ISSN 2319-8885 Vol.03,Issue.39 November-2014, Pages:7896-7899 www.ijsetr.com Design and Analysis of an Under Water Weapon VINODH PERAM1, SRI. G. ADI NARAYANA2 1PG scholar, Dept of Mechanical Engineering, Nirma College of Engineering & Technology, Vijayawada, AP, India, E-mail: [email protected]. 2Associate Professor, Dept of Mechanical Engineering, Nirma College of Engineering & Technology, Vijayawada, AP, India, E-mail: [email protected]. Abstract: Under water vehicles viz. torpedoes, submarines etc are used in defense applications. These are designed for moderate to extreme depths of operation with minimum structural weight for increasing performance, speed and endurance. In general Homing head shell is the front part of the torpedo and its main purpose is target detection and tracking. The present thesis deals with the design and structural analysis of homing head shell of a torpedo. Basic analytical design for static loads was carried out using theory of shells methodology and British Standard BS: 5500. The finalized configuration was analyzed. The FEA stress and displacement results were compared with analytical solution. Due to the complex features of the design, stress concentrations were observed at certain places. A number of design iterations were made at these locations to bring the design to be within the acceptable stress limits. As the torpedo is carried either on a ship or submarine, the vibration loads due to these platforms has to be considered. Modal analysis was carried out to see whether the natural frequency is within the operating range of these platforms. While launching of these torpedoes, the torpedo experiences the water entry shock. The shell was analyzed for the shock load. The stresses developed due to the above shock load were found to be within the acceptable limit. Keywords: Torpedo Sections, Homing Torpedoes, Acquisition Areas, Shell93 Element Description, Various Array Configurations, Static Analysis, Buckling Analysis. I. INTRODUCTION defensive anti-submarine weapons by surface warship. The Torpedo is one of the oldest weapons in the Naval Although a number of elderly weapons still rely on Inventory, having been invented over 130 years ago, But at gyroscopic guidance. The majority of modern torpedoes rely the same time it remains one of the deadliest anti-ship and on Active or Passive acoustic homing or Wake homing. anti-submarine weapon, it is far more lethal to submarines Passive homing is used to detect submarine’s noise and surface ship than any other conventional weapon. A signatures. But this fails 2 when the submarine switches to torpedo is a self propelled underwater weapon that carries a silence mode. Thus it is very hard for passive seekers to high explosive charge to its target. A torpedo can do more detect them, and today active seekers offers the best way of damage than a projectile from the biggest guns on a attacking submerged submarines. Homing torpedoes are a battleship. There is more explosive in a torpedo warhead than relatively recent development they have been perfected since there is in any projectile. Torpedo warhead explodes under the end of World War II. With homing torpedoes, a destroyer water, and that increases its destructive effect. When can attack a submerged submarine, even when its exact projectile explodes, the surrounding air absorbs a part of its position and depth are unknown. The homing torpedo is force. But when the torpedo warhead explodes the water becoming increasingly important as a weapon with which transfers almost full force of the explosion to the hull of the one submerged submarine may attack another. target ship. Thus, even if a projectile could carry the same amount of explosive, the torpedo would do more damage. II. DIFFERENT TYPES OF TORPEDOES Torpedoes make it possible for small ships to carry heavy A. Torpedoes Mark14 Type and Mark 23 Type armament. But of course it cannot make ship the equal of a These torpedoes are only 20 1/2 feet long, to fit in large one in a combat. submarine tubes. The Mark 14 has two speeds. The low- power setting will give a range of 9,000 yards at A torpedo moves slowly compared to a projectile and its approximately 32 knots, and the high-power setting, a range effective range is much shorter. Heavy weight torpedoes are of 4,500 yards at 46 knots. Its war head contains about 700 mainly confined to submarines (with a few notable pounds of high explosive. There are no side-gear assemblies exceptions) and Light weight torpedoes are used both as in the main engine of this torpedo. The two speed settings are offensive weapons in anti- submarine warfare and as obtained by changing the number of nozzle jets in use (two Copyright @ 2014 IJSETR. All rights reserved. VINODH.PERAM, SRI.G.ADI NARAYANA for low speed, five for high) and by altering the size of the Provision for maximum possible Transducer restrictions in the air, fuel, and water delivery lines. The Elements Mark 14 torpedo has a governor whose function is to stop the Placement of Transmitting and Receiving SOBID torpedo, if the starting lever is tripped accidentally, before the elements engine develops excessive speed, and thereby to safeguard Housing the Echo sounder at the bottom of the personnel and to prevent serious damage to the torpedo. homing head Peripheral positioning of 4 Numbers proximity Fuse B. Torpedo Mark 18 Type 17 The Mark 18 is an electrically propelled torpedo designed Mounting arrangements for front-end electronics for use in submarines. It is single-speed, designed to run for and Signal processing Unit. 4,000 yards at an average speed of about 29 knots. The primary advantage of the Mark 18 is that it is wakeless. In IV. PROPOSED METHOD VARIOUS place of an air-flask section this torpedo has a battery CONFIGURATIONS compartment, which contains a lead-acid storage battery, a Taking into consideration of all the requirements of the hydrogen eliminator, and a ventilating system. The battery homing head, various configurations were tried out, without runs a 90-horsepower series electric motor (located in the compromising on the functional aspects. Four configurations afterbody) whose armature is connected by the main drive were worked out and they are as follows. shaft and gearing to two counter-rotating propellers. Planar Array Compressed air-required to close the starting switch, spin the Conformal array gyro, and operate the depth and steering engines-is stored at Circular array 3,000 psi in three small flasks in the afterbody. The gyro is of “run-down” type. After the initial spin the air is shut off and A. Planar Array the gyro is unlocked; the gyro wheel continues to spin of its This is the simplest configuration tried out. In this own momentum. The war head contains about 600 pounds of configuration the homing transducer elements are placed in a high explosive. planner array as shown in Fig.1. The planar array consists of 6 x 6 or 8 x 8 array. The transducer mounting plate in this C. Homing Torpedoes configuration is a flat plate with 36 or 64 circular holes, The torpedoes described above are designed to take up through which the stress rod of the transducer elements will the course set on their gyro mechanisms, and then run in a project into the interior. The SOBID elements are placed at straight line. Homing torpedoes can also follow a gyro the periphery of the array for object identification and course. In addition, a homing torpedo can search for a target, transmission .Two SOBID elements for object receiving and and, when it finds one, chase it until it secures a hit. Some the other two for transmission. The main disadvantage of this types can switch back and forth between gyro control, search model is as the number of transducer elements are less the pattern, and homing control, as appropriate. Several types of viewing area is less so an optimum search of the target is not homing torpedoes are now in the Fleet, and others are in possible. In order to overcome this look up area and the various stages of development. For security reasons, only a number of transducer elements are to be increased so that the short and very general discussion can be given here. At torpedo can view through better area. present, homing torpedoes are acoustic (operated by sound). In general, they are of two types-active and passive. The active type sends out short pulses of sound, and “listens” for echoes from the target. When an echo is detected, the torpedo steers itself toward the source of the echo. The passive type merely listens for target sounds (such as propeller and machinery noises), then steers itself toward the source of the sounds. III. EXISTING SYSTEM A. Acquisition Areas The primary task of torpedo sonar is to detect acoustically the target and thus compensate for the position errors of the torpedo relative to the target, which are inevitable and become greater with an increasing distance. If the acquisition area is too small, then the risk of passing the target without any target contact becomes high and the probability of success goes down. The various errors to be considered will become very large, due to the navigational errors of the firing submarines and due to flow in homogeneities. The homing head of the torpedo is required to be designed with the following requirements in view. Fig.1. Planar array. International Journal of Scientific Engineering and Technology Research Volume.03, IssueNo.39, November-2014, Pages: 7896-7899 Design and Analysis of an Under Water Weapon B. Conformal Array Young’s Modulus 71000 MPa In order to increase the viewing area the planner Loads: An external pressure of 72 bar is applied on the outer arrangement of the transducer elements in the above shell configuration have been modified to conformal arrangement.