Building a working rocket engine is one thing, igniting the engine in a stable and repeatable way is an engineering feat in itself. Anyone who has been stuck in a car that won’t start knows the frustration, but once started an engine will generally tend to run. This is because the off-state of an engine is completely different to its on-state, and getting the process running requires adding energy to start combustion in the engine.

As Europe moves towards reuseable launchers, the technologies needed for igniting new rocket engines but also reigniting them during flights are being developed. The Exploration Company, based in Bordeaux, France, has shown an innovative type of ignition in action, using just the propellants themselves.