There are so many little things about gravity that we take for granted. If you take it away, a lot of things become tougher. The common discussion points are how you lose bone density, muscle mass, you get taller, and increased risk of herniated disks. But there are a lot of day to day things that are tough too. Sleeping while having no concept of up and down, exercising without weights, eating, writing, and drinking. Generally astronauts would have to drink from bags because you simply couldn’t have a cup of water. The lack of gravity would have the water simply float away. That is, until recently….
A coffee cup that uses surface tension has made it way aboard the International Space station. The surface tension keeps the liquid inside the cup, and funnels it toward the astronaut’s face when they are drinking. The cup is able to withstand flips, vibrations, and quick movements, without spilling any liquid.
“Wetting conditions and the cup’s special geometry create a capillary pressure gradient that drives the liquid forward toward the face of the drinker,” explained Mark Weislogel, one of the team members who is a senior scientist for IRPI LLC, an Oregon-based R&D and consulting firm specializing in fluid-thermal engineering, as well as a professor of mechanical engineering at Portland State University.
“your nose is closer to the beverage, which makes it easier to actually smell it while drinking,” he added. “An astronaut can drain the cup in sips or one long gulp in much the same manner as on Earth … without tipping their head, without gravity. It’s a stable situation — even though drinking scalding liquids from open containers while aboard the International Space Station is generally considered a safety concern.”
So how did all of this come about?
When Italian Astronaut Samantha Cristoferetti went aboard the International Space station, Italy sent up an espresso machine for her. this gave a team of researchers the inspiration to study the effects of microgravity on a variety of fluids, to see how they behave. This all led to the development of the zero G cup.
“Management of water, liquid fuels, coolants, and even drinks, when the influence of gravity is negligible, is a delightful challenge,” added Weislogel. “If this can be accomplished passively, without moving parts, by special control of wetting properties, container shape, and surface tension, we’re all in. We love watching and studying the large liquid surfaces that can dominate fluid behavior in space. And if astronauts are enjoying their coffee in a richer, deeper manner than before … well, that’s nice too.”
Back on Earth, enjoy a nice cup of coffee to start your Friday, and appreciate the fact that it doesn’t float away if you aren’t careful.