Surface effect ship
A Surface Effect Ship or Sidewall Hovercraft is a watercraft
A watercraft is a vessel or craft designed to move across or through water. The name is derived from the term "craft" which was used to describe all types of water going vessels...

 that has both an air cushion, like a hovercraft
A hovercraft is a craft capable of traveling over surfaces while supported by a cushion of slow moving, high-pressure air which is ejected against the surface below and contained within a "skirt." Although supported by air, a hovercraft is not considered an aircraft.Hovercraft are used throughout...

, and twin hulls
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

, like a catamaran
A catamaran is a type of multihulled boat or ship consisting of two hulls, or vakas, joined by some structure, the most basic being a frame, formed of akas...

. When the air cushion is in use, a small portion of the twin hulls remain in the water. When the air cushion is turned off ("off-cushion" or "hull borne"), the full weight of the vessel is supported by the buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...

 of the twin hulls.

The SES has two advantages over a hovercraft for open sea operation: it is more resistant to slipping sideways when acted on by air or sea and, and it can use water jets for propulsion as the inlet nozzles are always covered by water.

United States Navy

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...

 initiated the SES model test program in 1960. By 1963, a 10-ton
The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...

 test craft called the XR-1 was designed and built to test the surface effect concept. The first version of the XR-1 used fixed plywood
Plywood is a type of manufactured timber made from thin sheets of wood veneer. It is one of the most widely used wood products. It is flexible, inexpensive, workable, re-usable, and can usually be locally manufactured...

 seals at the fore and aft ends of the captured air bubble section. A jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...

 providing 1700 pounds of thrust was used for main propulsion. A separate 110 hp gas engine
Gas engine
A gas engine means an engine running on a gas, such as coal gas, producer gas biogas, landfill gas, or natural gas. In the UK, the term is unambiguous...

 was used to drive lift fans, and also to power out-drive units that were used for off-cushion slow-speed maneuvering. During the first year of testing, the XR-1 was fitted with more powerful main propulsion and flexible fore and aft seals were tested as well.

The XR-1 was also used to test the concept of water-jet propulsion. The ship was modified in 1964 and equipped with gas turbine engines driving the water jet propulsors. The ship's weight increased to 17 tons.

Rohr Industries 1970 to 1980

Rohr Industries
Rohr, Inc.
Goodrich Aerostructures Group, formerly Rohr, Inc., is an aerospace manufacturing company based in Chula Vista, California, south of San Diego...

 became involved in SES history in 1970, taking over the XR-1 test program for the Navy. Rohr continued to use the XR-1 to test propulsion and seal concepts. Their eventual goal was to develop a 3000 ton SES capable of utilizing vertical launch missile systems and anti-submarine helicopters. The proposed ship was to be capable of 80 knots in sea-state 6 conditions. The proposed main power units were to be 4 40,000hp
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...

 gas turbine engines driving water jet propulsors. The 3000 ton ship development contract was canceled in 1980.

The SES100

Two experimental SESs (the SES100A and 100B), both of around 100 tons, with 80 ft (24 m) length and 40 ft (12 m) beams, were developed for the US Military in the 1960s and 70s. They both attained speeds in excess of the program goal of 80 knots (150 km/h). The SES 100B, was built by Bell Aerospace (Textron
Textron is a conglomerate that includes Bell Helicopter, E-Z-GO, Cessna Aircraft Company, and Greenlee, among others. It was founded by Royal Little in 1923 as the Special Yarns Company, and is headquartered at the Textron Tower in Providence, Rhode Island, United States.With total revenues of...

 Corporation) at the NASA Michoud Assembly Facility
Michoud Assembly Facility
The Michoud Assembly Facility is an 832-acre site owned by NASA and located in New Orleans East, a large district within the city of New Orleans, Louisiana, United States. Organizationally, it is part of NASA's Marshall Space Flight Center...

