confidentialU.S.

Format: 16mm

Description: This "confidential" U.S. Navy training film gives an overview of the operation of the air-launched, acoustic homing torpedoes designed for anti-submarine and anti-ship use. The film discusses the difference between active and passive torpedoes, and goes on to describe the operation of the active type torpedoes. At 2:57 the passive Fido acoustic torpedo, also known as the Mine Mark 24, is shown. At 3:18 the Mark 27 Mod 0 acoustic torpedo is shown. USS Chivo (SS-341), a Balao-class submarine, is seen in the background. At 3:36 the Mark 28 Torpedo is seen, similar to the Mark 18. At 3:50 the Mark 34 Torpedo is shown. At 4:00 the Mark 27 Mod 4 is shown. At 4:15, passive torpedoes are shown. At 4;25 active torpedoes are shown including the Mark 32 Mod 1, the Mark 41 Mod 0, the Mark 43 Mod 0 and the Mark 41 Mod 1. The Mark 35 Mod 12 is also shown, but is not discussed in the film. At 5:09 an early Piasecki PV-3 / HRP helicopter is shown dropping an active torpedo. Animation then shows the "pinging" of the torpedo, as it turns and dives to search for a target (making a search circle). At 6;23 the pursuit circle is defined, and the "on/off steering" method that the torpedo uses to find its target are discussed. At 7:17, the final search circle is entered and the explosive charge is detonated. At 7:43 some of the non-optimal situations that a torpedo might encounter are shown, including shallow depth "angle blanking". At 8:54 the Mark 32 Mod 1 is shown, capable of being dropped from a blimp or surface ship. Its characteristics are then discussed. At 11:00, the Mark 41 Mod 0 is shown, an anti-submarine weapon only launched by aircraft. At 13:42 the Mark 43 Mod 0 is shown, again being dropped by a PV-3 helicopter. The torpedo's method of operation is then discussed. At 16:05, the Mark 43 Mod 1 is shown and its characteristics are discussed. At 19:48 the Mark 43, Mod 1, is shown being rigged for electrical firing, and its arming system shown. An acoustic torpedo is a torpedo that aims itself by listening for characteristic sounds of its target or by searching for it using sonar (acoustic homing). Acoustic torpedoes are usually designed for medium-range use, and often fired from a submarine. The first passive acoustic torpedoes were developed independently and nearly simultaneously by the Allies and the Germans during World War II. The Germans developed the G7e/T4 Falke, which was first deployed in March 1943. However, this early model was actually used in combat by only three German U-Boats. It was not until after the deployment of the T-4's successor, the G7es T-5 Zaunkönig torpedo in August 1943 that Germany began to use passive acoustic torpedoes in substantial numbers; the T-5 first saw widespread use in September 1943. This weapon was developed to attack escort vessels and merchant ships in convoys. Acoustic homing torpedoes are equipped with a pattern of acoustic transducers on the nose of the weapon. By a process of phase delaying the signals from these transducers a series of "acoustic beams" (i.e. a variation of acoustic signal sensitivity dependent on the incident angle of the noise energy). In early homing torpedoes the "beam patterns" were fixed whereas in more modern weapons the patterns were modifiable under on-board computer control. These sensor systems are capable of either detecting sound originating from the target itself i.e. engine and machinery noise, propellor cavitation, etc., known as passive sonar, or responding to noise energy reflections as a result of "illuminating" the target with sonar pulses, known as active sonar. Acoustic torpedoes can be compared to modern fire-and-forget guided missiles. What this means is the enemy (most likely a submarine) will be detected by sonar in any direction it goes. The torpedo will start with passive sonar, simply trying to detect the submarine. Once the torpedo's passive sonar has detected something, it will switch over to an active sonar and will begin to track the target. At this point, the submarine has probably started evasive maneuvers and may have even deployed a noisemaker. The torpedo's logic circuitry, if not fooled by the noise maker, will home in on the noise signature of the target submarine.

Complete Record:

