Friday, March 29, 2024

American Carrier Strike Groups: An Electronic Perspective (Part 3 of 5)

B. Kamalanath is a technical writer. He is also a research scholar, pursuing Ph.D in military technology

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FLIR imaging system. This is a high-power night-vision device used to detect surfaced submarines even in pitch darkness. The system senses the heat emitted by the submarines and is useful only when the enemy submarine has surfaced to get fresh air. In an FLIR, the surfaced submarine will stand out like a black spot on a plain, white paper. But, what happens when the enemy submarine is sailing underwater? There comes MAD.

Magnetic anomaly detector. A submarine is a colossal mass of metal sailing underwater. Magnetic field disturbances are created by the metallic mass’s interaction with the water’s different temperature gradients. MAD picks up these disturbances and detects submarine activity. Then, it transmits the location of the submarine to the destroyer through datalinks.

MADs are only a part of the detection system. Whereas, to pin the exact location of the submarine, helicopter’s dunking sonar and dispensable sonobuoys come into play.

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Dunking sonar. The helicopter hovers over the water surface and dunks sonar equipment. After dunking, resulting sonar readings are recorded and transmitted to the destroyer. This, the helicopter does at various locations in the sea. In the destroyer, readings from sonars are processed in underwater warfare command-and-control (C2) systems. This system comes directly under Aegis C2 system of the destroyer. Another method for detecting enemy submarine activity is through dispensable sonobuoys.

Dispensable sonobuoys. The helicopter strategically dispenses these sonobuoys at places where submarine activity is suspected or expected. These sonobuoys separate into two sections as sonar equipment and as a buoy. Sonars emit ultrasonic sound pulses as beeps and receive echoes like whales. Output of each beep is transmitted to the helicopter through buoys.

A92_Fig_17
Fig. 17: Under-sea warfare helicopter
A88_Fig_18
Fig. 18: A sailor loads dispensable sonobuoys in an under-sea helicopter (left); an under-sea warfare helicopter carrying a torpedo (right) and dispensable sonobuoys can be seen above it

A sonar computer in the helicopter collects information from various sonobuoys and transmits data to the underwater warfare C2 centre of destroyer. This system creates a picture of the underwater scenario by comparing the received echoes.

Each sonobuoy receives an echo. Depending upon their locations, the echo is received late or early. Through a process called triangulation, exact location of the submarine can be pinned down. Not just one helicopter, but helicopters from other destroyers are pressed into service, depending upon the combat situation. Because once a submarine’s presence is detected, the CSG puts in every helicopter to detect and neutralise that submarine. A fairly clear underwater picture can be evolved by these destroyers.

If the submarine is detected within the range of a helicopter, the under-sea warfare C2 system from the destroyer sends launch commands for a helicopter to launch a helicopter-launched torpedo.

The carrier, which is the prize target for a submarine, ironically, has neither strike capability against submarines nor strong organic submarine-detection capability. It has to defend against the submarine only when the submarine passes through the perimeter created by destroyers. The only defence it has against enemy submarines is through a torpedo decoy to seduce away the torpedoes launched by enemy submarines.

Torpedoes sense the noises chug chugs and murmurs generated by the target’s propellers and engine, respectively. There are certain torpedoes that track the wake created by the ships. The torpedo decoy is towed behind the carrier at a long distance. This decoy has a sonar that only looks for the sound of an approaching torpedo. When it detects an approaching torpedo, it produces a sound mimicking the sound produced by the carrier’s propellers and engine murmurs. The sound is so powerful and realistic that the torpedo is clearly attracted towards the decoy instead of the ship and thus gets spoofed. Employment of this decoy is a worst-case scenario in which associating ships have got sunk by enemy action.

Surface warfare
If a large flotilla of enemy surface ships is spotted faraway by E-2C airborne early warning (AEW) aircraft, F-18 combat aircraft carrying anti-ship missiles may be sent to finish these off. This is the long-range engagement but it is the destroyers that normally take care of medium-range engagements. Aegis C2 system keeps detecting and tracking surface targets. This is done by AN/SPS-67 surface-search radar, AN/SPY-1 radar and AN/SPG-9 radar.

For medium-range engagements, anti-ship missiles called Harpoons are used. These missiles are capable of reaching 100km. For short-range engagements, 12.6cm (5-inch) guns, or, simply, guns, are used to engage in a classical way.

In short-range engagements, the range, bearing and speed of the target are continuously updated and transferred to the gun’s fire control system (FCS). The FCS plots the course of the enemy surface vessel. Then, it calculates the elevation and orientation of the gun to be maintained and actuates the gun, accordingly. It even takes wave motion into account. If the destroyer is heaved one metre up, the shell may land far away from the intended target. So the FCS stabilises the gun accordingly and maintains it in the required orientation.

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