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

bobbymike said:
And even with soon to be two nuclear peers we’re not expanding just replacing.

Should announce a 1000 missile/silo program, 200+ B-21s and 20+ Columbias.
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Realistically you'll never get that, but they should at least be able to deploy 400 ICBMs and 192 SLBMs (12 Columbias). Hope the ICBMs can carry more warheads to make up for the reduction in SLBMs.
 
Desertfox said:
No one is canceling GBSD, its the most bipartisan of anything in congress.
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“Most bipartisan “ might be a stretch but fairly true. Despite the steady trickle of media articles denying any need for a replacement on cost grounds, there is little effort in any branch of government to curtail the program. The SLCM-N faced much longer odds as a non strategic weapon, and it seems even this will be produced.
 
Forest Green said:
That kind of accuracy surprises me, I was under the impression, CEP was around 100m for D5s, although I read in the early '90s that PGRV (basically an AMARV with terminal homing) would be accurate to a CEP of 20m.
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Program CEP requirement was about that. Everyone has said that in practice the D5 is significantly better than that.


Dilandu said:
Frankly, this sounds more like a bragging for civilians.
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"Pick which corner of a 6"x18" rubber block" is definitely bragging.

"Target point within the impact crater" of a ~200MJ thump is likely accurate.
 
CEP was generally reported as a hundred meters. Smart fusing however might improve that. My understanding is for at least the W76 mod1, the down range accuracy is significantly increased by slightly over shooting the target and adjusting the detonator to trigger over the target to compensate for down range ambiguity, which is much larger than cross range inaccuracy due to the geometry of delivery.

Those who truly know do not say, but I suspect even W76 could crack some 10,000 psi targets.
 
Desertfox said:
The cost is most certainly an issue and why the US has stuck to silos.

The cost of decoys can be significantly reduced by making the TEL externally look exactly like a tractor-trailer, the whole idea depends on being able to place something like a Midgetman inside a tractor-trailer. Yes a satellite can tell a TEL from a semi, but it can't look inside a semi's box nor tell semi's apart.
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Minuteman 3 is an 80,000lb missile, which is getting into oversized load rules on the highways and so needs more than 2 axles up front and 2 axles in back on the road. GBSD is likely the same size, maybe 90klbs on the upper bound. The whole TEL is then probably 100,000lbs of load or more.

You'd need something like the military HET with 3 powered axles under the 5th Wheel and then 3-4 axles under the trailer. Probably needing tag axles as well (the unpowered axles that can be lowered or raised to spread the load out over more wheels), on both the tractor and trailer.

Midgetman was only 30,000lbs, so it could conceivably fit into a 60ft trailer with all the other TEL bits, but the stabilizers needed as a TEL would be very obviously "not belonging" on an ordinary 60ft box trailer. No, it's not easy to hide the stabilizers.

The ideal TEL simulator is a mobile crane truck, not a semi. Lots of wheels to spread the load out as much as possible, has obvious stabilizer jacks that are necessary for the main job. But those basically don't leave urban areas very often. Might be viable for Europe, but not the US where it's a couple hundred miles between cities out west.

So now you're talking about your decoy as something that is obviously a TEL.

Also, see my response to Yellow Palace's comment below:
Yellow Palace said:
Sure, but it needs to be a tractor-trailer that has all the same external signatures as a live TEL to anything you think the bad guys might get within detection distance. That doesn't just mean the same outer mould line, but:
  • Mass and mass distribution. When it goes over a bridge, the bridge needs to deflect identically.
  • Thermal signature. A live weapon will, at a minimum, emit some level of decay heat. Are the hot spots in the same places and equally hot?
  • Radiation signature. A live weapon will emit some level of radiation. Your decoy needs to be able to mimic that. You can shield it to some extent, but then you're increasing your mass and thermal signatures.
  • Chemical signature. If anything in your weapon offgasses, then that's detectable.
  • Technical signature: If you've got 1 live launcher and 4 decoys, and only one launcher is fitted with a missile turboencabulator, then intelligence sources can just pull the maintenance records for the turboencabulators. If the decoys have signature emulators, then the ones that don't are clearly live.
  • Operational signature: obvious, but not trivial. Your decoys need to be moved like they're live. Full security detail. Full security clearance for everyone who touches them. That's a huge cost.
And that's just the ones I've though of while on a tea break.

Sure, some of these may not be easily observed by satellite. But if you're planning to disperse by road, any competent bad guy is going to have some special operations or intelligence types a mile or two from key choke points with a good telescope and sensing devices.

The technical and operational stuff basically implies that your decoy and live TELs are absolutely identical. Most just have a missile simulator in them, and the rest have a live missile. As few people as possible - and ideally nobody in the missile convoy - knows which are live.

The question then becomes, how much more expensive is it to have more live missiles? If the missile is a low proportion of the overall system cost - either because the missile is cheap or you need a lot of decoys - then it may turn out that decoys don't save money.
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While you'd have to get very close to most missiles to worry about detectable radiation, all those other points are, well, on-point. I mean, I slept within 3 feet of Trident tubes, but about 20ft from the business end. The only place that had a marked radiation area was between the tubes on Upper Level. Getting close enough to detect the radiation would also mean getting within the defense perimeter of the convoy, probably physically on the truck/trailer.

