The Coast Guard spends much more time thinking about how to keep ships from sinking, than it does about how to sink them. But because the Coast Guard is tasked with maritime security and because of the potential for terrorists using a ship as a means of attack, the question has become relevant. It becomes important when you consider, is the Coast Guard adequately armed for its missions. I’ve mentioned several times that I don’t believe the 57 mm gun is adequate to stop a medium to large ship being used as a weapon. I’ll try to explain why I have reached that conclusion and offer some examples.
Stopping–keeping it from reaching the target–rather than sinking a ship is probably more the relevant criteria, but generally ships don’t sink rapidly, particularly if you are trying to do it with a gun, so almost inevitably it is necessary to do enough damage to ultimately sink the ship if you are going to stop it in a timely fashion. Many of the ships that I will talk about continued to fight on for over an hour after the first hits were registered. Think of sinking a close surrogate for stopping a ship before it reaches its objective.
There are of course many examples of ships either surviving grievous attacks or alternately ships sink after a single hit. What it takes to sink a ship is highly variable and at best probabilistic. Its highly dependent upon ship design and preparation, but the most important variable seems to be size.
World War II experience
Over a long period, I’ve made an informal study of this subject. The primary source I used was the US Navy Report of War Damage series available here. The same index also includes reports of individual ship damage and reports of damage to British warships. I would also recommend the “Destroyer Report: Gunfire, Bomb and Kamikaze Damage, 17Oct41-15Aug45” which includes annotated damage control plates. The amount of damage these little ships took and in some cases survived is truly amazing.
The US Navy Report of War Damage series briefly outlines all incidents of damage to US Navy Battleships, Carriers, Cruisers, Destroyers, and Destroyer Escorts as they were known at the time the document was published and includes diagrams of the location of hits.
The forth and final volume includes a summary table of what caused the sinking of 92 ships ships lost during WWII (page 4). The ships sunk at Pearl Harbor but subsequently raised were considered “damaged” rather than “lost.” These 92 sinkings included 2 Battleships (BB), 4 Fleet carriers (CV), 1 Light Carrier (CVL), 6 Escort Carriers (CVE), 7 Heavy Cruisers (CA), 3 Light or Light Anti-Aircraft Crusiers (CL or CLAA), 60 Destroyers (DD), and 9 Destroyer Escorts (DE).
Causes for sinkings were listed as follows (three were listed as disappeared, but I have corrected the figures based on information that was not available at the time of the printing):
- 38 by torpedoes alone (41.3%)
- 16 by suicide planes (17.4%)
- 12 Bombs alone (13%)
- 11 by gunfire alone (12%)
- 6 by torpedoes and gunfire (6.5%)
- 5 by mines (5.4%)
- 4 by torpedoes and bombs (4.3%)
- 1 by bombs finished off by gunfire (1.1%)
As can be seen, torpedoes were involved in 48 of the 92 sinking (52%).
As the ships get larger it becomes harder to sink them by gunfire alone. If we consider only the 23 larger major warships (Battleships, Carriers, Cruisers) lost, torpedoes were involved in sinking 17 (74%) including 100% of the battleships and fleet carriers. It is not reflected in the table but torpedoes were also involved in the sinking of all six battleships at Pearl Harbor.
- 10 by torpedo alone (43.5%)
- 4 by torpedo and gunfire (17.4%)
- 3 by bombs and torpedoes (13%)
- 3 by suicide plane (13%)
- 2 by gunfire alone (8.7%)
- 1 by bombs alone (4.3%)
The two large ships sunk by gunfire alone both engaged heavy cruisers and/or battleships. USS Astoria (CA34) was sunk at the Battle of Savo Is., 8/9/42. She was hit at least 65 times by 8″ and 5″ projectiles. Five 5″ hits below water line. In spite of uncontrolled fires she did not sink until a magazine exploded nine hours after the action. The opposing force was 5 CA, 2 CL, 1 DD. USS Gambier Bay (CVE73), was sunk at the battle of Samar, 10/25/44. She was hit over 26 times. Two projectiles penetrated shell plating below waterline and detonated in forward engineroom and after engineroom, respectively. Hits included battleship caliber rounds, possibly including hits by Yamato’s 18.1″ guns. The opposing force was 4 BB, 6 CA, 2 CL, 11 DD. Notice in both cases, shells penetrated below the waterline. (As a point of reference typical shell weights are: 57 mm projectiles weigh about six pounds, a 76 mm 12-14#, a destroyer’s 5″ 55#, a light cruiser’s 6″ (152 mm) 110#, a heavy cruisers 8″ (205 mm) 260#, an smaller battleship’s 14″ 1485#, the Yamato’s 18.1″ 3219#)
Only one ship appears to have definitely been destroyed by gunfire from weapons 5″ or less, the Longshaw (DD559) hit six times while aground off Okinawa, resulting in a magazine explosion that blew off the bow. No ship larger than 3,000 tons full load was sunk by gunfire from weapons 5″ or smaller.
