Nozzle erosion blamed for Vega C launch failure

WASHINGTON — Europe plans to return the Vega C rocket to flight by the top of the 12 months after concluding an eroded nozzle element brought about the failure of its earlier launch final December.

The European Area Company introduced March 3 it had accomplished an unbiased investigation into the failed Dec. 20 launch of the Vega C on the VV21 mission, which skilled a lack of thrust from its Zefiro-40 solid-fuel second stage. The failure resulted within the lack of two Pléiades Neo imaging satellites for Airbus Defence and Area.

The investigation concluded {that a} element within the motor known as a throat insert, product of carbon-carbon materials designed to face up to excessive temperatures, suffered “thermo-mechanical over-erosion” throughout the launch. That insert regulates the move of exhaust by means of the nozzle, and because it eroded the chamber stress dropped, inflicting thrust to lower.

By 207 seconds after liftoff, or a bit of greater than a minute after the second stage ignited, acceleration of the car grew to become “quasi-null” and put the rocket on a ballistic trajectory, mentioned Pierre-Yves Tissier, chief technical officer of Arianespace and co-chair of the unbiased investigation, in a briefing concerning the report. A fault tree evaluation led investigators to rule out different causes of the failure.

The erosion of the insert, he mentioned, was linked to greater porosity of the carbon-carbon materials, confirmed in different testing of the fabric however not detected earlier. “The acceptance standards established for this materials weren’t in a position to detect such a weak spot,” he mentioned.

Avio procured the throat insert from a Ukrainian firm, Yuzhnoye. Giulio Ranzo, chief government of Avio, mentioned the corporate went with Yuzhnoye throughout the design part of Vega C in 2015 to 2017 after concluding that different European suppliers couldn’t present the fabric in required portions “on the schedule suitable with the event program” of the rocket.

The flaw, he mentioned, was indirectly linked to disruptions brought on by Russia’s invasion of Ukraine a 12 months in the past as a result of they have been manufactured earlier than the battle. He recommended that lockdowns linked to the pandemic may need been an element, although.

The erosion was not seen within the Zefiro-40 motor used on the inaugural Vega C launch final July, or in two earlier qualification firings. “The acceptance standards weren’t the best ones,” mentioned Giovanni Colangelo, ESA inspector basic and the opposite co-chair of the investigation. In these earlier firings of the motor, the supplies exceeded necessities.

“The one for VV21 was precisely according to specification, so have been inferior to the earlier one, so that’s the reason why there was a failure,” he mentioned.

The investigation concluded that the Yuzhnoye materials can now not be used on the Zefiro-40 motor. It will likely be changed with a carbon-carbon throat insert from ArianeGroup, which already produces related parts for motors used on different Vega levels.

Ranzo mentioned that Avio had already bought a number of such throat inserts from ArianeGroup final 12 months as a hedge in opposition to potential provide chain disruptions brought on by the battle in Ukraine. “We have now secured the following a number of flights by having procured this strategic inventory a number of months in the past,” he mentioned, including that Avio was longer-term choices for the element from ArianeGroup or others.

ESA mentioned that further evaluation and testing of the Zefiro-40 is deliberate for the approaching months, permitting a return to flight of the Vega C tentatively scheduled for late this 12 months. The payload for that mission would be the Sentinel-1C radar imaging satellite tv for pc.

“Sentinel-1C is certainly a really treasured payload,” acknowledged Josef Aschbacher, ESA director basic. That satellite tv for pc will exchange Sentinel-1B, whose radar payload failed last year. “We’re placing measures in place that are very sturdy and we’ve confidence this can all succeed.”

The Zefiro-40 drawback doesn’t have an effect on the unique Vega rocket, which makes use of a distinct motor in its second stage that doesn’t have a throat insert from Yuzhnoye. ESA plans a launch of that rocket, one in all two remaining of that model, earlier than the top of the summer time.

Stéphane Israël, chief government of Arianespace, mentioned that Vega launch will carry two major payloads and a number of other smallsat rideshares. “We’ll give extra info on these passengers in a couple of weeks,” he mentioned.

Along with fixing the issue with the Zefiro-40, there will likely be a broader evaluation of the car’s provide chain to search for different potential high quality points. “We’ll attempt to enhance considerably the monitoring of the efficiency and provide chain administration actions,” Ranzo mentioned.

Each ESA and Arianespace management expressed some frustration with the Vega program, noting that the VV21 failure was the third in eight flights of the Vega and Vega C. They’re additionally coping with delays with the event of the Ariane 6 which have pushed its first launch again to not less than late 2023, in addition to the lack of the Soyuz rocket after Russia’s invasion of Ukraine.

“We’re in a disaster,” Aschbacher mentioned. “For me, that is actually a second the place we have to replicate deeply tips on how to regain unbiased entry to area for Europe.”


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