Anechoic tiles are rubber or synthetic polymer tiles containing thousands of tiny voids, applied to the outer hulls of military ships and submarines, as well as anechoic chambers. Their function is twofold:
The technology of anechoic tiles was developed by the Kriegsmarine during the Second World War, codenamed Alberich after the invisible guardian dwarf of the Rhinegold treasure from Richard Wagner's Der Ring des Nibelungen music dramas. The coating consisted of sheets approximately 1 m (3 ft 3 in) square and 4 mm (0.16 in) thick, with rows of holes in two sizes, 4 mm (0.16 in) and 2 mm (0.079 in) in diameter. [1] [2] [3]
Manufactured by IG Farben as a specially formed synthetic rubber tile and made using a stabilized, non-polar, high molecular weight polyisobutylene homopolymer with low-temperature elasticity; the rubber material itself was known by its trademark Oppanol. [1] [2] [4]
The material was not homogeneous, but contained air cavities; these cavities resulted in a degraded reflection of ASDIC. [5] The coating reduced echoes by 15% in the 10 to 18 kHz range. [1] This frequency range matched the operating range of the early ASDIC active sonar used by the Allies. The ASDIC types 123, 123A, 144 and 145 all operated in the 14 to 22 kHz range. [6] [7] However, this degradation in echo reflection was not uniform at all diving depths due to the voids being compressed by the water pressure. [8] An additional benefit of the coating was it acted as a sound dampener, containing the U-boat's own engine noises. [1]
The coating had its first sea trials in 1940, on U-11, a Type IIB. [1] [5] U-67, a Type IX, was the first operational U-boat with this coating. [2] After its first war patrol, it put in at Wilhelmshaven probably sometime in April 1941 where it was given the coating. The coating covered the conning tower and sides of the U-boat, but not to the deck. By 15 May 1941, U-67 was in Kiel performing tests in the Baltic Sea. During July, the coating was removed from all parts of the boat except the conning tower and bow. Further experiments and sound trials were made in the Little Belt but they presumably proved unsatisfactory, as all the coating was subsequently removed. [9] Problems were encountered early-on, when it was found that the adhesive had insufficient strength to bond synthetic rubber with the pressure hull and casing. [3] [5] This resulted in the sheets loosening and creating turbulence in the water, making it easier for the submarine to be detected. [10] Furthermore, the coating was found to have considerably decreased the speed of the boat. [2] [11]
It was not until late 1944 that the problems with the adhesive were mostly resolved. The coating required a special adhesive and careful application; it took several thousand hours of glueing and riveting on the U-boat. [12] The first U-boat to test the new adhesive was U-480 a Type VIIC. [1] [5] With good results with the new adhesive, the Oberkommando der Marine intended that it would be widely used on the new Type XXI and Type XXII U-boats. However, the war ended before it could be put into large scale use. [5] Ultimately only one operational Type XXIII, U-4709, was coated with the anechoic tiles. [1] U-boats with the anechoic tiles coating include: U-11, U-480, U-485 U-486, U-1105, U-1106, U-1107, U-1304, U-1306, U-1308, U-4704, U-4708 and U-4709. [13] [14] [15] [16]
Anechoic coating based on research & technology supplied by Germany was also used by the Japanese I-400-class submarines, though completely different in composition from German rubber-based tiles like Alberich or Tarnmatte.
After the war the technology was not used again until the late 1960s when the Soviet Union began coating its submarines, starting with the Victor class, in rubber tiles. [17] These were initially prone to falling off, but as the technology matured it was apparent that the tiles were having a dramatic effect in reducing the submarines' acoustic signatures. Modern Russian tiles are about 100 mm thick, and apparently reduced the acoustic signature of Akula-class submarines by between 10 and 20 decibels, (i.e. 10% to 1% of its original strength).[ citation needed ]
Modern tiles[ when? ] may consist of several layers of material with voids of variable sizes, designed to mask and deflect specific sound frequency ranges at different depths. Different materials[ which? ] may be used by marine engineers to cover sections of the submarine where they are needed to absorb specific frequencies associated with machinery at that location inside the hull.[ citation needed ]
The Royal Navy started using anechoic tiles in 1980, when HMS Churchill was fitted with them during its second refit. [18]
The United States Navy also started using anechoic tiles in 1980, with USS Batfish. [19]
In recent years, nearly all modern military submarines are designed to use anechoic tiles.[ citation needed ]
Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation.
Sonar is a technique that uses sound propagation to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.
Flooring is the general term for a permanent covering of a floor, or for the work of installing such a floor covering. Floor covering is a term to generically describe any finish material applied over a floor structure to provide a walking surface. Both terms are used interchangeably but floor covering refers more to loose-laid materials.
