An anomaly in a Proton Breeze M upper stage engine’s oxidiser supply system caused a premature shutdown resulting in the incorrect orbiting of the Arabsat 4A satellite on 28 February, says the Russian state commission investigating the mishap.
Telemetry data suggests the most probable cause of the oxidiser supply interruption was a foreign particle blocking a booster hydraulic pump nozzle. The commission is developing corrective actions for additional inspections of Breeze M and Breeze KM main engines, which are of the same type, to prevent a recurrence. The Arabsat 4a launch was provided by International Launch Services (ILS), which markets Proton and Lockheed Martin Atlas rocket launches.
ILS’s own failure review oversight board will now hold meetings in Moscow to discuss the commission’s findings. “The [board] will review the final report and corrective action plan in accordance with US and Russian government technology control regulations, with a goal of completing its work by the end of May,” says ILS. Proton flight operations could resume after the corrective actions have been implemented, which is expected to be by the end of May.
The commission reviewed all possible failure scenarios based on telemetry data, and conducted verification tests, including firing main engines.
Launched from Baikonur Cosmodrome on 28 February, the ILS Proton M launcher inserted the Breeze M upper stage, with the satellite, into the proper orbit. But at 92min after lift-off an unplanned main engine shutdown occurred during the upper stage’s second burn. This triggered a flight control system emergency command and the Arabsat 4a satellite was separated from the upper stage, into an incorrect orbit of 51.5º inclination, 14,680km (9,120 miles) apogee altitude and 506km perigee altitude.
Source: Flight International
