Surface Ships Need More Offensive Punch, Outlook

[marauder2048]

Funnily enough, a notional cruiser design space exploration paper did a include a 12 MW, 450 metric ton laser AAW system.

 

[sferrin]

Exactly. That's why I think the Zumwalt is the obvious choice. It's got the power, the speed, and is available today.

It may or may not have the power for today. It certainly doesn't have the power for a 35-50 yr ship. The US is building Ford class with a 100% margin for power. I don't see 100% margin for power with 'today's Zumwalt.

A cruiser isn't an aircraft carrier. Furthermore the Zumwalt has a lot more margin, volume wise, than any conceivable Burke variant. Obviously one could build a Kirov analog but the unit cost would be so high as to be impractical.

I'm not convinced Zumwalt can carry a Ford class reactor. So now one has to look at either another existing reactor that has enough power. Is there one? If not, then you have to develop a new reactor or make a bigger Zumwalt. Or - you can use an existing hull with an existing reactor.

Or you do like every other US nuclear surface combatant and use a pair of reactors (which you'd want to do anyway to avoid a single-point-of-failure). A pair of the reactors being developed for the Columbus class should fit the bill.

The lost opportunity cost is dealing with two solutions, a conventionally powered Zumwalt and a nuclear powered Zumwalt. It's a waste of time, effort and training.

Ship design - X2
Ship production systems - X2
Ship building - X2
Training of the ship builders - X2

Efficiencies are driven by repetition. Look at the price management and schedule reduction with Virginia class. Want to drive the cost down on a cruiser? Build the same one over and over for 10 years. Then build it over and over for another 10 years. The extra production may assist in Ford cost management as well.

In principle I'd agree with you but the USN is trying to reconstitute the fleet ASAP and a flight of conventionally powered Zumwalt-based cruisers will get ships delivered sooner and buy you the time necessary to get the nuclear power worked out. It's not unprecedented. The Bainbridge was basically a nuclear powered Leahy.

I've got nothing against Zumwalt. I'm just not convinced it has the power or size to be a 40-50 year solution as a BMD ship. You don't either since you propose a nuclear powered "flight ii".

You're twisting my words. I am convinced the Zumwalt hull and machinery is the way to go. I did NOT say, "slap a "CG" in place of the "DDG" and call it good".

You can't retrofit nuclear propulsion into hulls. You can retrofit just about anything else in a hull.

Again, you're twisting my words. I'm not suggesting you rip the guts out of DDG-1000 to -1002 and convert them to nuclear power. I'm saying that a Flight II could could be redesigned for nuclear power, and maybe Flight III (or the Flight II) gets the stretched hull mentioned elsewhere in the thread.

Perhaps I'm missing the obvious but I don't see the requirement for 30+ knots. It would be nice but it's not necessary. And speed is the only advantage I see with the Zumwalt hull. All the other advantages I see with a Level 3 San Antonio.

Speed, maneuverability, survivability, cost. The only advantage a San Antonio would have is it's big. By the time you've made it into a combatant it would be so expensive you may as well have built the Kirov.

 

[marauder2048]

Wasn't the motivation for two reactors a federated design where one reactor was coupled to one propeller?

I think in all of the studies over the past decade+ the Navy only looked at single reactor arrangements
typically of the nuclear IPS style; the "medium surface combatant" specs were quite eye-watering.

 

[sferrin]

Wasn't the motivation for two reactors a federated design where one reactor was coupled to one propeller?

It may have been because they didn't have a single reactor available of sufficient power. That's why Enterprise had 8 reactors, two to a shaft.

; the "medium surface combatant" specs were quite eye-watering.

Damn. :'(

 

[NeilChapman]

Speed, maneuverability, survivability, cost. The only advantage a San Antonio would have is it's big. By the time you've made it into a combatant it would be so expensive you may as well have built the Kirov.

Perhaps, if it were built by the Russians. But I should like to hear your reasoning. Why would a BMD cruiser built on a San Antonio hull be so expensive as to be impractical, and, to what dollar amount does "so expensive" equates?

 

[sferrin]

Why would a BMD cruiser built on a San Antonio hull be so expensive as to be impractical, and, to what dollar amount does "so expensive" equates?

It would require an almost complete redesign. Most of the deck space is unusable for VLS or guns because there's a hangar beneath it. It's too slow. It's less maneuverable and has a larger RCS than the Zumwalt. It's $2 billion as is and it's mostly a hollow tin can. As for dollar amount it's "whatever is too high to afford 20- 30 of them".

