New mk28 type torpedo for fleet boats

[keltos01]

mk27 depth 1.5 max dive angle 20 max turn angle 180
detonating impulse = -500
pistol magn detonation range = 1

jap acc depth 4.0 max dive angle 30 max turn angle 135
detonating impulse = 2000
pistol magn detonation range = 2 (meters..)

the rest seems the same, although the jap one has more chances of circle runner, 2 dud chances, 3 of premature explosion !

made you a custom torpedous.sim with
depth = 4
dive angle = 30
max angle=135
impulse = 2000
pistol det = 2

I can email it to u or post it tonight.

[M. Sarsfield]

Go ahead and post it and I'll download it on Friday, since I will be busy for the next few evenings. We can call it Mk. 28 Mod 1.

Btw, what is the acoustic depth? Is that the min. depth that the torpedo has to run to get a good signal?

I couldn't find much information on the acoustic performance characteristics to compare the Mk. 24/27 to the Mk. 28. I know the former were developed by Bell Telephone Laboratories and the latter by Westinghouse.

[AlmightyTallest]

keltos, your becoming the master of homing torpedoes, thanks for helping us with this project, it is appreciated. I found some info on the acoustic warhead of the Mk 27 here:

http://www.geocities.com/Pentagon/1592/ustorp4.htm

Two other passive homing torpedoes saw service in WW II. The Mk.27 torpedo was a submarine launched anti-escort weapon based on the Mk.24. The original Mk.27 Mod 0 was a minimally modified Mk.24 with wooden rails to fit 21" torpedo tubes, a floor switch (instead of a ceiling switch) so it would not attack the launching submarine, and various arming, warm-up and starting controls to suit a torpedo tube, swim-out launch mode. Eleven hundred Mk.27 Mod.0 torpedoes, known as CUTIE, were built by Western Electric and delivered between June 1944 and April 1945. Production on a subsequent order for 2300 torpedoes continued until the end of the war. One hundred and six were fired against enemy escorts. Thirty-three hits sank 24 ships and damaged nine others. Later versions of the Mk.27 were longer and heavier. Mod.3 which was slightly over ten feet long and faster; it had a 200 lb warhead and a gyro for straight runout before beginning to search for its quarry, Only six were completed before the project terminated at the end of the war. The post-war Mk.27 Mod.4 was different from the wartime versions, especially in that it could attack submerged submarines, and is discussed in the next part of this series. The Mk.28 was a 21" x 246", 20 knot, submarine launched anti-surface vessel torpedo with a 585 lb warhead. It was equipped with passive homing and gyroscopic control which competed for rudder control. About 1750 of these torpedoes were produced by Westinghouse and Western Electric. Only fourteen were fired with four hits during WW II, but the torpedo remained in service until 1960.

For the Mk 24 ASW torpedo, which the Mk 27 used a modified arrangement to attack surface ships instead of just submarines.

Target detection was accomplished by four hydrophones symmetrically arranged around the circumference of the torpedo mid-section in the left, right, up and down positions. Such an array is useful for target acquisition because the four hydrophones together cover essentially all directions from the torpedo and for homing because "body shadow", meaning that the hydrophone on the right side, for example, being in the acoustic shadow of the torpedo body could not hear a target on the left side, provides directionality. The basic idea is to compare the signals from the left and right hydrophones and move the rudder in such a way as to steer towards the stronger signal. In the BTL implementation of this scheme, the hydrophone signals were amplified, rectified and subtracted. This net signal was combined with the voltage from a potentiometer which was coupled to the rudder. The combined signal drove a DC amplifier which, in turn, controlled a differential relay that caused the rudder motor to move in the appropriate direction to reduce the input voltage (hydrophone derived voltage plus rudder potentiometer voltage) to zero. The vertical control circuit was identical except for including inputs from a hydrostat that measured depth and a pitch pendulum, which were also voltages derived from potentiometers. These signals caused the torpedo to operate at a fixed depth until a sufficiently strong acoustic signal was received. When such a signal was detected, the hydrostat/pendulum control was disabled and acoustic depth control prevailed. As a safety feature, acoustic depth control was disabled and hydrostat/pendulum control re-established if the torpedo rose above a ceiling set at about forty feet. This prevented the torpedo from attacking surface vessels including surfaced submarines. These control systems produced rudder angles that were proportional to the difference in strength between the signals from the right and left (or up and down) hydrophones. Such proportional control was distinctly different from the "bang-bang" (rudder hard left or hard right) controls that had been used ever since the Obry gyro was introduced, but detailed analysis and experimental work at HUSL showed that the "bang-bang" (no rudder position feedback) controls would perform equally well

The Mk 27 was a development of the airborne Mk 24, using guide rails to fit the torpedo tubes of the submarines. It was to be used passively, without use of any means of detection beyond passive sonar, against Japanese convoy escorts, from the rear tubes to put the risk of it striking the launching submarine. It would swim out of a flooded tube in order not to confuse it through the sound of compressed air swooshing around it. It was extremely successful. Used in the last month of 1944 and onwards, it destroyed 24 escorts and damaged nine, with 106 torpedos expended. This success convinced the USN of the usefullness of the new concept (which had already been tried, successfully, by the Germans, though Allied countermeasures made it more difficult in the Atlantic), and the discarded fleet submarine project of 1945 carried two external torpedo tubes specifically for the anti-escort torpedo.
The Mk 27 was used postwar until replaced by Mk 37.

