ETD

• EcosimPro
• ESA
• IXV
• priming
• RCS

The RCS is one of the major IXV functional subsystems and its main function is to perform attitude control for the vehicle during the orbital arc and to support the flap control during the autonomous re-entry. Due to the stringent ground safety requirements, three barriers are necessary before the flight to avoid unintended firing of the thrusters during pre-launch operations and ascent flight, with potential catastrophic consequences. For this reason, after the IXV separation from the VEGA AVUM, the IXV RCS has to be prepared for operation through a priming sequence in orbit.

This operation may turn out to be critical if the corresponding overpressures are not correctly taken into consideration; moreover, with the utilization of hydrazine, the priming sequence may be even more critical in relation with the phenomenon of adiabatic compression and the low threshold of the propellant thermal decomposition.

The objective of this work is to numerically investigate the priming sequences (Nominal and Off-Nominal) through the realisation of suitable models with the software EcosimPro. The analysis has been performed both for a Mock-Up (for which experimental evidences are available) and for the Flight-Hardware. Once the procedure has been validated through the comparison between the Mock-Up EcosimPro-Results and the results of the experimental campaign, the analysis has been extended to the Flight-Hardware. Both the Nominal Priming Sequence and the Off-Nominal Priming Sequence (i.e. priming via LV in case of By-Pass Line failure) have been investigated at different initial conditions (initial tank pressure and initial non-condensable gas pressure) and the criticality has been assessed.