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Investigation finds cause of Russian cargo ship failure

Anatoly Zak, Spaceflight Correspondent
Jun 2, 2015, 15:34 UTC

Sen—The cause of last month's Progress cargo ship failure has been identified, the Russian space agency, Roscosmos, announced on Monday.

The technical problem led to the loss of the Progress cargo ship which was loaded with supplies for the International Space Station (ISS).

A press release published by the agency on Monday stated that, "after a thorough analysis of the failed launch and full-scale experiments, the State Commission investigating the April 28 accident concluded that the damage to the ship during its abnormal separation from the third stage of the Soyuz-2-1a launch vehicle resulted from a particular property of the stack including the spacecraft and the rocket."

Roscosmos said that "these properties were related to frequency and dynamic characteristics of joint vehicles," without providing any additional details. The wording of the press-release possibly referred to some resonance effect (vibration), which could damage the spacecraft.

The agency added that such a property was not fully accounted for during the development of the rocket and spacecraft complex. "Limitations on further flights of the Soyuz-2-1a rocket with other spacecraft had not been found. Currently, Roscosmos is developing an action plan for conducting further flight tests of this space complex," the announcement said.

The botched mission on April 28 was the second attempt to launch a Progress cargo ship on the Soyuz-2-1a rocket. The first launch on October 29 went seemingly without a hitch. All other Progress missions have been carried into orbit by a slightly less powerful Soyuz-U rocket.

Roscosmos did not say whether dynamic conditions during the failed ride were any different from the first successful Progress mission on the Soyuz-2-1a rocket.

The agency promised to finalise the new flight manifest for both crew and cargo by June 9.

The seven-ton Progress M-27M lifted off from Baikonur Cosmodrome in Kazakhstan on a mission to deliver propellant, water and other supplies for the 43rd long-duration expedition on board the ISS. However moments after the separation from the third stage of the launch vehicle in the initial parking orbit, communications between the mission control in Korolev near Moscow and the spacecraft suddenly faltered. The spacecraft was later found tumbling in space and all attempts to stabilize it failed. The stranded ship harmlessly reentered Earth's atmosphere on May 8.

Four days later, the State Commission led by Deputy Head of Roskosmos Aleksandr Ivanov presented its preliminary conclusions on the accident. According to the agency's press-release published at the time, investigators "came to a preliminary conclusion that a version of the abnormal separation had been objectively confirmed, which included two subsequent events related to the depressurization (disintegration after the cutoff of the third-stage engine) first of the oxidizer tank and then of the fuel tank."

The agency also said at the time that "the work of the Commission had been ongoing and that the final classification of the character of the root cause leading to the failure would require in-depth calculations and theoretical studies, an additional simulation and a number of experimental works."