No root cause identified as Arianespace sets timetable for returning Vega to flight following $415 million failure
WASHINGTON — Arianespace plans to return the Vega light-lift rocket to flight by the end of March after unspecified actions are taken to prevent a repeat of the July 10 launch failure that destroyed the UAE’s Falcon Eye-1 optical imaging satellite.
The Emirati satellite was insured for about $415 million, making Vega’s failure the space insurance industry’s largest single loss to date.
Preliminary findings issued Sept. 5 by a European Space Agency and Arianespace-led commission said investigators are still not exactly sure what caused Vega to break apart 130 seconds after liftoff, but are confident they’ve isolated the problem to the rocket’s Zefiro-23 second stage.
Specifically, investigators think Vega’s failure originated in the forward dome area of the Zefiro-23, the second of three solid-fueled stages the rocket expends to deliver satellites to orbit.
In an interview, Giulio Ranzo, CEO of Vega-manufacturer Avio, said that while the commission was not able to pinpoint the precise cause of the failure, careful analysis points to “thermo-structural failure” of the Zefiro-23’s forward dome area.
“It’s very confined in scope, the area it occured,” Ranzo told SpaceNews. “We know where to act with corrective measures to reduce significantly the risk that this could ever happen again.”
Ranzo said the commission evaluated other possibilities, such as the inadvertent trigger of the rocket’s self-destruct system, but deemed them all extremely unlikely. The commission also ruled out any “malicious act” as a probable cause.
Vega lifted off on the ill-fated flight VV15 from Europe’s Guiana Space Centre on July 10 at 9:53 p.m. local time. After the rocket jettisoned its P80 first stage following a nominal start to the mission, the Zefiro-23 booster ignited as expected and fired for 14 seconds, the commission said, before a “sudden and violent event” caused the rocket to break into two main pieces: the Zefiro-23 and the rocket’s upper half consisting of the Zefiro-9 third stage, a liquid-fueled AVUM upper stage and a payload fairing with Falcon Eye-1 still inside.
At 213 seconds, range safety officials sent a neutralization command to what was left of the rocket. At 314 seconds, telemetry ceased.
The commission recommended Avio and Arianespace, which markets and operates the rocket, undertake “an exhaustive verification plan of its findings based on analyses and tests” and implement “a set of corrective actions on all subsystems, processes and equipment concerned.”
Ranzo declined to specify the corrective actions Avio and Arianespace will take before returning Vega to flight. He said development of Vega’s successor, the more powerful Vega C, won’t be affected by the rocket’s only failure in 15 launches. In designing Vulcan C, Avio replaced the Zefiro-23 with the wider and slightly longer Zefiro-40 second stage.
Prior to the launch failure, Avio pushed Vega C’s debut from 2019 to March 2020 to accommodate a total of four launches of the current-generation Vega this year.
Arianespace’s plan to return Vega to flight between January and the end of March pushes two of those planned 2019 missions — the launch of the UAE’s Falcon Eye-2 satellite and a dedicated rideshare mission carrying 42 tiny satellites — out to 2020, and will likely affect the maiden flight of Vega C.
Arianespace spokesperson Isabelle Veillon said the company would give an update on its manifest at the World Satellite Business Week Conference in Paris the week of Sept. 9.
Vega, the newest vehicle in the Arianespace launch family, had flown 14 consecutive successful missions between its 2012 commercial debut and its failure in July. The rocket is designed to carry smaller payloads, ranging from numerous cubesats up to single satellites weighing around 1,500 kilograms.
In a news release, Arianespace CEO Stéphane Israël said Arianespace and Avio “will be doing everything in our power to reconnect with the 14 successful launches already recorded by our light launch vehicle.”