. Driven by 2 semi-submerged, supercavitating
Supercavitation is the use of cavitation effects to create a bubble of gas inside a liquid large enough to encompass an object traveling through the liquid, greatly reducing the skin friction drag on the object and enabling achievement of very high speeds...

 controllable, reversible propellers, achieved speeds in excess of 96 knots (approximately 110 mph) in the Gulf
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...

 outside of St. Andrews Bay in Panama City, Florida
Panama City, Florida
-Personal income:The median income for a household in the city was $31,572, and the median income for a family was $40,890. Males had a median income of $30,401 versus $21,431 for females. The per capita income for the city was $17,830...


The speed was verified by the USAF
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

 ARIS radar. It also fired the Navy's first vertically launched missile (an SM-2
RIM-66 Standard
The RIM-66 Standard MR is a medium range surface-to-air missile originally developed for the United States Navy . The SM-1 was developed as a replacement for the RIM-2 Terrier and RIM-24 Tartar that were deployed in the 1950s on a variety of USN ships...

) while doing 60 knots (110 km/h). It was also used to test automatic ride control and high speed collision avoidance and navigation systems. The 100A ship was used to test waterjet propulsion
A pump-jet, hydrojet, or water jet, is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal pump and nozzle...

, variable geometry inlets and automatic ride control systems. The 100A and 100B were both capable of operating almost completely out of the water on an air cushion with only 18in (46 cm) of sidewall, the propellers or the waterjet inlets entering the water. The 100 ton SES 100B was built for the US Navy as a 1/10 scale model to test the feasibility of using hovercraft and other Surface Effect Ships in combat situations. The top-secret specifications called for a ship capable of entering a combat zone at a speed of over 80 knots (150 km/h) and disgorging a tank and 100 soldiers onto a beach, turning back out onto water and escaping at high speed.

Unlike the hard sidewall SES's, the full skirted AALCs, JEFF A&B were the prototype vehicles for the LCAC's used by the Navy with such success in the Persian Gulf War
Gulf War
The Persian Gulf War , commonly referred to as simply the Gulf War, was a war waged by a U.N.-authorized coalition force from 34 nations led by the United States, against Iraq in response to Iraq's invasion and annexation of Kuwait.The war is also known under other names, such as the First Gulf...


The 3000 ton SES concept was never designed to go up on the beach, like a landing craft. The AALC (Amphibious Assault Landing Craft) and the SES were very different concepts from the beginning. The AALC was a pure hovercraft that is capable of high speed insertion of troops and vehicles onto a beach. As a hovercraft, the LCAC, derived from the AALC has no rigid hull parts that extend past the air cushion. It therefore can operate across the beach. The SES has rigid side hulls that enclose the air cushion, permitting water propulsion but allowing it to only go to the shore when conducting amphibious operations. Design concepts for a 6000+ ton cargo SES's that Rohr and Ingalls Shipbuilding
Ingalls Shipbuilding
Ingalls Shipbuilding is a shipyard located in Pascagoula, Mississippi, USA, originally established in 1938, and is now part of Huntington Ingalls Industries...

 proposed relied on the idea of the ship loading and unloading from beach, lighter, causeway
In modern usage, a causeway is a road or railway elevated, usually across a broad body of water or wetland.- Etymology :When first used, the word appeared in a form such as “causey way” making clear its derivation from the earlier form “causey”. This word seems to have come from the same source by...

 or conventional dock facilities.

