LGM-35A Sentinel - Ground-Based Strategic Deterrent (GBSD) program

Just something small I noticed in the details but W87-1 is described as a W78 replacement (note d), not a W87-0 replacement, so this may well imply something W78-sized physically but with W87-1-like yield, which is good because it suggests MIRVs. Also 5o ICBMs in storage - are they MMIIIs or Peacekeepeers?

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Desertfox said:
The Peacekeepers are in storage, I don't think any MMIIIs are.
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:oops: Didn't realise that, I suspected MMIIIs.
Desertfox said:
-1 and -0 use the same RV body so same size. But yes MIRVed
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The original -1 did, but is this the same thing? To replace the W78 for a 3xMIRV load (with the same bus area), like the notes say, it would have to be a Mk12A-sized RV. I guess time will tell.
 
Desertfox said:
Same RV, different payload inside.
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Found a source.
https://str.llnl.gov/2022-12/hsu
Strong partnerships with the U.S. Air Force, Lockheed Martin, and Northrop Grumman are key to having a reliable deterrent system based on the Sentinel intercontinental ballistic missile and the Mk21A reentry vehicle that will deliver the W87-1 warhead.
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Does seem to be an 'updated' version of the Mk21 though, hence the 'A' I guess.
https://www.llnl.gov/article/50021/...ogram-enters-phase-63-development-engineering
“Reaching Phase 6.3 for the W87-1 Modification program is an important milestone for the warhead program as we remain synchronized with the US Air Force for the Sentinel program and development of the updated Mark 21A reentry vehicle.
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Some interesting talk on the original -1 here as well. Apparently the only difference is the use of HEU in the secondary.
https://www.reddit.com/r/nuclearweapons/comments/15ccgp7/claim_the_upgraded_oralloy_w871_was_the
View: https://www.reddit.com/r/nuclearweapons/comments/15ccgp7/claim_the_upgraded_oralloy_w871_was_the/
 
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Forest Green said:
Found a source.
https://str.llnl.gov/2022-12/hsu

Does seem to be an 'updated' version of the Mk21 though, hence the 'A' I guess.
https://www.llnl.gov/article/50021/...ogram-enters-phase-63-development-engineering

Some interesting talk on the original -1 here as well. Apparently the only difference is the use of HEU in the secondary.
https://www.reddit.com/r/nuclearweapons/comments/15ccgp7/claim_the_upgraded_oralloy_w871_was_the
View: https://www.reddit.com/r/nuclearweapons/comments/15ccgp7/claim_the_upgraded_oralloy_w871_was_the/
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From Chuck Hansen's nuke book:

"Nominal W-87yield is 300 kilotons; yield can be increased to 475 kilotons by adding a sleeve of enriched uranium-235 around the secondary: the oralloy adds considerably to total yield when it fissions after the secondary is compressed and ignited by its "sparkplug". The 300 kiloton W-87 uses much less fissionable and fusionable materials than the W-78 with its 335 kiloton yield."
 
sferrin said:
From Chuck Hansen's nuke book:

"Nominal W-87yield is 300 kilotons; yield can be increased to 475 kilotons by adding a sleeve of enriched uranium-235 around the secondary: the oralloy adds considerably to total yield when it fissions after the secondary is compressed and ignited by its "sparkplug". The 300 kiloton W-87 uses much less fissionable and fusionable materials than the W-78 with its 335 kiloton yield."
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Yet the W78 is smaller. Just thinking, the Mk21A must have at least some differences with the Mk21 to have required flight testing.

bobbymike said:
Sentinel per missile cost increase
https://www.bloomberg.com/news/arti...eadSource=uverify wall&embedded-checkout=true
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The cost does include an upgrade of the entire infrastructure though. Peacekeeper cost $195m per missile in 2023 dollars without any upgrade to the infrastructure. Although a question must be posed, as with the Nimrod MRA4, is it actually cheaper to upgrade the existing silos, or just start anew?
 
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Forest Green said:
The cost does include an upgrade of the entire infrastructure though. Peacekeeper cost $195m per missile in 2023 dollars without any upgrade to the infrastructure. Although a question must be posed, as with the Nimrod MRA4, is it actually cheaper to upgrade the existing silos, or just start anew?
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Without considering land costs I'd bet it would be cheaper to build new silos. That being said I believe most of the land in the area has been sold off and the Federal government would have to buy back a large amount of land to build new silos - and if that's true I bet it is cheaper to upgrade the existing silos by a decent amount.
 
