NASA to return SLS to assembly building tomorrow Wednesday
UPDATE: Due to weather, the roll back to the VAB is now delayed until Wednesday, February 25, 2026.
Original post:
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According to its most recent update, NASA is now planning on rolling its SLS rocket back to the Vehicle Assembly Building (VAB) no sooner than tomorrow, February 24, 2026, in order to begin its investigation into the helium flow issue in the rocket’s upper stage that has now delayed any launch until April at the earliest.
Returning to the Vehicle Assembly Building at Kennedy is required to determine the cause of the issue and fix it.
Teams are reviewing the exact time to begin the approximately 4 mile, multi-hour trek. The quick work to begin preparations for rolling the rocket and spacecraft back to the VAB potentially preserves the April launch window, pending the outcome of data findings, repair efforts, and how the schedule comes to fruition in the coming days and weeks.
The present launch window closes on April 6, 2026. For a launch to occur, NASA engineers need to identify and fix the flow issue. They will also need to test it, which suggests they will have to do some form of fueling test once the rocket is returned to the launchpad.
All of this takes time. First we have one week to get back to the VAB. Then at least a full two weeks in the VAB to identify and fix the upper stage. Then another week to roll the rocket back to the launch pad. And then another week to do another fueling test on the launchpad. That brings us to the beginning of April.
In other words, NASA has no time margin at all. If anything takes just a little longer than planned, it will not make the April launch window.
None of this is a surprise. SLS in its first launch attempt in 2022 missed its spring launch window due to similar issues and ended up launching six months later (after more launch scrubs). I predicted it would happen again now. NASA at this moment has not revealed any later launch windows, so we don’t yet know how long a delay to expect if it misses this window. Based on 2022, I suspect the delay would be until the fall.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
UPDATE: Due to weather, the roll back to the VAB is now delayed until Wednesday, February 25, 2026.
Original post:
————————
According to its most recent update, NASA is now planning on rolling its SLS rocket back to the Vehicle Assembly Building (VAB) no sooner than tomorrow, February 24, 2026, in order to begin its investigation into the helium flow issue in the rocket’s upper stage that has now delayed any launch until April at the earliest.
Returning to the Vehicle Assembly Building at Kennedy is required to determine the cause of the issue and fix it.
Teams are reviewing the exact time to begin the approximately 4 mile, multi-hour trek. The quick work to begin preparations for rolling the rocket and spacecraft back to the VAB potentially preserves the April launch window, pending the outcome of data findings, repair efforts, and how the schedule comes to fruition in the coming days and weeks.
The present launch window closes on April 6, 2026. For a launch to occur, NASA engineers need to identify and fix the flow issue. They will also need to test it, which suggests they will have to do some form of fueling test once the rocket is returned to the launchpad.
All of this takes time. First we have one week to get back to the VAB. Then at least a full two weeks in the VAB to identify and fix the upper stage. Then another week to roll the rocket back to the launch pad. And then another week to do another fueling test on the launchpad. That brings us to the beginning of April.
In other words, NASA has no time margin at all. If anything takes just a little longer than planned, it will not make the April launch window.
None of this is a surprise. SLS in its first launch attempt in 2022 missed its spring launch window due to similar issues and ended up launching six months later (after more launch scrubs). I predicted it would happen again now. NASA at this moment has not revealed any later launch windows, so we don’t yet know how long a delay to expect if it misses this window. Based on 2022, I suspect the delay would be until the fall.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
I shocked some fellow space advocates before the launch of the first test flight by saying that I hoped it blew up on the pad, certainly putting it and us out its misery and forcing a rethink. Of course I want this manned flight to succeed!!! However, it is almost guaranteeing that the next words spoken from the lunar surface will be in Mandarin.
Chester Peake,
I can appreciate your expressed sentiment. Certainly any even approximate repetition of the Artemis 1 delay soap opera anent Artemis 2 would consume a great deal of SLS-Orion’s remaining political capital while providing an opportunity for Starship to put some significant points on the board.
It is by no means a given – as far too many now assume – that “the next words spoken from the lunar surface will be in Mandarin.” Internal politics in the PRC have been more than a tad turbulent recently. End-stage totalitarianisms are prone to sudden brittle fractures. Even if Xi hangs on for awhile, though, there is the additional X-factor of what he might do about Taiwan – perhaps even sooner than the PRC’s notional schedule for a first manned lunar mission. Should he make such a move and it goes badly the PRC could well lose the ability to essay any lunar missions for years even assuming a sub-optimal outcome of a Taiwan land grab doesn’t bring down the regime entirely.
“Paging Jeff Wright. Jeff Wright, customer needs assistance in the Copium aisle.”
I must be missing something. I need a grizzled OldSpacer to explain to me how this isn’t actually a setback, but a wonderful thing for the American Space Program!
I’m just here for the SLS pile-on.
I’d consider rolling to Florida to witness a SLS launch, there are probably only two more opportunities to do that.
I couldn’t find any launch window availability after 30 April so I asked my new brain, Grok. Grok said it couldn’t find any launch windows after 30 April:
“As of February 2026, NASA has not published official launch windows for Artemis II in May, June, or July 2026, as the mission’s current target is no earlier than April 2026 following recent delays due to a helium flow issue in the SLS rocket’s upper stage. space.com +2
If further delays occur, NASA would release updated availability for later months, typically featuring clusters of 4–6 dates per lunar cycle (about every 4 weeks) with daily windows of approximately 120 minutes each. space.com +1
These are determined by factors like lunar orbital mechanics, spacecraft power/thermal constraints (no eclipses over 90 minutes), and daytime reentry conditions for crew recovery. space.com
For reference, here are the most recent published windows (subject to change based on mission readiness):
February 6, 7, 8, 10, 11 Earlier window; now passed due to delays.
