NASA completes Space Launch System wet dress rehearsal following a few hiccups

space launch system at LC-39B

NASA completed the wet dress rehearsal of its Space Launch System rocket Monday from start to (almost) finish for the first time. It wasn’t without some hiccups, but this is a major milestone to fuel up all four tanks on the rocket before launch.

SLS’s wet dress rehearsal took place all day Monday. It began with fueling up the rocket just like it would be for launch and ended at T-29 seconds. This was the first time NASA was able to get this far, with previous attempts concluding before the terminal count could begin.

Getting through terminal count, which begins at T-10 minutes, was a big milestone. This included handing off between the ground launch sequencer and the automated launch sequencer, which the rocket controls. These control all the moving parts and manage when actions must take place to launch SLS. Again, this was a big step and one of many major milestones completed during the June 20 test.

This was also the first time NASA fueled all four tanks at the same time. This fueling process has four parts – slow fill, fast fill, topping, and then replenish. During previous attempts, one or more of the tanks could not be filled due to various issues with the rocket. Those issues have been fixed, but this test showed more kinks need to be worked out.

Leak in hydrogen bleed quick disconnect

While NASA did amazing work to get SLS through T-29 seconds, that was 20 seconds earlier than planned. A hydrogen leak was found on the Core Stage’s bleed quick disconnect. This led to lengthy holds to determine what to do next. Fueling operations continued, but the leak in the bleed quick disconnect didn’t allow NASA to test that specific system at about the T-4 minute mark.

This meant once the launch teams moved SLS to the automatic sequencer, it caught that the bleed system wasn’t prepared for launch and halted the countdown. The wet dress rehearsal was originally supposed to last until just before T-9 seconds. In a press conference Tuesday, NASA officials didn’t state if SLS would need a fifth attempt to complete a full rehearsal.

Space Explored’s take

This is a major milestone for NASA and builds more confidence in the successful launch of the Artemis I mission later this year. Of course, it is disappointing that another problem showed up, forcing more tests and most likely delays to the launch date. Will we see another full test? My bet would be no. Maybe another dry dress rehearsal or a modified fueling test to check the bleed system. NASA officials seemed very confident this test proved SLS is ready to fly, but we will have to wait and see when the data review process is over.

Featured Image: Derek Wise / Space Explored

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