...Those Marvelous Tin Fish: The Great Torpedo Scandal Avoided

Discussion in 'Alternate History Discussion: After 1900' started by DaveJ576, Jan 15, 2018.

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  1. DaveJ576 Well-Known Member

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    McPherson this is all good stuff! Thanks! The orientation of the firing pin was a key factor in why we got duds once the magnetic feature was disabled and the weapon was set to hit rather than run under a ship... ;) Yes, seemingly innocuous things like this can burn you if you don't test them...
     
  2. McPherson McPherson; a guy who needs a shave.

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    By the way...

    I had thought about that possibility before I posted the Mark 5 assembly/Mark 6 influence (got that one backwards ^^^^), but it seemed a ridiculous idea at the time.
     
  3. McPherson McPherson; a guy who needs a shave.

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    Physics.

    Quick layman's explanation. Take 30,000 tonnes of metal that is (250 m) long and (30 m) skinny and is unable to support its own weight if suspended on a fulcrum, teeter totter fashion in the middle as a bridge load (either live or dead weight, it does not matter). It floats in a condition of equilibrium pressure floatation. Now supply the fulcrum in the form of an underwater under the keel midbody explosion. Snap. Instant hog and sag actions.

    I like blowing the propulsion shaft seals myself. Guaranteed dead in all cases, even if the hulk floats because the hull is permanently pranged through the keel and longerons. And you can write off the propulsion train, too. That seems to be a "Russian" thing by the way.
     
    Last edited: Feb 15, 2018
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  4. phx1138 Bocagiste troll

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    I do understand the reasoning behind detonating beneath the keel.:rolleyes: As a matter of functional torpedoes, larger warhead is simpler & less prone to failure, which was the point.:rolleyes:
     
  5. McPherson McPherson; a guy who needs a shave.

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    Physical size limitations, ballasting and balance issues, and costs dictated the limits of the warhead volume available. That is the only conclusion I can offer, unless this is a case of the C-130^1 problem which constrains the possible systems that could be formulated.

    ^1 The barrel diameter of the aircraft limits what can be shoved into it. In the case of a torpedo tube it is the exact same problem.
     
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  6. phx1138 Bocagiste troll

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    I doubt USN would've gone up to 24", tho maybe, given the 22.5" Mk13. Either way, they did make the Mk14 longer than the Mk10, so how much longer would it need to be to increase the warhead size to, IDK, 1000pd?

    And if there's a real, practical size limit (I doubt it, until they exceed 24" {& I even less believe they'd go go a SU-standard 65cm:rolleyes:}, but...), why not look for better explosives? IDK if Torpex was practical yet, or if that would've been too advanced for the '28-'31 development period. Was it?

    If total length was an issue (again, I doubt it), as noted, delete the 2-speed feature, or use less fuel. Or improve the engine so it burns more efficiently. Or (fat chance) switch to enriched oxygen (not peroxide:eek:), akin the IJN fish. Again, is fuel chemistry too backward?

    And looking at the Mk13 spec, it wouldn't have been a terrible choice had it been as long as the Mk14. And the Mk15 was 42" longer, not an outrageous increase in a boat 308' long. So what about a 22.5x288" sub fish? And DD fish the same size? Given half the extra length is warhead, that puts the warhead at about 750pd. (Still too small, IMO.) If other systems are changed, can it reach 1000pd? Make it Torpex, for an equivalent of 1500pd TNT?
     
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  7. McPherson McPherson; a guy who needs a shave.

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    Hmm. I know that some US experimental work in the late 1930s with explosives was parallel to British work and that some of the explosives produced was about 1.5 the explosive force of TNT.

    Probably. Anyway RDX and HMX are available from `1933 on in the US tech tree if someone builds the production plants. That is RE value of 1.6 and 1.7 respectively.

    Not to throw a monkey wrench in the proceedings, but you know the Whitehead/Brotherhood engine system setup operated off cold gas pressure, right? It has always struck me as idiotic that no major world power has ever until recently thought of a low grade self combusting solid rocket candle to supply the gas for either a cold piston or turbine motor to drive a torpedo. I know US torpedoes use a liquid triune glycol/nitrate/butylene base fuel that can be ignited and self generate such a gas that drives a swash plate ICE piston engine. The slow burning solid fuel motor would be a more exotic, but doable attempt at a self oxidizing gas generator. It does have the ballast problem in that you cannot admit seawater into the fuel tank to maintain the correct density weight. The torpedo would rise unless there was a piston diaphragm that allows seawater displacement and pushes the candle back along the fuel case as the wicking burns the fuel off. It is doable. The chemistry is not that exotic.

