On board the trimaran-hulled USS Mobile (LCS-26)

5 05 2023

I finally managed to get up close with the trimaran variant of the US Navy’s Littoral Combat Ship or LCS. Developed at a time when I dabbled in the design of high performance marine craft, it was always interesting to see the many different approaches that were taken to finding a right fit of a hull form for a naval platform. And the LCS, especially the trimaran design of one of two variants of the LCS under consideration, represented an exciting move away from the tried and tested.

The USS Mobile at Changi Naval Base during IMDEX Asia 2023.

The LCS programme was the US Navy’s response to the changing nature of the threats that United States was facing. The was made especially apparent by the 9-11 terror attack on its own soil. Traditionally a blue-water navy, the LCS was conceived to fill a gap that the USN had in brown-water or littoral capabilities with a small and compact, agile, shallow draught reconfigurable platform.

The USN’s decision made in the mid-2000s to go with two configurations, a monohull and the Australian Austal designed trimaran, certainly raised eyebrows, as did the extensive use of aluminium alloy — a material that the USN had shied away from due to its susceptibility to stress corrosion and fatigue cracking, from its own experience with aluminium alloy superstructures in the post World War 2 era, as well as the concerns with the loss in structural strength of aluminium alloys at high temperatures.

Also raising eyebrows was the choice of hull form. The trimaran hull in the case of the Austal design was essentially a very slender monohull with two outriggers. It is certainly superior when it comes to minimising the drag increase due to wave generation — a dominant factor in the higher speed range at which the LCS operates. It also has a greater resistance to capsize (the slenderness of monohull is limited by its ability to remain upright). The widely spaced hulls also provide a greater deck area that is always welcome in naval platforms operationally. There is also the advantage of potentially reduced pitch and heave motions in waves due to their smaller waterplane areas, which provides the platform with a superior operability.

In operation for more than a decade — the first of class, the USS Independence was commissioned in 2010, the trimaran LCS as with the monohull variant, have been beset with problems. Cost overruns and a host of operational and maintenance issues have plagued both classes of LCS. Structural cracking, as predicted by material choice sceptics, have also been reported, leading to a reworking of structural design details. Designed to be in service for 25 years, two ships of each classes have already been decommissioned, with more expected to follow.

As for the LCS-26 (the trimaran variants are numbered evenly), USS Mobile, having been commissioned only about two years ago in May 2021, it would have incorporated the lessons the designers learnt from the lead ships in the class. As with the other ships in the class, its expansive main deck permits a large mission bay with stern door for launch of smaller craft to be laid out. On top of this a large two-bay hangar that can accommodate both the ship’s MH-60 helo and a Fire Scout drone, and a helicopter deck can be found. The ship is designed to be manned minimally and is operable with a core crew of 40, and can take up to 35 mission crew.

The USS Mobile, is here as part of a display of warships during IMDEX Asia, a regional naval exhibition that takes place every two years in Singapore. The exhibition, which serves as a showcase of the latest in naval platform, arms and sensor technologies, is often also barometer of the wants and desires of the region’s navies.

The stern door at the Mission Bay.
The Mission Bay.
On the fo’c’sle deck.
The helo bay of the Hangar.
The heli-deck.
The Hangar from the upper deck.
The HCR (Helo Control Room).
A gym set up in the Mission Bay.
A view of the stern. The main hull in is in the centre with four waterjets at the bottom that propel the ship and the stern door of the Mission Bay above. The heli-deck is on top. The two outrigger hulls can be seen on either side of the main hull.


More photographs


Advertisement




The naval powers collide at Changi

29 06 2015

Every two years in May, the international maritime defence exhibition, IMDEX Asia, comes to town and offers a chance not only to catch up with the going-ons in the region’s naval developments, but also a rare opportunity to take a look at some of the the naval assets of the powers in the Asia Pacific region. This year’s treat must have been the chance to get up-close to the very impressive looking and well-built Chinese stealth frigate, the People’s Liberation Army (PLA) Navy’s 4,000-tonne Type 054A Jiangkai II class CNS Yulin (FFG 569).

The People's Liberation Army Navy's Type 054-A Jiangkai II Class Stealth Frigate, CNS Yulin.

The People’s Liberation Army Navy’s Type 054-A Jiangkai II Class Stealth Frigate, CNS Yulin.

The HQ-16 SAM vertical launcher cells on the fore deck.

The 32 cell HQ-16 SAM vertical launcher system on the fore deck.

There were also the ships of some of the navies whose presence in the region helps maintain a balance, chief among them the United States Navy (USN), which was the foreign navy with the largest number of ships at Changi Naval Base with two surface ships and a submarine. These were the Arleigh Burke Class Destroyer USS Mustin (DDG 89), a Freedom Class Littoral Combat Ship USS Fort Worth (LCS 3), and a Los Angeles Class submarine, the USS Pasadena (SSN 752). Some of the others at berth were a Republic of Korea Navy Incheon Class Frigate ROKS Incheon (FFX 811), a Royal Australian Navy Anzac Class Frigate HMAS Perth (FFH 157), and several ships of the regional and Indian sub-continent navies. More on IMDEX Asia 2015 can be found at the exhibition’s website. The next exhibition is schedule to take place from 16 to 18 May 2017.

The USS Fort Worth Littoral Combat Ship.

The USS Fort Worth, a Freedom class Littoral Combat Ship.

USS Mustin, an Arleigh Burke Class Destroyer.

USS Mustin, an Arleigh Burke class Destroyer.

USS Pasadena, a Los Angeles Class submarine.

USS Pasadena, a Los Angeles Class submarine.

SLNS Sayura, a Sri Lanka Navy Sukanya Class Patrol Vessel.

SLNS Sayura, a Sukanya class Offshore Patrol Vessel and the flagship of the Sri Lanka Navy.

The stern of the ROKS Incheon against the incoming storm.

The stern of the ROKS Incheon against the incoming storm.

The KD Lekir, a TLDM (Royal Malaysian Navy) Kasturi Class Corvette.

The KD Lekir, a TLDM (Royal Malaysian Navy)
Kasturi Class Corvette.

The Indian Navy's INS Satpura, a Shivalik Class Frigate.

The Indian Navy’s INS Satpura, a Shivalik Class Frigate.

The silhouettes of two of the Republic of Singapore Navy's Endurance class LSTs.

The silhouettes of two of the Republic of Singapore Navy’s Endurance class LSTs.


Previous posts on other naval vessels: