Peggy Whitson is back! The record-breaking astronaut reveals why she chose to command a private space mission after leaving NASA.

Record-breaking astronaut Peggy Whitson will return to space to command a commercial mission for Texas-based Axiom Space, three years after her retirement from NASA in 2018.

"There was no question," Whitson told Space.com in an exclusive interview about her decision to return to space. Whitson retired from NASA in 2018 after setting a number of records, including the most cumulative days spent in space by a NASA astronaut with 665 days, 22 hours and 22 minutes in space. But Whitson is about to add 10 more days to that record, as she will command a private mission to be launched by the private spaceflight company Axiom Space. 

"It feels phenomenal," Whitson said about making her return to spaceflight with these new planned missions. "Obviously, when I retired from NASA I wasn't sure how soon any of the commercial spaceflight opportunities might be available … so [I'm] very, very excited."

In photos: The record-breaking career of NASA astronaut Peggy Whitson

During her time at NASA, Whitson flew three long-duration missions to the International Space Station. In addition to her cumulative spaceflight record, Whitson was the first woman to command the space station and previously held the record for longest-ever single spaceflight made by a woman (a record NASA astronaut Christina Koch beat in 2019). 

Whitson, who is also a biochemist, went on to serve as NASA's chief astronaut before retiring from the agency in 2018. 

Now, Whitson will serve as commander of Axiom Space's Ax-2 mission, the second planned private spaceflight mission for the company. Whitson will also serve as backup commander for Ax-1, the company's first private crewed launch to the space station. 

"I've always been a part of NASA's program. And it's very exciting to transition and be a part of commercial space as well," Whitson said.

The biggest difference between this flight and her previous missions with NASA, Whitson said with a laugh, is the much shorter length of this mission compared to her previous trips to space. "Ten days," she said with a laugh, "I'm not sure how to manage … we'll figure it out." 

So what is Whitson most looking forward to with her return to space? Looking back at her home planet. "It never gets old, looking at the curve of the Earth. It really doesn't."

Photos: The first space tourists

Booming commercial spaceflight

On the Ax-2 flight, Whitson will conduct genomics experiments for the California company 10x Genomics, alongside pilot and racecar driver John Shoffner. This type of research is a major part of why Whitson is so excited about not just this mission, but the growing commercial space industry as a whole. 

"I think it's so much more than space tourism," she said. "The commercialization of space is going to be in pharmaceuticals, it's going to be in manufacturing … even things like growing stem cells like I did on my last International Space Station visit, I think has a huge potential for commercialization in space … I see Axiom Space, commercial space, as being something that is going to be widely used."

"The idea that we are taking people up is like the beginning of aviation … you know, when we were commercializing aviation, only a few people could manage to make that work. But the process of developing that and building that infrastructure is what made it possible for pretty much anybody to be able to get a plane ticket nowadays. And so hopefully, that's the next step for commercial space." 

Getting the crew together

Whitson has already begun training with Shoffner, who is also a backup crewmember for Ax-1, and the pair have so far completed centrifuge training and a zero-g flight, she said. 

"In such a short period of time, you don't get to teach a lot of people very much about being in zero gravity, but it's still a good familiarization that you really have to think about things in a different way," she said about their zero-g flight, adding that they plan to complete SpaceX and space station training soon. 

"It's actually really a lot of fun to go back into training with the new guys," Whitson said about the start of training, which so far includes Shoffner and we expect to include more of the crew as time goes on. "Their excitement about everything helps renew my excitement, and so it's a lot of fun."

But this fun isn't all fun and games. 

"Making sure you integrate with the crew is really important," Whitson said. "Having been on the long-duration side of it before when many shuttle crews were visiting, I'm very sensitive to how to best go about integrating our crews so that we don't get in the way."

"I want my crew to be a team, just like a NASA crew is," Whitson said. "We will do training to ensure that we can become that team and that we can rely on each other … you don't necessarily get to pick your crew, you just have to work on making things work to everyone's benefit. And that's what I will be doing with my crew for Axiom."

Axiom's private spaceflight plans

Ax-1 and Ax-2 are two of four crewed missions that Axiom Space now has planned, with Ax-3 and Ax-4 to follow, the company confirmed on June 2. To date, Ax-1 is the only one of these missions that NASA and Axiom Space have an agreement for, with the Ax-1 agreement announced May 10. 

Axiom Space will fly all four missions, which are set to launch by 2023, with SpaceX's Crew Dragon spacecraft. The company additionally plans to launch a private module to the space station in 2024. By 2028, the module should be ready to detach from the station and move freely in Earth's orbit as the starting point for a larger, privately-owned space station. 

"We are on track to enable that future by managing the first-ever private missions to the ISS as a precursor to our development of the world's first commercial space station," Axiom president and CEO Michael Suffredini said in a statement. "SpaceX has blazed the trail with reliable, commercial human launch capability and we are thrilled to partner with them on a truly historic moment."

Email Chelsea Gohd at cgohd@space.com or follow her on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.