The fixed missile silos out in the middle of nowhere (sorry Montana!) serve a lot of useful purposes. If you do not intend to be the one who pushes the button and destroys the entire world, it is nice having weapons like that precisely because the adversary can see whether or not you've fired them. If the enemy can see that your ICBMs haven't launched and your bombers aren't in range to fire their cruise missiles, they know you haven't gone all the way. Additionally, silos like that are something the adversary must target if they have any hope to survive, which is one less warhead they can drop somewhere else (an air base, fleet, city, or whatever).
A submarine is inherently less predictable, yes, and in terms of ratcheting down tensions that is not always great.
One additional reason, that the enemy would have to destroy a large amount of American territory to realistically neutralize the threat. They can’t just target some military bases and subs in an attempt to cripple us while attempting to keep it limited. No half measures.
This doesn't work since you can't really prove that your opponent doesn't know the secret or changing locations - either out of sabotage or technical advancement.
I can't imagine any sort of sabotage that would make SSBNs easier to locate without also being obvious to the crew. As for technical advancements, what are you thinking of there within the current laws of physics? No other country has the economic resources to blanket the ocean with detection platforms. Some researchers have proposed using satellites to detect submarine wakes but that would take a huge constellation and could only even potentially work if the sub was moving fast at a shallow depth.
SSBN stealth could be at risk by mid-century if current technologies continue to advance in surveillance and information processing. That would be enormously destabilizing from a grand strategic perspective but is still very much a future worry not a contemporary problem yet.
The two which I’ve read are concerning are using the ferromagnetic material in a sub to detect tiny variations in the magnetic field using supercooled sensors and just better computers and acoustic sensors to extract more signal from well below the noise floor.
There’s also some more science fiction level technologies proposed like using the nuclear signature of a sub’s reactor or using space based LIDAR to detect signs of the wake of a submerged submarine but I’ll defer judgment on those for now. But longer term I wouldn’t completely count them out.
PLAN copying / rotating fleet of DARPA ACTUV (ASW Continuous Trail Unmanned Vessel). Park them outside sub home ports (outside of territorial waters / contiguous zone but within active sonar range) and blast sonar to keep continuous track once they're underway. Likely then hand off to faster/more powerful surface ASW platforms. Combine with rumored mini nuke boats from PLAN, especially if autonomous improves to drastically reduce manning (less mouths to feed to match endurance of big nuke boats), basically tailgate nuke boats the second they leave parking lot. Trumpet following girl meme. Economically, hard to say, but only fraction of very expensive to operate 14 boomers/SSNs on deterrent patrol at any given time.
That said, IMO hardly matters, sea/air leg of triad can be replaced by redundant / distributed land, not silos but road mobile TELs in hardened shelters probably for MUCH cheaper per warhead - PLA/PLARF model. Can have 1000s of cheap TEL trucks / fake warheads to play shell game and be just as impossible to decapitation strike as a few SSNs with 20 missiles. Mobile land leg just politically not sensible because it means unambigiously painting target on homeland, not just empty silo fields in bumfuck nowhere. IMO half the reason of sea/air leg now is they're out of sight/out of mind doing distant patrols. No one wants to see a nuclear TEL driving down the highway and process implications. If anti missile defense improves, cost/benefit of limited magazine SSNs gets even worse - a tube on a 2.5B+ nuke boat cost 100m to acquire + likely very expensive operation costs per shot to field. You can buy 500+ HEMTT 8x8 to hull around solid fuel ICBMs for that price. PRC can probably buy 1,000. Economics of nuke boats as delivery platforms outside of psychology does not seem to make sense, but civilian psychology when it comes to nuclear planning is very important.
Darpa toying with ACTUV expliclity because it was _dirt_ cheap vs relying on large surface combatants + air for ASW - small hulls with 10-20k per day operating cost vs 500k-800k per day ASW destroyer (US costs). It would be cheap to build out a fleet of ~50 small autonomous / minimally manned surface/subsurface fleet to follow the handful of SSNs on deployment at any given time. 30-80 ACTUV for surface ASW (US costs) is already 5-10 shadowing each deterrent patrol SSN. Economy of scale enters picture even if nuclear powered - danger is mostly political, parking reactors in adversaries EEZs. PLA relative cost vs USN acquiring/maintaining SSNs likely much cheaper / lopsided. Look at PRC's 80 type 22s that existed basically on the hope that it can deter the 1-2 carriers US normally throws in theatre.
As for mobile TEL / mobile land triad, like 30k+ HEMTT+LVSR has been built, and that's just Oshkosh Defense building tactical trucks. # of USD 300-500k heavy/tactical trucks globally in 100,000s. Add in land infra/tunnel/harden costs and you won't get close to 100m per shot. Can probably get Oshkosh to hammer out budget decoy TELs with autonomous driving without any of the the expensive TEL/launch hardware. Say what you will about US industry, US auto still pretty capable of building things that roll on wheels vs US ship building. SSNX is projected to be 5-7B per unit (200m+ per launch tube), that buys you a lot of road mobile launchers. E: USN plants to acquire like 30 of them. I would be very surprised PLAN needs to spend 150-200B on a ASW UAV fleet to counter that. That's ~400-600 054s frigates. An ACTUV drone would cost fraction of manned frigates. I think you're dramatically underestimating just how expensive US SSN force is / will projected to be and how economics will incentivize scope of counters.
