Astronauts will bake cookies in space to see how they cook in zero gravity

To boldly go where no chocolate chip has gone before.
To boldly go where no chocolate chip has gone before.
Image: Hilton
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What happens when cookies are baked in space? Will they puff into fluffballs, or be dense fudgy spheres? Will they have crispy caramelized edges, or gooey middles? Will a lack of gravity allow us to one day make a space souffle that never collapses?

Some enterprising bakers are sending cookie dough into orbit to answer these questions and many more.

In a truly interstellar marketing ploy, the recipe—and funding—is coming from DoubleTree by Hilton. With more than 25 million DoubleTree cookies distributed to hotel guests every year, it’s a well-tested recipe that has to consistently produce the same taste and texture at hotels around the world.

But will the cookies cook the same in space? A prototype oven and a batch of frozen cookie dough are ready to launch to the International Space Station later this year so astronauts can find out.

This isn’t an entirely goofy stunt. As any pastry chef will tell you, baking is a real science. “What’s the most familiar laboratory that we have in most of our homes? The kitchen,” says Ian Fichtenbaum, co-founder of Zero G Kitchen, one of the companies attempting to make the Earthbound cookies space-worthy.

spce cookie in tray
Raw cookie dough in ZeroGKitchen’s tray.
Image: ZeroGKitchen

For example, the ratio of white to brown sugar dictates the difference between a crispy or chewy cookie, a distinction emphasized by fiddling around with sugar’s critical 356°F caramelization temperature. Egg yolks gives cookies their fudgy, gooey texture, while egg whites puff into taller, fluffier cookies. The type of fat—butter, shortening, margarine, or oil—isn’t just about taste, but also melting temperature, which dictates cookie texture. Leavens like baking soda rise dough, but they also neutralize acid to allow browning. Even cooling matters, with a quick rest on a wire rack allowing the dough to set and reduce how much the cookies crumble.

But we don’t know how all of this will work in space.

On Earth, round balls take longer to bake than thin discs—but when there’s no gravity to cause the cookies to flatten, what shape will they form? The chemical reaction of how moisture, alkali, and acid within cookie dough react when heated will still produce carbon dioxide gas—but will those bubbles spread to aerate the dough into a puffy cookie?

“We really don’t cook in space, we just warm things up or we add water to rehydrate them,” says Mike Massimino, a former astronaut who helped repair the Hubble Space Telescope. He was the first person to tweet from space, and now he’s Hilton’s space-savvy cookie consultant. “So we’re not sure how the baking process is going to work.”

The space oven in which the cookies will be baked.
The space oven in which the cookies will be baked.
Image: ZeroGKitchen

The first step toward bringing edible science into orbit is designing a zero-gravity oven. This comes with unique challenges. Most ovens on Earth rely on convection, which is the circulation of air as heat rises. “That doesn’t really happen to the same extent in zero gravity,” Fichtenbaum says. Instead, heating elements are arranged to create a pocket of heat. The cookie dough is also encased in silicone pouches to keep it from flying around.

“We really don’t know what’s going to happen,” Massimino says. “Is it going to poof up? How does gravity affect cooking?”

The questions abound. Will they be chewy or crispy? Will they be thick or thin? Will they cook thoroughly within eight to 12 minutes at 350°F, like most cookie recipes, or will the thermodynamics change? Will they even be cookie-shaped at all?

Nanoracks experiment rack
An Nanoracks experiment on the ISS.
Image: NanoRacks

“We’re thinking they will bake in a spherical blob, given they don’t have the weight of gravity on a flat tray,” says Abby Dickes, director of marketing for NanoRacks, a company specialized in supporting plug-and-play experiments on the ISS. They’ve worked with Zero G Kitchen to develop the space oven to slot into their orbiting experiment rack. “The specialty microgravity trays our engineers designed are reminiscent of a silicon baking bag, with a space twist, so we imagine the cookie expanding in all directions.”

While this is the first time fresh cookies will be baked in space, it’s far from the first space dessert. During Massimino’s missions, he used his precious tiny personal allotment from NASA to pack hard Italian sweet biscuits for a taste of home. “I brought my own stash of biscotti from Michael’s Bakery in Brooklyn,” he recalls amid a list of desserts he savored in orbit.

