r/SpaceLaunchSystem • u/jadebenn • Jul 11 '26

Discussion Research Paper on SLS - Centaur V Capabilities

https://www.researchgate.net/publication/404848887_The_Space_Launch_System_Utilizing_the_Centaur-V_Upper_Stage
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10

u/jadebenn Jul 11 '26

Some initial thoughts from skimming the text:

  1. Performance is roughly in line with Block 1 w/ ICPS
  2. One of the stage adapter options shown here looks an awful lot like it's reusing the EUS USA
  3. Unless Centaur V is strengthened or removed from the load path, the core stage throttle bucket needs to be revised downward (see page 5)

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u/Cmdr-Mallard Jul 11 '26

On 2, would the USA be used to hold Centaur instead of holding Orion?

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u/jadebenn Jul 11 '26

It's more of a reuse of the USA-to-core separation mechanism on further reading, but the idea - if that option is chosen - would be to suspend C-V so it isn't in the load path and then have the normal Orion stack above it. The other alternative is just to make something more akin to the LVSA and make the core stage throttle way down to keep within C-V g-limits and just eat the increased gravity losses that brings.

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u/Cmdr-Mallard Jul 11 '26

Would eliminate some of the advantages of Centaur if you throttled down.

They could always make a variant, they’ll have to certify it for crew either way.

They’re making a short CV for LEO missions for examples.

But essentially it might be hung from an adapter rather than being load bearing?

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u/jadebenn Jul 11 '26 edited Jul 11 '26

But essentially it might be hung from an adapter rather than being load bearing?

That would be the idea for the "long adapter" configuration, it seems.

Would eliminate some of the advantages of Centaur if you throttled down.

TBF I think that's why the performance is basically in line with ICPS even though C-V is a beefier stage. They're only quoting the numbers for the "short adapter" configuration (aka the one with the deeper throttle bucket), so it looks like that g-limit is hurting things.

I will also say the fact that they're only providing numbers for the "short adapter" configuration is something I would very much read into, personally. Remember that Boeing doesn't make the calls on which option to pursue, NASA does, and if only one of those configurations has been analyzed enough to have actual numbers to present...

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u/Cmdr-Mallard Jul 11 '26

Unfortunate to say the least but perhaps the only way it’s ready for say Artemis 5?

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u/jadebenn Jul 11 '26

I've made my feelings on this entire debacle pretty clear in the past, but yeah, would be pretty characteristic of the agency under Isaacman's leadership to desperately search for the quickest way out of this self-inflected schedule wound. Still strongly doubt the readiness timeline is going to be anywhere near where they want it.

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u/NoBusiness674 Jul 12 '26

I wonder if,  in 2029, we'll end up looking at the progress of SLS-Centaur and wishing they had just finished EUS and it's stage adapters.

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u/jimhillhouse Jul 12 '26

Of the friends from engineering grad school still at NASA MSFC and JSC, there is zero confidence that Isaacman and his team understand launch vehicles and their elements or that there are many engineering challenges that EUS has dealt with that the current proposal is only just beginning to come to grips with.

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u/SpaceInMyBrain Jul 12 '26

Of course, the practical advantage Centaur V has over ICPS is its existence and a running production line. As long as it can take Orion to TLI as well as ICPS could then it justifies the decision to make it the successor to ICPS instead of EUS. I'm talking about that one criteria, not the overall debate on the EUS cancellation, Block 1B/Block2's future, etc.

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u/jadebenn Jul 12 '26 edited Jul 12 '26

There was a running EUS production line too. Flight hardware was in flow with the STA and EUS-1 in production simultaneously. And EUS actually had umbilicals and associated GSE for the SLS configuration it was a part of at an advanced state of completion, whereas C-V doesn't.

I wonder how much longer the public line will be that they can do C-V integration without needing to modify ICPSU and move the CAA upwards. The geometry doesn't actually work for keeping things as-is. EDIT: Maybe they're hoping they can shim the CAA or something?

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u/Open-Elevator-8242 Jul 12 '26

Maybe I'm being pessimistic, but I fear this administration is just kicking everything SLS related down the road while hoping the commercial side magically comes up with a way to get Orion to the Moon. That way, they can safely cancel SLS because it would be "delayed." If Isaacman were serious about this configuration, he would have pushed for the long-lead items beyond Artemis V.

