Progress Launch: Russia successfully resumes Soyuz booster flights to the ISS

Russia’s space agency Roscosmos has successfully returned the venerable Soyuz booster to flight via the launch of the Soyuz-U booster carrying the uncrewed Progress M-13M/45P resupply spacecraft to the International Space Station (ISS). The launch is the first successful Soyuz booster flight to the ISS since the 24th August failure of the Soyuz-U booster carrying the Progress M-12M/44P spacecraft.

Previous failure:
Following the 24th August liftoff of the Soyuz-U booster carrying the Progress M-12M/44P resupply spacecraft to the ISS, the booster’s third stage unexpectedly shut down shortly after ignition, causing the third stage with attached Progress spacecraft to fall back to Earth and disintegrate in the atmosphere.

The failure could not have come at a worse time for the ISS, with the workhorse Space Shuttle having been retired only the previous month, and commercial resupply spacecraft still engaged in preparations for their debut launches to the station.

While the loss of supplies from Progress M-12M wasn’t a huge concern to the ISS due to the “heavy” delivery of cargo by the final Space Shuttle mission in July, more concerning was the fact that the third stage of the Soyuz-U booster used to launch unmanned spacecraft to the ISS shares a lot of commonality with the third stage of the Soyuz-FG booster used to launch crews to the station.

Following the launch failure, all Soyuz boosters were grounded pending an investigation, a move which forced delays to other crew and cargo flights to the ISS.

With impressive speed, a Russian commission quickly determined the cause of the failure to be a blocked fuel line leading to the gas generator in the Soyuz-U third stage’s RD-0110 engine. The blocked fuel line caused a loss of pressure in the gas generator, which in turn caused a shutdown of the RD-0110 engine’s turbopump, leading to a total loss of thrust.

While the blocked fuel line was attributed to a random, one-off event caused by human error in vehicle processing, all Soyuz third stages were ordered to be sent back to their assembly plant for through testing. With the tests confirming that the previous defect was indeed a one-off, Russia cleared the Soyuz booster for resumption of flights.

In order to prevent a re-occurrence of the defect, numerous new safety measures were implemented, including video cameras to record all stages of Soyuz booster assembly.

Numerous Russian media reports have cited ageing workforces, poor salaries, and a lack of investment as causes for the decline in the quality of the usually highly reliable Soyuz booster, which has completed well over one-thousand successful flights.

Fallout from the failure:
The largest concern resulting from the launch failure was that the Soyuz booster would not be returned to flight in time to launch a new crew to the ISS before the current one had to return to Earth, leading to a de-crewing of the station.

While operating the ISS in an un-crewed configuration is technically possible, it is highly undesirable due to the loss of scientific research and increased risk resulting from on-board failures, as detailed at length in previous articles on this site.