According to Arianespace officials, today’s failure of their Vega rocket likely occurred because of “human error” in the installation of cables.
Engineers concluded that cables leading to thrust vector control actuators on the upper stage were inverted, apparently a mistake from the assembly of the upper stage engine, according to Roland Lagier, Arianespace’s chief technical officer. The thrust vector control system pivots the upper stage engine nozzle to direct thrust, allowing the rocket to control its orientation and steering.
The cabling problem caused the engine to move its nozzle in the wrong direction in response to commands from the rocket’s guidance system. That resulted in the rocket losing control and tumbling just after ignition of the upper stage engine around eight minutes after launch.
Lagier characterized the inverted cables as a “human error,” and not a design problem.
The next obvious question is the source of the error. The answer was not revealed, I think partly because of the number of contractors involved in building that upper stage:
The AVUM upper stage’s structure is produced by Airbus, and the Ukrainian rocket contractors Yuzhnoye and Yuzhmash supply the AVUM stage’s main engine, which consumes hydrazine and nitrogen tetroxide propellants. Avio, the Vega rocket’s Italian prime contractor, oversees final integration of the AVUM upper stage.
The goal of the investigation that will now follow will be to point that source among these contracts, and how their interaction might have contributed to it.
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