Underway replenishment
Encyclopedia
Underway replenishment (US Navy
) or replenishment at sea (RAS) (NATO/Commonwealth) is a method of transferring fuel, munitions, and stores from one ship to another while under way.
Prior to underway replenishment, coaling stations were the only way to refuel ships far from home. This however had two disadvantages: the competition between the colonial powers for suitable sites astride the world's trade routes, and the introduction of a predictable pattern to a nation's naval operations.
Following some early development starting at about 1900 for transferring coal, the technique of underway replenishment was perfected by the United States Navy
in the 1920s and 1930s, beginning with the supply ship and receiver ship coming along side each other at full stop in good sea states, but this was found impractical and methods were developed while ships were underway. And these methods developed were used extensively as a logistics support technique in the Pacific
theatre of World War II
. Since it allowed extended range and striking capability to naval task forces the technique was classified so that enemy nations could not duplicate it. Presently, most underway replenishments for the United States Navy are handled by the Military Sealift Command
. It is now used by most, if not all, blue-water navies
.
Germany used specialized submarines (so-called milk-cows
) to supply hunter U-boats in the Atlantic during World War II. However, these were relatively ponderous, required both submarines to be stationary on the surface, took a long time to transfer stores, and needed to be in radio contact with the replenished boat, all conspiring to make them rather easy targets. Due to this, those not sunk were soon retired from their supply role.
and speed, generally between 12 and 16 knots. The receiving ship then comes alongside the supplier at a distance of approximately 30 yards. A gunline, pneumatic line thrower, or shot line is fired from the supplier, which is used to pull across a messenger line. This line is used to pull across other equipment such as a distance line, phone line, and the transfer rig lines. As the command ship of the replenishment operation, the supply ship provides all lines and equipment needed for the transfer. Additionally, all commands are directed from the supply ship.
Because of the relative position of the ships, it is possible for some ships to set up multiple transfer rigs, allowing for faster transfer or the transfer of multiple types of stores. Additionally, many replenishment ships are set up to service two receivers at one time, with one being replenished on each side.
In the U.S. Navy, aircraft carrier
s are always replenished from the port side of the supply ship (the starboard side of the carrier). The design of an aircraft carrier, with its island/navigation bridge to starboard, does not permit replenishment from the carrier's port side. Most other ships can receive replenishment from either side of the supply vessel.
Alongside connected replenishment is a risky operation, as two or three ships running side-by-side at speed must hold to precisely the same course and speed for a long period of time. Moreover, the hydrodynamics of two ships running close together cause a suction between them. A slight steering error on the part of one of the ships could cause a collision, or part the transfer lines and fuel hoses. For this reason, experienced and qualified helmsmen are required during the replenishment, and the crew on the bridge
must give their undivided attention to the ship's course and speed. The risk is increased when a replenishment ship is servicing two ships at once.
In case of emergency, crews practice emergency breakaway procedures, where the ships will separate in less-than-optimal situations. Although the ships will be saved from collision, it is possible to lose stores, as the ships may not be able to finish the current transfer.
Following successful completion of replenishment, many US ships engage in the custom of playing a signature tune
over the replenished vessel's PA system
as they break away from the supplying vessel.
A third type of underway replenishment is vertical replenishment (VERTREP). In this method, a helicopter
lifts cargo from the supplying ship and lowers it to the receiving ship. The main advantage of this method is that the ships do not need to be close to each other, so there is little risk of collision; VERTREP is also used to supplement and speed stores transfer between ships conducting CONREP. However, the maximum load and transfer speeds are both limited by the capacity of the helicopter.
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
) or replenishment at sea (RAS) (NATO/Commonwealth) is a method of transferring fuel, munitions, and stores from one ship to another while under way.
History
Following some early development starting at about 1900 for transferring coal, the technique of underway replenishment was perfected by the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
in the 1920s and 1930s, beginning with the supply ship and receiver ship coming along side each other at full stop in good sea states, but this was found impractical and methods were developed while ships were underway. And these methods developed were used extensively as a logistics support technique in the Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
theatre of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. Since it allowed extended range and striking capability to naval task forces the technique was classified so that enemy nations could not duplicate it. Presently, most underway replenishments for the United States Navy are handled by the Military Sealift Command
Military Sealift Command
The Military Sealift Command is a United States Navy organization that controls most of the replenishment and military transport ships of the Navy. It first came into existence on 9 July 1949 when the Military Sea Transportation Service became solely responsible for the Department of Defense's...
. It is now used by most, if not all, blue-water navies
Blue-water navy
The term blue-water navy is a colloquialism used to describe a maritime force capable of operating across the deep waters of open oceans. While what actually constitutes such a force remains undefined, there is a requirement for the ability to exercise sea control at wide ranges...
.
Germany used specialized submarines (so-called milk-cows
German Type XIV submarine
The Type XIV U-boat was a modification of the Type IXD, designed to resupply other U-boats. They were nicknamed "Milchkuh/Milchkühe " . They had no torpedo tubes or deck guns, only anti-aircraft guns. Due to its large size, the Type XIV could resupply other boats with 400 tons of fuel, four...
) to supply hunter U-boats in the Atlantic during World War II. However, these were relatively ponderous, required both submarines to be stationary on the surface, took a long time to transfer stores, and needed to be in radio contact with the replenished boat, all conspiring to make them rather easy targets. Due to this, those not sunk were soon retired from their supply role.
