General
Information on Submarines
The
Submarine
A submarine is a self-propelled vessel capable of operating underwater.
(The broader term for devices designed for underwater operation is submersible.)
Submarines used in the two world wars could remain underwater only a
few hours at a time and had to function at the surface for long periods,
so they had sharply pointed bows and long, slender hulls. In contrast,
nuclear submarines (and various submersibles) designed for lengthy underwater
operation have a relatively broad tear shape or fish shape with bluntly
rounded bows and tapering sterns. Also, for stability, surface hulls
are broadest above the waterline, whereas underwater hulls have more
circular cross sections that increase strength and reduce surface area
and friction drag. (These design concerns do not apply to submersibles
such as diving bells). see
modern submersibles and tourist submarines
BASIC
SUBMARINE STRUCTURE
A
submarine is fundamentally an air space contained by a hull that is
designed to withstand deep ocean pressures and to move easily underwater.
The hull is a double steel shell. The inner, or pressure, hull contains
all the machinery for propelling and guiding the vessel, plus living
quarters for the crew. The outer hull holds the ballast tanks. When
the vessel submerges, these tanks are opened and flooded with seawater.
For surfacing, the seawater is forced out of the ballast tanks and replaced
by compressed air.
Submersion - Flooding
the ballast tanks is only one step in the process of submerging. The
submarine is also propelled downward by rear-mounted propellers that
force the craft forward, and by diving planes, which are movable horizontal
rudders that direct the angle of the dive. When the desired depth is
reached, the water level in the vessel's trim tanks is adjusted to keep
the craft stable.
Power Sources - Non-nuclear
submarines are propelled on the surface by diesel engines; when submerged,
propulsion is provided by electric batteries and motors. The batteries
must be recharged on the surface by the diesels after a short running
time. Nuclear submarines are powered by a shielded nuclear reactor that
generates steam to turn the propulsion turbines and also supplies electricity
for subsidiary systems such as lighting, the vent controls of the ballast
tanks, the operation of the torpedo tubes, the periscope, and the maintenance
of the life-support systems--the air and water supply that is manufactured
on board.
Nuclear
power generation is self-contained: because there is no combustion,
it does not draw oxygen from the vessel's air supply. In addition a
nuclear reactor can power a submarine for many thousands of kilometers
without refueling. Nuclear submarines therefore have a virtually unlimited
range.
Navigation - Until
after World War II, submerged submarines were navigated with a simple
magnetic compass, supplemented by periscopic sextant shots and observation
of the shoreline. Most periscopes could not be used at depths greater
than 9 m (30 ft). Improvements in gyroscopic navigational aids ultimately
led to the development of modern inertial navigation systems capable
of providing accurate guidance without the need for frequent external
"fixes" .
The Conning Tower - The fin-shaped superstructure mounted
on top of the submarine serves as a bridge when the vessel is on the
surface. It holds a number of instruments: the periscopes, the various
radio and radar antennas, and the snorkel, a system of air intake and
exhaust pipes. On nuclear submarines the conning tower is known as the
"sail" and carries a set of diving planes.
SUBMARINE
DEVELOPMENT - Submarines in History
The
first craft known to have maneuvered underwater was constructed by Cornelis
DREBBEL, court engineer to James I of England, and was demonstrated
on the Thames in 1620. Propelled by oars sealed at the locks by leather
gaskets, it apparently submerged by admitting water into the hull and
surfaced by pumping it out again.
Although
the idea of the submarine continued to intrigue inventors, the lack
of a power source to propel the vessel was a major obstacle to its development.
The wooden TURTLE, designed by David Bushnell, an American, was driven
by hand- and foot-cranked propellers. Its armament was an explosive
charge that, in theory, could be fastened to an enemy ship's hull. The
Turtle's one foray (1776), against a British ship lying off New York
Harbor, was frustrated in part by the difficulty of maneuvering the
vessel underwater.
David
Bushnell's Turtle - In 1801, Robert Fulton demonstrated his
three-man metal submarine, the NAUTILUS, for the French navy. Like the
Turtle, the Nautilus was driven by a hand-cranked propeller, but for
depth control it had movable horizontal surfaces--the diving planes
now used on all modern submarines. Its warhead was a towed contact mine,
designed to explode when it was dragged against the enemy target. The
military potential of the Nautilus was never realized in its time.
The first Nautilus submarine -
Submarines in the U.S. Civil War
- In response to the Northern blockade of shipping during the Civil
War, the Southern navy developed a group of semisubmersibles known as
"Davids" --small craft intended to battle the Union's Goliath
fleet. Although not true submersibles--their smokestacks and air intakes
were always above water--they were the first vessels to use submergence
with tactical success.
Another
Confederate development was the Hunley, a true submersible. Although
it used the old hand-cranked propeller system and was slower than the
"Davids," it could submerge completely. Fitted with a spar
torpedo--a 6-m (20-ft) pole tipped with an explosive charge--the Hunley
went down on the night of Feb. 17, 1864, sinking the U.S.S. Housatonic,
off Charleston but destroying itself in the process.