March 6, 7, 8, 9, 11 Next window; likely missed due to rollback for repairs.
April 1, 3, 4, 5, 6, 30 Current target;
120-minute windows, times vary (e.g., April 1 opens at 6:24 p.m. EDT).”
Guessing May 1,2,3,4, also. Falcon’s always a reliable option.
John: You would have done as well if not better simply searching BtB for this info.
Well, I actually want Starship to succeed long term since zealots seem bent on killing not one but two rockets Marshall created that actually took payloads to the Moon. I maintain the perhaps antique belief that some great things also need to be done by nations as nations to promote unity and involvement.
Had Starship flown to the Moon and SLS never got beyond LEO you would have had a point–but that wasn’t the case. If the best part is no part…then four liquid fuel engines are better than forty.
There will never be a MSS in orbit. Should Starship have leaking problems in LEO, folks will be about as understanding about that as SLS haters are of current events.
Hillhouse was right…
Jeff Wright: it doesn’t need to be done by the state to be representative of America, promote unity, or get people involved. SpaceX building lunar bases and enabling the settlement of Mars will do all of that in spades. Nice ad hominem, too.
You write as if Starship development is over. It is not. No matter how much you refuse to understand this, your misunderstanding can’t change reality. Starship will fly to the Moon, the SLS program will end after a tiny handful of launches, and you will be left raging because your ego is far more important to you than real life.
As for hypothetical leaks, cogent points here are that SpaceX’s rate of improvement is dramatically faster than Boeing’s; Starship is much cheaper than SLS; and there will be many more tests of Starship depots and transferring propellant on orbit than SLS launches, by far. ‘SLS haters’ have dramatically more reason to be critical of the SLS than you have ever had to be critical about Starship, because you insist on ignoring every difference between the rockets, instead preferring rhetoric and chest-thumping about Alabama and MSFC. You’ve given yourself no out of this aside from being made to look an ignorant fool.
Nate P: I repeat, if I wanted to as inarticulate as Jeff Wright, I would point out that Falcon Heavy put a Tesla a lot farther out then SLS flew Orion, and thus proved without doubt that Falcon Heavy is better than SLS.
But that kind of stupid argument makes no sense, and nonsensical arguments make my brain hurt.
Newspacers aren’t trying to kill Marshall rockets. Just pointing out that they have suicided and brain function has stopped. Organ donation is salvaging body parts after cessation of brain function to keep viable people alive.
Robert Zimmerman: yeaaaaah… he’d benefit from a rhetoric class.
I have been saying all along that given past performance, it will not launch this year.
I have my doubts about the heat shield, too, but am hoping for the best on that one
Tesla is not a spacecraft, Robert–you know that as much as I do.
I am very glad Nate is not NASA Chief Administrator.
Jeff Wright: yes, you are allergic to accountability, fiscal responsibility, free enterprise, and common sense. The SLS must be defended at all costs because it’s Alabama’s baby, all delays are irrelevant, all costs are irrelevant, Alabama must have its ego stroked!
Hey guys I like Jeff being here.
We need someone promoting the government side of things and he is perfect for that job.
I don’t mind Jeff being here or government programs (where appropriate). His contribution has made the government look less appealing, not more.
Chester Peake wrote: “However, it is almost guaranteeing that the next words spoken from the lunar surface will be in Mandarin.”
Do we really care?
We have learned, even before SpaceX reminded us, that the long-term goal is the object of the exercise. The Soviet Union put the first satellite, dog, and man into low Earth orbit, but the United States got to the Moon, and we now do more in space than the rest of the world combined. Blue Origin landed New Shepard’s booster before SpaceX landed its own booster, but SpaceX reuses a fleet of Falcon boosters on more than a hundred annual launches. Rocket Lab was first to launch from a privately owned launch pad, but SpaceX is nearing the end of a development campaign for Moon and Mars missions. Being first is no guarantee of long-term leadership.
We don’t have to Beat the Chinese™ to the Moon, because we already did.
On the other hand, it would be nice if, as the first Chinese land on the Moon and say (in Mandarin) something like, “that was one small step for mankind, but a giant leap for China,” a lunar rover pulls up and an astronaut hops out to give them a lift to the nearby Hilton hotel.
The point is, China’s lunar project is much like NASA’s. The plan is to land on the Moon, plant yet another flag, and walk around for a while to pick up some pretty rocks, but the long-term plan for SpaceX’s lunar project is to build a busy lunar base, “Moonbase Alpha,” where a million satellites are made for their orbital data centers. The long-term plan for Blue Origin’s lunar project is to move polluting industry off the Earth. Which of them gets there first is less important than what they accomplish there.
That is what we really care about.
____________
Jeff Wright,
You wrote: “If the best part is no part…then four liquid fuel engines are better than forty.”
That depends upon the engine and the mission. Jeff, I am so glad that you don’t design anything that I fly on.
“Tesla is not a spacecraft”
One of them is now!
To John Hare
I can’t think of another time a D-IV upper stage had problems. We already had one person here wish it exploded. That alone makes me suspect a wayward NewSpacer committing sabotage …knowing full well there would be a backlash.
No one objected when I entertained the notion that Boca is so close to Mexico that someone might take a potshot at it. That likelihood is also higher now after the recent cartel strike. I hope Elon has shot spotter equipment.