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

[Josh_TN]

Why not just put Peacekeeper back in production?

Because it would take an extra 5-10 years compared to Sentinel? It’s not like any of those components would be available now, so it would be a total redesign.

 

[Josh_TN]

Yes but getting that back then already expensive ICBM Back again will be expensive but im for it. Give it GPS and Astro Navigation and you get pgm ICBM xD

Peacekeeper was inertial and I don’t see any reason for any other guidance mode for a silo bases weapon. I imagine Sentinel is also inertial only.

 

[Josh_TN]

The only way to be relatively secure with road mobile is dirt roads out in the boonies of the western states.

I’d argue modern SAR/EO satellite constellations with AI filtering will make any ground basing without overhead cover insecure by the end of the decade if not before.

 

[Scott Kenny]

I’d argue modern SAR/EO satellite constellations with AI filtering will make any ground basing without overhead cover insecure by the end of the decade if not before.

My definition of "relatively secure" for that was "while still obvious to satellites and vulnerable to ballistic/HGV first strike, difficult to attack on the ground."

 

[Scott Kenny]

Yes Minuteman silos can take a 120" diameter cold-launched weapon.

They'd need an 85" liner, then.

 

[A Tentative Fleet Plan]

They'd need an 85" liner, then.

Minutemen are already held in a cradle suspended from the sides. You could do something similar (albeit strengthened) for a large cold-launched system.

 

[Scott Kenny]

Minutemen are already held in a cradle suspended from the sides. You could do something similar (albeit strengthened) for a large cold-launched system.

Would be a relatively simple swap, then. Trick would be figuring out how flimsy you could make the cold launch tube and still punt the bird clear of the ground before main engine ignition. Though IIRC the existing transporters pull the birds without a liner and would put birds into a liner in the silo.

 

[A Tentative Fleet Plan]

Would be a relatively simple swap, then. Trick would be figuring out how flimsy you could make the cold launch tube and still punt the bird clear of the ground before main engine ignition. Though IIRC the existing transporters pull the birds without a liner and would put birds into a liner in the silo.

You'd probably want some sort of new structure to both support the much heavier missile and canister, not to mention one capable of resisting the force of ejecting the missile.

Somewhat moot, given much of GBSD's cost are to do with rebuilding ICBM force's infrastructure, so you could probably just build new silos, provided they were in already existing missile fields.

Reusing Minuteman silos does offer the potential for much bigger missiles than Trident, see Silo-Stuffer below:

 

[Scott Kenny]

You'd probably want some sort of new structure to both support the much heavier missile and canister, not to mention one capable of resisting the force of ejecting the missile.

Somewhat moot, given much of GBSD's cost are to do with rebuilding ICBM force's infrastructure, so you could probably just build new silos, provided they were in already existing missile fields.

Reusing Minuteman silos does offer the potential for much bigger missiles than Trident, see Silo-Stuffer below:

View attachment 711792

I would be very happy to see the Sentinel end up as the Silo Stuffer.

 

[Josh_TN]

My definition of "relatively secure" for that was "while still obvious to satellites and vulnerable to ballistic/HGV first strike, difficult to attack on the ground."

I read that as insecure for all intents and purposes. At least in a silo a nuke would be required; a mobile missile is a soft target once its location is known. A conventional HGV could be used against it, and unless there is enough separation, multiple TELs might be engaged by single nuclear detonation. I’d rather stick to a silo then have to assume at any given moment a number of my ICBM TELs positions (or all of them) were known.

 

[uk 75]

Does the US need a heavy hitting bunker killer ICBM like the old Titans.

 

[NMaude]

Does the US need a heavy hitting bunker killer ICBM like the old Titans.

Given that Russia has deployed the SS-30 Satan II I'd say they definitely should consider it, now if they do would it be a MIRV payload or a single large multi-megaton TN warhead?

 

[Scott Kenny]

I read that as insecure for all intents and purposes. At least in a silo a nuke would be required; a mobile missile is a soft target once its location is known. A conventional HGV could be used against it, and unless there is enough separation, multiple TELs might be engaged by single nuclear detonation. I’d rather stick to a silo then have to assume at any given moment a number of my ICBM TELs positions (or all of them) were known.

