Vosper Thornycroft Project Cerberus Stealth Corvette

[Triton]

Perhaps the most interesting (although very unlikely to be built for the RN "as is") is the CERBERUS stealth corvette design. The 2000 tonnes, 116m long, Cerberus is designed to deal with the sub-surface, surface and air threats to both itself and vessels in convoy. Cerberus can be installed with the Mk41 Vertical Launch System which allows for the fitting of Evolved Sea Sparrow (ESSM) in lieu of Aster and extends the potential range of weapons that may be carried to include ASROC and the proposed vertical launch Harpoon. A mixture of systems including SeaRAM, a medium calibre gun and two 30mm mountings provides inner layer air defence.

http://navy-matters.beedall.com/fsc-pre2005.htm

 

[Triton]

Is the Project Cerberus stealth corvette similar to the General Dynamics/Austal Independence-class Littoral Combat Ship in capabilities in addition to a similarity in appearance?

 

[RP1]

Short answer: No.

Long answer: Noooooo.

Seriously... the VT design is akin to a classic corvette / light frigate, with speeds of about 30knots and a mix of gun and missile armament, whereas the LCS is an entirely different concept, revolving around the huge mission module bay aft.

RP1

 

[JohnR]

I've been curious about an aspect of these trimaran designs. What would happen in the event of a torpedo strike on one of the secondary hulls/outriggers?

What were they used for, did they contain equipment, fuel or were they empty?

How heavily subdivided were they.

Regards.

 

[TomS]

It varies a lot by design, but in most of the newest trimarans, the sidehulls have very little displacement at rest; they really come into play only as the ship rolls or heels. Systems housed in there tend to be fairly small -- secondary propulsion motors, maybe towed array reels, and fuel or water ballast. Heavy compartmentalization is the rule.

From a damaged stability perspective, the sidehulls are usually small enough that they don't cause severe impacts. They're usually touted as being a net positive for damage control because the sidehulls absorb some damage that would otherwise cause flooding in the mainhull.

 

[RP1]

Further to Tom's comments. Trimaran side hulls - on UK, US and Aus designs at least - are either so long that they are unlikely to be completely lost to a single hit (although raking damage is a possibility in high speed craft), have extensive transverse and horizontal subdivision, large haunches or all three.

To explain haunches, examine the image here:

Note that the inside surfaces of the side hulls are angled inwards - these are the haunches. As the ship heels due to damage to a side hull, these will be immersed, providing additional buoyancy. Similarly, the connecting box structure itself will eventually be submerged. Trimarans typically exhibit significant damaged stability, but at a higher angle of heel than a monohull - but this can be controlled through careful design of the haunches. For a trimaran with shorter side hulls, it is actually possible to design it to survive the entire side hull flooding.

RP1

 

[Rickshaw]

Don't trimarans have weight penalties because of the requirement to increase transverse stiffness between the hulls? In such a design, in heavy seas, a twisting movement is experienced which must be compensated for, which doesn't occur in a monohull design.

 

[Abraham Gubler]

Is there even a contact fused torpedo in service anywhere in the world anymore? Its not the 1940s anymore...

 

[Rickshaw]

Is there even a contact fused torpedo in service anywhere in the world anymore? Its not the 1940s anymore...

The RN managed to find one to do in the BELGRANO. They had to use a WWII torpedo to do it but they still carried them. While that was 1982, some more modern torps have a contact fusing option. The MU90 Impact is the only one I can find listed though, which is expressly designed with an impact fuse. Spearfish has a contact option as an alternative to proximity as does the Russian APR-3E.

 

[RP1]

Don't trimarans have weight penalties because of the requirement to increase transverse stiffness between the hulls? In such a design, in heavy seas, a twisting movement is experienced which must be compensated for, which doesn't occur in a monohull design.

Actually, torsion can be a problem for open-topped structures such as container ships, but that's another story.

The side hulls of a typical trimaran are usually such a small percentage of the overall displacement that the forces the generate are quite small and can easily be handled with sensible structural design. Fatigue is a more significant issue, since the only way to avoid this is to ensure structural continuity and in places to use large castings to prevent stress concentrations. The underside of the connecting box structure is also subject to wave loads (slamming) and so typically a double skin will be used. You are correct that, overall, a trimaran built using conventional methods (as opposed to the trimaran LCS, which is *very* light) will have a higher structural weight fraction, but this is as much to do with their being more surface area to cover in steel as it is to do with the specific load cases produced by the trimaran configuration.

RP1

 

[Brickmuppet]

Does anyone know how well would a trimaran cope with light ice conditions?

I'd THINK that the tresses of having ice between the hulls would be...ummm...bad.

Could you realistically build one to, say, DNV class 1C or B?

I ask because there has been some talk of an austere diesel powered version of the Trimaran LCS for the USCG...

http://www.informationdissemination.net/2009/04/offshore-patrol-cutter-update-lcs-still.html

....but a major Coast Guard cutter, even if not an icebreaker, has to be able to deal with a few inches of ice from time to time.

