HOME

TheInfoList



OR:

Marine propulsion is the mechanism or system used to generate
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
to move a
watercraft Any vehicle used in or on water as well as underwater, including boats, ships, hovercraft and submarines, is a watercraft, also known as a water vessel or waterborne vessel. A watercraft usually has a propulsive capability (whether by sail, ...
through water. While
paddle A paddle is a handheld tool with an elongated handle and a flat, widened distal end (i.e. the ''blade''), used as a lever to apply force onto the bladed end. It most commonly describes a completely handheld tool used to propel a human-powered w ...
s and sails are still used on some smaller
boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inl ...
s, most modern
ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...
s are propelled by mechanical systems consisting of an
electric motor An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagneti ...
or
internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
driving a
propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
, or less frequently, in
pump-jet A pump-jet, hydrojet, or water jet is a marine system that produces a jet of water for propulsion. The mechanical arrangement may be a ducted propeller ( axial-flow pump), a centrifugal pump, or a mixed flow pump which is a combination of bot ...
s, an
impeller An impeller or impellor is a rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid. In pumps An impeller is a rotating componen ...
.
Marine engineering Marine engineering is the engineering of boats, ships, submarines, and any other marine vessel. Here it is also taken to include the engineering of other ocean systems and structures – referred to in certain academic and professional circl ...
is the discipline concerned with the
engineering design process The engineering design process is a common series of steps that engineers use in creating functional products and processes. The process is highly iterative - parts of the process often need to be repeated many times before another can be entere ...
of marine
propulsion system Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...
s. Human-powered paddles and oars, and later, sails were the first forms of marine propulsion. Rowed
galley A galley is a type of ship that is propelled mainly by oars. The galley is characterized by its long, slender hull, shallow draft, and low freeboard (clearance between sea and gunwale). Virtually all types of galleys had sails that could be used ...
s, some equipped with sail, played an important early role in early human
seafaring Seamanship is the Art (skill), art, knowledge and Competence (human resources), competence of operating a ship, boat or other craft on water. The'' Oxford Dictionary of English, Oxford Dictionary'' states that seamanship is "The skill, techniques ...
and
warfare War is an intense armed conflict between states, governments, societies, or paramilitary groups such as mercenaries, insurgents, and militias. It is generally characterized by extreme violence, destruction, and mortality, using regular ...
s. The first advanced mechanical means of marine propulsion was the
marine steam engine A marine steam engine is a steam engine that is used to power a ship or boat. This article deals mainly with marine steam engines of the reciprocating type, which were in use from the inception of the steamboat in the early 19th century to their ...
, introduced in the early 19th century. During the 20th century it was replaced by
two-stroke A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...
or
four-stroke diesel engine A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directi ...
s,
outboard motor An outboard motor is a propulsion system for boats, consisting of a self-contained unit that includes engine, gearbox and propeller or jet drive, designed to be affixed to the outside of the transom. They are the most common motorised method ...
s, and
gas turbine engine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
s on faster ships. Marine nuclear reactors, which appeared in the 1950s, produce steam to propel
warship A warship or combatant ship is a naval ship that is built and primarily intended for naval warfare. Usually they belong to the armed forces of a state. As well as being armed, warships are designed to withstand damage and are usually faster a ...
s and
icebreaker An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller ...
s; commercial application, attempted late that decade, failed to catch on.
Electric motor An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagneti ...
s using
battery pack A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density. The term battery ...
s have been used for propulsion on
submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...
s and electric boats and have been proposed for energy-efficient propulsion.Development in
liquefied natural gas Liquefied natural gas (LNG) is natural gas (predominantly methane, CH4, with some mixture of ethane, C2H6) that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. It takes up about 1/600th the volu ...
(LNG) fueled engines are gaining recognition for their low emissions and cost advantages. Stirling engines, which are quieter, smoother running, propel a number of small submarines in order to run as quietly as possible. Its design is not used in civilian marine application due to lower total efficiency than internal combustion engines or power turbines.


