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Monday (June 20) was a big day for NASA’s Artemis 1 mission.
The agency’s massive new moon rocket, the Space Launch System (SLS), concluded a more than 50-hour launch simulation known as a “wet dress rehearsal” Monday night (June 20). After several failed attempts in April, mission team members were able to: full fuel for SLS for the first time on Monday, completing a series of crucial pre-launch tests.
It was a big milestone for the Artemis 1 moon mission, but there were some snags along the way.
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Ground teams at NASA’s Kennedy Space Center (KSC) in Florida spent the weekend reviewing procedures and checklists for Artemis 1’s SLS, Orion capsule and ground systems the same way they would if they were preparing for an actual launch.
SLS is NASA’s backbone Artemis programa new-age successor to Apollo that the space agency hopes will help establish a permanent human presence on the moon† And with a new moonshot comes a new moon rocket. SLS has never flown before and the recent wet dress rehearsal would be the last hurdle. But it is not yet clear whether Artemis 1 is actually ready to fly.
Monday’s activities focused primarily on filling the missile’s cryogenic fuel tanks. The two-stage SLS uses liquid hydrogen (LH2) and liquid oxygen (LOX) as hypergolic propellants. Three attempts to fuel the rocket during an earlier wet-dress attempt in April were aborted when operators encountered technical problemsincluding a hydrogen leak high in the mobile launch pad (MLP) of the Artemis 1 stack.
Those issues were addressed in KSC’s Vehicle Assembly Building (VAB) for the past month, but controllers encountered another hydrogen leak Monday while spinning the wet dress on the launch pad. However, this new leak appeared in a “quick disconnect” – a point where the fuel cables connecting the SLS to the MLP are designed to separate during launch.
This new leak impacted proceedings on Monday. The technicians’ efforts to fix the problem were unsuccessful, and their efforts pushed the count back three hours. But once the SLS was fully fueled up, NASA officials made the decision to send a software patch so they could still continue the simulated countdown.
The patch actually allowed the ground launch sequencer to bypass the automatic checks that would have detected the leak, but the onboard flight systems for SLS couldn’t undergo the same failsafe bypass. As planned, the terminal count continued until the second mark of the T-33, after which the ground computers transfer flight control to SLS’s systems.
The count was eventually stopped at T-29 seconds. NASA had hoped to bring the clock all the way back to T-9 seconds, as originally planned, but considers the wet dress rehearsal largely a success anyway.
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“I’d say we’re in the 90th percentile,” Mike Sarafin, NASA’s Artemis mission manager, said during a talk with reporters on Tuesday (June 21).
“Terminal count is a very dynamic time,” explains Charlie Blackwell-Thompson, Artemis launch director at the Exploration Ground Systems Program at KSC.
There are “many time-critical events that take place in the terminal count, which are monitored in the flight software as well as on the ground, and in the interaction between the two,” she added.
Blackwell-Thompson and other NASA representatives during the conversation cited the shortcut leak as the only major failure during Monday’s refueling and agreed the wet dress was “extremely supple.”
Now agency officials must determine if this wet dress was good enough. The leak prevented the count from reaching the T-9’s second target for aborting the wet-clothes launch, but that doesn’t mean NASA will have to do the wet-clothes rehearsal all over again before deciding to cancel the Artemis 1 mission. launch, which will take an unmanned Orion on a journey of about a month around the moon. And by Tuesday’s phone call, nothing had been decided.
“There are a few things we didn’t get in the terminal count,” Blackwell-Thompson said. “We’re going to see what those are. We’re going to see what that means for us, if there are ways to test those, and then we’ll come back and make a recommendation.”
“We really need to sit down and… look at what we’ve accomplished, see what extra work is needed and look at the [quick disconnect]Sarafin added during Tuesday’s phone call, pointing out that since the NASA operators’ long day on Monday, not much work had been done to analyze the test data.
NASA officials on the call were optimistic about the path ahead, even if they were non-committal about what’s next for Artemis 1 in the near future. During the conversation, there was a shared confidence that a clearer path forward would emerge in a few days, after the team had a chance to examine the Artemis 1 stack and the wet dress data.
“We’re taking all the data from yesterday and taking it with us the next time we load this vehicle,” Blackwell-Thompson said. “I’m sure it will go as smoothly as the core stage went yesterday.”
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