Consider that all these ships, including the aircraft carriers and battleships, were smaller than merchant ships that are now common. The largest was the carrier Lexington (CV2), 43,055 tons (fl), 888 ft (oa), 105’5″ beam, 33’4″ draft (270.66 x 32.12 x 10.15 m) (She was destroyed as a result of the accumulation of gasoline vapors after two torpedo and two bomb hits. The direct result of the hits were relatively minor, it was the gasoline vapor explosion that destroyed the ship). Lexington was a big ship, but no longer remarkable.
Warships might be thought more immune to damage. They usually have the advantage of better compartmentalization, a larger crew for firefighting, and sometimes armor. But they also had disadvantages. They frequently have, or had, large high pressure boilers that could explode. They carried lots of highly explosive projectiles, propellant charges, depth charges, torpedoes, aviation gasoline, etc that when exposed to damage could lead to secondary explosions. Modern merchant ships can be very hard to sink or even stop. A modern double hull tanker could be a particularly difficult.
SINK-EX RIMPAC 2000
To give some more recent data, using modern weapons, I’ll refer to RIMPAC 2000. One portion of the exercise included a missile firing exercise during which four decommissioned ships were sunk at the Pacific Missile Range Facility off the island of Kauai. The “Sink-Ex” operation involved firing of more than 100 missiles at the four target ships.
The four ships were
ex-USS Worden (CG-18), a 7,800 ton full load (fl) guided missile cruiser commissioned in 1963. The former USS Worden sustained a continuous attack from two ships and from F-14 Tomcat and F-18 Hornet fighters, finally sinking 34 hours after the exercises started.
ex-USS Buchanan (DDG-14), a 4,526 ton (fl) guided missile destroyer commissioned in 1962. Three Hellfire hits, three harpoon hits and a 2,400 pound laser-guided bomb hit were not enough to sink the ship, which required an additional 200 pounds of scuttling charges before sinking.
ex-USS Ramsey (FFG-2), a 3,426 ton guided missile frigate commissioned in 1967. Missile and aircraft firing exercises involving nine ships and three different types of aircraft were required to sink ex-USS Ramsey and ex-USS Gen. Hugh J. Gaffey. Ex-Ramsey sank only after taking several surface and airborne harpoons.
ex-USS Gen. Hugh J. Gaffey (AP-121), a 20,120 ton full load transport commissioned in 1944 that had once been the Coast Guard manned transport USS Admiral W. L. Capps (AP-121). Built to WWII merchant standards, Ex-Gaffey sunk nine hours after taking a total of 13 bombs.
While I can’t claim it is dead accurate I developed a rule of thumb when developing a rudimentary naval war game. It might serve as a useful metric until something better comes along. Actual results are probabilistically distributed but on average to have high confidence of sinking another ship you need to put one pound of bombs or shells on target for every ton of ship. To disable them, usually only takes about a tenth of that.
Torpedoes, considering only the warhead, are more effective. Weight of warhead exploding at the side of the ship, is about four times as effective as the same weight of ordnance (including bomb and shell casing as well as explosive) delivered above the waterline. Torpedoes exploded under the keel are about ten times as effective as the same weight delivered above the waterline.
Using this metric to sink a 2000 ton WWII destroyer took about 36 hits from a destroyer’s 5″ guns, about 18 hits from a light cruiser’s 6″ guns, 8 hits from a heavy cruisers 8″ guns, or only one hit from a battle ship’s 16″. A torpedo with a 500# warhead would usually sink a 2000 ton ship (unless it hit at the extreme ends of the ship). That appears pretty close to actual experience.
The only ships the Coast Guard currently has with any hope of stopping a medium to large ship are those armed with 76 and 57 mm guns. That in itself is not a good plan, because when the capability is needed, they are unlikely to be available. (I hope no one really expects to stop a determined attack by fast roping onto the deck.)
For the cutter faced with trying to stop a determined attack, I can only suggest that the CIWS may also be useful and recommend targeting the rudder and the engineroom near the waterline. Maybe hit the bow too in hopes of setting off any explosive that might be there.
