Zenit-3SL accident may result from onboard power source failure

The failure of the first-stage on-board power source might have caused the abortive launch of a Zenit-3SL rocket on February 1, a source close to the investigative commission gave the tentative information to Interfax-AVN on Tuesday.

"It was clear on the very first day that the power source caused the accident. Yet we have to wait for an official opinion of the investigative commission, which will be announced within days," the source said.

"Ten seconds before liftoff contact, the onboard power source starts rotating and pressure is created for actuator drivers," he said.

"The ignition comes four seconds before the liftoff contact. The on-board power source filled with helium raises the pressure to 150 atmospheres and the actuator drivers start working. One and a half seconds after the takeoff ,the engine gains momentum, the helium stops flowing in and kerosene takes its place," the source said.

"The on-board power source is a turbine pumping either gas or liquid. It is tested with nitrogen on the ground and helium is used in the takeoff. One and a half seconds after the launch, the on-board power source shuts down and kerosene flows in [the turbine combustor]," the source said.

"The turbine started running on kerosene but shut down in less than a second (0.8 seconds)," he said.

"Combustors were set to focus the flame during takeoff. The rocket started rising from the launch pad and elevated by several meters. The combustors were set to the working position but the pressure was lost, the combustors lost control and the rocket deviated from the designated trajectory," the source said.

"Then the control system ordered the emergency shutdown of the engine but the shutdown did not happen for 20 seconds. The delay was programmed to take the rocket away from the launch platform. The rocket lifted off by two kilometers and moved approximately 2.6 kilometers away from the launch platform before it crashed into the Pacific," he said.

The Intelsat-27 satellite was lost in the Zenit-3SL accident.

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