Monday, June 12, 2017

Surface Ship Torpedoes

In a previous post, we touched on the subject of anti-surface torpedo tubes in surface ships.  Yes, many ships today have torpedo tubes but the majority are intended for anti-submarine use and utilize lightweight torpedoes.  The US Navy’s standard surface ship torpedo armament is the Mk32 triple tube launcher with Mk46/50/54 lightweight anti-submarine torpedoes.  These torpedoes may or may not have an anti-surface ship mode but they are not ship killers.  The ship killing torpedo in the US Navy is the Mk48 ADCAP (Advanced CAPability) heavy torpedo and even this is intended primarily as an anti-submarine weapon.

                 Mk 48        Mk54         Mk50         Mk46

Range, yds       35000        ?            16000        12000
Speed, kts       55 (63?)     40+          50+          45
Diameter, in/mm  21/533       12.75/324    12.75/324    12.75/324
Length           29’2”        8’11”        9’6”         8’6”
Weight, lbs      3450         608          800          508
Warhead, lbs     650          95           100          95
Cost             $2.4M(FY88)  $0.8M(FY14)  $1M(FY02)

For comparison, here are a couple of the main Russian Torpedoes.

                 Type 65      Type 53 UGST (2)

Range, miles     62@35mph     25
Speed, kts       50           26-45
Diameter, in/mm  25.6/650     21/533 
Length           30           24’  
Weight, lbs      10450        3800   
Warhead, lbs     990-1225     801                 

The Mk46 was designed for open ocean, deep water anti-submarine use and had problems in shallow water.  The Mk50 was developed as the replacement for the Mk46 but encountered problems.  The Mk54 was developed to rectify the problems identified in the Mk50 but does, itself, suffer from shortcomings against shallow water non-nuclear submarines.  A Mk54 Block Upgrade (BUG) program was initiated to address the problems but DOT&E still assessed the torpedo as not operationally effective in its intended role in a 2014 Annual Report and reiterated that assessment in the 2016 Annual Report despite additional upgrade efforts.

According to Polmar (1), US surface ships had anti-ship torpedo tubes until the late 1950’s.  During the 1960’s the Mk48 was intended to be fitted to surface ships for long range, wire guided ASW use but that never occurred.

Polmar also notes that a dedicated anti-surface torpedo was proposed by the Navy in the mid-1980’s (1).  The torpedo was envisioned as a low cost ($200K in then year dollars vs. $2.43M per Mk48 in FY88), no frills alternative to the Mk48.  The program was cancelled in the late 1980’s.

As a brief historical reminder of the use of anti-surface torpedoes on surface ships, here’s a list of the post-WWII ships that have had large, anti-surface-capable torpedo tubes installed.

  • Garcia/Brooke Class FFG 2x 21” fixed, stern tubes, Mk37 Torpedo
  • Sherman Class DD 4x 21” tubes
  • Mitscher Class DL 4x 21” tubes
  • Gearing Class DD 10x 21” tubes, twin trainable quintuple mounts, Mk15 Torpedo

That brings us to today.  The US Navy has no surface anti-ship torpedo capability and only a marginally effective submarine launched anti-ship torpedo, the Mk48.

The next question, and the main point of this post, is, does the US Navy need a surface anti-ship torpedo launch capability?

To better frame the question, consider that currently the Burke class DDG probably cannot sink a large ship such as a tanker or large cargo vessel.  If the US attempted a blockade and wanted to sink enemy merchant shipping, the Navy’s surface ships would be hard pressed to accomplish the task.  Small 5” guns are incapable of sinking a ship bigger than a patrol boat and Harpoon or Standard missiles in anti-ship mode will only damage superstructure, not sink a sizable ship.  Smaller ships such as the LCS which would be expected to perform most of the blockade and merchant shipping attacks have zero ability to sink a large ship.  A heavy weight anti-ship torpedo would go a long way toward providing a credible anti-ship capability.