Your decoys need to do all the things that an actual missile would need to do, like I bold+italicized in the comment.

At some point, the cost of a missile becomes a trivial part of this whole equation, and at that point you might as well just load your "decoy launchers" with live missiles.


In_A_Dream said:
Has the US ever explored mimicking China with their mountainous tunnel networks, where their TELs can pop out of any of the numerous entrances to stage an attack?

Not only can a complex like that provide cover, but concealment of movement, maintenance, and preparation too. And it would be re-usable infrastructure for future missiles.
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Building such a tunnel network is very expensive and time consuming. Plus, most of the US that has lots of big mountains also has lots of earthquake faults, so tunnels are contra-indicated there.

Also, if the attacker's missiles are sufficiently accurate, you can do a lot of damage to anything inside the tunnels by putting a warhead at the entrance. Better if you have a penetrating warhead that can be 10-15m inside the tunnel when it goes off.


Yellow Palace said:
I would venture to suggest that this is still the case, for the same reason. But when you're throwing thermonuclear warheads around, the difference in accuracy with modern weapons is insignificant.
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It actually matters a whole lot with heavily hardened structures, the ones built to thousands of PSI as the standard. Those you need to plant that warhead within a few meters of the structure to destroy it.
 
Desertfox said:
I've seen radiation detectors in use, its not quite that easy. Also we are talking about shifting trucks from one shelter to another a couple miles away, on remote easily secured roads. Yes the decoys would also need security when moving, but you only need to shift 2-3 trucks at any one time per a group of say 10 (1 warhead, 9 decoys), so you only need 2-3 security teams.
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These are all things that were very real considerations when the MX shell game was being looked at. The OTA report on MX Missile Basing does a very good job of illustrating the difficulties of this kind of operation.

If you're not trying to hide them amongst traffic in the public road network, then you don't need to disguise the TELs as anything, of course. You still need to disguise which ones are live, but you can build them as big as necessary to do that. But, if they're operating between fixed shelters, how much of an improvement over a non-mobile system are they really?
Scott Kenny said:
Minuteman 3 is an 80,000lb missile, which is getting into oversized load rules on the highways and so needs more than 2 axles up front and 2 axles in back on the road. GBSD is likely the same size, maybe 90klbs on the upper bound. The whole TEL is then probably 100,000lbs of load or more.
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Very rough estimate, the UK haulage industry reckons you can get 26 tonnes of cargo in a 44 tonne articulated tipper. If you want to carry a 36-tonne (i.e. Minuteman 3) missile, the whole rig is unlikely to come in under 60 tonnes - and that's if the launch equipment is weightless.
Scott Kenny said:
The ideal TEL simulator is a mobile crane truck, not a semi. Lots of wheels to spread the load out as much as possible, has obvious stabilizer jacks that are necessary for the main job. But those basically don't leave urban areas very often. Might be viable for Europe, but not the US where it's a couple hundred miles between cities out west.
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Unfortunately, those also have lots of exposed machinery. It would be a real challenge to disguise a TEL as one, because it would have lots of TEL bits that don't look like crane bits, and no crane bits. Plus the entire armed convoy escorting it, which is kind of a giveaway.
Scott Kenny said:
It actually matters a whole lot with heavily hardened structures, the ones built to thousands of PSI as the standard. Those you need to plant that warhead within a few meters of the structure to destroy it.
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Thing is, a 100-kiloton weapon gets 10,000psi overpressure at just under 100 metres. Even a ten-kiloton weapon is about 45 metres. At that point, any CEP measured in single digits of metres has an effectively 100% SSPK. The dominating factor is weapon reliability.
 
bobbymike said:
www.airandspaceforces.com

Lawmakers Want Briefing on Fund to Take Sentinel Off Air Force Books

The Senate Armed Services Committee 2025 defense bill could signal a move to shift the Sentinel missile off the Air Force budget.
www.airandspaceforces.com www.airandspaceforces.com
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I was pretty much saying this earlier, if the ground based silos are going to be under the Air Force command there has to be other ways to pay for it besides from their slice of the pie. This program, as well as other Air Force priorities, are too important to have to pick and choose between. Maybe that means a global DoD nuclear budget or something similar, because we need NGAD and Sentinel.

Also like the idea of adding 50 more ready alert missiles given that we have two nuclear peers. Especially with the planned reduced fleet number of SSBNs.
 
Shoes31 said:
I was pretty much saying this earlier, if the ground based silos are going to be under the Air Force command there has to be other ways to pay for it besides from their slice of the pie. This program, as well as other Air Force priorities, are too important to have to pick and choose between. Maybe that means a global DoD nuclear budget or something similar, because we need NGAD and Sentinel.

Also like the idea of adding 50 more ready alert missiles given that we have two nuclear peers. Especially with the planned reduced fleet number of SSBNs.
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Or maybe just remove ICBM from Air Force and give them to Army?
 
