Sally Ride was America’s sweetheart—a famous and revered hero for being the first U.S. woman in space. And yet in many ways we barely knew her.

That will change for readers of Lynn Sherr’s new biography, Sally Ride: America’s First Woman in Space (Simon & Schuster, June 2014). Sherr became a good friend of Ride’s over many years reporting on the space shuttle program for ABC News, including both of Ride’s space shuttle flights in the 1980s and her role investigating the Challenger and Columbia shuttle accidents. Yet Sherr, like many who knew Ride, was surprised after the astronaut’s death to learn that she had been in a relationship with a woman, Tam O’Shaughnessy, for 27 years—starting while she was married to fellow astronaut Steve Hawley. Ride and O’Shaughnessy had played tennis together as teens (both were accomplished players). In 2001 the two co-founded Sally Ride Science, an education company devoted to encouraging kids, especially girls, to pursue science.

After Ride died of pancreatic cancer in 2012 Sherr conducted exclusive interviews with Ride’s family and friends as well as O’Shaughnessy to paint a fuller picture of the astronaut’s life than the public had glimpsed before. Sherr spoke with Scientific American about Ride’s loves, her experiences in space and the power of science for women.

[An edited transcript of the conversation follows.]

You were a friend of Sally’s and knew her pretty well. How do you feel you know her now, after writing this book?

I certainly know her a lot better. The revelations about her personal life make me feel bad that she didn’t feel she could share it with the public and the people who really cared about her.

I wouldn’t be honest if I didn’t say that [her secrecy] hurt me a tiny bit. By the same token, it’s her life and she gets to live it the way she wants. The fact that she never mentioned Tam, it hurts me—not that she left me out of her life but that I was unable to share it with her. But I’ll take what I got because she was a wonderful friend and we had a lot of terrific moments together.

Did keeping this secret weigh heavily on Sally?

Tam makes a point about what a happy person Sally was. She woke up with a smile everyday, and didn’t seem to have a problem with this for the most part.

If it hadn’t been for Tam being very bold and very honest and very real about their life together, Sally would have died without ever saying a word. There’s no evidence that she had any intention of talking about this. But when Tam brought it up, Sally said, “Whatever you want to do is fine with me.” I think that speaks to two things: It’s a huge tribute to Tam for taking the lead, and it’s also a huge credit to Sally for saying, “Go for it.”

How much of Sally’s secrecy had to do with her association with NASA?

Sally remains the only publicly known gay astronaut—and there have been a lot of astronauts. Do I believe there were others? Of course I do. That they have chosen not to come out is their decision, but it is largely about the attitude of the country and the space agency.

Sally’s made a huge difference. This is an agency that for a long time couldn’t even deal with women, let alone gay women. This is an agency that has indeed opened up, that has made enormous social changes, to their credit. This, too, will change. Do I believe there will eventually be an openly gay astronaut selected? Yes.

But I can’t imagine being gay in those days and feeling the least bit comfortable about saying anything about it at NASA. She wouldn’t have been hired, she wouldn’t have been selected and she never would have flown. It was a different era.

Given how private a person Sally was, it’s somewhat surprising that she took on a job that would make her one of the most famous people in the country. How did she deal with the fame?

She really did hate a large part of that. She was a severely private individual. It was painful for her to have to do a lot of public speaking. She was quite good at it, however. But before she went on stage she had to psych herself up every single time.

She did like the doors that it opened. She enjoyed the fact that she got her phone calls answered immediately, and she liked the power that went with it. She had no time for bureaucracy.

What were the qualities that got Sally selected over all the thousands of applicants for the astronaut program?

She was very smart and did quite well in college and grad school. They liked her astrophysics degree. They also really liked the tennis. They were looking for all-around people. Being a shuttle astronaut means being able to pivot on a dime. They liked the idea of somebody who had outside interests. I think also the teamwork aspect of her tennis career was very, very important. Being an astronaut was not an individual thing. It’s very much a crew and a team and a cooperative effort, and I think they saw she was someone who could be a team player.

Sally was one of six women selected in that first class of shuttle astronauts. The decision on who would be the first woman to fly—what did it come down to?

The six women were all extraordinary individuals. But Sally floated to the top of that crew as well. I think her work with the [space shuttle] robot arm was a huge advantage for her. Sally somehow picked it up in a way that everybody was so admiring of. She would work every problem through until she knew what she was doing. And she was also very cool under pressure.

You found some of Sally’s notes about her first spaceflight. How were her impressions different from the picture she painted for the public?

When she first unstrapped and was first in weightlessness, it wasn’t so perfect. She felt a little queasy, and couldn’t eat right away. She didn’t want to be “upside down” in relation to the Earth. Astronauts never talk about this. You’re supposed to fly up there, float around and everything is wonderful. But space sickness is a very real problem when you are up there on a mission trying to do a job. Sally, like everybody else, never admitted that she felt the least bit uncomfortable. Suddenly I realized that she did, which was a very rare admission for a type-A astronaut with the right stuff.

What else in your research came as a surprise?

During the post-Challenger investigation, the fact that she had been the source of the first piece of paper indicating that management understood that those supercold temperatures were going to be damaging to the [space shuttle] O-rings, and that she’s the one who passed it off to the commission, was a great revelation. I have yet to find the source of who leaked it to her.

Also, during the Columbia investigation, she leaked to [reporter] Todd Halvorson that had NASA been able to launch another shuttle, there might have been the possibility of rescuing the crew. This info got out because she was the leaker. This has never been revealed before. This is so Sally—no fingerprints, just do it.

You write that NASA was Sally’s launchpad, not her apogee. What do you think was her high point?

I think Sally Ride Science was very much where she wanted to be. I don’t think she knew that when she first flew but science was her life. And to be able to combine her love of science with her deep concern for helping women and young girls, to me was the perfect combination of the things she wanted to do with her life.