Thus, the main argument for a surface anti-ship torpedo capability is lethality.  Compare the warhead weight of the Mk48 (650 lbs) versus the Kongsberg Naval Strike Missile (276 lbs) which is, apparently, going to be the Navy’s standard anti-ship weapon for smaller ships.  The difference is significant and, while simply comparing warhead weights is fraught with irrelevance, it nonetheless gives some idea of explosive power and concomitant lethality.  Clearly, a heavy torpedo packs a much more potent explosive punch.  Add to that the fact that torpedoes explode on or under the hull and let water in while missiles let air in, and the lethality of torpedoes is accentuated.  Smaller ships such as the LCS would gain a huge increase in lethality by mounting heavy anti-ship torpedoes.

The Mk48 warhead is lighter than the Long Range Anti-Ship Missile (LRASM) (1000 lbs) which may become a standard anti- ship missile for larger ships.  Again, though, the underwater location and nature of a torpedo explosion magnifies its explosive effectiveness.  Thus, even a Burke equipped with the LRASM could benefit from a heavy anti-ship torpedo.  We should also note that the vertical launch version of the LRASM may or may not ever happen and, if it does happen, takes away VLS cells from the ship’s main purpose which is anti-air warfare.

Another argument for torpedoes is their inherent survivability.  Currently, there are no effective active countermeasures to destroy attacking torpedoes and it is debatable how effective acoustic decoys, such as the US Nixie, will be given the Russian development of wake-homing torpedoes.  Unlike anti-ship missiles which are susceptible to electronic countermeasures (ECM), decoys, anti-air missiles, and close-in weapon systems and, therefore, need to be launched in large numbers to ensure sufficient hits, torpedoes can be used in relatively smaller numbers since they are largely immune to countermeasures.

On the other hand, one of the drawbacks to anti-ship torpedoes in the past has been the limited range, at least compared to anti-ship missiles.  The standard WWII Mk15 torpedo, for example, had a maximum range of around 8 miles.  That kind of range is unsuitable for today’s long range, over the horizon type of warfare where anti-ship strike ranges need to be 20-100+ miles.  However, modern torpedoes have greatly increased ranges that bring them in to the low end of anti-ship missile ranges.  For example, while the actual range of the Mk48 is unknown, the often cited range is around 20 miles.  The Mk48 upgrades have increased the fuel load and improved the propulsion so it is reasonable to assume that the range has significantly increased.  30 miles?  60 miles?  Who knows?  The point is that the torpedoes’ range is beginning to approach, for example, the Harpoon range of 60 miles. 

Certainly, modern torpedoes outrange the ship’s onboard sensors which makes them effective to the limit of the ship’s sensors.

Speed is another drawback.  Torpedoes are very slow compared to anti-ship missiles.  A fast torpedo has a speed of 50-60 kts versus even slow anti-ship missiles which have high subsonic speeds.  Thus, the travel time from the launching ship to the target allows for a great deal of movement by the target which complicates the targeting probability of success.  Further, the long travel time allows the enemy the opportunity to strike the launch platform before the torpedoes arrive.  Even if the torpedoes arrive and sink their targets, the launching ships may be destroyed in the interim!

Some of the arguments against torpedoes are valid due to the limitations of US torpedoes whose design and development has languished for decades compared to the advances in Russian torpedoes.  If the US were to develop a completely new anti-ship torpedo, many of the limitations would be eliminated or reduced.

Consider these improvements to torpedo performance.

Range.  Range could be 60-90 miles, matching the low to mid range for anti-ship missiles.  The old Russian Type 65-76 had a range of 60+ miles at 35 mph (2).  The German Navy’s current DM2A4 Seehecht (export designation "SeaHake mod 4") has a reported range of 87 miles (2) with GPS waypoint capability and carries a warhead of 572 lbs.

Speed.  Speed could be 60+ kts.  Russia’s VA-111 Shkval is the extreme example of high speed, reportedly capable of 200+ kts via supercavitation although the high speed comes at the cost of a reduced range of about 9 miles.  The US Mk48 is capable of around 60 kts.

