Posts: 1524
From: Perth, Western Australia
Registered: Apr 2015

posted 02-22-2026 02:48 AM               

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quote:

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Originally posted by Blackarrow:
...I also suspect an astronaut would prefer to fly an Artemis mission after, say, four cryogenic recycles than 22 recycles.

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If the crew are happy to strap into a disposable rocket with 2 big solid rocket motors trying to rip the sides off the main fuel tanks at launch and as they accelerate through MaxQ, worrying if the structural fatigue count between fuel cycle 3 and fuel cycle 4 of a 22-cycle safe fatigue limit is probably low on the “what could possibly go wrong” list.

If we see a dozen more fuel-defuel cycles, that worry probably makes its way up the priority list.

Posts: 1449
From: Vancouver, WA, USA
Registered: Feb 2012

posted 02-22-2026 01:12 PM               

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After NASA rolls the SLS back to the VAB and fixes the issue with the interim upper stage, will NASA need to conduct another WDR after SLS is sent back to 39B? Can they just do a tank fill test instead of an entire WDR?

I am concerned about the interface that leaked liquid hydrogen, but is now seemingly fixed, might be disturbed by all that trundling back and forth between the VAB and 39B.

Posts: 56057
From: Houston, TX
Registered: Nov 1999

posted 02-22-2026 01:18 PM               

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That is a question only NASA managers can answer and will likely address at a press briefing later this week, after the SLS is back inside the VAB.

Having completed all of the necessary checkouts during the second wet dress rehearsal, it might be that the team decides to proceed with a launch attempt and scrub if necessary. The primary difference between a WDR and launch attempt is the presence of the crew.

Posts: 3930
From: Belfast, United Kingdom
Registered: Feb 2002

posted 02-22-2026 01:21 PM            

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quote:

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Originally posted by oly:
If the crew are happy to strap into a disposable rocket with 2 big solid rocket motors trying to rip the sides off the main fuel tanks at launch...

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That's a fair point about the SRBs (and I recall many shuttle astronauts saying they sighed with relief after booster separation) but all the little additional risks add up: remember the story of "the straw that broke the camel's back."

Referring to Ben's point about Apollo 16: yes, I had forgotten that Apollo 16 was rolled out to the pad in December, 1971 for a mid-March 1972 launch but was rolled back to the VAB in January for repairs, resulting in an April launch. But that wasn't caused by a problem with the launch vehicle itself, or fuelling leaks.

Posts: 585
From: Bennington, Vermont, USA
Registered: Feb 2011

posted 02-22-2026 04:26 PM               

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NASA did not solve the problem of hydrogen leaks during the Apollo or space shuttle program. They did, as they do now, work to halt the leak and then decided whether to press forward or scrub.

I was a fireman for Brevard County in the mid to late 70's, stationed on the coast. The PAFB fire dept came down for an educational visit (more community relations I suppose). At the time, they were on the mutual aid support list for KSC.

They brought up this issue of hydrogen leaks and fires, how the fire detection systems alerted to the presence of fire but not the location.

One way to zero in on the area was to use a corn stick broom and hold it out. When the end caught fire, the problem was located.

A low tech solution to the problem.

Posts: 56057
From: Houston, TX
Registered: Nov 1999

Posts: 56057
From: Houston, TX
Registered: Nov 1999

Posts: 56057
From: Houston, TX
Registered: Nov 1999

posted 02-24-2026 04:29 PM               

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NASA is targeting around 9 a.m. EST on Wednesday (Feb. 25) to begin rolling SLS off the launch pad and back to the Vehicle Assembly Building.

The 4.2-mile trek is expected to take up to 12 hours.

Posts: 56057
From: Houston, TX
Registered: Nov 1999

Posts: 594
From: Maryland
Registered: May 2010