A submarine is a specialized watercraft that can operate
underwater at very high pressures beyond the range of unaided human
survivability. Submarines, first widely used in World War I, are used by
all major navies today, especially the American, Russian and British
navies. Civilian submarines and submersibles are used for marine and
freshwater science and for work at depths too great for human divers.
Submarines are always referred to as "boats" except in some formal documents. The term U-Boat is sometimes used for German submarines in English. This comes from the German word for submarine, U-Boot, itself an abbreviation for Unterseeboot (“undersea boat”).
Submarines encompass one of the largest ranges in capabilities of any
vessel. They range from small one- or two-man vessels that can examine
the sea floor for a few hours to the Russian Typhoon class, which can
remain submerged for half a year and carry nuclear missiles capable of
destroying multiple cities. There are also specialized submarines such
as rescue submarines (like the Deep Submergence Rescue Vehicle (DSRV) or
Priz-class) and tiny one-person human powered subs intended for
competitions between universities. An older device for use in underwater
exploration, salvage, construction and rescue is the diving bell.
The word “submarine” was originally an adjective meaning "under the
sea." Some firms who make diving gear—but not parts for
submarines—called their work "submarine engineering." “Submarine” as a
noun—meaning a submersible craft—originated as short for "submarine
boat" and older books such as Jules Verne’s Twenty Thousand Leagues Under the Sea always use this term.
Civilian submarines and submersibles
Civilian submarines are usually much smaller than military submarines.
Tourist submarines work mainly in tropical resort areas or other areas
with clear water and good visibility. By 1996 there were over 50 private
submarines operating around the world, serving approximately two
million passengers a year. Most of them carried between 25 and 50
passengers at a time and sometimes made ten or more dives per day. In
design, these submarines borrow mainly from research subs, having large
portholes for viewing and often placing significant mechanical systems
outside the hull to conserve interior space. Nonetheless, even aboard
tourist submarines the seating can be rather cramped. They are mainly
battery-powered and very slow.
As of January 2005, the largest tourist submarine in use was the Atlantis XIV based out of Waikiki beach. The largest Atlantis-class
submarine of its fleet, launched in 1994, can carry 64 passengers and
three crew (two guides and a pilot) to 150 feet (50 meters) deep off the
shores of the island of O'ahu in Hawaii. There, tourists can view a
great number of ocean specimens living around artificial reefs.
In common usage, "submarine" means a ship that operates above and below
the surface, untethered. Underwater vessels with limited mobility,
intended to remain in one place during most of their use, such as those
used for rescue, research or salvage purposes are usually called
"submersibles." Submersibles are typically transported to their area of
operation by surface ships or large submarines and have a very short
range. Many submersibles operate on a "tether" or "umbilical," remaining
connected to a tender (a submarine, surface vessel or platform).
Bathyspheres are submersibles that lack self-propulsion and are used for
very deep diving. A predecessor of the bathysphere, the diving bell,
consisted of a chamber with an open bottom, lowered into the water.
Bathyscaphes are self-propelled deep-diving submersibles reliant on a
mother ship on the surface.
A fairly recent development, very small, unmanned submersibles called
"marine remotely operated vehicles" (MROVs) are widely used today to
work in water too deep or too dangerous for divers. For example,
remotely operated vehicles (ROVs) repair offshore petroleum platforms
and attach cables to sunken ships to hoist them. A thick cable providing
power and communications tethers these remotely operated vehicles to a
control center on a ship. Operators on the ship see video images sent
back from the robot and may control its propellers and manipulator arm.
The wreck of the RMS Titanic was explored by such a vehicle, as well as by a manned vessel.
Private individuals have designed, built and operated submarines for
recreational use. One example is the K-250 submersible designed by
George Kittredge. It is a one-person, 2.5 ton, 1-ATM, dry submarine
rated for a maximum depth of 250 feet. Claus Noerregaard and Peter
Madsen from Copenhagen, Denmark have successfully built a larger
diesel-electric submarine named Kraka and operated it in the Baltic Sea. Kraka
is 42 feet long and displaces six tons. This submarine, based largely
on military concepts, is one of very few seagoing privately built
submarines. Built for coastal waters, Kraka is rated for a maximum diving depth of 120 feet.
Military submarines
There are more military submarines in operation than civilian ones.
Submarines are useful militarily because they are difficult to locate
and difficult to destroy when deep below the surface. A great deal of
attention in the design of a submarine is devoted to making it travel
through the water as silently as possible in order to prevent its
detection. Sound travels underwater much more easily than light does.
Since the atoms in water are closer together than the atoms of gaseous
matter, the vibrations of sound travel more easily through water than
air, which means that a submarine's sound is the feature most likely to
allow its detection. Some submarines conceal their sound so well that
they actually create a silent area in their environment, which can be
detected if it blocks other ambient sounds. If a submarine remains
undetected, it is able to strike at close range.
Submersion and navigation
All surface ships, as well as surfaced submarines, are in positively
buoyant condition, weighing less than the water of their volume would.
To submerge hydrostatically, a ship must gain negative buoyancy, either
increasing its own weight or decreasing displacement of the water. To
control their weight, submarines are equipped with ballast tanks, which
can be filled with either outside water or pressurized air.
For general submersion or surfacing, submarines use the forward and aft
tanks, called main ballast tanks (MBTs), which are opened and completely
filled with water to submerge, or filled by pressurized air to surface.
Under submerged conditions, MBTs generally always stay flooded, which
simplifies their design; on many submarines these tanks are simply a
section of interhull space. For more precise and quick control of depth,
submarines use smaller depth control tanks or DCTs, also called “hard
tanks” due to their ability to withstand higher pressure. The amount of
water in depth control tanks can be controlled either to reflect changes
in outside conditions or change submersion depth. Depth control tanks
can be located either near the submarine's center of gravity, or
separated along the submarine body to prevent affecting trim.
When submerged, the water pressure on submarine's hull can reach 4 MPa
for steel submarines and up to 10 MPa for titanium submarines like
Soviet Komsomolets, while the pressure inside stays the same. This
difference results in hull compression, which decreases displacement.
