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NASA to repair SLS liquid hydrogen leak on pad – SpaceNews

WASHINGTON — NASA will attempt to secure the cushion to a liquid hydrogen seal that caused the Space Launch System to gum up, keeping open the option of making another launch attempt later this month.

In a late September 6 statement, NASA said technicians would continue with plans to replace the joint at the interface called the quick disconnect between a liquid hydrogen supply line and the SLS core stage. This work will be performed on the platform rather than returning the vehicle to Kennedy Space Center’s Vehicle Assembly Building (VAB).

A problem with that seal led to what officials called a large leak of liquid hydrogen during core stage refueling during the Sept. 3 launch attempt. Several efforts to reattach the quick disconnect, by heating and then cooling it and applying helium gas pressure to the fitting, failed to stop the leak, and NASA called off the launch attempt. Artemis 1 three hours before the opening of the two-hour launch window.

During a Sept. 3 post-scrub briefing, NASA officials said they were considering options to repair the quick-disconnect joint while remaining at Launch Complex 39B rather than returning to VAB. Staying on the pad has “a few pros and cons associated with it,” said Artemis mission manager Mike Sarafin. “The downsides happen just about every afternoon here when you get a downpour or thunderstorm.”

NASA said in its latest statement that before beginning to replace the gasket, technicians would place an enclosure around the interface “to protect the hardware from weather and other environmental conditions.” The agency did not say how long this preparatory work or the replacement of the seal itself would take.

One of the advantages of doing the work on the pad is that the workers can then test the fitting using liquid hydrogen, which is not an option if the work is being done at the VAB. “It’s the only place we can get a full cryo test and make sure we don’t have an additional issue with leaks at the temperatures we need to fill the vehicle on launch day,” said said Sarafin.

Doing the work on the pad would also preserve the ability to proceed with another launch attempt without returning to the VAB. This, however, is only possible if the US Space Force’s Space Launch Delta 45, which operates the Eastern Range, extends Flight Termination System (FTS) certification on the rocket. This certification expired on September 6 and NASA should return to the VAB to reset the FTS, which is in a part of the rocket that is not accessible on the pad.

“We do not have an FTS waiver at this time beyond 25 days. Until we have that, we have to go back,” Jim Free, NASA associate administrator for exploration systems development, said during the Sept. 3 briefing. He said the agency would consider asking for an extension, but would have to determine how long of an extension it needed versus how much the eastern chain would give. “That negotiation didn’t happen, so as far as I’m concerned, we have to go back.”

If, however, the eastern range extends FTS certification, it may be possible to attempt another SLS launch during the next launch window, which opens September 20 and ends October 4. “I think it’s too early to say ‘whether a late September launch is possible,’ Sarafin said. “It really comes down to what the fault tree analysis is telling us and what changes are needed and what mitigations are needed to be confident that we’ve fixed this problem.”

Free said other factors could weigh into the decision to remain on the pad, including constraints for the Orion spacecraft remaining on the pad. “At the end of the day, we are guided by the FTS.”

If NASA decides to return to the VAB, which could be to perform further work on the vehicle or because of weather as Florida enters the peak of hurricane season, it would delay the launch by several weeks. , said Sarafin. That would push the launch back to at least the next launch window, which runs from October 17 to October 31.

NASA’s Sept. 6 update did not provide additional details on the cause of the leaking quick-disconnect seal. Agency officials speculated after the scrub that “unintentional overpressure” of the liquid hydrogen line during refueling preparations could have damaged the seal, but said they needed more time to investigate the problem.

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