Hovermarine SES Ferries

The UK based company Hovermarine developed the HM.2 SES ferry at their factory in Woolston, Southampton
Woolston, Southampton
Woolston is a suburb of Southampton, Hampshire, located on the eastern bank of the River Itchen. It is bounded by the River Itchen, Hampshire, Sholing, Peartree Green, Itchen and Weston.The area is rich in maritime and aviation history...

 in the 1960s. The first HM-2 craft was operated by Seaspeed
Seaspeed was the joint hovercraft operations of British Rail in association with the French SNCF....

 in 1968 between Ryde Pier
Ryde Pier
Ryde Pier is an early 19th century pier serving the town of Ryde, on the Isle of Wight, off the south coast of England.- Before the pier :Before the pier was built, passengers to Ryde had the uncomfortable experience of coming ashore on the back of a porter and then, depending on the state of the...

 and Portsmouth Harbour
Portsmouth Harbour
Portsmouth Harbour is a large natural harbour in Hampshire, England. Geographically it is a ria: formerly it was the valley of a stream flowing from Portsdown into the Solent River. The city of Portsmouth lies to the east on Portsea Island, and Gosport to the west on the mainland...

. The early HM2 suffered from mechanical problems and during a financial crisis in 1969, Hovermarine went into voluntary liquidation and the major assets were acquired by a new company, Hovermarine Transport Ltd, this was subsequently taken over by the American company, Transportation Technology Inc. Production of HM.2s for North and Central America was undertaken by Hovermarine's factory at Titusville, Florida
Titusville, Florida
Titusville is a city in Brevard County, Florida in the United States. It is the county seat of Brevard County. Nicknamed Space City, USA, Titusville is on the Indian River, west of Merritt Island and the Kennedy Space Center and south-southwest of the Canaveral National Seashore...

. Over 110 HM.2's were manufactured in the UK and US

Operational use

Currently SESs are used, primarily as small ferries.
The Soviet Navy
Soviet Navy
The Soviet Navy was the naval arm of the Soviet Armed Forces. Often referred to as the Red Fleet, the Soviet Navy would have played an instrumental role in a Warsaw Pact war with NATO, where it would have attempted to prevent naval convoys from bringing reinforcements across the Atlantic Ocean...

 built two 1050 ton Bora class surface effect corvette
Bora Class guided missile hovercraft
The Bora-class hoverborne guided missile corvette of the Russian Navy, also bears the NATO class name Dergach, is one of the few types of military surface effect ship built solely for marine combat purposes, rather than troop landing or transport...

s. The ships were passed on to the Russian Navy and remain in active service with the Black Sea Fleet
Black Sea Fleet
The Black Sea Fleet is a large operational-strategic sub-unit of the Russian Navy, operating in the Black Sea and the Mediterranean Sea since the late 18th century. It is based in various harbors of the Black Sea and the Sea of Azov....


The Royal Norwegian Navy
Royal Norwegian Navy
The Royal Norwegian Navy is the branch of the Norwegian Defence Force responsible for naval operations. , the RNoN consists of approximately 3,700 personnel and 70 vessels, including 5 heavy frigates, 6 submarines, 14 patrol boats, 4 minesweepers, 4 minehunters, 1 mine detection vessel, 4 support...

 built 9 Alta and Oksøy class
Alta class minesweeper
The Alta class minesweeper is a ship class of minesweepers operated by the Royal Norwegian Navy. An almost identical class of minehunters is known as the Oksøy class....

 surface effect vessels for mine warfare. The Norwegian Navy also operates several Skjold class
Skjold class patrol boat
The Skjold class patrol boats is a new class of superfast, large stealth missile craft, formerly known as MTBs . From 2009, the Royal Norwegian Navy officially label them as coastal corvettes because their seaworthiness is seen as comparable to corvettes. They are built at the Umoe Mandal yard...

 surface effect patrol boats. These ships are the fastest warships in the world with service speeds of 60 knots (117.6 km/h). The prototype (KNM Skjold) was leased and tested for one year by the US Navy.

See also

  • List of amphibious warfare ships
  • Air Cavity System
    Air Cavity System
    Air Cavity System is a commercially offered technology for reducing drag of ships.- Principle of operation :The idea behind ACS is to trap air beneath hull recesses and thus reduce wetted area with associated viscous drag. Since some air will be inevitably carried away by water stream, a pump...

    is a related technology.
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