Drawing
of The Hunley - In 1863 the French inventor Charles Brun used
compressed air to propel his vessel, the Plongeur, and to expel water
from its ballast tanks, a method that is still used. The French navy
built several all-electric submarines in the 1880s and 1890s. These
demonstrated the potential of electric power underwater but were severely
limited by the need to recharge their battery-powered engines. Robert
Whitehead's self-propelled TORPEDO gave the submarine a genuine offensive
capability; the Swedish inventor Torsten Nordenfelt (1842-1920) developed
internal torpedo tubes for submarines in the 1880s.
The Holland - The Irish-American John P. Holland (1840-1914)
had experimented with submarine designs for a quarter century when he
sold (1900) the U.S. Navy its first submarine. The U.S.S. Holland used
an electric motor for propulsion underwater and a gasoline engine for
surface propulsion and for recharging the batteries. The submarines
of the two world wars differed in basic design from the Holland only
in the substitution of diesels for the gasoline engine. Like most later
submarines, the Holland submerged by flooding its ballast tanks, used
trim tanks and diving planes to control pitch when submerged, and fired
torpedoes and blew the ballast tanks empty with compressed air.
World War I
From the early years of the 20th century, fleets of submarines were
built by every major European power. The German vessels were the most
efficient; by 1911, German designers had abandoned both steam and gasoline--which
was volatile and therefore hazardous within the confines of a submarine--and
had equipped all their vessels with diesel engines. Also, German periscopes
were the best in the world.
German
U-Boat, WWI
World War I provided the first opportunity to use submarines as attack
vessels on a large scale. With its fleet of U-boats (Unterseebooten),
Germany came close to severing Britain's overseas lifelines. The British
countered with DEPTH CHARGES and hydrophones--underwater listening devices--and
with killer submarines--small antisubmarine vessels that could maintain
underwater speeds of up to 15 knots for as long as two hours. Finally,
merchant sailings were concentrated into large, well-escorted convoys,
a tactic for which the Germans had not found an answer by the war's
end.
World
War II
As
in World War I, Germany began World War II with a small but seasoned
submarine force and immediately applied it to isolate Britain from overseas
resources. Britain again replied with heavily escorted convoys, and
the Germans responded by sending U-boats out in large "wolf packs"
that searched and attacked in concert.
German
U-Boat, 1944
Tactical complexities multiplied: hydrophones were supplemented by underwater
sound-ranging systems (SONAR), and the use of RADAR and radar warning
devices became widespread. The Germans used long-range search aircraft
to coordinate the wolf packs; the British and Americans replied with
antisubmarine aircraft carriers and fleets of hunter-killer submarines
that were guided to the German vessels by sensitive direction-finding
radios installed aboard surface vessels.
American
submarines in the Pacific and British submarines in the Mediterranean
enjoyed the success denied the Germans in the Atlantic. Submarine destruction
of Axis supplies played a major role in the Allied victory in North
Africa. American submarines effectively halted Japanese maritime commerce
by mid-1944. Britain and Italy both had isolated but spectacular successes
with miniature one- and two-man submarines in port attacks on enemy
ships
THE
NUCLEAR SUBMARINE
The
first nuclear submarine, the U.S.S. NAUTILUS, launched in 1954, resembled
conventional submarines in many respects, but its great range both above
and below the surface made it a revolutionary and formidable weapon.
The Nautilus sailed almost 170,000 km (105,633 mi; 91,733 naut mi) before
refueling; 146,000 km (90,720 mi; 78,782 naut mi) were spent submerged.
On Aug. 3, 1958, it sailed under the Arctic ice and the North Pole.
Following
the Nautilus and a group of submarines of the same design, the U.S.
Navy developed the Skipjack class of nuclear submarine, which had a
teardrop-shaped hull design and was capable of reaching underwater speeds
of more than 30 knots. Succeeding nuclear submarines, the Thresher and
Sturgeon classes, were designed to be high-speed detection and attack
vessels. The U.S.S. Triton, launched in 1959, is among the largest and
is propelled by two nuclear reactors. In 1960 the Triton circumnavigated
the globe underwater, traveling 78,858 km (49,000 mi; 42,552 naut mi)
in 84 days.
The
nuclear BALLISTIC MISSILE submarine is perhaps the ultimate development
of the submarine's military potential, having the ability to launch
as many as several dozen intercontinental ballistic missiles while submerged.
Following the first underwater launch of a POLARIS missile from the
U.S.S. George Washington in 1960, such submarines entered the U.S. and
Soviet navies in increasing numbers, as well as those of Great Britain
and France. U.S. nuclear submarine classes include those carrying the
POSEIDON missile and a new fleet of TRIDENT submarines, first launched
in the early 1980s. The Soviet fleet, about 230 nuclear submarines,
is now shared by Russia and Ukraine.
With the end of the Cold War, the question of how to dispose of the
nuclear engines in aging submarines became paramount, especially for
the former Soviet fleet, many of whose vessels will be retired during
the decade of the 1990s
more
on historical submarines >
Ben Franklin deep submarine
