The weapons you find on warships and submarines. Not stuff that fires out of your belly button.
Shipboard weapons cover several areas:
Historically, the main determinants of AA effectiveness have been fire control- the ability of your radars to track enough targets, how fast you can fire your guns/get your missiles off, and how likely they are to hit their targets.
On the other hand, anti-submarine warfare conducted by subs is essentially an equal playing field, with the winner determined by a combination of equipment and skill (training).
Now, on to the different types of naval weapons.
Types of naval weapons
Used by ships since cannons were invented, but they became truly effective in the 19th century. The invention of explosive shells, proximity fuzes, and stabilization and fire control systems enabled ships to become convenient floating artillery batteries. Guns can be used in a fire support role for ground troops, for aircraft, point defense against enemy weapons, or to strike specific strategic targets.
The oldest form of surface weapon, and consequently usually the most reliable. In the early 20th century, an arms race resulted in bigger and more powerful guns being built, culminating in the massive guns of World War II.
Main guns were also the original form of shore bombardment. Due to their mechanized nature, their firing rate is much higher than field guns of similar caliber, which have to be light enough to be dragged around by trucks. One ship can provide nearly the same amount of shells on target at a time as an entire battery of field artillery. Their main limitation is typically range; the ship can only get as close to shore as its draft allows.
Modern guns are typically of lower caliber (3" to 5") than their predecessors from before WWII (12" to 18") but because of the overwhelming power of the missiles referred to above, most modern ships are not particularly heavily armored. Naval architects reason that a direct hit by an ASCM would be game over anyway; instead they use the space for more self-defense weaponry. Thus smaller shells will do just fine.
Modern guns are usually largely automated, aimed by radar, and have a rate of fire between 20 and 80 rounds per minute, a significant improvement over older weapons that required large crews, were aimed optically, and had slow rates of fire. Range is typically out to the visible horizon, some 10-15 miles. Some can be loaded with specialty ammunition for use against different threats, though the standard High Explosive is the most common and most useful. They may not be as powerful as missiles but they will get the job done cheaper, more reliably, and at close range, faster.
A note about the term "caliber": when talking about small arms (pistols, rifles, machine guns, etc) caliber simply refers to the diameter of gun's bore (and thus the width of the bullet). When talking about Naval guns, caliber refers to the ratio of the width of the gun's bore to the gun's length. In other words, a 16"/50 caliber weapon, like the ones carried by the old Iowa class battleships, has bore that's 16" wide and a barrel that's 16 x 50 = 800" (66 2/3 feet!) long.
- The US Mk 45 5"/54 caliber "lightweight" gun (and the 62 caliber version). Lightweight relative to earlier 5"/54 caliber guns, that is; the previous Mk 42 gun of the same caliber had a barrel that was some 50% heavier and a turret assembly nearly triple the Mk 45's weight. This comes at the expense of its rate of fire; at a maximum of 20 rounds per minute the Mk 45 is the slowest-firing ~5" gun currently in service and half the rate of fire of the Mk 42 it replaced.
- The US Mk 12 5"/38 caliber gun was the first truly dual-purpose gun (equally effective against ships and aircraft) employed by the US Navy, and was employed on essentially all American warships of destroyer size or larger built between 1934 and 1950 (along with quite a few smaller escort ships and as defensive armament on auxiliary ships) in a wide variety of both open pedestal mounts and enclosed turrets. Some of these could reach a rate of fire as high as 22 rounds per minute despite a significant portion of the loading process being manual, and the Mk 12 in all of its forms was famous for extremely high reliability.
- The US 6.1"/62 caliber Advanced Gun System, designed to restore "gun cruiser" like shore bombardment capability to the US Navy. Currently used only by the Zumwalt-class destroyers. Given the Zumwalt class places a heavy emphasis on stealth, the barrels are retractable when not in use. As of November 2016, this gun has no ammunition to fire, as the cost of the precision-guided LRLAP (Long Range Land Attack Projectile) ballooned to nearly $1 million per shell, which was deemed excessive and caused the LRLAP to be cancelled. No other ammunition had ever been designed for the Advanced Gun System, and it's expected to be years before a cheaper shell can be designed.
- The Russian AKM-130 130mm/70 caliber twin-barreled autocannon. When the original goal of a gun capable 60 rounds per minute (so as to match the smaller AK-100 100mm/70 caliber gun it was replacing) couldn't be reached, in typical Russian fashion the developers simply added another gun to the turret, bringing the combined rate of fire to 80 rounds per minute.
- The OTO-Melara 76mm/62 caliber gun is used as a smaller but rapid firing gun used by a number of navies, including the US FFGs and several of the US Coast Guard's cutters.
- The Bofors 57mm/70 caliber gun is the primary competitor to the OTO-Melara 76mm, which compensates for its less powerful shells with higher rate of fire. Likewise used by many navies, including the US Littoral Combat Ships and the latest class of Coast Guard cutters.
- Though there are none in active service today, the all-big-gun battleships of the 1900s to 1940s were perhaps the most fearsome naval fire support platforms ever. Their heavy armor meant that they could take fire from land-based guns and ask for more, and they typically mounted upwards of 9 very heavy caliber guns. The US Iowa class ships mounted 9 16"/50 caliber guns which they could fire about every 30 seconds, independently. This means either a full broadside of 9 rounds every thirty seconds or a rolling fire of 1 round every 3 1/3 seconds. For an enemy soldier, this was equivalent to a Volkswagen filled with high explosives landing on your position from 20 miles away every few seconds until the Marines told them to stop! That, or 9 50-foot craters suddenly appearing at your position at once.
- The Iowa and Wisconsin were last used during Desert Storm in 1991 to shell Iraqi positions. The Iraqis realized that RQ-2 Pioneer Unmanned Aerial Vehicles (some of the first UAVs used by the US Navy) were being used to spot targets for the big guns, and eventually just started surrendering when the UAV flew overhead, rather than get blown to smithereens from a ship so far away they couldn't even see her.
- The nine gun/three turret layout wasn't settled on until relatively late in the game, striking a balance of firepower (very heavy, long-ranged guns) and speed (more turrets or guns meant more weight to slow a ship down). Earlier designs carried varying numbers of guns in varying numbers of turrets, with one British dreadnought mounting fourteen heavy guns in seven turrets (named for the days of the week, natch. For those of you wondering, it's the HMS Agincourt, armed with 12"/45 caliber guns).
- The Japanese 18.1"/45 caliber Type 94 guns of the Yamato-class battleships were the largest guns ever mounted on a ship. They were officially designated as being 40cm (15.7") to conceal their true size. Their shells each weighed 1.5 tons. Each gun weighed 150 tons and each triple turret weighed 2,700 tons...larger than most destroyers of the time.