 

[Mark S.]

Would assume one of the design requirements of the new cruiser is that it has to keep up with the carriers. So that makes it a 35 knot ship. It would be too expensive and take too long to design a new nuclear reactor and test it to power the vessel. Additionally the hull shape needs to be efficient at higher speeds to minimize use of the power plant for propulsion and maximize it for radars and weapons. The requirements point to a Zumwalt hull with a conventional power plant. The outliers would be a scaled up Burke hull with conventional power or maybe a America hull with a single reactor from the Ford class. The America solution only if the hull was designed for high speed and that it could be cut down to the level of the hangar deck without a reduction in strength. A vessel that size would have a huge growth potential.

 

[Colonial-Marine]

Using a variation of the Zumwalt's hull certainly seems like a viable option as it seems to have the size and the potential to provide enough power. Yet I must admit I am still a bit concerned about the Zumwalt's hull form despite all of the testing that has been done. Has DDG-1000 herself weathered any North Atlantic storms yet?

A hull based on the San Antonio class doesn't seem that great an option unless you intend to park the ship off of some global hotspot and stay there. I think it's more important to have a ship that can keep up with the carrier battle group at 30+ knots and protect it.

Otherwise how hard would it really be for the US to design a new conventional hull sized for a large cruiser with heavy power requirements?

 

[marauder2048]

We've only considered single reactor or dual reactor nuclear powered ships but the RAND study on future carriers
did consider an IPS-based nuclear-GTG hybrid. That might make a single S1B feasible.

 

[marauder2048]

More color on the 57mm Alamo. They are looking to scale it to 76mm and 5-inch.

https://www.youtube.com/watch?v=6keezPwOXRI&t=4s

 

[Moose]

Otherwise how hard would it really be for the US to design a new conventional hull sized for a large cruiser with heavy power requirements?

"Hard" can be defined many ways, we could absolutely do it, but at cost. Generally, it would take additional money and time versus a mild adaptation of an existing hull. How much many and how much time, well that's the question isn't it?

 

[bobbymike]

https://news.usni.org/2018/04/20/navy-leadership-looking-at-lpd-flight-ii-missiles-additional-virginia-class-buys

CAPITOL HILL – Navy and Marine Corps leaders are mulling if and how to up-gun the San Antonio-class LPD Flight II ships; whether to buy more attack submarines and how to extend the lives of a handful of Los Angeles-class; and other ideas to increase the size and the lethality of the fleet in the near- to mid-term.

Top Navy leadership testified at two hearings with the Senate Armed Services Committee this week and addressed several ship classes that are important to fleet operations today and going forward.

 

[sferrin]

https://news.usni.org/2018/04/20/navy-leadership-looking-at-lpd-flight-ii-missiles-additional-virginia-class-buys

CAPITOL HILL – Navy and Marine Corps leaders are mulling if and how to up-gun the San Antonio-class LPD Flight II ships; whether to buy more attack submarines and how to extend the lives of a handful of Los Angeles-class; and other ideas to increase the size and the lethality of the fleet in the near- to mid-term.

Top Navy leadership testified at two hearings with the Senate Armed Services Committee this week and addressed several ship classes that are important to fleet operations today and going forward.

This would be mainly putting VLS cells for Tomahawks and maybe ESSM onboard.

 

[marauder2048]

I think we discussed this in another thread, but BAE's McCullough was pointing out that the MK 132
cannot accommodate the weight of 8 x ESSM Blk IIs. The Adaptable Deck Launcher (in some form) is
being pitched as a replacement.

 

[sferrin]

I think we discussed this in another thread, but BAE's McCullough was pointing out that the MK 132
cannot accommodate the weight of 8 x ESSM Blk IIs. The Adaptable Deck Launcher (in some form) is
being pitched as a replacement.

There are always the VLS cells. (Why would you think there would be an 8-cell Sparrow mount? San Antonios don't have them.)

 

[Moose]

I think we discussed this in another thread, but BAE's McCullough was pointing out that the MK 132
cannot accommodate the weight of 8 x ESSM Blk IIs. The Adaptable Deck Launcher (in some form) is
being pitched as a replacement.

An upgrade for MK132 to handle ESSM Block II has gone to RFI.

