In a March 12 media roundtable, Tory Bruno, president and chief executive of ULA, said the anomaly was traced to a “manufacturing defect” in one of the internal parts of the nozzle, an insulator. Specific details, he said, remained proprietary.

“We have isolated the root cause and made appropriate corrective actions,” he said, which were confirmed in a static-fire test of a motor at a Northrop test site in Utah in February. “So we are back continuing to fabricate hardware and, at least initially, screening for what that root cause was.”

That investigation was aided by the recovery of hardware that fell off the motor while in flight, which landed near the pad, as well as “trimmings” of material left over from the manufacturing process. ULA also recovered both boosters from the ocean so that they could compare the one that lost its nozzle to the one that performed normally. The defective hardware “just stood out night and day,” Bruno said. “It was pretty clear that that was an outlier, far out of family.”

That information has been passed along to the Space Force as part of the process to obtain certification for national security missions. “We’ve completed everything that you’re supposed to do,” he said, with that information provided last month. “Typically, it’s not a very long process in the past when vehicles are certified,” but deferred questions on the timeline of certification to the Space Force.

ULA’s next launch will be not of Vulcan but of Atlas, carrying a set of satellites for Amazon’s Project Kuiper constellation. That would be followed, once Vulcan is certified, of the USSF-106 and USSF-87 missions for the Space Force before switching back to Kuiper launches.