Didn't the Space Shuttle have similar hydrogen leak issues?
NASA delays Artemis II to March after hydrogen leaks bedevil countdown test
NASA has concluded a Wet Dress Rehearsal (WDR) for Artemis II, but recurring liquid hydrogen leaks forced the test to be halted short of completion, prompting the agency to delay the mission's launch to at least March 2026. The extra time will be used to work through the issues that arose during the test before a second WDR. …
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Wednesday 4th February 2026 09:46 GMT frankvw
Frequently.
LH2 leaks were the leading cause of shuttle launch delays. So on the one hand you'd expect them to have some experience in mitigating that particular problem, although on the other hand it might not be mitigatable, which should give rise to the question of whether LH2's superiour specific impulse is actually worth the pain. (I suppose it is, or they'd have gone to liquid CH4 or back to RP1.)
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Tuesday 3rd February 2026 12:34 GMT A Non e-mouse
There's a whole debate around humans Vs drones for exploration that I'll skip here.
The underlying issue is that the Chinese are likely to be putting boots on the Moon "soon". So America is trying to resurrect some of the nostalgia from the Apollo era and trying to one-up the Chinese by going to Mars. Unfortunately, getting to Mars is way harder than going to the Moon.
Unfortunately, Boeing got involved. Then politicians had their snouts in the trough too and costs and timescales went the wrong way.
America's trying to salvage something from its sunk costs and we've got the Artemis programme doing a flyby of the Moon.
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Tuesday 3rd February 2026 14:49 GMT Filippo
It's mostly politics, but sometimes that can be a good reason. Doing something inspiring has value, especially in a time when cynicism has got to the point of being frankly crippling.
Whether that's a good enough reason, however, is a much more difficult question, one I can't attempt to answer.
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Wednesday 4th February 2026 09:55 GMT frankvw
"Is there a good reason to send people back to the moon?"
The Chinese seem to think there is. So the US wants to get there first. So that's a good enough reason. Geopolitics and the military aspects of rocketry drove the Mercury, Gemini and Apollo projects in the 1960s and that's what also drive Artemis now. Russia has been replaced with China but othewise we've all seen this movie before.
And that, incidentally, is my main gripe with NASA and Artemis right now as well. SpaceX might be a bunch of yahoos, but they do innovate. NASA has simply upgraded their existing 1960s technology to a somewhat bigger and powerful version of the hardware but otherwise it's pretty much rinse-and-repeat. In the 1950s and 1960s they had the balls to accept RUDs as a necessary part of R&D (like SpaceX does now) but they're so politics-bound these days that they'd rather not try than risk spectacular failures. Too bad.
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Wednesday 4th February 2026 17:09 GMT Anonymous Coward
Count how many unmanned missions have gone sideways for lack of a half-trained mook with a wrench or stout boots to ... *convince* recalcitrant machinery to behave.
The downside, obviously, is all the extra machinery to possibly go wrong that's needed to keep said mook in more or less working (or at least grumpily swearing) order...
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Tuesday 3rd February 2026 12:49 GMT xcdb
Pint to the chemical engineer :)
"You'd think the post-launch review from three years ago might have led with:
'So, what can we improve on?'
'Well, it'd be good not to trash the launch tower each time…'
'Oh, and we should probably give that whole hydrogen pissing out all over the place issue a coat of looking at.'"
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Tuesday 3rd February 2026 16:46 GMT awavey
Why ? A real chemical "engineer", and not some pretend AI version. would know that its rocket "engineering" thats causing the problem, ie the propellant connections on the mobile launch platform, and stages, not rocket "science" as the science of helium and loading of cryogenic propellant into rockets is very simple and well understood, even by so claimed chemical engineers
Unless they like being called chemical scientists too, which most engineers dont, a bit like surgeons dont like being called doctors.
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Wednesday 4th February 2026 02:47 GMT that one in the corner
Could be interesting. You wouldn't need enough to stretch the whole way to the Moon: once the stack is tall enough, the middle of it will be in orbit[1] and then the one at the bottom can just climb up without the tower dropping, followed by the one that was standing on its shoulders, then the one previously standing on his shoulders etc until they are all in space. With the correct timing you ought to be able to get the whole lot flung off in the direction of the Moon. Landing requires more acrobatics, this time adding at the middle and extending both down and up, until the bottommost can grab hold, all totally doable. Ahem.
You can see how it will all work in this diagram; really, it's not that hard(tm).
[1] yes, yes, that is an oversimplification, it won't quite be the middle; there may be an issue with lateral movement in atmosphere of the chain once the bottommost lets go with its toes and starts climbing up; questions exist over how much twang to impart so the line keeps moving out of the way of all the big (radio) shouty things that keep flying past (who put those there anyway?);
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Wednesday 4th February 2026 13:35 GMT David Hicklin
> yes, yes, that is an oversimplification
I am sure that this was done very tongue in cheek, and that you are well aware of the real engineering problems that would arise such as :
At some stage you will need to extend the base area otherwise the COG further up the stack will make it very unstable aka a pyramid structure
The above also solves the problem of the bottom robot carrying all the mass of those above it and its feel sinking into the ground (or simply collapsing)
Reaching orbit will not be stable until you reach geosynchronous orbit, anything unsupported below that will simply drop back down to the ground rather than staying up as you will not be orbiting fast enough' Let go before then and the whole stack will come crashing down.
Your stack will pass the moon once every day (or thereabouts) as the Earth is rotating much faster, so you will need a ski lift structure to hop on and off as it passed each time
Not sure how to handle the centrifugal force caused by the Earths rotation as you get further away, there is supposable an null point between the moon and earth but then as you start climbing back down towards the moon the forces will start to increase.
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Wednesday 4th February 2026 04:11 GMT Herby
No moon orbit...
This Artimis II thingy is just a simple flyby, and they won't even orbit the moon. The last time we did that it was because of a failure (see movie Apollo 13). This time all that will happen is that 4 guys will be able to see first hand the far side of the moon, and not much else.
Good effort, and a participation trophy for you.
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Wednesday 4th February 2026 17:59 GMT cray74
Re: tremendous success [Artemis 1]
I guess we're ignoring the heat shield issues?
The heat shield is mostly made of the same, flight-proven stuff used on the Apollo heat shields, AVCOAT, so NASA selected it with high confidence that it would work. NASA's endorsing it for Artemis II because, again, they know it'll work when reentry is kept to an Apollo-style direct entry.
However, NASA's learned something new about AVCOAT during the Artemis I flight: it doesn't like skip maneuvers.
An atmospheric "skip" allows a re-entering vehicle to effectively bounce up in a ballistic arc and land somewhere other than the original target. The skip distance can be significant - Apollo capsules could skip over 1,000 miles, while the Orion capsules can skip 5,500 miles.
So if your Orion capsule is about to land in the wrong ocean or continent, then you can skip to a more preferable landing site. Useful, right?
Apollo never tested a skip maneuver and, as far as I know, a skip maneuver had never been tested before the 2022 Artemis 1 flight. This left a gap between theory and reality. The gap was that it was thought that a skip maneuver would create a gentler thermal environment for the heat shield. The theory made sense: the Orion capsule wouldn't just blaze in at lunar return speeds to a full stop (25,000mph to 0) but would get a briefer, lower peak heating, then have a chance to cool off as it skipped above the atmosphere, and finish reentry some minutes later. Lockheed's Orion skip page still talks about those 'thermal environment' benefits.
Orion's 2022 flight was uncrewed, so NASA decided to finally try the skip maneuver, and that's where reality proved theory wrong.
The problem with ablative heat shields like AVCOAT, PICA, and others is that they depend on polymers. In a normal reentry, these polymers pyrolize in the heat of reentry (consuming some heat energy), form fumes from decomposition ("blowing") that pushes the superheated plasma away from the surface, and then char, forming an insulating layer. This would continue as reentry stripped away the ablator, exposing fresh ablator to fight the good fight. Basically, there are several processes preventing heat from the plasma from soaking through the heat shield and reaching the contents (e.g., astronauts) behind the shield.
But they're still polymers, which start having mechanical and chemical problems at a few hundred degrees (on any temperature scale).
The two-part skip maneuver interrupted some of those ablative heat shield processes as the maneuver carried the scorching shield back into a vacuum. Rather than immediately dropping into the thick, cooling air of the troposphere and splashing into the cold ocean minutes after peaking heating, the plastic shield was heat-soaked in a vacuum. This roasting produced gas pockets and spallation inside the shield material.
And as the damage developed inside the heat shield, the shield was thrown back into the furnace again. Large chunks were torn from the spalling-damaged material by aerodynamic forces. NASA and Lockheed-Martin developed bladder control problems upon seeing the heat shield. (Which still worked - the capsule was intact.)
After figuring out the problem in 2024, NASA approved AVCOAT for the Artemis II flight, but took atmospheric skip maneuvers off the menu. AVCOAT works just fine when used as physics, if not the manufacturer, indicates.
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Thursday 5th February 2026 19:53 GMT cray74
Re: tremendous success [Artemis 1]
That means that Orion has not been proven for reentry at the speed profile Artemis II will be coming in at.
The heat shield was tested in an Artemis II-like flight profile by Exploration Flight Test-1 in 2014. After the Artemis I heat shield mishap in 2022, there has been extensive, supplementary lab testing to revalidate the heat shield design.
If Artemis II sticks to an Apollo-like course, it should be fine.
Of course, I would've said the same thing about the shuttle's heat shield before 2003. After all, there were 112 good flights of the shuttle's heat shield design, so it should be fine on the 113th flight.
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Biting the hand that feeds IT