This brings up the next challenge that comes after baking cookies in space: eating cookies in space.

“Crumbs are a problem in space,” Massimino says, “You’ve got to be really careful.” Most space food has a slightly liquid consistency so that it sticks to utensils and doesn’t make a crumbly mess. “Something brittle like a biscotti is a real problem,” he says. “They had to be bite-size so you could shove them in your mouth and chew them so that they wouldn’t create a lot of crumbs.”

Although many Earth cookies are crumbly, these cookies have been engineered so they shouldn’t present a delicious hazard in space. “There is a filtered vent to allow steam to get out, but otherwise it’s contained so that we’re containing any crumbs,” Fichtenbaum says. The lack of crumbs is also part of the appeal of sending DoubleTree’s cookie dough, he explains, which bakes into a compact, chewy cookie. “This particular cookie tends to stay together. It’s not a very crumbly cookie.”

Those same vents that allow steam to escape will also allow the smell of freshly baked cookies to escape into the sealed Space Station, tempting astronauts to sneak a snack. But, devastatingly, taste-testing is not a part of the plan.

“Launching food that is approved for astronaut consumption is a very intensive process,” Dickes says. “This is the first time something is ever being baked from a raw state on-orbit, so there are plenty of science questions to be answered—and that’s the priority of this experiment.”

It sounds like a cruel joke that the first crew to bake and smell fresh space cookies won’t be the first to eat them. But despite the apparent cruelty of not allowing astronauts to nibble on fresh-baked cookies, even when they’re the bakers, it’s unlikely this prohibition will spark rebellion. “It’s not that NASA wants to deprive astronauts of a cookie,” Massimino says. “They want to make sure that it’s OK to eat: that it’s cooked thoroughly and that there’s no microbial problem with that cookie.”

A DoubleTree cookie at the Kennedy Space Center.
A DoubleTree cookie at the Kennedy Space Center.
Image: Hilton

But orbital taste tests will need to happen eventually, partially because everything tastes a bit different in zero gravity. “Our sense of smell is compromised a bit while we’re in space,” Massimino says. “Fluid tends to pool the upper extremities, including your head, and it makes you a little stuffy.” That means smells are weaker, leading to the popularity of stronger flavors like hot sauce and honey, particularly during space missions.

Space cookies are hopefully just the first step to freshly made desserts in orbit—and beyond. Chocolate, another Earthbound mainstay, won’t be anywhere near as easy.

“There’s a lot of science involved in making desserts,” explains Rachael McKinley, an experimental chef developing new truffles and treats for Purdys Chocolatier. She started her career earning a degree in biochemistry, but found it difficult to focus until she discovered how to apply what she was learning to developing new chocolates. “Using food as a way to understand science is what ignited passion in me,” she says.

And what better thought experiment than chocolate in space?

“We would have to completely change the way we make chocolate because we depend so much on gravity,” McKinley says. When making chocolates by hand, it needs to be poured into a mold (which requires gravity), with the excess flowing out onto paper or collected to re-melt (which also requires gravity). Fully enclosing the mold would create new problems, as chocolate needs to cool in very specific ways for a smooth texture without sugar or fat blooms. “If you have a large block of chocolate, it is never going to cool properly because all the latent heat is trapped in the center,” McKinley explains. “That part is going to crystallize incorrectly, and you’re going to have a weird white splotchy bit in the middle.”

Dessert sounds like such a triviality when confronted by all the challenges of deep space, from keeping humans alive to repairing spacecraft. But the science learned from these edible experiments explore bigger engineering questions about thermodynamics, state changes, and even the psychology of supporting humans working in isolation.

“Sometimes in our space world, we have trouble relating to the everyday person and struggle to explain why space exploration is so important,” Dickes says. “So we really have a great opportunity here to teach the world about the Space Station, why cooking in space is so important for long-term exploration, and how space-science is one of the coolest, strangest, and most important things on our planet.”

“I think it’s only the beginning. I think something like a hot pocket or Bagel Bites will be next,” Massimino says. “You don’t want to deprive people of good food.”