Water density increases as the salinity and pressure are higher, but
this does not compensate for hull compression, so buoyancy falls with
depth. A submerged submarine is in an unstable equilibrium, having a
tendency to either fall down to the ocean floor or float up to the
surface. Keeping a constant depth requires continual operation of either
the depth control tanks or control surfaces.
Submarines in a neutral buoyancy condition are not intrinsically stable
in trim. To sustain desired trim, submarines use specialized forward and
aft trim tanks. Pumps can move water between these tanks, changing the
weight distribution and therefore creating a moment to turn the sub
upwards or downwards. A similar system is sometimes used to maintain
stability.
The hydrostatic effect of variable ballast tanks is not the only way to
control the submarine underwater. Hydrodynamic maneuvering is done by
several surfaces, which can be turned to create corresponding
hydrodynamic forces when a submarine moves at sufficient speed. The
stern planes, located near the propeller and normally oriented
horizontally, serve the same purpose as the trim tanks, controlling the
trim, and are commonly used, while other control surfaces may not be
present on many submarines. The fairwater planes on the sail and/or bow
planes on the main body, both also horizontal, are located closer to the
center of gravity, and are used to control depth with less effect on
the trim.
When a submarine performs an emergency surfacing, all depth and trim
methods are used simultaneously, together with propelling the boat
upwards. Such surfacing is very quick, so the sub may even partially
jump out of the water, but it inflicts serious damage on some submarine
systems, primarily pipes.
Modern submarines use an inertial guidance system for navigation while
submerged, but drift error unavoidably builds up over time. To counter
this, the global positioning system will occasionally be used to obtain
an accurate position. The periscope—a retractable tube with prisms
allowing a view to the surface—is only used occasionally in modern
submarines, since the range of visibility is short. The Virginia-class
submarines have "photonics masts" rather than hull-penetrating optical
tube periscopes. These masts must still be hoisted above the surface,
and employ electronic sensors for visible light, infrared, laser
range-finding, and electromagnetic surveillance.
Submarine hull
Modern submarines are usually cigar-shaped. This design, already visible
on very early submarines (see below) is called a "teardrop hull," and
was patterned after the bodies of whales. It significantly reduces the
hydrodynamic drag on the sub when submerged, but decreases the
sea-keeping capabilities and increases the drag while surfaced. Since
the limitations of the propulsion systems of early military submarines
forced them to operate on the surface most of the time, their hull
designs were a compromise. Because of the slow submerged speeds of those
boats—usually well below 10 knots (18 kilometers per hour)—the
increased drag for underwater travel was considered acceptable. Only
late in World War II—when technology allowed faster and longer submerged
operations and increased surveillance by enemy aircraft forced
submarines to stay submerged—did hull designs become teardrop shaped
again, to reduce drag and noise. On modern military submarines the outer
hull is covered with a thick layer of special sound-absorbing rubber,
or anechoic plating, to make the submarine quieter.
A raised tower on top of a submarine accommodates the length of the
periscope and electronics masts, which can include radio, radar,
electronic warfare, and other systems. In many early classes of
submarines (see history), the Control Room, or "Conn," was located
inside this tower, which was known as the "conning tower." Since that
time, however, the “Conn” has been located within the hull of the
submarine, and the tower is more commonly called the "sail" today. The
“Conn” should not be confused with the "bridge," which is a small, open
platform set into the top of the sail used for visual observation while
operating on the surface. There may also be an additional closed
platform below this with windows and wipers for bad weather.
Double hull
All small modern submarines and submersibles, as well as the oldest
ones, have a single hull. Large submarines generally have an additional
hull or hull sections outside. This external hull, which actually forms
the shape of submarine, is called the outer hull or light hull, as it
does not have to hold any pressure difference. Inside the outer hull
there is a strong hull, or pressure hull, which withstands sea pressure
and has normal atmospheric pressure inside.
As early as World War I, it was realized that the optimal shape for
withstanding pressure conflicted with the optimal shape for
seaworthiness and minimized water resistance, and construction
difficulties further complicated the problem. This was solved either by a
compromise shape, or by using two hulls; internal for holding pressure,
and external for optimal shape. Until the end of World War II, most
submarines had an additional partial cover on the top, bow and stern,
built of thinner metal, which was flooded when submerged. Germany went
further with the Type XXI, the general predecessor of modern submarines,
in which the pressure hull was fully enclosed inside the light hull,
but optimized for submerged navigation, unlike earlier designs.
After World War II, approaches split. The Soviet Union changed its
designs, basing them on the latest German developments. All post-World
War II heavy Soviet and Russian submarines are built with a double hull
structure. American and most other Western submarines retain a
single-hull approach. They still have light hull sections in the bow and
stern, which house main ballast tanks and provide a hydrodynamically
optimized shape, but the main cylindrical hull section has only a single
plating layer.
Despite being no longer needed for different shapes, the double-hull
approach still has a number of advantages. The ring stiffeners and
longitudinals are located between hulls, and the light hull can also be
used to mount certain equipment that does not require constant pressure
to operate, while attaching it directly to the pressure hull could cause
dangerous local stress. These measures save a lot of space inside the
pressure hull, which is much heavier and takes longer to build than the
light hull. In case the submarine is damaged, the light hull can take
most of the damage, which does not compromise the boat's integrity, as
long as the strong hull is intact. A light hull can also be acoustically
decoupled from the pressure hull, which significantly reduces noise
from internal equipment, improves stealth or allows the use of a simpler
internal layout and equipment mounting.
The major downside of double-hull structure is the significantly greater
amount of manual work required to construct it. The Soviet Union had
implemented the requisite welding technology earlier and had enough
cheap, qualified workers available, but the high cost of manual labor in
the United States made the less expensive single-hull approach
preferable. Another reason for double-hull construction in the Soviet
Union was operation under the Arctic Ocean, where submarines had to
break thick ice to launch their missiles, which could damage the hull.
