SLS upper stage helium flow problem fixed

WASHINGTON — Workers have completed repairs to the helium pressurization system in the upper stage of the Space Launch System, keeping a potential April launch of the Artemis 2 mission on track.

In a March 3 statement, NASA said engineers traced a blockage in helium flow in the Interim Cryogenic Propulsion Stage, or ICPS, to a seal in a quick-disconnect line feeding helium from ground equipment into the stage. The seal had become dislodged, blocking helium flow.

Technicians removed the quick-disconnect fitting, reassembled it with the seal properly positioned and reinstalled it. Tests confirmed that helium was flowing into the stage after the repairs.

The quick-disconnect line was one of the leading suspected causes of the blockage, along with a check valve inside the stage. NASA said Feb. 21 that neither issue could be addressed at the launch pad, requiring the agency to roll the vehicle back to the Vehicle Assembly Building for repairs.

While addressing the helium issue, workers also performed maintenance on other parts of the SLS. That included replacing batteries in the core stage, ICPS and boosters, as well as replacing batteries in the rocket’s flight termination system ahead of end-to-end testing required by the Eastern Range.

NASA also said it is replacing a seal in a line that feeds liquid oxygen into the core stage. That seal is separate from those in liquid hydrogen lines that caused leaks during a wet dress rehearsal in early February and were replaced at the pad. NASA did not disclose why it is replacing the liquid oxygen seal, as there were no reports of leaks during the two fueling tests conducted last month.

NASA said the repairs and maintenance keep the vehicle on schedule to roll back out to the pad later this month for a launch attempt in early April. Two-hour launch windows are available on the evenings of April 1, 3, 4, 5 and 6 during the next launch period. The following opportunity opens April 30.

The agency did not disclose when it plans to roll the SLS and Orion spacecraft back to the pad. At a Feb. 27 briefing, Lori Glaze, acting associate administrator for the Exploration Systems Development Mission Directorate, said teams would need “at least a week and a half or so” at the pad after rollout to complete preparations for a launch attempt.