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Underway Replenishment

Underway Replenishment

 

AUTHOR LtCdr. Donald D. Hill, USN

 

CSC 1989

 

SUBJECT AREA - Logistics

 

 

 

EXECUTIVE SUMMARY

 

UNDERWAY REPLENISHMENT

 

Underway replenishment has always been recognized as

important, but took a back seat in development until it was

absolutely required. Research indicates that underway

replenishment dates back to the days of sail. Since then,

there have been four major periods in the development of

underway replenishment. The first was at the turn of the

century when coaling-at-sea was investigated. The second

was refueling-at-sea development. The third was underway

replenishment during World War II and the Korean War. The

final period was the late l95Os when the modern underway

replenishment concept was developed.

From the underway replenishment concept came the modern

underway replenishment ships and equipment. Underway

replenishment by these ships has evolved into a highly

efficient and reliable system that can replenish the naval

fleet day or night in all kinds of weather. This

replenishment is accomplished using single-product

replenishment ships (fleet oilers, combat stores ships, and

ammunition ships) and multi-product ships (fast combat

support ships and replenishment oilers). Each ship's

capabilities are taken into account when deciding what type

of ship is going to be used to handle fleet commitments.

There are not enough replenishment ships to handle all

the replenishment requirements that could occur during a

major crisis when much of the fleet would need support.

The Navy is looking at using various merchant tankers and

containerships to aid the Navy replenishment ships in fleet

support.

Underway replenishment has positive direction and

enjoys higher status than the past. New ships are being

built, new equipment is being developed, and new ship types

are being explored to carry underway replenishment into the

future.

 

 

UNDERWAY REPLENISHMENT

 

OUTLINE

 

Thesis Statement: The US Navy underway replenishment

 

program has come through the time of forced development to

 

an evolving doctrine that will adequately serve the fleet.

 

I. History of Underway Replenishment

 

A. Days of Sail

 

B. Coaling at Sea

 

C. Eearly Refueling/World War I

 

1. USS Maumee

 

2. Close-in fuel rig

 

D. World War II

 

E. Korean War

 

II. Modern Underway Replenishment Concept

 

A. Designed-For-Purpose UNREP Ships

 

B. Multi-Product UNREP Ships

 

III1. Cargo Transfer System

 

A. Connected Replenishment

 

1. STREAM

 

2. Rig configuration

 

B. Vertical Replenishment

 

IV. Fleet Replenishment

 

A. Battle Group Replenishment

 

B. Underway Replenishment Frequency

 

C. Underway Replenishment Ship Shuttle

 

D. Ship Requirements

 

 

E. Mini-Multi Concept

 

F. Merchant Augmentation

 

V. Future of Underway Replenishment

 

A. New Ships

 

B. New Equipment

 

 

UNDERWAY REPLENISHMENT

 

 

 

Underway replenishment for the US Navy has become a

 

routine, common occurrence for ships at sea. Everything

 

needed at sea can be transferred while underway; fuel,

 

food, ammunition, parts, personnel, and mail are

 

transferred. This reliable, fast transfer-at-sea has not

 

always been a navy luxury.

 

Underway replenishment has been required by the US

 

Navy since its earliest days. Underway replenishment has

 

been piecemeal, improvised, and lacking direction until

 

recent times. There is hope on the horizon, and the hard

 

lessons of the past have been learned. The US Navy

 

underway replenishment program has come through the time of

 

forced development to an evolving doctrine, that will

 

adequately serve the fleet.

 

The US Navy conduct of underway replenishment dates

 

back to the earliest years of the Navy. During the

 

Quasi-War with France (1799-1801) the young United States

 

traded only in the Caribbean. The neutral US shipping was

 

harassed by French warships and various privateers. The

 

Navy was sent to the area to defend US interests. (lO:159)

 

One particular ship squadron whose flag was USS

 

 

Constitution was assigned duty off Haiti. The slow down of

 

local privateering due to the presence of the US ships had

 

made the US warships not welcome in Haitian ports. These

 

were the closest ports for replenishment. The USS

 

Constitution and squadron had to stay on station to carry

 

out their mission and could not go off station as would be

 

required by going to other friendly ports to replenish food

 

and other items. The Navy Department chartered various

 

merchant vessels to rendezvous with the USS Constitution

 

squadron for resupply. The merchant would rendezvous with

 

a warship and be taken under tow. The stores would be

 

transferred by ship's boats. This setup allowed the

 

warships to stay on station. (10:161)

 

The US Navy also used the frigate USS John Adams with

 

reduced armament to shuttle men and supplies from the

 

Chesapeake to the Mediterranean during the war with

 

Tripoli. (6:78)

 

Sailing ship UNREPs pale in comparison to UNREP

 

requirements that were coming with the modern, mechanized

 

fleet. The first and foremost problem was one of fuel.

