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Though NASA says it is not a problem, they have now revealed that the very expensive mobile launcher to be used for the first unmanned SLS launch in 2019, is leaning slightly.
The notes spoke of engineers being concerned about a lean towards the North – which would be towards the rocket when mated – with the angle of the leaning claimed to be seen as increasing when the Vertical Stabilizer porch was installed. It was also claimed the ML Tower is twisting and this issue increased when the porch was installed. This was cited as the reason additional arm installations onto the Tower were placed on hold, until the leaning-twisting issue is understood. Next in line for installation are the ICPS (Interim Cryogenic Propulsion Stage) Umbilical Arm, the Crew Access Arm and the two Vehicle Stabilizer Arms.
NASASpaceFlight.com’s Philip Sloss took the concerns to NASA to ask for clarifications. NASA responded, saying “the ML leaning/bending was not the cause of the delay in the install of the Crew access arm. These are unrelated.” However, they did expand on the specific issue, mainly to note it is understood and does not currently require any additional mitigation or modification to the ML.
“NASA’s mobile launcher is structurally sound, built to specifications, and does not require a design change or modifications. As expected, the mobile launcher is not perfectly still,” a NASA spokesperson added.
Note that this mobile launcher is not compatible with the second SLS launch, which would be the first manned flight in 2023. NASA will either have to modify it significantly at great costs, or build another, discarding this launcher after only one use.