Reasonable testing of hypergolic fuels

The paper presents the results of drop tests performed to measure ignition delay for ionic liquids under various experimental conditions. Factors that strongly affect correct determination of ignition delay are indicated. Processes preceding ignition upon contact between various quantities of a fuel and an oxidizer are explained. It is argued that well-defined experimental conditions are required to ensure correct comparison when using benchmark fuels. •Differences in measured ignition delay for ionic liquids are analysed.•Drop tests must be performed under well-defined conditions.•Modified drop test provides an adequate characterization of ignition.•Results are used for comparison against benchmark fuels, such as hydrazine.