Every sonar engineer knows that signal clarity begins with the cable. But in naval defense, not all sonar systems are created equal. And neither are their cables.
At DeRegt, we’ve spent decades helping navies and defense engineers turn hydrodynamic challenges into predictable performance. In this article, we explore two main sonar architectures: Towed Array Sonar and Variable Depth Sonar. And how depth, buoyancy, and cable mechanics reshape what’s possible underwater. Because sometimes, being able to detect an enemy is just a matter of a few grams per meter, or the right cable design.
For naval sonar systems launched from submarines or surface vessels, the cable is a crucial component. These systems are collectively called Towed Sonars, as they are towed in the water. Each application requires a different cable design, determined by what must be detected, and at what depth. Below, we highlight two common naval sonar systems.
Towed Array Sonar System
A Towed Array Sonar System is towed behind a submarine or ship. Using a cable, the array’s sensors avoid the vessel’s self-noise, enabling more effective detection and tracking by the naval sonar system. Towed Array Sonar Systems are used exclusively in defense, typically to detect hostile submarines or surface ships.
The challenge in making cables for Towed Array Sonar is that they must remain at the correct depth during operation. Ideally, the cable is neutrally buoyant: neither sinking to the seabed nor rising to the surface. This balance is delicate, because copper conductors are eight times heavier than seawater, while polymer jackets compress under deep pressure, changing buoyancy with every meter.
Depending on submarine design, cables may be made slightly positive or negative in buoyancy to prevent entanglement with the propeller when the submarine stops.
Variable Depth Sonar: flexibility’s effect on cable design
Unlike Towed Array Sonar, Variable Depth Sonar relies on adjusting depth to achieve the required detection range. By varying depth, these systems can search in deeper or shallower waters as needed.
A Variable Depth Sonar typically uses two types of cables. The Heavy Tow Cable connects the towed body to the vessel. This armored cable must be as heavy as possible to reach operational depth. Often, hydrodynamic fairings are added to reduce drag, but they do not increase flexibility, and sometimes even reduce it.
The second cable type is the Light Tow Cable, a neutrally buoyant cable similar to that used in Towed Arrays, to keep the sensors at a constant depth behind the towed body.
Variable Depth Sonar vs Towed Array Sonar
These are two completely different naval sonar systems, designed for different missions. The choice between them depends entirely on operational requirements: depth, detection goals, and platform design. In our Complete Guide for Subsea Defense Projects, we cover requirements, design, testing, and validation for naval sonar systems in detail.
Download the Complete Guide
For all other cabling questions, you can always contact our experts. We’re ready to listen, advise, and co-create the right solution for your mission.
