The US military is building its entire force structure
around the concept of information which includes data collection, surveillance,
networks, etc. In other words, the
military is assuming – or, at least, working towards the goal of – perfect
battlefield awareness, believing that will make up for vast, self-inflicted shortcomings
in firepower. Setting the lunacy of that
assumption aside, the implication is that the US believes that all will be
known and seen on the battlefield. Accepting
that premise for the sake of analysis and discussion, we must also assume that
the Chinese will have the same degree of total vision and situational
awareness.
What, then, does that suggest about the survivability of
naval forces? It’s obvious, isn’t
it? Only the most stealthy platforms
will be able to evade detection for any useful time period. Unfortunately, none of our current
naval surface ships come remotely close to that level of stealth. In order for a ship to survive on the future naval
battlefield, it will need to have maximum stealth across the entire
electromagnetic spectrum and beyond.
With that in mind, why don’t we have a bit of fun and see if we can come
up with a conceptual design for a future ship – it doesn’t matter what type – that
is the stealthiest possible given our current level of technology?
Before we go any further, we need to briefly review what
stealth is.
While most people associate the term ‘stealth’ with radar
signature, the term actually encompasses much more. The definition of stealth is the ability to
evade detection. That evasion can
include measures such as reduced radar signature, reduced infrared signature,
reduced acoustic signature, altered visible signature (camouflage), the use of
multi-spectral obscurants, decoys (chaff, flares, emitters), electronic
warfare, tactics (avenues of approach, use of weather), etc. It should be noted that some of these do not
have to be part of the ‘hiding’ platform’s capabilities but can be provided by
other platforms in support of the ‘hider’.
For example, an F-18G Growler electronic warfare aircraft can provide
stealth cover for other ships or aircraft by using its EW/jamming capabilities
to reduce the likelihood of detection of the ‘hiding’ platforms.
Of course, having organic stealth measures helps, too!
So, understanding everything that goes into making a
platform – a ship, in this case – stealthy, let’s see if we can conceptually design
the ultimate stealth surface ship, just for fun. What would it look like? What characteristics would it have? What unique aspects would be incorporated
into this design that are not currently common?
For this exercise, we’ll only consider the organic stealth
measures and ignore the off-board measures from other platforms. Thus, we’ll concern ourselves with size, radar
signature, acoustic signature, infrared signature, optical visibility,
electromagnetic emissions, obscurants, decoys, electronic warfare, and wake
suppression. Some of these factors are
pretty obvious so, for the sake of brevity, I won’t belabor them.
Size – The most basic – and almost universally
ignored – aspect of ship stealth is size.
Simple size. All else being
equal, a smaller ship is harder to detect than a larger ship. A smaller ship naturally has smaller
signatures across the electromagnetic spectrum.
This is a fundamental truth that the Navy has totally ignored as it continues
to produce ever larger ships. The WWII
Fletcher class destroyer was 376 ft long versus a Flt IIa Burke class destroyer
which is 509 ft long. A WWII Atlanta
class cruiser was 541 ft long versus a Zumwalt class cruiser (the Navy
misleadingly calls it a ‘destroyer’) which is 610 ft long. The Brooke class FFG was 414 ft long which
was followed by the larger Perry class FFG which was 453 ft long which was
followed by the still larger Constellation class FFG which is 496 ft long.
One of the largest drivers of ship size is the Navy’s
obsession with helicopters. The Navy
believes that every ship must have a helicopter with its attendant flight deck,
hangar, magazines, maintenance shops, additional crew, etc. which make up a
third of a ship’s length and superstructure.
No ship should have a helicopter unless it is absolutely required for
the execution of its primary mission.
For example, an AAW escort has no need for a helo which instantly reduces
the ship’s size by a third – a nice chunk of ‘instant stealth’!
Included in size considerations is the superstructure. Superstructures have grown enormously since
the ships of WWII (see, “Ship Superstructures”). Every square foot of superstructure area and every
cubic foot of superstructure volume increases the ship’s various signatures.
The obvious conclusion is that our stealthy ship must have
the smallest hull size and smallest superstructure possible, consistent with
its mission requirements (CONOPS).
