Astronaut Scott Kelly, whose memoir, Endurance, will be published by Knopf in September, holds the record for most days in orbit: 520. He’s traveled into space four times and spent a total of more than 18 hours on space walks. Yet, in his apartment overlooking Houston’s downtown Discovery Green, named for the city’s famous association with space exploration, the only obvious memento of his highly decorated two-decade-long career at NASA is a large glass case holding—what else?—a space suit. It’s the same one he wore on his first long-duration space flight in 2010 and 2011.

Pulling off the front of the case, Kelly says, “It’s still off-gassing and smells a little like space”—a scent he describes in Endurance as like that of “burnt metal.” It’s just one of many surprising facts that Kelly serves up in his memoir; another is that the Russian-made space suit is sealed against the vacuum of space with a couple of rubber bands. “It goes back virtually to when Yuri Gagarin made his first mission,” Kelly says. “The Russians are ingenious and very committed to the idea that if something works, it doesn’t need replacing.”

Kelly notes that the suit, which is entered through a zipper in the chest, can be a bit snug. “In the absence of gravity, especially after a year, our bodies do reconfigure and expand.” But he adds: “I want to be clear about something: I did not grow two inches after my year in space, as reported all over the internet. That did not happen.”

Were it the case, Kelly—who is a stout five feet, seven inches tall—would stand taller than his identical twin brother Mark, who is also one of NASA’s most highly decorated astronauts. Mark Kelly is perhaps best known as the husband of Gabby Giffords, the former Arizona Congresswoman who was nearly assassinated in 2011. News of his sister-in-law’s shooting reached Kelly during one of his four missions to the International Space Station, one of several dramatic moments recounted in the book.

“I wanted Endurance to give people a sense of what it was really like to live on the space station for a year, and I felt it was important to get across that life on Earth doesn’t stop for you just because you are in space,” Kelly says. “In fact, your connection to daily life on Earth becomes all the more important.”

Kelly writes lovingly of his long-term partner Amiko (who returns in the middle of our interview having just attended a session of “goat yoga”—“More like yoga with goats around, than yoga with goats,” she explains) and describes the rigors of maintaining an Earth-to-space relationship. This ranges from prosaic tasks, like explaining how to connect the speaker to their home stereo, to the emotional issues of a long-distance relationship taken to the next level.

At the time of Kelly’s final extended mission, Amiko was working in public relations for NASA, and the couple bonded, in part, by collaborating on social media. They promoted a viral video of Kelly chasing a shipmate while dressed in a gorilla suit and posted photos of different environmental and climate events as seen from the ISS (sometimes against NASA’s wishes). “I can’t say if climate change exists, but I can tell you pollution exists,” Kelly says. “[And] from the first time I went up to the last, I could see the deforestation of large parts of South America.”

Kelly notes that the ISS is a collaboration between the space agencies of Russia, Japan, Canada, Europe, and the United States. With the retirement of the space shuttles, NASA is dependent on Russia to fly Soyuz rockets to and from the ISS; and as Kelly says often in the book, the mission would have been impossible without international collaboration.

Throughout, he emphasizes his intimate relationships with his many Russian colleagues. He also describes their preflight rituals, many of which date back to Gagarin’s first spaceflight (walking past a row of trees, each one planted by previous cosmonauts and astronauts who had flown into space, and stopping on the drive to the spacecraft to urinate on a rear tire of the bus; women participate by carrying a vial of urine to douse on the tire).

“The Russian references make the book feel very timely,” Kelly says, referring to the current controversy surrounding President Trump and Russian tampering with the election. Kelly’s concerned that Putin will retaliate for the U.S. sanctions against Russia by limiting or ending NASA access to the Russian program. “This would effectively end the mission of the ISS,” he says. As we speak, Kelly continues to eyeball a TV turned to CNN.

As for reaching Mars, Kelly believes that humanity can and will make it to the red planet someday, but it will take a worldwide effort to get there. And though he regrets that he won’t have the opportunity to travel on that mission—though he says it may happy in his lifetime—his hope is that his book will inspire future generations to make that journey. “When I read Tom Wolfe’s The Right Stuff as a college student it changed the course of my life, and I hope that the same will happen after some young person reads Endurance.”

In addition to this book, Kelly has already been commissioned to do a book of photographs that he took from space, and also to write several books for Random House Children’s Books, the first of which is My Journey to the Stars, illustrated by André Ceolin (Crown, Oct.).

All in all, Kelly isn’t likely to be done circumnavigating the globe: foreign rights for Endurance have sold in more than 20 countries, including to Russia, and he’s committed to a 20-city U.S. book tour. (His sense of adventure extends to his home planet, as exemplified by the well-thumbed copy of Atlas Obscura sitting on his desk.) “It’s taken me 15 months to write the book, which is already longer than the time I spent on the space station, and it looks like I’m going to spend an equal amount of time promoting it.”

Having already achieved so much, Kelly wants to set one more record: to be the author of the bestselling space book of this century. His competitive side is best summed up in an anecdote from Endurance in which Kelly confesses to struggling with growing some flowers on the ISS on social media. Someone taunted him on Twitter about it, saying Kelly’s “no Mark Watney”—a reference to the main character in Andy Weir’s bestselling novel The Martian. Kelly took it as a personal slight and doubled down on his efforts, eventually succeeding in getting his zinnias to bloom.

So it’s no surprise that, when I make a passing reference to Chris Hadfield, the Canadian astronaut who became a celebrity after posting a video of himself singing David Bowie’s Space Oddity on the ISS and who has since penned several bestsellers, Kelly replies, stone-faced: “Never heard of him. Is he an astronaut?” Then, offering a knowing smirk, says: “Oh, you mean that guy who can’t sing?”