The Hedgehog was a forward-throwing anti-submarine weapon that was used primarily during the Second World War. The device, which was developed by the Royal Navy, fired up to 24 spigot mortars ahead of a ship when attacking a U-boat. It was deployed on convoy escort warships such as destroyers and corvettes to supplement the depth charges.
A sonobuoy is a small expendable sonar buoy dropped from aircraft or ships for anti-submarine warfare or underwater acoustic research. Sonobuoys are typically around 13 cm (5 in) in diameter and 91 cm (3 ft) long. When floating on the water, sonobuoys have both a radio transmitter above the surface and hydrophone sensors underwater.
An anti-submarine weapon (ASW) is any one of a number of devices that are intended to act against a submarine and its crew, to destroy (sink) the vessel or reduce its capability as a weapon of war. In its simplest sense, an anti-submarine weapon is usually a projectile, missile or bomb that is optimized to destroy submarines.
Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typically carried out to protect friendly shipping and coastal facilities from submarine attacks and to overcome blockades.
In materials science, radiation-absorbent material (RAM) is a material which has been specially designed and shaped to absorb incident RF radiation, as effectively as possible, from as many incident directions as possible. The more effective the RAM, the lower the resulting level of reflected RF radiation. Many measurements in electromagnetic compatibility (EMC) and antenna radiation patterns require that spurious signals arising from the test setup, including reflections, are negligible to avoid the risk of causing measurement errors and ambiguities.
The Type 039A submarine is a class of diesel-electric submarine in China's People's Liberation Army Navy. It is China's first AIP powered submarine and presumed to be one of the quietest diesel-electric submarine classes in service. This class is the successor of the Type 039 submarine. The official Chinese designation is 039A as the ship is based on the 039 class, but as the 039A has very little resemblance to the 039 it is commonly referred to as the Type 041. The class is designed to replace the aging Type 033 and the older Type 035 submarines that previously formed the backbone of the conventional submarine force.
German submarine U-1105, a Type VII-C/41 U-boat of Nazi Germany's Kriegsmarine, was built at the Nordseewerke Shipyard, Emden, Germany, and commissioned on 3 June 1944. Oberleutnant zur See Hans-Joachim Schwarz was given command. He would command U-1105 for the remainder of the war.
The term acoustic signature is used to describe a combination of acoustic emissions of sound emitters, such as those of ships and submarines. In addition, aircraft, machinery, and living animals can be described as having their own characteristic acoustic signatures or sound attributes, which can be used to study their condition, behavior, and physical location.
German submarine U-11 was a Type IIB U-boat built before World War II for service in Nazi Germany's Kriegsmarine. She was commissioned on 21 September 1935, with Kapitänleutnant Hans-Rudolf Rösing in command. She served in several training flotillas in her 10-year career, but sank or damaged no ships.
Acoustic quieting is the process of making machinery quieter by damping vibrations to prevent them from reaching the observer. Machinery vibrates, causing sound waves in air, hydroacoustic waves in water, and mechanical stresses in solid matter. Quieting is achieved by absorbing the vibrational energy or minimizing the source of the vibration. It may also be redirected away from the observer.
German submarine U-486 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down at the Deutsche Werke in Kiel as yard number 321, launched on 12 February 1944 and commissioned on 22 March with Oberleutnant zur See Gerhard Meyer in command.
The S-99 experimental submarine was the only ship of the Project 617 class that the Soviet Union built during the early Cold War. She was the only Soviet submarine which used a German Walter turbine fueled by high-test peroxide (HTP). Entering service in 1956, the boat was assigned to a training unit of the Baltic Fleet. S-99 was badly damaged by a HTP explosion in 1959 and was not repaired. The submarine was decommissioned in 1964 and subsequently scrapped.
German submarine U-1308 was the last Type VIIC/41 submarine to be laid down, launched and commissioned by Nazi Germany's Kriegsmarine during World War II. The Oberkommando der Marine or OKM,, had decided near the end of World War II to put all of its resources into building newer types of Unterseeboot, such as the types XXI and XXIII. U-1308 was part of a batch of eight U-boats ordered on 1 August 1942 to be built at Flensburger Schiffbau-Gesellschaft, Flensburg. She was laid down on 16 February 1944 and launched on 22 November. The eight boats were commissioned over a 12-month period between February 1944 and 17 January 1945.
German submarine U-480 was an experimental Kriegsmarine Type VIIC U-boat of World War II.
German submarine U-202 was a Type VIIC U-boat of the Kriegsmarine during World War II. The submarine was laid down on 18 March 1940 by the Friedrich Krupp Germaniawerft yard at Kiel as yard number 631, launched on 10 February 1941, and commissioned on 22 March under the command of Kapitänleutnant Hans-Heinz Linder.
The Gruppenhorchgerät was a hydrophone array which was used on Nazi Germany's U-boats in World War II.