History


Pre-mechanization

Until the application of the coal-fired
steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...
to ships in the early 19th century,
oars An oar is an implement used for water-borne propulsion. Oars have a flat blade at one end. Rowers grasp the oar at the other end. The difference between oars and paddles is that oars are used exclusively for rowing. In rowing the oar is connecte ...
or the
wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
were the principal means of watercraft propulsion. Merchant ships predominantly used sail, but during periods when
naval warfare Naval warfare is combat in and on the sea, the ocean, or any other battlespace involving a major body of water such as a large lake or wide river. Mankind has fought battles on the sea for more than 3,000 years. Even in the interior of large la ...
depended on ships closing to
ram Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...
or to fight hand-to-hand,
galley A galley is a type of ship that is propelled mainly by oars. The galley is characterized by its long, slender hull, shallow draft, and low freeboard (clearance between sea and gunwale). Virtually all types of galleys had sails that could be used ...
were preferred for their manoeuvrability and speed. The
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
navies that fought in the
Peloponnesian War The Peloponnesian War (431–404 BC) was an ancient Greek war fought between Athens and Sparta and their respective allies for the hegemony of the Greek world. The war remained undecided for a long time until the decisive intervention of th ...
used
trireme A trireme( ; derived from Latin: ''trirēmis'' "with three banks of oars"; cf. Greek ''triērēs'', literally "three-rower") was an ancient vessel and a type of galley that was used by the ancient maritime civilizations of the Mediterranean S ...
s, as did the
Romans Roman or Romans most often refers to: *Rome, the capital city of Italy * Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a lette ...
at the
Battle of Actium The Battle of Actium was a naval battle fought between a maritime fleet of Octavian led by Marcus Agrippa and the combined fleets of both Mark Antony and Cleopatra VII Philopator. The battle took place on 2 September 31 BC in the Ionian Sea, ...
. The development of
naval gunnery Naval artillery is artillery mounted on a warship, originally used only for naval warfare and then subsequently used for shore bombardment and anti-aircraft roles. The term generally refers to tube-launched projectile-firing weapons and excludes ...
from the 16th century onward vaulted broadside weight ahead of manoeuvrability; this led to the dominance of the sail-powered warship over the following three centuries. In modern times, human propulsion is found mainly on small boats or as auxiliary propulsion on sailboats. Human propulsion includes the push pole, rowing, and pedals. Propulsion by sail generally consists of a sail hoisted on an erect mast, supported by stays, and controlled by
lines Line most often refers to: * Line (geometry), object with zero thickness and curvature that stretches to infinity * Telephone line, a single-user circuit on a telephone communication system Line, lines, The Line, or LINE may also refer to: Arts ...
made of
rope A rope is a group of yarns, plies, fibres, or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than similarly ...
. Sails were the dominant form of commercial propulsion until the late nineteenth century, and continued to be used well into the twentieth century on routes where wind was assured and coal was not available, such as in the South American
nitrate trade Sodium nitrate is the chemical compound with the formula . This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordinary saltpeter, potassium nitrate. ...
. Sails are now generally used for recreation and racing, although innovative applications of
kite A kite is a tethered heavier than air flight, heavier-than-air or lighter-than-air craft with wing surfaces that react against the air to create Lift (force), lift and Drag (physics), drag forces. A kite consists of wings, tethers and anchors. ...
s/
royal Royal may refer to: People * Royal (name), a list of people with either the surname or given name * A member of a royal family Places United States * Royal, Arkansas, an unincorporated community * Royal, Illinois, a village * Royal, Iowa, a cit ...
s,
turbosail The turbosail or French is a marine propulsion system using a sail-like vertical surface and a powered boundary layer control system to improve lift across a wide angle of attack. This allows the sail to power the boat in any direction simply by ...
s, rotorsails,
wingsail A wingsail, twin-skin sail or double skin sail is a variable-camber aerodynamic structure that is fitted to a marine vessel in place of conventional sails. Wingsails are analogous to airplane wings, except that they are designed to provide lif ...
s,
windmills A windmill is a structure that converts wind power into rotational energy using vanes called sails or blades, specifically to mill grain (gristmills), but the term is also extended to windpumps, wind turbines, and other applications, in some par ...
and
SkySails SkySails Group GmbH is a Hamburg-based company that sells kite rigs to propel cargo ships, large yachts and fishing vessels by wind energy as well as airborne wind energy systems for electricity production from high-altitude winds. Busines ...
's own kite buoy-system have been used on larger modern vessels for fuel savings.


