In an April 15 update, SLS executives said work had begun to locate the source of the leak, which was identified shortly after the start of the liquid hydrogen charge at the base stage of the missile during the April 14 attempt. It was the first time the controllers had reached this stage of the countdown after technical problems that stopped two previous attempts before the loading of liquid hydrogen began. The leak is located on the ground of a umbilical plate in the mobile launcher service tissue and not in the SLS itself. “The good news is that there are only a few things in this cleaning enclosure and there are a few distinct intrusions that could be the culprits,” said Charlie Blackwell-Thompson, Artemis Startup Manager. These represent what Mike Sarafin, director of NASA’s Artemis mission, called “low hanging fruit” to solve the problem. If the leak is detected and repaired quickly, NASA could attempt another wet-dress rehearsal as early as April 21, pending the series’ availability. Agency officials said in another briefing later in the day that the launch of the Crew-4 commercial crew at the International Space Station, scheduled for April 23, would outperform the SLS tests. The way forward is less clear, however, if the leak cannot be corrected quickly on the pad. “There are some more invasive options that require further access to the hardware and we may need to go into some extensive troubleshooting,” he said, suggesting that some of these options may require work on the Vehicle Assembly Building instead of the pad. Sarafin said engineers also had to consider the environmental issues of placing the vehicle on the brake for a long time, such as wind stresses on the tall vehicle. “The longer we stay on the pad, the more we stress the vehicle,” he explained. “Every time the wind blows in the opposite direction, it creates a moment of decline and, over time, it adds up.” “We have not fully described all the options at the moment,” he said. “What we are pursuing with great vigor is the selection of low fruits and we will let the team find some other options.” Blackwell-Thompson suggested one option would be to do another tank test as soon as the vehicle returns to the Artemis 1 launcher pad. “you tank before the launch countdown,” he said. In this scenario, the rocket would go through a tank test and perform the countdown and, if all went well, “a few days later would decide to start launching”. Although it has not passed the countdown test in three attempts to date and the uncertainty about when the hydrogen leak will be corrected, Blackwell-Thompson said it was not particularly concerned. He noted that there were five or six tank tests before the bus was first launched more than four decades ago. “Putting it in context, I would say we are in the family of our past experience for our first jobs,” he said.
