WASHINGTON — While NASA has yet to update the schedule for the first flight of its Space Launch System, companies working on the heavy-lift rocket now expect the rocket to launch in early 2021 rather than 2020.

The first launch of the SLS, on a mission called Artemis 1, had been formally scheduled for the second half of 2020, a date that already represented two years’ worth of delays. That date is under review as NASA brings in new leadership for its exploration programs after reassigning former associate administrator Bill Gerstenmaier and his deputy, Bill Hill, in July.

During an Aug. 19 panel discussion at the American Institute of Aeronautics and Astronautics’ Propulsion and Energy Forum in Indianapolis, executives with companies involved with the SLS projected that, based on what work needs to be done to complete the vehicle for launch, that launch probably won’t take place before early 2021.

Jeff Foote, vice president of NASA programs at Northrop Grumman Innovation Systems, said he expected that, with the agency deciding to perform a “Green Run” static-fire test of the core stage at the Stennis Space Center next year, that core stage won’t arrive at the Kennedy Space Center for launch preparations until late 2020.

“From that time forward, with the integration of Orion, wet dress rehearsal and that sort of thing, there’s probably two quarters, maybe two and a half quarters, or work to get to a launch date,” he estimated. “So, most likely early in 2021. It could happen earlier, it could happen later.”

The core stage has been on the critical path for the launch for some time because of problems with its engine section. Both NASA and Boeing now expect the core stage to be completed and ready to ship to Stennis at the end of the year.

“We’ll probably fire it off in the second or third quarter of next year, and do a full test,” Robert Broeren, the integrated product team lead for SLS stages at Boeing, said of the Green Run test on the panel. “After that, it probably takes quite a bit of time to do rework and some upgrades to it, then we’ll put it on a barge and send it down to the Cape.”

Earlier this year NASA said it was considering whether the Green Run test was necessary, since skipping it could save several months of schedule. However, NASA Administrator Jim Bridenstine announced July 25 that NASA would go ahead with the test.

Bridenstine visited the Michoud Assembly Facility in New Orleans where Boeing is building the core stage Aug. 15, and said later he was impressed with the progress that we saw. “What I saw there was absolutely eye-watering,” he said Aug. 16 during a separate event at the Marshall Space Flight Center. He acknowledged the challenges in the engine section that delayed completion of the core stage, and NASA’s efforts to get around it by integrating the other sections of the core stage first.

That engine section, he said, is nearly ready to be integrated to the rest of the core stage, to be followed by its four RS-25 engines. He confirmed that work should be completed by the end of the year.

Bridenstine didn’t discuss the schedule for Artemis 1 in those remarks, but in July 17 testimony before the Senate Commerce Committee suggested a first launch in 2021, rather than 2020, was likely. “I think 2021 is definitely achievable” for that mission, he said then, but noted he wanted to bring in new leadership for the agency’s exploration program before setting a firm date.

A slip to 2021 would not necessarily delay the first crewed SLS/Orion mission, Artemis 2, now scheduled for 2022. “If Artemis 1 launches no later than mid 2021, there will be no impact to Artemis 2,” Bridenstine said in an Aug. 3 email to Sen. Mike Enzi (R-Wyo.), who several days earlier wrote to the NASA administrator about his concerns about cost and schedule problems with SLS and other major NASA programs.

“This is a realistic plan,” Bridenstine added, “but I would like to have new leadership in place and committed to an integrated schedule before committing to a date.”