Inquiry finds Vega failed after violent event during early second stage flight

by Chris Bergin

Arianespace has published the findings from an Independent Inquiry Commission tasked with analyzing the failure of Vega Flight VV15. Vega failed during the launch of the Falcon Eye-1 satellite in July. The overview concludes the second stage failed 14 seconds into its burn, via a sudden and violent event via a “thermo-structural failure in the forward dome ” resulting in vehicle breakup.

Vega had a flawless launch record ahead of the VV15 flight, with 14 successes as Arianespace’s small launcher tasked with dealing with customer demand outside of its Ariane 5 and Soyuz launch contracts.

Falcon Eye-1 was its 12th Earth observation mission, the first of two spacecraft for the United Arab Emirates’ FalconEye satellite system.

Vega’s launch appeared nominal, with the first stage booster firing the rocket and payload from the ELA-1 pad at the European Spaceport in French Guiana.

The first stage’s P80 burned for one minute and 54 seconds, propelling the rocket to a velocity of 1.78 kilometers per second (3,980 miles per hour) and an altitude of 53 kilometers (33 miles, 29 nautical miles).

The first stage separated at burnout, with the second stage supposed to ignite its Zefiro 23 motor almost immediately for what was supposed to be a one-minute, 43-second burn.

Views from the live webcast didn’t appear to show the second stage lighting up, although this has since been revealed to the fault of the views attained by the long-range cameras. It was flagged as a worry soon after controllers started to move to their phones and appeared concerned at the status of the launch.

It is now known the staging and ignition of the second stage engine were nominal. However, and explaining the concern seen in the control room, in addition to the trajectory moving away from the nominal path, the second stage failed 14 seconds into flight.

This was revealed in the publication of the investigation commission’s findings, which was co-chaired by the Inspector General of the European Space Agency (ESA); and the Senior Vice President and Technical and Quality of Arianespace.

The Commission was appointed on Thursday, July 11, 2019 – tasked after having analyzed the flight data, the Commission identified possible causes for the anomaly and drew up recommendations for Vega to resume launches under the requisite conditions of safety, security and reliability.

The commission confirmed the flight was nominal through first stage, staging and early second stage flight.

“The operation of the P80 first stage (engine ignition, atmospheric phase, P80 propulsion and separation) was nominal; all parameters were as expected and in line with those from preceding flights.

“The ignition and powered phase of the Z23 stage was nominal during the first 14s 25ms and all parameters were as expected and in line with those for preceding flights.”

The rocket failed at T+130 seconds, resulting in vehicle breakup.

Vega overview – via ESA

“At 130s 850ms, a sudden and violent event occurred on the Z23 motor,” noted the investigation. “This event led to a breakup of the launcher in two main parts: the Z23; and the assembly composed of the fairing, satellite, flight adapter, AVUM and the Zefiro 9 stage (Z9). At 135s: the upper assembly trajectory started to deviate from the nominal one.”

The investigation identified the most likely cause of the anomaly was a “thermo-structural failure in the forward dome area of the Z23 motor”. It added that other possible causes, such as inadvertent activation of the Z23 neutralization system, have been found unlikely.

The goal is to now return Vega to flight in 2020, following some corrective actions.

“In the past weeks, members of the inquiry commission have done a remarkable job, with the support of the prime contractor Avio. I want to encourage all the teams to implement corrective measures for the reliable return to flight of Vega, securing Europe’s full autonomy of access to space,” noted Daniel Neuenschwander, ESA Director of Space Transportation.

The Commission has proposed: An exhaustive verification plan of its findings based on analyses and tests and a set of corrective actions on all subsystems, processes and equipment concerned.

Vega rocket ahead of launch – via Arianespace

Arianespace and ESA will hold a final review of these corrective actions ahead of resuming Vega launches next year.

“I would like to thank the co-chairs of the Independent Inquiry Commission, as well as all members,” added Stéphane Israël, Arianespace CEO. “Their work on identifying the causes of the Flight VV15 anomaly, and the well-defined actions to be carried out from now until the end of the year, will pave the way for a resumption of Vega launches as from the first quarter of 2020, under the requisite conditions of reliability.

“Along with our industrial partner Avio, we will be doing everything in our power to reconnect with the 14 successful launches already recorded by our light launch vehicle.”

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