Shoes31 said:
Without considering land costs I'd bet it would be cheaper to build new silos. That being said I believe most of the land in the area has been sold off and the Federal government would have to buy back a large amount of land to build new silos - and if that's true I bet it is cheaper to upgrade the existing silos by a decent amount.
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From what I've seen the space taken up per silo is very little, but I guess there are 450 of them. I just think that a significant amount of the cost is probably stripping out and replacing old crap. New silos would also allow them to build them stronger.
 
bobbymike said:
Sentinel per missile cost increase
https://www.bloomberg.com/news/arti...eadSource=uverify wall&embedded-checkout=true
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Not the cost per missile on a crazy increase.

It's all the infrastructure that needs to be redone. When the program was originally bid out, redoing all the comms lines between silos and command centers etc wasn't part of the program of record, and the silos were to be overhauled.
  • Then it turned out that those comms lines are a rat's nest of splices added over 70 years, to the point that it's better (edit) cheaper to lay all-new lines with splice boxes built in to handle the exercise systems than it is to try to fix all the bad splices in the lines.
  • And it turned out that the silos themselves are in much worse material condition than USAF had led the bidders to believe, to the point that it's likely to be cheaper to build new silos from scratch than try to fix everything wrong with the old ones.
 
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https://www.nationaldefensemagazine...6iwO5al3ZUfR5lDw54_aem_q7Pp0VMtANH5x1508B9xaALaPlante said he rescinded the 2020 Milestone B decision for Sentinel and directed the Air Force to restructure the program, which will lead to an estimated delay of “several years.”
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We don’t have several years of delay. What we did to the nuclear enterprise starting in ~1989 was criminal.
 
So in regards to the Sentinel programme the costs for the actual missile itself are still under control?
 
NMaude said:
So in regards to the Sentinel programme the costs for the actual missile itself are still under control?
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Yeah, I think most of the cost is actually due to Nimrod MRA4-type issues of having to deal with old infrastructure. I hope someone has seriously considered whether just starting from scratch might be cheaper. Land-wise, it looks like there's enough room to just start constructing a new silo at the opposite side of the existing plot. Start next to the 50 empty silos first, so that you're always working next to empty silos.

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There doesn't seem to be an LGM-30 Minuteman thread (Which I find surprising) so I thought I'd post it in this thread as it seemed appropriate:


Explore the fascinating history and future of the US Minuteman ICBM, a 62-year keystone of nuclear defense. Discover its origins, technological evolution, and the looming transition to the new LGM-35 Sentinel.
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NMaude said:
So in regards to the Sentinel programme the costs for the actual missile itself are still under control?
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Appears to be, yes.

I mean, the costs of building a solid-fueled multi stage missile are pretty well developed, it'd take some egregious malfeasance to screw that part up.
 
Alex Hollings from Sandboxx has just put out a video about why the US needs the Sentinel ICBM:


The program to replace America's aging nuclear ICBM arsenal, known as the LGM-35A Sentinel, is already projected to go at least 81% over budget, representing tens of billions of dollars in anticipated cost overruns. But despite the program's ballooning expenses, the Pentagon has reaffirmed its commitment to the effort, calling its continuation, "essential to national security."
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Let's talk about why the Defense Department doesn't see the Minuteman III has what it takes to ensure American security for the foreseeable future, and what it's options are looking ahead.
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bobbymike said:
https://breakingdefense.com/2024/07...743&utm_content=316626743&utm_source=hs_email
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Admittedly, now that the USAF knows how much needs to be replaced, they probably could chop the new wiring and new silos out of the existing contract to get the missiles out of Nunn-McCurdy breach.

Because I'm sure anyone doing business with the .gov has absolutely evil penalty clauses in the contract for scope changes or contract modifications. I certainly would. Especially if doing business with the Navy.
 
Scott Kenny said:
Admittedly, now that the USAF knows how much needs to be replaced, they probably could chop the new wiring and new silos out of the existing contract to get the missiles out of Nunn-McCurdy breach.
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Were new silos actually part of the contract, or just new wiring, refubishment etc.? I think it was just a refurb:
https://www.afnwc.af.mil/Weapon-Systems/Sentinel-ICBM-LGM-35A/
I think it's cheaper to build new silos on the existing plots at this rate.
 
I wonder if the LGM-35A's booster-stack will have a constant diameter (Like the LGM-114A Peacekeeper), reduced diameter second third stage (Like the LGM-30G Minuteman III) or different diameters like the LGM-30A/B,G Minuteman I/II?
 
flateric said:
I wonder if you have seen official renderings and patches?
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I have seen the official renderings however I understand that isn't the definitive appearance so that's why I'm asking as there doesn't appear to be much information available concerning the rocket-motors that will be used in the booster-stack.
 
What makes you think that this is not a 'definitive appearance'?
 

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