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The Hybrid Missile Submarine

May 1, 2010

My thinking on the line of what may be an affordable Trident Ballistic Missile Submarine replacement, for both the US and UK, has been the cruise missile submarine. Since both nations are nearing decision time for their respective replacement programs, both also are forecasting impending doom to their respective fleets for the enormous expense of such an undertaking ($30 billion for the UK and $100 billion for the US). Each Navy has stretched themselves very thin in terms of shipbuilding resources, heavily invested as they are in the “5 Battleships“, there is no room left for extras.

Admittedly, the Tomahawk land attack missile (TLAM) is not the most desirable choice, it being principally a tactical weapon, though its range is much like that of the early Polaris missiles deployed by the RN and USN into the 1970s. Another plus is the fact that American and British boats already operate TLAM, so the transition with a nuclear version would be the simplest route to go. Problems of course, being the US plans to dispose of the last nuclear TLAM which were deployed off Japan, and the British has never utilized this version.

An alternative would be an exiting new technology New Wars reported on and which Heretic reminded us in the comments:

And, I have to wonder if Mike’s link to Navy Tests Advanced Sub-Missile Launcher might not be involved in any design of a Trident Follow On SLBM system to increase reliability and reduce the “cost” to the SSBN launcher (ie. sub) in terms of required volume of systems and so on.

The beauty of this new system recently tested by the USN in the above photo, is almost any type missile can be launched in an ascending cone of air to the surface, without, if I understand the concept correctly, any major adaptation. Anyway, this seems to take the deployment of ballistic missiles at sea, out of the box. If all new submarines, or others so converted can carry the new systems, this would not limit you to the missiles you carry, meaning, it doesn’t have to be Tomahawk on board standard SSNs like Astute or Virginia. Why can’t they carry about 4 Tridents each onboard, which are already geared for nuclear payload and can carry many MIRVs?

Still leaning toward nuclear TLAM as the most affordable and practical route, but this seems to hold merit if the retro-fitting isn’t too costly. Just a thought. I am interested in your opinion on this subject.


13 Comments leave one →
  1. Heretic permalink
    May 3, 2010 1:15 pm

    TNT = 4.6 Megajoules per kilogram

    A 1m cylindrical long rod of steel (specific gravity 7) with a 10cm diameter (10:1 length-to-width ratio) has a volume of 5^2*pi*100=7854 cm^3 and a mass of ~55 kg.

    At a velocity of Mach 1 (330 meters per second), said steel rod would have a kinetic energy of:
    0.5*55000*(330^2)=2994.75 Megajoules

    2994.75 / 4.6 = 651 kilograms of TNT “equivalent” (less than 1 ton)

    Every doubling of the Mach Number at impact increases the energy by 4x … so doing the same thing at Mach 2 is the equivalent of 2604 kilograms of TNT (2.6 tons). At Mach 16 … the proverbial “lawn dart from orbit” … you’re looking at 256x the amount of kinetic energy … which is 166.656 tons of TNT equivalent (for a 55kg steel rod).

    And that’s for a 1 meter steel rod. Other shapes exist (such as the bowling ball), but they will have increased drag, reducing impact velocity for an unpowered lawn dart.

  2. MatR permalink
    May 3, 2010 10:02 am

    Well, kinetic energy can be calculated by Ek = 1/2 mv2.

    There are plenty of online resources and defence magazines listing the CEP for Trident 1 and 2, and the M45 and M51, and their terminal speeds. Figures range from 50-200m CEP and terminal speeds of 1 to 2 km/s (it being hard to pin down because of the secrecy and all).

    Actual area coverage would depend upon whether submunitions were carried, for example, shape and composition of the warhead, what it hit, etc.

    The argument goes (not mine, I veer towards keeping conventional cruise and nuclear ballistic missiles seperate) that you wouldn’t get a super-weapon from a conventional Trident, you’d opt for it because of its high speed and the lower likelihood of it being intercepted on route. The maths behind conventional Trident is sound enough, though.

  3. ArkadyRenko permalink
    May 2, 2010 2:56 pm

    Can anyone, please, point to me a document saying the area effect of a pure kinetic energy round?

    This comes up in innumerable discussions, well, the solid metal dart has so much energy, it can devastate an area. But, in reality, I’ve seen nothing prove that.

