More details have emerged about the causes of the 24 August Soyuz-U malfunction that caused the destruction of its Progress M-12M spacecraft.
"[Russian space agency Roscosmos] have data showing that the engine was shut down due to what looks like low pressure on the fuel side. They saw data all the way down to when the vehicle broke up," according to Michael Suffredini, NASA's ISS program manager.
Exactly what caused the low fuel pressure in the third-stage RD-0110 engine is not yet known, Suffredini continued, without which no root cause can be established.
After the onboard computer commanded shutdown to The Progress spacecraft was carrying 2670kg (2.9t) of supplies on the type's 44th mission to the International Space Station.
Though ISS contains sufficient supplies, safety concerns resulting from the malfunction have forced a shuffle in crew transfer scheduling. Soyuz-FG, which uses the same RD-0110 third-stage engine, is currently the only rocket approved to launch people to ISS. Soyuz rockets are grounded indefinitely until the problem can be isolated and solved.
There have been a confirmed total of nine Soyuz losses due to third stage failures, according to Flightglobal's Ascend SpaceTrak data, though none to a similar malfunction.