How can astronauts drink in space? If your answer is, 'through a straw so drops don't fly off and damage the instruments around them,' then Don Pettit has proven that you're a fool. Check out how astronauts can enjoy drinks from an open container like civilized ground-people.


There's nothing like space to make us realize how much we rely on our old friend gravity. Sure it occasionally, when we lose our footing, causes the ground to punch us in the face, but that's a small price to pay for the service of keeping everything we own organized all the time. It's no fun having to clean a dropped egg salad sandwich or spilled soda off the floor. It's even less fun to clean it off the floor, the walls, the ceiling, and slowly filter it out of the air. Stuff spilled in space goes everywhere. Even the slightest detachment of fluid can leave drops that damage things. Which is why they have to drink out of bags with straws, like barbarians.

Enter the space cup. From the side it looks like a cylinder, much like a regular cup. However, when looked at from above, one side of the cylinder is pinched together, giving it the look of a tear drop. Liquid clings to itself, in a phenomenon called cohesion, and gives us things like rounded water droplets and water-scooting bugs. It also, depending on the container, clings to other things. This is called adhesion. Some containers exert a greater pull on liquids than the liquid itself does. This leads to the little curve that many people can see in test tubes, where the liquid appears to 'climb the wall' of the tube. Since the wall has a smooth, wide curve, the adhesion has little effect in a test tube. The liquid far away from the walls of the tube doesn't get pulled upwards. However the pinched together walls of the space cup are close enough that the entire surface of the liquid gets pulled up and up and up to the top edge of the cup. The lack of gravity, pulling it down, helps the liquid rise so dramatically. And once the tea is at the top, if it is sipped carefully, the cohesive force of the water and the adhesive force of the water and container keep droplets from breaking away. So enjoy watching the astronauts go wild and sip their tea.


Meniscus Image: UWPlatt

Via Physics Central.