If you’re a coffee lover, there’s nothing quite as enjoyable as sitting by a window and watching the sunrise, hot mug of java in hand. But until recently, caffeine-loving astronauts have had to check their hot beverage sipping habits at the airlock. Despite the installation of an espresso maker on the International Space Station, and what is arguably the greatest window view in the solar system, the ISS crew has been stuck sipping beverages from a pouch. Floating spheres of scalding hot liquid are an operational hazard.
That may change with the invention of a new coffee cup by mechanical engineering professor Mark Weislogel and his team at Portland State University. In this video from NASA, Weislogel describes how the unique geometry of the cup—it looks like the offspring of a demitasse and a gravy boat after a topological deformation—takes advantage of surface tension to keep hot liquids from floating free. Normally overwhelmed and masked by gravity on Earth, Weislogel says surface tension and capillary forces create a gradient such that when astronauts puts their lips to the cup, the liquid inside is driven into their mouths. ISS crew members are seen passing cups filled with hot coffee to one another, the vessels tumbling through the air without losing a drop.
Although it cannot be denied they contribute to crew morale, space lattes are really just a proof of concept prototype. There are real challenges to designing fluid systems—such as refrigeration, or waste and fuel management—that will work when you cannot count on gravity to direct the fluid, Weislogel says. By studying how geometry can stand in for gravity and control liquids in microgravity, Weislogel and his team hope to create more reliable, passive systems necessary for long term space flight. A failure in your potable water system on the ISS means no espresso for a while—but on a voyage to Mars, it could be fatal.
