Sea Launch has provided additional details about the Zenit 3SL failure that resulted in the loss of Intelsat 27, which occurred on February 1.
“11.4 seconds into flight, the Zenit flight control system detected an exceedance of a pre-programmed roll limit and responded appropriately with activation of the on-board thrust termination sequence,” reported an official Sea Launch statement.
Sea Launch, together with Energia Logistics, formed a Failure Review Oversight Board to obtain investigation reports from all contractors involved in the launch. However, Sea Launch confirmed that the rocket’s systems were functional and ready for the mission and all pre-launch operations were executed as expected.
The launch vehicle designer has identified a potential fault within the 1st stage hydraulic system, that is likely to have caused the malfunction in the Thrust Vector Control system. Russian sources specifically identified the root cause in a hydraulic pump within the first stage propulsion system. The pump, manufactured in Ukraine, provides hydraulic pressure to the gimbal mechanism controlling the engine’s nozzle. Telemetry has shown that the pump performed nominally during engine start, but early in the flight started to slow down before stopping completely. The Thrust Vector Control’s loss caused the rocket’s uncontrolled roll leading to the activation of an emergency shutdown 20 seconds after liftoff. Although the malfunction was detected 11 seconds after liftoff, the system was programmed to delay the emergency shutdown to avoid a re-entry too close to the semi-submersible Odyssey launch platform.
The launcher splashed down into the Pacific Ocean 4 km away from Odyssey. The search helicopters that were sent to the splashdown location were unable to find recoverable debris from the rocket.
The video below shows a previous Zenit launch from the mobile Sea Launch platform: