New mk28 type torpedo for fleet boats

[keltos01]

New mk28 type torpedo for fleet boats :
it does appear in career mode in 1944, not before. description still that of mk 27, specs of mk28 speed 19.6 range 4000m. enjoy !
where is the description of the different torpedoes? it inst in localization like the german part..

mk28 made by and tested by keltos

http://hosted.filefront.com/keltos01/

[DrBeast]

Originally Posted by keltos01

where is the description of the different torpedoes? it inst in localization like the german part..

Try LukeFF's advice here. Or, you might need to check in menu.txt under Data\Menu. Nice work btw!

[keltos01]

I tried.. couldn't find it help anyone ! I need to change the displayed specs of the torp loadout !!!!

[DrBeast]

Sorry mate, can't help you there. 1.5 changed the way it's displayed, and I don't have it.

[M. Sarsfield]

I finally got a chance to try out the Mk. 28 on a target. It was a lone, large freighter south of Tokyo Bay. I approached in foggy conditions at night and launched one Mk. 28 on the surface after cutting engines. Range to target was about 2600 yards, speed was estimated at 10 knots (turned out to be 9 kts) and my AoB estimate was only off by 8 degrees. Depth was set for 12 feet.

In my opinion the torpedo should have hit the target, but it didn't. It must have run far enough ahead of the target not to pick up the engine noises, but at a 1kt difference, it should have been a very close call. IMO the Mk. 27 warhead resembles a 90-yr-old man with hearing aids, but I don't know how sensitive the acoustic device was in real life.

[keltos01]

I myself usually get them from the rear with the "jap" accoustic torps, this way the torpedo can sniff its way to the target. will take a look to see the differences between the two, one might be more sensitive.

[AlmightyTallest]

In the one article I posted from the crew of a Tench class sub USS Torsk and USS Tennet firing these torpedoes, They mentioned the optimum firing angle is after the ship has just passed you, so that the torpedo has a better chance of following the sound contact of the ships.

I don't know how sensitive they really were, I can take a look and see what I find about the subject. Perhaps we could use the more sensitive german homing topedo variants if it's found the Mk 28 was more sensitive than the Mk 27?

Edit: found this info:

http://www.navweaps.com/Weapons/WTUS_PostWWII.htm

A passive homing torpedo developed from the Mark 18 which in turn was developed from captured German G7e torpedoes. The USN considered motor and gear noises to be the most troublesome problem with the homing torpedoes, unlike the Germans, who regarded propellor noises as the worst problem. The Mark 18 was not a quiet design, so the Mark 28 used only one propellor and eliminated the tail gearing. There were four hydrophones on the curved part of the nose. In production from 1944-52 and remained in service until 1960.

http://www.sennet.org/diary_all.html

TMCS(SS) Robert Marble 65-66, the "Doodle Bug" that George Bedell refers to is possibly the MK 27 acoustic (passive) homing torpedo. It was a 19" diameter, swimout torpedo that chased a target's propeller noises. It could also be the MK 28 torpedo, a smarter, heavier torpedo that reached the Pacific boats at the end of WWII. The MK 28 was 21" in diameter, impulse launched, and battery powered. By the time the MK 28 got to the fleet, there were few targets left. -- Jim Fields 46-49 gave me some more info -- The SENNET carried some MK 28 "stubby" torpedos which the crew called "Doodle Bugs." Two MK 28 "stubbys" could stowed on a rack that normally held one standard MK 14 torpedo. The MK 28 had to be fired at depths below 200' to keep it from picking up on SENNET's own propeller noises.

So it claimed as more sensitive compared to the Mk 27, it would pick up your own ships propellor noises more readily. From the diary they would fire these things and then sink down to at least 200 feet, or they could fire them from 200 feet on a bearing only launch and let the torpedo home in on the noise? Also when firing from stern tubes would have to be running silent engines off or turn engines off soon after firing before the weapon became active.

Perhaps we could use the smarter sensor modeled for the German Zaunköning or just use the entire torpedo model itself with adjusted stats for the Mk 28 or use the later updated variant Zaunköning mentioned in v1.5?

[M. Sarsfield]

I was thinking the same thing. I'll have to go back to some of those torpedo links that we posted a few weeks ago and see if there were any differences between 27 and 28 models.

I guess I'll have to adjust the firing angle to fire towards the stern of the ship next time. Still, I would think that a large freighter running at 10 kts would be making all sorts of racket, regardless of approach angle.

[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...