Warning sign? NASA never finished a fueling test before today’s SLS launch attempt

“…Space is hard, certainly. But Monday’s attempt—which NASA had promoted heavily by inviting celebrities to the launch and which included a visit by Vice President Kamala Harris—was perhaps a bit rushed. Why? Because NASA rolled a rocket out to launch without accounting for all of the things that could go wrong…

…Beginning in April of this year, NASA conducted four separate “wet dress rehearsal” tests during which the agency aimed to fully fuel the SLS rocket and countdown to T-10 seconds, ending the test before ignition of the main engines. Each of these four tests ultimately ended prematurely, although the fourth attempt in June saw engineers bring the rocket down to T-29 seconds.

However, to reach that late stage in the countdown, NASA had to “fool” the flight computer. During the test, a 4-inch hydrogen line—smaller than the problematic 8-inch line on Monday—had a leaky seal. To complete the wet dress test, NASA chose to mask the leak from the ground launch sequencer, the ground-side computer that controls the majority of the countdown.

Because of this masking, NASA could not complete the engine chill portion of the test. Had it done so, the agency may well have uncovered the problem that caused a scrub on Monday. In hindsight, therefore, NASA probably should have completed a full wet dress rehearsal before rolling the rocket out for a launch…”