Rocket Factory Augsburg is developing a launch vehicle that uses oxidiser rich staged combustion engines. The Helix engine is ignited with a single-shot hypergolic ampoule containing TEA-TEB. The goal for RFA is to be able to re-light the Helix engine in flight, making it possible to recover the first stage, and to extend the payload capabilities of the second stage. In order to achieve this, its single-shot ignition system has to be modified to allow for multiple in-flight ignitions. This thesis covers the modelling of the ignition fuel flow, a trade-off between existing re-ignition options for hypergolic ignited engines, and sizing of a re-ignition system for the current Helix engine.