The final phase of HIPATIA, included the assessment of the project outcomes, including the evaluation of the Technology Readiness Levels (TRLs) following the ESA TRL Handbook as a reference. In this way, Figure 9 and Table 3 show the evolution in TRL of the different units to be developed in HIPATIA, plus the HIPATIA System itself along the whole project.
The most significant advances in this regard have been achieved at System level, its first integration being already achieved in early 2021, obtaining a TRL4-5, and followed-up by the second coupling test campaign integrating the TU and PFCU EQMs and the RFGPU EM, achieving TRL5.
For the RFGPU and PFCU the progress has also being important. In the case of the RFGPU, the assembled EM is considered TRL5, but it already implements functionalities that could be considered TRL6. For the PFCU, the EQM certified TRL6. Both units are ready for a direct transition towards Qualification Models in future development phases.
The TU EM was assembled and operated already in 2020 achieving TRL5. However, problems in its operation were detected and re-design was necessary. The progress towards the EQM solved some of these issues, but not the ones related to the poor thrust performances of the device, as depicted in Table 2.
A representative of a fly unit EQM was integrated and successfully operated in the required environment (TRL6), but this is a thruster that does not fulfil the necessary requirements to perform adequately for reference missions. Therefore, the advances in the TU development have not been as expected. Before the end of the project, a new design was proposed, implementing changes that will prospectively lead to improving thrust performances. There has not been time to assembly and test this model in the frame of HIPATIA. SENER and UC3M will continue working on it and expect to have results from testing it during the first semester 2023.
Despite the current low performances, given the relatively simple and robust design of the HPT technology (no grids, neither neutralisers), HIPATIA still has the potential for providing a cost-effective solution for large constellation of small satellites (<500 kg, <750W of power for EP) to perform in-orbit insertion, station-keeping and End of Life disposal. In addition to this, air breathing Very Low Earth Orbit (VLEOs) satellites could make use of HIPATIA, since the HPT technology provides a cathodeless solution that can operate in the conditions of those orbits (electrostatic EP systems cannot operate in presence of the atomic oxygen present in those orbits).
Considering all this, the HIPATIA Partners will continue their research activities on EP beyond this project and apply the lessons learnt during it in future activities. For the HIPATIA system, all these activities will aim at enhancing the propulsive performances and try to do In-Orbit Demonstration (IOD) in the coming years.
