Work to replace a malfunctioning computer on one of the four engines in the SLS core stage will delay its first launch to at least March, NASA announced Dec. 17. NASA/Cory Huston

WASHINGTON — NASA is postponing the rollout of the first Space Launch System for a final prelaunch test by a month to give workers more time to complete vehicle preparations.

NASA announced Feb. 2 that it was delaying the rollout of the SLS from the Vehicle Assembly Building to Launch Complex 39B for a fueling test and practice countdown called a wet dress rehearsal. NASA officials said as recently as mid-January that they expected the vehicle to roll out to the pad in mid-February for that test.

Instead, said Tom Whitmeyer, deputy associate administrator for exploration systems development at NASA Headquarters, that rollout will likely take place in mid-March. He said in a call with reporters it was too soon to give a more specific date for that rollout given the work still ahead for crews.

Unlike in December, when a faulty engine controller, or computer that controls one of the SLS’s RS-25 engines, delayed a rollout then scheduled for the first half of January, there is no single issue causing this latest delay. “We just have a lot of things we need to close out,” Whitmeyer said. “It’s a big vehicle. There’s a lot of instrumentation that needs to be finished.”

“There really isn’t a significant thing that we’re working,” added Mike Bolger, manager of NASA’s Exploration Ground Systems program. “It’s just the volume of work and it’s us being really meticulous and making sure that, when we roll, we’re ready.”

Another factor has been the pandemic, including the recent surge in cases linked to the omicron variant. “I think that caught everybody off guard just by the sheer number of cases,” Bolger said. “It has slowed us down some.” He added, though, that the situation appeared to be improving as the number of new cases drops.

That delay rules out a launch of the uncrewed Artemis 1 mission in March, as agency officials had previously been hoping for. Instead, NASA is looking at two-week windows from April 8 to 23 and from approximately May 7 to 21 as launch opportunities for Artemis 1. The windows are governed by the performance of the SLS and mission constraints, such as having the Orion spacecraft splash down in daylight conditions.

That schedule will depend on the vehicle’s performance during the wet dress rehearsal. Bolger said it should take about two weeks to complete the full series of tests on the pad, from checks of vehicle interfaces on the pad through the full tanking test and practice countdown.

That time frame is approximate, though. “We do have some first-time uncertainties, but then some standard uncertainties,” said Mike Sarafin, Artemis 1 mission manager. The first-time uncertainties involve activities not done before, such as rolling the full SLS out to the pad and linking it to pad infrastructure. Standard uncertainties, he said, involve issues like weather that could delay the rollout and testing.

As in the past, agency officials said they don’t plan to set a launch date for Artemis 1 until after the wet dress rehearsal is complete. “We really don’t know until we do the wet dress rehearsal how much additional time it will take to get ready for launch,” Whitmeyer said. “We hope it won’t be a significant amount of time.”

Engineers are also continuing to study the engine controller problem that caused the delay in December. “We think we’ve isolated the cause of the problem,” he said, with an update on the issue expected in a couple of weeks. The issue needs to be cleared before launch, but would not delay the wet dress rehearsal.

Delays in the launch should not pose an issue for the SLS’s two five-segment solid rocket boosters. When NASA started stacking the boosters a year ago, agency officials said the boosters were certified for 12 months, but that testing could extend that limit.

“We would run into this problem periodically with the shuttle as well,” Whitmeyer said. Testing and data analysis, he said, allows them to extend the life of the boosters in their stacked configuration. “Right now on the boosters, we don’t really see this as a risk, even if we proceed on further into the year. We think we’re in OK shape.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...