 

The early steam powered ships required large amounts of

 

coal to operate. The problem of ship coal replenishment

 

first arose during the Civil War. No method of coaling on

 

the open sea existed. At any one time, one-quarter of

 

Union ships on blockade duty were required to be off

 

station in a nearby friendly port filling their coal

 

 

bunkers. (16:157) While very inefficient, no alternatives

 

were offered

 

During the Spanish-American War large numbers of US

 

Navy steam-powered ships were required to fight outside the

 

continental shores. (12:2) To refuel these ships, merchant

 

colliers were procured. Coaling was done underway by

 

bringing the collier alongside the customer ship, placing

 

fenders in between, and lashing the ships together with

 

mooring line. Booms on the collier would transfer

 

the coal to the customer. (15:8) If the sea state became

 

too rough, the replenishment would have to stop until the

 

weather calmed, or the ships would have to move to a

 

sheltered anchorage and transfer the coal at anchor. While

 

on blockade duty off Santiago de Cuba, the weather was so

 

rough most of the time that ships had to go to Guantanamo

 

Bay to recoal. Again one-quarter of the fleet was off

 

station at any one time taking on coal. USA Massachusetts

 

and two other ships were 45 miles away recoaling in

 

Guantanamo Bay and completely useless when the Spanish

 

fleet came but of Santiago. (16:159-160)

 

The problems with coaling during the Spanish-American

 

War led to engineering research in coaling-at-sea mainly by

 

the engineer, Spencer Miller, Esq. He developed an under-

 

way coaling-at-sea system in 1904, but when tested, it

 

operated poorly. The next decade was spent redesigning and

 

refining this system. The revised system showed promise,

 

 

but the development was stopped. Coaling-at-sea had re-

 

ceived a bad name among naval officers from the 1904 expe-

 

rience, and with the emergence of fuel oil for navy

 

boilers, coaling-at-sea became a less critical

 

requirement. (13:76)

 

With the emergence of fuel oil as the fuel of choice,

 

the Navy built a diesel powered oiler the USS Maumee (AO 2)

 

in 1916. The oiler was designed to transfer fuel oil to

 

warships while at anchor. Small ships came alongside the

 

oiler, but the oiler went alongside the battleships. (18:10)

 

The USS Maumee's crew discussed and developed a plan

 

to refuel ships while underway, but had no opportunity to

 

test the plan. At the outbreak of World War I, USS Maumee

 

was sent to the mid-Atlantic 300 miles south of Greenland.

 

This location was a rendezvous position to refuel US

 

destroyers enroute to England who could not transit across

 

the Atlantic unless they refueled. The destroyers would

 

approach USS Maumee who would pass a 10-inch manila hawser

 

which was then secured to the destroyer. The destroyer

 

would slow to maintain good steering control-and a spacing

 

of about 50 feet would result. A four-inch fueling hose

 

was then passed to the destroyer and supported by a wooden

 

saddle suspended from cargo booms on the USS Maumee. The

 

hose was lead directly to the-destroyer's fueling bunker,

 

and fuel was pumped by USS Maumee. In addition to fuel,

 

stores and personnel could be transferred using the cargo

 

 

booms. The whole UNREP took about two hours per

 

destroyer. USS Maumee refueled 34 destroyers enroute to

 

Europe while on station approximately three months in

 

1917. (18:10-11)

 

This same system was used for Navy fuel UNREPs through

 

World War II. As ship rudder controls were made more

 

sensitive and reliable the 10-inch hawser was deleted, but

 

the rest of the procedure was unchanged. (18:12) (It is still

 

used today and is called the close-in fuel rig.) After

 

World War I refueling underway at sea was looked upon as an

 

emergency operation that may have to be resorted to in

 

wartime. It was a tolerated, annual exercise. (4:3)

 

World War II produced the great task of supporting the

 

fleet from the US west coast and Hawaii far out to the

 

operating areas in the Pacific. Floating logistic support

 

was the only alternative to this tremendous undertaking.