With the arrival of aircraft during WWI came weapons to keep them away. During WWII these were the primary anti-aircraft weapons, but were rendered obsolete by the combination of faster carrier aircraft, long range missiles, point defense missiles and CIWS. These are still in limited use for defense against "low-slow fliers" like helicopters or hypothetical small kamikaze aircraft flown by terrorists, as well as their effectiveness against small watercraft. This section focuses on dedicated anti-aircraft guns; note that other guns mentioned on this page may also be used against aircraft if needed.
- The Browning M2 .50 caliber Heavy Machine Gun was originally designed as an anti-aircraft weapon, and may still be used as such for slower, closer-in targets.
- The Bofors 40mm autocannon was widely during WWII. More advanced radar-directed versions are still used today by many navies (with accuracy improved to the point that it's a decent CIWS and also quite effective against small boats, such as those loaded with explosives for suicide bombing), with usually only 2-4 guns per ship compared to the dozens (or even hundreds on aircraft carriers and battleships) of the manually-operated versions in WWII.
- The Oerlikon 20mm cannon was also widely used during WWII, and newer versions continue to arm many vessels today.
Most WWII-era submarines packed some artillery guns on their decks. These guns, usually based on those used on surface vessels, were used to supplement their torpedoes for sinking ships, for bombing shore positions, attacking targets too small for torpedoes, or for defense against aircraft and surface ships. Most deck guns are exposed, though a handful were mounted in turrets. Deck guns are no longer used today, as modern submarines are not meant to engage the enemy in such a direct manner.
- The American 5"/25 caliber gun, used on most of their WWII submarines.
- The British XXII 4-inch gun.
- The Japanese 14 cm/40 11th Year Type gun.
Close-In Weapons Systems (CIWS)
Separately from or in cooperation with point defense missiles, these are radar-aimed gun systems designed as a last-ditch defense against incoming missiles. They are typically highly accurate and have absurdly high rates of fire; with the drawback of short range-even if you do score a hit, momentum will probably still carry the fragments of the incoming missile into the ship. Their ammo consumption is also generally so ludicrously high that even firing in bursts you may run out of ammo even well before a point-defense missile system would.
In addition to missiles, they can also be used against small boats and aircraft.
- The US Phalanx system uses two radars (both contained in a tall white dome) and a 20mm gatling gun of the same type used by most American fighters. Due to its appearance often referred to by American sailors as R2-D2 with a hard-on, and by British sailors as a Dalek.
- The Dutch Goalkeeper system, which uses the same tank-killing 30mm seven-barreled gatling gun as the A-10 Warthog. The bigger gun makes it somewhat more effective than the PHALANX, but also significantly heavier (in addition to taking up more below-deck space) and thus less suitable for small ships.
- The Chinese Type 730 CIWS seems to be a copy of the Goalkeeper's gun and turret, but with locally-designed electronics. The aircraft carrier Liaoning apparently has some of these that were put on steroids, having a larger turret and a eleven-barrel 30mm gatling, designated Type 1130.
- The Russian Kashtan combined gun-missile system, combining short-range missiles with a pair of potent six-barrel 30mm gatling guns that a certain Russian soldier would be pleased with. Kashtan is an enlarged version of the land-based 2K22 Tunguska, using the same missiles but replacing the latter's single-barrel 30mm autocannons with the gatlings that were already in widespread Soviet Navy use. Its only real shortcoming is that it's huge (a single Kashtan turret weighs 16 tons and takes up nearly 20 square meters worth of deck).
- The Russian AK-630 family consists only of the 30mm gatlings, and is still used for ships that are either too small or lack empty deck space for the massive Kashtan. Unlike the other CIWS systems listed, the AK-630's fire control radar is mounted separately from the turret. The original standard arrangement was two turrets close together with a single radar mounted nearby◊ (or on very small vessels like missile boats, sometimes a single turret), but now a relatively stealthy turret is offered containing two of the gatlings mounted one directly above the other as the AK-630M-2 Duet◊.
- The Swiss Oerlikon 35mm Millennium gun stands out for being a CIWS that can be mounted on literally anything that has a few square meters of empty space, as it's entirely self-contained and just bolts onto the deck. Unlike most CIWS systems that rely on high rate of fire, the Millennium gun is a single-barrel revolver cannon that fires somewhat larger rounds with extreme precision that explode right in front of the target to shower it in shrapnel. Given Switzerland's location, it exists entirely for export to nations that actually have a coastline.
- The Spanish Meroka is notable for being 12 20mm barrels stacked six on top one another in a single turret with onboard radar. Much like the Swiss Millennium, the weapon does not rely on high rate of fire, and instead on its massive twelve-round salvoes that act much like a giant shotgun.
Machine guns and autocannons
Exactly What It Says on the Tin. Smaller-caliber, rapid firing. Machine guns mounted on ships have several advantages over their land-based bretheren: The ship itself provides a stable firing platform, an armored position to fight from, and storage space for literally tons of ammunition. They provide defense against fast-moving small vessels, and in port against personnel on foot and in vehicles. When mounted in small, fast moving boats, they become the primary armament. Some designs can be mounted in automated turrets or remote weapon systems, while others must be aimed and fired by hand.
- The US M2 .50 cal heavy machine gun. You can use it for anything. If you could find a way to get rid of the water in between, you could probably sink submarines with it.
- The US M240B 7.62mm medium machine gun.
- The US Mk 38 Bushmaster is a 25mm chain gun that comes in two varieties: The manually-operated Mod 1 requires a sailor to stand out on deck to aim and fire it, while the Mod 2 is remotely controlled and aimed by video camera (though it can still be manually fired if needed). Both need sailors standing by with extra ammo to reload it with.
- The US Mk 44 Bushmaster II is a 30mm chain gun (as the name implies, and improved version of the Mk 38) that's mounted in a fully automated turret and is loaded from inside, removing the need to have sailors exposed on the deck to reload it. This design requires below-deck mechanisms to function.
- The Soviet/Russian DShK 12.7mm heavy machine gun.
- The Soviet/Russian PKM 7.62mm medium machine gun.
After WWII, guided missiles began to supplement and eventually replace guns as primary shipboard weapons. Missiles and rockets have since gone on to cover multiple roles.
Older ships use rail-based launchers or box launchers. Rail launchers usually had one or two missiles sitting on rails, basically providing you with one or two missiles available to launch before the launcher would reload from an automated magazine below decks. A box system came with say eight missiles in a launcher out on deck which you would then have to reload manually. These looked visually impressive, but once all missiles were expended, they would take a little while to reload.
