It not bad weather interrupted CRS-10 mission as it was predicted before. Launch was halted in the last moments before ignition due the technical reasons.
More positive weather forecasts from Friday, which mentioned that chance for launch increased from 50% to 70% turned out to be truth. Launch was possible and refueling process along with final preparations were performed according to schedule.Rocket was rolled out to Launch Pad 39A already on Friday and spent night in horizontal position. From early morning hours on Saturday all necessary tests were performed, Rocket was erected and fueling process started at T-45'. It was confirmed with final weather forecast predicting following hours with good weather conditions over Florida and Kennedy Space Center.
In the last moment before igniting nine Merlin-1D engines, countdown was terminated at T-15" and launch was scrubbed. Officially it was caused by minor issue with steering of the engine in the second stage. Problem was located in vector control system, which is controlling direction where thrust is pointed. It is one of the most crucial systems used for controlling whole second stage of the rocket during flight. As Elon Musk announced on Twitter:
"All systems go, except the movement trace of an upper stage engine steering hydraulic piston was slightly odd. Standing down to investigate...
If this is the only issue, flight would be fine, but need to make sure that it isn't symptomatic of a more significant upstream root cause"
Engineers are still working at Launch Pad, SpaceX decided to postpone launch for today, on 14:39 UTC.