Mechanized

In the second half of the 20th century, rising fuel costs almost led to the demise of the steam turbine. Most new ships since about 1960 have been built with
diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...
s, both Four or two-Stroke. The last major passenger ship built with steam turbines was '' Fairsky'', launched in 1984. Similarly, many steam ships were re-engined to improve fuel efficiency. One high-profile example was the 1968 built '' Queen Elizabeth 2'' which had her steam turbines replaced with a diesel-electric propulsion plant in 1986. Most new-build ships with steam turbines are specialist vessels such as nuclear-powered vessels, and certain merchant vessels (notably
Liquefied Natural Gas Liquefied natural gas (LNG) is natural gas (predominantly methane, CH4, with some mixture of ethane, C2H6) that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. It takes up about 1/600th the volu ...
(LNG) and coal carriers) where the cargo can be used as
bunker fuel Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil, marine fuel oil (MFO), ...
.


Engines


Steam

Steam powers two types of engine, reciprocating (with steam driving pistons connected to a crankshaft) and turbine (with steam driving blades attached radially to a spinning shaft). The shaft power from each can either go directly to the propeller, pump jet or other mechanism, or it goes through some form of transmission; mechanical, electrical or hydraulic. In the 1800s, steam was one of the main power sources for marine propulsion. In 1869 there was a large influx of steam ships as the steam engine underwent large advancements during the time period.


Reciprocating

The development of piston-engined steamships was a complex process. Early steamships were fueled by wood, later ones by coal or fuel oil. Early ships used stern or side
paddle wheels A paddle wheel is a form of waterwheel or impeller in which a number of paddles are set around the periphery of the wheel. It has several uses, of which some are: * Very low-lift water pumping, such as flooding paddy fields at no more than about ...
, which gave way to screw
propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
s. The first commercial success accrued to
Robert Fulton Robert Fulton (November 14, 1765 – February 24, 1815) was an American engineer and inventor who is widely credited with developing the world's first commercially successful steamboat, the (also known as ''Clermont''). In 1807, that steamboat ...
's ''
North River Steamboat The ''North River Steamboat'' or ''North River'', colloquially known as the ''Clermont'', is widely regarded as the world's first vessel to demonstrate the viability of using steam propulsion for commercial water transportation. Built in 1807, t ...
'' (often called ''Clermont'') in US in 1807, followed in
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
by the of 1812. Steam propulsion progressed considerably over the rest of the 19th century. Notable developments include the steam
surface condenser A surface condenser is a water-cooled shell and tube heat exchanger installed to condense exhaust steam from a steam turbine in thermal power stations. These condensers are heat exchangers which convert steam from its gaseous to its liquid stat ...
, which eliminated the use of sea water in the ship's boilers. This, along with improvements in boiler technology, permitted higher steam pressures, and thus the use of higher efficiency multiple expansion (compound) engines. As the means of transmitting the engine's power, paddle wheels gave way to more efficient screw propellers. Multiple expansion steam engines became widespread in the late 19th century. These engines exhausted steam from a high pressure cylinder to a lower pressure cylinder, giving a large increase in efficiency.


Turbines

Steam turbines were fueled by
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...
or, later,
fuel oil Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil, marine fuel oil (MFO), bun ...
or
nuclear power Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced b ...
. The marine steam turbine developed by Sir
Charles Algernon Parsons Sir Charles Algernon Parsons, (13 June 1854 – 11 February 1931) was an Anglo-Irish engineer, best known for his invention of the compound steam turbine, and as the eponym of C. A. Parsons and Company. He worked as an engineer on d ...
raised the power-to-weight ratio. He achieved publicity by demonstrating it unofficially in the ''
Turbinia ''Turbinia'' was the first steam turbine-powered steamship. Built as an experimental vessel in 1894, and easily the fastest ship in the world at that time, ''Turbinia'' was demonstrated dramatically at the Spithead Navy Review in 1897 and set ...
'' at the
Spithead Spithead is an area of the Solent and a roadstead off Gilkicker Point in Hampshire, England. It is protected from all winds except those from the southeast. It receives its name from the Spit, a sandbank stretching south from the Hampshire ...
Naval Review A fleet review or naval review is an event where a gathering of ships from a particular navy is paraded and reviewed by an incumbent head of state and/or other official civilian and military dignitaries. A number of national navies continue to ...
in 1897. This facilitated a generation of high-speed liners in the first half of the 20th century, and rendered the reciprocating steam engine obsolete; first in warships, and later in merchant vessels. In the early 20th century, heavy fuel oil came into more general use and began to replace coal as the fuel of choice in steamships. Its great advantages were convenience, reduced manpower by removal of the need for trimmers and stokers, and reduced space needed for fuel bunkers.