Guidance.  Currently, the US has no wake homing torpedo but there is no technical reason why we could easily develop one.  Thus, a new torpedo could use multiple modes of guidance including passive and active acoustic, wake homing, and GPS/Inertial.  Wire guidance is probably not feasible for a surface ship due to the ship’s maneuvering and near surface turbulence but it’s worth looking at.


WWII Destroyer Torpedo Tubes - Time To Return To The Past?

A modern, new design, anti-ship torpedo could offer a lethality option for surface ships that is currently lacking.  Heavy torpedoes would not negatively impact VLS inventories although deck space and/or internal volume would have to be allocated.  Such a weapon would offer a relatively low cost increase in tactical options to the ship commander and ought to be part of every surface ship’s standard armament.



__________________________________

(1)“The Naval Institute Guide To The Ships And Aircraft Of The U.S. Fleet”, 16th ed., Norman Polmar, Naval Institute Press, 1997, p.465-469

(2)Submarine Matters blog, 1-July-2015,


24 comments:

  1. Yes!

    The ability to actually sink commercial ships is a long standing capability gap in the USN and USCG inventory.

    I would suggest that the Navy simplify a MK 48 for surface launch - whatever cost savings a new design would likely be consumed by overall program development costs, and maintaining as much parts commonality and volume production as possible with the Mk 48 would be a huge boon.

    GAB

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    1. There are two potential surface torpedo uses: anti-merchant and anti-warship. For anti-merchant, yes, a modified, simplified Mk48 would probably be quite adequate, as you suggest. For the anti-warship, we likely need a new design torpedo with greater speed, range, guidance, etc. Now, the question I have is whether the anti-warship role is a viable one. People with more knowledge than me would have to study the issue. I believe it could be viable with the right torpedo and tactics but my belief is not based on sufficient information.

      I did not mention it in the post but another possible use for an anti-warship surface torpedo would be as an unmanned recon asset. Fired down a bearing of interest or suspicion, a spread of torpedoes could scout and provide feedback and would have the advantage of a degree of stealth and complete survivability, as opposed to UAVs. The downside is that the sensors would have a very limited field of view so the extent of recon coverage might not be adequate. It's just a thought, that, again, someone with more knowledge would have to look at.

      Any thoughts on the tactical viability of an anti-surface torpedo?

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    2. Our VLASROC is need of an upgrade because it has a very short range (~15 mi) when compared to submarine torpedoes and ASM's. Adding an anti-ship capability to the ASROC is a dual use we should consider. First, dual-use VLASROC would not require weight and space modifications to the DDG's to accommodate the torpedoes. We would deploy the torpedoes from existing Mk 41 VLS cells. Second, adding a second offensive use to the VLASROC would enhance our flexibility to engage targets and conduct offensive operations. We are moving towards multipurpose weapons which us the most bang for each VLS cell. Dual-use ASROC could conduct both ASW and ASuW missions for the cost of 1 VLS cell. Third, a rocket deployed torpedo would be faster and potentially longer ranged than a submersed torpedo.

      KS

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    3. "Adding an anti-ship capability to the ASROC is a dual use we should consider."

      The idea is good but the execution would be challenging and is not possible, at the moment. Take a look at the specs in the post for the Mk46 length. The Mk46 is the torpedo that is in the VL ASROC. You'll note that the Mk46 is a lightweight torpedo and is not a ship-killer. The ship-killing, heavy torpedo is the Mk48 but look at the length. It's a bit over 29 ft. The longest Mk41 VLS cell is the strike version which is around 26 ft. Thus, the Mk48 won't fit in the VLS even without the rocket booster! That's why I say it can't be done, at the moment. We would have to design a brand new torpedo. Whether we could design a torpedo that is big enough to be a ship killer and still fit in a VLS with a rocket booster is highly questionable.

      So, while I agree with your concept, the reality is that it probably can't be done with current technology.

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  2. I like your idea CNOOPS that our surface ships have anti-surface torpedoes. Three 21 inch Mk 8 mod 4 torpedoes non-guided, conventional torpedoes with 805-pound warheads sunk the Belgrano in 1982... Re the MK48 torpedo- she's a fine weapon that works and I always questioned the Soviet/Russian claims on their miracle weapons...

