February 14, 2013 – International Launch Services (ILS) has issued additional details regarding the most probable root cause and corrective actions presented to the ILS Failure Review Oversight Board (FROB) concerning the Yamal 402 Proton launch anomaly which occurred on December 8, 2012.
 
The members of the FROB agreed with the findings of the Russian investigation that the most probable cause of the Yamal 402 Proton launch anomaly was due to a combination of adverse conditions which affected the operation of the Breeze M main engine during the startup of the 3rd burn.

The combination of adverse conditions were predominantly thermal in nature and affected the conditions at the oxidizer inlet line to the Breeze M main engine prior to the 3rd burn ignition and resulted in a large volume of oxidizer gas (rather than liquid oxidizer) at the engine inlet, exceeding the Breeze M main engine specifications. The volume of gas was ingested by the Breeze M turbopump at the start of the 3rd burn, leading to over-speed of the oxidizer turbopump bearing without the cooling normally supplied by liquid oxidizer. The over-speed damaged the bearing, which eventually led to the premature shutdown of the fourth burn. The adverse thermal conditions were due to higher than previously recorded propellant temperatures at liftoff combined with higher than previously recorded thermal soak-back of engine heat to the Breeze M prior to the 3rd burn.

Several corrective actions will be implemented, and include management of both satellite and Breeze M thermal requirements to ensure adequate margin to prevent future recurrence of this anomaly. No Breeze M hardware modifications are required.

The ILS Proton return to flight mission will be the Satmex 8 satellite for Satélites Mexicanos, S.A. de C.V. (Satmex) on March 27 (March 26 EDT) from the Baikonur Cosmodrome in Kazakhstan. The corrective actions required by the FROB to prevent future recurrence of the anomaly have been started and are currently on schedule to support the new launch date. Scheduling of the remainder of the ILS Proton near term manifest for 2013 is currently being determined.