NASA is working to track the source of the hydrogen leak from the SLS countdown test

WASHINGTON – NASA says it may try another rehearsal to count down the space launch system immediately after April 21, depending on how quickly they can fix a hydrogen leak that stopped the previous test.

At a briefing on April 15, SLS executives said they were beginning work to track the source of the leak, which was discovered shortly after they began loading liquid hydrogen into the rocket’s ground stage during the April 14 experiment. This was the first time the controllers reached this stage of the countdown, after technical problems stopped two previous experiments before the liquid hydrogen could begin to charge.

The leak is on the ground side of the umbilical plate of the tail service mast of the mobile launcher, not the SLS itself. “The good news is that there are only a few things in this purge chamber and there are a few discreet intrusions that could be to blame,” said Charlie Blackwell-Thompson, Artemis’ director of launch.

They represent what Mike Sarafin, head of NASA’s Artemis mission, called “low-hanging fruit” to fix the problem. If the leak is quickly identified and repaired, NASA may try another wet rehearsal immediately after April 21, pending the availability of the range. Agency officials told a briefing later in the day that the launch of the Crew-4 commercial crew to the International Space Station, scheduled for April 23, would take precedence over SLS tests.

However, the way forward is less clear if the leak cannot be quickly removed on the pad. “There are some more invasive options that require further hardware penetration and the possible need for advanced troubleshooting,” he said, suggesting that some of these options may require work done back in the vehicle assembly building. and not on the pad.

Sarafin said engineers also need to consider environmental issues, such as keeping the vehicle on the pad for extended periods of time, such as wind pressure on the towering vehicle. “The longer we stay on the site, the more we stress the vehicle,” he explained. “Every time the wind blows against it, it creates a bending moment, and over time it increases.”

“At the moment, we have not fully outlined all the options,” he said. “The one we’re chasing with great vigor is the low-hanging fruit option, and we’ll let the team come up with some other options.”

Blackwell-Thompson suggested one way to do another tank test after the vehicle returns to the Artemis 1 launch site. “Do you want to tank before the countdown,” she said. In this scenario, the missile would pass a tanking and countdown test and, if all went well, “a few days later decided to launch.”

Although she has not passed the countdown test in three trials so far and is unsure when the hydrogen leak will be eliminated, Blackwell-Thompson said she was not particularly concerned. She noted that before the shuttle’s first launch more than four decades ago, there were five or six tank tests. “Putting it in context, I would say we are in the family of our past experience of operations for the first time,” she said.