New water jets to give U.S. Navy littoral combat ships extra punch


February 6, 2013

The purpose of the new jets is to increase the speed of the LCS while lowering running costs ( USS Fort Worth (LCS 3)

The purpose of the new jets is to increase the speed of the LCS while lowering running costs ( USS Fort Worth (LCS 3)

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The U.S. Navy is fitting new Rolls Royce water jets to its Littoral Combat Ships (LCS). Originally designed for a cancelled ship program, four of the new Axial-Flow Waterjet Mk-1 engines will be fitted over the next two years to the U.S. Navy’s fifth LCS, USS Milwaukee (LCS-5) at the Marinette Marine shipyard in Wisconsin, with ten of the class to follow.

The new water jets replace earlier commercial jet systems and, according to the Navy, can pump out half a million gallons (1.9 million liters) of high-density seawater per minute, pushing the LCS at over 40 knots (46 mph, 74 km/h) while providing more power for less weight.

The engines were developed by Rolls-Royce Naval Marine in collaboration with the Office of Naval Research (ONR) and the Naval Surface Warfare Center, Carderock Division, and their purpose is to increase the speed of the LCS while lowering running costs. They do this in part by reducing cavitation, which is what happens when a poorly engineered propeller or turbine runs at high speed and generates bubbles. When these bubbles collapse, they produce spots of high temperature and shock waves that can severely damage equipment.

The LCS are a new class of warships designed to help the Navy deal with post-Cold War naval requirements. They come in two variants, a conventional hull and a trimaran, and are similar to corvettes, though with assault ship capabilities such as a landing deck, a hanger large enough for two SH-60 Sea Hawk helicopters and the ability to launch a small armored assault force. They’re meant to be small, inexpensive and modular with flexible mission capabilities with an emphasis on operating in shallow coastal waters. Much of the design can be swapped out depending on the mission, as too can assets which can be launched from the LCS by smaller vessels, aircraft and unmanned vehicles, which keeps the ship itself out of harm’s way.

A Navy press release said that the Mk-1 will reduce maintenance costs and increase the engine system’s lifespan, though some critics have said that the new jets will be extremely noisy and make it difficult to the LCS to carry out littoral anti-submarine operations.

Source: US Navy

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past. All articles by David Szondy

why hydrojets & why not use on the Next Gen PT type boat class. since PT boats are littorial by nature.

Stephen Russell

This is the same class of ships that were recently found to be " not survivable in combat" and are less than 5 years old and already deteriorating from corrosion. This just makes me want to scream how stupid Washington is and how they find new ways to waste the taxpayers dollars. Why would you have produce an engine for a ship that produces extreme amounts of noise to hunt subs for crying out loud !

Why not just use a small nuclear reactor like our subs do ? That way it could be quiet and could sail independently for 60-90 days at a time. It would only have to come into port to swap out it's mission modules, resupply ammo and food and personnel if needed.

This ship program has been a total cluster@uck from day one just like the F-35 fighter. What the hell is going on in Washington now that we can't build ships or planes ?


The opinions of critics are often wrong there were critics of the M-1 tank that thought we should have been buying more M-60s that were know to be second rate when they were new over 20 years early. Even if the water jets are noisy the sonar buoys aren't.

Most the problems these ships have are a result of cost reduction measures.


Any ship going 40 knots will be noisy. Torpedoes doing 60+ knots are also noisy. Whales are noisy. All seaborne systems have some kind of noise signature (among other signatures). Submariners are very skilled at finding surface ships (and other boats) using thermoclines, towed and bow and stern arrays, buoys and a multitude of other technologies including burst transmission satellite detection. In effect, if you are in a ship near a modern (NATO) submarine and in a conflict zone, you are toast. Your best survivability mode is RAPID acceleration and manoeuvring when you detect a torpedo. These jets give you just that plus a sustained rapid transit capability to get in theatre quickly.

Andrew Cox
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