SLS: Core stage wet dress rehearsal complete, ‘early shutdown’ in fueling test being evaluated

After a few weeks of trial and error, NASA says it has completed the wet dress rehearsal test step for the core stage of Space Launch System, the agency’s rocket to the Moon and beyond. This is the final step before NASA and Boeing engineers fire the core stage in place for eight minutes to collect data.

The wet dress rehearsal involves fueling the rocket core stage with 700,000 gallons of liquid hydrogen and liquid oxygen at precise temperatures. Early in the test step, it was discovered that the target temperature was not reached. NASA paused fueling and readjusted its fueling procedure to accommodate for the performance experienced during testing. A few days later, refueling began with operational changes in place.

NASA says wet dress rehearsal was completed on December 20, although the test ended sooner than expected.

First looks at the data indicate the stage performed well during the propellant loading and replenish process. Part of the test was to simulate the countdown with the tanks loaded, leading up to 33 seconds prior to the engines firing. However, the test ended a few minutes short of the planned countdown duration. […]

The team is evaluating data to pinpoint the exact cause of the early shutdown. Then they will decide if they are ready to move forward with the final test, a hot fire when all four engines will be fired simultaneously.

NASA aimed to complete core stage testing this week, but unexpected results in the wet dress rehearsal process have extended the process so far.

Following the hot fire test, the SLS core stage will be transported from Stennis Space Center in Mississippi to Kennedy Space Center in Florida. Then Space Launch System can be fully assembled and readied for the Artemis I mission around the Moon that’s currently set for November 2021.

Space Explored’s Take

While it’s frustrating to see the Space Launch System Green Run test extend into the new year, discovering and correcting issues during testing is working exactly as intended. As far as the calendar year goes, NASA and Boeing teams at Stennis Space Center were dealt a tough hand in 2020.

An extended shutdown and depleted workforce due to COVID-19 would be enough for one year, but at least three named hurricanes required testing to stop and additional steps to be taken to secure the core stage. If the November 2021 launch date for the Artemis I mission has to slip, we can thank the team at Stennis Space Center for at least getting us close in an extraordinarily trying year.


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