The Midgetman TEL wasn't that vulnerable once grounded. That's the setup I would assume for any road-mobile IRBM, especially in a small country.

Does the US need a heavy hitting bunker killer ICBM like the old Titans.

Yes. Something carrying 8-14x 450+kt booms, as long as it's landing within 50m of point of aim. Like Trident II.

 

[Josh_TN]

Does the US need a heavy hitting bunker killer ICBM like the old Titans.

No. The alternative is W88 or various flavors of B-61, but the former would be far more effective than a Titan given it’s accuracy. It’s worth noting even an AGM-86 has a 30 m CEP and 150kT warhead at the high yield option. There are very few targets that wouldn’t be vulnerable to even a W76 mod1.

 

[Josh_TN]

The Midgetman TEL wasn't that vulnerable once grounded. That's the setup I would assume for any road-mobile IRBM, especially in a small country.

It seems like a diminishing return to me. It’s still a relatively soft target and it is limited to a single small RV. If you can’t ensure that the location of your ICBM can be concealed, mobile basing loses all advantage, IMO. The silo requires a nuke and is easy to staff and maintain without a burdensome security element. SSBNs continue to be the bulk of the warhead count and the primary secondary strike capability, so why invest money in a questionable deployment scheme that will only grow more vulnerability with time?

 

[Scott Kenny]

It seems like a diminishing return to me. It’s still a relatively soft target and it is limited to a single small RV. If you can’t ensure that the location of your ICBM can be concealed, mobile basing loses all advantage, IMO. The silo requires a nuke and is easy to staff and maintain without a burdensome security element.

Oh, there's still a major security element at the silos.

Also, I was assuming a missile with at least 3x MIRVs, not a single warhead. Minuteman or maybe Polaris/Poseidon sized birds, not Midgetman.

SSBNs continue to be the bulk of the warhead count and the primary secondary strike capability, so why invest money in a questionable deployment scheme that will only grow more vulnerability with time?

Because it may be cheaper than digging more silos, if we get to the point of having all silos filled.

 

[Josh_TN]

Oh, there's still a major security element at the silos.

Also, I was assuming a missile with at least 3x MIRVs, not a single warhead. Minuteman or maybe Polaris/Poseidon sized birds, not Midgetman.



Because it may be cheaper than digging more silos, if we get to the point of having all silos filled.

I’m not familiar with ICBM security elements but I’m going to go out on a limb and assume a mobile missile above ground increases the manpower by an order of magnitude, at least when deployed on the move. When not deployed, we are left with a fixed garison of missiles that is essentially a soft target, just like the 40 or so Russian mobile regiments. ~80 warheads would likely take out >90% of those forces that weren’t actually out on deployment. Add in those that were dispersed but detectable by satellite. It doesn’t seem like a useful deployment scheme in this day and age.

 

[bobbymike]

Yes. Something carrying 8-14x 450+kt booms, as long as it's landing within 50m of point of aim. Like Trident II.

I read an article years ago (that I probably saved somewhere) where the head of StratCom said he’s seen D5 tests where the aim point was often inside the [non-explosive] RV crater. That’s some serious accuracy.

 

[Scott Kenny]

I read an article years ago (that I probably saved somewhere) where the head of StratCom said he’s seen D5 tests where the aim point was often inside the [non-explosive] RV crater. That’s some serious accuracy.

When the Kentucky (Ohio D5 boat) had visitors onboard, the MTs would tell the visitors to picture their local sportsball field, usually the Kingdome in Seattle. Polaris would land somewhere in the parking lot. Poseidon would land somewhere inside the stadium. Trident 1 would land somewhere on the infield. Trident 2 would land on the pitcher's mound, and you could call which corner of the pitcher's rubber block you wanted.

 

[Forest Green]

Expensive. Very expensive

You could have built >300 for the price of 20 B-2s.

 

[Forest Green]

You'd probably want some sort of new structure to both support the much heavier missile and canister, not to mention one capable of resisting the force of ejecting the missile.

Somewhat moot, given much of GBSD's cost are to do with rebuilding ICBM force's infrastructure, so you could probably just build new silos, provided they were in already existing missile fields.

Reusing Minuteman silos does offer the potential for much bigger missiles than Trident, see Silo-Stuffer below:

View attachment 711792

2nd from left is likely to be close to the Sentinel IMO.