Transcription

[Music] acoustic homing torpedoes may be divided into two general types active and passive passive torpedoes listen for cavitation noises generated by the propellers of target ships or submarines here as in the remainder of this film dimensions have been altered to simplify visual presentation when acoustic contact is made the torpedo will home on the target however noises from the propellers are limited in amplitude when a target moves slowly or when the target is at a relatively great depth or both under these conditions passive torpedoes are ineffective active torpedoes on the other hand do not depend upon noises coming from the target they periodically transmit an ultrasonic ping if a target is in the area echoes are produced the echoes in turn direct the torpedo in addition to the target however marine life and particles in the water close to the torpedo also produce echoes these echoes are complex reverberations which would misdirect the torpedo it means were not provided to prevent it to prevent misdirection the torpedo is provided with a time variation of gain circuit TVG which makes the torpedo insensitive to echoes received from very short distances thus the torpedo is not distracted and it homes on the target before considering several post-war active acoustic torpedoes let us look at some earlier passive ones this passive torpedo known as the mine marked 24 phyto is perhaps the best known of all acoustic weapons this device saw service both in the United States Navy and in the British Navy during World War two the torpedo marked 27 mod 0 is the pro submarine counterpart of the mine mark 24 it is a veteran of the Pacific fighting during world war 2 it is the only acoustic torpedo designed primarily as a defensive weapon for use against attacking enemy surface ships they took him mark 28 arrived toward the end of World War two it resembles closely the familiar electric mark 18 torpedo with the addition of an acoustic homing system the mark 34 torpedo is essentially a double sized higher speed mine mark 24 it arrived a little late for World War 2 the torpedo mark 27-month 4 is one of the latest of passive weapons it incorporates many of the features of earlier acoustic weapons with additional features of its own these weapons just shown are all passive acoustic torpedoes the weapons shown here are active acoustic torpedoes they are the mark 32 mod 1 the mark 41 mod 0 the mark 43 mod 0 and the mark 43 mod 1 the mark 35 is also an active acoustic torpedo however it will not be discussed in this film this film will consider the specific characteristics of each of these weapons they have a great many functions however which are similar to illustrate their general behavior let us first consider a hypothetical active acoustic torpedo which is representative of them all upon being launched from a firing vessel or from aircraft the torpedo enters the water and commences its initial diet then the torpedo stabilizes its descent and assumes a more nearly horizontal attitude after reaching a predetermined depth the torpedo starts pinging and listening for echoes in the following sequence the ultrasonic inaudible signal from the torpedo will be simulated by an audible tone in the absence of a target the torpedo makes a controlled helical downward search for a target the rate of descent the rate of turning and the transmitting and receiving pattern of the torpedo are such that a cylinder of ocean is searched this circle is called the search circle if contact is made with a target an echo will reach the torpedo the echo causes the torpedo to reverse direction and travel a long and art of another circle this is called the pursuit circle the torpedo continues in the pursuit circle until the echoes are no longer received after an additional short interval it reverses direction again and turns back into a second search circle contact is again made with the target this type of steering first in the arc of a search circles on or toward the target then in the arc of a pursuit circle off or away from the target is called on/off spearing thus the approach to the target is made along a series of artists when the weapon has closed to about 125 feet the torpedo is purposely deafened this deafening is called blanking the torpedo no longer responds to the echo and enters a final search circle upon contact with the target the explosive charge is detonated this illustrates the general behavior of many active acoustic torpedoes under optimum conditions however optimum conditions do not always exist for example suppose operations are conducted in relatively shallow water if a target is contacted and the torpedo dives of a steep angle Echo's will be received from the ocean floor so that the torpedo will not home on the sea bottom the acoustic range of the torpedo automatically shortens this type of blanking is known as angle blanking many of the active acoustic weapons incorporate angle blanking other compensations are necessary for other unfavorable conditions for example let us suppose a torpedo has made sure contact and is approaching a target once the torpedo has closed to a range of about 500 feet a range blanking system defens the torpedo too distracting echoes arriving from greater distances this completes our discussion of a generalized active acoustic weapon now let us consider some real active acoustic torpedoes first the torpedo marked 32 mod 1 the mark 32 mod 1 can be launched from blimps airplanes or surface ships at a depth of 18 feet propulsion starts and an initial dive at a 15 degree angle is rapidly achieved during its progress from 18 to 60 feet the torpedo can respond to echos in azimuth but not in depth at a depth of 60 feet the torpedo is headed downward at about two and three-quarter degrees here the mark 32 can respond in both azimuth and death in the absence of a target the helical search continued until the torpedo reaches a depth of 225 feet at this depth the torpedo continues to circle and search if no echoes are received this is not to be confused with the maximum depth to which the torpedo may go in pursuit of target when the battery is exhausted the torpedo sinks because of its negative buoyancy as it sinks through the 500 foot level the exploder is sterilized if acoustic contact is made shortly after water