 

[marauder2048]

I think we discussed this in another thread, but BAE's McCullough was pointing out that the MK 132
cannot accommodate the weight of 8 x ESSM Blk IIs. The Adaptable Deck Launcher (in some form) is
being pitched as a replacement.

There are always the VLS cells. (Why would you think there would be an 8-cell Sparrow mount? San Antonios don't have them.)

Forgive my Monday-morning incoherency: the Adaptable deck launcher gets a mention in the article and
is being pitched as a Mk 132 replacement on the Nimitz and Ford class and a firepower enhancement on LCS.

 

[sferrin]

I think we discussed this in another thread, but BAE's McCullough was pointing out that the MK 132
cannot accommodate the weight of 8 x ESSM Blk IIs. The Adaptable Deck Launcher (in some form) is
being pitched as a replacement.

There are always the VLS cells. (Why would you think there would be an 8-cell Sparrow mount? San Antonios don't have them.)

Forgive my Monday-morning incoherency: the Adaptable deck launcher gets a mention in the article and
is being pitched as a Mk 132 replacement on the Nimitz and Ford class and a firepower enhancement on LCS.

You'd think there would be enough space for a set of Self-Defense length Mk41 VLS. One in each aft sponson (of the CVNs) would give them 64 ESSMs.

 

[marauder2048]

The typical argument against VLS for self-defense has been the increased minimum engagement distances for ESSM but
maybe RAM Blk II in the trainable launchers makes that less relevant.

 

[jsport]

Cruisers would seem to be the only sensible ship to focus on at this time. As the future is now. The energy requirements demand a ship large enough for a reactor to support:

-even PBWs (necessary for next gen BMD)

Particle Based Weapons don’t work well in atmosphere, and lasers trying to reach high enough to hit an ascending missile or descending warhead are going to be subject to beam-wander because of air density variactions.

The assessment may be different if the lasers are defending the ship and its charges.

would argue as higher energy lasers are perfected and burn through air density etc. then potentially a PBW designed to project from within that LF beam weapon could deliver instantaneous KE (PBW some assume is a KE wpn not a DEW wpn ) effects at longer range.

 

[bobbymike]

Hopefully this one doesn't count towards the 355 ship fleet.

 

[sferrin]

That's the USS Safe Space.

 

[TomS]

It's apparently assigned to USS Constitution. Her website refers to it as a "beaver boat" -- a little tugboat they used to haul Constitution out of drydock and to handle lines and booms around the dock.

 

[jsport]

Cruisers would seem to be the only sensible ship to focus on at this time. As the future is now. The energy requirements demand a ship large enough for a reactor to support:

-even PBWs (necessary for next gen BMD)

Particle Based Weapons don’t work well in atmosphere, and lasers trying to reach high enough to hit an ascending missile or descending warhead are going to be subject to beam-wander because of air density variactions.

The assessment may be different if the lasers are defending the ship and its charges.

would argue as higher energy lasers are perfected and burn through air density etc. then potentially a PBW designed to project from within that LF beam weapon could deliver instantaneous KE (some assume PBW is a KE wpn not necessarily a DEW wpn ) effects at longer range.

The USN shipborne PBW program was called Chair Heritage.
starts pg 34
http://sill-www.army.mil/firesbulletin/archives/1980/JAN_FEB_1980/JAN_FEB_1980_FULL_EDITION.pdf

a possible way to have a chance against hypersonics.

 

[bobbymike]

https://www.naval-technology.com/features/sizing-us-navys-future-guided-missile-frigate-designs/

In January this year, at the US Surface Navy Association Symposium in Washington DC, Dr Regan Campbell, PMS515 program manager at the US Navy’s Naval Sea Systems Command (NAVSEA), gave attendees an update on one of the major future procurements for the service.

Campbell is in charge of PMS515, which has responsibility for the evaluation and initial procurement of the US Navy’s FFG(X) next generation frigate. The frigate will become the backbone of the navy’s future capability with 20 ships expected to be procured.

According to Campbell, FFG(X) will be an “agile, multi-mission platform designed for operation in littoral and blue water environments”. It should be able to operate independently or integrate with a task force to conduct offensive and defensive surface, anti-submarine, and air warfare roles.

 

[sferrin]

https://www.naval-technology.com/features/sizing-us-navys-future-guided-missile-frigate-designs/

In January this year, at the US Surface Navy Association Symposium in Washington DC, Dr Regan Campbell, PMS515 program manager at the US Navy’s Naval Sea Systems Command (NAVSEA), gave attendees an update on one of the major future procurements for the service.

Campbell is in charge of PMS515, which has responsibility for the evaluation and initial procurement of the US Navy’s FFG(X) next generation frigate. The frigate will become the backbone of the navy’s future capability with 20 ships expected to be procured.

According to Campbell, FFG(X) will be an “agile, multi-mission platform designed for operation in littoral and blue water environments”. It should be able to operate independently or integrate with a task force to conduct offensive and defensive surface, anti-submarine, and air warfare roles.

"The frigate will become the backbone of the navy’s future capability with 20 ships expected to be procured."

Strange he'd consider 20 frigates to be the "backbone" rather than ~80 Burkes.

 

[TomS]

Dr. Campbell is a woman.

I suspect she's referring to the idea that the frigates are going to be a larger proportion of future construction. Eventually, FFG(X) production should outnumber new CG/DDG construction.

 

[sferrin]

Dr. Campbell is a woman.

I suspect she's referring to the idea that the frigates are going to be a larger proportion of future construction. Eventually, FFG(X) production should outnumber new CG/DDG construction.

Well she said, "backbone of the navy’s future capability". She didn't specify construction. That suggests, if a small number of frigate is going to replace a large number of destroyers, that the USN will experience a significant downturn in "future capability".

 

[TomS]

Well she said, "backbone of the navy’s future capability". She didn't specify construction. That suggests, if a small number of frigate is going to replace a large number of destroyers, that the USN will experience a significant downturn in "future capability".

Thing is, it's a very short quote out of a longer speech. "Future capability" can refer to "capability that we will have in the future" or "capability we will add in the future" or any one of a number of things, depending on the rest of the speech. I'm sure there's a lot more context where it makes sense. I don't think it's useful to snipe at such things. It makes us feel smart, but it implies that the people who actually run the programs don't know basic things like what the future force structure looks like, which I guarantee isn't true.

 

[sferrin]

Well she said, "backbone of the navy’s future capability". She didn't specify construction. That suggests, if a small number of frigate is going to replace a large number of destroyers, that the USN will experience a significant downturn in "future capability".

Thing is, it's a very short quote out of a longer speech. "Future capability" can refer to "capability that we will have in the future" or "capability we will add in the future" or any one of a number of things, depending on the rest of the speech. I'm sure there's a lot more context where it makes sense. I don't think it's useful to snipe at such things. It makes us feel smart, but it implies that the people who actually run the programs don't know basic things like what the future force structure looks like, which I guarantee isn't true.

I took it more as an effort at a sales pitch / marketing. "Don't you see? We NEED these frigates because they're going to be the BACKBONE of our fleet in the future." More than a little hyperbole.

 

[bobbymike]

https://www.usni.org/magazines/proceedings/2018-05/build-great-white-fleet-21st-century

What has changed, and how?

The 21st century presents two stark naval realities: Technological advantage between navies in the information age makes competitive gains shorter-lived and increasingly costly, and the pace of maritime globalization continues to accelerate from Africa to South and Central America, as well from Asia to North America, with increasing corruption. The U.S. Coast Guard, an armed force and an integral part of the national fleet, is uniquely qualified to answer the geographic combatant commands’ (GCCs) force requirements by leveraging vast authorities; capabilities; and interservice, interagency, intelligence community, and international partnerships. Unfortunately, national investment in the Coast Guard is insufficient to provide the capacity necessary to combat the full wave of threats to U.S. shores. The current operational approach is costly and does not give the United States sufficient capacity to maintain a sustainable maritime presence or achieve meaningful global partnerships. “U.S. forward naval presence is essential to accomplishing the following naval missions derived from national guidance: defend the homeland, deter conflict, respond to crises, defeat aggression, protect the maritime commons, strengthen partnerships, and provide humanitarian assistance and disaster response.”1 The Chairman of the Joint Chiefs of Staff’s “Joint Operating Environment 2035” states, “Ultimately, the future Joint Force will best contribute to a peaceful and stable world through well-crafted operational approaches attuned to the evolving character of conflict.” The fleet balance needs to be re-examined to help close this strategy-capability-capacity gap.

 

[Moose]

The Kongsberg-Raytheon Naval Strike Missile has won the competition to arm the LCS and FFG(X) with an Over-The-Horizon ASM.

 

[bobbymike]

https://www.defensenews.com/naval/2018/06/16/the-us-navy-is-fed-up-with-ballistic-missile-defense-patrols/?utm_campaign=Socialflow&utm_source=twitter.com&utm_medium=social

The U.S. Navy’s top officer wants to end standing ballistic missile defense patrols and transfer the mission to shore-based assets.

Chief of Naval Operations Adm. John Richardson said in no uncertain terms Tuesday that he wants the Navy off the tether of ballistic missile defense patrols, a mission that has put a growing strain on the Navy’s hard-worn surface combatants, and shifted towards more shore-based infrastructure.

“Right now, as we speak, I have six multi-mission, very sophisticated, dynamic cruisers and destroyers -- six of them are on ballistic missile defense duty at sea,” Richardson said during his address at the U.S. Naval War College’s Current Strategy Forum. “And if you know a little bit about this business you know that geometry is a tyrant.

“You have to be in a tiny little box to have a chance at intercepting that incoming missile. So, we have six ships that could go anywhere in the world, at flank speed, in a tiny little box, defending land.”

 

[jsport]

https://www.defensenews.com/naval/2018/06/16/the-us-navy-is-fed-up-with-ballistic-missile-defense-patrols/?utm_campaign=Socialflow&utm_source=twitter.com&utm_medium=social

The U.S. Navy’s top officer wants to end standing ballistic missile defense patrols and transfer the mission to shore-based assets.

Chief of Naval Operations Adm. John Richardson said in no uncertain terms Tuesday that he wants the Navy off the tether of ballistic missile defense patrols, a mission that has put a growing strain on the Navy’s hard-worn surface combatants, and shifted towards more shore-based infrastructure.

“Right now, as we speak, I have six multi-mission, very sophisticated, dynamic cruisers and destroyers -- six of them are on ballistic missile defense duty at sea,” Richardson said during his address at the U.S. Naval War College’s Current Strategy Forum. “And if you know a little bit about this business you know that geometry is a tyrant.

“You have to be in a tiny little box to have a chance at intercepting that incoming missile. So, we have six ships that could go anywhere in the world, at flank speed, in a tiny little box, defending land.”

This is why the case for dedicated ABM ships has always been a valid one.

 

[Airplane]

https://www.defensenews.com/naval/2018/06/16/the-us-navy-is-fed-up-with-ballistic-missile-defense-patrols/?utm_campaign=Socialflow&utm_source=twitter.com&utm_medium=social

The U.S. Navy’s top officer wants to end standing ballistic missile defense patrols and transfer the mission to shore-based assets.

Chief of Naval Operations Adm. John Richardson said in no uncertain terms Tuesday that he wants the Navy off the tether of ballistic missile defense patrols, a mission that has put a growing strain on the Navy’s hard-worn surface combatants, and shifted towards more shore-based infrastructure.

“Right now, as we speak, I have six multi-mission, very sophisticated, dynamic cruisers and destroyers -- six of them are on ballistic missile defense duty at sea,” Richardson said during his address at the U.S. Naval War College’s Current Strategy Forum. “And if you know a little bit about this business you know that geometry is a tyrant.

“You have to be in a tiny little box to have a chance at intercepting that incoming missile. So, we have six ships that could go anywhere in the world, at flank speed, in a tiny little box, defending land.”

This is why the case for dedicated ABM ships has always been a valid one.

Serving on ships is harder than you imagine... Even carriers for that matter. That is unless you're fortunate enough to have outdoor duties or at least a window.

Life on a dedicated ABM ship relegated to patrolling tiny little swaths of sea would be worse than what I hear missile silo duty is like. Having only one mission... One small patrol area... Service on that ship would be torture.

 

[fredymac]

Serving on ships is harder than you imagine... Even carriers for that matter. That is unless you're fortunate enough to have outdoor duties or at least a window.

Life on a dedicated ABM ship relegated to patrolling tiny little swaths of sea would be worse than what I hear missile silo duty is like. Having only one mission... One small patrol area... Service on that ship would be torture.

Once SM3 Block 2 phases in those “tiny” patrol areas will open up. If a dedicated ABM patrol ship is built, even bigger missile could be accommodated allowing the ship to move along most of the predicted trajectory ground tracks.

Being cooped up in cramped settings is a good description of 50 years of SSBN duty. No window and no idea where you are for extended periods and yet they have managed somehow.

