‘The fifth and sixth tests of the hybrid rocket engine demonstrated the successful operation of the key design features and confirmed the viability of the chosen engine concept. During the tests, a stable combustion process was maintained, with no critical structural failures, and the oxygen supply system and nozzle assembly operated as predicted, enabling a large volume of experimental data to be gathered for further design optimisation.

Analysis of video recordings, temperature characteristics, flame shape and pressure dynamics confirms the establishment of a fully-fledged operating mode for the engine. Following an initial unstable phase, there was a gradual increase in combustion intensity, with maximum thermal and energy output occurring during the middle phase of the engine’s operation. Reconstruction of the hidden portion of the pressure diagram using mathematical interpolation indicates that a peak thrust of approximately 110–112 kgf was likely achieved, which exceeds the upper measurement limit of the sensor used.

Mathematical modelling has shown that, when the engine is used on a civilian sounding rocket with a mass of approximately 60 kg and a casing diameter of 205 mm, the calculated vertical flight altitude, taking aerodynamic drag into account, could be around 20 km, and, under favourable conditions, within the range of 18–22 km. The results obtained confirm that the design has sufficient energy potential to carry out high-altitude atmospheric sounding missions.

At the same time, the tests have identified the main area for further improvement of the engine. The most significant shortcoming remains the excessively long time taken to reach maximum thrust. The actual attainment of a thrust level of approximately 60 kgf did not occur until the 91st second, which is considerably later than the desired launch profile for the launch vehicle and significantly limits its practical applicability as a launch engine.

The main objective of the next stage of research and development work is to reduce the time taken for the engine to reach start-up thrust to approximately 10–20 seconds by optimising the mixture formation processes, nozzle geometry, flow swirl organisation, fuel charge composition and the thermal regime of the combustion chamber. At the same time, a promising area of development is increasing the maximum thrust to a level of around 200 kgf whilst maintaining the stability of the combustion process, structural strength and acceptable thermal loads. Achieving these parameters will lay the foundations for the transition to the next generation of civil sounding hybrid launch vehicles with significantly higher flight performance.