Astronaut Scott Kelly sits inside a Soyuz simulator at a training center in Russia. Kelly spent a record-breaking year in space. (Bill Ingalls/AP)

Marcia Bartusiak is a professor in the MIT Graduate Program in Science Writing. She is the author of six books on the frontiers of astrophysics and its history, including "Black Hole" and "Einstein's Unfinished Symphony."

For many of us, the childhood fantasy never went away. We grew up glued to our grainy black-and-white TVs, watching with awe as Alan Shepard and John Glenn rocketed into space in blazing glory. It was easy to imagine that, someday in the future, we'd have the same chance to be free from the confines of gravity. Few have gotten that opportunity, but "Endurance," astronaut Scott Kelly's memoir (written with Margaret Lazarus Dean) of his record-setting year on the International Space Station (ISS) in 2015, offers Earthlings an informative and gripping look at both the adventures and day-by-day experiences of living in a metal container that is orbiting Earth at 17,500 mph.

Yet at the same time, Kelly brings our dreams crashing down to Earth, vividly reminding us of the many challenges — some mundane, others quite scary — of that cosmic frontier. It's not all beautiful views of our planet and restful floats in zero-g. There's the burned-out lightbulbs, the mold and dust, the never-ending hum of equipment, the occasional flashes in your vision when a cosmic ray passes through your eyes, the lost bone mass, and the build-up of carbon dioxide when the scrubbers sporadically malfunction. "If we are going to get to Mars," Kelly writes, "we are going to need a much better way to deal with CO2. Using our current finicky system, a Mars crew would be in significant danger," and if "the toilet broke and we couldn't fix it, we would be dead." He and his colleague, Russian cosmonaut Mikhail Kornienko, were human guinea pigs, hoping to learn the long-term effects of space isolation on mind and body.

Given Kelly's history growing up, the book's biggest surprise is that he even made it into space. A terrible student, he was more interested in partying and hurtling down a hill on a bike than sitting quietly in a classroom. Graduating from a New Jersey high school in the bottom half of his class, he was about to flunk out of college — until he came upon Tom Wolfe's "The Right Stuff" in the campus bookstore. He was immediately drawn to the book's "young hotshots catapulting off aircraft carriers, testing unstable airplanes, drinking hard, and generally moving through the world like bad­asses." Almost overnight, he knew he wanted to join them. Inspired, he gradually learned how to focus on his courses, changed to a military-oriented school and told his new roommate that he was going to be an astronaut. His friend replied, "Well, I'm going to be an Indian chief."

But Kelly proved all such doubters wrong. Within years, he was flying off aircraft carriers as a naval aviator (some of the most exhilarating sections of the book) and then became a test pilot. He at last filled out his NASA application in 1995 and was accepted into the largest astronaut class in NASA's history: 44 in all, including his twin brother, Mark. Within four years, Kelly was in space, aboard the space shuttle Discovery sent out to repair the Hubble Space Telescope. He compared his training for that moment to "getting a Ph.D."

“Endurance,” by Scott Kelly (Knopf/Knopf)

Piloting the space shuttle had been Kelly's sole ambition. "I didn't want to get that space station stink on me . . . resulting in fewer shuttle flights." But when asked, he served. He reluctantly agreed to stay on the station for six months in 2010-11, by then rocketing up on a Russian Soyuz after the shuttles were decommissioned. That experience made him especially qualified for a repeat performance, but this time for an entire year, with his personal quarters on the station no bigger than an old-fashioned phone booth.

"Endurance" is filled with minutiae on the ISS's modules and equipment, which space aficionados will probably lap up, yet it remains a fascinating read. Upon opening the Soyuz hatch to enter the ISS, for example, Kelly senses something familiar: "A strong burned metal smell, like the smell of sparklers on the Fourth of July. Objects that have been exposed to the vacuum of space have this unique smell on them, like the smell of welding — the smell of space."

His language is earnest and straightforward, just the style one expects from an astronaut. At the same time he frankly reflects on how his career upended his family and marriage. And then there is the boisterous camaraderie with his colleagues and stationmates, not to mention the astronaut rituals. Because the Russian cosmonaut Yuri Gagarin, the first human to journey into space, in 1961, peed on the right rear tire of his launchpad bus before entering his capsule, every astronaut and cosmonaut launching from Russia has done the same for good luck ever since (women bring a bottle of urine to splash on the tire).

The year does not go quickly for Kelly. Thirteen other astronauts and cosmonauts would come and go as he and Kornienko stayed put, each dealing with separate duties in their respective Russian and U.S. modules. Kelly completed a few spacewalks for repairs (which are far more arduous than the traditional publicity suggests), dissected rodents to study the effects of spaceflight on mammal physiology and took a stab at playing botanist Mark Watney in the movie "The Martian." He grew lettuce and zinnias, to test whether fresh food would be possible for Mars travelers. In this endeavor, he learned that there is also an emotional need for such spaceborne farming, confessing that he had "been missing the beauty and fragility of living things" over his sequestered year.

What no one misses are the inherent dangers. During his year in space, three non-manned supply ships exploded after launch, forcing the station inhabitants to ration for a while. More horrific is the space junk, the myriad debris and old satellites that buzz around the Earth at thousands of miles per hour. Most are tracked, and the ISS's engines are fired up routinely to move the station out of the way. But sometimes a new bit of junk is sighted with too little time for such a maneuver, which happened during Kelly's year on the ISS. All aboard took shelter in the Soyuz capsule for 10 excruciating minutes. "I realize that if the satellite had in fact hit us," Kelly writes, "we probably wouldn't even have known it. . . . [We] would have gone from grumbling to one another in our cold Soyuz to being blasted in a million directions as diffused atoms, all in the space of a millisecond."

But every astronaut and cosmonaut willingly accepts such challenges for a reason: to secure the future of spaceflight. "It will be very, very difficult, it will cost a great deal of money, and it may cost human lives," stresses Kelly. "But I know now that if we decide to do it, we can."

Just make sure European Space Agency astronauts are included in that first trip to Mars. According to Kelly, they bring the best food.

A Year in Space, a Lifetime of Discovery

By Scott Kelly

Knopf. 387 pp. $29.95