    57.15 cm x 731.52 cm? Good grief, that is a 2000 kg torpedo. The Mark XIV was probably already a beast at 1500 kg to handle manually with block and tackle. There was little or no power assist on US boats.

    Look, I think the Mark 6 exploder was too large, complex, and mis-oriented in the warhead block. Make the detonator linear with a nose spinner clock safety with cam lugs instead of that impeller setup (^^^^). That probably gets you another 100 kg in the primary charge without fumbling with the rest of the fish because the cast warhead block can use and fill all of the void space of what looks like a cake pan fore-body more efficiently. I like a four or six whisker trigger switch inertia hammer initiated contact exploder with the apple core shaped initiator center buried dead center in a plasticized hexanite aluminum oxide warhead... just in case the torpedo decides to roll as well as yaw and pitch. This probably could be coupled with a top secret magnetic influence feature that the US Army was familiar with using for other applications by 1936. In other words, a US version of the Pi-2 (^^^^), only one that actually works.
     
    Last edited: Feb 15, 2018
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  8. NHBL Long Time Member, CMII

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    The problem with going to a larger diameter is that ALL infrastructure needs to be redone. It would become impossible for newer boats to use older torpedoes, an d every little detail would need to be redesigned--things like torpedo doors, for example. I don't know how much more complicated that would make things.
     
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  9. McPherson McPherson; a guy who needs a shave.

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    Torpedo tubes.

    And now some history.

    The international standard for torpedo tubes, (and oddly enough for railroad gauges) was established by the British. Initially this was the 45 cm (17.7 inch) torpedo because that was the standard Whitehead diameter of the 1880s and 1890s. This Whitehead gauge standard was British and American (Bliss Leavitt) but increased to 21 inches in the decade just before WW I because with the appearance of bigger battleships and more powerful guns, the need for a bigger long range fish to sink them was necessary and since most torpedo launchers in the era were destroyer, cruiser and battleship mounted, the swapping out of above deck launchers was less onerous than designing new submarine front ends. The swap-over was not complete until the end of the first world war. Even at that, many nations; Italy, UK, Germany, Russia, Japan used 17.7 barrel diameter torpedoes for the new air-dropped version of the weapon.

    And the new submarine standard for the torpedo became the 53.3 cm diameter bore tube. Even Japan adopted and did not change this submarine standard. The one oddball nation that refused the standard was France. France being France decided on a 55 cm standard. Note how long and relatively light weight for overall size the WW II French submarine fish are?

    Anyway for US purposes, the new torpedo tubes (longs from 1925 on) set the size limit for US fish at 21 inches (53.3 cm) in barrel diameter and 20 feet 6 inches (625 cm) in length. This standard is the smallest in volume of all the submarine torpedo tubes used by the great powers of the interwar era. Should it have been extended by two feet? It could be doable, but the problem is that now the existing sub's bow section has to be completely rebuilt and extended forward (See "Italian" GUPPY above.) It would be cheaper to design a new torpedo than change the gauge limits. There are economic boundaries and rather stringent ones to what the USN can afford in the 1930s. So... any PoD that is not ASB has to find the cheapest practical possible alternative to the RTL Goat Island fiascos.

    The best alternatives technically possible are electrics, some kind of (dangerous) NAVOL fish, or something off the wall like a solid propellant catalytic gas generator fueled torpedo. Not likely. So we are stuck with the Mark XIV propulsion setup. Whatever happens in this proposed timeline, the actual alcohol fuelled wet-heater technology and the volume limitations are going to restrict torpedo performance to a run time of 500 seconds at 24 m/s and give a maximum reach of 12,000 meters and an effective chase reach of about 4,000 meters before angle solutions become impossible. Warheads are limited to no more than 300 kg on a 1500 kg very heavy and dense fish. To tweak for effect, we need guidance alternatives to compass and pendulum and different fusing options. More bang through better chemistry (^^^^) is possible but some way to cure nose wander and to chase screws is my preferred solution. Someone (espionage) needs to look at a German G-7 and realize the whiskers could serve as passive fore-body fin (nose canards) stabilizers as well as contact actuator levers to set off an initiator charge. As for some kind of keel-breaker, has no one considered how a land-mine detector works?
     
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  10. jlckansas Well-Known Member

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    Is there any chance they might have a modular warhead system, much like you prop charges for artillery? You would have a destroyer have x amount of explosion parts, subs y amount and aircraft z amounts.
     
