According to Mission Control Center specialists, still most possible explanation for disaster of Progress MS-04 cargo spacecraft is problem with third stage of Soyuz-U rocket. To remind, spacecraft exploded after 382 seconds of flight on December 1, 2016.
TASS news agency quotes official statement given by Mission Control Center of Roscosmos, evaluating as most possible reason for disaster of Soyuz-U cutting off propulsion of the third stage – Blok-I. RD-0110 engine fueled with RG-1/LOX, which is propulsion of Blok-I, stopped to work probably at T+6’22”, but still no reason for such anomaly has been found. Most possible explanation, mentioned in the statement of MCC, which directly supervised mission of MS-04, is emergency cut off. This could be only result of losing correct trajectory or pressure problems in combustion chamber. Theory is close to previous assumptions which appeared at Novosti Kosmonautiki forum but is not going along with previous theories (with assumed presence of foreign object in engine or problem caused by poor engine assembling quality) presented by TASS and based on sources close to Roscosmos. Still, for official statement we will have to wait until at least 20th December 2016 – special interdepartmental commission with Roscosmos director Igor Komarov as a chief, probably will work at least to this day. Work of the commission and their results are also important for Roscosmos also due the more economical reason, not only because of science curiosity or future cargo flights. As usual during space flights, vehicle and its payload (including NASA payload placed inside MS-04) was insured. But insurance also has its conditions and total sum can be paid only in certain cases. If it will discovered, that accident was caused by circumstances not covered by insurance, it may be that sum of $33 million (covered by insurance contract) will not be paid. VTB Insurance, Ltd., company which was awarded with insurance contract for both Soyuz-U and MS-04 probably is looking forward final report with even greater eagerly than Roscosmos.
As it was announced by Roscosmos, Commission started to work just after disaster. Already on December 6 members of commission along with team of specialists and engineers reached Tuva Republic to start searching for place of crash of not burned particles of Progress. Until December 6 only three parts from Progress were found and sent to RKK Energia and Progress State Research and Production Rocket Space Center for further analysis. It was announced and confirmed by Tuva Republic authorities, that all particles, which were found were not harmful. Still searching for crash site lasts and is quite complicated due the weather and environment conditions.