Soyuz launch
Liftoff of the Soyuz rocket carrying the Soyuz MS-10 spacecraft Oct. 11. Credit: NASA

MOSCOW — Accident investigators confirmed that the failed Soyuz launch to the International Space Station three weeks ago was caused by a damaged sensor in the booster package, a fault attributed to the final assembly stage of the rocket at the Baikonur Cosmodrome, Oleg Skorobogatov, deputy director of Russia’s Central Research Institute of Machine Building (TsNIIMASH) told reporters here Nov. 1.

As was clear from video of the Oct. 11 launch, the flight of Soyuz MS-10 was aborted 118 seconds after liftoff when one of the rocket’s four side boosters failed to eject properly — colliding with the rocket’s second stage, damaging the lower portion of the rocket and sending the entire assembly into a spin, triggering an automated abort that jettisoned the crewed capsule.

“The cause of the abnormal separation was the lid of the oxidizer tank’s nozzle in Block D did not open due to a deformation (6-degree bend) of the contact sensor during assembly of the package at the Baikonur Cosmodrome,” Skorobogatov was quoted by TASS as saying. “This was the cause of the off-nominal separation.”

The accident investigation commission says that it has developed new guidelines and checks to ensure that future Soyuz rockets do not run into similar problems, and that two launch vehicles slated for imminent launch — one at Baikonur and one at the ESA launch complex in Guiana — are being reassembled to ensure that they, too, are in working order.
With the cause of the Oct. 11 failure identified, crewed launches of Soyuz-FG launch vehicles are set to resume. The next launch is scheduled for Dec. 3. Last week, the Russian Defense Ministry demonstrated that the problem with Soyuz MS-10 was not universal when it conducted a Soyuz 2 launch from its cosmodrome in Plesetsk.

NASA didn’t comment on the specific findings of the Roscosmos investigation. “NASA is working closely with its International Space Station partner Roscosmos to move forward on crew launch plans,” NASA spokesperson Stephanie Schierholz said Nov. 1.

NASA has its own team working alongside Roscosmos to gather insight from the investigation, she said. That team will help “inform NASA’s decision on launch readiness that will be made during the flight readiness review” for the Soyuz MS-11 mission now scheduled for a Dec. 3 launch.

A week earlier, NASA Administrator Jim Bridenstine praised Roscosmos for keeping NASA informed about the investigation. “Roscosmos has been very transparent with NASA on the failed launch of the Soyuz,” he said in an Oct. 25 speech. “I am very confident with where we are that we will launch again in December and that there will be no gap in human activity on the International Space Station.”

Along with the commission’s findings, Roscosmos on Nov. 1 released a video on its social media feeds taken from the body of the Soyuz MS-10 rocket. The video runs from launch until moments after the side booster struck the rocket, knocking it off course. The video provides a previously unseen vantage point of one of the most serious launch failures in years.

Пуск ракеты-носителя «Союз-ФГ» с пилотируемым кораблем #СоюзМС10. Видео с бортовых камер

— РОСКОСМОС (@roscosmos) November 1, 2018

NASA separately announced Nov. 1 a media availability for Anne McClain, the NASA astronaut on the Soyuz MS-11 mission. That release noted she and her crewmates “are targeted to launch” Dec. 3, and will remain on the ISS until June 2019.

SpaceNews senior staff writer Jeff Foust contributed from Washington.

Matthew Bodner is a freelance journalist based in Moscow. He previously worked for The Moscow Times.