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Ariane 6 anomaly ‘will have no consequences’ for upcoming missions

Ariane 6 anomaly ‘will have no consequences’ for upcoming missions

Source: CNES/ESA/Arianespace-ArianeGroup/Optique Vidéo CSG/S.Martin-P.Piron

During the inaugural flight of Europe’s Ariane 6 rocket, an anomaly occurred resulting in two mission payloads not being successfully deployed.

The inaugural Ariane 6 mission was launched on July 9 at 21:00 CEST from the Guiana Space Center. After just one hour of flight, three payload separation events were successfully completed in just nine seconds. Then, the fourth and final payload separation event was expected to occur almost four after liftoff after a deorbit burn that would have placed the upper stage on a trajectory to burn up in Earth’s atmosphere. Two of the payloads were small return capsules that could not perform their own deorbit burns, hence the unusual deployment sequence.

Just before the two-hour mark of the mission, it became clear that the rocket’s upper stage had deviated from its planned mission profile, failing to gain altitude. Commentators on the ESA broadcast confirmed the deviation, citing a problem with the second APU ignition.

The APU is used to pressurize the rocket’s upper tanks to allow the Vinci engine to be restarted in orbit, providing a constant supply of fuel. The APU also provides a small amount of thrust, contributing to the rocket’s maneuverability and precision during its mission.

After two hours and fifty minutes of flight, ESA ended its mission broadcast, making it clear that the final deorbit launch had not been successful.

During a post-launch press conference, Martin Sion, CEO of ArianeGroup, revealed that the APU initially fired up before suddenly stopping. Without the APU, the rocket was unable to restart the Vinci engine a second time to complete the deorbit burn. Sion added that stage passivation had been successfully initiated. Passivation refers to the process of removing stored energy from a vehicle to reduce the risk of a high-energy release (such as an explosion or fragmentation) that could create unwanted orbital debris.

In a November 2021 post, ArianeGroup said an example of the APU’s versatility is “its ability to deorbit the stage at the end of the mission in compliance with European space law by propelling it towards Earth to burn up upon atmospheric reentry.” Still, Sion apparently didn’t think the mission’s upper stage deorbit failure was all that significant.

“It’s clear that many upper stages are still in orbit and take several years to return, depending on the orbit. So this is not an exceptional situation.” He added: “This is something that poses no greater risk than what happens with the vast majority of launchers.”

Sion tried to downplay the impact of the anomaly even further, stating that it occurred during the “demonstration phase” of the mission. According to the ArianeGroup CEO, this phase of the mission was intended to study how the upper stage behaves in microgravity and how different systems operate in this environment.

“So we were very clear from the beginning that there were two aspects. One was to demonstrate launch success, which we did. And then to understand and gather as much information as we could in this microgravity phase.”

While European Spaceflight cannot confirm without a shadow of a doubt that this distinction was not clear “from the start”, it is clear that the official ESA mission statement, which was published before the launch, does not distinguish between the two mission phases described by Sion. The mission’s “Launch Timeline” also does not specify the different flight phases.

What’s next for Ariane 6?

According to ESA, data from various ground stations detailing the operation of the upper stage will first need to be collected before data analysis can begin. This process is expected to take several days, with subsequent analysis to determine what happened to the APU taking one to two weeks.

While it is not yet known what happened to the APU during the inaugural flight, Arianespace CEO Stephane Israel confirmed that the investigation will not affect the rocket’s first operational launch, which is expected before the end of 2024.

“We are now on track to make a second launch this year,” Israel said. “This has no impact on future launches.”

That’s probably partly true. ArianeGroup has proven that Ariane 6 can successfully complete a standard mission profile. That allowed the company to proceed with the rocket’s next flight, which is intended to put a French spy satellite into orbit. However, the rocket may still not be able to complete its deorbit burn until the APU problem is fully understood.