  11. McPherson McPherson; a guy who needs a shave.

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    Not likely. There was no working room for such a solution. Six in the tubes, six + four in the racks and up to 20 men bunked in the compartment. That makes for no space for dial a yield warheads or for packing a war-shot to target size with explosive fill tailored to the intended victim.

    My thing is missiles, but can you imagine trying to pull maintenance on a Mark XiV or doing battery checks on a Mark XVIII under weigh? Then pack a warhead cavity with blocks of Hexanite and attach said warhead to a power unit and propulsion body? The British tried that trick with some of their early ship borne surface to air missiles. It was a NIGHTMARE fraught with peril and dangerous to the firing unit. The British were crazy.

    I would rather have one size fits all low-maintenance weapons than a high maintenance lead acid battery powered torpedo with a warhead that had to be packed before ready as a warshot. Yikes, their situation with the Mark XIV with its leaky battery power cells, lube oil everywhere, flammable alcohol fuel and finicky trigger mechanisms that needed constant checking was horrible enough. Those men were brave.

    [​IMG]
     
    Last edited: Feb 16, 2018
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  12. phx1138 Bocagiste troll

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    That works for me, & addresses your correct complaint about excessive weight, too. (OTOH, a really big fish might encourage something like a crane in the torpedo rooms...:) Wouldn't need to be fancy, just a pull-down & pivot.)

    To be clear, tho, the notion of a really big fish is more noodling than serious. The Mark XIV got the spec it did for reasons I don't see are likely to change much.
    That is really interesting. It makes me think of high-test camp stove bricks (can't think of the brand name...:oops:). That would have to be safer than methanol, I would think.

    The balance issue shouldn't be too hard to solve. Especially if we conjecture a fuel mix where it's reactive with seawater. (Yes, that raises pre-lauch seal-tightness issues that may be a problem on their own...:eek:) Even if not...
     
  13. McPherson McPherson; a guy who needs a shave.

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    May compromise the weight forward more than design tolerances for a sub allow. There is a Spanish submarine class that an engineer recently screwed up when he put the decimal point in the wrong place for a critical displacement volume value. The sub is the S-80. The displacement error was about 80 tonnes.

    See above. (^^^^). Tolerances for a submarine are so tight that a few dozen tonnes error in mass can balloon the volume displacement size by 15% or more.

    Rocket candle.

    The thing that worries me besides the buoyancy issues is the bursting pressure the combustion would put on the torpedo casing or fuel container. Sure solid propellant can be packed dense and its burn geometry jigged to give a constant volume gas flow, but the secret about solid propellant burn is that the candle burns in a fashion so that the length of the candle is involved without a single constriction point in the burn developing. This it to prevent burnthrough, local gas pressure build up at the wrong spot and case melting from the blow torch effect. Needless to say, with the Goat Island crowd and their RTL reputation for quality control? Having them cast such a candle is not my first choice. Better off with a precursor OTTO fuel if it can be devised. It should be remarked that the problems I noted (see previous) are the problems encountered with the US 12.75" (32.4 cm) Mark 40 torpedo. (1955) These problems have apparently been solved in a later US torpedo (in current inventory).

    Those problems were solved post 1995.
     
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  14. Threadmarks: Post 7 - Frustration and Progress, 1930-1935

    DaveJ576 Well-Known Member

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    FRUSTRATION AND PROGRESS, 1930-1935

    By the spring of 1930 the prototype Mk 13 was ready for testing and 10 examples were provided to squadron VT-1B from the USS Lexington (CV-2). This first round was conducted on the test range in Narragansett Bay under controlled conditions. The Martin T4M-1 biplanes came in low and slow (30 feet and 80 mph) with camera’s clicking away and retrieval boats buzzing about. Of the ten initial drops, three broke apart upon entering the water, four failed to start, one ran on the surface, and the remaining two ran erratically. Seven of the ten were recoverable and were taken back to the shop for analysis. Assisted by engineers from Bliss and Alexandria, the Project G 6 technicians found and corrected several faults. Testing continued throughout 1930 and the operating parameters were eventually ramped up, including end to end testing on Torpedo Testing Range Atlantic (TTRA) in Maine and at sea out in the Atlantic Ocean. Results were mixed, with water entry characteristics causing a lot of concern. The Navy’s highest performing torpedo aircraft was brought in, the Great Lakes TG-2 and it was found that as the drop speeds and altitudes increased so did the erratic performance. The whole point of the project was to increase tactical operating parameters of the launching aircraft so the G 6 team took the Mk 13 back to the shop for some further development work and lab testing.