    Here's something for you- mate up that MK46 torp with an ASROC type assist OTH/glide. Something super deadly.

    BTW HARPOONS can sink ships. I've participated and seen it done with telemetry weps. Depends on how the enemies ships are designed for damage control. Takes more that one for sure. So do 2000lb Skipper2's we don't have anymore.

    b2

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    1. "HARPOONS can sink ships."

      You're taking me a hair too literally. Of course Harpoon missiles can sink a ship under the right circumstances: small size ship, multiple missiles, a bit of good luck in where they hit, less effective damage control, etc.

      My statement is the recognition that Harpoon is not a guaranteed, one-hit sinking missile. Any decent sized ship like a large commercial cargo ship or tanker or large warship is probably immune from sinking due to Harpoons. Destroyer size ships could be sunk with enough hits. The point is that Harpoon is not an efficient ship sinking weapon and against the kinds of targets I cited, probably can't sink the ships at all barring very good luck and lots of missile hits.

      Consider the experience of our WWII destroyers on the picket lines fighting the kamikazes. Destroyers took multiple hits (some up to a dozen or so) and didn't sink. I very roughly liken a kamikaze to a Harpoon. The point is not whether a kamikaze is equivalent to a Harpoon, the point is that even small, destroyer size ships can take a lot of above the waterline damage without sinking and that's what a Harpoon does - it causes above the waterline damage. It's not a ship sinker except for smaller ships.

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    2. I agree, this ain't the battleship game- one shot one kill because you fired a single HARPOON..

      Shoot-wait-shoot.

      Stimulate them and when they are looking for you, HARM 'em and make 'em blind; then 'POON them from all aspects (pop and sea skim). Wait, rinse, repeat. Basic K.I.S.S.

      Too bad our helos aboard surface ships can't carry HARM and HARPOON. They should. They would have more credibility for me as ASUW/WAS replacements for the Viking/other jets if they did...

      b2

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  3. Do you necessarily have to sink a warship or a commercial vessel to render it mission ineffective? That is to say, still afloat, but either severely degraded operationally or else no longer useful at all for its intended purpose?

    Possibly you launch enough volume of ordnance against the ship so that when the last of its defensive ammunition runs out -- if it is so equipped -- the next missile you send does the job of at least gaining a mission kill.

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    1. Historically, we've never settled for mission kills if we had a choice. In fact, "mission kill" is a modern concept stemming from the recognized inability to kill ships combined with the recognized extreme vulnerability of ships. The same applies to merchant ships. No merchant ship has ever been "mission killed" and left afloat if the shooting ship/sub had a choice.

      The logic is simple, given time, every mission killed ship, warship or commercial, can be returned to the fight and have to be killed again. That's far too inefficient from the attacker's perspective to leave ships afloat. Also, it's very difficult for the attacker to determine the point at which mission kill has been achieved. The prudent attacker continues attacking until the target is going down.

      So, while a mission kill could fortuitously happen to a ship that you didn't have the capability to outright sink, no attacker is going to make that their ultimate goal. Sinking is the ultimate goal.

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    2. Scott,

      In a word yes, ships need to be sunk - mission kills are acceptable for a tactical commander, but the strategic level of war demands destruction.

      For a number of reasons, it is preferable to have a knockout weapon capable of sinking an enemy with at most 2-3 shots.

      I also note that:

      1) Sinking large warships is hard. Short of a magazine explosion (and often even in spite of one), many capitol ships have often required torpedoes to deliver the coups de grâce. The German cruiser Prinz Eugen survived two (2!) atomic bomb blast tests.

      2) Commercial hulls are monstrously large, By 2030 about 1/3 of container ships will be Post-PANAMAX size and capable of carrying 10-14,500 TEU, which is about the equivalent mass of 2-3 Nimitz class CVNs!

      GAB

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    3. "mission kills are acceptable for a tactical commander, but the strategic level of war demands destruction."

      Outstanding observation!