=Nuclear-powered

= In these vessels, the
nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...
heats water to create steam to drive the turbines. When first developed, very low prices of diesel oil limited nuclear propulsion's commercial attraction. The advantages of its fuel-price security, greater safety and low emissions were unable to overcome the higher initial costs of a nuclear powerplant. In 2019, nuclear propulsion is rare except in some
Navy A navy, naval force, or maritime force is the branch of a nation's armed forces principally designated for naval warfare, naval and amphibious warfare; namely, lake-borne, riverine, littoral zone, littoral, or ocean-borne combat operations and ...
and specialist vessels such as
icebreaker An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller ...
s. In large
aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft. Typically, it is the capital ship of a fleet, as it allows a ...
s, the space formerly used for ship's bunkerage is used instead to bunker aviation fuel. In
submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...
s, the ability to run submerged at high speed and in relative quiet for long periods holds obvious advantages. A few naval
cruiser A cruiser is a type of warship. Modern cruisers are generally the largest ships in a fleet after aircraft carriers and amphibious assault ships, and can usually perform several roles. The term "cruiser", which has been in use for several hu ...
s have also employed nuclear power; as of 2006, the only ones remaining in service are the
Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
n . An example of a non-military ship with
nuclear marine propulsion Nuclear marine propulsion is propulsion of a ship or submarine with heat provided by a nuclear reactor. The power plant heats water to produce steam for a turbine used to turn the ship's propeller through a gearbox or through an electric generato ...
is the with . In an ice-breaker, an advantage is fuel security and safety in demanding arctic conditions. The commercial experiment of the ended before the dramatic fuel price increases of the 1970s. The Savannah also suffered from an inefficient design, being partly for passengers and partly for cargo. In recent times, there is some renewed interest in commercial nuclear shipping. Fuel oil prices are now much higher. Nuclear-powered cargo ships could lower costs associated with carbon dioxide emissions and travel at higher cruise speeds than conventional diesel powered vessels.


Diesel

Most modern ships use a reciprocating
diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...
as their prime mover, due to their operating simplicity, robustness and fuel economy compared to most other prime mover mechanisms. The rotating
crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...
can be directly coupled to the propeller with slow speed engines, via a reduction gearbox for medium and high speed engines, or via an alternator and electric motor in diesel-electric vessels. The rotation of the crankshaft is connected to the camshaft or a hydraulic pump on an intelligent diesel. The reciprocating marine diesel engine first came into use in 1903 when the
diesel electric Diesel may refer to: * Diesel engine, an internal combustion engine where ignition is caused by compression * Diesel fuel, a liquid fuel used in diesel engines * Diesel locomotive, a railway locomotive in which the prime mover is a diesel engin ...
rivertanker ''Vandal'' was put into service by Branobel. Diesel engines soon offered greater efficiency than the steam turbine, but for many years had an inferior power-to-space ratio. The advent of turbocharging however hastened their adoption, by permitting greater power densities. Diesel engines today are broadly classified according to *Their operating cycle:
two-stroke engine A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...
or
four-stroke engine A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directi ...
*Their construction: crosshead, trunk, or
opposed piston An opposed-piston engine is a piston engine in which each cylinder has a piston at both ends, and no cylinder head. Petrol and diesel opposed-piston engines have been used mostly in large-scale applications such as ships, military tanks, and ...
*Their speed **Slow speed: any engine with a maximum operating speed up to 300 
revolutions per minute Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
(rpm), although most large two-stroke slow speed diesel engines operate below 120 rpm. Some very long stroke engines have a maximum speed of around 80 rpm. The largest, most powerful engines in the world are slow speed, two stroke, crosshead diesels. **Medium speed: any engine with a maximum operating speed in the range 300–1000 rpm. Many modern four-stroke medium speed diesel engines have a maximum operating speed of around 500 rpm. **High speed: any engine with a maximum operating speed above 1000 rpm. Most modern larger merchant ships use either slow speed, two stroke, crosshead engines, or medium speed, four stroke, trunk engines. Some smaller vessels may use high speed diesel engines. The size of the different types of engines is an important factor in selecting what will be installed in a new ship. Slow speed two-stroke engines are much taller, but the footprint required is smaller than that needed for equivalently rated four-stroke medium speed diesel engines. As space above the waterline is at a premium in passenger ships and ferries (especially ones with a car deck), these ships tend to use multiple medium speed engines resulting in a longer, lower engine room than that needed for two-stroke diesel engines. Multiple engine installations also give redundancy in the event of mechanical failure of one or more engines, and the potential for greater efficiency over a wider range of operating conditions. As modern ships' propellers are at their most efficient at the operating speed of most slow speed diesel engines, ships with these engines do not generally need gearboxes. Usually such propulsion systems consist of either one or two propeller shafts each with its own direct drive engine. Ships propelled by medium or high speed diesel engines may have one or two (sometimes more) propellers, commonly with one or more engines driving each propeller shaft through a gearbox. Where more than one engine is geared to a single shaft, each engine will most likely drive through a clutch, allowing engines not being used to be disconnected from the gearbox while others keep running. This arrangement lets maintenance be carried out while under way, even far from port.


