Russia Identifies “Design Peculiarity” as Cause of Progress Launch Failure

Progress_vehicle_freeflight
Roscosmos says it has identified the cause of the launch failure involving a Progress resupply ship last month:

The loss of a Russian Progress spacecraft that started spinning out of control shortly after its April 28 launch is being blamed on an unexpected interaction between the spacecraft and the upper stage of its Soyuz rocket, the Russian space agency Roscosmos said June 1.

In a statement, Rocosmos said a “design peculiarity” between the Progress M-27M spacecraft and the upper stage of its Soyuz-2.1a rocket led to the accident. The statement did not discuss in detail how that design issue caused the accident other than citing the “frequency-dynamic characteristics of the linkage” between the spacecraft and upper stage.

The launch of the Progress started off normally, with the spacecraft appearing to separate into its planned orbit and on a trajectory to dock with the International Space Station six hours later. However, shortly after reaching orbit, the spacecraft went into a slow roll. Roscosmos deferred the docking to April 30, then canceled it entirely.