 

However, the depression had left the Navy lacking for

 

support craft of any kind, so they had to be made and

 

pressed into use after the war started.

 

Most Pacific World War II naval shipping was supplied

 

at anchor by small supply craft designed or built for

 

specific functions. As the fleet fought toward, Japan, the

 

logistic support also moved to forward bases on nearby

 

friendly islands or atolls. Merchant ships brought

 

supplies to the forward bases. Here they would deliver to

 

the small craft for resupplying ships at anchor, or they

 

 

would resupply the oilers of the Fast Attack Carrier

 

Forces. These oilers were the only ships to conduct actual

 

UNREPs during World War II, and then they conducted UNREPs

 

only with the aircraft carriers and escorts. They used the

 

method developed by USS Maumee. As the war progressed,

 

shipping increased to support the war, but at the end of

 

World War II, the majority of the large logistics Navy was

 

deactivated. It was theorized that all Pacific

 

requirements could be handled from Hawaii or CONUS. (6:78)

 

When the Korean War broke out in 1950, the US had very

 

few logistics ships to support the war. The ships

 

available were sent to Korea from all over the Pacific.

 

Ships from World War II were reactivated and loaded as

 

quickly as possible. The same jury rigged replenishment

 

methods used during World War II had to be employed.

 

While these methods may have worked-in World War II, they

 

were not sufficient to handle the tempo of operations off

 

Korea. Using merchant ships to rearm aircraft carriers was

 

found to be inefficient and unsafe. (13:76) Some slight

 

improvements were made as the war progressed, but new

 

problems appeared. (12:4-5)

 

The magnitude of problems that occurred during the

 

Korean War led the Chief of Naval Operations to call a

 

conference at San Francisco Naval Shipyard in 1952 which

 

put engineering back into UNREP for the first time since

 

1913. (12:5) One result of this meeting was a shipbuilding

 

 

program that produced the first "designed-for-purpose"

 

(12:5) UNREP ships. An oiler, a stores ship, and an

 

ammunition ship came out of this program. There existed a

 

major drawback with these new ships. The ships were larger

 

and faster than their World War II counterparts, but no

 

improvement had been made in the underway transfer

 

capability. (12:5) The UNREP method was still pre-World War

 

I.

 

A new UNREP concept started to emerge. In 1957, a

 

conference convened by the Chief of Naval Operations,

 

Admiral Arleigh Burke, "called for a new underway

 

replenishment system that minimized the time for UNREP and

 

could be conducted day or night in fair weather or foul."

 

(12:7) Out of this direction came the concept of a

 

multi-product UNREP ship. This concept allowed combatant

 

ships to go alongside one UNREP ship and get everything

 

needed in only one stop instead of having to go alongside

 

three single-product ships. Aircraft carrier replenishment

 

time was reduced from ten hours to three. (13:76)

 

The first ship designed was a fast combat support ship

 

(AOE). The AOE was sized to have the fuel capacity of a

 

fleet oiler, the ammunition capacity of an ammunition ship,

 

and a partial dry cargo capacity of a stores ship. The

 

hull design was configured using a battleship because of

 

its excellent course and station keeping capabilities. The

 

AOE was given the speed to stay with and be protected by

 

 

the aircraft carrier battle group (CVBG). This also allows

 

combatants to UNREP anytime enemy and operational

 

commitments permit. (13:76)

 

An AOE would be nothing more than a fast, expensive

 

cargo ship were it not for the "high-performance, all-

 

weather cargo transfer system. "(13:77) The transfer rig is

 

a modern version of what was tested and developed by

 

Spencer Miller, Esq. at the turn of the century.

 

Transferring either coal bags or ammunition pallets has

 

been found to be very similar. The rig is called the

 

standard tensioned replenishment alongside method

 

(STREAM). It uses a hydraulic ram tensioner to keep a wire

 

highline tensioned between the UNREP ship and the

 

combatant/customer ship. A one-inch wire rope is passed to

 

the customer by the UNREP ship. It is attached to a

 

special attachment point on the customer ship. The slack

 

is removed, and the ram tensioner keeps up to a 300-foot

 

highline (maximum ship separation) taut no matter how the

 

ships roll. A trolley rides this highline and transfers

 

loads between ships. The largest, heaviest missiles and

 

aircraft engines are lifted by a sliding block on the UNREP

 

ship, transferred to the customer by the trolley, and

 

lowered to the customer's deck by a sliding padeye.