Gas turbines

Many warships built since the 1960s have used
gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
s for propulsion, as have a few passenger ships, like the
jetfoil The Boeing 929 Jetfoil are passenger-carrying, waterjet-propelled hydrofoils by Boeing. Boeing adapted many systems used in jet airplanes for hydrofoils. Robert Bateman led development. Boeing launched its first passenger-carrying waterjet-propell ...
. Gas turbines are commonly used in combination with other types of engine. Most recently, has had gas turbines installed in addition to diesel engines. Because of their poor thermal efficiency at low power (cruising) output, it is common for ships using them to have diesel engines for cruising, with gas turbines reserved for when higher speeds are needed. However, in the case of passenger ships the main reason for installing gas turbines has been to allow a reduction of emissions in sensitive environmental areas or while in port. Some warships, and a few modern cruise ships have also used steam turbines to improve the efficiency of their gas turbines in a combined cycle, where
waste heat Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...
from a gas turbine exhaust is utilized to boil water and create steam for driving a steam turbine. In such combined cycles, thermal efficiency can be the same or slightly greater than that of diesel engines alone; however, the grade of fuel needed for these gas turbines is far more costly than that needed for the diesel engines, so the running costs are still higher. Some private yachts, such as the Aga Khan's ''Alamshar'', also have gas turbine propulsion (Pratt and Whitney ST40M), which enables top speeds of up to 70 knots, which is unique for a 50-meter yacht.


LNG Engines

Shipping companies are required to comply with the
International Maritime Organization The International Maritime Organization (IMO, French: ''Organisation maritime internationale'') is a specialised agency of the United Nations responsible for regulating shipping. The IMO was established following agreement at a UN conference ...
(IMO) and the
International Convention for the Prevention of Pollution from Ships The International Convention for the Prevention of Pollution from Ships, 1973 as modified by the Protocol of 1978, or "MARPOL 73/78" is one of the most important international marine environmental conventions. MARPOL 73/78, MARPOL is an amalg ...
emissions rules. Dual fuel engines are fueled by either marine grade diesel, heavy fuel oil, or liquefied natural gas (LNG). A
Marine LNG Engine A marine LNG engine is a dual fuel engine that uses natural gas and bunker fuel to convert chemical energy in to mechanical energy. Due to natural gas’ cleaner burning properties, the use of natural gas in merchant ship propulsion plants is beco ...
has multiple fuel options, allowing vessels to transit without relying on one type of fuel. Studies show that LNG is the most efficient of fuels, although limited access to LNG fueling stations limits the production of such engines. Vessels providing services in the LNG industry have been retrofitted with dual-fuel engines, and have been proved to be extremely effective. Benefits of dual-fuel engines include fuel and operational flexibility, high efficiency, low emissions, and operational cost advantages. Liquefied natural gas engines offer the marine transportation industry with an environmentally friendly alternative to provide power to vessels. In 2010, STX Finland and Viking Line signed an agreement to begin construction on what would be the largest environmentally friendly cruise ferry. Construction of NB 1376 will be completed in 2013. According to Viking Line, vessel NB 1376 will primarily be fueled by liquefied natural gas. Vessel NB 1376 nitrogen oxide emissions will be almost zero, and sulphur oxide emissions will be at least 80% below the International Maritime Organization's (IMO) standards. Company profits from tax cuts and operational cost advantages has led to the gradual growth of LNG fuel use in engines.