    And continue along that path, if you’re so worried about cost. why would you:
    1) use ballistic missiles to go after targets
    2) design new ballistic missiles

    Both of the those are extremely expensive and, in the first case, completely impractable.

    I agree, that there is a asymmetry between what the US has and what the Chinese have, but that’s why Darpa is working on a variety of hypersonic gliders.

    And, about the conventional ballistic missiles being mistake for nuclear missiles. Essentially, doctrine for nuclear attack includes the idea of launch on warning, if your missiles are under attack, so that you don’t loose them. Unless you only use the ballistic missiles very infrequently, and at low value targets, then the opposition may want to launch unilaterally. But, that means that you’ve designed a weapon, and your going to use it in a un-cost effective manner. Which goes back to square one, costing too much.

    Finally, how can anyone know the CEP for the Trident, and be able to say it? Remember, even if it is 50m, that’s ridiculously accurate for an internally guided missile, fired over 5000 nm. A scud has an accuracy around a kilometer, for the basic types, and that’s a short ranged weapon. Finally, the Trident carries a nuclear warhead, so it doesn’t need to have a 1m CEP.

  4. MatR permalink
    May 2, 2010 11:26 am

    Mike Burleson: “Concerning the “conventional Trident” fears, I think that mostly comes from the other side not wanting us to have any.”

    Heh, I think you may be right! It’s a good point, given what the Chinese are working on.

    I like the idea of being able to lob lots of conventional warhead missiles at the bad guys without various parties whining that we’re on the road to armageddon if we do ;o)

    It seems to me that in Western societies, we’re our own worst enemies – a phrase I heard a historian use was that we’re highly ‘de-bellicised’. Pressure groups always looking for reasons to curtail military options during actual conflict. I disagree with the UK having banned antipersonnel landmines under all scenarios (even in things like perimeters around our nuclear plants or air bases), and having forsworn all use of cluster bombs, no matter what the circumstance (even at sea, where the risk of collateral damage is vanishingly small). I don’t think the US has experienced this trend as much as Europe has, but I see it placing restrictions in the UK on anything that looks like a ‘nasty’ weapon.

    I think the CEP for things like Trident or the French systems is maybe 50 metres? Not so pinpoint. Great for things like oil refineries or factories, though, and a huge impact at high mach numbers.

  5. Mike Burleson permalink*
    May 1, 2010 7:34 pm

    “Trident missiles have the following advantages: They are accurate, they are fast, and their launchers are hidden.”

    All true, though you left out one thing: they are no longer affordable. I agree with all you said. All we’re doing is trying to save the deterrent.

    I hope the two navies can keep what they got, but lets don’t kid ourselves.

  6. ArkadyRenko permalink
    May 1, 2010 5:27 pm

    To put it bluntly:

    What targets are worth a trident missile in cost terms? Not that many.

    Why would you want to expose your nuclear deterrent? Remember, SSBNs were designed to hide, not to engage in conventional warfare. Only when they’ve been removed from deterrence patrols are they given conventional missions.

    Finally, what happens if the target for the nuclear cruise missile happens to be an enemy missile fueling on a launching pad? Are you going to wait the 2 to 3 hours for the cruise missile to hit its target? Or, do you want to hit it in 30 minutes.

    Trident missiles have the following advantages: They are accurate, they are fast, and their launchers are hidden. Switching to a hybrid missile submarine is defeats those attributes.

    However, should submarines carry a wider range of weapons? Yes. Should they launch different surface to surface and surface to air missiles? Yes. But, combat missions and strategic deterrence missions should be kept separate.

    Because, if your combat SSN is carrying a Trident missile in its launch tubes, it cannot carry 6 tomahawk missiles. Thus, the submarines conventional combat capability is severely compromised. Even worse, because the sub is on nuclear patrol, the amount of missions it will be allowed to do will be far less.

    The solution to the SSBN replacement issue is to build the deterrence subs not on the Navy budget, but on a different budget, a special strategic systems budget. Or just give up the nuclear weapon thing altogether.

  7. Hudson permalink
    May 1, 2010 11:30 am

    Trident is more sophisticated than Scud, hence more accurate, maybe even down to 10 m CEP. However, Iraqi Scuds might have been equipped with primitive GPS guidance. It’s still a dangerous missile.