 

Transfers of two-minutes-per-load are normally achieved.

 

(13:77)

 

UNREP ships are configured with priority of transfer

 

 

to aircraft carriers. Aircraft carriers can only UNREP to

 

their starboard sides, so UNREP ships have the highest

 

number of STREAM rigs to their port side. Most UNREP ships

 

are built with four port side delivery stations and three

 

starboard side delivery stations. This configuration

 

allows simultaneous aircraft carrier UNREPs to the port

 

side of the UNREP ship and escort ship UNREPs to the

 

starboard side.

 

In addition to the STREAM stations, sixty percent of

 

current UNREP ships have helicopter hangars and can carry

 

two H-46 helicopters for vertical replenishment (YERTREP).

 

The H-46 helicopter can carry loads internally as well as

 

externally. For VERTREP the load is normally a 4000 pound

 

external load. The helicopter hovers over the UNREP ship,

 

a load is attached to the helicopter via a hook and

 

pendant, the load is picked off the deck of the UNREP ship

 

and taken to the customer ship, the helicopter hovers over

 

the other deck, and the load is released and set on the

 

deck of the customer ship. With two ships nearby, VERTREP

 

can handle about the same amount of stores or ammunition as

 

a STREAM rig. Neither fleet oilers nor the five older

 

ammunition ships carry helicopters. The 17 oilers don't

 

carry enough dry cargo, and the five ammunition ships do

 

not have space for a hangar.(12:11-12)

 

CVBG replenishments are done with one AOE or one re-

 

plenishment oiler (AOR). An underway replenishment group

 

 

(URG) consisting of one oiler (AO), one ammunition ship

 

(AE), and one combat stores ship (AFS) in turn support the

 

AOE/AOR. The URG shuttles to and from the nearest supply

 

base. Upon arrival in the operating area the URG would

 

either replenish the CVBG directly, or they would

 

consolidate (transfer from one UNREP ship to another) their

 

loads with the AOE/AOR which would then replenish the

 

CVBG. The URG would then return to the supply base and

 

repeat the shuttle processa

 

The CVBG endurance is a function of UNREP frequency.

 

The length of time between UNREPs is based on fuel,

 

ammunition, and food consumption. Food consumption is

 

constant. Fuel and ammunition consumption rates vary.

 

ammunition and fuel consumption is based on the type of

 

operations being conducted, and their usage will increase

 

significantly as the tempo of operations increases. (5:50)

 

This could require more frequent UNREPs.

 

Based on computed consumption rates a CVBG should

 

UNREP every four days. Examining a CVBG operating in the

 

Indian Ocean and taking into account URG transit times

 

shows that at least two URGs would be required to resupply

 

from Diego Garcia. One URG UNREPs the CVBG and commences

 

the return trip to Diego Garcia while the other URG

 

resupplies in Diego Garcia and begins its transit back to

 

the CVBG. If Diego Garcia is not available, and the URG

 

has to transit to Subic Bay, RP, or Perth, Australia, at

 

 

least five URGs would be required to sustain the CVBG.

 

(5:50-51)

 

Table 1 lists distances and transit times required for

 

URG transits to various parts of the world. The table

 

assumes an 18 knot transit speed and does not include ship

 

loadout time. (5:50)

 

TABLE 1

 

URG TRANSIT TIMES

 

OPERATING RESUPPLY DISTANCE (NM) ROUND TRIP

AREA POINT TIME (DAYS)*

Eastern Med Naples, Italy 500 3

Rota, Spain 1300 6

 

North Portsmuth, UK 900 4

Atlantic Azores 1500 7

United States 3900 18

 

North Yokosuka, Japan 1400 7.5

Pacific Subic Bay, RP 3000 14

United States 4000 18.5

 

Indian Ocean Diego Garcia 1700 8

(Arabian Sea) Mombasa, Kenya 1700 8

Perth, Australia 4000 18.5

Subic Bay, RP 4000 18.5

 

 

The Navy currently has 11 AOE/AORs to support the 15

 

CVBGs. There are 13 AEs, 18 AOs, and 7 AFSs. These

 

numbers show that the minimum requirement of one AOE/AOR

 

and one URG per CVBG can not be attained, let alone

 

supported. At a minimum, two to five URGs (6 to 15 ships)

 

would be required just in the Indian Ocean. Given the

 

overall strategy of CVBGs operating simultaneously

 

throughout the world, a worst case requirement calls for as

 

 

many as 25 URGs (75 ships) being required to sustain

 

operations. This is considerably higher than the current

 

7-12 URGs (21-36 ships.)