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    4. GAB: "In a word yes, ships need to be sunk - mission kills are acceptable for a tactical commander, but the strategic level of war demands destruction."

      An opinion has been pushed by some number of people for more than twenty years on naval blogs that a single hit on a modern warship by a modern anti-ship missile will do enough damage that even if the ship isn't sunk outright, then more likely than not, it will be out of action for some months until it can be repaired.

      GAB, what your response implies is that there are some adversaries we might face who wouldn't necessarily be inclined to tow their own ship away to the breakers if it had been severely damaged in a combat engagement. They'd tow it back to a safely defended port where it could be repaired, assuming there was enough time and enough money, and assuming the conflict or war hadn't yet ended after some number of months of combat action. How credible is this scenario in a future war between two capable adversaries?

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    5. Scott, the question wasn't directed at me and I don't presume to speak for GAB but here's my answer, for what it's worth.

      A peer war is going to be a long affair spanning many years. Neither side is likely to invade or even seriously attack the other's mainland. Therefore, neither side will be able to out and out defeat the other and the conflict will drag on around the periphery. In this scenario, both countries will have months and years to repair ships and return them to service.

      Consider some of the seriously damaged ships that we repaired during WWII which only spanned four years or so. Heck, we raised sunken ships from Pearl Harbor even though they were already nearly obsolete! Also, repair times during war will be much quicker than during peace. Consider the speed with which Yorktown was made operational just prior to Midway - weeks or months of repairs were condensed into 48 hours!

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    6. “An opinion has been pushed by some number of people for more than twenty years on naval blogs that a single hit on a modern warship by a modern anti-ship missile will do enough damage that even if the ship isn't sunk outright, then more likely than not, it will be out of action for some months until it can be repaired.”

      Hi Scott – I disagree with that opinion:
      1) We should avoid war, particularly protracted ones, but history argues that wars of decision between peer competitors often become nasty, protracted affairs. The antagonist(s) in every war expect a swift, and easy victory, otherwise they would not start a war; but human nature leaves ample room for miscalculation.

      2) Even extensive, expensive repairs become attractive if the repairs use different resources from new construction, and the ship can be returned to service faster than a replacement can be built.

      3) Ignore the ship and focus on the value of a trained crew – sinking the ship means likely killing many/most of the crew, a scarce, and hard to reconstitute resource. A mission kill, means that many crew will likely survive. The Germans had roughly 40 submarines left in May 1944, but the staggering losses of U-boote crews in the 12 preceding months (~75% KIA) ensured that many were not ordered to sea and the boats played little role in stopping the invasion of Normandy. War remains very much a human endeavor.

      Returning to the issue of commercial ships: imagine a scenario where a hijacked super tanker is driven at high speed towards a liquefied natural petroleum natural gas terminal (A-bomb level explosion), or the Panama Canal locks – how much would you pay for a weapon to stop the ship? If you have the time, there are other solutions (air strike, offensive ship boarding, etc.), but we likely will not know with any significant time to spare.

      I find the prospect of large torpedo tubes on surface ships and FAC to be viable because they can also be used to launch large drones or even lay mines.

      GAB

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  4. The new Italian PPA frigates in build include two 533 mm torpedo over the stern launchers. So the Italians think ship hitting torpedoes operationally viable. Their new Black Shark Advanced heavy weight torpedo, 6,300 x 533.4 mm, is equipped with multiple wake sensors, active and passive acoustic head and fitted with a fiber optic wire guidance, powered by Lithium-Polymer Battery.

    "Currently, there are no effective active countermeasures to destroy attacking torpedoes" 

    Navy in development of the Surface Ship Torpedo Defense (SSTD) System, Torpedo Warning System (TWS) and Countermeasure Anti-Torpedo (CAT) for the protection of the CVNs, there does not appear enough stern space to fit on the'dense' Burkes and their limited weight allowance.

    DOT&E FY2016 report
    A combined TWS and CAT contractor test in July 2016 demonstrated the Navy’s contractors are making progress toward developing an initial defensive capability to counter a salvo of threat torpedoes and improving the active source reliability. The test demonstrated that the TWS active and passive system, with a highly qualified sensor operator, is capable of detecting, tracking, and alerting on threat torpedoes; that operators can initiate a salvo of CATs to intercept the threat torpedoes; and that a salvo of CATs can intercept a salvo of threat torpedoes.

