Commercial launch services company, International Launch Serivces (ILS), which is part of the Russian rocket firm Khrunichev, has announced the findngs of an investigation into the 6 August failure of a Proton M flight which stranded two satellites, Telkom 3 and Express MD-2 in an an incorrect orbit. The ILS Failure Review Oversight Board (FROB) agreed with the conclusion of the Russian State Commission that the failure was caused by a fault in the Breeze-M (Briz-M) upper stage fuel system which in turn was a result of a production fault. Following this it was announced that the Proton M would be returned to flight status with the next flight of the rocket set for 14 October. This launch will carry the Intelsat 23 commercial communications satellite.
With respect to the cause of the August flight failure, after two successful firings of the Briz M Upper Stage the third firing of the engine shut down after 7 seconds instead of the intended 18 minutes 5 seconds. An investigation commission found that pressure in the Briz-M’s upper stage had fallen sharply following the vehicle’s second engine burn, causing the Proton-M rocket to spin out of control. The investigating commission further found that a small metallic orifice inside a pressurisation line that was not manufactured according to specifications caused the failure.
The faulty component was built by the subcontractor Polyot of Omsk, Russia, due to an apparent misunderstanding. The manufacture of this component had been moved from Proton M’s main manufacturer Khrunichev to Polyot in 2011. Unfortunately, the defect only showed itself under certain pressure thresholds and was thus not found during component testing. A corrective action plans including all Breeze-M (Briz-M) upper stages planned for future launches are currently being checked for the fault.