Conceputal Armor For Modern Ships

Modern navies have all but abandoned armor for ships.  ComNavOps has demonstrated the fallacy in this approach.  The overall situation can be summed up thusly:  we are building multi-billion dollar ships that are susceptible to one-hit kills (literal and mission) due to lack of armor.

The arguments against armor, such as the one-hit killing power of torpedoes, have been debunked.

What is left now is to design a conceptual armor arrangement for modern ships that takes into account modern threats.

Let’s start by looking at the threats.

Large Anti-ship Cruise Missiles (ASCM or just ASM) – These are the heavy weight, generally supersonic missiles such as the BrahMos (Mach 3, 6000 lb, 28 ft long, 440 lb warhead) or SS-N-22 Sunburn/P-270 Moskit (Mach 3, 10000 lb, 32 ft long, 660 lb warhead).  These present a threat to the ship’s side and upperworks as well as having significant penetrating capability to internal compartments.

Small Anti-ship Cruise Missiles – These are the smaller, generally high subsonic missiles such as Exocet, Harpoon, or C-80x.  They typically carry 350-400 lb warheads.  These present a threat to the ship’s side and upperworks as well as having significant penetrating capability to internal compartments.

Mines – There are all manner of mines but for our purposes we can categorize them as contact or influence fuzed – the difference being the distance and depth at which they explode from the ship’s hull.  A contact mine is typically the venerable floating or near surface mine that would contact the ship’s underwater hull side.  An influence mine is more likely to explode under the ship’s hull but offset well to the side.  These present a threat to the ship’s structural integrity below the waterline but generally above the bottom of the ship.

Torpedoes – Generally, torpedoes are designed to explode under the ship’s hull.  These present a threat to a ship’s structural integrity at the bottom of the hull.

Artillery – Guns, whether ship or land based, are generally guns of up to 5” (127 mm) or 6” (155 mm) size.  Depending on the range, artillery shells present a plunging threat to the upper works and decks of a ship.

Close Range Missiles – These are small, close range missiles such as Hellfire.  These present a threat to upperworks and the sides of a ship, depending on the launcher height relative to the target.  They do not, however, have a great deal of penetrating power.

Fragmentation Missiles/Shells – These are generally small warhead missiles or shells intended to destroy exposed upper works and equipment.  A typical example is an anti-radiation missile intended to destroy radars and sensors.  These present a general shrapnel threat to upperworks and a specific threat to sensors and nearby equipment.

Miscellaneous – These include machine guns (0.50 cal, 20-30 mm, etc.), rocket propelled grenades (RPG), rockets up to 5” in size, etc.  These present a threat to upperworks and the sides of a ship, depending on the launcher height relative to the target.

I’ve intentionally left out anti-ship ballistic missiles because there are no sensor systems of sufficient range to make them viable threats.  A 5000 mile anti-ship ballistic missile is useless when the sensor/targeting range is on the order of hundreds of miles.

Having defined the scope of threats, it is now necessary to consider the likelihood of each threat.  In the inevitable tradeoffs of armor design, the likelihood of a threat will help determine where best to place our armoring efforts.  In order, the likelihood is

1. Small ASMs.  Modern naval combat will be mostly missile based and small ASMs are the most numerous and likely to be encountered.
2. Fragmentation missiles and shells will be commonly used to attempt to blind ships by destroying their sensors.
3. Large ASMs.  While potent, these are far less numerous and, therefore, less likely to be encountered.
4. Torpedoes are potent but less likely due to the simple fact that submarine attacks are challenging to set up.
5. Mines will be ubiquitous but are easily detected en masse and will be avoided with generally good success.

Everything else is relatively unlikely due to the short ranges required to launch the weapons.

In the normal course of armor design consideration, we would also include an assessment of the lethality of the various threats, however, we’ve already noted that every weapon is ‘lethal’ (mission or ship kill) to today’s lightly built ships!  Therefore, this is almost pointless and we’ll ignore it.

As we enter the meat of the discussion, note that I am not an armor expert.  Therefore, our discussion will be limited to conceptual arrangements rather than specific armor types, thickness, or specifications.  That’s a job for a naval engineer.

As we begin to contemplate the actual armor arrangement, we note from the preceding discussion that a ship has several distinct zones or bands that are each susceptible to different threats.  The main “bands” are:

• Upperworks – the upperworks are susceptible to horizontally impacting missiles
• Deck – the deck is susceptible to plunging artillery fire and plunging missiles that have executed a pop-up maneuver
• Side above the waterline – the above water side of the ship is susceptible to sea-skimming missiles
• Side below the waterline – the side below the waterline is susceptible to influence fuzed mines and torpedoes
• Bottom – the bottom is susceptible to torpedoes
• Internals – this includes the critical combat related command and control spaces, fire control, engineering, computer facilities, etc.
• Special mention: electronics and weapons – electronics and weapons are particularly susceptible to shrapnel in addition to direct impacts from all manner of shells and missiles

Having identified threats and their likelihood and recognized key zones of a ship, we are now ready to discuss the armor arrangement.  The arrangement is predicated on understanding the reason for armor.  While it is simple enough, it bears stating.