However, the double-hull approach is today being considered for future
submarines in the United States as a means to improve payload capacity,
stealth and operational reach.
Pressure hull
The pressure hull is generally constructed of thick high-strength steel
with a complex structure and high strength reserve, and is separated
with watertight bulkheads into several compartments. There are also
examples of more than two hulls in a submarine, like the Typhoon-class,
which has two main pressure hulls and three smaller ones for control
room, torpedoes and steering gear, while the missile launch system is
located between the main hulls.
The dive depth cannot be increased easily. Simply making the hull
thicker increases the weight and requires reduction of the weight of
onboard equipment, ultimately resulting in a bathyscaphe. This is
affordable for civilian research submersibles, but not military
submarines, so their dive depth was always bound by current technology.
World War I-era submarines had their hulls built of carbon steel, and
could not submerge below 100 meters. During World War II, high-strength
alloyed steel was introduced, allowing for dive depths of up to 200
meters. High-strength alloyed steel is still the main material for
submarines today, with a 250-400 meter depth limit, which cannot be
exceeded on a military submarine without sacrificing other
characteristics. To exceed that limit, a few submarines were built with
titanium hulls. Titanium is almost as strong as steel, but lighter, and
is also not ferromagnetic, which is important for stealth. Titanium
submarines were favored by the Soviet Union, which developed specialized
high-strength alloys and built an industry capable of producing
titanium at an affordable cost. It has produced several types of
titanium submarines. Titanium alloys allow a major increase in depth,
but other systems need to be redesigned to cope, so test depth was
limited to one thousand meters for K-278 Komsomolets, the deepest-diving
military submarine. An Alfa-class submarine may have
successfully operated at 1,300 meters, though continuous operation at
such depths would be an excessive stress for many submarine systems.
Despite its benefits, the high cost of titanium construction led to the
abandonment of titanium submarine construction as the Cold War ended.
The task of building a pressure hull is very difficult, as it must
withstand a force of several million tons. When the hull is perfectly
round in cross-section, the pressure is evenly distributed, and causes
only hull compression. If the shape is not perfect, the hull is bent,
with several points heavily strained. Inevitable minor deviations are
resisted by the stiffener rings, but even a one-inch (25-millimeter)
deviation from roundness results in over 30 percent decrease of maximal
hydrostatic load and consequently dive depth. The hull must therefore be
constructed with very high precision. All hull parts must be welded
without defects, and all joints are checked several times using
different methods. This contributes to the very high cost of modern
submarines (for example, each Virginia-class attack submarine costs $2.6 billion, over $200,000 per ton of displacement).
Propulsion
The first mechanically driven submarine was the 1863 French Plongeur, which used compressed air for propulsion, and anaerobic propulsion was first employed by the Spanish Ictineo II in 1864. Ictineo's
engine used a chemical mix containing a peroxide compound to generate
heat for steam propulsion while also providing oxygen for the crew. The
system was not employed again until 1940 when the German Navy tested a
system employing the same principles, the Walter turbine, on the
experimental V-80 submarine and later on the naval U-791 submarine.
Until the advent of nuclear marine propulsion]], most twentieth-century
submarines used batteries for running underwater and gasoline (petrol)
or diesel engines on the surface and to recharge the batteries. Early
submarines used gasoline, but this quickly gave way to paraffin, then
diesel, because of reduced flammability. Diesel-electric became the
standard means of propulsion. The diesel or gasoline engine and the
electric motor, separated by clutches, were initially on the same shaft
and drove the propeller. This allowed the engine to drive the electric
motor as a generator to recharge the batteries and also propel the
submarine if required. The clutch between the motor and the engine would
be disengaged when the submarine dove so that the motor could be used
to turn the propeller. The motor could have more than one armature on
the shaft—these would be electrically coupled in series for slow speed
and in parallel for high speed (known as "group down" and "group up,"
respectively).
The principle was modified for some submarine designs in the 1930s,
particularly those of the U.S. Navy and the British “U”-class
submarines. The engine was no longer attached to the motor/propeller
drive shaft, but drove a separate generator to drive the motors on the
surface while recharging the batteries. This diesel-electric propulsion
allowed much more flexibility; for example, the submarine could travel
slowly while the engines were running at full power to recharge the
batteries as quickly as possible, reducing time spent on the surface, or
use its snorkel. It was then possible to insulate the noisy diesel
engines from the pressure hull, making the submarine quieter.
Other power sources were attempted. Oil-fired steam turbines powered the
British "K"-class submarines built during the First World War and in
the following years, but these were not very successful. This was
selected to give them the necessary surface speed to keep up with the
British battle fleet. German Type XXI submarines attempted the
application of hydrogen peroxide to provide long-term, fast
air-independent propulsion, but were ultimately built with very large
batteries instead.
At the end of the Second World War, the British and Russians
experimented with hydrogen peroxide/kerosene (paraffin) engines which
could be used both above and below the surface. The results were not
encouraging enough for this technique to be adopted at the time, and
although the Russians deployed a class of submarines with this engine
type (codenamed Quebec by NATO), they were considered unsuccessful.
Today several navies, notably Sweden, use air-independent propulsion
boats which substitute liquid oxygen for hydrogen peroxide. A newer
development in air-independent propulsion is the use of hydrogen fuel
cells, first applied in series on the German Type 212 submarine, with
nine 34-kilowatt or two 120-kilowatt cells.
Steam power was resurrected in the 1950s with the advent of the
nuclear-powered steam turbine driving a generator. By removing the
requirement for atmospheric oxygen, these submarines can remain
submerged indefinitely (air is recycled and fresh water is distilled
from seawater). These vessels always have a small battery and diesel
engine and generator installation for emergency use if the reactors have
to be shut down.