Today, the Vertical Launch System (VLS) is generally used, with missiles placed in silos inside the hull and launched on command. This is basically a box system with a much higher ammo capacity: it allows you to get a missile off about once a second (or faster), can use different types and sizes of missiles easily, is mechanically much more simple and reliable than the automated reloading and aiming systems associated with rail and box launchers, and reduces your radar cross-section (making you harder to find and hit). However, it isn't easy (or sometimes not even possible) to reload at sea without an ammo ship and special crane.
A Surface-to-Air Missile (SAM) is a missile which is launched from a surface platform and attacks an aircraft or missile. Invented in the 1950s, they vary from short-ranged, barely guided early models to modern missiles capable of hitting other missiles in mid air and doing so from hundreds of miles away from the launching ship. Unlike their air-to-air counterparts, naval SAMs generally use a command-guidance or semi-active homing scheme; that is, the launching ship either guides the missile the entire way to the target or illuminates the target with a radar beam, the reflection of which the missile homes in on. Considering the self-guiding, "fire and forget" ability of modern missile technology, this seems an anachronism but confers several advantages: by shifting the processing power to the launching ship, the missiles can take advantage of bigger computers, can have more warhead or fuel for the same size missile, and are cheaper, with the same guidance capability. Since the ship can usually point its radars in any direction, following the target is not a problem, either.
Area defense surface-to-air missiles
Missiles with a range in excess of 10 nautical miles, used to defend multiple warships. Usually found on destroyers and a job requirement for cruisers. Most are designed to hit incoming missiles and find regular aircraft laughably easy targets.
- The US Standard series, especially linked in with the Aegis system that allows for dozens of targets to be engaged simultaneously and for sharing of targeting information. The most recent iteration is the long-range RIM-174 Standard Missile 6. Originally fired from single- or double-rail launchers, the Mk 41 VLS has become almost universal over the past few decades.
- The Soviet/Russian S-300/SA-N-6 "Grumble" and its successors (the S-300FM/SA-N-20 "Gargoyle") and clones (the Chinese HHQ-9). Launched from specialized cold-launch VLS, though China now has a multiuse grid VLS.
- The British Sea Dart system, now retired and replaced with the Sea Viper. Fired from a double-rail launcher.
- The Franco-British Aster-30 (the aforementioned Sea Viper in British service). Fired from the Sylver VLS, a modular system similar to the Mk 41.
- The Indo-Israeli Barak 8, fired from a single-purpose grid VLS.
Point defense surface-to-air missiles
Found on most smaller ships and also ships like carriers which have no other air-defense systems. These are generally very short-range and are installed as a last ditch effort to save the ship from being hit by missiles that the area-defense weapons miss. These sacrifice range and explosive power for for speed and accuracy, and unlike CIWS systems have the ability to engage multiple targets simultaneously. Many of these still use box systems so that they can be installed on a variety of different ship types, and because keeping the time from launch to impact short is of deadly importance.
- The US RIM-7 Sea Sparrow. These are fired from deck-mounted 8-round box launchers.
- The US RIM-162 Evolved Sea Sparrow. Looks rather like a miniaturized Standard despite being an evolution of the Sea Sparrow. Compatible with existing Sea Sparrow box launchers but in newer ships usually fired from a VLS. Four of them can be packed into a single "cell" of the Mk 41 VLS used for the Standard family, and for smaller ships the Mk 48/Mk 56 family is used.
- The RIM-116 Rolling Airframe Missile (RAM), which was jointly designed by the US, Turkish, Hellenic, German, Egyptian, and South Korean navies as a replacement for the PHALANX CIWS. 11 or 21 can be carried in a box launcher. The 11-round version is mounted on the SeaRAM turret, which is basically a modified PHALANX turret, including the distinctive radar dome, with the launcher in the place of the 20mm Gatling. This version is, like the PHALANX, a fully autonomous system. The 21-round launcher requires an external fire control system and thus is only suitable for replacing PHALANX on larger ships, while SeaRAM can be mounted on almost anything.
- The Soviet 9K33M Osa-M/SA-N-4 "Gecko", found mounted on a wide variety of their ships. While the land-based version (9K33 Osa/SA-8 "Gecko") carries 6 missiles in box launchers, the naval model is fired from a twin-rail launcher that, quite unusually, is mounted on a retractable platform with a circular plate covering it when not in use.
- The Soviet 3K95 Kinzhal/SA-N-9 "Gauntlet", the replacement for the Osa-M. Fired from a VLS.
- The Soviet 2K22 Tunguska/SA-N-11 "Grison", the missile half of the combined gun/missile Kashtan CIWS.
- The French Crotale eight-tube system.
- Also made by the French is the Mistral IR missile, usually mounted in a lightweight six-tube launcher.
- The British Sea Wolf, which initially used a 6-box launcher but now only the improved VLS version (which also features slightly improved range) is used. Highly accurate; during tests it even shot down 4.5-inch gun shells.
- The Franco-British Aster-15, which is simply Aster-30 with the booster rocket removed. This dramatically reduces its range but also reduces its minimum range (making it more suitable for point defense) and can be fired from a shallower-depth version of the Sylver VLS (allowing it to be carried by smaller ships, and to take up less space on aircraft carriers).
- The Umkhonto, a South African VLS-launched IR missile.
- The FL-3000, a Chinese IR missile that is similar in function and capability to the RAM.
- The Indo-Israeli Barak 1, mounted in a compact 8-cell VLS.
These are typically the nastiest surface-to-surface threats out there. Also known as Anti-Ship Cruise Missiles (ASCM), they can be launched by aircraft, submarines, ships, or land-based launchers, fly more than 100 miles at extremely low altitude, accelerate to supersonic speed, weave to evade interception, and then impact the target with enough explosives to blow some smaller ships in half.
They generally come in two types. The first, as described above, are called sea-skimmers. They fly a few feet above the waves to make detecting them on radar extremely difficult, usually at subsonic speeds to extend range. Newer ones are capable of evasion, and some can be programmed to fly a roundabout path to the target to hide where it came from. This is so terrifying for defending units because the low altitude reduces the amount of time to react (a minute or less). Even the best air defense missiles take time to reach the target...and the incoming missile may take less time than that to impact.
- The US AGM/RGM/UGM-84 Harpoon (the designation varies depending on whether it's air, surface or submarine launched)
- The French Exocet, infamous for its high performance in The Falklands War and IranIraq War.
- The Russian Kh-35 Uran/SS-N-25 "Switchblade", also known as "Harpoonski" for being a blatant copy of the Harpoon.
- The Russian 3M-54 Klub/SS-N-27 "Sizzler".
