NASA looks for technical expertise surpassing that of an airline pilot, the valor of a special forces soldier, the forbearance of a kindergarten teacher, and the stamina and decisiveness of a mountain climber — all in one person. And did we mention advanced training in medicine, engineering, or physics?

Earlier this month, NBC News MACH made the trip to Houston and sat down with NASA astronauts Karen Nyberg (#478), Kjell Lindgren (#542), and Sunita Williams (#450) to dig deeper into what it takes to join the corps, train for the job, and then perform well under enormous pressure. Like the others we have met, these spacefarers seem normal enough in conversation. But as astronauts describe all they have accomplished, it becomes abundantly clear that they simply are not like you and me.

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Astronauts come in every shape, size, and skin color. They hail from small towns and big cities, rising through the ranks in the military, academia, industry, and medicine. But all share the same program of intense training that has them making emergency repairs in spacecraft simulators both physical and virtual, testing their skill in notoriously unforgiving supersonic jets, and logging long hours underwater in full space gear — over and over, until their responses are automatic.

As the experiences of Nyberg, Lindgren, and Williams show, it's this combination of innate character and relentless training that prepares them for the challenges and hazards of spaceflight: the chaotic scenarios, but also the unnerving tedium of weeks or months spent with crewmates in an airtight container where even simple tasks like washing your hair and cooking become absurdly complicated. A spacecraft is, without a doubt, the most bizarre home office on the planet — or off it.

NEXT CHAPTER: Saving a Spaceman from Drowning