was scheduled for launch from LC-39B in the September 2009 timeframe. It was planned that after the STS-125 mission in October 2008, Launch Complex 39B would undergo the conversion for use in Project Constellation for the Ares I-X rocket. Several of the members on the NASA mission management team said at the time (2009) that single-pad operations were possible, but the decision was made to use both pads. Crew The crew assigned to this mission was a subset of the STS-126 crew: Early mission plans Three different concept mission plans were evaluated: The first would be to use a shuttle-to-shuttle docking, where the rescue shuttle docks with the damaged shuttle, by flying upside down and backwards, relative to the damaged shuttle. It was unclear whether this would be practical, as the forward structure of either orbiter could collide with the payload bay of the other, resulting in damage to both orbiters. The second option that was evaluated, would be for the rescue orbiter to rendezvous with the damaged orbiter, and perform station-keeping while using its Remote Manipulator System (RMS) to transfer crew from the damaged orbiter. This mission plan would result in heavy fuel consumption. The third concept would be for the damaged orbiter to grapple the rescue orbiter using its RMS, eliminating the need for station-keeping. The rescue orbiter would then transfer crew using its RMS, as in the second option, and would be more fuel efficient than the station-keeping option. The concept that was eventually decided upon was a modified version of the third concept. The rescue orbiter would use its RMS to grapple the end of the damaged orbiter's RMS. Preparations After its most recent mission (STS-123), Endeavour was taken to the Orbiter Processing Facility for routine maintenance. Following the maintenance, Endeavour was on stand-by for STS-326 which would have been flown in the case that STS-124 would not have been able to return to Earth safely. Stacking of the solid rocket boosters (SRB) began on 11 July 2008. One month later, the external tank arrived at KSC and was mated with the SRBs on 29 August 2008. Endeavour joined the stack on 12 September 2008 and was rolled out to Pad 39B one week later. Since STS-126 launched before STS-125, Atlantis was rolled back to the VAB on 20 October, and Endeavour rolled around to Launch Pad 39A on 23 October. When it was time to