    Regarding the advanced missile launcher, or any silo launcher, really, you would not need to build an entire sub to make it work. You could construct a block of launchers and tow it underwater in coastal waters, like an underwater train–much cheaper than a full-rigged sub.


    Do we really want that? I say we want to keep these weapons awe inspiring and few and far between rather than cheap and handy like a briefcase (I know baby nukes already exist.). ‘Cause once these things start flying around, as I fear they someday will, there will not be holes deep enough for us to hide in.

  8. Mike Burleson permalink*
    May 1, 2010 7:45 am

    I don’t think ballistic missiles are any more accurate. Seem to recall those Scud missiles in the Gulf Wars going just everywhere. Also, concerning the “conventional Trident” fears, I think that mostly comes from the other side not wanting us to have any.

    Though not sub based, our potential adversaries like China have been arming themselves with conventional ballistic missiles for years, including the Dong Feng 21, which comes in nuclear or conventional versions. I think the alarms are being raised, as with the Tomahawk in the 1970s, because they know we can build this better than they can, concerning accuracy.

  9. MatR permalink
    May 1, 2010 7:34 am

    I’d opt for a ballistic missile on a sub. I’m a bit scared of putting nukes on a cruise missile. I don’t think nuclear cruise missiles are impossible to get right, but they need to be matured into a safer system, perhaps? (That might be entirely possible, I concede.)

    With current models, there’s a good chance the missile will ‘slalom’ into terrain, fail to boost, or be shot down, leaving a possibly intact warhead on someone else’s territory. gives the successful use of tomahawks at ‘over 85%’.

    Tomahawks have previously gone astray in Turkey and Pakistan. In 1998 US-destroyers fired Tomahawk missiles at Taliban bases in Afghanistan. Six of these missiles misfired and landed in Pakistan, and rumours abound that Pakistan reverse engineered them to produce its new Babur cruise missile, that looks for all the world like a Tomahawk. And if the Pakistanis have something, their allies the Chinese will soon have it.

    Defence Today had an article a while back that pointed out that accurate, reliable targeting is the biggest issue for cruise missile designs.

    Click to access DT-CM-Guidance-June-2009.pdf

    GPS can be jammed around key installations because the GPS satellites pump out a terribly weak signal, and plenty of people sell GPS jammers, like the Chinese and the Russians. The British and Americans have experimented with them too, because the technology is incredibly cheap. I wouldn’t rule out a nuclear cruise missile being spoofed to a false target many kilometres astray: which would necessitate a much lager warhead to compensate for the worse circular error probability, and therefore much worse collateral damage and fallout.

    Assuming that the missile’s warhead is a much ‘cleaner’ neutron bomb, the problem persists because neutron bombs have a relatively small effective blast radius, and therefore need very accurate targeting.

    Terrain contour matching, starlight navigation, laser gyros and other forms of navigation can’t 99% guarantee an accurate hit, having their own technical problems. If your warhead is just a conventional blast or penetration model, missing the intended target isn’t so scary.

    Perhaps nuclear cruise missiles could be used against coastal targets, safer in the knowledge that if one was downed, the sea would do a good job of hiding it? In that case, they would be a weapon with limited use, but a very small price tag.

    One thing I’ve just thought of – isn’t one of the main arguments against conventional Trident that adversaries would be panicked into thinking you’d launched a nuke at them, and retaliate in kind before they were hit? Nuclear tipped cruise missiles might face the same problem, in that they would make it much harder to use your non-nuclear cruise missiles.

  10. Mike Burleson permalink*
    May 1, 2010 7:15 am

    “I have a few doubts if this system is applicable to all missiles”

    I didn’t know, but like you I love the concept. Missiles are so flexible, versatile, and varied–it would be great if you could enhance the abilities of the basic submarine even more. Plus a little scary.

  11. Marcase permalink
    May 1, 2010 6:38 am

    I have a few doubts if this system is applicable to all missiles, especially huge SLBM types and ofcourse those cruise missiles that only use a small booster to get clear of the ship/surface before their cruise engines kick in.

    Does promises great potential though.

    I really like the larger ‘six shooter’ missile silos, as currently being installed in SSN-774.

    Although a Trident won’t fit, it is large and modular enough to turn any outfitted (fleet) submarine into a missile platform, without the usual (533mm) restrictions.


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