S
tealth relies on fi ve core principles when it comes to
military vessels: materials, coatings, geometry, noise
and tactics. While the latter is situation dependent,
the fi rst four are physical qualities that can be modifi ed to
enhance stealth with advanced technologies.
Materials are based on composites such as fi breglass
rather than hard metals and the incorporation of negative-
index metamaterials (NIMs). These latter artifi cial
substances are designed to be all-but inv isible to specifi c
radar frequencies. Some vessels are also being built with
demagnetisation 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 energ y. This process works as the
carbonyl iron coating has an alternating magnetic fi eld,
which when hit by radar waves begins to oscillate at a
molecular level, trapping the incoming signal within the
material and dissipating its energ y as heat.
Geometry is also crucial to remaining undetected. In
terms of radar, complex structures offer a far crisper,
easier-to-identify return image than those with a simple
geometr y. As such, modern stealth warships and
submersibles are designed with this in mind, often
installing protective domes over the mast and sensors,
called radomes. Similarly, today’s vessels have incredibly
clean and angled hulls w ith few doors and faceted hangars.
Noise in terms of maritime vessels can come courtesy of
ship wake, heat generation and operating machiner y. In
fl uid dynamics a wake is the area of disturbed liquid fl ow
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 outfi tted with low-power diesel motors with
specialised heat-dissipation systems to reduce their thermal
signature. Active acoustic camoufl age systems beneath the
hull, meanwhile, can generate a constant series of small
bubbles, effectively disrupting sonar images.
Here we explore four examples of cutting-edge military
vessels that have been designed with covertness at the top of
the priorit y list, from out-and-out destroyers through to
agile, wraith-like submarines.Stealth warships
We lift the lid on the
latest covert vessels that
are taking the art of
sneaking to a whole
new level
Radar
Ship positions are typically
determined through the
use of large-scale military
radar systems on land,
with data passing between
them and other local
vehicles and facilities. But
as stealth tech advances it
becomes far harder for
radars to spot enemies.USS San Antonio
Type:
Amphibious transport dock
Roles: Troop and vehicle
transport; multi-mission
littoral combat
Displacement: 24,900 tons
Length: 209m (684ft)
Beam: 32m (105ft)
Draft: 7m (23f t)
Propulsion: 4 x diesel engines
Power: 31,200kW (41,600hp)
Max speed: 41km/h (25mph)The statistics...
MILITARY