Updated at 3:15 p.m. EDT Oct. 2
PARIS — Russia’s heavy-lift Proton rocket on Sept. 28 successfully returned to flight four months after a failure, placing a Russian military satellite into geostationary orbit, the Russian space agency, Roscosmos, said.
The satellite, whose exact mission and characteristics were not disclosed, “cleanly separated from the [Proton] upper stage Breeze-M and went into the desired orbit,” Roscosmos said in a statement.
The successful flight should put Proton, which has a long list of customers waiting to launch, back into the rotation for commercial telecommunications satellite fleet operators alongside Europe’s Ariane 5 and the Space Exploration Technologies Corp. Falcon 9. China’s Long March vehicle remains sidelined for most commercial satellite missions because of U.S. regulations denying the export of U.S.-built satellites or satellite components.
Reston, Virginia-based International Launch Services, which manages commercial Proton missions, said in a Sept. 29 statement that the cause of the May failure that destroyed a Russian communications satellite was “the loss of structural integrity of a bolted interface that attaches the Stage III steering engine turbopump to the main engine structural frame.
“The loss of integrity led to an excessive steering engine turbo pump vibration environment that damaged a fuel inlet line to the oxidizer gas generator, resulting in a fuel leak. The loss of fuel led to the premature shutdown of the turbopump and loss of stage control authority and ultimately loss of mission approximately 545 seconds into the flight.”
Asked for a clarification, ILS issued a further statement saying: “The telemetry, analysis and test indicate that at least one bolt holding the steering engine turbopump to the main engine frame lost preload [became loose] at approximately 45 seconds into the 3rd stage burn. There is no indication that any of the bolts were improperly installed, nor is there any evidence of a material issue with the bolts used for this interface. The [Failure Review Oversight Board] concluded that the cause for the loss of preload was a combination of sub-optimal installation and non-robust requirements for the process of assembly and torquing of the bolted interface.”
ILS said it and its owner, Proton prime contractor Khrunichev Space Center of Moscow, are preparing for a total of up to four additional Proton launches by the end of the year, for both commercial and government customers.
Satellite fleet operator Russian Satellite Communications Co. (RSCC) of Moscow, whose large AM4R satellite was lost during the May failure, wants two Proton launches by the end of the year. RSCC launches are handled by the Russian government as part of the federal space program, not by ILS.
ILS customers awaiting launches include SES of Luxembourg and Inmarsat of London and Mitsubishi Electric of Japan, whose Turksat 4B satellite, for fleet operator Turksat of Turkey, was purchased with the launch service bundled into the contract.
Proton vehicles have been operated since the 1960s and the rocket has demonstrated the ability to launch at a sustained pace of better than one per month. But in recent years multiple workmanship issues have resulted in launch failures. Quality control malfunctions have resulted in failures originating all over the rocket, with the May failure attributed to the third stage.