A sonobuoy (a

portmanteau A portmanteau word, or portmanteau (, ) is a blend of wordssonar and buoy) is a relatively small buoy – typically diameter and long – expendable sonar system that is dropped/ejected from

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engine ...

or ships conducting

anti-submarine warfare Anti-submarine warfare (ASW, or in older form A/S) 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 t ...

or underwater acoustic research.

Theory of operation

Sonobuoys are ejected from aircraft in canisters and deploy upon water impact. An inflatable surface float with a

radio transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...

remains on the surface for communication with the aircraft, while one or more

hydrophone A hydrophone ( grc, ὕδωρ + φωνή, , water + sound) is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates an electric potenti ...

sensors and stabilizing equipment descend below the surface to a selected depth that is variable, depending on environmental conditions and the search pattern. The buoy relays acoustic information from its hydrophone(s) via UHF/ VHF radio to operators on board the aircraft.

History

With the technological improvement of the submarine in modern warfare, the need for an effective tracking system was born. Sound Navigation And Ranging ( SONAR) was originally developed by the British—who called it

ASDIC Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances ( ranging), communicate with or detect objects on ...

—in the waning days of

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

. At the time the only way to detect submarines was by listening for them (passive sonar), or visually by chance when they were on the surface recharging their battery banks. Air patrols (the British mostly used small airships which had the advantage of long endurance) could spot surfaced submarines and occasionally, when conditions were right, even submerged ones as the diving depth of submarines of the era was so limited. If contact was made, they would follow the submarine while summoning surface ships by radio to attack it. Sonar saw extremely limited use and was mostly tested in the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

with few naval officers seeing any merit in the system. With the end of World War I came the end to serious development of sonar in the United States, a fact that was to be fatal in the early days of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. However, considerable development of ASDIC took place in the United Kingdom, including integration with a plotting table and weapon. While the United Kingdom pursued the development of sonar during the interwar period, the United States Coast and Geodetic Survey during the 1920s developed the

radio acoustic ranging Radio acoustic ranging, occasionally written as "radio-acoustic ranging" and sometimes abbreviated RAR, was a method for determining a ship's precise location at sea by detonating an explosive charge underwater near the ship, detecting the arriv ...

method of fixing the position of survey ships during

hydrographic survey Hydrographic survey is the science of measurement and description of features which affect maritime navigation, marine construction, dredging, offshore oil exploration/ offshore oil drilling and related activities. Strong emphasis is placed ...

operations by detonating a small explosive at the location of the ship, recording the time it took for the sound of the explosion to reach distant

s mounted at shore stations or aboard crewed station ships, and radioing the time of receipt of the sound to the ship, allowing the crew to make precise position fixes by using triangulation. In 1931, the Coast and Geodetic Survey proposed the replacement of crewed station ships with "radio-sonobuoys", and placed the new buoys in service beginning in July 1936. These buoys weighed , could be deployed or recovered by Coast and Geodetic Survey ships in five minutes, and were equipped with subsurface hydrophones, batteries, and radio transmitters that automatically sent a radio signal when their hydrophones detected the sound of a ranging explosion. These "radio-sonobuoys" were the ancestors of the sonobuoys that began to appear in the 1940s. The damage inflicted upon the Allies by German

U-boat U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare ro ...

s during World War II made the need for sonar a priority. With millions of tons of shipping being sunk in the Atlantic, there was a need to locate submarines so that they could be sunk or prevented from attacking. Sonar was installed on a number of ships along with radar and

high-frequency direction finding High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate over ...

