We lift the lid on the latest covert vessels that are taking the art of sneaking to a whole new level.
Stealth relies on five core principles when it comes to military vessels: materials, coatings, geometry, noise and tactics. While the latter is situation dependent, the first four are physical qualities that can be modified to enhance stealth with advanced technologies.
Materials are based on composites such as fibreglass rather than hard metals and the incorporation of negativeindex metamaterials (NIMs). These latter artificial substances are designed to be all-but invisible to specific radar frequencies. Some vessels are also being built with demagnetization belts – a process that involves encircling a ship with superconducting ceramic cables.
Covering a vessel with radar-absorbent coatings such as iron ball paint – tiny spheres of carbonyl iron or ferrite – can also reduce a radar cross-section. Coatings are referred to as RAMs (radar-absorbent materials) and work by transforming radar waves into heat energy. This process works as the carbonyl iron coating has an alternating magnetic field, which when hit by radar waves begins to oscillate at a molecular level, trapping the incoming signal within the material and dissipating its energy as heat.
Noise in terms of maritime vessels can come courtesy of ship wake, heat generation and operating machinery. In fluid dynamics a wake is the area of disturbed liquid flow downstream of a ship. This wake can be detected by side-scanning synthetic aperture radars (SARs), which can then work out both the ship’s position and direction plus sonar installations.
To combat this, the latest stealth ships are generally outfitted with low-power diesel motors with specialised heat-dissipation systems to reduce their thermal signature. Active acoustic camouflage systems beneath the hull, meanwhile, can generate a constant series of small bubbles, effectively disrupting sonar images.
In this article We explores four examples of cutting-edge military vessels that have been designed with covertness at the top of the priority list, from out-and-out destroyers through to agile, wraith-like submarines.
What are masking systems?
Masking systems in marine vehicle applications work by reducing radiated noise generated by the vessel’s propulsion system and general movement. This is achieved by mounting machined perforations on the sides and propellers of the ship, through which compressed air is pumped at a high rate. This action creates a barrier of tiny air bubbles around the vessel and propellers that traps mechanical noise and disrupts sonar waves. The result of this is that enemy sonar installations, such as those found on military submarines, receive a heavily distorted image of the scanned area, with vessels commonly shrouded in a pattern akin to rain falling on the ocean surface.
The Infiltrator – Type 26 Global Combat Ship
The Crusader – USS San Antonio
So how is such a gargantuan vessel cloaked? Well, aside from the basics, it comes down to ship-wide attention to detail. Major antennas are mounted on platforms inside two advanced enclosed mast/sensor (AEM/S) systems rather than on yardarms. Deck edges are bounded by shaped bulwarks rather than lifeline stanchions; all exterior equipment is recessed or flush-mounted; bulky things like boat-handling cranes fold down when not in use; while the anchor and anchor hold are designed to minimise radar backscatter.
This strict adherence to stealth principles transforms the radar cross-section of what is essentially a small aircraft carrier into one under half its size. This allows it to sneakily approach target coastlines and launch air-cushioned landing crafts, amphibious assault vehicles, attack helicopters, military jeeps and even armoured personnel carriers onto land along with a maximum 699 soldiers.
The Annihilator – USS Zumwalt
Interestingly, the Zumwalt even extends its stealth mantra to its weapons, with every gun, missile and torpedo launched by integrated computer systems. As such, far from crew members having to man gun emplacements on deck or load missiles into launchers manually -generating more noise – the Zumwalt allows the sleek, minimalist deck to remain undisturbed, so an offensive can be launched without compromising its location.