http://www.bergall.org/cutie.html

Target detection was accomplished by four hydrophones symmetrically arranged around the circumference of the torpedo mid-section in the left, right, up and down positions. Such an array is useful for target acquisition because the four hydrophones together cover essentially all directions from the torpedo and for homing because "body shadow", meaning that the hydrophone on the right side, for example, being in the acoustic shadow of the torpedo body could not hear a target on the left side, provides directionality. The basic idea is to compare the signals from the left and right hydrophones and move the rudder in such a way as to steer towards the stronger signal. In the BTL implementation of this scheme, the hydrophone signals were amplified, rectified and subtracted. This net signal was combined with the voltage from a potentiometer which was coupled to the rudder. The combined signal drove a DC amplifier which, in turn, controlled a differential relay that caused the rudder motor to move in the appropriate direction to reduce the input voltage (hydrophone derived voltage plus rudder potentiometer voltage) to zero. The vertical control circuit was identical except for including inputs from a hydrostat that measured depth and a pitch pendulum, which were also voltages derived from potentiometers. These signals caused the torpedo to operate at a fixed depth until a sufficiently strong acoustic signal was received. When such a signal was detected, the hydrostat/pendulum control was disabled and acoustic depth control prevailed. As a safety feature, acoustic depth control was disabled and hydrostat/pendulum control re-established if the torpedo dove below a limit set to about 150 feet. These control systems produced rudder angles that were proportional to the difference in strength between the signals from the right and left (or up and down) hydrophones.
It was recounted by J.J. Ott, that it was fun (during operational checks) to make noises from several directions and watch the 'cutie' rudder and elevator wiggle around, trying to acquire the source. As they were an acoustic device, all effort must be made to insure that the submarine is quiet immediately after the launch or (being closer to the sub than the target) the torpedo would acquire the submarine. Since the Bergall failed to remove engine power before firing the first 'Cutie', it was the "loudest" target found when the 'Cutie' was released. The first 'Cutie' used fired by the Bergall against an enemy vessel, almost acquired the Bergall!
The enemy ship had to be "drawn" into close proximity to the submarine in order for the 'Cutie' to acquire the target. On the Bergall this was accomplished by rising to periscope depth, raising the periscope and "wiggling" the scope around, giving the enemy a better chance of seeing the periscope head. At this point the patrol craft would begin a run on the submarine. The Bergall would then drop to about 150 feet depth and wait as the enemy before firing.
The Mk.27 torpedo was based on the Mk.24. The original Mk.27 Mod 0 was a minimally modified Mk.24 with wooden rails to fit 21" torpedo tubes, and various arming, warm-up and starting controls to suit a torpedo tube, swim-out launch mode. Eleven hundred Mk.27 Mod.0 torpedoes, known as CUTIE, were built by Western Electric and delivered between June 1944 and April 1945

http://www2.nsysu.edu.tw/NOOM/weapon.htm

Guidance: uses passive accoustical guidance with pattern running

Seems EVERYTHING about U.S. Torpedoes is here:

https://www.keyportmuseum.cnrnw.navy.mil/html/part1.htm

In the departure from the practice of the time for the purpose of obtaining a quiet launching, Torpedo Mk 27 was started while still in the torpedo tube and swam out under its own power, requiring 8 to 10 seconds to clear the tube. The noisy ejection of the conventional torpedo was thus eliminated.
With successful application of the passive homing feature to "mission kill" or crippling weapons characterized by small warheads, application to large antisurface ship weapons logically followed, thus, the development of Torpedo Mk 28 by Westinghouse Electric Corp., Sharon, Pa., in the later World War II years. The Mk 28 was a full-size (21-inch diameter by 21-foot length), electrically-propelled submarine torpedo, with a speed of 20 knots and a range of approximately 4000 yards. This torpedo was also gyro-controlled on a preset course for the first 1000 yards, at which point the acoustic homing system was activated. The explosive charge was also increased to approximately 600 pounds.
About 14 Torpedoes Mk 28 were fired during World War II resulting in four hits. Since this torpedo was made available late in the war without adequate training in its tactical use, the number of hits was not as large as expected. The tendency to regard the acoustic homing torpedo as a device that could correct for any kind of fire control error was a factor in its low success rate. Nevertheless, the Mk 28 demonstrated that it was possible to successfully include acoustic homing in a full-size, submarine-launched torpedo.
ACTIVE ACOUSTIC HOMING TORPEDO DEVELOPMENT
The acoustic weapons developed and deployed during World War II were passive; they listened for a sound and then indiscriminately attacked the source. This technique, while far more effective than any preceding it, had limitations against a ship at slow speed, a submarine running deep, a submarine sitting on the bottom, or a ship employing countermeasures such as a stream of bubbles or a noisemaker.

Man, sorry for the huge post and many quotes, but this was everything I could find about the mk 27 and mk 28 before leaving for work.

[M. Sarsfield]

I remember reading that. I don't know if they programmed in a ceiling depth (min. operating depth) for the Mk. 24 or a floor depth (max. operating depth) for the Mk. 27 in the game.

[keltos01]

will take all this into account and try to mod a "real" mk28. as for the 3d... waiting till we can import the model using s3d.. k

[AlmightyTallest]

it's no problem keltos, we're not in any hurry, but what you created already is a great starting point for this torpedo.

[keltos01]

thanks I too would like a full size mk28, when I'm done I"ll include it in my torp mod, I hope to have it as another torp, not replacing one this time on ! Then I hope to be able to mod other torps...