NASA Spaceflight.com by Philip Sloss June 28, 2021
Final securing of the Space Launch System (SLS) Launch Vehicle Stage Adapter (LVSA) to the Core Stage for Artemis 1 in the Vehicle Assembly Building (VAB) at the Kennedy Space Center (KSC) in Florida was slowed down by issues discovered when workers started bolting the two elements together. NASA’s Exploration Ground Systems (EGS) and prime launch processing contractor Jacobs lifted the LVSA by crane up on top of the SLS Core on June 22 with mating expected to be finished that night; however, hard-mate was not completed for several days.
While the stacking procedures were delayed, other work in parallel tracks continued in different areas of the SLS vehicle. After the Core Stage was attached to its Solid Rocket Boosters in mid-June, post-Green Run repairs and refurbishment resumed along with preparations for upcoming vehicle power up and pre-launch testing and checkouts.
LVSA hard-mate issuesHard-mate of the LVSA to the forward skirt of the Core Stage for Artemis 1 was completed on the weekend of June 26-27 after the SLS interstage connector was lifted into High Bay 3 earlier in the week. Lifting operations themselves for the LVSA were delayed by the quick onset of the new Juneteenth federal holiday; when the lift team returned after the three-day weekend, the 325-ton crane was attached to the adapter in VAB High Bay 4 during the day on June 21 to lift it off its transportation pallet for inspections and cleaning of the lower mating surface.
Overnight on June 21 into 22, the approximately 9 meter tall cone was lifted up above High Bay 4, across the transfer aisle into the High Bay 3 integration cell, and lowered onto the forward skirt of the Core Stage. The connection between the Core Stage and LVSA is a bolted flange, with 360 bolts fastening the two elements together at one-degree intervals around the circumference.
The flange was soft-mated on June 22, but according to sources, completion of hard-mate was delayed into the June 26-27 weekend — which pushed back the lift and mating operations for the Interim Cryogenic Propulsion Stage (ICPS) to no earlier than the middle of the week of June 28. The LVSA hard mate is a constraint to starting the procedures to lift the ICPS and mate it to the top of the stage adapter.
It had been expected that hard mate would be completed by the end of the day on June 22, but work to fully secure the bolted connection was taking longer than anticipated. Ideally the mating surfaces would be perfectly flat, but there is some tolerance for the rings on the LVSA and the Core Stage not completely touching; however, sources noted gaps that were out of tolerance that needed to be addressed.
There was also an issue reported with the form and fit of splice plates, which are parts added to the flange to help fully mate them. A “tiger team” across the SLS program elements and contractors had been set up to address any issues that came up during stacking of the SLS flight hardware on the Core Stage, and the time consumed to resolve some of these “non-conformances” has been taken up as much by programmatic discussion and reviews as it has by hands-on work with the hardware.
Issues like these were expected in this first launch campaign. When assessing the schedule of work before the Core Stage arrived at KSC in late-April, EGS estimated as much as four months of risk to a six-month schedule of work.
More:
https://www.nasaspaceflight.com/2021/06/artemis-1-stacking-continues/
