As an overall conclusion of the HYPROGEO project, we can validate the completion of the project objectives, which were first to study a new cost-effective subsystem for access to space using hybrid chemical propulsion technology and confirm the benefits as a complementary and cost-effective alternative to classical bi-liquid chemical engines and all-electric propulsion. The second objective focused on providing significant scientific progress and increase the European excellence and know-how in critical technologies and components of an operational hybrid propulsion system, in all 4 technical challenges
1st Challenge: Achieve high specific impulse
− Fuel selection compatible with space applications and providing the highest theoretical ISP
− Combustion efficiency with low regression rate
− Optimization of catalyzer and increase of HTP concentration
2nd Challenge: Sustain long duration burn with medium thrust
− Duration of burns
− Thrust stability
− Thermal protection (nozzle and combustion chamber)
− Geometrical arrangement of the fuel for long duration burns and constant performance with time
− Compatibility with oxidizers.
3rd Challenge : Demonstrate the feasibility of using High concentration HTP
− High concentration issues (production, storage, decomposition, safety of operations)
− Compatibility with material and subsystems (lifetime of tanks)
4th Challenge: Integrate the hybrid propulsion within operational spacecrafts and confirm the economical and Technical effectiveness
− Confirmation of cost impact and reduction of design complexity
− Accommodation of the hybrid propulsion modules within the spacecraft
− Geometrical arrangement of tanks
− Reaction control thrusters
− Trade-off between upper stage and apogee engine scenarios.
Analysis of the assets of hybrid propulsion in HYPROGEO’s target of long duration and stable firings leaded to the definition of a preferred application as an independent kick-stage module compatible with full or partial geostationary transfer of geostationary satellites.
One of the interesting impacts identified by the WP1 activities was the identification of the best compromise in terms of performance management at satellite level between the kick-stage chemical propulsion (to quickly raise the orbit since its injection from launcher), and the electric propulsion on-board the spacecraft. This optimization search aims to increase the satellite operational lifetime (with the maximization of Xenon mass where in geostationary orbit) without leading to over-constraining durations currently encountered with full electric propulsion transfers.
Positive impacts have been demonstrated in all technical domains as first exploitable results are currently being disseminated, from an innovative isochoric combustion chamber concept for long duration and constant thrust, a high-temperature and low-erosion material development for a high endurance nozzle, a very performing test of a long duration catalytic bed using 98% HTP (European first), and development of a HTP production plant of up to a top-level concentration over 98%.
Lastly, the competitive positioning (SWOT) of hybrid engines was analyzed from the technical perspective. Hybrid engines are simpler, safer, and cheaper than chemical or electric ones. In terms of ISP and thrust, they provide an interesting in-between alternative to chemical and electric engines.
