Vega-C Zefiro40 Test: Independent Enquiry
by Staff Writers
Paris (ESA) Oct 04, 2023

Following the failure of the Vega-C launch (VV22) in December 2022, an Independent Enquiry Commission drew several conclusions and made recommendations to ensure a reliable return to flight and a robust exploitation. One of the recommendations was to implement a (delta-)qualification of the nozzle with a new Carbon-Carbon throat insert material different from that previously used on the Zefiro40, the solid rocket booster of the Vega-C second stage. On 28 June 2023, a static firing test of the modified Zefiro40 engine took place at the test bench in Salto di Quirra in Italy. During the test the engine nozzle suffered significant damages.

ESA Director General Josef Aschbacher has set up an Independent Enquiry Commission chaired by the ESA Inspector General, Giovanni Colangelo, and composed of experts from CNES, ASI, ESA, Arianespace and academia to understand the cause of the test anomaly and propose recommendations.

The Independent Enquiry Commission concluded that in the current design of the nozzle, the combination of the geometry of the Carbon-Carbon throat insert and the different thermo-mechanical properties of the new material caused progressive damage of other adjacent nozzle parts and a progressive degradation eventually leading to the nozzle's failure. This phenomenon is not linked to those observed on VV22 with the previous Carbon-Carbon material.

The Independent Enquiry Commission has formulated a series of recommendations including the need to improve the nozzle design of the Zefiro40 motor, calibrate numerical models to predict the behaviour and conduct two more firing tests to verify performance with the aim to ensure a reliable return to flight and a robust commercial exploitation of Vega-C.

A task force steered by ESA and Avio has been set up and will immediately start to implement the recommendations proposed by the IEC. Vega-C, undergoing design changes of the Zefiro40 nozzle and technical reviews as well as the two firing tests, is expected to return to flight in the fourth quarter of 2024. In the meantime, another Vega flight will take place in the second quarter of 2024. A media briefing held by ESA, Avio and Arianespace took place on 2 October to detail findings and answer questions.

ESA considers the return to flight of Vega-C a strategic priority to secure Europe's independent access to space and will support the necessary efforts drawing from already available resources.

Avio in its role as Design Authority is committed to fully implement the recommendations of the Independent Enquiry Commission and is responsible for the return to flight of Vega-C.

ESA, as launch system qualification authority, Avio, as design authority and prime contractor of the Vega launcher and Arianespace, as launch service provider, will continue their joint efforts to achieve the common objective of a robust exploitation of the Vega launch system, for the benefit of their institutional and commercial customers.

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