    Ralph Christie and his Project G 53 team was also experiencing frustrations with the magnetic exploder. Bench tests in the lab showed great promise, but during operational testing at sea the exploder was maddeningly inconsistent, sometimes tripping prematurely and sometimes not at all. The Ericsson became a familiar partner in the tests, towed about by fleet tugs to different locations, mostly off the New England coast. A deflated Christie, not willing to give up on his pet project, cajoled the Council into requesting an expanded test program with newer and larger ships. After quite a bit of debate the request was approved and in February 1932 he was granted the use of the brand new heavy cruiser USS Indianapolis (CA-35) and two destroyers. He loaded them up with torpedoes, exploders, and test equipment and they sailed for the equator off the Pacific coast of Chile. The testing there went much better and Christie gathered a large amount of data which he took back to the lab in Newport, where he continued to refine the design of the exploder.

    Fleet Problem IX and other tactical exercises amply demonstrated that although the torpedoes performed well, they were beginning to show their age and a desire for higher performance moved to the forefront of the Council’s priorities. Changing tactics and new ships showed that the old weapons were too slow, too short legged, and lacked explosive power. A series of discussions at Council meetings lead to a new design that was intended to serve as a weapon common to both submarines and surface ships. Refining the concept and taking into account the vastly different launching techniques and combat employment tactics the new weapon morphed into two closely related designs, designated the Mk 14 for submarine use and the Mk 15 for destroyer use. Using the standard 21” diameter, they shared the same engine, control mechanisms, and the same exploder design (intended to be the Mk 6 from the very beginning), but the Mk 15 was to have a larger warhead and a longer range, and thus was over two feet longer than the Mk 14. They were capable of speeds up to 46 knots with greatly increased range over their predecessors. For simplicity sake the same wet-heater engine used in the Mk 13 was adapted for the new weapons.

    The initial design prototype as developed by Newport proved to be a finely crafted piece of machinery and the technicians there were justifiably proud of it. Production planners at Bliss and Alexandria examined it from a mass production standpoint and were far less impressed. They recommended numerous changes and simplifications. The Newport contingent pushed back, insisting that the design stay as is. It took the intercession of the Chairman of the Torpedo Development Council, Assistant SecNav (and shipbuilding engineer) Ernest L. Jahncke, who overruled Newport after hearing both sides. Bliss engineers took the design and refined it for mass production. Their efforts also had the pleasant side effect of refining the Mk 13 design, as the three torpedoes shared the same propulsion system. Bliss also assisted in setting up the production line at Alexandria, with both facilities sharing common tooling.

    Testing of the refined prototypes kicked off in 1933, originally from barges right off NTS Newport. The 46-knot speed of the weapon thrilled the onlookers, but almost immediately problems arose. Net testing showed that the weapons were running about 10 feet deeper than set. Recovered weapons were checked thoroughly and found to be in perfect working order. Quite mystified, Newport ended the series and set a date to continue testing. Three weeks later, a new engineer from Bliss, recently graduated from MIT, was being hosted on an introductory tour of Newport and during the walkthrough of the testing lab he noticed that the depth setting test rig was not calibrated correctly. He meekly raised his hand and pointed out the error. At first incredulous, the Newport technicians later sheepishly admitted that the rig was indeed mis-calibrated, and they quickly applied the fix to the test weapons. New tests showed that the fix had helped, but the weapons were still running approximately 6 feet deeper than set. There were also a higher than anticipated rate of erratic runs, with some weapons nearly running a full circle.

    The final solution to these two problems eventually were found by conducting tests on sub-scale models at the Washington Navy Yard’s Experimental Model Basin. It was found that the much higher speed of the weapon created low pressure flow eddies in the area of the tapered aft section that lead to the rudders and propellers. The depth sensor was located in this area and the low-pressure eddies were making it think it was running too shallow, and thus a correction was sent to the depth planes that made the weapon run deeper. Launch tests here also showed that the gyro compartment access cover tended to leak under pressure or impact with the water and this threw the gyro into a tumble.

    During this time models of the Mk 13 were also tested, dropped into the basin from a special test rig, simulating the launch characteristics from an airplane. The results showed that the impact with the water was much more severe than thought, and damage to the models frequently occurred. The speed and impact angle also caused unfavorable post entry behavior, including broaching, hooking, and sinking. Various methods of controlling and mitigating these impact forces were tested, including parachutes. Tests on the Mk 13, both in scale-model and full-size form, continued to 1935. The solution ultimately proved to be drag rings installed to slow and stabilize the torpedo in the air, and shroud rings to protect the rudders and depth control surfaces. By the end of that year, the Mk 13 could be dropped up to the maximum speed of the T4M/TG aircraft (approx. 140 mph) and up to 500 feet altitude. At or below these levels the weapon achieved a successful run 90% of the time. These efforts were so successful that it was felt that even greater drop performance could be achieved with minimal development work, even to the point that the Council strongly recommended to BuAer that development work on a new torpedo plane be accelerated.