The second type are missiles that fly extremely high and extremely fast, and then dive down onto the target. These are less common today because advances in SAMs mean that despite their speed, their high altitude means that shipboard radars can track them almost their entire flight, giving numerous chances for defenses to engage them. Their one advantage today is that they can typically carry a larger warhead. Some Soviet missiles of this type had one missile in the salvo one would fly up to and use its active radar to search for targets, forwarding this data to the other missiles which remained at low altitude. The missiles could be programmed so that half of a salvo would head for a carrier target, with the rest dividing between other ships. If the high flying missile was shot down another from the salvo would automatically pop up to take its place. The most dangerous (such as those listed below) are the ones that are actually a hybrid of this type and sea-skimmers, which after traveling some distance drop down to extremely low altitude yet maintain their very high speed.
- The Russian P-500 Bazalt/SS-N-12 "Sandbox"
- The Russian P-700 Granit/SS-N-19 "Shipwreck", its "little cousin" the P-270 Moskit/SS-N-22 "Sunburn" and the new Indo-Russian PJ-10 "Brahmos"
Land Attack Cruise missiles
Cruise missiles are flying, self-guided bombs. Many are closer to small unmanned aircraft filled with explosives than they are to regular missiles, being jet-propelled rather than rocket-propelled. They were first invented in World War I, but the earliest versions to see action were the German V-1 missiles in World War II. Some nations forgot the ''unmanned'' part. Modern cruise missiles will usually fly slower than other types of missiles (subsonic), cruise to the target at low altitude for hundreds of miles, and then impact with "pick a window" accuracy on a target. They are able to be programmed to evade air defenses on their own, and some of these can be fitted with nuclear warheads. Ships or submarines equipped with Vertical Launch Systems can pump out dozens of these at a time. They are used to strike at strategic targets either close to shore or far inland without endangering the launching unit very much.
- The most (in?)famous of these is the US Tomahawk, which can be fitted with a single warhead, cluster munitions, or a W61 nuclear warhead.
As the name would imply, these missiles fly to their target in a ballistic arc. They are not nearly as accurate as cruise missiles but typically have much longer (intercontinental) range and response time and as such are today only carried by submarines and fitted with nuclear warheads. Each missile can be fitted with Multiple Independent Reentry Vehicles (MIRV) which are warheads that can hit several targets independently, and they can be fired while submerged. The job of SSBNs or "Boomers" are to hide until such time as they are ordered to fire these, and usually carry 1-2 dozen of them. Thankfully, no nuclear ballistic missiles have ever been fired in anger.
- The US Trident II, carried by Ohio class SSBNs.
- The Russians currently operate the Bulava ballistic missile on its Borei class SSBNs, and its last remaining Typhoon, the latter as a test platform. The backbone, however, remains variants of the R-29 missile on its Delta class boats.
- The French M45 and M51, carried by the Le Triomphant class.
- The People's Republic of China are widely believed to be working on anti-ship ballistic missiles for use against US carrier groups. Since such a thing has never been attempted before, nobody knows how well it will work.
- Though long retired, the Polaris missile is notable for the fact that the US and Italian navies both wanted to fire them from surface ships.
This category covers weapons that primarily function below the surface.
Essentially self-propelled underwater bombs, modern torpedoes have evolved quite a bit from the straight-running, short ranged weapons seen in World War I and World War II. The modern varieties come in two general types; heavyweight and lightweight. Heavyweight torpedoes are only carried by submarines, and can target subs or surface ships, while lightweight torpedoes are launched by aircraft and ships, but can only target submarines. We'll leave the lightweights for the anti-submarine section.
Heavyweight anti-ship torpedoes are truly fearsome weapons. Most have ranges in the dozens of miles, they can move at double the max speed of most ships and submarines, and due to their large size have bigger warheads than any other naval weapon (excluding nukes, of course—though there are nuclear-tipped torpedoes); many are capable of blowing cruiser-sized vessels clean in half. Newer ones also have multiple guidance methods; they can be quietly guided by wires from the launching sub until a certain distance, but then use acoustic seekers, and their detonators can be magnetic. They are also very difficult to decoy.
- The US Mk 48 ADCAP heavyweight torpedo is the very latest long-range, surprise underwater demolition equipment. It's also used by the Canadian, Australian, and Dutch navies.
- The British Spearfish is a comparable weapon.
- The Chinese Yu-6.
- The German DM-53 heavyweight torpedo, with its superb fiber-optic guidance system
- The Soviet/Russian Type 65-76 torpedo is the largest heavy torpedo ever deployed, with its DST92 variant having an even larger warhead than the WW2 Japanese Type 93 "Long Lance".
While the heavyweight behemoths described above can also catch and destroy submarines (and are very good at it) they are typically too large and heavy to be carried by aircraft, and take up unnecessary space on surface ships. Lightweight torpedoes are about 1/3 as heavy and are still deadly weapons. They take a "just enough" approach to destroying submarines: they are shorter-ranged than heavyweights; they won't blow one in half, but instead are designed to cause a sufficiently large explosion sufficiently close to the submarine to crack its pressure hull, burst pipes, blind its sonar, and otherwise cause chaos within. Helicopters can usually carry two or three of these, surface ships these days usually have four to six of these ready to go (with plenty of extras in the magazines), and maritime patrol aircraft can carry sometimes as many as eight.
- The US Mk 46 Mod 5 is a refinement of a design that has been around since the 60's.
- The US Mk 54 is its intended replacement. It combines the warhead and sonar of the Mk 50 (the previous intended replacement of the Mk 46, until post-Cold War budget cuts made a torpedo more expensive than many of the submarines it would be fired at impossible to justify) with the body of the Mk 46.
A depth charge is a bomb that is dropped in the water and set to detonate at a certain depth; either by pressure or by a timer. Their advantages are that they are cheap and simple to operate; their disadvantages are that they are very short ranged and unlike torpedoes, will not follow their targets around until they hit them. Also, during depth charge attacks, the attacker must pass over the submarine's location, at which point sonar contact is lost. The resulting explosions will also blind sonar, making it difficult to verify a target's destruction.
Depth charges were very common in World War I and World War II but few navies carry them today. Like lightweight torpedoes, these are not designed or intended for direct hits; near misses would be good enough.
Anti-submarine mortars were devised in World War II, due to the ineffectiveness of depth charge attacks. These weapons launch explosives ahead of the ship, while there is still sonar contact with the target. The projectiles are equipped with contact fuzes, which detonate on impact, making them more effective at sinking submarines if a hit was scored, and since they only detonated on contact, an unsuccessful attack would not disrupt sonar contact as depth charges would.
- The British Hedgehog and its successor, Limbo.
The successor to anti-submarine mortars, anti-submarine missiles and rockets function on the same principle as an anti-submarine mortar.