Stirling

Since the late 1980s, Swedish shipbuilder
Kockums Saab Kockums AB is a shipyard headquartered in Malmö, Sweden, owned by the Swedish defence company Saab Group. Saab Kockums AB is further operational in Muskö, Docksta, and Karlskrona. While having a history of civil vessel construction, Koc ...
has built a number of successful Stirling engine powered submarines.Kockums (a) The submarines store compressed oxygen to allow more efficient and cleaner external fuel combustion when submerged, providing heat for the Stirling engine's operation. The engines are currently used on submarines of the and classes and the Japanese submarine. These are the first submarines to feature Stirling air-independent propulsion (AIP), which extends the underwater endurance from a few days to several weeks. The heat sink of a Stirling engine is typically the ambient air temperature. In the case of medium to high power Stirling engines, a radiator is generally required to transfer the heat from the engine to the ambient air. Stirling marine engines have the advantage of using the ambient temperature water. Placing the cooling radiator section in seawater rather than ambient air allows for the radiator to be smaller. The engine's cooling water may be used directly or indirectly for heating and cooling purposes of the ship. The Stirling engine has potential for surface-ship propulsion, as the engine's larger physical size is less of a concern.


Hydrogen Fuel

While currently not commonly used in the maritime industry, hydrogen as a fossil fuel alternative is an area with heavy investment. As of 2018 the shipping company Maersk has pledged to be carbon free by 2050, a goal they plan to achieve partly by investing in hydrogen fuel technology. While hydrogen is a promising fuel, it has a few disadvantages. Hydrogen is far more flammable than other fuels such as diesel, so precautions must be taken. It is also not very energy dense, so it has to be heavily compressed to increase its energy density enough for it to be practical, similar to methane and LNG. Hydrogen can have its power extracted either by use of a fuel cell system or it can be burned in an internal combustion engine, similar to the diesel engines presently used in the maritime industry.


Electric

Battery-electric propulsion first appeared in the latter part of the 19th century, powering small lake boats. These relied entirely on lead-acid batteries for electric current to power their propellers. Elco (the Electric Launch Company) evolved into the industry leader, later expanding into other forms of vessel, including the iconic World War II
PT boat A PT boat (short for patrol torpedo boat) was a motor torpedo boat used by the United States Navy in World War II. It was small, fast, and inexpensive to build, valued for its maneuverability and speed but hampered at the beginning of the wa ...
. In the early part of the 20th century electric propulsion was adapted to use in
submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...
s. As underwater propulsion driven exclusively by heavy batteries was both slow and of limited range and timespan, rechargeable battery banks were developed. Submarines were primarily powered by combined diesel-electric systems on the surface, which were much faster and allowed for dramatically expanded range, charging their battery systems as necessary for still limited subsurface action and duration. The experimental '' Holland V'' submarine led to the adoption of this system by the
U.S. Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage o ...
, followed by the
British Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against Fra ...
. To expand the range and duration of the submarine during World War II the German
Kriegsmarine The (, ) was the navy of Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war (1919–1935) of the Weimar Republic. The was one of three official branches, along with the a ...
developed a snorkel system, which allowed the diesel-electric system to be utilized while the submarine was all but completely submerged. Finally, in 1952, the USS ''Nautilus'' was launched, the world's first nuclear powered submarine, which eliminated the restrictions of both diesel fuel and limited duration battery propulsion. Several short-range ships are built as (or converted to) pure electric vessels. This includes some powered by batteries which are recharged from shore, and some shore-powered by
electrical cables Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure. Wiring is subject to safety standards for design and installation. Allowable ...
,
either ''Either/Or'' is an influential book by philosopher Søren Kierkegaard. Either/Or and related terms may also refer to: * ''Either/Or'' (book), a novel by Elif Batuman * ''Either/Or'' (album), music by Elliott Smith * ''Either/Or'' (TV series), a ...
overhead or submerged (no batteries). On November 12, 2017
Guangzhou Shipyard International CSSC Offshore & Marine Engineering (Group) Company Limited (COMEC), formerly Guangzhou Shipyard International Company Limited (GSI), is the largest modern integrated shipbuilding enterprise based in Southern China. It was founded in 1954 and is ...
(GSI) launched what may be the world's first all-electric, battery-powered inland coal carrier. The 2,000 dwt vessel will carry bulk cargo for up to 40 nautical miles per charge. The ship carries
lithium ion batteries A lithium-ion or Li-ion battery is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy. It is the predominant battery type used in portable consumer electronics and electric vehicles. It also see ...
rated at 2,400 kilowatt-hours, about the same amount as 30
Tesla Model S The Tesla Model S is a battery-powered liftback car serving as the flagship model of Tesla, Inc. The Model S features a dual-motor, all-wheel drive layout, although earlier versions of the Model S featured a rear-motor and rear-wheel drive ...
electric sedans.