In terms of making the 76 and 57 mm more effective. The Coast Guard might consider insuring the ships have available a very high velocity penetrating round, possibly using a discarding sabot as a means to get into a large diesel engine and destroy it. I know such a round is made for the 76mm, although it probably isn’t in the USN system. (I don’t know about the 57 mm.)
The real answer is to arm the more numerous and more readily available smaller cutters with a weapon that can reliably stop a ship of substantial size.
I think a modified Mk 46 could be an effective ship stopper, but if you absolutely, positively have to stop a ship immediately, nothing beats a heavy weight torpedo:
“On Monday, June 14, 1999, the Australian Collins class submarine HMAS Farncomb fired a Mark-48 war-shot torpedo at the 28-year-old former Destroyer Escort (actually a frigate) Torrens. The firing was part of the Collins class trials requirements and was designed to validate the submarine’s combat system. The submerged Farncomb fired the Mark-48 torpedo at the stationary hulk of the 2700-ton Destroyer Escort from over the horizon. The plume of water and fragments shot some 150 meters skyward as the blast of the torpedo cut the ship in two. The stern section sank rapidly after the torpedohit; the bow section remained afloat, but sank sometime later.
“The torpedo warhead contains explosive power equivalent to approximately 1200 pounds of TNT. This explosive power is maximized when the warhead detonates below the keel of the target ship, as opposed to striking it directly. When the detonation occurs below the keel, the resulting pressure wave of the explosion “lifts” the ship and can break its keel in the process. As the ship “settles” it is then seemingly hit by a second detonation as the explosion itself rips through the area of the blast. This combined effect often breaks smaller targets in half and can severely disable larger vessels.
“The Mark-48 torpedo used in this test is a variation of the MK-48 ADCAP (Advanced Capability) torpedo developed for the United States Navy.
“Photos and Mk-48 Torpedo information provided by Maritime Headquarters and DSTO Australia. Photos by PO Scott Connolly and AB Stuart Farrow. This PowerPoint presentation prepared by the Northern Connecticut Submarine Library and Museum.
“Source: US NAVY, site states that all content is in the public domain.”
(Added July 2012, US Navy photo)
(Added July 2012, US Navy photo )
The Royal Australian Navy’s (RAN) Collins Class submarine HMAS Farncomb has successfully sunk a target ship, the 12,106-tonne former USNS (United States Navy Ship) Kilauea in Hawaii.
Farncomb fired one Mark 48 Torpedo and achieved a hit just below the bridge of the ship as part of a sinking exercise, or “SINKEX,” at Exercise Rim of the Pacific (RIMPAC) 2012.
The former USNS Kilauea broke into two parts and sank about 40 minutes later.
If there is ever a question “Are cutters are large enough to launch a light weight torpedo?” this should dispel any doubts. A 12 meter (40 foot) USV with two torpedo tubes. http://www.navyrecognition.com/index.php/news/defence-news/2016/june-2016-navy-naval-forces-defense-industry-technology-maritime-security-global-news/4135-elbit-systems-seagull-usv-successfully-completes-torpedo-launch-trials.html
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There is an indication here that the Mk46 mod 5 light weight torpedo can be used against surface targets. http://www.navweaps.com/Weapons/WTUS_PostWWII.php
Its reported range (8,000 yards) and speed (45 knots) would be adequate for our needs.
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SINKEX with the former USS Thach as target. Four harpoons, 2000 lb bomb, 500 lb bomb, a bunch of Hellfires and it stayed afloat for 12 hours. http://www.popularmechanics.com/military/navy-ships/a21887/us-navy-allies-frigate-fire-exercise/
During 1995, the ex-USCGC Cherokee was expended as a target for the US Navy at Roosevelt Roads, PR. The WWII tug absorbed tremendous punishment, including a UGM-84 Sub-Harpoon from USS Key West (SSN-722), a RIM-7 Sea Sparrow from USS Arthur W. Radford (DD-968) and air-launched weapons.
Look at how many hits it took to sink a relatively small ship. http://navaltoday.com/2017/08/02/watch-the-brazilian-navy-sink-a-former-royal-navy-frigate-during-missile-exercises/?uid=171
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One crucial point – SINKEX hulks are all emptied of fuel and all weapons magazines are unloaded.
My primary point was that it is extremely difficult to reliably sink or even stop a ship with the guns the Coast Guard is equipped with. I have been primarily concerned about use of merchant ships as terrorist platforms. Their fuel is extremely hard to ignite by gun fire and generally they don’t carry a lot of explosives although they might. Even if they are carrying a substantial explosive charge we may not succeed in setting it off, before they reach their target, as evidenced by the success of the Saint Nazaire Raid. https://chuckhillscgblog.net/2011/02/03/a-tale-of-two-harbor-defense-organizations-part-one-2/ and of course all the ships in the original post were fueled and armed.