 

[Forest Green]

You'd probably want some sort of new structure to both support the much heavier missile and canister, not to mention one capable of resisting the force of ejecting the missile.

Somewhat moot, given much of GBSD's cost are to do with rebuilding ICBM force's infrastructure, so you could probably just build new silos, provided they were in already existing missile fields.

Reusing Minuteman silos does offer the potential for much bigger missiles than Trident, see Silo-Stuffer below:

View attachment 711792

Isn't the missile 3rd from left shorter than a Peacekeeper (39.384 inches to a metre)?

 

[Calphor]

2nd from left is likely to be close to the Sentinel IMO.

Nope. Sentinel will have three stages of different diameters. Sentinel 3rd stage will likely be of similar diameter to MMIII 1st stage with each of the stages below larger than the one above.

 

[Calphor]

Isn't the missile 3rd from left shorter than a Peacekeeper (39.384 inches to a metre)?

Yes. All of the missiles shown are shorter than PK with the exception of the Silo Stuffer. PK is a very large missile. There is a great display in front of FE Warren AFB showing Peacekeeper, MMIII and MMI. It really shows off the size of Peacekeeper.

 

[Forest Green]

Yes. All of the missiles shown are shorter than PK with the exception of the Silo Stuffer. PK is a very large missile. There is a great display in front of FE Warren AFB showing Peacekeeper, MMIII and MMI. It really shows off the size of Peacekeeper.

Curious because the throw weight of Peacekeeper is only rated at 8,000lbs, same as the missile third from left. Maybe the length is the booster length only??

 

[bobbymike]

New Schedule for Sentinel Coming Soon, Says ICBM Modernization Boss

Brig. Gen. Colin J. Connor, head of Air Force Global Strike Command’s new ICBM Modernization Directorate, discussed Sentinel’s progress.

www.airandspaceforces.com

Again wouldn’t be so concerned if they didn’t ride the MMIII and the C3 to near death prior to modernization.

 

[sferrin]

Nope. Sentinel will have three stages of different diameters. Sentinel 3rd stage will likely be of similar diameter to MMIII 1st stage with each of the stages below larger than the one above.

Sentinal is almost certainly smaller than MM3. Where did you get the notion that it's smallest stage is the size of the MM3 1st stage?

 

[Josh_TN]

Sentinal is almost certainly smaller than MM3. Where did you get the notion that it's smallest stage is the size of the MM3 1st stage?

Do you have a source for the "certainly smaller"? From what I understand, throw weight is increased. That wouldn't make sense if third stage diameter shrunk such that MIRVs were not possible.

"The MMIII engines use heavy steel casings to house the missile propellant. These casings add to the weight of the missile and affect its flight range and payload capabilities. Modern rocket boosters, like the Navy’s D5 Submarine Launched Ballistic Missile, use composite material to save weight and increase potential payload. The boosters designed for the new missile will use a composite material, making Sentinel significantly lighter than the MMIII. Most notably, this will increase the missile’s throw weight, which is a measure of the weight of the payload that the missile can deliver to a particular range"

Report to Congress on LGM-35A Sentinel Intercontinental Ballistic Missile - USNI News

The following is the Congressional Research Service, Defense Primer: LGM-35A Sentinel Intercontinental Ballistic Missile on Jan. 10, 2023. From the report The LGM-35A Sentinel is expected to replace the Minuteman III (MMIII) Intercontinental Ballistic Missile (ICBM) in the U.S. nuclear force...

news.usni.org

 

[NMaude]

Is there any information about the SRMs that will be used in the Sentinel?

 

[Forest Green]

SRM?

 

[flateric]

Solid rocket motor

 

[jsport]

You'd probably want some sort of new structure to both support the much heavier missile and canister, not to mention one capable of resisting the force of ejecting the missile.

Somewhat moot, given much of GBSD's cost are to do with rebuilding ICBM force's infrastructure, so you could probably just build new silos, provided they were in already existing missile fields.

Reusing Minuteman silos does offer the potential for much bigger missiles than Trident, see Silo-Stuffer below:

View attachment 711792

stocking stuffer, 'silo stuffer', that is the loudest project name ever exclaimed

 

[bobbymike]

Is there any information about the SRMs that will be used in the Sentinel?

