Roscosmos, the Russian space agency, announced the results of the investigation on the failure of the mission of the Progress M-27M cargo spacecraft. The problem was found to be in the separation system between the spacecraft and the third stage of the Soyuz 2-1a rocket used to launch it. A new Progress mission to bringh supplies to the International Space Station could be scheduled for early July, probably using a Soyuz-U rocket, the version used until recently.
On April 28, 2015, the Progress M-27M spacecraft was launched with various supplies to the International Space Station. Immediately after separation from the third stage of the Soyuz 2-1a rocket the communications problems started and it was later discovered that the cargo spacecraft was spinning.
After a few days of attempts to take control of the Progress M-27M, Roscosmos had to admit that the mission had failed. Without control, the spacecraft fell down into Earth’s atmosphere after some days, disintegrating. The communication problems also made limited the availability of telemetry data for the investigation, which consequently was really difficult.
Initially, it seemed that the cause of the mishap was the depressurization of the third stage tanks of the Soyuz 2-1a rocket which caused a violent separation from the Progress M-27M spacecraft. Instead, the findings of the investigation indicate that the depressurization was caused by a problem in the separation.
Roscosmos statement is sparse and points to a design flaw in the separation system and to frequency dynamic characteristics associated with it. No details were given on the observed oscillations frequencies in the separation mechanism so for example it’s not clear why the launch of the Progress cargo spacecraft in October 2014, the first carried out using a Soyuz 2-1a rocket, went well.
The positive news is that the problem appears to be related to the coupling between the version of the third stage used for the Soyuz 2-1a rocket and the Progress cargo spacecraft. Roscosmos will still study potential problems that could plague the version of the third stage used in other versions of the Soyuz rocket, the U and the FG.
Last year, Roscosmos stated that the updates to the Soyuz 2-1a rocket allowed to carry up to 300 kg (about 660 lbs) more cargo than the previous versions. Presumably, until the problem is resolved, they will just carry lower cargos.
At this point, Roscosmos is also expected to announce the date for the launch of the new International Space Station crew members. They too get launched using Soyuz rockets and were therefore grounded. In their case, there should be no technical problems to further delay their launch.