("Huff-Duff") to detect surfaced submarines. While sonar was a primitive system, it was constantly improved. Modern anti-submarine warfare methods evolved from the techniques devised for the movement of convoys and battle groups through hostile waters during World War II. It was imperative that submarines be detected and neutralized long before the task group came within range of an attack. Aircraft-based submarine detection was the obvious solution. The maturity of radio communication and sonar technology made it possible to combine a sonar transducer, batteries, a radio transmitter and whip antenna, within a self-contained air-deployed floating (sono)buoy. Early sonobuoys had limited range, limited battery life and were overwhelmed by the noise of the ocean. They first appeared during World War II, in which they first were used in July 1942 by RAF Coastal Command under the code name 'High Tea', the first squadron to use them operationally being No. 210 Squadron RAF, operating Sunderlands. They were also limited by the use of human ears to discriminate man-made noises from the oceanic background. However, they demonstrated that the technology was viable. With the development of better hydrophones, the

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

and miniaturization, and the realization that very low frequency

sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' b ...

was important, more effective acoustic sensors followed. The sonobuoy went from being an imposing tall, diameter sensor to the compact suite of electronics it is today. The advancement in sonobuoy technology aided the development of aircraft such as the P-2 Neptune, S-2 Tracker,

S-3B Viking The Lockheed S-3 Viking is a four-crew, twin-engine turbofan-powered jet aircraft designed and produced by the American aerospace manufacturer Lockheed Corporation. Because of its characteristic sound, it was nicknamed the "War Hoover" after th ...

and P-3 Orion for anti-submarine warfare.

Operation

Sonobuoys are classified into three categories: active, passive and special purpose. *Active sonobuoys emit sound energy (pings) into the water and listen for the returning echo before transmitting information—usually range and bearing—via UHF/VHF radio to a receiving ship or aircraft. The original active sonobuoys pinged continuously after deployment for a predetermined period of time. Later, Command Activated Sonobuoy System (CASS) sonobuoys allowed the aircraft to trigger pings (or buoy scuttling) via a radio link. This evolved into DICASS (Directional CASS) in which the return echo contained bearing as well as range data. *Passive sonobuoys emit nothing into the water, but rather listen, waiting for sound waves (for instance, power plant, propeller or door-closing and other noises) from ships or submarines, or other acoustic signals of interest such as an aircraft's black box pinger, to reach the hydrophone. The sound is then transmitted via UHF/VHF radio to a receiving ship or aircraft. *Special purpose sonobuoys relay various types of oceanographic data to a ship, aircraft, or satellite. There are three types of special-purpose sonobuoys in use today. These sonobuoys are not designed for use in submarine detection or localization. **BT—The bathythermobuoy (BT) relay bathythermographic and/or salinity readings at various depths. Laying a pattern of sonobuoys is often preceded by laying one or more bathythermobouys to detect density/temperature strata which can act as sonar reflectors or, conversely, as waveguides. **SAR—The search and rescue (SAR) buoy is designed to operate as a floating

Radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the ...

beacon. As such, it is used to assist in marking the location of an aircraft crash site, a sunken ship, or survivors at sea. **ATAC/DLC—Air transportable communication (ATAC) and down-link communication (DLC) buoys, such as the UQC, or "gertrude", are intended for use as a means of communication between an aircraft and a submarine, or between a ship and a submarine. This information is analyzed by computers, acoustic operators and tactical coordinators to interpret the sonobuoy information. Active and/or passive sonobuoys may be laid in large fields or barriers for initial detection. Active buoys may then be used for precise location. Passive buoys may also be deployed on the surface in patterns to allow relatively precise location by triangulation. Multiple aircraft or ships monitor the pattern either passively listening or actively transmitting to drive the submarine into the sonar net. Sometimes the pattern takes the shape of a grid or other array formation and complex

beamforming Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles e ...

signal processing is used to transcend the capabilities of single, or limited numbers of, hydrophones.

References

External links

Sparton SonobuoysUltra Electronics - Maritime Systems Ultra Electronics - USSI Ultra Electronics - Sonar Systems

Ultra Electronics - Flightline Systems

Sonobuoy TechSystems
- a 1977 '' Flight International'' advertisement for the Mini-Jezebel sonobuoy
Harris Sonobuoy Launching Systems
{{hydroacoustics Anti-submarine warfare Sonar

Theory of operation

History

Operation

See also

References

External links