Nuclear power is now used in all large submarines, but due to the high
cost and large size of nuclear reactors, smaller submarines still use
diesel-electric propulsion. The ratio of larger to smaller submarines
depends on strategic needs; for instance, the U.S. Navy operates only
nuclear submarines, which is usually explained by the need for overseas
operations. Other major operators rely on a mix of nuclear submarines
for strategic purposes and diesel-electric submarines for defensive
needs. Most fleets have no nuclear submarines at all, due to the limited
availability of nuclear power and submarine technology. Commercial
submarines usually rely only on batteries, as they are never expected to
operate independently of a mother ship.
Toward the end of the twentieth century, some submarines, such as the British Vanguard-class,
began to be fitted with pump-jet propulsors instead of propellers.
Although these are heavier, more expensive, and less efficient than a
propeller, they are significantly quieter, giving an important tactical
advantage.
A possible propulsion system for submarines is the magnetohydrodynamic
drive, or "caterpillar drive," which has no moving parts. It was
popularized in the movie version of The Hunt for Red October,
written by Tom Clancy, which portrayed it as a virtually silent system
(in the book, a form of propulsor was used rather than an MHD). Although
some experimental surface ships have been built with this propulsion
system, speeds have not been as high as expected. In addition, the noise
created by bubbles, and the higher power settings that a submarine's
reactor would need, mean that it is unlikely to be considered for any
military purpose.
Crew
With nuclear power, submarines can remain submerged for months at a
time. Diesel submarines must periodically resurface or snorkel to
recharge their batteries. Most modern military submarines are able to
generate oxygen for their crew by electrolysis of water. Atmosphere
control equipment includes a CO2 scrubber, which uses a catalyst to
remove the gas from air and diffuse it into waste pumped overboard. A
machine that uses a catalyst to convert carbon monoxide into carbon
dioxide (removed by the CO2 scrubber) and bonds hydrogen produced from
the ship's storage battery with oxygen in the atmosphere to produce
water, also found its use. An atmosphere monitoring system samples the
air from different areas of the ship for nitrogen, oxygen, hydrogen, R12
and R114 refrigerant, carbon dioxide, carbon monoxide, and others.
Poisonous gases are removed, and oxygen is replenished by use of an
oxygen bank located in a main ballast tank. Some heavier submarines have
two oxygen bleed stations (forward and aft). The oxygen in the air is
sometimes kept a few percent less than atmospheric concentration to
reduce fire danger.
Fresh water is produced by either an evaporator or a reverse osmosis
unit. It is used for showers, sinks, cooking and cleaning. Seawater is
used to flush toilets, and the resulting "black water" is stored in a
sanitary tank until it is blown overboard using pressurized air or
pumped overboard by using a special sanitary pump. The method for
blowing sanitaries overboard is difficult to operate, and the German
Type VIIC boat U-1206 was lost with casualties because of a mistake with
the toilet. Water from showers and sinks is stored separately in "gray
water" tanks, which are pumped overboard using the drain pump.
Trash on modern large submarines is usually disposed of using a tube
called a trash disposal unit (TDU), where it is compacted into a
galvanized steel can. At the bottom of the TDU is a large ball valve. An
ice plug is set on top of the ball valve to protect it, the cans on top
of the ice plug. The top breech door is shut, and the TDU is flooded
and equalized with sea pressure, the ball valve is opened and the cans
fall out to the ocean floor assisted by scrap iron weights inside the
cans.
A typical nuclear submarine has a crew of over 120; non-nuclear boats
typically have less than half as many. The conditions on a submarine can
be difficult because crewmembers must work in isolation for long
periods of time, without contact with their families. Submarines
normally maintain radio silence to avoid detection. Operating a
submarine is dangerous, even in peacetime, and many submarines have been
lost in accidents.
Women on submarines
In 1995 the Royal Norwegian Navy became the first navy in the world to
appoint a female submarine captain. In 1998, the Royal Australian Navy
(RAN) became the second nation to allow women to serve on combat
submarines. Canada and Spain followed in permitting women to serve on
military submarines. The usual reasons for barring women that are given
are lack of privacy and "hot bunking" or "hot racking," a common
practice on submarines where three sailors share two bunks on a rotating
basis to save space. The U.S. Navy, which permits women to serve on
almost every other ship in the fleet, only allows three exceptions for
women being on board military submarines: (1) Female civilian
technicians for a few days at most; (2) Women midshipmen on an overnight
during summer training for both Navy ROTC and Naval Academy; (3) Family
members for one-day dependent cruises. The U.S. Navy argues it would
cost $300,000 per bunk to permit women to serve on submarines versus
$4,000 per bunk to allow women to serve on aircraft carriers. However,
this calculation is based on the assumption of semi segregation of the
female crew, possibly to the extent of structural redesign of the
vessel.
Types of military submarines
Military submarines are generally divided into attack submarines,
designed to operate against enemy ships—including other submarines—in a
hunter-killer role, or strategic ballistic-missile submarines, designed
to launch attacks on land-based targets from a position of stealth, also
known as "boomers" in the United States Navy or "bombers" in the Royal
Navy. The division between these classes refers to role rather than
construction, and submarines designed to destroy enemy fleets from long
distances with multiple nuclear missiles are similar to
ballistic-missile boats in size, armament and other facilities.
Every known strategic, ballistic-missile carrying submarine (SSBN)
operated today is nuclear powered. In regard to tactical nuclear
weapons, it is widely rumored that Israel tested nuclear-capable cruise
missiles from two German-built Dolphin-class submarines in May 2000; if so, these are likely to be operational today.
U.S. attack submarines no longer carry nuclear-tipped Tomahawk cruise
missiles as a result of nuclear arms control agreements. Some older, Trident-class
ballistic missile submarines are being converted to carry multiple
conventional-warhead, "guided" Tomahawk missiles and thus become
redesignated as guided-missile submarines. The Russian Federation also
possesses several nuclear-powered submarines capable of launching
SS-N-19 anti-ship cruise missiles. NATO forces designate these craft as
SSGN submarines as well.
Attack submarines may be divided in two general types: nuclear (what the
U.S. calls a fast-attack submarine; SSN) or diesel-electric (SS).