Did a bit of tabulating to determine how BBs and BCs were lost during WWII. Excluding those that were raised, the six major naval powers lost 22 to enemy action, five British, two US, ten Japanese, three German, one French, and one Italian.
Eleven were lost to aircraft only. Two to a combination of surface and air. Six to surface only. Three to submarines. Eight were lost in port.
Of the fourteen ships sunk while underway, only two were sunk by guns alone, Hood (British) and Kirishima (Japanese), each was hit by 15 or 16 inch projectiles.. Four were sunk by a combination of guns and torpedoes. Two by a combination of bombs and torpedoes. Five were sunk by torpedoes alone. One was sunk by guided missiles (Italian Battleship Roma).
How many were sunk by sabotage or acts of coersion?
The German battleship Tirpitz was very severely damaged by explosive laid on the harbor floor by British midget submarines (X-craft). It was essentially already useless when finally sunk by the RAF.
Two British battleships Queen Elizabeth and Valiant, were sunk but later raised in Alexandria harbor by Italian two man “pigs” a type of slow torpedo. https://en.wikipedia.org/wiki/Decima_Flottiglia_MAS
Another SINKEX, this time an FFG-7 class frigate. Took an awful lot of ordnance to put her down. https://www.navytimes.com/news/your-navy/2019/10/02/lcs-fires-ship-killing-missile-during-ex-frigate-fords-sinkex/?utm_medium=social&utm_campaign=Socialflow+NAV&utm_source=facebook.com&fbclid=IwAR2En6jSrzTHQliJD96mgsPenUbShofx19etU8e45jjSAMHDsP5_PIftTSw
This from Wikipedia, On July 14, 2016, the ex-USS Thach took over 12 hours to sink after being used in a live-fire, SINKEX during naval exercise RIMPAC 2016. During the exercise, the ship was directly or indirectly hit with the following ordnance: a Harpoon missile from a South Korean submarine, another Harpoon missile from the Australian frigate HMAS Ballarat, a Hellfire missile from an Australian MH-60R helicopter, another Harpoon missile and a Maverick missile from US maritime patrol aircraft, another Harpoon missile from the cruiser USS Princeton, additional Hellfire missiles from an US Navy MH-60S helicopter, a 900 kg (2,000 lb) Mark 84 bomb from a US Navy F/A-18 Hornet, a GBU-12 Paveway laser-guided 225 kg (500 lb) bomb from a US Air Force B-52 bomber, and a Mark 48 torpedo from an unnamed US Navy submarine. https://en.wikipedia.org/wiki/Oliver_Hazard_Perry-class_frigate
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The Drive provides us three reports on RIMPAC SINK-EXs.
Watch Three Anti-Ship Missiles Rip Through USS Durham During RIMPAC Sinking Exercise (2020) https://www.thedrive.com/the-war-zone/36077/watch-three-anti-ship-missiles-rip-through-uss-durham-during-rimpac-sinking-exercise Watch USS Racine Get Pummeled To Death During RIMPAC 2018 Sinking Exercise https://www.thedrive.com/the-war-zone/22184/watch-uss-recine-get-pummeled-to-death-during-rimpac-2018-sinking-exercise This Retired Perry Class Frigate Just Won’t Sink After Being Severely Pummeled During RIMPAC ‘16 https://www.thedrive.com/the-war-zone/4450/this-retired-perry-class-frigate-just-wont-sink-after-being-severely-pummeled-during-rimpac-16
A bit more information on what it took to sink the former USS Durham (LKA-114), length 575 ft 6 in (175.41 m), displacement: 9,937 tons (light) 18,322 tons (full load)
Weapons fired at her included four Harpoon ASCMs, an Exocet ASCM, two Hellfire, two different 5″ guns, and of course she was finished of with a Mk48 torpedo
Interestingly one of the missile shooters was a 80 meter 1625 ton Brunei offshore patrol vessel, which launched an Exocet.
It is not clear that all weapons hit, but film shows three ASCMs hitting very close to the same time and place on the target ship.
So much comes down to variables.
Clearly, construction matters. Just look at the Royal Navy’s losses in the Falklands in 1982 against a few Exocets.
Type of ordnance matters, as @Chuck described in his analysis of the Japanese attacks in the Philippines. Matching ordnance to the target clearly matters. Look at the 20mm to 30mm and even 57mms being used against large ships to minimal effect. (Of course the effect is different with relatively soft targets as US sailors from the USS Liberty would attest.
