The Space Launch System, or SLS, is a key part of NASA’s flagship Artemis program – an elaborate attempt to send the first woman and the first man of color to the surface of the Moon. But first, the SLS really has to fly, and before that could happen, NASA wanted to go through all the complicated steps that lead to a real launch – except where the rocket takes off. With the SLS standing on its launch pad at the Kennedy Space Center in Florida, NASA engineers and flight controllers filled the vehicle with its extremely cold propulsion on Monday, as they would on launch day. With all the SLS tanks full, the flight crew counted down for a simulated lifting time, with the plan to stop the countdown to about T-minus 9 seconds. Instead, the team stopped the countdown short to T-minus 29 seconds due to hydrogen leakage. NASA says it has been able to accomplish most of its test objectives, mainly by loading the vehicle with propulsion – but that there are still a few that could not be reached with the early shutdown. “I would say that the majority of our goals have been achieved.” “I would say most of our goals have been achieved,” said Charlie Blackwell-Thompson, NASA’s Artemis launch director, during a post-test press conference. “There may have been small pieces in this primary goal that we did not achieve.” NASA has attempted this general rehearsal three times in the past, and all of these efforts ended before flight controllers could fully load the rocket with a propeller. After the third failed attempt, NASA dropped the SLS on the service’s huge Vehicle Assembly Building to perform various repairs and upgrades before dropping the rocket onto the cushion again on June 6. Three of the dress rehearsals’ biggest goals included proving that the flight crew could load the vehicle with propulsion, stop the countdown, and then drain the SLS – all of which took place on Monday. In addition, NASA was able to enter the terminal countdown, the final phase of the countdown that begins T-minus 10 minutes before launch. NASA / Ben Smegelsky One of the big things they failed to try was a recycling attempt. The team had originally planned to reach the T-minus 33 seconds, stop the count and then return to the T-minus 10 minutes. This goal was to simulate an unexpected wait on launch day and a retry attempt, which can sometimes happen. The team would then have reached the T-minus 9.3 seconds – just before the series started igniting the main engines at the base of the rocket. The designs changed during the test. The take-off simulation was delayed by hours due to certain issues that flight controllers worked on throughout the day, including a hydrogen leak. Eventually, the flight controllers chose to bypass the stop and roll in the T-minus 33 seconds and simply proceed to the T-minus 9.3 seconds, according to CBS. However, they knew that the hydrogen leak would most likely cause a miscarriage on the flight computers before they reached this final countdown time. “We will make a decision on what is the best way forward.” During a post-test press conference, NASA staff stressed that most of the rehearsal general’s goals had been achieved. “I would say we are in the 90th percentile in terms of, you know, where we need to be overall,” said Mike Sarafin, director of the Artemis mission to NASA. But they were vague about the details that had not been completed. One of the goals they failed to achieve was to demonstrate what is known as a “bleeding flow” – a way to maintain proper propellant temperatures – due to hydrogen leakage. There was also some old material in the solid rocket boosters that did not have the opportunity to be fired as planned. Now, NASA says it is reviewing the data it has collected and will determine the next steps. “I think we’re going to take a few days and go through it and then make a decision about which is the best way forward,” said Tom Whitmeyer, NASA’s deputy associate for common exploration systems. The agency may choose to do another type of power test, and NASA’s Jim Free, NASA’s co-director of exploration systems development, said before that effort that NASA wanted a thorough test before it flew. “This is the first time we have flown this vehicle and I think we need to understand what we can do before we commit to launching,” Free said last week. But Whitmeyer noted that there is a “relative risk of continuing to exercise the material on the pad.” As for how this may affect the schedule for the first flight of the SLS, NASA will not say. The SLS is about to make its debut during a flight called Artemis I, which will see the rocket launch an empty crew capsule called the Orion around the Moon on a week-long journey. Ahead of this rehearsal, NASA noted that the earliest possible launch attempt would be during a window that opened in late August. Now with this test, NASA does not set specific dates. “I do not think we know yet,” Whitmeyer said. “We really need to sit down and do everything we just talked about: look at the goals, see what we have achieved and see what extra work may be required.”