 

[RP1]

Well, I don't think anyones' going to be building a trimaran ice-breaker anytime soon, but light ice is more likely to impose severe local loads - on the skin of the hull at the waterline - than overall prying loads between the hulls. The only real problem I could think of would be the potential for the ice to simply get stuck between the two hulls if it fails to break into small enough pieces to pass through, but I must admit my understanding of ice physics is poor to non-existent.

WRT a low speed USCG variant of the LCS trimaran, I would be more concerned about the overall robustness of the structure. The high speed requirement has lead to a very lightly constructed ship (there are some pictures and odd factoids floating about that give clues to this) and aluminium (or that strange variant, aluminum) suffers from fatigue. It may be that through cunning design and perhaps some changes to the structure, a USCG variant could be produced, but I wouldn't necessarily pick it as a starting point, even if it does have a *huge* payload pay and flight deck and, I suspect, better seakeeping (in rough weather) than the monohull.

RP1

 

[Triton]

Vosper Thornycroft Project Cerberus Stealth Corvette press release:

VT unveils next generation Trimaran design

19 September 2001

Vosper Thornycroft has taken its family of trimaran warship designs into the next generation with the unveiling of a 116 metre corvette tailored to the export market.

The new design updates the original VT trimaran corvette developed in 1995 and incorporates VT’s unique experience in building the RV Triton Trimaran Warship Demonstrator for the UK Defence Evaluation and Research Agency (DERA).

This experience has made VT a world leader in trimaran warship technology and the knowledge has been harnessed in the Cerberus design, which is unveiled for the first time at the DSEI exhibition to be held in Greenwich.

Jon Beadon, VT Export Ship Sales Director, explains: “Preliminary results from the trials programme currently being undertaken by RV Triton have supported the initial theory of the advantages of a trimaran hull over a monohull. We remain firmly convinced that trimaran hulls will play a significant role in the design of future warships and Project Cerberus places the latest platform technology within this exciting hull form.”

In addition, VT has incorporated some of the advanced features of its Sea Wraith stealth vessel in the new trimaran design, particularly elements that promote a reduced radar cross section. VT has combined these advances with notable trimaran benefits that include savings in propulsion power, improved capability for helicopter operations and better seakeeping. Another innovative approach in warship design is the use of the latest podded propulsion technology.

“The result is a fast, stealthy corvette with the capability of a larger destroyer or frigate. The ship is designed to operate in littoral waters and the advantages presented by the trimaran hull form extend further its operating potential,” adds Mr Beadon.

The Cerberus design is characterised by a long and slender main hull that produces improved seakeeping and this is augmented by a high bow freeboard complimented by a VT fine form ram bow. The cross deck structure begins some 40 per cent of the ship’s length aft of the bow and the clearance of its underside from the waterline (sometimes called wet deck clearance) conforms with results obtained from model tests and the full scale RV Triton trials.

The principal structure is of steel whilst composite materials are to be used for the superstructure, masts and the underwater bodies of the side hulls. The latter are constructed in easily replaceable sections to eliminate corrosion and facilitate repair in the event of damage. The sections are also made impermeable to minimise any resulting loss of buoyancy.

Careful shaping of the hulls and reduced clutter of topsides fittings ensures a low RCS. Advances in integrated mast technology have enabled Cerberus to contain radio communications antennae within the main mast or embedded in the structure.

Infra-red sources are reduced by cooling main engine exhausts and directing them to atmosphere under the cross deck between the hulls, while the side hulls also help to mask IR produced by the main engines and generators.

An innovative approach to propulsion has been adopted with the use of Rolls Royce “Azipull” podded propulsors. These compact units permit the transmission of the required power without excessively long shafting and four units are installed – two aft and two amidships – each driven by a medium speed diesel engine. Wide separation of propulsion plants significantly increases the vessel’s survivability in the event of damage to one engine room.

Cerberus is designed to deal with sub-surface, surface and air threats to both itself and vessels in convoy. The helicopter plays a key role in this capability with typical types able to operate from the ship including NH-90 and SH-60 Seahawk. Provision is also included for the operation of UAVs.

The trimaran configuration permits the installation of the latest multi-function radars such as the Empar without comprising stability or performance. This means that Cerberus can exploit the capabilities of the Aster or Evolved Sea Sparrow families of missiles for more effective air defence. Cerberus is designed for the installation of the Mk. 41 Vertical Launch System, which extends the potential mix of weapons to include anti-submarine and anti-ship missiles. An inner layer defence, provided by a mixture of systems including CIWS, a medium calibre gun and two 30mm gun mountings enhances survivability against air and surface attack.

In addition to the helicopter, the anti-submarine warfare equipment fit includes a low frequency towed array sonar and anti-submarine torpedo tubes. Cerebus also carries a comprehensive electronic warfare outfit, including electronic surveillance measures and both active and passive countermeasures.

“Trimarans are swiftly gaining credibility as a hull form for the next generation of warships. VT is using its unrivalled trimaran experience to take this theory one step further with a viable design that provides navies with a new alternative for their front-line vessels,” adds Mr Beadon.