A rocket or a missile carries a lightweight torpedo or depth charge out some distance from the launching ship, and then drops it into the water, where it activates and acts like a normal torpedo or depth charge. Some are simply ballistic (rocket flies in an arc, drops torpedo) while others are guided. This is a good way for a surface ship to keep itself away from a sub. The one exception to this is when the "depth charge" carried by the rocket is actually a ''Nuclear Depth Bomb'', in which case it will take out every submarine within a two mile radius or so of the impact point. Some such weapons offer (such as the original ASROC, and early depth charge rockets) only minimal increase in range over the torpedoes they carry, with the actual advantage being that they're much faster than the torpedo and drop in right on top of the submarine so that it'll have little time to evade.
- The US RUR-5 ASROC (AntiSubmarineROCket) and its successor, the RUM-139 Vertically Launched ASROC (VLA) which has substantially increased range. Basically a Mk 46 torpedo with a rocket attached. The ASROC could also carry a Nuclear Depth Bomb in case the ship ran into serious submarine trouble. The original ASROC's range was actually shorter than the Mk 46 torpedo it carried, with the advantage being that it could rapidly drop that torpedo directly above a submarine and thus give much less chance of evasion. VL ASROC on the other hand can actually fire on a submarine from outside the range of the sub's own torpedoes, which is a huge advantage if the submarine is detected that far out.
- The Australian Ikara, now out of service. Mocked by submariners as standing for "Insufficient Knowledge And Random Action", despite being significantly superior to the original ASROC on account of having double the range and being capable of mid-flight guidance.
- The Russians use the RBU-1000 and RBU-6000 multi-barrel rocket launchers. These remain in use largely because they take up so little deck space anyway, because the shallow yet cluttered waters of the Baltic Sea (a major Russian Navy operating area) can reduce sonar detection range to the point that such mortars are occasionally viable, and because they can be used as a last-ditch torpedo defense (fire the mortars in the direction of an incoming torpedo and hope for the best).
- The Soviet Metel (SS-N-14 "Silex"), similar to the Ikara but larger and longer-ranged. Unknown to NATO until after the fall of the Soviet Union, there is also an anti-ship version, the "Rastrub". Still used for as long as they last, but no longer in production.
- The Soviet/Russian RPK-2 Viyuga (SS-N-15 "Starfish") and RPK-6 Vodopad (SS-N-16 "Stallion") have largely replaced the Metel. These were originally submarine-launched weapons, but now are also used on surface ships by being launched into the water out of a ship's torpedo tubes, then popping back up to the surface and launching into the air, then flying to the target submarine and dropping a torpedo or nuclear depth bomb. This might seem overly complicated, but it allows for the missiles to fired by any ship with standard Russian 533mm torpedo tubes, as opposed to needing the large deckspace-consuming launchers of the Metel.
The reason why we have Minesweepers. Mines, like their land-based brethren, are bombs that sit inert until they are triggered by some external stimulus. There are literally hundreds of types of mines, and they are all deadly. Any seagoing vessel or aircraft can be a minelayer, and all ships and submarines are vulnerable (or, as the saying goes, any ship can be a minesweeper once.) The best ways to categorize them are:
- Position in the water
- Moored at some fixed depth from the bottom
- Resting on the bottom
- Buried under the bottom
- Detonation mechanism
- Contact (something touches the mine)
- Acoustic (the sound of a specific ship)
- Magnetic (the magnetic signature of a metal hull)
- Pressure (the pressure of a ship or sub passing over them)
- Timed (the mine detonates when its timer runs out)
- Command (whoever laid the mine sends a signal to detonate)
The most insidious mines use a combination of the above; for example, there are mines that sit on the bottom, listen acoustically for a certain ship type, and then only float to the surface after a certain number have passed by, and only detonate when it gets the right magnetic signature to be sure it is close enough.
As an interesting bit of trivia, torpedoes are actually an offshoot of mines, with the original torpedoes being a type of sea mine named for an electric ray that would sting predators that came too close. Some clever wit decided to drag one of these behind a Torpedo Boat, and later someone decided to attach it to the front of the boat, before someone was finally clever enough to just leave the crew off and let the whole rig sail off at a target unattended, creating the Self-propelled Torpedo. More recently, things have come full circle with the CAPTOR (enCAPsulated TORpedo) mine, which is a mine containing a torpedo. When it detects a submarine within range that matches the acoustic profile of an enemy, it releases the torpedo.
Mines can be planted either by hand, by air, or by dedicated ships (minelayers). Some mines can also be deployed from submarine torpedo tubes.
While not necessarily a weapon in and of themselves, the outer ring of air defense for a sufficiently large strike group will be formed by the carrier's air wing. Airborne early warning aircraft extend the radar horizon and fighters can visually identify and engage hostile aircraft, or provide early target information for naval SAMs. Many fighters are also light bombers/attack aircraft and can be used versus surface ships, and helicopter squadrons provide an antisubmarine capabililty.
There are three standard methods for launching fixed-wing carrier-based aircraft. The most conventional is Catapult Assisted Take-Off But Arrested Recovery (CATOBAR), in which a steam catapult (or starting with the USS Gerald R. Ford, scheduled to enter service in 2016, an electromagnetic catapult) is used to launch the aircraft, and on landing the aircraft must catch one of a set of arrestor wires with its tailhook. The second is Short Take-Off and Vertical Landing (STOVL), which dispenses with the need for catapults and wires but requires specialized aircraft that are usually lower in overall performance.note The third is a hybrid of the other two, Short Take-Off But Arrested Recovery (STOBAR), which uses similar aircraft to CATOBAR but doesn't require heavy, expensive and maintenance-intensive catapults.
- The F-14 Tomcat of Top Gun fame was considered the most powerful naval fighter of its day. It is now retired from US service with a few hanging around in Iran. Where they're used on land due to lack of carriers, and not actually used that much at all which is why they're not too worn out to fly like the American ones. Its AIM-54 Phoenix missile was the longest-range air-to-air weapon ever deployed, able to reach out and touch someone upward of 100 nautical miles (190 km) away, but they were almost never used outside of tests due to being so expensive.
- Its replacement, the F/A-18 Hornet and especially the enlarged F/A-18E Super Hornet, is a "strike fighter" which can attack surface or air targets.
- There's also the EA-18G Growler, a dedicated jamming aircraft built into the Super Hornet airframe. Often borrowed by the Air Force, who retired their dedicated jammers over a decade ago.
- Finally now entering service is the C-model of the F-35, which has greater range and payload than the B-variant due to omitting the lift fan. And, for that matter, the Super Hornet it will be complementing for the foreseeable future.
- The E-2C Hawkeye provides long-range radar coverage.
- The SH-60 Seahawk helicopter comes in several flavors, of which the B, F, and R variants are designed for antisubmarine warfare.
