Stepping out of a capsule no bigger than a modest home kitchen, the four-person crew of NASA’s latest Human Exploration Research Analog study “returned” to Earth last month after a 45-day mission to fictional asteroid Geographos. Although the capsule never actually left NASA Johnson Space Center in Houston, the mission’s results could shape how the space agency’s astronauts someday handle the isolation, confinement and sleep deprivation likely to occur during interplanetary travel.

Crew member William Daniels, a geologist at the University of Massachusetts Amherst, has long adored cosmic exploration. He saw this mission as a small-but-significant step toward deep-space travel—NASA will use lessons from this crew to build protocols for human voyages to Mars. Unfazed at the prospect of sleeping just five hours per night and being subjected to a steady stream of invasive physiological and mental tests, Daniels volunteered to live with three strangers in the cramped capsule, which consisted of a flight deck, a living area and a “hygiene” module. Daniels spoke to Scientific American about his experience.

[An edited transcript of the interview follows.]

Talk me through a normal day in the capsule.

We’d wake up at 7 A.M. to a song of our choosing being blasted over the loudspeakers, which is just like they do it on the International Space Station. We had an eclectic mix of wake-up songs, because each crew member had different tastes. It ranged from Arlo Guthrie to the Beatles to Avicii. We liked the loud, fast-paced ones to help jump-start us out of bed.

Our morning started by donning lots of body sensors, such as voice recorders and activity monitors. The rest of the day was filled with flight-simulation scenarios and scientific tasks. For example, we did simulations where we would use a robotic arm to grapple incoming cargo pods. Or we would do simulations of extravehicular activity—actually venturing out to the asteroid to collect rocks and do geological surveys. We also grew brine shrimp and hydroponic plants. Some days were punctuated with simulated emergencies, either concerning spacecraft systems or crew health. We would have three square meals a day, with one hour for each. I thought the food was delicious and pretty varied—a real marvel of food engineering! It was mostly freeze-dried, and our kitchen consisted of just a water dispenser and a small convection oven.

We would eventually get to bed at 2 A.M. So we were limited in the amount of sleep we could have.

How did the sleep deprivation affect you?

Our team did surprisingly well with the sleep deprivation. I was expecting it to be much more difficult than it was. I think we can thank the lighting protocol for helping with that—during the day the lights were brighter and bluer, and in the evening they would become dimmer and redder. Keeping busy also helped us stay alert. There were moments though—like in down time, if I tried to read a book—that I would doze off. So I couldn’t read books inside the capsule. The sleeping pods themselves weren’t much bigger than a human body, and they had a mattress and white padded walls for insulation. They had a cocoonlike feel—very comfortable!

What were some of the biggest challenges your crew faced during the mission?

When you’re in such confined space, things like body odor—as silly as that might sound—can be a big thing. So we all made commitments, like being hygienic and keeping the workspace tidy. If we were shedding hair, we’d clean it up. And we’d try not leave our pens and other personal items all over the table. Just keeping a tidy work and living space was important.

Regarding personal cleanliness, how exactly did that work?

We each got 30 minutes of “hygiene time” each day. In the hygiene module, which was called “Serenity,” we had a shower, a toilet and a sink. So it was pretty normal with regards to showering. That’s one thing that set it apart from an actual space mission—it was kind of luxurious in terms of the hygiene.

How did you spend your free time?

Our group played Scrabble—every day. We did have access to Netflix, so we could watch some shows and movies. And one of the fun traditions of our group was “sophisticated Saturday,” where we would dress up in our nice clothes each week and have a meal together—it made us feel like we were civilized and really helped us bond as a group. As the mission went on we felt closer to one another, and we definitely learned a lot from each other. It was important to build those social relationships when we were confined together like that.

How much contact did you have with the outside world?

Contact was limited, but we were fine with that. Each week we were required to have a private phone conversation with a psychologist as well as a medical doctor. We were also allowed a 30-minute conversation each week with our friends or family. Those conversations were huge morale-boosters for me. The other contact we had on a regular basis was with mission control. We used radios to talk to mission control. One interesting thing was understanding how a radio delay would impact our communication with the ground. As we got further away from Earth, there was a longer delay in our communications. At the longest point, there was a five-minute one-way travel time for a message. So it would take 10 minutes to send a message and expect a response. For things that required a quick response, that caused some frustration, although I think our team did well with being autonomous during the long communication delays.

If that was it for outside contact, how did NASA collect samples from the crew?

For some of our biological samples, we had a stash of several hundred urine bottles preloaded in the space capsule. When those were full, we put them into the airlock and pretended to jettison them out to space. But really, ground control had a hidden trapdoor—we would put them in one side, and they would take them out the other. For the blood drawing, we would stick our arm through a curtain, and there would be a phlebotomist on the other side. We referred to this person as the “phlebotobot.” They would draw our blood without us ever seeing or hearing them.

What did you miss most about the outside world?

Being confined in there gave me extra appreciation for the things back home. From basic things like ice cream or talking to my family to just being outside. I also missed doing my regular life things—like work. Basically, I missed doing work! Ha! I also missed having the freedom to choose my daily schedule. When we were in there, 100 percent of our day was prescheduled for us. We had very little decision-making power.

What did you not miss about the outside world?

We were cut off from a lot of the social pressures we face in our normal lives, and that was nice [to escape]. And in a way, even not having to make decisions about our daily schedules was nice—kind of relaxing.

What was the most exciting part of the mission?

Takeoff and reentry were two highlights for me. During takeoff, they simulated the rumble of the engines, and our video monitors showed a view as if we were taking off from Earth. On reentry we flew past the moon, used our engines for a burn to adjust our trajectory, then gathered on the first level of the module to watch as the parachutes deployed. When we got closer to Earth they simulated the wind and other sounds we would hear. So those were pretty exciting moments. The in-between was more monotonous. I think that’s true in space travel as well—the takeoff and the landing are more exciting, and the in-between is more routine.

How did it feel to finally step out of the capsule?

We had two egresses. One was egressing from the space capsule into the larger warehouse. Our friends and family were there to greet us, and we felt really accomplished. The second egress was when we left the warehouse to go outside—and at that point it really hit me: There was hot, wet air in Houston, it was windy, and the moon was up. Just being outside was really an emotional lift for me.

How did you celebrate?

We ate junk food and drank beer.

You were in the capsule for 45 days. A round-trip mission to Mars would take more than a year and a half. Would you sign up?

No. This mission made me more aware of how much there is on Earth and how difficult a long-duration mission would be. So for me personally, no, but I hope that what we did in the HERA capsule makes it easier for future astronauts who do choose to do that.