NASA Cracked the Zero-G Espresso Problem
Just over a year ago, aboard the International Space Station 200 miles above earth, Italian astronaut Samantha Cristoforetti slid a plastic capsule into a machine about the size and shape of a home safe. She opened a small plexiglass door, attached a pouch of water to an intake valve, and snapped on a smaller, empty plastic bag. Then she closed the door, turned the machine on, and waited for her espresso.
We long ago solved the problem of making coffee on earth. But building an espresso machine for the space station turned out to be a much bigger challenge than the Italian engineering firm Argotec expected when it took on the project. A team of 11 engineers—7 of them working full time—spent a year and a half coming up with a brewing process that could work in microgravity and meet NASA’s rigorous safety standards. “I don’t think any of us realized that every component would have to be modified,” says Joshua Hall, an engineer who worked on the project, named ISSpresso.
To make espresso, you have to force almost-boiling water through finely ground coffee beans. In a typical pot placed on your home stove, the water at the bottom becomes less dense, creating convection currents that mix the heat into the rest of the container. When the water boils, steam pushes into the air above. But hot water behaves differently in near-zero gravity; it doesn’t rise. Even as it turns to steam, it stays put, close to the heating element. The result is a superheated, and dangerous, bubble of vapor suspended in a ball of water. Argotec’s solution was to run the water through thin steel pipes to ensure that it never builds up bubbles of heat.
But that didn’t solve the pressure problem. NASA views anything greater than 60 pounds per square inch of pressure as a safety concern, and brewing espresso requires at least twice that. To minimize the danger of a blowout, the engineers replaced the traditional rotary pump with a plunger—like in a syringe—driven by an electric motor with just enough power to do the job, and no more.
Leaks were another challenge. In microgravity, water doesn’t pool; it floats away. So every piece of piping was fitted with release valves that flush into the machine’s central chamber, which can then be mopped with a towel. The engineers also designed a mechanism to blow air through the capsule into the coffee “cup”—a zip-lock bag—clearing out liquid that could otherwise drift around the cabin.
The beans needed no reengineering. Lavazza, the Italian coffee company that led funding for the project, chose a blend of Arabica delicate enough for the American palate but roasted to produce the strong espresso that Italians prefer. The capsule, however, had to be rethought and made from a material that wouldn’t give off toxic fumes if it caught fire.
Like other space technology, the project could have earthly applications. Argotec and Lavazza have filed two patents: for an air jet that could save water at home and for the metal plunger that ejects the capsule in zero gravity, which could be repurposed in a wall-mounted espresso machine.
Space coffee may sound like a frivolity. But like music, phone calls to family, and other comforts of home, it can contribute to the psychological well-being of crew members in cramped, stressful conditions—and a crew’s well-being will only become more important as NASA explores the possibility of a manned mission to Mars. “If something as minor as a good, tasty cup of coffee can prevent astronauts from feeling alienated, isolated, or burned out, there’s just no excuse for not allowing that to be present,” says Gary Beven, chief of aerospace psychiatry at NASA’s Johnson Space Center in Houston.
Judging by Cristoforetti’s reaction, the project has been a success. After her first sip from the zip-lock bag, she flashed the camera a smile and a quick thumbs-up. Then she squeezed out a marble-size bubble of espresso and gently floated forward to catch it in her mouth.