From: Phil Rood Public Relations Vosper Thornycroft Tel: 023 8042 6000 Fax: 023 8042 6020 E-mail: phil.rood@vosperthornycroft.com

http://www.vtplc.com/Media/Pressreleases/VTUNVEILSNEXTGENE/

 

[Triton]

From Vosper Thornycroft (VT) Group Ltd. via Internet Archive:

CERBERUS

Development

CERBERUS is the result of an evolutionary series of trimaran ship designs developed by VT Shipbuilding and experience gained in the contract to design and build RV TRITON, a unique 97m ocean going research, trials and demonstrator vessel which became operational in 2000.

Reduced ship motions and superior seakeeping ability in higher sea states are the principal attributes of the trimaran, making it an outstanding platform for helicopter operations with a capability beyond those of their monohull counterparts and which consequently makes the trimaran an ideal anti-submarine warfare (ASW) platform.

The CERBERUS corvette design exploits the advantages of the trimaran hull configuration combined with modern electronic systems to provide the capability of a larger conventional ship, but in a smaller displacement and more acquirable form.

Hull Design

The CERBERUS trimaran is characterised by having a very long and slender main hull in order to gain the maximum benefit of reduced powering through reduced wave making resistance; the required transverse stability being provided by a pair of long slim side hulls supporting the primary cross deck structure. Improved seakeeping results naturally from the long, narrow main hull and this is augmented by a high bow freeboard complimented by a VT fine form ram bow.

Stealth

Above water stealth in low Radar Cross Section (RCS) terms is achieved by careful shaping of the hull sides and superstructures into flat, facetted panels displaying common attitudes and angles in both azimuth and inclination. RCS is further reduced from advances in integrated mast technology, which has enabled the majority of radio communications antennas to be contained within the main mast or be embedded in the structure.

Propulsion

The very slender main hull of a trimaran necessitates an innovative approach to the design and arrangement of the propulsion system. Four “Azipull” units are installed- two aft and two amidships- each driven by a medium speed diesel engine. Considerable advantage is gained with this arrangement in that it permits a very flexible combination of engine use

Accommodation and Habitability

The desire today is for reduced deployment costs through low manning levels and CERBERUS has therefore been designed to be fully capable with a crew of 62, plus 10 training berths. The trimaran configuration, with its wide single level cross deck, permits high standards of outfit which, on a comparable monohull, could not be achieved.

Combat System

CERBERUS is designed to deal with the sub-surface, surface and air threats to both itself and vessels in convoy. The increased beam of the trimaran allows for a particularly spacious Combat Information Centre (CIC) and Bridge together with the installation of the latest multi-function radars such as EMPAR without compromising stability or performance.

CERBERUS has been designed to be able to install the Mk41 Vertical Launch System which allows for the fitting of Evolved Sea Sparrow (ESSM) in lieu of Aster and extends the potential range of weapons that may be carried to include ASROC and the proposed vertical launch Harpoon. A mixture of systems including SeaRAM, a medium calibre gun and two 30mm mountings provides inner layer air defence.

CERBERUS carries a comprehensive electronic warfare outfit, which includes electronic surveillance measures and both active and passive countermeasures. The effectiveness of this suite is enhanced by the stealthy design of the vessel.

Dimensions:
LOA 116.00m
LWL 109.00m
Beam extreme 24.60m
Beam (main hull) 8.00m
Draught fi load 6.50m
Displacement:
Half load ca 1900 tonnes
Full load ca 2000 tonnes
Speed: In excess of 28 knots at fi load displacement and not exceeding sea state 4.
Range: Fuel is carried for a range in excess of 3500 nmiles at 16 knots

Propulsion: Four Rolls Royce Ulstein 'Azipull' podded tractor propulsion units each driven by medium speed diesel engine. Two pods are mounted amidships in the main hull and are fixed and non-steerable and installed at the after end of the main hull.

Generators: Three diesel generator sets Two Switchboards
Armament: Combat Management System using 9 multi-function consoles to control and direct:
1x medium calibre automatic gun
2x 30mm secondary automatic canon
1x CIWS
1x Vertical launching system with 16 cells configured for a mix of SAM, AsuW and ASW weapons
2 x surface vessel triple torpedo tube mountings
1 x medium (9-10 tonnes) helicopter.
Complement:
Commanding Officer
5 Senior Officers
2 Junior Officers
4 Aircrew Officers
2 Officers (training)
6 Chief Petty Officers
2 Petty Officers (training)
28 Junior Ratings
6 Ratings (training)

Total 62 + 10 training berths
Construction: Hulls and cross deck structure – steel.
Superstructure and integrated mast- FRP composites.
Communications: Military External Communications
Military Standard Internal Management and Distribution system with Intercom
PABX and Emergency Telephones
Public Address System
CCTV
Domestic Television/Radio
Safety Radio
Commercial Satellite
Commercial Mobile Telephone
Paging

Source:
http://web.archive.org/web/20030831070405/www.vosperthornycroft.co.uk/shipbuilding/product.asp?ItemID=977&s=&catid=476