Proton-M Failure Due to Same Design Flaw that Doomed 1988 Mission
Russian authorities investigating the May 16, 2015 Proton-M rocket failure have determined that the root cause was a design flaw in the turbopump for the third stage steering engine and concluded it was the same root cause of a prior crash in 1988.
Igor Komarov, head of Russia's Roscosmos space agency, said today that the Proton-M third stage failed on May 16 because of excessive vibration in the turbopump. The failure destroyed Mexico's MexSat-1 communications satellite.
Alexander Medvedev, head of the Khrunichev Center, which manufactures Proton, revealed that it was the same problem that caused a 1988 Proton failure. That crash previously was attributed to a manufacturing defect that led to the destruction of a fuel line in the third stage.
The solution is to replace the turbopump shafts and mounting structures, including the use of new materials. Komarov said it was not a costly fix.
Human error was initially suspected in the May 2015 crash, and although the specific cause turned out to be a design flaw, the investigation also identified quality management and manufacturing process inconsistencies. Komarov said there would be "disciplinary and administrative measures" taken in that regard.
Anatoly Zak, editor of RussianSpaceWeb.com, explained that sensors to monitor vibration loads on the turbopump were added after a Proton-M failure precisely one year before this one. In that case, a Russian Ekpress-AM4R satellite was destroyed. Investigators determined at the time that the problem was a failed bearing. The sensors were then added to provide additional in-flight data, which made it easier to determine the cause of this crash.
The announcement in TASS likened the 2015 failure only to the one in 1988, but Deputy Prime Minister Dmitri Rogozin said on May 18 there were three Proton failures that were "exact replicas," including Ekpress-AM4R in the list. Zak reports that "under certain border-line conditions, the shaft of the turbopump tends to fail, even though, it has actually happened in just three launches of more than 400 Proton missions since 1965."
Russia has been experiencing an unusual number of launch failures of various rockets since December 2010 and other Proton crashes had other causes, so the Russian aerospace sector still has work to do to restore confidence in their capabilities. Russian officials still have not determined, for example, the cause of an April 28 Soyuz-2.1a launch failure that doomed the Progress M-27M cargo mission to the International Space Station. TASS reports that the launch of a military satellite on a Soyuz-2.1b rocket is being postponed until the Progress M-27M accident is solved.
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