entry or at any time during search sitters the pursuit circle when the range has closed to 500 feet the torpedo will no longer respond to echoes coming from more remote points when the range has close to about 125 feet the torpedo is definite the mark 32 mod 1 now reenters the search circle and hits the target another type of active acoustic torpedo is the mark 41 mod 0 it is used only as an anti-submarine weapon the torpedo mark 41 mod 0 is launched only by aircraft propulsion starts when the torpedo reaches a depth of 20 feet it is not acoustically enabled at any depth for 20 seconds after launching it is war armed below 50 feet the torpedo marked 41 mod 0 searches in a controlled downward helix the dive angle during search is 3 degrees if no target is contacted during its down search the torpedo continues to search downward until it crushes in the search circle the torpedo mark 41 mod 0 turns at a 10 degree per second rate if the target is contacted the torpedo turns into the pursuit circle and pursues with a seven and a half degree per second off turn at a distance of 600 feet from the target the mark 41 mod zero swings one two four degrees in the pursuit circle this results in virtually straight course homing at this distance the torpedo is flanked to echos returning from greater distances at about eighty feet from the target another range blank occurs which defens the torpedo as a consequence of mark 41 mod 0 break turns to its 10 degree per second search circle and collision results if the mark 41 mod 0 has pursued the target and lost it and arranged greater than 600 feet it will again start searching after 8 seconds if target contact is lost within a range of 600 feet the torpedo levels off after 8 seconds and continues its search at a constant depth if an attack carries the torpedo above 50 feet the Explorer will be inactivated and the torpedo will start up down search let us consider next the torpedo mark 43 mod 0 in a great many respects this weapon can be considered a miniature mark 41 mod 0 torpedo transmission of pings is delayed a few seconds after launching because of vacuum tube filament warmup time at a depth of 30 feet the torpedo is war armed it is capable of responding to acoustic signals as soon as its vacuum tubes warm up as with the mark 41 mod 0 the mark 43 mod 0 makes a port helical downward search limited to a 3 degree down angle and a 10 degree per second turning rate if a target is not encountered the torpedo searches downward would depth preset in the torpedo shot here like the mark 32 it continues to circle and surf if a target is encountered the torpedo enters the pursuit pattern after the torpedo has closed to within 500 feet of the target a range blank prohibits response to echoes coming from greater distances as the torpedo approaches its target it is blanked for echoes returning from objects within about 90 feet the torpedo re-enters a search circle and detonation follows if the mark 43 mod zero has pursued a target and lost it without closing to 500 feet the torpedo will again start of downward search this time after an eight second delay if target contact is lost within a range of 500 feet the torpedo levels off and continue searching at this constant death if an attack carries the torpedo above 30 feet the exploder will be inactivated and the torpedo will reenter up down sir now let us consider the next active acoustic weapon on our list this is the torpedo mark 43 mod 1 as a helicopter weapon it makes a dive at about a 30-degree angle it becomes war armed at 50 feet it may be acoustically enabled at 50 feet or at a greater depth depending upon the initial setting the downward search spiral of the mark 43 mod 1 is typical of the other weapons just presented after an initial dive the mark 43 mod 1 can also be made to search upward by means of a shop adjustment in the downward search the mark 43 mod 1 has a variable depth search reversal floor now this means that the torpedo can be caused to spiral downward to any preset death for example 150 feet where it will reverse its vertical search direction and spiral upward the floor setting is a torpedo shop adjustment since search reversal can also take place at a ceiling the torpedo can be made to search both upward and downward within a prescribed strike when the target has been contacted and the range has close to 500 feet the torpedo mark 43 mod 1 will no longer respond to echoes coming from greater distances unless contact is lost for more than 6 seconds when the mark 43 mod 1 closes to a range of about 125 feet it is blanked to returning echo hence it reverts to its search turn and strikes the target if the mark 43 mod 1 should lose its target after pursuing to within 500 feet of the target it will continue pursuit for about two seconds and then level off for four and a half seconds before recommencing search in the direction of the last echo if it does not again pick up the target within the first six seconds after lost the mark forty three mod one has some features not to be found in other torpedoes of its general type for example the mark forty three mod one can be set to follow a gyroscope controlled course at a predetermined depth say 150 feet before it starts its characteristic search during the gyroscope controlled portion of the run the torpedo neither Kings nor listen it is acoustically enabled at the end of its gyroscope run after enabling the torpedo enters the typical search spiral another distinguishing feature of this torpedo is its pendulous transducer it is vertically stabilized so that for practical purposes it is independent of the pitch of the torpedo if the torpedo tilts up or down the transducer retains the same position which it had when the torpedo had zero pitch therefore the torpedo can be largely free of capture by reflected surface or bottom noises thus eliminating the need for pitch blanking the mark 43 mod 1 unlike the torpedoes previously discussed is fired electrically by means of a presetting cable and a control valve the control box includes circuits for battery heating gyroscope and vacuum tube warmer and for firing the torpedo this completes our general discussion of the active type torpedoes mark 43 mod 1 mark 43 mod 0 mark 41 mod 0 and mark 32 mod 1 [Music]

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