Nuclear powered submarines are faster and larger, and have more
firepower and longer mission endurance than diesel-electrics. Depending
on the submarine's overall mission, the diesel-electric submarine is
sometimes more suited for shallow water or littoral operations. To close
the gap between the two very different designs several navies have
started the development of air-independent propulsion boats, which are
used like diesel-electric submarines with an enlarged diving period.
Various specialized military submarines have also been developed in the
past. In World War II, the Japanese used submarines such as its
I-400-class as platforms to launch attack seaplanes. The Germans built
their Type XIV Milchkuh submarines to serve as supply vessels for
other submarines. Midget submarines were used for sabotage and
espionage, especially by the Japanese and British navies; five were used
by Japan in its attack on Pearl Harbor. During the early years of the
Cold War, radar-picket submarines such as the USS Triton were developed to provide radar coverage and direct aircraft operations at long distances ahead of other units.
Ballistic missile submarines
Ballistic missile submarines (SSBNs; boomers in
American slang) carry submarine-launched ballistic missiles (SLBM) with
nuclear warheads for attacking strategic targets such as cities or
missile silos anywhere in the world. They are currently universally
nuclear-powered, to provide the greatest stealth and endurance. They
played an important part in Cold War mutual deterrence, as both the
United States and the Soviet Union had the credible ability to conduct a
retaliatory strike against the other nation in the event of a first
strike. This was an important element of the strategy of mutual assured
destruction.
The U.S. built 18 Ohio-class submarines as SSBNs, each capable of carrying 24 Trident SLBMs. The first four Ohio-class vessels are now being converted to carry Tomahawk guided missiles; the remaining 14 carry Trident II missiles.
The Royal Navy possess a single class of four ballistic missile submarines, the Vanguard-class. The Royal Navy's previous ballistic missile submarine class was the Resolution-class, which also consisted of four boats. The Resolutions, named after battleships to convey the fact they were the new capital ships, were decommissioned when the Vanguards entered service in the 1990s.
France operates a force de frappe including a nuclear ballistic submarine fleet made up of one SSBN of the Redoutable-class and three SSBNs of the Triomphant-class. One additional SSBN of the Triomphant class is under construction.
The People's Republic of China's People's Liberation Army Navy's SLBM
inventory is relatively new. China launched its first nuclear-armed
submarine in April 1981. The PLAN currently has one Xia-class ("Type 92") at roughly 8,000 tons displacement. The Type 92 is equipped with 12 SLBM launching tubes.
Attack boats
Submarines designed for the purpose of attacking merchant ships or other
warships are known as "fast attacks," "hunter-killers," "fast boats,"
or "fleet submarines" (which terms are not synonyms; each is a different
design for a different mission). They typically carry torpedoes for
attacking naval vessels, and today carry cruise missiles for attacking
either land-based targets or shipping. On American submarines, cruise
missiles can be fired horizontally through a submarine's torpedo tubes,
or, on newer vessels, via specially designed vertical launch tubes. The
former has an effect of reducing the available torpedoes a submarine can
carry, while the latter requires it to be reloaded by a submarine
tender or by returning to port. The Soviet Navy also developed several
types of missile attack submarines (SSGNs) which carried a heavy load of
anti-surface missiles, as their primary targets were U.S. aircraft
carriers.
Attack submarines can use a wide variety of propulsion systems. The
majority of non-nuclear submarines use the same diesel-electric
combination developed early in the twentieth century; heavier types use
nuclear power, and a small but growing number use fuel cells in addition
to diesel-electric or some other form of air-independent propulsion
such as Stirling engines. All of the attack submarines of the United
States use nuclear power.
Until the 1980s, Soviet attack submarines were designed around the
concept of anti-surface warfare so they tended to be fast and noisy. Due
primarily to a U.S. sailor and communications technician who spied for
the Soviet Union, John Anthony Walker, the Soviet Union learned NATO
naval forces could track them quite easily and over time redesigned
their submarines to operate much more quietly, and redeployed them into
defensive bastions. The Victor III was the first class of Soviet
submarines to be built with this new capability; armed with torpedoes,
tactical short-range nuclear missiles and cruise missiles, they posed a
more significant threat to NATO sea power. Today Russian Akula- (Shark), Sierra- and Graney-class submarines continue in design innovation and are respected as some of the finest submarines in the world.
Just before the 1990s, the Royal Navy consisted of diesel and nuclear
powered submarines but, due to the end of the Cold War, financial cuts
saw the submarine fleet became all-nuclear, presently consisting of the Swiftsure and Trafalgar
classes of submarines. The boats are armed with torpedoes, Harpoon
anti-ship missiles and, in many cases, Tomahawk cruise missiles, all are
fired from their torpedo tubes. The Royal Navy intends to have all of
its attack submarines armed with the Tomahawk by 2008. The Astute-class
submarine is expected to replace older submarines in the Royal Navy,
but delays have seen the expected launch of the first boat, HMS Astute, moved to 2009.
The role of all these attack boats has changed considerably since the
end of the Cold War. U.S. fast boats no longer prowl the deep oceans in
the hunt for elusive Soviet SSBNs; instead, they provide cruise missile
support, early warning and intelligence gathering, harbor mine clearing,
Special Operation Warfare team delivery, and others. The Virginia-class was specifically designed with this multiple-mission capability in mind.
History of submarines
Early history of submarines and the first submersibles
A far ancestor for a submarine is probably a seventeenth-century Ukrainian Cossack riverboat called Chaika (gull) that was used underwater for reconnaissance and infiltration missions. Chaika
could be easily capsized and submerged so that the crew was able to
breathe underneath like in a modern diving bell and propel the vessel by
walking on the bottom of river. Special plummets for submerging and
pipes for additional breathing were used.
The first submersible with reliable information on its construction was
built in 1620 by Cornelius Jacobszoon Drebbel, a Dutchman in the service
of James I. It was propelled by means of oars. The precise nature of
the submarine type is a matter of some controversy; some claim that it
was merely a bell towed by a boat. Two improved types were tested in the
Thames between 1620 and 1624.