- Many navies without any other air capability will at least have some helicopters for anti-submarine, anti-surface, and general purpose work. It helps that they can land on pretty much any ship with a decent amount of flat deck space.
- The US Marine Corps and most non-US navies with a fixed wing capability tend to use aircraft with STOVL capability, as it allows for real fighter-bombers to fly off of a smaller carrier without expensive catapults and arresting gear. The most famous sea-borne STOVL aircraft is the Harrier, originally developed by the British, then later refined by a joint US-British effort and exported around the world. Often their carriers have a "ski jump" ramp at the front of the flight deck, which allows Harriers (and any future STOVL aircraft) to take off with a larger payload.
- Its intended replacement is the STOVL variant of the F-35 Lightning II (the F-35B), which was developed by an international effort led by the US and UK. Because the F-35B can carry a larger payload than the Harrier, it's unsafe to land it vertically while fully loaded; to avoid the wasteful dropping of unused weapons (which tend to be expensive) before landing, a technique has been developed to use thrust vectoring to slow the aircraft down enough that it can come to a rolling stop without the need for arresting gear.
- There are actually three distinct Harrier airframes. The original British Harrier was the most primitive of the three, and the only naval users were the US Marine Corps (designated AV-8A), the Spanish Navy and the Royal Thai Navy (with hand-me-down Spanish Harriers), all of whom have retired them. The next was the Sea Harrier, a navalized and considerably improved version that was equipped with radar so that the Royal Navy, having retired all its CATOBAR carriers, could still have fighter support. These were also the fastest Harriers, and were later given the excellent Blue Vixen radar allowing them to fire AMRAAM missiles. Due to budget cuts they were prematurely retired by the Royal Navy before the F-35 was available to replace them. The only other operator is the Indian Navy. The final version is the Anglo-American Harrier II (AV-8B in US service), which has a larger airframe and a correspondingly more powerful engine, giving it superior payload and range. These are used by the Marines and the Spanish and Italian Navies, and some RAF Harrier IIs were transferred to the Royal Navy as a stopgap replacement for the retired Sea Harriers. Some Marine Corps, Spanish and Italian Harrier IIs have been upgraded to the AV-8B Plus, which gives them APG-65 radars removed from F/A-18C Hornets when the latter got better ones installed, allowing the Harriers to use AMRAAM. A proposal to similarly upgrade British Harrier IIs with the Blue Vixen radars from the retired Sea Harriers, but this was rejected as too expensive.
- The French Navy, the only other one with a modern catapult-equipped aircraft carrier, uses the Dassault Rafale M. It lies somewhere between the standard F/A-18 and the Super Hornet in payload but is stealthier than either of them.
- Russia, China and India also use carriers with a "ski jump", but a steeper one than normally used for STOVL aircraft. Instead they use STOBAR aircraft, which are adapted from the Sukhoi Su-27 "Flanker" and Mikoyan MiG-29 "Fulcrum" land-based fighters.
This category covers electronic and sensor systems used to enhance a ship's combat capabilities.
The orginal naval sensor was naturally the "Mark I Mod 0 Eyeball", but ever since the idea of a telescope came about in the 1600s, people have been looking at ways to improve on that. Modern optical sensors often come with myriad of useful features, such as very high magnification, automatic stabilization systems, night vision, thermal vision, and automatic tracking of targets. Even with all these advancements, however, the use of common, inexpensive binoculars is still practiced by all navies for navigation and observation.
One of the hardest problems in early naval gunnery was the problem of determining the range to target. The angle of the target is easy to figure out, and it's relative speed laterally to the firing ship is relatively easy to calculate by measuring the change in it's angle, so you can figure out the lead required. But figuring out how far away it is was very difficult to do; and during combat it often boiled down to firing a salvo, observing the splashes produced, and then adjusting and trying again until a hit was achieved. This is obviously inefficent and also gives the enemy the opportunity to evade. Every time the range changed significantly, you needed to start the process over again; so usually what would happen is that you'd have to close with the enemy until the range so short that it was impossible to miss, exposing yourself to enemy fire in turn.
Optical rangefinders were the first attempt to solve this problem; basically a series of lenses and mirrors were arranged in such a way that two images of a target were produced from two different angles, and then those images compared such that with a little trigonometry a range could be calculated. This worked alright, but these systems were large, heavy, complicated, fragile, and expensive, so they would often only be found on the largest ships. Even then, they could be subject to significant error, so some trial and error shooting was still required for an accurate range. The ship that "found the range" first would then relay that information to the rest of her fleet so they could all zero in on that target.
Radar, as discussed below, largely solved the ranging problem, but there are still situations in which radar is less useful, particularly against small or stealthy targets that don't show up on radar well, or when you don't want to give your presence away by radiating a radar signal. Lasers were invented in the 1960s and make a handy rangefinder, by shining a laser on the target and timing how long it takes the beam's reflection to return. There are handheld versions, but also optical sensors often have laser rangefinders packaged with them, allowing an operator to see exactly how far away anything they are looking at is, and then relay that information to fire control systems.
Radar was invented just prior to World War II and its development revolutionized naval warfare. Radar works by sending a radio wave out, waiting for a reflection of that wave off a solid object to return, and then measuring the time the round trip took. Knowing the speed of the radio wave, you can easily calculate the distance it covered. Not only did the invention of radar neatly solve the ranging problem, it also allowed targets to be accurately be detected and tracked well beyond the range they could be seen at, at night, and through smoke and fog. Modern radars can be generally divided up by what function they are designed for:
Air Search Radars
These radars are optimized for detecting and tracking flying objects, particularly aircraft and missiles. The range they can find airplanes at depends on how much power they can put out, and is limited by curvature of the earth, and so they tend to be mounted very high up on the ship and consume enormous amounts of power; usually they are the single largest consumer of electrical power on any ship they are mounted on. Since aircraft tend to move very quickly compared to ships, and missiles are a huge threat to ships, they also have the ability to detect track very fast and small objects. Modern phased-array radars can track dozens of targets simultaneously at very long ranges.
- The US SPY-1 and its variants is currently the gold standard of shipboard air search radars, capable of simultaneously detecting and tracking hundreds of targets at extreme range, even up into space.
Surface Search Radars
Surface search radars are designed to look for objects close to the surface of the sea. As ships tend to move more slowly than aircraft, they do not have the same tracking speed as air search radars, but tend to be much smaller, lighter, and cheaper. They are ranged mainly because the curvature of the earth gets in the way of seeing objects low to the water, and so tend to use less power as it's not necessary to look so far away. Some surface search radars are futher specialized for anti-submarine warfare, being designed to look for small objects very close to the water, like periscopes.
