ASW on Small Craft

The 425 ton, 187 foot corvette HMS Gävle of the Swedish navy in Visby harbor. To be fitted with the Kongsberg Maritime ST2400 variable depth sonar.  Photo by Mr Bullitt

It seems warships are getting bigger all the time, but technology can sometimes make it possible to do more with less.

If we ever again face a submarine threat, there will never be enough destroyers and frigates to meet all the needs. The larger Coast Guard cutters will certainly be pressed into service, but there may also still be a need for protection of ports, coastal traffic, or choke points. These are prime submarine hunting areas. The Webber class might be adaptable to meet this need.

Certainly we would not I expect to see these on Cutters any time soon, but I wanted to point out the possibilities. Adding any ASW sensor, with the possible exception of the hull mounted sonar, would probably require that we land the 26 foot boat.

Below are three examples of ASW sensors applicable to small vessels. Most of the sensor technology comes from ASW helicopters, which like patrol boats, are limited as to space and weight. While helicopters can provide rapid response and movement, patrol boats have the advantage of persistence, including the ability to drift for days at a time.

We have already discussed how tubes for light weight torpedoes might be fitted to the Webber class for use against surface vessels. They could of course also be used against submarines.

Elbit Systems:

Elbit Systems’ Seagull unmanned surface vessel (shown firing a light weight torpedo) recently exhibited its anti-submarine detection capabilities using a dipping sonar rig and proprietary software.

The smallest is actually aboard a 39 foot unmanned boat, but it includes both a sensor in the form of a dipping sonar and an ASW torpedo weapon system.

Dipping sonars are a common feature on most ASW helicopters. The current US Navy system is the Airborne Low Frequency Dipping Sonar (ALFS) subsystem. ALFS began life as a Thales system.

Kongsberg Maritime ST2400 VDS variable depth:

Presentation of the Kongsberg Maritime ST2400 VDS variable depth sonar in the video above time 12:00 to 13:50

NavyRecognition reports this system is to be fitted on the Swedish Navy’s two remaining Göteborg class corvettes, which are already 24 to 27 years old. They are 20% larger than the Webber class, but they also are equipped with:

  • 1 × Bofors 57mm Mk2
  • 1 × Bofors 40mm/L70
  • 8 × RBS15 MkII AShM
  • 4 × 400 mm tubes for Type 43/45 torpedoes
  • 4 × ELMA Antisubmarine grenadethrowers
  • Mines & Depthcharges

Thales BlueWatch and CAPTAS-1

DefenseNews announced a new ASW sensor suite for ships as small as 300 tons that might include both a hull mounted sonar based on the same transducer currently used on the currently used dipping sonar, ALFS, and a towed sonar with a both an active transmitter element and a towed linear towed array receiver, the CAPTAS-1.

Thales Blue Watch Sonar System. (A hull mounted version of the AN/AQS-22.)

 

 

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