Failure evidence and return to flight

The original Vega’s VV15 failure in July 2019 involved the Zefiro-23 second stage. ESA described hot gas entering through its forward dome and the vehicle breaking up. The later Vega-C VV22 loss in December 2022 involved the Zefiro-40 nozzle: the inquiry identified excessive erosion of its carbon-carbon throat insert and questioned the sufficiency of the material acceptance criteria.

These accounts identify different hardware and mechanisms. A useful comparison begins with flight, configuration, component and evidence. Saying only that “the second stage failed” loses the distinction needed to assess corrective work. Neither event should be assigned to the other simply because both vehicles carry the Vega name.

A modified Zefiro-40 suffered nozzle damage during a June 2023 ground firing. The subsequent inquiry found that the new insert material’s properties interacted with the nozzle geometry and damaged adjacent parts. It explicitly distinguished this mechanism from VV22. Recommendations included redesign work, better-calibrated models and further firing tests.

This provides a general engineering lesson: replacing a suspect material does not automatically qualify the surrounding assembly. In an original classroom analogy, a replacement fitting may withstand heat better on its own but expand differently from its housing. Testing the assembly can reveal a problem that a material certificate alone cannot settle.

Keep the investigation evidence separate

Vega-C returned to flight on December 5, 2024, placing Sentinel-1C in orbit. CNES documented that completed launch. The result adds important flight evidence after the redesign and test effort; it does not erase the earlier failures or guarantee every future mission. The course deliberately separates historical outcomes from predictions.

An original review table can use four columns: observed problem, proposed correction, verification evidence and remaining limits. A static firing exercises selected conditions on the ground; an orbital mission tests a broader flight sequence. Neither should be described as proving conditions it did not exercise. The strongest explanation connects each claim to its actual evidence.