Fire Control Radars
These radars are designed specifically for getting highly accurate information about a target's range, bearing, course, speed, and (sometimes) altitude, and then passing that information to a gun or missile system. Sometimes, particularly with gun systems, they are also designed to track the outgoing projectiles and any splashes they produce as well, so that they can see how much the last salvo missed by and adjust fire for the next shot. Often these have a very narrow field of view, so the target must be first detected by a search radar and then its location "handed off" to the fire control radar. Laser-based systems, as described above, can also serve this purpose, usually for short ranged guns that can't fire over the horizon anyway.
Many ships and aircraft have warning systems that will detect these signals and tell operators that they are being targeted by a fire control radar, leading to an entertaining secondary use for these systems as a psychological warfare tool: if those alarms are going off, someone may be trying to kill you, and perhaps you should leave the area now! However, operators must also bear in mind that doing this to someone is generally considered impolite and provocative and depending on the country, the reply might be in the form of weapons fire or a declaration of war.
Sonar is the primary sensor used by submarines, and an important secondary sensor for surface ships and aircraft. Sonar uses sound waves instead of radio waves to detect ships and submarines. It is much less precise and consistent than radar due to the nature of the ocean environment and sound compared to the atmosphere and radio, but it can also convey more information about the target than radar. It comes in two main flavors:
Active sonar works exactly like radar does, but using sound instead of radio: very powerful and large transducersnote broadcast a loud "ping" noise into the water, and then sensitive hydrophonesnote listen for echoes and time how long it takes them to get back. Knowledge of water conditions is then used to calculate the local underwater speed of sound, and a bearing and range to target can be determined. After enough pings, you can also calculate the target's course, speed, and depth. Active sonar can also be used to find the depth of the water, and to detect ice or mines.
Nearly all submarines, and any surface ship designed for antisubmarine warfare, have an active sonar system installed, but most navies are very cautious in their use of it, as the very ping it produces both gives away your general position and instantly identifies you as vessel designed for undersea warfare. Since it's much harder to make a surface ship stealthy in the first place, they are much more likely to "go active" than submarines, who will likely only do so if they are convinced they've already been detected anyway.
Passive sonar works by simply listening to the water with hydrophones, observing the direction the sound is coming from, and analyzing its frequency and other characteristics. This is of course much stealthier than active sonar, and can give you a lot of information about whatever you are listening to; skilled sonar operators can readily identify a ship's class by how it sounds and what frequencies it produces, and can sometimes even identify individual ships within a class and what equipment they have running. However, it has one key drawback compared to active sonar: it won't tell you the range to the target, and thus it also won't give you data about its course and speed. It is possible to get an estimate of the range using a technique called Target Motion Analysis, but this takes an extended period of time and is not very precise. Passive sonar further subdivides into hull-mounted sonar, which is hardy and convenient, but less sensitive and more likely to be drowned out by the sound of the vessel it is attached to, and towed-array sonar, which is towed well behind the ship and is much more sensitive and less vulnerable to one's own noise, but is also more fragile and may restrict maneuvering.
Sonobouys are not strictly weapons per se but are still an important part of hunting submarines. They are basically disposable buoys with small sonar systems hanging underneath them, underwater, that can be launched by aircraft or thrown over the side by surface ships. The acoustic data they gather is then transmitted back to the parent ship or aircraft, effectively providing the originator with the ability to listen in more than one place at the same time. Some sonobuoys use active sonar, while others use passive sonar only; most anti-submarine aircraft carry some of both types.
Magnetic anomaly detectors (MAD)
Magnetic anomaly detectors are used to detect a submarine's metallic profile, by using the earth's magnetic field as a baseline and then detecting the distortion created by a large metallic object where one is not expected to be. They can be carried by ships or aircraft (to avoid their own magnetic field interfering with its function, they are typically towed or in the case of aircraft, mounted away from the aircraft's body). They are more effective against submarines at a shallow depth, due to their short range, and can be confused by wrecks or uncharted masses of ore.
Electronic Warfare suites
There are whole books written on this topic, but for the purposes of this article, this is basically warships listening for enemy radars or broadcasting jamming to confuse enemy sensors. This can allow you to detect enemy ships long before they can pick you up on radar (by its very nature, to get a radar return, the signal needs to go from the transmitter to the target and back; the emitter has to have enough power to send signals double its maximum range). If your own emitters are turned off, you can then track them without needing your own radar. You can use common civilian radars to fool the enemy into thinking you are a merchant vessel. EW plays a key role in defense against ASCMs; detecting the missile's radar seeker may provide you more warning than your own radars, and you may be able to jam its seeker and confuse it. Most modern combatants mount some sort of EW system.
A jammer is similar to a radar, but instead of sending out a signal and listening for echoes, it blasts electromagnetic "noise" over the frequencies used by enemy sensors in order to generate false targets, make the range to target impossible to determine, or simply drown out all echoes and effectively "blind" the enemy radar. This does make it much harder for the enemy to target you, but does also make it rather obvious that there is a warship or warplane in the area, as civilian vessels don't carry jammers, so it's not a great idea to use them if stealth is important.
Radio Direction Finders
These simply tell you which direction a radio signal is coming from. By using several of them on different vessels, and then comparing what direction they see the signal coming from, you can triangulate the position of the transmitter, without using your own radar.
One way to avoid getting hit by missiles is to avoid being detected at all. New warships are now being designed so that their radar-cross sectionnote is reduced, making it harder to detect them initially and then harder for missiles to lock on. This started in the US in the 1980s but the practice has now become commonplace around the world. Generally it involves eliminating right angles, using radar-absorbent composite materials, and clearing away or concealing objects sticking out on deck and on the sides of the ship. This also has the added benefit of making the ships look more sleek, deadly and futuristic without all that ungainly, random crap like radars, antennas and deck fixtures sticking out.
- For an example of the progression stealth ship design has undergone, examine the shapes of five US warships from the last 30 years:
- The ''Spruance'' Class destroyers◊ were built in the 1970s and 80s, before the advent of stealth features for ships. Note the slab-sided superstructure with right angles everywhere.
- The ''Ticonderoga'' Class cruisers◊ were originally designed without stealth design (and use the same hull as the Spruance class), but some features were later added to improve it, such as radar absorbent material.
- The ''Arleigh Burke'' Class destroyers◊ were the first US ships built from the beginning to be stealthier; note the lack of prominent right angles and the major reduction of topside clutter. This is probably as stealthy as an air defense escort ship needs to be, since the aircraft carrier it's accompanying will inherently be about as stealthy as Mt Everest.
- The ''San Antonio'' class amphibious assault ships◊ represent the latest in stealth design; you can see how all most all of the antennas and protrusions topside are either missing or hidden inside the two large masts. Even the anchor is hidden from any angle a radar might see it from.
