Fix in the Works for Giant SLS Welding Machine

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COLORADO SPRINGS, Colo. — The gigantic welding tool that will piece together the stages of NASA’s Space Launch System rocket has been taken apart and will be put back together around August to correct a misalignment that made it impossible to use the machine, a NASA official said.

Sweden’s ESAB Welding & Cutting, which has its North American headquarters in Florence, South Carolina, built the roughly 65-meter tall Vertical Assembly Center (VAC) as a subcontractor to SLS contractor Boeing at NASA’s Michoud Assembly Facility in New Orleans.

ESAB wrapped up construction in September, but discovered the finished tool was out of alignment and therefore unable to lift parts of the 8.4-meter-diameter SLS stages all the way up and down its length for welding.

The problem was due to a “miscommunication” between two ESAB suncontractors, Todd May, NASA’s SLS program manager, said here after an April 15 panel discussion at the National Space Symposium.

“The requirement, which was to be horizontal within one eighth of an inch [0.3175 centimeters] measured 170 feet up was not passed to one subcontractor, and instead that subcontractor used the standard tolerance requirements for plate flatness to horizontal within 0.06 inches at the base of the tower,” May wrote in a subsequent email to SpaceNews April 20. “This corresponded to a roughly 2.5-inch [6.35 centimeter] misalignment at the top, compared with the intent to have to towers horizontal to within one eighth of an inch [0.3175 centimeters].”

Todd May
NASA SLS program manager Todd May. Credit: NASA/Marshall Space Flight Center

In other words, the VAC’s baseplate, which secures the tool to Michoud’s concrete floor, was cocked too far to one side. The angle was very slight — the highest part of the baseplate was less than half a centimeter above its lowest part — but it was enough to put the whole tool out of alignment, May said.

While the baseplate’s alignment can be corrected easily enough, the plate sits at the very bottom of the VAC and cannot be accessed without disassembling substantial parts of the machine, said May.

For now, the exact effect SLS’s development, both in terms of cost and possible delays, has yet to be calculated, May said. In February, Ginger Barnes, Boeing’s outgoing SLS program manager, said the Vertical Assembly Center was supposed to be ready by March.

Boeing’s SLS stages contract is worth $2.8 billion over six-and-a-half-years. Finalized in July, the deal runs through 2021 and calls for the company to deliver two SLS cores, including hydrogen and oxygen tanks, and avionics. SLS is slated to loft the Orion crew capsule to lunar space twice: once in 2017 and once in 2021. Only the second flight will be crewed.