We all know that the familiar rules on Earth don’t apply in space. For instance, there is no up and no down, and the midday sky is pitch black. Of all the odd things that occur in space, the behaviour of coffee has to be one of the most peculiar.
Physics professor Mark Weislogel of Portland State University has conducted a lot of research into the behaviour of coffee in microgravity. Pouring the coffee into a cup would be the first stumbling block, he says, as there is no pull of gravity. Then, presuming you’ve managed to get the coffee into the cup, you probably wouldn’t be able to sip the coffee from the cup. “You’d have to shake the cup toward your face and hope that some of the hot liquid breaks loose and floats toward your mouth,” says Weislogel.
Coffee is not the only liquid that “misbehaves” in space. Cryogenic fuels, thermal coolants, potable water and urine do it, too.
To develop a better understanding of fluids in microgravity, Weislogel and colleagues are conducting the Capillary Flow Experiment on board the International Space Station.
For instance, one of the devices in their experiment suite looks at “interior corners”. If two solid surfaces meet at a narrow-enough angle, fluids in microgravity naturally flow along the join — no pumping required. This capillary effect could be used to guide all kinds of fluids through spacecraft.
Weislogel and colleagues have already been granted three patents for devices invented as a result of their work, one of which is for a low-gravity coffee cup.
Basically, one side of the cup has a sharp interior corner. In the microgravity environment of the space station, capillary forces send fluid flowing along the channel right into the lips of the drinker.