Science fiction tends to present space food as either flavorless, prefabricated cubes or plates of luscious Earth food that magically appear out of high-tech replicators. In reality, the truth is somewhere in between.

What do astronauts eat? According to NASA’s Vickie Kloeris, the menu is expansive, provided food items can survive microbe-killing heat treatment or complete dehydration.

“We’re able to provide a wide variety of products in thermal-stabilized or freeze-dried form,” says Kloeris, who manages food systems for both U.S. shuttle and International Space Station (ISS) missions. “And we can provide some in natural form, such as cookies or crackers.”

Perusing the Menu

Far from flavorless cubes, the menu selection includes such astronaut favorites as shrimp cocktail. The shrimp come freeze-dried, and the spicy cocktail sauce arrives as a powder. Just add water and you’re in low-gravity flavor country.

SLIDE SHOW: Top 10 Best Space Food

The preservation process doesn’t work for every food item. Acceptable space pizza, Kloeris says, continues to elude NASA. Yet an astronaut aboard the ISS still has roughly 180 foods and beverages to choose from — and that’s just the American menu.

“The Russians have about 100 different food and beverage items on the ISS, and we have a few from the Japanese agency and a few from the European Space Agency as well,” Kloeris says. “So we have around 300 different foods and beverages in orbit at the ISS that the crew members can choose from.”

Aside from some occasional requests for a particular blend of coffee, there’s very little ordering off the menu. NASA has responded to requests for kosher meals before and has even provided vegetarian meals — at least for short-term visits.

“Most of our vegetarians have flown on the shuttle, so if we send a vegetarian crew member up for six months in orbit, that’s going to be a challenge,” Kloeris says. “Especially because half the food systems come from the Russian side, and I can tell you there is very little vegetarian on the Russian menu.”

MORE: What’s the Top 10 Worst Space Food?

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ISS crew members also get to stash a few “preference items” away, enough to equal 1 cubic foot of storage space for every month they’re in orbit. That should take care of the space munchies.

Transportation and Storage

You might be wondering why all this space food is either dried-out or heat-treated. First, NASA demands a pretty high shelf life for its groceries: two years for most freeze-dried foods and three years for thermo-stabilized foods. And second, there’s only so much room aboard the resupply missions.

“ to the International Space Station is a very precious commodity,” Kloeris says. “We’re launching food on the shuttle and will continue to do that until the shuttle retires, but we are also sending food to Russia to launch on the Progress, to South America to launch on the European Space Agency (ESA)’s Automated Transfer Vehicle (ATV) and to Japan to launch on the H-II Transfer Vehicle (HTV).”

WATCH VIDEO: What’s the tastiest space food? James Williams catches up with NASA Astronaut Leroy Chiao to find out.

This not only involves sending the food into orbit, but also transporting it across international lines to launch sites around the globe.

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“The biggest challenge is getting the food where it needs to be,” Kloeris says, “figuring out which vehicle to put it on, when the vehicles are going to launch and when they’re going to get to the station so we can supply a consistent supply of food aboard the station. Launch schedules change, and it’s difficult to keep up with that.”

Dehydrated foods offer a particular value as the ISS’s newest dehydration station uses recycled water from the rest of the station. And speaking of recycling, you won’t find any such efforts when it comes to leftover food packaging — and there’s quite a bit of it.

“It takes a lot of packaging to get the kind of shelf life we need on these products,” Kloeris says. “Plus the crew members really want the items to be packaged in single servings. They don’t want to have to deal with opening and re-closing things because it’s difficult to deal with bulk storage in microgravity.”

All that packaging — along with used clothing and other waste — goes into the empty, unmanned resupply vehicles. When it’s time for a new Russian Progress, European ATV or Japanese HTV to arrive with fresh goods, the ISS crew dumps the old ones to burn up on reentry.

Health Food in Space

NASA emphasizes nutritious space food and, luckily, human nutritional requirements in space are pretty much the same as they are on Earth, with a few small exceptions.

“NASA has discovered some things about nutrition that are slightly different in space,” Kloeris says. “For instance, you don’t need as much iron because you’re not turning over red blood cells as frequently in microgravity as you would on the ground.”

WIDE ANGLE: Space Food and Orbital Dining

Human digestion works pretty much the same in orbit as well, except that stomach contents float a bit high. As a result, astronauts tend to feel full a lot faster than they would on Earth. The solution? More meals, smaller quantities and lots of snacking. If we ever have orbital restaurants, you can be sure they’ll serve mostly tapas.

Space food has come a long way over the years, but the work of space nutritionists is far from finished. One of NASA’s current projects involves cutting down on sodium levels in space food.

“Consuming too much salt isn’t healthy, and that’s especially true for our astronauts,” Kloeris says. “We know that high sodium contributes to bone loss, and all astronauts experience at least some degree of bone loss when they’re in orbit. So we’re working right now to try to bring down the overall sodium content of the menu to help mitigate some of the medical issues that have begun to show up in our long-duration crew members.”

The low sodium effort is part of a two-and-a-half-year project. In the meantime, astronauts are probably better off leaving their liquid salt packets in the pantry.

And don’t even ask about the veggie lovers’ pizzas.

Explore these great links to learn even more about space food:

How Food Preservation Works

How Space Food Works

How Space Stations Work

How do astronauts eat in space?

How does going to the bathroom in space work?