Radar Signature – This is the commonly understood
measure of stealth and needs little further discussion other than to note that
a truly minimized radar signature requires that there be no protruding objects
such as railings, sensor domes, antennae, line handling equipment, platforms
and supports, cabling, electrical junction boxes, firefighting plumbing, etc.,
all of which our current ships have in abundance. Our conceptual starting point, in this
respect, is the Swedish Visby which is nearly as free of protruding items as
possible (see, “Ship Stealth and Visby”).
 |
| Visby - Note the relative lack of protruding objects |
Acoustic Signature – Arguably, the most lethal threat
to ships is the submarine and the main means of detection that a submarine uses
is acoustic sensors. Our ship must be as
quiet as possible. Every known acoustic
suppression method must be used, including isolation and rafting of internal
machinery, selection of inherently quiet machinery, Prairie-Masker, vibration
dampening, cavitation suppression, etc. Silence
must take priority over speed. The
powertrain and propulsion must be the quietest possible. We cannot use massive noise beacons like
water jets. I do not have detailed
acoustic data about propulsion pods but I suspect they may be a good choice
since they eliminate the use of long, large, noisy propeller shafts and
combining gear. I also do not have
acoustic data on turbines versus, say, diesel engines.
The point is that the propulsion system must be selected for
reduced sound rather than maximum power or speed, again, consistent with
mission requirements. This would be a
radical departure from current ship design.
Infrared Signature - Ideally, our ship should have a
temperature identical to the surrounding ambient air and water. One of the major IR sources is, of course,
the hot exhaust from the commonly used turbine engines. If we can’t find a better choice than
turbines, we need to, at least, suppress the heat of the exhaust by discharging
the heated air through a water mist or exhausting the air into the water[4] or
very near the waterline in a water-cooled discharge.
The rest of the hull and superstructure gets hot from
internal heat sources and heat absorption from the sun. The hull and superstructure need a cooling
system similar to the Nuclear/Biological/Chemical (NBC) washdown system. In this case, instead of washing away
radioactive particles, the washdown would serve to cool the ship’s skin and
reduce the IR signature.
Optical Visibility – Many weapons use optical sensing
for target identification, terminal guidance, and impact point selection. We must reduce or alter our optical signature
as much as possible by reducing ship and superstructure size and by applying
camouflage to break up or alter the ship’s outline. Interestingly, early WWII Gato submarines had
relatively large superstructures which, in combat, were quickly cut down to
reduce their visible detectability. We
must follow this example. The least
detectable superstructure is no superstructure.
While that may not be totally achievable, it is the goal we must strive
for. We must ruthlessly eliminate any
non-combat compartment in the ship. This
means no ship’s post office, no gym, no crew lounge, no chapel, no lawyer’s
office, etc. This is a ship of war not a
cruise ship. Every non-combat space that
can be eliminated allows us to reduce the size of the superstructure. I guarantee that every sailor will gladly
choose survival in combat over a coffee bar or video game lounge.
An intriguing area for research is the use of adaptive electrochromic
coatings/paint that can alter their color, reflectance, and other properties
depending on temperature, light and light angles, and electrical state. To the best of my limited knowledge, these
are not available for field use but they should be aggressively pursued as near
term research projects.[3]
Electromagnetic Emissions – This is our old friend,
EMCON. This is well understood and,
until very recently, totally ignored by the Navy. I won’t belabor this further other than to emphasize
that our conceptual ship cannot have any stray emissions and must be designed
to operate without active emissions to the maximum extent possible. This means emphasizing passive detection and
tracking of targets versus active. To
the maximum extent possible, fire control must utilize passive sensing. Every piece of equipment on the ship must
have a verified EMCON mode of operation.
It goes without saying that cell phones, video games, or any other
personal electric device must be banned.
Obscurants – ‘Smoke’ has been developed that can
provide multi-spectral interference (concealment) and can be deployed as any
other shipboard decoy canister.
Decoys – This is a vastly under-emphasized aspect of
stealth. Not to belabor the obvious but
decoys mimic a real target in hopes that an attacking weapon will be fooled
into selecting the decoy instead of the real ship. Decoys can take many forms from simple
emitters that broadcast the real ship’s radar frequencies to persistent,
floating, radar reflecting, multi-faceted ‘igloos’.
