NASA, it turns out, doesn’t leave voicemail messages.

When Kayla Barron, a lieutenant in the U.S. Navy, was waiting to hear whether NASA had selected her for its next class of astronaut candidates, she actually missed the selection committee’s first call.

“It was a horrifying experience,” she told Fortune. “It was the most important call of my life.”

Once Barron, 29, connected with NASA, she found out that the selection committee, after a rigorous, months-long evaluation process, had selected her as one of its 12 new recruits—from the biggest-ever pool of applicants: 18,300.

Barron says she stands apart from her classmates in that she just recently came to see the astronaut program as a concrete goal. From the Navy, she didn’t see a straight path to NASA.

But working as a submarine warfare officer—operating in small teams, in confined spaces, in hostile environments—got her thinking about going into orbit. “The depths of the ocean are not that different from the vacuum of space,” she says.

In addition to being the most competitive class in NASA history, the new cohort is also one of the most diverse: Barron is one of five women. Of the 350 astronaut candidates in NASA’s history—including this year’s group—57 have been female.

Barron has a message for any girls who might want to add to that number, especially those interested in science, technology, engineering, and math fields.

It’s important, she says, “to learn how to fail and move on from failure. You have to risk failure in order to be successful.”

In applying for the astronaut program, Barron herself confronted that possibility. “I knew it was competitive,” she says, and she thought her unconventional background in the Navy might be a strike against her.

She thought about going to space for weeks before finally spilling the secret to her boss, Vice Admiral Ted Carter, as the two traveled to an event at the Air and Space Museum. “So while we were there, he introduced me to a bunch of astronauts,” she recalls. And finally, Carter asked Barron if she knew how to become an astronaut. When she said no, he responded: “You apply.”

“That was kind of a lightbulb moment,” Barron says. “It was the obvious answer; that I should go for it and put my name out there, and I wouldn’t be here if hadn’t.”