There was a Sentinel first stage test don’t believe they said the diameter. But years earlier there was a SRM “technology demonstrator” first stage that, IIRC, was exactly MMIII size.

So my speculation has always been Sentinel will be MMIII sized but lighter therefore with a modestly higher payload.

 

[Calphor]

There was a Sentinel first stage test don’t believe they said the diameter. But years earlier there was a SRM “technology demonstrator” first stage that, IIRC, was exactly MMIII size.

So my speculation has always been Sentinel will be MMIII sized but lighter therefore with a modestly higher payload.

There were a couple of demonstrator programs. One was LCS-1 which was a tech demonstrator using SR-118 (Peacekeeper 1st stage) as the baseline. There was also MCS-III which was a tech demo designed to show technology insertions within the MMIII 3rd stage OML that could be put into production.

As I said previously, Sentinel 3rd stage will be roughly the same diameter as MMIII 1st stage. MMIII 1st stage is about 54” in diameter. Sentinel will be intermediate in size between MMIII and Peacekeeper. As to the question of how I know, as I have stated in the past, I work in the industry.

 

[Calphor]

Is there any information about the SRMs that will be used in the Sentinel?

Nothing has been made public regarding SRM physical dimensions. However, the publicly released art for Sentinel is representative of the proposed design.

 

[bobbymike]

There were a couple of demonstrator programs. One was LCS-1 which was a tech demonstrator using SR-118 (Peacekeeper 1st stage) as the baseline. There was also MCS-III which was a tech demo designed to show technology insertions within the MMIII 3rd stage OML that could be put into production.

As I said previously, Sentinel 3rd stage will be roughly the same diameter as MMIII 1st stage. MMIII 1st stage is about 54” in diameter. Sentinel will be intermediate in size between MMIII and Peacekeeper. As to the question of how I know, as I have stated in the past, I work in the industry.

MMIII first stage is 66” diameter, second 52” diameter, third stage 52”

 

[Desertfox]

Sentinel will have more throw weight than MMIII. Also if you want road-mobiles, the best option is to use a harden shell game method, moving the launcher between say 10 hardened shelters.

 

[Kat Tsun]

Sentinel will have more throw weight than MMIII.

It may very well be smaller, enough for a single W87 Mod 0/1 and penaids, since just like the Minuteman. The penaids may give it a paper throw weight similar to Minuteman's triple warhead configuration but the warhead will probably be singular. There aren't many W87s left and no real capacity to make more after all!

Also if you want road-mobiles, the best option is to use a harden shell game method, moving the launcher between say 10 hardened shelters.

The best option is to use TELs disguised as freight vehicles and use your commercial truck fleet as cover, duh.

Proper VID is one of the big reasons why Russia has trouble targeting HIMARS and Brimstone carriers in Ukraine. It would be even harder for a strategic attack on the U.S. requiring VID of all road mobile TELs.

 

[NMaude]

It may very well be smaller, enough for a single W87 Mod 0/1 and penaids, since just like the Minuteman. The penaids may give it a paper throw weight similar to Minuteman's triple warhead configuration but the warhead will probably be singular. There aren't many W87s left and no real capacity to make more after all!

Even if there's only a limited number of W87s to go around it still makes sense for the Sentinel to be able to carry more than one RV as a way of future-proofing the design.

 

[Kat Tsun]

Even if there's only a limited number of W87s to go around it still makes sense for the Sentinel to be able to carry more than one RV as a way of future-proofing the design.

Why? This is a genuine question. Did you forget that Trident II has a higher "throw weight" than any ICBM deployed by the U.S. Air Force? Any future proofing is making the missile smaller and cheaper, both because the future is DOE downsizing, and because the Navy has the really big rockets anyway.

Giving it enough room to carry a decoy or something, or perhaps fit a future anti-simulation RV, or hyperglider, and making it small enough to be mass producible, are serious enough concerns by themselves. The last U.S. designed land-based ICBM was MGM-134, so they're going to look at that, because it's what USAF determined was optimal in the 1980's, and it's probably correct.

MX was only born out of an early 1970's requirement for a "heavy" ICBM to suppress SS-18 fields. These no longer exist. Why rebuild it?