Damage Control is also a significant aspect, as is support from other friendly forces, both to provide aid as well as beating away the attackers.
So many variables… The only predictable, or prior-to-damage-controllable is construction and DC training. To a certain extent operating with friendly forces too, but that has it’s own variables.
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Found another similar analysis, this one from Soviet Union.
It has been my observation that in order to sink a ship, without a secondary explosion, unless the explosion is under water, it is probabilistic, but on average you need to put a pound of warhead on target for every ton of ship, e. g. 2000 ton ship you need about 2000 pounds of bombs, shells, or missile warheads.
Also explosives applied against the side of the ship by mine or torpedo are about 4 times as effective as the same weight applied above water so a torpedo with a 500 pound warhead is likely to sink a 2000 ton ship.
Warhead of a torpedo that explodes under the keel like the Mk48s, seems to be about ten times as effective as the same weight hitting above the water line. So a 750 pound warhead will likely sink a 75,000 ton ship.
Not to say there are not exceptions where ships survive or where they sink after being hit by far less.
Another SinkEx worth a look.
Looks like it took an awful lot of ordnance to sink the former USS Ingraham.
The report indicates.
at least three Harpoon missiles, delivered by P-8, sub, and FA-18s
two Naval Strike Missiles,
a Joint Standoff Missile,
laser guided weapons,
and a partridge in a pear tree.
This is another interesting source. http://www.navweaps.com/index_tech/tech-108.php
Reports on WWII loses of British destroyers. These were all small ships, none larger than 2,840 tons full load, and most much less. 153 lost, 140 due to enemy action. Less than 10%, only 14.5, attributed to gunfire (the half was also torpedoed). 50.5 attributed to torpedoes. 27 attributed to mines which cause similar damage effects. 48 were lost to bombs, which probably included some damage done by near misses. 12 were lost to accidents, and one was intentional blown-up destroying a dock in St. Nazaire, occupied France.
Of the 14.5 sunk by gunfire, two were sunk by shore batteries, two were sunk by battleships, 4.5 were sunk in engagements against cruisers, so only six were sunk by guns of 5″ or smaller. Of those six, three were sunk by two or more opposing destroyers. Only three were sunk by guns of 5″ or smaller, used by a single enemy warship: one by a Japanese destroyer with six 5″ guns, one by an Italian Corvette with three 100mm guns, and one Italian submarine with a single 100mm gun, that may have made a single very lucky hit, while engaging three British destroyers and a sloop, that may have resulted in a fire and magazine explosion.
The official investigation found that the damage, done by the Italian sub, that was also sunk in the engagement, was not the cause of the torpedo explosion, five and a half hours later, that led to the destruction of HMS Khartoum, so maybe there were only two sunk by a single adversary with guns no larger than 5″.
Nothing to add but want to thank you for the dedication you show to this blog. I’m only a part time lurker, but I really appreciate the effort you put in, and even entries like this one, which is over a decade old, are still very informative, well researched, and relevant. You even remember it and update it! The other one I remember if your 25mm vs 30mm gun article.
This is my most successful post.
Report on a RIMPAC 2000 Sink-Ex targeting the former USS Buchanan a 437 ft (133 m) 3,277 tons standard 4,526 tons full load guided missile destroyer, about the same size as the Bertholf class National Security Cutters or the Argus class OPCs.
“She remained afloat after being hit by three AGM-114 Hellfire air-to-surface missiles, three Harpoon anti-ship missiles, and a 2,400-pound (1,100 kg) laser-guided bomb in the Pacific Ocean off Hawaii on 13 June 2000. She finally was scuttled on 14 June 2000 by the detonation of 200 pounds (91 kg) of explosives that had been placed aboard her.”
RIMPAC 2022, Footage shows a mix of U.S., Canadian, Australian, and Malaysian forces hitting the former Oliver Hazard Perry-class frigate USS Rodney M. Davis (FFG-60) about 50 miles north of Kauai.
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US Navy, Royal Navy, US Air Force, and RAF beat up on a poor defenseless former USN FFG. Took an awful lot of ordnance. https://seapowermagazine.org/navys-vp-9-conducts-harpoon-shot-in-atlantic-thunder-2022/
why in WWII did some U-boats sink ships by exploding right next to the ship? suicide or was it a type of never giving up?
@Seth, I have never heard of a U-boat sinking a ship by blowing itself up. I have heard of U-boats being sunk when they torpedoed an ammunition laden vessel and the resulting explosion also sank the U-boat.
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