What we know about NASA’s supposedly ‘successful’ mega-rocket launch rehearsal

NASA's Space Launch System on the launch pad at Kennedy Space Center in Florida.

NASA’s Space Launch System on the launch pad at Kennedy Space Center in Florida.
Photo: Nasa

NASA enveloped yesterday saw its fourth wet dress rehearsal of the Space Launch System, during which ground crews achieved a number of key test objectives. That said, an unresolved hydrogen leak prevented full completion of the test, in a development that could further complicate the Artemis 1 mission schedule.

Yesterday’s wet dress rehearsal ended at 7:37 p.m. ET, with ground crews managing to fill both rocket stages with super-cold liquid oxygen and liquid hydrogen propellants, which they had been unable to achieve in the first three rehearsal attempts. Teams also practiced a terminal countdown, but the clock was stopped at T-29 seconds instead of the planned T-10 second mark. The rocket has been stripped of its propellant and it remains standing on Launch Pad 39B at Kennedy Space Center in Florida while launch controllers determine next steps.

A hydrogen leak caused the countdown to stop prematurely, in a decision made earlier on Monday, NASA officials told reporters today. Those missing 19 seconds might not seem like a lot, but the final moments before launch involve a ton of moving parts. It cannot therefore be said that NASA has carried out a full dress rehearsal of its mega Moon rocket. NASA officials are not yet ready to say whether a fifth wet dress rehearsal will be required or if SLS is finally ready for its maiden launch, a mission known as Artemis 1. The next Artemis missions could see a man and a woman landing on the lunar surface by 2025, the construction of the first lunar space station, and a long-awaited permanent presence on and around the Moon, but it all starts with SLS.

That the rocket’s tanks have been fully loaded with propellants and that a countdown is so close to the finish line – and all the things that need to happen before and in between – is still a big deal. During today’s media conference call, Tom Whitmeyer, NASA Deputy Associate Administrator for Joint Exploration Systems Development, said “those are really important things that we wanted to see.” Whitmeyer described the giant rocket as a complicated puzzle, and the recently concluded wet dress means “we now have a very good idea of ​​what the puzzle looks like”, but some unspecified outstandings must be analysed. Ground crews “have to chase the leak as well,” he said.

Indeed, the hydrogen leak ruined an otherwise uneventful launch rehearsal. This leak occurred while propellants were being poured into the rocket; crews attributed the problem to the rapid disconnection of the umbilical from the center stage tail service mast, the point where the line connecting the rocket and mobile launcher separates during launch. During the wet hold, ground crews worked feverishly to fix the problem by reheating the quick disconnect and then realigning it to form a tight seal, but it didn’t work.

Now, in a normal launch scenario, such a leak would undoubtedly have resulted in a scrub, but launch controllers wanted the repeat to continue. They “developed a plan to obfuscate the data associated with the leak that would trigger a hold by the ground launch sequencer, or launch computer, in an actual launch day scenario, to allow them to get as far as possible in the countdown,” according to a NASA statement. This allowed for a repeat of the terminal count (the last 10 minutes of a countdown), including a key step in which the ground launch sequencer is switched to the automatic launch sequencer controlled by SLS flight software . But for security reasons, the countdown had to be stopped shortly after the second transition of the T-33, due to the hydrogen purge line leaking issue, as explained by NASA officials during the press conference.

The words ‘success’ and ‘success’ were thrown around around generously at today’s press conference, but it’s fair to say that (1) the fourth wet dress rehearsal was incomplete (albeit slightly) so, (2) the rocket wouldn’t have launched, if this was a one-shot scenario, and (3) the unresolved hydrogen leak is clearly an issue that needs work. These concerns aside, the plethora of issues that plagued the first three attempts at wet clothes seem to have been fully resolved, and the Orion capsule is “nominally” functioning, as NASA officials told me during the Report.

Charlie Blackwell-Thompson, Artemis’ launch director, said the teams met many test goals, but some goals weren’t met in the final tally. She and her colleagues need to assess the data so they can come back with a recommendation on how to proceed, Blackwell-Thompson said, saying no decision has been made on whether another launch rehearsal is needed. . Mike Sarafin, NASA’s Artemis mission manager, chimed in, saying teams will look at “the risks of not performing another test.”

I’m a practice-made-perfect type of guy, so mine the feeling is that NASA should perform a fifth test. SLS is positioned as a work vehicle for the next decade or two, so another test doesn’t seem like a big deal, especially since the rocket is still on the launch pad and only a few final details need to be ironed out. . . A number of Artemis launch windows remain available to NASA, including late August and late September opportunities. NASA officials said they plan to meet with the press later this week, so we can get the answer quickly.

After: ISS maneuver test with Cygnus spacecraft did not go as planned.

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