Diesel-electric

The diesel-electric transmission of power from the engine to the propeller affords flexibility in distribution of machinery within the vessel at a higher first cost than direct-drive propulsion. It is a preferred solution for vessels that employ pod-mounted propellers for precision positioning or reducing general vibrations by highly flexible couplings. Diesel-electric provides flexibility to assign power output to applications on board, other than propulsion. The first diesel electric ship was the Russian tanker
Vandal The Vandals were a Germanic people who first inhabited what is now southern Poland. They established Vandal kingdoms on the Iberian Peninsula, Mediterranean islands, and North Africa in the fifth century. The Vandals migrated to the area betw ...
, launched in 1903.


Turbo-electric

Turbo-electric transmission A turbo-electric transmission uses electric generators to convert the mechanical energy of a turbine ( steam or gas) into electric energy, which then powers electric motors and converts back into mechanical energy that power the driveshafts. T ...
uses electric generators to convert the mechanical energy of a turbine (steam or gas) into electric energy and electric motors to convert it back into mechanical energy to power the driveshafts. An advantage of turbo-electric transmission is that it allows the combination of high-speed turbines with slow turning propellers or wheels, without requiring a heavy and complex gearbox. It has the advantage of being able to provide electricity for the ship or train's other electrical systems, such as lighting, computers, radar, and communications equipment.


Transmission of power

To transmit the rotational force of the shaft into thrust, propellers are most commonly used in today's merchant vessels. The developed thrust from the propeller is transferred to the hull via a thrust bearing.


Propulsion types

Numerous types of propulsion have been developed over time. These include:


Oars

One of the oldest forms of marine propulsion, oars have been found dating back to 5000-4500 BCE. Oars are used in rowing sports such as rowing, kayaking, canoeing.


Propeller

Marine propellers are also known as "screws". There are many variations of marine screw systems, including twin, contra-rotating, controllable-pitch, and nozzle-style screws. While smaller vessels tend to have a single screw, even very large ships such as tankers, container ships and bulk carriers may have single screws for reasons of fuel efficiency. Other vessels may have twin, triple or quadruple screws. Power is transmitted from the engine to the screw by way of a propeller shaft, which may be connected to a gearbox. The propeller then moves the vessel by creating thrust. When the propeller rotates the pressure in front of the propeller is lower than the pressure behind the propeller. The force from the pressure difference propels the propeller forward.


Paddle wheel

The paddle wheel is a large wheel, generally built of a
steel frame Steel frame is a building technique with a "skeleton frame" of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The developm ...
work, upon the outer edge of which are fitted numerous paddle blades (called ''floats'' or ''buckets''). The bottom quarter or so of the wheel travels underwater. Rotation of the paddle wheel produces
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
, forward or backward as required. More advanced paddle wheel designs have featured ''feathering'' methods that keep each paddle blade oriented closer to vertical while it is in the water; this increases efficiency. The upper part of a paddle wheel is normally enclosed in a paddle box to minimize splashing. Paddle wheels have been superseded by screws, which are a much more efficient form of propulsion. Nevertheless, paddle wheels have two advantages over screws, making them suitable for vessels in shallow rivers and constrained waters: first, they are less likely to be clogged by obstacles and debris; and secondly, when contra-rotating, they allow the vessel to spin around its own vertical axis. Some vessels had a single screw in addition to two paddle wheels, to gain the advantages of both types of propulsion.


