Staying Cool in Outer Space

A heat pipe transfers heat between two surfaces by evaporating liquid at one end and condensing it at the other. The pipes don’t involve any prone-to-failure mechanical parts, nor require any power, so they are important cooling components in spacecraft for long-distance missions. But experiments on the International Space Station now indicate that the cooling devices behave in a surprising way in the absence of gravity. The results reveal that the device’s performance, such as how fast it can transfer heat, is limited by different mechanisms in space than on Earth.