According to this interview on SpaceFlight Now, the recent failure of a Soyuz launch vehicle’s third stage does indeed give pause to wanting to put a crew on the next one right away, but Michael Suffredini, the NASA ISS manager, had the standard NASA response: OH NOES OH NOES OH NOES WE’RE DONE LET’S GET OUT NOW!
Well, actually he said that unless the Russians had success with launching the Soyuz reliably by November of this year, the crew would have to be brought home and the eleven years of a continually-manned space station would come to an end.
The Soyuz-U launch vehicle’s RD-0110 engine shut down early, causing the vehicle to crash. Fortunately, the Russians had telemetry all the way down so they have lots of data with which to analyze the fault.
The Soyuz-U and Soyuz-FG, used in manned flights, are almost the same vehicle, so the concern is not entirely unfounded. Still, this launcher is still the most reliable, and most-used, in the history of spaceflight. Various versions of the Soyuz launcher (which was based on the original R-7 ICBM used as a launcher by the USSR from 1957 onward) have been launched over 1700 times, and has a reliability record of over 94%.
Granted, the third stage is a little less validated than the rest of the vehicle – the earlier models that launched Vostoks and Volkshods had a smaller third stage. But not by much…
The R-7 variants are a little different from most American (and European) launch vehicles. The first stage is actually the liquid-fueled outside booster stages. The second stage is the core sustainer stage. The third stage would be considered the second stage on most American launchers, like the Deltas. This site gives you a lot more information about the Soyuz vehicles.
So I’ve digressed. My point is that I think these folks probably have a handle on getting it fixed. It feels weird saying that about the “Russkies” but it is what it is. They’ve built a load of these and most of them have flown. They know what they’re doing. I think it’s premature for the person in charge of the ISS on the NASA side to say, just a few days after the failure of an unmanned Soyuz, that we may have to abandon a billion-dollar space station in November. I hope he and the rest of the NASA ISS folks will wait a little longer and let the people in charge analyze the fault in the Soyuz. Some people bend tin, and some people spend years and years assessing risk.