Yellow Palace said:
These are all things that were very real considerations when the MX shell game was being looked at. The OTA report on MX Missile Basing does a very good job of illustrating the difficulties of this kind of operation.

If you're not trying to hide them amongst traffic in the public road network, then you don't need to disguise the TELs as anything, of course. You still need to disguise which ones are live, but you can build them as big as necessary to do that. But, if they're operating between fixed shelters, how much of an improvement over a non-mobile system are they really?

Very rough estimate, the UK haulage industry reckons you can get 26 tonnes of cargo in a 44 tonne articulated tipper. If you want to carry a 36-tonne (i.e. Minuteman 3) missile, the whole rig is unlikely to come in under 60 tonnes - and that's if the launch equipment is weightless.

Unfortunately, those also have lots of exposed machinery. It would be a real challenge to disguise a TEL as one, because it would have lots of TEL bits that don't look like crane bits, and no crane bits. Plus the entire armed convoy escorting it, which is kind of a giveaway.

Thing is, a 100-kiloton weapon gets 10,000psi overpressure at just under 100 metres. Even a ten-kiloton weapon is about 45 metres. At that point, any CEP measured in single digits of metres has an effectively 100% SSPK. The dominating factor is weapon reliability.
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The shell game comes into place when you are limited in terms of warheads or missiles due to treaties, politics, or cost.
 
The Navy probably cares alot more about the boomers than the USAF cares about GBSD.
 
Moose said:
Doing this but leaving SSBNs on the shipbuilding budget would be a hell of a pill for Navy to swallow.
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The article states that something like that already exists for the Navy, called the National Sea-Based Deterrence Fund. Googling that makes it look like the Navy uses the fund for Columbia R&D as well as procurement, as well as to help cover funds for other nuclear projects in the branch.
 
Desertfox said:
The shell game comes into place when you are limited in terms of warheads or missiles due to treaties, politics, or cost.
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We've just spent the last couple of posts bludgeoning the idea of effective decoys being significantly cheaper than more missiles to death.

All the arms reduction treaties go out the window in 2026, and are highly unlikely to be recycled for at least 20 years.

Now it's just internal politics.
 
Shoes31 said:
The article states that something like that already exists for the Navy, called the National Sea-Based Deterrence Fund. Googling that makes it look like the Navy uses the fund for Columbia R&D as well as procurement, as well as to help cover funds for other nuclear projects in the branch.
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Nooooope. The Navy, navy supporters in the Senate, and administration lobbied for what became the NSBDF starting in '14 to pay for what was then the ORP/SSBN-X design and construction from outside the Navy's existing shipbuilding budget. They predicted, and we are seeing it today, that the SSBN would put too great a strain on the relatively flat SCN funds and this would lead to other major programs being delayed or killed. The fund was created but then left without actual money in it by budget hawks until 2018. Then, 10 U.S.C. §2218a turned it from a "Congress will fund nuclear deterrence from outside the shipbuilding budget" fund into "The Navy will take the SCN money for the Columbia class and put it in this fund." So the money's still coming out of the Shipbuilding budget rather from outside that budget as originally envisioned.
 
Moose said:
Nooooope. The Navy, navy supporters in the Senate, and administration lobbied for what became the NSBDF starting in '14 to pay for what was then the ORP/SSBN-X design and construction from outside the Navy's existing shipbuilding budget. They predicted, and we are seeing it today, that the SSBN would put too great a strain on the relatively flat SCN funds and this would lead to other major programs being delayed or killed. The fund was created but then left without actual money in it by budget hawks until 2018. Then, 10 U.S.C. §2218a turned it from a "Congress will fund nuclear deterrence from outside the shipbuilding budget" fund into "The Navy will take the SCN money for the Columbia class and put it in this fund." So the money's still coming out of the Shipbuilding budget rather from outside that budget as originally envisioned.
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Why don't they give the mission to Space Force?
 
Dilandu said:
Because after all hysterical cries "RUSSIANS ARE SURELY PLANNING TO PUT NUKES ON ORBIT!!!" giving nuclear deterrence function to Space Force would be an ultimate "pay no attention to the man behind the curtain".
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What is your opinion on the US Army taking it over?
 
Changing who operates the missiles has no effect on cost, outside the fact that reassignment probably would add some administrative hoops that cost even more money. If more money is needed, that is the job of Congress, not the services.
 
So which is it? New warhead same RV, new warhead new RV or old warhead new RV?
 
www.vandenberg.spaceforce.mil

Mk21A RV TEST LAUNCH SHOWCASES READINESS

An operational test launch of an unarmed Mk21A reentry vehicle was launched from Vandenberg Space Force Base aboard a Minotaur I rocket, Monday, June 17, at 11:01 p.m. PT.The Mk21A RV is currently
www.vandenberg.spaceforce.mil
The Mk21A RV is currently under contract with Lockheed Martin for its engineering and manufacturing development phase. After attaining full operational capability, the Mk21A RV will be integrated on the nation’s intercontinental ballistic missile weapon system. The Mk21A program is currently in early development and overseen by the Air Force Nuclear Weapons Center.
 
Are there any technical-papers available online concerning the Mk-21 and/or NGRV?
 

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