Artemis I Mission Scrubbed as Launch Window Opens

NASA's Artemis I mission was scrubbed Monday just as the launch window opened at 8:33 am EDT.

The SLS developed multiple issues during the countdown at the Kennedy Space Center. The one that caused the mission to scrub appears to be an issue with the number 3 engine. But the mission had issues beginning as early as 6:25 am when the agency posted on its blog that while liquid oxygen loading into the interim cryogenic propulsion stage continued and core stage tanks continue to be replenished with propellants, engineers began to troubleshoot an issue conditioning one of the RS-25 engines (engine 3) on the bottom of the core stage. Launch controllers condition the engines by increasing pressure on the core stage tanks to bleed some of the cryogenic propellant to the engines to get them to the proper temperature range to start them. Engine 3 was not properly being conditioned through the bleed process.

Teams also noted what appeared to be a crack in the thermal protection system material on one of the flanges on the core stage. The flanges are connection joints that function like a seam on a shirt, are affixed at the top and bottom of the intertank so the two tanks can be attached to it. The launch team implemented an unscheduled hold at T-40 minutes to work on the issues.

That crack turned out to be only in the thermal insulation and not a problem with the spacecraft itself. But the number 3 engine issue ultimately led to the Artemis I mission being scrubbed. The weather was also becoming questionable, with clouds, rain and possible thunderstorms predicted for the area.

In a media briefing after the scrub, NASA said Engineers are evaluating data gathered during the Artemis I launch attempt. Teams could not get the rocket’s engines to the proper temperature range required to start the engines at liftoff, and ran out of time in the two-hour launch window to continue. The mission management team will convene Tuesday afternoon to discuss the data and develop a plan forward.

The Space Launch System’s four RS-25 engines must be thermally conditioned before super cold propellant begins flowing through them for liftoff. Launch controllers condition them by increasing the pressure on the core stage liquid hydrogen tank to route, or “bleed” as it is often called, a portion of the approximately minus 423 F liquid hydrogen to the engines. Managers suspect the issue, seen on engine 3, is unlikely to be the result of a problem with the engine itself.

During the countdown, launch controllers worked through several additional issues, including storms in the area that delayed the start of propellant loading operations, a leak at the quick disconnect on the 8-inch line used to fill and drain core stage liquid hydrogen, and a hydrogen leak from a valve used to vent the propellant from the core stage intertank.

A hydrogen leak was noted during a wet dress rehearsal in June. NASA said at the time: "Despite a liquid hydrogen leak detected earlier in the day when increasing pressure to condition the engines, teams were able to develop a plan to proceed into the terminal count with the expectation the countdown would stop after handover to the flight software for the automated launch sequencer. The software performs checks to confirm the engine temperatures are within acceptable range up to the point of the engine start sequence at T-9.34 seconds and operate correctly to halt the countdown at any point if temperatures fall outside that range, just as it would during an actual launch attempt."

NASA will host a media teleconference Tuesday, Aug. 30, at approximately 6 p.m. EDT to provide an update on data analysis and discussions. The time is subject to change. While managers have not yet set a date for the next launch attempt, the earliest possible opportunity is Friday, Sept. 2, during a two-hour launch window that opens at 12:48 p.m.

(Source: NASA. Image from file)