Though the first submersible vehicles were tools for exploring under
water, it did not take long for inventors to recognize their military
potential. The strategic advantages of submarines were set out by Bishop
John Wilkins of Chester in Mathematicall Magick in 1648.
- Tis private: a man may thus go to any coast in the world invisibly, without discovery or prevented in his journey.
- Tis safe, from the uncertainty of Tides, and the violence of Tempests, which do never move the sea above five or six paces deep. From Pirates and Robbers which do so infest other voyages; from ice and great frost, which do so much endanger the passages towards the Poles.
- It may be of great advantages against a Navy of enemies, who by this may be undermined in the water and blown up.
- It may be of special use for the relief of any place besieged by water, to convey unto them invisible supplies; and so likewise for the surprisal of any place that is accessible by water.
- It may be of unspeakable benefit for submarine experiments.
The first military submarine was Turtle (1775), a hand-powered egg-shaped device designed by the American David Bushnell, to accommodate a single man. It was the first verified submarine capable of independent underwater operation and movement, and the first to use screws for propulsion. During the American Revolutionary War, Turtle (operated by Sgt. Ezra Lee, Continental Army) tried and failed to sink a British warship, HMS Eagle (flagship of the blockaders) in New York harbor on September 7, 1776.
In 1800, France built a human-powered submarine designed by Robert Fulton, the Nautilus. The French eventually gave up with the experiment in 1804, as did the British when they later considered Fulton's submarine design.
During the War of 1812, in 1814, Silas Halsey lost his life while using a submarine in an unsuccessful attack on a British warship stationed in New London harbor.
In 1851, a Bavarian artillery corporal, Wilhelm Bauer, took a submarine designed by him called the Brandtaucher (incendiary-diver) to sea in Kiel Harbor. This submarine was built by August Howaldt and powered by a treadwheel. It sank but the crew of three managed to escape. The submarine was raised in 1887 and is on display in a museum in Dresden.
Submarines in the American Civil War
During the American Civil War, the Union was the first to field a submarine. The French-designed USS Alligator was the first U.S. Navy sub and the first to feature compressed air (for air supply) and an air filtration system. It was the first submarine to carry a diver lock which allowed a diver to plant electrically detonated mines on enemy ships. Initially hand-powered by oars, the boat was converted to a screw propeller powered by a hand crank after six months. With a crew of 20, she was larger than Confederate submarines. Alligator was 47 feet (14.3 meters) long and about 4 feet (1.2 meters) in diameter. She was lost in a storm off Cape Hatteras on April 1, 1863 while uncrewed and under tow to her first combat deployment at Charleston.
The Confederate States of America fielded several human-powered submarines including H. L. Hunley (named for one of her financiers, Horace Lawson Hunley). The first Confederate submarine was the 30-foot long Pioneer which sank a target schooner using a towed mine during tests on Lake Pontchartrain but was not used in combat. Pioneer was scuttled after New Orleans was captured and was sold for scrap in 1868.
Hunley was intended for attacking Union ships that were blockading the South's seaports. The submarine had a long pole with an explosive charge in the bow, called a spar torpedo. The sub had to approach an enemy vessel, attach the explosive, move away, and then detonate it. It was extremely hazardous to operate, and had no air supply other than what was contained inside the main compartment. On two occasions, the boat sank; on the first occasion half the crew died and on the second, the entire eight-man crew (including Hunley himself) drowned. On February 18, 1864 Hunley sank USS Housatonic off the Charleston Harbor, the first time a submarine successfully sank another ship, though Hunley sank in the same engagement shortly after signaling her success. Another Confederate submarine was lost on her maiden voyage in Lake Pontchartrain; the boat was found washed ashore in the 1870s and is now on display at the Louisiana State Museum. Submarines did not have a major impact on the outcome of the war, but did portend their coming importance to naval warfare and increased interest in their use in naval warfare.
Mechanically-powered submarines (late nineteenth century)
The first submarine that did not rely on human power for propulsion was the French Navy submarine Plongeur, launched in 1863, and using compressed air at 180 pounds per square inch.
The first combustion-powered submarine was the steam and peroxide driven Ictineo II, launched in 1867 by NarcÃs Monturiol. It was originally launched in 1864 as a human-powered submarine, propelled by 16 men.
The 14-meter craft was designed to carry a crew of two, dive 30 meters (96 feet), and demonstrated dives of two hours. When on the surface it ran on a steam engine, but underwater such an engine would quickly consume the submarine's oxygen. So Monturiol turned to chemistry to invent an engine that ran on a reaction of potassium chlorate, zinc, and manganese peroxide. The beauty of this method was that the reaction which drove the screw released oxygen, which when treated was used in the hull for the crew and also fed an auxiliary steam engine that helped propel the craft under water. In spite of successful demonstrations in the Port of Barcelona, Monturiol was unable to interest the Spanish navy, or the navy of any other country.
In 1870 French writer Jules Verne published the science fiction classic 20,000 Leagues under the Sea, which concerns the adventures of a maverick inventor in Nautilus, a submarine more advanced than any that existed at that time. The Nautilus functioned "all by electricity." The story inspired inventors to build more advanced submarines.
In 1879, the Peruvian government, during the War of the Pacific, commissioned and built a submarine. The fully-operational Toro Submarino never saw military action and was scuttled to prevent its capture by the enemy. The first submarine built in series, however, was human-powered. It was the submarine of the Polish inventor Stefan Drzewiecki—50 units were built in 1881 for Russian government. In 1884 the same inventor built an electric-powered submarine.