 

In an attempt to alleviate the UNREP ship shortfall,

 

single-product ships (AO, AE, AFS) have been modified to

 

mini-multi-product delivery. On the AE and AFS, one

 

starboard side transfer station has been configured for

 

refueling of destroyers and frigates by transferring own

 

ship cargo fuel. The fuel pumping rate is slow but

 

workable. The AO and AE can be outfitted with three

 

20-foot refrigerated deck cargo containers to carry

 

provisions. These modifications allow a single-product

 

ship to service the fleet when a multi-product ship is

 

unavailable. (12:12-13)

 

Another way to relieve the UNREP ship shortfall is to

 

use commercial tankers and containerships to augment US

 

Navy shipping. However, commercial ships-can only be used

 

to resupply UNREP ships and not combatants. One idea is to

 

modify merchant tankers at one of two possible levels. The

 

lower level of modification would add two port and one

 

astern refueling stations, two port and two starboard UNREP

 

attachment points, a limited US Navy communications

 

package, and two electrical generators to support the added

 

equipment. The higher level of modification would add to a

 

tanker three port and two starboard refueling stations, an

 

OMEGA Navigation system, an extra gyrocompass, a full US

 

 

Navy communications package, and significant safety

 

enhancement equipment. To either modified tanker could be

 

added a helicopter deck area, a sliding padeye for dry

 

cargo transfer, and a raised Mecanno deck. (19:35-36) The

 

Mecanno deck is an erector set style raised platform to

 

carry outsize cargo or modern cargo containers. (14:224)

 

Containerships can transfer supplies from point-to-

 

point as designed. Problems arise because the US Navy

 

requires breakbulk ships not containerships. Also if the

 

containership destination is not equipped to handle the

 

containers, the ship can not be offloaded. Ordnance

 

transfer is also a problem as easy access is required to

 

the cargo. (19:38) Two systems are available to modify

 

containerships to help solve these problems as all new

 

cargo ships being built are containerships. One is a

 

modular elevator in which the elevator shaft and equipment

 

are built into standard cargo containers. The other system

 

is a flat rack. The flat rack is a container without a top

 

and sides. The flat rack-can be used as a cargo bridge and

 

allow access to loaded containers. Using the modular

 

elevator and flat racks roughly turns a containership into

 

a breakbulk ship. The extent of these modifications, hence

 

US Navy usage, is limited as the number of US merchant

 

ships is declining.

 

The future of UNREP is bright. The US Navy is

 

building new Military Sealift Command oilers to UNREP the

 

 

fleet. These oilers are the same as the improved USS

 

Cimarron (AO 177) class oiler and will replace aging World

 

War II era oilers. Another development is a new gas

 

turbine powered AOE, the AOE 6 class. The keel for AOE 6

 

has been laid, and up to fifteen ships of this class may be

 

built. This will enable the replacement of older

 

ammunition ships and ensure at least one multi-product ship

 

for each CVBG. The trend in the US Navy is to continue to

 

build multi-product vice single-product UNREP ships. The

 

latest proposal is to build a ship with the capabilities of

 

both an AE and an AFS.

 

The US Navy is also continuing to develop new UNREP

 

equipment to be used on the new ships. A new refueling

 

hose is under development. The hose is made of

 

polypropylene and is light weight and durable. With this

 

new hose it may be possible to conduct refueling without a

 

wire highline. Only the hose will have to be passed by the

 

UNREP ship. Another new idea is that of tensioned

 

connect-up. Instead of all the line that has to be handled

 

to connect two ships during an UNREP, a small stainless

 

steel wire rope will be passed to the customer and the

 

highline and associated equipment will be pulled over by

 

the UNREP ship using this small wire. A program to

 

standardize all UNREP equipment for the NATO navies is also

 

in progress.

 

The US Navy UNREP program has come a long way from the

 

 

days of sail to the present day. The UNREP concept

 

developed 30+ years ago is still as viable today as it was

 

when developed. It continues to shape the UNREP program

 

and will do so into the next century. The value and

 

importance of UNREP is fully realized, and is getting the

 

attention it deserves.

 

 

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