Test Activities on Hybrid Rocket Engines: Combustion Analyses and Green Storable Oxidizers—A Short Review

Hybrid rocket engines (HREs) offer a low-cost, reliable, and environmentally friendly solution for both launch and in-space applications. Hybrid propellants have been identified as green thanks to their use of non-toxic, non-carcinogenic oxidizers. Of particular relevance are storable oxidizers, namely high-concentration (≥90 wt.%) hydrogen peroxide (HP, H2O2) and nitrous oxide (N2O). This work provides a survey of experimental activities based on H2O2 and N2O for hybrid rocket propulsion applications. Open literature data are completed with original thermochemical calculations to support the discussion.