Discussions between the English reverend, George Garrett, and the industrially and commercially adept Swede, Thorsten Nordenfelt, led to a series of steam powered submarines. The first was the Nordenfelt I, a 56-ton, 19.5 meter vessel similar to Garret's ill-fated Resurgam (1879), with a range of 240 kilometers and armed with a single torpedo in 1885. Like the Resurgam, it operated on the surface by steam and shut down its engine to dive. Greece, fearful of the return of the Ottomans, purchased it. Nordenfelt then built the Nordenfelt II (Abdülhamid) in 1886 and Nordenfelt III (Abdülmecid) in 1887, a pair of 30-meter submarines with twin torpedo tubes, for the Ottoman Navy. Abdülhamid became the first submarine in history to fire a torpedo while submerged under water. Nordenfelt's efforts culminated in 1887 with the Nordenfelt IV which had twin motors and twin torpedoes. It was sold to the Russians, but proved unstable, ran aground and was scrapped.
Another fully capable military submarine was the electrically-powered vessel built by the Spanish engineer and sailor, Isaac Peral, for the Spanish Navy. It was launched on September 8, 1888. It had two torpedoes, new air systems, a hull shape, propeller and cruciform external controls anticipating much later designs. Its underwater speed was ten knots, but it suffered from the short range and difficulty of recharging at sea of battery powered systems. In June 1890, Peral's submarine launched a torpedo while submerged under the sea. The Spanish Navy scrapped the project.
Another major submarine development was the French Gymnote, launched in 1888, often considered as the first fully functional modern submarine. The electrically-powered Gymnote completed two thosand dives successfully.
Many more submarines were built at this time by various inventors, but they were not to become effective weapons until the twentieth century.
Late nineteenth century to World War I
The turn of century era marked a pivotal time in the development of submarines, with a number of important technologies making their debut, as well as the widespread adoption and fielding of submarines by a number of nations. Diesel-electric propulsion would become the dominant power system and things such as the periscope would become standardized. Large numbers of experiments were done by countries on effective tactics and weapons for submarines, all of which would culminate in them making a large impact on coming World War I.
In 1895, Irish inventor John Philip Holland designed submarines that, for the first time, made use of internal combustion engine power on the surface and electric battery power for submerged operations. In 1902 Holland received U.S. Patent 708553. Some of his vessels were purchased by the United States, the United Kingdom, the Imperial Russian Navy, and Japan, and commissioned into their navies around 1900 (1905 for Japan, too late to serve in the war).
Commissioned in June 1900, the French steam and electric submarine Narval introduced the classic double-hull design, with a pressure hull inside the outer light hull. These 200-ton ships had a range of over 100 miles on the surface, and over 10 miles underwater. The French submarine Aigrette in 1904 further improved the concept by using a diesel rather than a gasoline engine for surface power. Large numbers of these submarines were built, with 76 completed before 1914.
Submarines during World War I
Military submarines first made a significant impact in World War I. Forces such as the U-boats of Germany saw action in the First Battle of the Atlantic, and were responsible for the sinking of the RMS Lusitania, which receives much of the credit for prompting the United States to enter the war.
The U-boats' ability to function as practical war machines relied on new tactics, their numbers, and submarine technologies such as combination diesel-electric power system that had been developed in the preceding years. More like submersible ships than the submarines of today, U-boats operated primarily on the surface using regular engines, submerging occasionally to attack under battery power. They were roughly triangular in cross-section, with a distinct keel to control rolling while surfaced, and a distinct bow.
In 1916, a Serbian pilot named Konjovic, flying with the Austro-Hungarian air service, bombed and sank the French submarine Foucault in the Adriatic Sea, thus becoming the first man to sink a submarine from the air. Spotting survivors in the water, he landed his flying boat and rescued them, an act for which the French government awarded him a special recognition in 1968.
Interwar developments
Various new submarine designs were developed during the interwar years. Among the most notorious ones were submarine aircraft carriers, equipped with waterproof hangar and steam catapult and which could launch and recover one or more small seaplanes. The submarine and her plane could then act as a reconnaissance unit ahead of the fleet, an essential role at a time when radar still did not exist. The first example was the British HMS M2, followed by the French Surcouf, and numerous aircraft-carrying submarines in the Imperial Japanese Navy. The 1929 Surcouf was also designed as an "underwater cruiser," intended to seek and engage in surface combat.
Submarines during World War II
Germany
Germany had the largest submarine fleet during World War II. Due to the Treaty of Versailles limiting the surface navy, the rebuilding of the German surface forces had only begun in earnest a year before the outbreak of World War II. Having no hope of defeating the vastly superior Royal Navy decisively in a surface battle, the German High Command immediately stopped all construction on capital surface ships save the nearly completed Bismarck-class battleships and two cruisers and switched the resources to submarines, which could be built more quickly. Though it took most of 1940 to expand the production facilities and get the mass production started, more than a thousand submarines were built by the end of the war.
Germany put submarines to devastating effect in the Second Battle of the Atlantic in World War II, attempting but ultimately failing to cut off Britain's supply routes by sinking more ships than Britain could replace. The supply lines were vital to Britain for food and industry, as well as armaments from the United States. Although the U-boats had been updated in the intervening years, the major innovation was improved communications, encrypted using the famous Enigma cipher machine. This allowed for mass-attack tactics or "wolf packs," (Rudel), but was also ultimately the U-boats' downfall.
After putting to sea, the U-boats operated mostly on their own trying to find convoys in areas assigned to them by the High Command. If a convoy was found, the submarine did not attack immediately, but shadowed the convoy to allow other submarines in the area to find the convoy. These were then grouped into a larger striking force and attacked the convoy simultaneously, preferably at night while surfaced.
From September 1939 to the beginning of 1943, the Uboatwaffe scored unprecedented success with these tactics, but were too few to have any decisive success. By the spring of 1943, German U-boat construction was at full capacity, but this was more than nullified by equally increased numbers of convoy escorts, aircraft, and technical advances like radar and sonar. Huff-Duff and Ultra allowed the Allies to route convoys around wolf packs when they detected them from their radio transmissions. The results of Allied efforts were devastating: from March to July of that year, over 130 U-boats were lost, one-third of which were lost in May alone (41 boats). Allied losses dropped dramatically in the same period, from 750,000 tons in March to only 188,000 in July. Although the Second Battle of the Atlantic would continue to the last day of the war, the U-boat arm was unable to stem the tide of men and material, paving the way for Operation Torch, Operation Husky, and ultimately, D-Day.