    Testing of the Mk 14 and 15 continued on the TTRA. The Mk 6 exploder was not yet ready so the weapons were fitted with a version that did not have the magnetic features installed. The underwater cliffs at Bald Porcupine Island immediately revealed a vexing problem: duds. Eight out of ten failed to detonate. Mystified, the Newport staff immediately set to checking the remaining weapons while one member of the FLO contingent on site (a trained Mk 5 deep sea diver) volunteered to dive down and retrieve as many of the unexploded weapons as he could find. Five of the weapons were in a condition to be retrieved so they were brought aboard a barge towed out from Bar Harbor and thoroughly checked.

    The root cause of the duds was revealed to be the design of the firing pin assembly itself. It was set vertically in the exploder, perpendicular to the axis of travel for the weapon. At 46 knots the weapon struck the cliff with a force of over 500 G’s. The firing pin, built solidly for this exact reason, had enough mass that when the weapon struck the cliff the G’s forced the pin against the guide studs intended to guide the pin into the fulminate exploder cap. The spring could not overcome the friction this caused and the pin did not move far enough to strike the fulminate cap, thus no explosion.

    Returning to the lab in Newport, a submarine qualified Chief Torpedoman from the FLO suggested an innovative and inexpensive testing technique. Weighted warheads (minus the explosive) were hoisted up on a crane cable and dropped onto steel plates from a height meant to simulate the impact force of hitting a ship. Sure enough the firing pin guide studs deformed and the pin failed to move 90% of the time. When the steel plates were angled to simulate a glancing hit, the exploder worked far more often. This was eventually found to be the result of reduced G forces from the glancing blow. This stunning revelation came as a shock to the Newport staff. Duds in earlier weapons like the Mk 8 and Mk 10 had been rare. It was found that the much higher speed of the Mk 14 and 15 magnified the G forces beyond what the legacy design of the firing pin could handle. The first solution offered was to lower the speed of the torpedo, but this eliminated one of the primary advantages of the new weapons. Ultimately the solution proved to be deceptively simple; manufacture the firing pin out of a lighter grade of aluminum so it had less mass. The new pins were installed and tested in live shots and the rate of detonations soared to nearly 100%.

    By late 1935 the Mk 14 and 15 were considered to be refined enough to allow their deployment to the fleet. Bliss and Alexandria immediately began to turn out production versions and the first weapons were loaded aboard submarines and destroyers by the end of the year.

    Another fortuitous event occurred in 1933 that would prove to have a profound impact on the Navy’s torpedo community and to the nation as a whole. Franklin Delano Roosevelt was elected in a land-slide victory as the 32nd President of the United States. The architect of the present torpedo infrastructure and the founder of the Torpedo Development Council was now the President and was in a position to clear any and all governmental and financial hurdles to success.

    Author’s note: As stated before, the lack of testing was a prime factor in the scandal. The reason most often given for no testing was the lack of funding. True, money would have to be spent and by 1932 this became problematic. But the reality was that it wouldn’t have been prohibitively expensive as long as the will was there. Innovative techniques like the crane drop would have been easy and cheap to conduct, but Newport would have none of it. Their confidence in themselves had become hubris, to the detriment of the entire Navy.
     
    Last edited: Feb 18, 2018
  15. McPherson McPherson; a guy who needs a shave.

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  16. phx1138 Bocagiste troll

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    The testing, & the solutions, are so close to OTL it infuriates me they weren't done.:mad:
     
  17. McPherson McPherson; a guy who needs a shave.

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    Dead in the tube is a problem we have not addressed.

     
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  18. phx1138 Bocagiste troll

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  19. McPherson McPherson; a guy who needs a shave.

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    How about a water ram? Post-war, but the tech is not that hard to develop pre-war. Your hot run is by hydraulic action expelled and you clear datum (noise) to try again later?
     
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  20. SsgtC Ready to Call it a Day

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    I somehow doubt this would be corrected. It's not a huge issue for one, it can be handled with a couple minutes work per fish by the torpedo room crew on board the boat. It wouldn't be seen as critical until the Navy is actually in a shooting war and the need for rapid loading becomes apparent. Also, and this is my own personal opinion, that would stray too far into using 20/20 hindsight to fix everything and give the US absolutely perfect fish
     
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