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- Navies around the world use sonobuoys to detect submarines, allowing sub hunters to quickly form their own underwater detection grids.
- With the rise of the Chinese Navy, and Russia’s investment in a fleet of imposing new submarines, the U.S. Navy wants to find and target those threatening subs.
- Last month, the service announced a $222.3 million deal to purchase up to 18,000 sonobuoys, which act like giant ears, listening for sonar returns triggered by underwater explosions.
Sub-hunting is back. The rise of the Chinese Navy, plus Russia’s introduction of a formidable new fleet of Yasen and Borei-class (pictured at top) submarines, have caused navies around the world—including the mighty U.S. Navy—to prioritize anti-submarine warfare, or ASW.
That much is evidenced by the service’s decision last month to purchase up to 18,000 AN/SSQ-125 sonobuoys as part of a $222.3 million contract with Lockheed Martin’s Rotary and Mission Systems division in Manassas, Virginia and ERAPSCO, a Columbia City, Indiana-based manufacturer of Navy sonobuoys and transducers. Sonobuoys are highly sensitive floating receivers that help pinpoint the locations of submarines.
You can get a rare glimpse of the life cycle of an AN/SSQ-101 sonobuoy in the video below:
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Anti-submarine warfare is one of the least well-known forms of combat, making the Navy’s investment particularly interesting. Sans sonobuoys, submarines rely on the opacity of the world’s oceans to evade detection, sneaking up on enemy ships before ambushing them with a brace of missiles or torpedoes. Modern submarines can attack their targets while fully submerged, making visual or radar detection impossible. ASW hunters must find them via sound, using sonar to detect lurking submarines.
One way of doing so is through the use of so-called “active sonar.” Active uses a burst of sound energy, transmitted through the water, to detect unseen objects. The thriller film The Hunt for Red October made this burst, often called a “ping,” famous when it debuted in 1990; It’s probably the first sound you imagine when you consider a submarine. As the burst travels through the water, it bounces off of underwater objects and returns in the direction from which it came, boomerang-style. A sub’s crew can then analyze the sonar return to determine if it’s coming from an enemy submarine. Counting the time it takes for bursts to return also allows the sub hunters to figure out the direction in which the enemy subs are traveling.
But another way to identify submarines is via aircraft, and it’s extremely effective. Airborne sub hunters are capable of searching vast distances and responding quickly to reports of enemy submarines. The problem for airplanes is that, unlike surface ships and other submarines, they are unable to utilize any sort of built-in sonar, since they travel over the water rather than through it.
That’s where sonobuoys come in. The floating sensors can listen to the ocean and relay that data to aircraft flying above. The long, thin buoy is one portion of the two-part Air Deployable Active Receiver (ADAR) system. A P-3 or P-8 anti-submarine aircraft, MH-60 Seahawk helicopter, or even a surface ship will drop AN/SSQ-101 and AN/SSQ-125 sonobuoys in an attempt to find an enemy sub.
Once released, the AN/SSQ-101 enters the water and deploys its payload. One of the first things it releases is a floating transmitter that bobs on the surface of the ocean, relaying whatever information it finds to nearby friendly ships and aircraft. Next, the sonobuoy unfolds a five-sided array of 40 underwater microphones (known as hydrophones), creating an underwater listening post.
The other half of the ADAR system is the AN/SSQ-110A sonobuoy. The AN/SSQ-110A is more exciting and consists of two explosive charges. Each time an explosive charge detonates, it sends a pulse of sound energy through the surrounding water. These pulses, especially those bouncing off of enemy submarines, are picked up by the listening AN/SSQ-101. ASW hunters would typically drop multiple AN/SSQ-101s, hopeful that their data could help triangulate an enemy sub’s position. The newer AN/SSQ-125, which replaces explosive charges with electronically generated sound, is replacing the -110A.
Newer ADAR systems forego explosive charges for an “electronically produced active acoustic wave” (read: ping), but the principle remains the same. Anti-submarine warfare is a cat-and-mouse game, and sometimes the cat needs to make some noise to find the mouse.
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