Monday (June 20) was a big day for NASA’s Artemis 1 mission.
The agency’s huge new moon rocket, the Space Launch System (SLS), concluded Monday night (June 20) a more than 50-hour launch simulation known as the “wetsuit rehearsal.” After several failed attempts in April, members of the mission team were able to full SLS fuel for the first time on Monday, concluding a series of crucial pre-launch tests.
This was an important step for the Artemis 1 lunar mission, but there were a few hiccups along the way.
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Ground crews at NASA’s Kennedy Space Center (KSC) in Florida spent the weekend reviewing procedures and checklists for the SLS, Orion capsule, and Artemis 1 ground systems in the same way they would if they were preparing for an actual launch.
SLS is the backbone of NASA Artemis programa new-age Apollo sequel that the space agency hopes will help establish a permanent human presence on the moon. And with a new moonburst comes a new moon rocket. SLS has never flown, and the recent wet suit rehearsal was supposed to be its final hurdle. But it’s not yet clear whether Artemis 1 is actually ready to fly now.
Monday’s activities focused primarily on filling the rocket’s cryogenic fuel tanks. The two-stage SLS uses liquid hydrogen (LH2) and liquid oxygen (LOX) as hypergolic thrusters. Three attempts to fuel the rocket during a previous wet-test in April were aborted when operators technical problems encounteredincluding a hydrogen leak at height in the Mobile Launch Platform (MLP) of the Artemis 1 stack.
Those issues were resolved inside KSC’s Vehicle Assembly Building (VAB) over the past month, but controllers encountered another hydrogen leak on Monday while running the wet dress on the launching ramp. This new leak, however, appeared in a “quick disconnect” – a point where the refueling cables connecting the SLS to the MLP are designed to separate during launch.
This new leak affected Monday’s proceedings. Efforts by technicians to fix the problem were unsuccessful and their work pushed the count back by three hours. But, with the SLS fully populated, NASA officials made the decision to ship a software patch allowing them to continue the simulated countdown anyway.
The fix allowed the ground launch sequencer to skip automatic checks that would have detected the leak, but the onboard flight systems for SLS were unable to experience the same fail-safe bypass. As expected, the terminal count continued until the T-33’s second mark, at which point the ground computers handed over flight control to the SLS systems.
The count was finally stopped at T-29 seconds. NASA had hoped to lower the clock to T-9 seconds, as originally planned, but considers the wetsuit repeat largely a success regardless.
Photos: NASA’s new Space Launch System mega-rocket
“I would say we’re in the 90th percentile,” NASA Artemis mission manager Mike Sarafin said in a call with reporters Tuesday, June 21.
“The terminal count is a very dynamic time,” said Charlie Blackwell-Thompson, Artemis launch director in the Exploration Ground Systems program at KSC.
There are “many time-critical events that play out in the terminal count, which are verified in both flight software and on the ground, and in the interaction between the two,” she said. added.
Citing the quick-disconnect leak as the only major issue during Monday’s tanking, Blackwell-Thompson and other NASA representatives on the call agreed that the wet dress was “extremely smooth.”
Now agency officials must determine if that wet dress was good enough. The leak prevented the count from hitting the T-9’s second target for the wet-dress launch abort, but that doesn’t mean NASA will have to start the wet-dress rehearsal again before deciding to launch the mission. Artemis 1, which will send an unmanned Orion on a roughly month-long trip around the moon. And at Tuesday’s call, nothing had been decided.
“There are a few things we didn’t understand in the final tally,” Blackwell-Thompson said. “We’ll see what it is. We’ll see what it means for us, if there are ways to test them, then we’ll come back and make a recommendation.”
“We really need to sit down and…look at what we’ve accomplished, see what additional work might be needed and take a look at the [quick disconnect]Sarafin added on Tuesday’s call, pointing out that since NASA’s long operator day on Monday, little work had yet been done to analyze the test data.
NASA officials on the call were optimistic about the way forward, though they weren’t committing to what’s next for Artemis 1 in the immediate future. On the call, there was a shared confidence that a clearer way forward would emerge within days, after the team had a chance to review the Artemis 1 stack and wet dress data.
“We’ll take all the data from yesterday and incorporate it the next time we load this vehicle,” Blackwell-Thompson said. “I’m sure it will be as smooth as the main stage yesterday.”