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.
Yes, seemingly innocuous things like this can burn you if you don't test them...
