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NASA scrubs Artemis mission yet again because SLS just can't handle the pressure

Sitting, Leaking Slowly?

It was second time unlucky for NASA as its Space Launch System rocket remained rooted to its Florida launch pad following a second scrub of its Moon mission.

Once again, the countdown was fraught with drama when over-pressure warnings were triggered in the liquid oxygen and hydrogen lines as engineers chilled down the plumbing of the vehicle prior to the loading of chilled fuel. Déjà vu struck as a leak was detected at an 8-inch quick disconnect (QD) point for the hydrogen fueling umbilical line at the base of the rocket (a different QD to the one that leaked during the first attempt earlier this week.)

Engineers paused liquid hydrogen loading to allow the hardware in the area to warm up in the hope that the leak would seal itself. When that failed, engineers had a crack at pressurizing lines to force the balky seal to reseat itself as the countdown clock continued its relentless march toward the launch window.

Alas, it was all for naught as NASA confirmed the inevitable. There will be no launch of the SLS into the Florida sky today. At least they managed to fill the tanks on the earlier attempt, this time they didn't even get that far before things went wrong.

Observers would be forgiven for pondering the wisdom of using such a fuel; sure, it gives a bigger bang than the RP-1 favored by the likes of SpaceX's Falcon 9 but, as ably demonstrated by the SLS's woes, has its downsides.

The selection of fuel was driven by NASA's decision to use left-over Space Shuttle bits for the SLS - in this case, the RS-25 engines which run on a mixture of liquid oxygen and hydrogen. With more than a decade since the Space Shuttle last launched, dealing with the problematic propellant has presented challenges throughout the dress rehearsal for the SLS launch, and on both the first two launch attempts.

It has been said that with Apollo, President John F. Kennedy pulled a bit of the 21st century into the 1960s. It is difficult to avoid the suspicion that with the SLS, NASA has dragged a chunk of the 1970s into the present day. While other rocket operators look to reusability and alternative fuels, the SLS is resolutely expendable and relies on the clearly difficult-to-handle liquid hydrogen.

There remains the potential for a third and final opportunity to launch before the SLS must be hauled back to the Vehicle Assembly Building on September 5. NASA did not confirm if it would take this opportunity or simply admit defeat and roll out the crawler to take the SLS back to the workshop.

The agency will face some awkward questions over the SLS. Excuses such as "but it's a new rocket" will fail to cut the mustard considering the heritage hardware at play and NASA's previous Shuttle experience. The stakes also could not be higher, particularly considering the SpaceX launch pads lurking behind the SLS as a reminder that there is another way. ®

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