Pump jet

A pump-jet, hydrojet, water jet, or jet drive uses a
ducted propeller A ducted propeller, also known as a Kort nozzle, is a marine propeller fitted with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily loaded propellers or propellers with limited dia ...
(
axial-flow pump An axial-flow pump, or AFP, is a common type of pump that essentially consists of a propeller (an axial impeller) in a pipe. The propeller can be driven directly by a sealed motor in the pipe or by electric motor or petrol/diesel engines mounted ...
),
centrifugal pump Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are a sub-class of dynamic ...
, or mixed flow pump to create a jet of water for propulsion. These incorporate an intake for source water and a nozzle to direct its flow out, generating momentum, and in most cases, employing thrust vectoring to steer the craft. Pump-jets are found on personal watercraft, shallow-draft river boats, and torpedoes.


Sail

The purpose of sails is to use
wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
to propel the vessel,
sled A sled, skid, sledge, or sleigh is a land vehicle that slides across a surface, usually of ice or snow. It is built with either a smooth underside or a separate body supported by two or more smooth, relatively narrow, longitudinal runners ...
, board,
vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wa ...
or
rotor Rotor may refer to: Science and technology Engineering *Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator * Helicopter rotor, the rotary wing(s) of a rotorcraft ...
. Depending on the angle of your sail it will be the difference in direction of where your boat is heading and where the wind is going. Dacron was used a lot as a material for sails because of its strong, durable, and easy to maintain. However, when it was being woven into it suffered from weaknesses. Nowadays laminated sails are used to combat sails becoming weak when woven into.


Voith-Schneider cyclo-rotor

A
Voith Schneider Propeller The Voith Schneider Propeller (VSP) is a specialized marine propulsion system (MPS) manufactured by the Voith Group based on a cyclorotor design. It is highly maneuverable, being able to change the direction of its thrust almost instantaneously ...
(VSP) is a practical
cyclorotor A cyclorotor, cycloidal rotor, cycloidal propeller or cyclogiro, is a fluid propulsion device that converts shaft power into the acceleration of a fluid using a rotating axis perpendicular to the direction of fluid motion. It uses several blades wi ...
that provides instant thrust in any direction. There is no need to turn a propulsor. Most ships with VSPs do not need or have a rudder. VSPs are often used in tugboats, drilling vessels, and other watercraft that require unusually good maneuverability. First deployed in the 1930s, Voith-Schneider drives are both reliable and available in large sizes.


Caterpillar

An early uncommon means of boat propulsion was the water caterpillar. This moved a series of paddles on chains along the bottom of the boat to propel it over the water and preceded the development of
tracked vehicle Continuous track is a system of vehicle propulsion used in tracked vehicles, running on a continuous band of treads or track plates driven by two or more wheels. The large surface area of the tracks distributes the weight of the vehicle b ...
s. The first water caterpillar was developed by Joseph-Philibert Desblanc in 1782 and propelled by a steam engine. In the United States the first water caterpillar was patented in 1839 by William Leavenworth of New York.


Oscillating flappers

In 1997, Gregory S. Ketterman patented a propulsion method of oscillating flappers driven by pedals. The Hobie company markets the propulsion method as the "MirageDrive pedal propulsion system" in its kayaks.


Buoyancy

Underwater gliders An underwater glider is a type of autonomous underwater vehicle (AUV) that employs variable-buoyancy propulsion instead of traditional propellers or thrusters. It employs variable buoyancy in a similar way to a profiling float, but unlike a floa ...
convert buoyancy to thrust, using wings, or more recently hull shape (SeaExplorer Glider). Buoyancy is made alternatively negative and positive, generating tooth-saw profiles.


See also

* * * * * * * * * *


References

{{DEFAULTSORT:Marine Propulsion