Explosion excluded as possible cause for Progress space freighter accident — expert

MOSCOW, May 13. /TASS/. An explosion is ruled out as a possible cause for the accident with Russia’s Progress M-27M space freighter than went out of control and was burned in the dense layers of the Earth’s atmosphere, a Russian space expert said on Wednesday.

Depressurization of the oxidizer and propellant tanks of the Soyuz-2.1a carrier rocket’s third stage caused the loss of the Progress cargo ship as was established by Russia’s Federal Space Agency (Roscosmos), Academician of the Russian Academy of Cosmonautics and Cosmonautics News Journal Editor-in-Chief Igor Marinin said.

"The third stage’s tanks could not explode considering that pressure had already fallen off and the tanks were empty at the end of the stage’s operation. They could not explode due to depressurization as there was no excessive pressure there," the expert said in reply to a question about whether the "break-up of the tanks" as described by Roscosmos specialists could be called an explosion.

The expert said he agreed with Roscosmos’s version that the Progress space freighter had gone out of control due to the sequential depressurization of the oxidizer and propellant tanks of the Soyuz-2.1a carrier rocket’s third stage.

"But specialists still have to find the cause for this ‘break-up,’" the expert said.

The expert said he ruled out the version of a structural defect in the manufacture of propellant tanks.

"The [rocket’s] stage is old and has been used for a long time and there could be no such defects there," he said.

The Soyuz-2.1a carrier rocket with the Progress space freighter blasted off from the Baikonur space center in Kazakhstan on April 28. However, the carrier rocket failed to deliver the cargo ship into a designated orbit and Russia’s Mission Control lost communications with the space freighter that was intended to deliver supplies to the International Space Station.

The Progress cargo ship burnt up in the dense layers of the Earth’s atmosphere over the Pacific Ocean in the morning of May 8.

Roscosmos later said the accident had been caused by the "off-nominal separation of the third stage of the Soyuz and Progress space vehicles" as a result of the tanks’ depressurization.

The causes for the Progress space freighter accident are currently being investigated. The results of the investigation are expected to be announced on May 22.