The purpose of armor is to maintain the ship’s combat capability (enable it to keep fighting) for as long as possible and to enhance the ship’s survivability.  The purpose of armor is NOT to grant total immunity.

Recognizing the purpose, this gives us some guidance as to how to design our conceptual armor. 

We need to protect the ship’s structural integrity and mitigate the main threat which is flooding (fire is actually the main threat to a ship but that’s more of a damage control issue rather than an armor issue).

We need to protect the ship’s weapons, sensors, and command so that the ship can continue fighting.

With those two goals in mind, here is the armor concept for the various zones.

• Upperworks – the majority of upperworks are devoted to a ship’s daily operational tasks such as small boat handling, replenishment, anchoring, and the like.  As such, they require only fragmentation armor protection.
• Deck – the deck is susceptible to plunging artillery fire and plunging missiles but these are less common occurrences.  Therefore, unlike WWII ship armoring, deck armor can be significantly reduced – perhaps needing only a couple of inches.
• Side above the waterline – the above water sides have been identified as likely targets and will need heavy armor bands sufficient to resist small anti-ship missiles and low level, horizontally launched rockets and small missiles.  Depending on the size of the ship, this is where several inches of armor should be placed.
• Side below the waterline – while the potential for damage is large from mines the likelihood is very low.  This area needs only enough armor to mitigate the effects of torpedoes which explode below the ship’s hull.
• Bottom – The bottom of the hull needs v-shaped, shock absorber mounted armor plates, multiple void spaces that alternate empty and liquid (foam, maybe) filled, and modified structural elements that are designed to absorb more than resist torpedo explosions.  Scaled down battleship torpedo defense designs and construction techniques are a good starting point and should be built into every ship.  This is less a question of pure armor and more an issue of proper structural design.
• Internals – the critical combat related command and control spaces, fire control, engineering, computer facilities, etc. require substantial armor in ‘cubic’ form – meaning, all around the compartments as opposed to just on the sides.
• Special mention: electronics and weapons – Weapons need to be armored to the point that only a direct hit can incapacitate them.  I believe that VLS systems are armored around the sides to direct blasts upwards but are not significantly armored against hits from above.  This is semi-informed speculation on my part and could be wrong.  If correct, we need to add topside armor to the VLS systems sufficient to protect against plunging shellfire and small anti-ship missiles.  The 5” guns need protection against shrapnel and near misses.  The WWII Fletchers had up to 2.5” of armor on their 5” guns and today’s guns should have a functionally equivalent amount.  Sensors are a challenge to armor because armor generally interferes with their function.  What can be done is to provide armored screens around the backs and sides of sensors and, for those that rotate, make the screens rotating with the sensor.  Thought should be given to housing the sensors inside armored pockets until needed and then extending when in use.  Precedent exists for such arrangements as observed in some of the more extreme stealth ships.

Compared to WWII armor designs, plunging fire is much less of an issue and armor should be concentrated more on the sides and less on the decks, on a relative basis.  Thus, we see a modern armor design that features a single, very heavy side band of armor combined with significant protection of critical internal compartments.  The hull bottom is every bit as critical but requires less in the way of pure armor and more in the way of structural design modifications, as we’ve addressed in previous posts.

Hand-in-hand with armor is intelligent ship design.  For example, outer compartments should be non-critical functions such as berthing, storage, machine shops, and the like with all such compartments designed to contain shrapnel and localize damage.  To an extent, the upperworks and outer compartments are sacrificial.  Being non-combat-critical, their purpose in combat is to act as ‘crumple zones’, to borrow an analogy from the automotive industry, and shrapnel sponges.

As with WWII armor, a ship’s side armor should be designed to detonate missiles as early as possible rather than allow deep penetration prior to detonation.  WWII armor research developed some very specific techniques (de-capping, for example) for the purpose.  Whether those would apply to detonating missiles or not, the concept remains valid – detonate the missile as far ‘out’ from the ship’s core as possible.  That, combined with locating non-critical compartments and functions in the outer areas should provide substantial sustainment of combat capability during battle.

Again, the goal is not to provide total, 100% immunity to all known weapons but to prolong the effective combat duration of the ship in the face of damage.

Below is a drawing of a Burke class destroyer illustrating the concept just described.  The heavier green is heavier armor with lighter green areas being lighter armor.  Note that the entire ship should be constructed of heavier material than is current practice.  Also, the ship's critical internals should be armored, as discussed.  The yellow band of the underwater hull represents a combination of armor and structural redesign for torpedo resilience.

Conceptual Armor Scheme