For the latest entry in our animated Supercluster Explains series we tackle a combustable, dependable, and highly toxic topic: Hypergolic Fuels.

Hypergolic fuels have a unique characteristic:

To burn fuel, you normally need ignition — like a match to a candle, or the spark plugs in your car. Basically you usually need a little bit of something very hot to get the fire going.

But some liquids, really volatile, toxic, corrosive ones, will burn without external ignition. You just mix the liquids together and voila — instant burning.

This is great for spacecraft because it's a reliable process. To start and stop the engine, you can just start and stop the flow of the two liquids. And you can keep them in tanks on your spaceship for years.

Just don’t touch them.