Similar to electronic warfare, the Navy has given relatively
little attention to decoy research and development. Current decoys are very basic and
limited. What is needed is a decoy that
simulates radar, infrared, and visible emission characteristics of the host
ship and has a useful degree of persistence.
We also need suitable doctrine and tactics for the
employment of decoys. For example, the
current tiny handful of decoys embarked on ships is woefully insufficient for a
high end naval battle. We need to be
capable of dispersing hundreds of decoys, not a handful. Let an enemy weapon find the literal
one-in-a-hundred signal that is the real ship.
Insert photo: Decoy 1.jpg
-multi-faceted radar reflector
Electronic Warfare (EW) – Despite the fact that
historical data shows that EW is far and away the most effective defensive
technique, the Navy has virtually ignored EW for decades. Even the SEWIP modernization program barely
pays lip service to the role that EW should play.
We need powerful emitters for jamming, false signal
injection, cyber attacks, etc. and the entire electronic warfare system must be
tied into the Aegis combat system so that it acts in a coordinated fashion.
Wake – Our enemies have wake homing torpedoes and no
truly stealthy ship would be without wake suppression measures. Unfortunately, wake suppression is
technically challenging and I’m not sure if any practical measures have been
fielded. The Navy has a patent on a wake
suppression technique using ultrasonics to reduce/remove the microbubbles in
the ship’s wake which are what allow a wake to be sensed and tracked.[1] Another patent describes a means of reducing
wake vorticity (turbulence) by siphoning off the boundary layer of water along
the hull.[2]
Design
Having come to an understanding of the various factors that
impact stealth, we can now conceptualize a maximum stealth ship design.
The ship will be as small as possible with only a minimal
superstructure – think a slanted, stealth version of a WWII Fletcher class
destroyer superstructure, maybe less.
All surfaces, hull and superstructure, will be fairly sharply angled and
will be completely smooth with no protruding pieces of equipment. The ship will, externally, appear to have no
equipment or weapons and items that are necessary for ship handling operations
will be fully retractable in one way or another.
Sensors will be either embedded flat panels or retractable
with an emphasis on passive sensors providing complete and continuous hemispherical
coverage with multitudes of redundant and overlapping sensors. Even navigation radar will be omitted. Instead, infrared and electro-optical sensors
will provide navigational information. This
may force us to become actual sailors again but that’s not a bad thing, is
it? Radar use will be limited to active
weapons employment and even that will be minimized.
Weapons will be retractable in various ways. Even the ubiquitous Mk41 VLS will be modified
with a completely flat cover instead of a multitude of separate hatches, each
with its own several-sided radar reflecting surfaces.
Except for specific ASW vessels, there would be no helo
facilities.
UNREP gear will be fully retractable.
This ship will require a complete revision in combat
operating procedures. The overwhelming
emphasis will be on passive sensors and greatly reduced communications (none,
during combat). Admirals will have to
trust the ship captains to understand their mission intent and then leave them
free to execute as they deem best. The
constant verbal diarrhea gushing forth from today’s ships will be a thing of
the past. This ship will operate unseen
and unheard.
Nothing will be allowed on the ship that does not have a
verified, shielded, EMCON operating mode.
The ship will not emit a single stray electron.
The ship will embrace bad weather, seeking it out and using
it tactically for whatever degree of cover it can provide.
The ship will be constantly passively ‘sniffing’ the electromagnetic
spectrum for its situational awareness instead of depending on the brute force
of radar. The crew and ship’s systems
will be constantly a hair’s breadth from active combat. Combat systems will have a full auto mode
which will be the standard mode in a combat zone. There won’t be time for human reactions.
The ship will be built for war, not cruising. Silent.
Unseen. Stealthy.
____________________________________
[1]https://patents.google.com/patent/US5787048A/en
[2] https://patents.justia.com/patent/5222455
[3]https://gardnerlaboratories.com/2013/11/22/chemistry-corner-more-color-changing-paint-byk/
[4]Discharge into the water will increase the backpressure
on the exhaust flow thereby reducing propulsion system performance. This is an example of prioritizing stealth over speed.