Alongside connected replenishment
The alongside connected replenishment (CONREP) is a standard method of transferring liquids such as fuel and fresh water, along with ammunition and break bulk goods. The supplying ship holds a steady courseCourse (navigation)
In navigation, a vehicle's course is the angle that the intended path of the vehicle makes with a fixed reference object . Typically course is measured in degrees from 0° clockwise to 360° in compass convention . Course is customarily expressed in three digits, using preliminary zeros if needed,...
and speed, generally between 12 and 16 knots. The receiving ship then comes alongside the supplier at a distance of approximately 30 yards. A gunline, pneumatic line thrower, or shot line is fired from the supplier, which is used to pull across a messenger line. This line is used to pull across other equipment such as a distance line, phone line, and the transfer rig lines. As the command ship of the replenishment operation, the supply ship provides all lines and equipment needed for the transfer. Additionally, all commands are directed from the supply ship.
Because of the relative position of the ships, it is possible for some ships to set up multiple transfer rigs, allowing for faster transfer or the transfer of multiple types of stores. Additionally, many replenishment ships are set up to service two receivers at one time, with one being replenished on each side.
In the U.S. Navy, aircraft carrier
Aircraft carrier
An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations...
s are always replenished from the port side of the supply ship (the starboard side of the carrier). The design of an aircraft carrier, with its island/navigation bridge to starboard, does not permit replenishment from the carrier's port side. Most other ships can receive replenishment from either side of the supply vessel.
Alongside connected replenishment is a risky operation, as two or three ships running side-by-side at speed must hold to precisely the same course and speed for a long period of time. Moreover, the hydrodynamics of two ships running close together cause a suction between them. A slight steering error on the part of one of the ships could cause a collision, or part the transfer lines and fuel hoses. For this reason, experienced and qualified helmsmen are required during the replenishment, and the crew on the bridge
Bridge (ship)
The bridge of a ship is the room or platform from which the ship can be commanded. When a ship is underway the bridge is manned by an OOW aided usually by an AB acting as lookout...
must give their undivided attention to the ship's course and speed. The risk is increased when a replenishment ship is servicing two ships at once.
In case of emergency, crews practice emergency breakaway procedures, where the ships will separate in less-than-optimal situations. Although the ships will be saved from collision, it is possible to lose stores, as the ships may not be able to finish the current transfer.
Following successful completion of replenishment, many US ships engage in the custom of playing a signature tune
Breakaway music
Breakaway music is a modern U.S. Naval tradition used to motivate sailors upon the conclusion of underway replenishment UNREP, although using breakaway music is at the discretion of the Captain, and not all commands use it...
over the replenished vessel's PA system
1MC
1MC is the term for the shipboard public address circuits on naval vessels of the United States. This provides a means of transmitting general information and orders to all internal ship spaces and topside areas, and is loud enough that all embarked personnel are able to hear it...
as they break away from the supplying vessel.
Astern fueling
The earliest type of replenishment, rarely used today, is astern fueling. In this method, the receiving ship follows directly behind the supplying ship. The fuel-supplying ship throws a marker buoy into the sea and the receiving ship takes station with it. Then the delivering ship trails a hose in the water that the fuel-receiving ship retrieves and connects to. This method is more limited, as only one transfer rig can be set up. However, it is safer, as a slight course error will not cause a collision. The first underway refueling conducted by the US Navy was the astern replenishment of the destroyer by the oiler in 1921; further experiments with Cuyama and led the Navy to conclude that the rate of fuel transfer was too slow to be useful. This however was the method used by the Soviet navy for many decades after the end of World War II.Vertical replenishment
A third type of underway replenishment is vertical replenishment (VERTREP). In this method, a helicopter
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
lifts cargo from the supplying ship and lowers it to the receiving ship. The main advantage of this method is that the ships do not need to be close to each other, so there is little risk of collision; VERTREP is also used to supplement and speed stores transfer between ships conducting CONREP. However, the maximum load and transfer speeds are both limited by the capacity of the helicopter.
See also
- Replenishment oilerReplenishment OilerA replenishment oiler or fleet tanker is a naval auxiliary ship with fuel tanks and dry cargo holds, which can replenish other ships while underway in the high seas. Such ships are used by several countries around the world....
- Vertical replenishment
- Carrier onboard deliveryCarrier onboard deliveryCarrier Onboard Delivery is a military term used to describe type of aircraft which are able to ferry personnel, mail, and high-priority cargo on and off a naval ship .-History:...
- Aerial refuelingAerial refuelingAerial refueling, also called air refueling, in-flight refueling , air-to-air refueling or tanking, is the process of transferring fuel from one aircraft to another during flight....
- SeabasingSeabasingSeabasing is a naval capability that provides commanders with the ability to conduct selected functions and tasks at sea without reliance on infrastructure ashore. It describes the concepts and methods for sustaining large military forces during operations at large distances from traditional...
- Military Sealift CommandMilitary Sealift CommandThe Military Sealift Command is a United States Navy organization that controls most of the replenishment and military transport ships of the Navy. It first came into existence on 9 July 1949 when the Military Sea Transportation Service became solely responsible for the Department of Defense's...
- Military logisticsMilitary logisticsMilitary logistics is the discipline of planning and carrying out the movement and maintenance of military forces. In its most comprehensive sense, it is those aspects or military operations that deal with:...
External links
- Underway Replenishment (UNREP)
- Video footage of Underway Replenishment (Internet Archives : Prelinger Archive)