Winston Churchill wrote that the U-boat "peril" was the only thing that ever gave him cause to doubt the Allies' eventual victory.
Japan
Japan had the most varied fleet of submarines of World War II, including manned torpedoes (Kaiten manned torpedo), midget submarines (Ko-hyoteki-class, Kairyu-class), medium-range submarines, purpose-built supply submarines (many for use by the army), long-range fleet submarines (many of which carried an aircraft), submarines with the highest submerged speeds of the conflict (Sen taka I-200-class), and submarines that could carry multiple bombers (the war's largest submarine, the Sen toku I-400-class). These submarines were also equipped with the most advanced torpedo of the conflict, the oxygen-propelled Type 95. Overall, despite their technical prowess, Japanese submarines were relatively unsuccessful. They were often used in offensive roles against warships, which were fast, maneuverable and well-defended compared to merchant ships. In 1942 Japanese submarines sank two aircraft carriers among other warships, but were not able to sustain these results afterwards. By the end of the war, submarines were instead often used to transport supplies to island garrisons.
United States
The United States used its submarine force to attack merchant shipping (commerce raiding or guerre de course), its submarines destroying more Japanese shipping than all other weapons combined.
Where Japan had the finest submarine torpedoes of the war, the U.S. Navy had perhaps the worst. One attempt to correct the problems resulted in a wakeless, electric torpedo being placed in service, but the losses of two boats resulted from self-inflicted hits by these torpedoes, and contributed to a third before the boat was bombed by aircraft.
During World War II, 314 submarines served in the United States Navy. One hundred eleven boats were in commission on December 7, 1941, and 203 submarines from the Gato-, Balao- and Tench- classes were commissioned during the war. Fifty-two boats with 3,506 men were lost during hostilities. U.S. submarines sunk 1,392 enemy vessels of a total tonnage of 5.3 million tons, including eight aircraft carriers and over two hundred warships.
The Schnorchel
Diesel submarines need air to run their engines, and so carried very large batteries for submerged travel. These limited the speed and range of the submarines while submerged. The schnorchel (a prewar Dutch invention) was used to allow German submarines to run just under the surface, attempting to avoid detection visually and by radar. The German navy experimented with engines that would use hydrogen peroxide to allow diesel fuel to be used while submerged, but technical difficulties were great. The Allies experimented with a variety of detection systems, including chemical sensors to "smell" the exhaust of submarines.
Modern submarines
In the 1950s, nuclear power partially replaced diesel-electric propulsion. Equipment was also developed to extract oxygen from sea water. These two innovations gave submarines the ability to remain submerged for weeks or months, and enabled previously impossible voyages such as USS Nautilus' crossing of the North Pole beneath the Arctic ice cap in 1958 and the USS Triton's circumnavigation of the world in 1960. Most of the naval submarines built since that time in the United States and the Soviet Union/Russia have been powered by nuclear reactors. The limiting factors in submerged endurance for these vessels are food supply and crew morale in the space-limited submarine.
While the greater endurance and performance from nuclear reactors mean that nuclear submarines are better for long distance missions or the protection of a carrier battle-force, conventional diesel-electric submarines have continued to be produced by both nuclear and non-nuclear powers, as they can be made stealthier, except when required to run the diesel engine to recharge the ship’s battery. Technological advances in sound dampening, noise isolation and cancellation have substantially eroded this advantage. Though far less capable regarding speed and weapons payload, conventional submarines are also cheaper to build. The introduction of air-independent propulsion boats led to increased sales numbers of such types of submarines.
During the Cold War, the United States and the Soviet Union maintained large submarine fleets that engaged in cat-and-mouse games; this tradition today continues, on a much-reduced scale. The Soviet Union suffered the loss of at least four submarines during this period: K-129 was lost in 1968 (which the Central Intelligence Agency attempted to retrieve from the ocean floor with the Howard Hughes-designed ship named Glomar Explorer), K-8 in 1970, K-219 in 1986 (subject of the film Hostile Waters), and Komsomolets in 1989 (which held a depth record among military submarines—1000 meters). Many other Soviet subs, such as K-19 (the first Soviet nuclear submarine and the first Soviet sub to reach the North Pole) were badly damaged by fire or radiation leaks. The United States lost two nuclear submarines during this time: USS Thresher and USS Scorpion. Thresher was lost due to equipment failure, and the exact cause of the loss of Scorpion is not known, though is thought by many to have been a faulty torpedo.
The sinking of PNS Ghazi in the Indo-Pakistani War of 1971 was the first submarine casualty in the South Asian region. The United Kingdom employed nuclear-powered submarines against Argentina in 1982 during the Falklands War. The sinking of the cruiser General Belgrano by HMS Conqueror was the first sinking by a nuclear-powered submarine in wartime.
Major submarine incidents since 2000
Since submarines have been actively deployed, there have been several incidents involving submarines which were not part of major combat. Most of these incidents were during the Cold War, but some are more recent. Since 2000, there have been nine major naval incidents involving submarines. There were three Russian submarine incidents, in two of which the submarines in question were lost, along with three United States submarine incidents, one Chinese incident, one Canadian, and one Australian incident. In August 2005, the Russian Priz, an AS-28 rescue submarine was trapped by cables and/or nets off of Petropavlovsk, and saved when a British ROV cut them free in a massive international effort.
Submarine movies
A genre of submarine movies has developed. Submarines are popular subjects for films due to the danger, drama and claustrophobia of being on a submarine, and the suspense of the cat-and-mouse game of submarine or anti-submarine warfare. One of the first, based on a classic book, was Run Silent, Run Deep. Modern movies include The Hunt for Red October, Das Boot, U-571, Crimson Tide and The Enemy Below. K-19: The Widowmaker is about the first of many disasters that befell the Soviet submarine K-19. Operation Petticoat is a Cary Grant comedy from 1959 about a World War II submarine. Another comedy about a diesel submarine, Down Periscope, stars Kelsey Grammer.