 

[bobbymike]

https://breakingdefense.com/2018/06/keep-ships-longer-to-boost-fleet-size-355-ships-by-2035/

WASHINGTON: The Navy can cut 20 years off the time to grow to its target of 355 ships, the service’s chief shipbuilder said today, if it invests more in maintaining and upgrading its current vessels so it can keep them longer. Instead of growing from 284 ships now to 355 in 2052-2055, the timeframe officials cited in the past, the Navy could reach its goal in 2032-2035, said Vice Adm. Thomas Moore, chief of Naval Sea Systems Command (NAVSEA).
Navy photo

Admirals were already telling Congress that just building new ships faster was not enough if you retire old ships at the same rate. It’s a classic case of two steps forward, one step back. You get to 355 far too slowly to serve the new National Defense Strategy, with its emphasis on near-term great power competition.

“Even if you’re going to build at the maximum rate possible… based on the capacity we have today (and) when we take ships out service… we don’t get to 355 until 2052,” Moore said. “That’s not something you want to put on a bumper sticker.

 

[jsport]

Serving on ships is harder than you imagine... Even carriers for that matter. That is unless you're fortunate enough to have outdoor duties or at least a window.

Life on a dedicated ABM ship relegated to patrolling tiny little swaths of sea would be worse than what I hear missile silo duty is like. Having only one mission... One small patrol area... Service on that ship would be torture.

How about the much touted automated ship w/ a few rotated in contractors but otherwise as automated as possible. Ship has only one role.


Once SM3 Block 2 phases in those “tiny” patrol areas will open up. If a dedicated ABM patrol ship is built, even bigger missile could be accommodated allowing the ship to move along most of the predicted trajectory ground tracks.

Being cooped up in cramped settings is a good description of 50 years of SSBN duty. No window and no idea where you are for extended periods and yet they have managed somehow.

 

[TomS]

I don't see how a dedicated BMD ship results in a dramatic savings.

A dedicated BMD ship needs almost all of the systems as a full-mission capable cruiser -- air defense/BMD radar, missile launchers, fire control, C4 systems, etc. It needs ASW and cruise missile defense capabilities so it can self-protect against someone who tries to clear the way for a missile strike by attacking the BMD assets. About the only parts of a cruiser's weapon systems you could delete would be the main guns and antiship missiles. I suppose you could also scale back the number of stowed antiaircraft missiles since you really need only a self-defense capability. It needs to be built to robust damage control standards, especially since it may be stationed away from other fleet assets and needs to keep its crew alive after an attack or accident. It needs relatively high speed to reposition in the event of a changed tactical environment -- if the primary threat shifts from Japan to Guam, the BMD stations need to move.

Also, the feasibility of leaving ships on station for protracted periods is questionable -- we've experimented with it and the outcomes are not what was hoped. At best, you could do a Blue-Gold deployment, but you need long transit and overhaul periods as well, so the actual availability gain isn't that huge.

So, with dedicated BMD ships, you still need at least 75% of the cost of a full on cruiser, and at least 75% as many ships. So maybe you save 40% or so compared to cruisers.

In contrast, shore-based facilities don't need lots of other systems for protection, don't need propulsion, don't need to rotate for overhauls, and don't need lots of maintenance downtime. Japan's planned AEGIS Ashore procurement of two systems is projected to come in at ~$1.8 billion, about the same as one cruiser. It will provide coverage that would require at least a half-dozen ships to match. That's <20% of the total cost of doing the mission with cruisers and a third the cost of doing with dedicated BMD ships.

 

[fredymac]

A dedicated ABM ship (or sub) would tailor the missile compartment to fit anything from a KEI to a full size GMD both equipped with high MKV count payloads. A sub based system would actually throw in uncertainty so nobody would know if you were sitting close enough for a boost phase intercept.

If you were positioned near the apogee of the ground track, you might still intercept in "bus phase" before warheads separate. Unless you go to space based interceptors this is the best alternative. Sticking to land sites mean you are essentially putting your assets at the target and the best you can hope is to intercept near the mid point of the trajectory after the warheads have separated.

The operational employment might be similar to an SSBN patrol. For a sub based system, you wouldn't need escorts (unless ASW technology has a breakthrough). For surface ships, you would be a very tempting target and would either need escorts or wind up looking like an LHD with a complement of F-35Bs. Until lasers and railguns develop to the point where they can reach up to ICBM warheads, a submarine would seem to be the better solution.