The heaviest logistic flight to the ISS has been launched by NASA. STS-126 carries the Leonardo MPLM that is packed with supplies for the ISS crew. The mission would carry out a crew rotation on the ISS and the EVA's would solely focus on the starboard SARJ. The countdown was clean except for couple of issues during the opening part of the final DOO.
New modifications to the SRB holddown posts debuted on STS-126 that would prevent stud hang ups during launch. A stud hang-up occurs when the stud does not clear the aft skirt foot bore hole prior to the vehicle first liftoff motion (appx 200-250 milliseconds after ignition). A total of 25 aft skirt stud hang-ups at launch have randomly occurred on 23 shuttle launches since program inception, according to historical documentation. Looking to the future, STS-126 will also debut two new sets of instrumentation aimed at gathering data on RSRM behavior during the first stage. The resulting data would benefit to understand and mitigate TO on Ares I