- And then we have the planned Zumwalt class◊ destroyers. Note the even more dramatic absence of protrusions and random clutter, turrets into which the gun barrels are retracted when not in use, and the unconventional hull shape which is much stealthier but also less stable in rough seas. This design may also someday include a railgun, which will need even more clever engineering to conceal.
- The French ''La Fayette''-class frigate was the codifier of the stealth ship concept, featuring a clean profile with angled, flush sides and construction from radar-absorbent composites.
Drawbacks to dedicated stealth designs include the high cost and lower resilience of dedicated composites, limited deck space and internal volume and, in the case of the Zumwalt, a hull form with a history of instability problems - all of which would conspire to make such ships very hard to upgrade. At the same time, modern integrated sensor networks are causing naval theorists to question the very notion that naval stealth is possible at all.
Countermeasures are systems that actively attempt to defeat or destroy enemy weapon systems.
Ballistic Missile Defense
Modern ballistic missiles are basically every defense planner's worst nightmare: they can be launched with little-to-no warning, fly hundreds-to-thousands of miles in a matter of minutes, and then deliver multiple nuclear weapons to different targets anywhere on the globe. Worse yet, it's impossible to know exactly where they're aimed at until they fire, at which point it is too late to move defensive assets into the path of the missile.
That last one is why in many ways, ships are ideal Ballistic Missile Defense (BMD) platforms. Thanks to international waters, they can move anywhere there's ocean, and unlike aircraft, they can loiter in good intercept position for months without requiring a base to return to.
To understand BMD, you need to know a little bit about how Ballistic Missiles operate. There are three phase of flight: Boost, Midcourse, and Terminal.
- In the Boost phase, the missile is taking off from its launcher and its rocket motor(s) is/are burning. It takes about 5-10 minutes depending on the range to target. The huge, hot exhaust plume makes it easy to detect and track, and it's at its most fragile during the stresses of acceleration. Unfortunately, to intercept a missile in boost phase, you need to be relatively close to the launch site, have a good idea of where the missile is heading, and have an interceptor system that can catch up to and overtake a missile which is literally rocketing upward and acclerating into space. Also, unless you expect a launch, you may not have sensors looking in the right direction to detect the launch until the missile is at higher altitude.
- In the Midcourse phase, the missile's motor has burned out and it is coasting on a ballistic arc towards its target. For ICBMs, this will be outside the atmosphere. During this phase the boost stages will drop off and if the missile has multiple warheads, they will separate and manuver to point towards their respective targets. Surface-based radars should be able to easily detect them now, and once they are being tracked it becomes relatively easy to figure out where they are headed. This is the longest phase, giving a defender the most chances to intecept them. The hard part about intercepting in midcourse is that most missile designers today include decoys with their warheads that make it very difficult to tell which are real warheads and hit them, and again, the warheads are moving very, very fast.
- During the Terminal phase, the warheads have re-entered the atmosphere and are screaming out of sky nearly direcly on top of their targets. The decoys are now gone, slowed by the atmosphere while the denser warheads fall through. This is the shortest phase, lasting about 30-60 seconds. It ends when the warhead detonates on or above its target. The obvious disadvantage of a terminal BMD system is that you have to be near the target, and you have maybe one chance to intercept every incoming warhead before you are converted into radioactive ash. You'd better hope your missiles are fast and your aim is good.
Most ships are best suited to perform midcourse BMD, which would allow them to cover a broader area and take advantage of their existing systems To do this, a ship would need radars capable of seeing into space, missiles capable of reaching that high in a very short time, and a guidance system capable of "hitting a bullet with a bullet", as both the interceptor missile and the ballistic missile or its warheads will be moving in different directions at thousands of miles per hour.
This is a very new warfare area, so feel free to post new examples as they are invented. Or don't, if keeping such things a secret are important to you.
- The US is attempting to turn its CGs and DDGs equipped with Aegis into BMD ships using a version of the Standard family of missiles; it appears to be the most successful system so far. In fact, the RIM-161 Standard Missile 3 is also more successful than any known land-based BMD weapon as well, to the extent that Japan, Poland and Romania are deploying them on land (which is now known as "Aegis Ashore").
Exactly What It Says on the Tin. Warships carry flare launchers to decoy IR Guided (heat-seeking) missiles by creating a heat source hotter than the ship's exhaust. Ideally, the missiles go after the flares and not the ship.
Chaff consists of thousands of small strips of metal which are fired into the air in a "cloud" to decoy radar-guided missiles in a similar manner to flares. They create a large swarm of false targets and/or a single large, false target for the missile to home in on. The British proved that these work during The Falklands War, though they also demonstrated that you should be careful where exactly you fire these off; in at least one case an incoming missile was fooled by the chaff launched by destroyers, flew through it, and then acquired the next target it found on the other side, which turned out to be a merchant converted into a cargo transport by the British. Whoops.
Active radar decoys
These work by flying out away from a ship and then turning on a radar repeater which imitates the signals from a radar-guided misile and hopefully causes it to believe there's a bigger ship where there actually isn't. These are generally more effective than chaff but are generally much more expensive and can get as big as small missiles, so a ship will usually have fewer of them if it has any at all.
- The joint US-Austrailian built NULKA is one of these.
These are decoys either fired underwater or towed behind a ship or submarine whose job it is to fool torpedoes into either going the wrong way or detonating early. Some are noisemakers which imitate the sound of a legitimate target, some are essentially "jammers" which flood the water with sound to confuse sonar, some form a "screen" of bubbles to try and provide active sonar with a bigger target than the submarine/surface ship, and finally some generate a magnetic field intended to fool a torpedo's detonator into thinking its found the target. Some incorporate more than one method.
- The US AN/SLQ-25 "Nixie" is one of these.
Other things that make warships better
Navies have been individually arming sailors since navies were invented. During the Age of Sail, boarding actions carried out by crewman with axes, cutlasses, and pistols were an important means of winning battles. While the invention of accurate long-range guns ended the days of daring boarding actions, most ships have a team of specially-trained sailors for boarding (ostensibly) unarmed vessels and for in-port security. As well as occasionally at-sea security, as seen on the night of October 7, 2009 when Somali pirates boarded what they mistook for a civilian tanker but was actually a French Navy command ship. And on January 12, 2012 when they did it again, this time to a Spanish Navy replenishment ship. Boarding teams are usually at least as well-armed as the average infantryman on land and will typically have nifty things like ballistic vests that are also flotation devices, rope ladders with hooks and poles for getting up the side of ships, and tools for cutting through metal doors. Their weapons are generally more compact so as to be easier to maneuver inside cramped ships.