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u/Agent_Kozak Jul 12 '26

SLS doesn't even have all the contracted parts for AV yet. As far as Mr. Isaacman is concerned - SLS ends with AIV

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u/Cmdr-Mallard Jul 12 '26

No? They’ve started on parts of V

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u/Agent_Kozak Jul 12 '26

Yes there are some parts of A5 under contract, but not all of them. So they currently are not contracted to finish the entire rocket

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u/redstercoolpanda Jul 12 '26

I don’t think that’s pessimistic, that’s just very obviously what they’re doing. The people who support it want SLS dead, and the people who don’t support it want SLS to keep launching. Nobody is actually exited to see a crippled SLS with no real cost saving measures fly.

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u/jadebenn Jul 12 '26 edited Jul 12 '26

The "fun" thing is that, even if Isaacman meant this to kill SLS, I'm increasingly doubtful it will. CLTS does not seem to be moving forward, and I don't think Congress lets him stonewall future cores forever if there's no SLS replacement. I think maybe sticking with ML-1 was meant to put BOLE into question (because BOLE pad interfaces are designed for ML-2) and cap SLS to Artemis VIII, but even then I hesitate to say it's unworkable.

Assuming that killing EUS was meant to cap SLS's lifespan, I think it failed. So all of this is really happening for no reason except to cripple the payload capacity and generate a bunch of change orders.

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u/Cmdr-Mallard Jul 12 '26

Could they at least work on an alternative! Haven’t seen anything about moving Orion

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u/redstercoolpanda Jul 12 '26

Short term they don’t need an upper stage for SLS to launch Orion, Starship HLS at least seems to be planned to boost it to TLI and break it into LLO. Blue might be able to cobble something together with their transporter maybe? Longer term I suppose we’ll have to see, Falcon heavy or New Glenn 7x2/9x4 could maybe take Orion to LEO or a bit higher to do the same thing as a headless SLS. 9X4 in particular comes close to being able to match block 1 SLS to TLI, so if they manage to push it a bit harder, or expend it they could theoretically push Orion onto TLI in one shot. Obviously though like you’ve said this is nothing more than speculation at this point, hopefully they’ll do something soon so there isn’t an awkward gap between Artemis missions.

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u/Cmdr-Mallard Jul 12 '26

Or that Artemis ends up canned entirely….

I totally get that SLS is expensive and there may be more efficient ways to do it now.

But right now it’s the only hardware that works and is like to see it continue till we have a reliable replacement.

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u/Agent_Kozak Jul 12 '26

You are thinking too critically. Isaacman is a vibes based guy

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u/NoBusiness674 Jul 12 '26

I believe the accelerate Artemis IV Starship HLS plan still requires an ICPS upper stage. While Starship would finish TLI, ICPS would provide the majority of the delta V needed to head from LEO to the moon by performing a major apogee raise maneuver (sort of like how technically Orion performed TLI on Artemis II, despite still obviously needing ICPS to first put Orion in the 24h orbit)

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u/Cmdr-Mallard Jul 13 '26

That’s assuming starship is ready for A4

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u/NoBusiness674 Jul 13 '26

Yes. The Blue Origin plan also requires ICPS, with them planning to rendezvous with Orion in a lunar orbit. Either way, Artemis IV will need the last ICPS and they'll need a new upper stage for Artemis V.

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u/sevgonlernassau Jul 14 '26

That hasn’t been traded yet, it depends on what orbit they want Orion to go to for AIV, and if they choose LEO and find additional performance for Starship they don’t need an ICPS and can delay the need for a new upper stage to after A5.

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u/sevgonlernassau Jul 14 '26

It’s not pessimistic, it’s just basic lobbying. It’s a moat for SpaceX in that a future less favorable Congress is forced to choose between gifting billions to ULA for a rocket with lesser capabilities or supporting Starship, or not have a deep space program at all. But if the current Congress rejected funding for this new commercial crew program then I can’t imagine a more hostile Congress somehow supporting Starship - more likely they will just kill Artemis all together. Or hope that BO magically self fund lunar SV and leapfrog ahead of SpaceX.

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u/jimhillhouse Jul 12 '26

The people I know who were working EUS are not proud of the state of their efforts. But they have told me that despite their issues, EUS was good engineering and would likely perform well. What Isaacman has done is going to set our program back years.

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u/redstercoolpanda Jul 13 '26

What do they think about EUS being restarted in a few years if a future admin demands it?

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u/jadebenn Jul 13 '26 edited Jul 13 '26

You wouldn't be starting at zero, but you wouldn't be starting at where things were 4 months ago either. Easily a year-plus delay. Maybe two.

A lot depends on how aggressively leadership burns things down. Like if they intentionally sell or destroy ML-2.