Sloshing in Space

Experiencing the effects of microgravity in space, and floating around a spacecraft is something many of us dream of. However, it is not without its problems. Without gravity pulling things down we often must rethink how certain things work in space. One great example of this is fluid in rocket engines.

Famously we have seen how fluids tend to float around the cabin of spacecraft. We have seen many images of astronauts demonstrating this phenomenon during their missions. This behaviour isn’t just seen in the cabin of the spacecraft but occurs elsewhere in the spacecraft, it even happens within the astronaut’s bodies. It’s not just the water the astronauts squirt out of pouches that float, all liquids demonstrate this behaviour, from the fuel in the tanks, to the fluids in an astronaut’s stomach.

Biological issues aside, this lack of downhill flow can provide some major headaches when building spacecraft. Building a fuel tank here on Earth is straightforward, a hole on the bottom of a container will funnel fuel into the engine without too much extra work. In microgravity, this fuel can float away from the engines and where it is needed.  There are various traditional methods that are currently used to try and overcome this issue. These range from sponges and screens to channels and vanes to help guide the fluid to where it needs to be. The issue with these methods is they are often based on mechanical systems. These are susceptible to breakdowns which can jeopardise space missions.

To counteract these risks scientists have been working on a fluid repelling coating for the inside of their tanks. The theory behind this, is that if the walls repel the liquid it will bounce around until it bounces to the bottom of the tank where there will be no fluid repelling coating and it will stick.