When Italian astronaut Samantha Cristoforetti came aboard the International Space Station, she brought a whole new experience to microgravity: espresso. She became the first astronaut to sip espresso made with the ISSpresso, a custom-crafted space beverage machine designed by the Italian Space Agency, the coffee company Lavazza, and Argotec, a tech manufacturer. 

Instead of drinking it out of a bag with a straw like other space beverages, this space-spresso involves 3D-printed cups that use surface tension to control the liquid. A group of researchers from NASA Johnson Space Center, Portland State University, and the Japanese space agency are presenting data on how these Space Cups have fared in their first few months of what’s called the Capillary Beverage Experiment at the American Physical Society’s annual fluid dynamics meeting this week in Boston. 

According to the research team, many of the astronauts have been most excited about the smell, which is much more aromatic than the residents of the ISS experience from drinking through a straw. "This is eerily like drinking on Earth," as one astronaut commented. 

Mark Weislogel of Portland State University explained the problems baristas in space face in a blog for NASA earlier this year:

In a normal cup of espresso, carbon dioxide bubbles release and collect to form a crema. Some of the bubbles adhere to the walls of the cup, while the remainder rise and stratify due to their size in layers we refer to as foam. Steam rises above the surface of the crema in part condensing in an advancing front on the inside surfaces of the cup. The cup cools by natural convection and the aromatics waft at rates determined by buoyancy. These processes are completely induced by gravity!

With the Space Cup, touching your lips to the cup creates a capillary connection that’s similar to the one that allows a paper towel to soak up water, wicking the liquid into your mouth. In microgravity, liquids naturally flow along narrow corners, so the cup has a sharp interior corner that guides the espresso toward the mouth. 

The fluid dynamics research that comes out of astronauts drinking from these Space Cups might eventually guide how other fluid systems—like fuel or water stores—are designed for the ISS.