Everything You Never Thought to Ask About Astronaut Food

“Burping in microgravity is probably not something you want to do a lot of.”

NASA astronaut Karen Nyberg floats a piece of food during mealtime.
NASA astronaut Karen Nyberg floats a piece of food during mealtime. (JSC / NASA)

Days before his return to Earth in 2008, NASA astronaut Daniel Tani told reporters he couldn’t wait to do something very ordinary after spending four months in space.

“I’m looking forward to putting food on a plate and eating several things at once, which you can’t do up here,” Tani said.

Plates are pretty useless on the International Space Station, where food—along with everything else—floats. Mealtime in microgravity usually consists of thermo-stabilized or freeze-dried entrees and snacks in disposable packages and pouches. Astronauts heat them up in an oven or add water before chowing down with a fork straight out of the package. The space station doesn’t have refrigerators or freezers to keep food fresh, so there’s no such thing as leftovers.

Despite the almost alien process of eating, astronauts consume many of the foods they would find back home: scrambled eggs, spaghetti, chicken teriyaki, broccoli au gratin, oatmeal with raisins. During the holidays, they have turkey, candied yams, cornbread dressing, and other seasonal foods. The current menu includes about 200 foods and beverages. Some items can be eaten in their natural form, like nuts and cookies. But most of the food has to be prepared in a laboratory and carefully tested over and over, to ensure it’s fit for consumption but can also last for two years before opening. Some of the prep veers into Food Network territory: The lab gets volunteers to judge food items on appearance, color, flavor, texture, and aroma.

The process of developing a microgravity-friendly food item can take months or years, says Vickie Kloeris, the food scientist who runs the ISS food-systems lab. I spoke with Kloeris about eating in space, how to pack food for a mission to Mars, and the myth of astronaut ice cream. Our conversation has been edited for length and clarity.

Marina Koren: So you got to Johnson Space Center as a food scientist in 1985. What was the state of astronaut food back then?

Vickie Kloeris: It really wasn’t all that different than it is now. Everything was shelf-stable, just like it is now. We had thermo-stabilized, freeze-dried, natural-form food, irradiated food, powdered beverages—just like we do now. But we didn’t have nearly as much variety during the Space Shuttle program because the missions were short, so we really didn’t need a whole lot of variety. When I came to work here, we were flying entrees from the MREs from the military. We don’t do that anymore because the MRE entrees are way too high in salt and fat for what we want for our long-duration crew members. The military has good reasons to have that salt and fat in there, but they are negatives for our crew members.

Koren: How do you transform a a terrestrial recipe into something that’s fit for consumption in microgravity?

Kloeris: Many terrestrial recipes, especially entrees, are not shelf-stable. The end product requires refrigeration. We don’t have a dedicated refrigerator or freezer for food on the space station, so everything that we send to orbit has to be shelf-stable. So we convert standard recipes into shelf-stable foods through freeze-drying and thermo-stabilization. Thermo-stabilization is basically canning—except we don’t do it in cans, we do it in pouches. Pouches are much lighter in weight and more efficient to stow. The tricky thing is, you can’t just take a traditional recipe and thermo-stabilize it or freeze-dry it and have it work. If only it were that simple. When we go to create a new item, it often takes multiple attempts, multiple adjustments, to end up with something that actually works.

Koren: Does microgravity affect the taste buds? Does food taste the same on the space station?

Kloeris: That depends on who you talk to. There is no scientific evidence that microgravity alters the taste of food. There is anecdotal evidence from crew members that they feel like their taste buds are somewhat dulled in orbit. Other crew members say it’s all in their head and there is no difference. But they are probably getting less aroma from the food when they eat in orbit than when they consume those same items on the ground. They’re eating out of packages rather than off a plate, so that can hinder the amount of aroma they’re getting. Plus, when you heat food on the ground, a lot of the heat rises and the aroma goes with it. When you heat stuff in microgravity, the heat can dissipate in different directions, so that has the potential to spread out the odor and have it be less intense. So that could be it. Just like when you and I are congested down here and we’re not getting as much aroma—the food’s not going to taste exactly the same.

Koren: Which foods are the most difficult to prepare for space?

Kloeris: Anything that creates a lot of crumbs. Crumbs are very difficult to deal with in microgravity because they’re just messy. When they get loose, they can make it into the air filtration system. You have to find a way to clean them up, and that usually involves a vacuum cleaner. Anything that requires refrigeration to remain microbiologically stable is going to be impossible to send up there. We occasionally get to send ice cream because they’ll have a freezer for medical samples that’s empty on the uphill trip. When that happens, we can send some frozen ice-cream treats and they have to eat those pretty much as soon as the vehicle docks, because they’re going to have to fill up that freezer with medical samples.

Koren: Have you tried to develop a microgravity-friendly recipe that just didn’t work?

Kloeris: We’ve had it happen more than once. We tried a thermo-stabilized cheesecake and we were never, never happy with the results. So we gave up on that.

Koren: How about carbonated drinks like soda? Can astronauts drink that?

Kloeris: Not unless they’re packaged under pressure, like in a whipped-cream can. In microgravity, the carbonation will not remain with the beverage. It will separate. Coke and Pepsi flew in pressure vessels back in the ’80s on one flight, and at that time, they didn’t have a way to chill it. So it was like, okay, we had hot Coke and hot Pepsi, so what? You’re probably not going to want a lot of carbonation in your diet when you’re in microgravity anyway, because when you burp down here, it’s dry burp. When you burp in microgravity, it’s probably not going to be a dry burp.

Koren: What ... what kind of burp would it be?

Kloeris: Wet. You’re gonna have food coming with it. When you burp, you’re burping through that sphincter at the top of your stomach. That is not a full closure. So in microgravity, when you eat, the food floats high in your stomach. Burping in microgravity is probably not something you want to do a lot of.

Koren: Have you been thinking about what kind of meals NASA would need to prepare for longer missions, like a trip to Mars or into deep space?

Kloeris: The research team in our lab is trying to figure that out right now. For Mars, the food that they eat on the return trip will be somewhere between five and seven years old, so that is a huge challenge. We can actually make food that is microbiologically safe to eat for that period of time. But there’s very few foods in our current food system that would maintain sufficient quality after that long. Even though we can stop microbial changes in these products by preserving them, we can’t stop the chemical changes. The color, texture, and flavor are going to change, and the nutritional content is going to degrade. We’re looking into which items are most susceptible to degradation. A particular nutrient will be more stable in one food than in another. For instance, vitamin C is not very stable in thermo-stabilized products, but it’s very stable in powdered beverages.

Koren: What recipes are you working on right now?

Kloeris: We aren’t developing any new foods right at this moment. We have some new products that have been developed over the last couple of years that we’re just now introducing into the food supply to see how the acceptability goes. We have a new freeze-dried roasted-brussels-sprouts dish, a couple of thermo-stabilized fish casseroles—to try to get some more omega-3s into the food system—a freeze-dried fruit salad.

Koren: I’m sure people have asked you this a million times, but how did that chalky, Neapolitan astronaut ice cream become a thing?

Kloeris: During [the Apollo program], one of the crew members did request ice cream, but what they flew doesn’t look like anything that they sell at the museums or the visitor centers. I think that just took off because it was something the kids liked and a commercial company made it. What actually flew during Apollo was a synthetic cube that was dairy-based. That’s about as close to ice cream as they got.

Koren: Does your job change the way you look at preparing food at home?

Kloeris: My family thinks I overreact sometimes because I worry about food safety. I’m not one to leave the turkey sitting out on the table for hours after dinner.