SLS on pad
After a second scrubbed countdown test April 4, NASA will wait until after a crewed SpaceX launch April 8 before trying again. Credit: NASA/Joel Kowsky

WASHINGTON — NASA expects to be ready to perform another countdown rehearsal of the Space Launch System in early June as it pushes back the first launch of the vehicle to at least August.

At a May 5 briefing, NASA officials said they had made progress on two problems with the SLS and its mobile launch platform discovered during three attempted wet dress rehearsal (WDR) operations last month at Launch Complex 39B. Those problems, along with the need to upgrade supplies of nitrogen gas at the pad, prompted NASA to roll the vehicle back to the Vehicle Assembly Building (VAB) April 26.

That work included replacing a helium check valve in the rocket’s upper stage. Technicians found a small piece of rubber in the valve that prevented it from closing. “Right now they’re still investigating what could be the source of that piece of rubber,” said Cliff Lanham, senior vehicle operations manager for NASA’s Exploration Ground Systems program.

A hydrogen leak detected at the pad, he said, was likely caused by bolts on a gasket that has loosened up. Those bolts have been retorqued and don’t show signs of leaks, but he added they won’t know for certain that was the source of the leak until the vehicle is back at the pad and liquid hydrogen flows through that umbilical line. “We feel we’ve done what we can do at this point,” he said.

While that work was in progress at the VAB, Air Liquide, the company that provides nitrogen gas supplies to various sites at KSC, has been working to upgrade its system to meet the higher demands of the SLS. “The repairs at Air Liquide are progressing on track,” said Jim Free, NASA associate administrator for exploration systems development. He said NASA would soon check that the upgraded system can provide the nitrogen needed for SLS operations at the pad.

The completion of the repairs in the VAB and the nitrogen upgrades at the pad will determine when the SLS rolls back out for another countdown rehearsal. Free estimated that the vehicle would roll out “in the late May time frame” is work goes as planned. That would allow another WDR in early to mid-June.

He acknowledged that NASA might need to perform more than one WDR before feeling confident enough to move ahead with final launch preparations. “We are optimistic we only need one more based on everything we’ve been able to do so far,” he said. “But, we also want to be realistic and upfront with you that it may take more than one attempt.”

The current schedule for Artemis 1, he said, would allow at least two countdown rehearsals at the pad in June before rolling back to the VAB for final launch preparations, then back to the pad for a launch “in the August time frame.” One launch period from July 26 to Aug. 9, but Free said NASA was looking only at the early August part of that window. The launch would have to work around the Falcon Heavy launch of the Psyche asteroid mission, which has a short launch window that opens at the beginning of August.

Additional launch windows are available Aug. 23 to 29 and Sept. 2 to 6. “We have launch periods planned for the entire rest of the year,” Free said, although dates beyond early September are preliminary.

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...