    Assessment • The combined TWS and CAT contractor testing in July 2016 demonstrated the Navy’s contractors are making progress toward developing an initial defensive capability to counter a salvo of threat torpedoes.

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  5. I feel like an issue is range. Assuming (for the sake of argument) that the torpedo travels at 60 knots and the ship travels at 30 knots, the effective range the ships that the torpedo is able to hit would be significantly less than its maximum range.

    This is because the ship can flee at a fairly decent percentage of the torpedo's top speed. A ship running away at 30 knots from a 600 knot missile doesn't make that much difference in range (it is only able to cover a few miles before the missile hits, a ship running away at 30 knots from a 60 knot torpedo makes a big difference, if the ship is 30 nm from the launching ship, it would be able to get an additional 30 nm away from the ship before the torpedo hits (ignoring the variable of acceleration) and if it is 35 nm away when the torpedo is launched, the ship would be able to get beyond the range of a torpedo with a theoretical maximum range of 60 nm. I think the relatively slow speed of the torpedo compared to the speed of the ships, would dramatically reduce torpedo's range.

    Additionally, sonar, presumably, would not work at a range of 60 nm, so the torpedo would either need to follow set waypoints to get to the estimated position of the ship, or receive location updates. Again, because of the speed difference, if the torpedo is following waypoints, the ship could be 30 nm away by the time the torpedo reaches the target ship's prior
    location, if it is relying on getting updates from the launching ship, that just increases the danger of the ship being mission killed by missiles before the torpedo arrives, which may cause the torp to miss.

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    1. Range/speed is an issue. Of course, you're assuming that the target is either moving away from the attacking ship the whole time or detects the torpedo very early and, again, moves away. One of the advantages of a torpedo is that it can't be detected on radar. What range can a torpedo be detected at AND A COURSE ESTABLISHED FOR IT so that the potential target knows it is, indeed, the target and should start to run, is unknown. Modern Russian torpedoes are incorporating stealth (acoustic quieting) into their designs to prevent detection until too late to run.

      Also, consider the effect of a target ship that is forced to stop whatever it's doing and run for an extended period. That has a tactical advantage for the attacking ship. The target ship becomes less of a threat and by making a high speed run becomes an acoustic beacon for any subs in the area. While running, the target ship is sonar-blind due to self-noise. So, all in all, even a torpedo that is outrun can have a positive impact on a battle.

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  6. I like the idea of an extended range torpedo. But, I think it carries a risk of hitting an unintended target, such as a neutral ship or worse, one of our own.

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    1. Wasnt that the reason for the lightweight torpedoes being ASu only, they were only operate below 30m or so. And when the Russian missile subs would surface before firing their cruise missiles, so were invulnerable to air dropped torpedoes, they came up with the harpoon ?

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    2. So does a missile but we intend to use them heavily!

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    3. Do missiles turn around and come back ?

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    4. Recent examples of missiles hitting unintended targets are the Taiwan navy which hit a fishing boat with a Hsiung Feng III missile in July of 2016 and the Hezbollah C-802 type missile that missed its Israeli warship target, the INS Hanit, and hit a Cambodian flagged merchant ship some 40 km further downrange.

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  7. " If the US attempted a blockade and wanted to sink enemy merchant shipping.."

    I just can't imagine the scenario of USAF/USN not be able to throttle Hormuz/Malacca/Suez chokes, which all Chinese maritime trade (other than trans-pacific) must pass, at will; they are not wide waters of the Battle of the Atlantic/Pacific.

    IMO, torpedoing PLAN warships in first/2nd island chain water is more relevant than torp'ing Chinese merchant ships elsewhere.

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  8. After you have fired all your SSM (normally 8), and you are gettig within gun range for continuing the fight, it would be very useful to have anti ship torpedos, even if they swim at 60 knots.

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