A Review of Some Emerging Aspects on Modern Ship Radar Signature Management

Signature management for modern warship design is increasingly crucial for a platform continued existence and, consequently, for its operational performance. The new generation of military warships requires significantly improved ship signature as regards both the absolute radar cross section (RCS) levels and the ship imaging features.

The absolute RCS level of the ship is a result of the overall integration of the scattering contributions from the ship structures. The ship imaging features imply an additional need to carefully identify and control the spatial distribution of these scattering centres, represented as hot spots in 3D analyses of the platform. It is the improved discrimination and recognition features of new radar sensors that have made it important to know the distribution of scattering centres and its related signature properties. Accordingly, there is a need for the design of stealthy ships together with low signature imaging properties.

A ship’s ability to manage its own signature according to its mission is becoming crucial to military strategies. For instance, the possibility to modify a ship signature from peacetime status to war status will improve that ship’s chances of survival. So, apart from designing a low RCS ship, suitable camouflaging criteria and methods must be identified to obtain the desired signature properties.

Camouflage techniques in the pipeline

Signature management through camouflage techniques is a formidable engineering challenge to be addressed. The basic scope of signature management is the need to reduce the possibility of a ship being classified in peacetime and, thus, being recognisable in times of conflict. In addition, the ability to change ship signature can be used to optimise deception techniques. These aspects will have a dramatic impact on the ship design process, therefore requiring a major rethink of the design philosophy.

For typical combat ships requiring low RCS, previous experiences have made clear that the most significant RCS contributions come from scattering centres localised on the superstructure of the ship. They also come from certain topside mounted equipment and combat system components - including important contributions from the antennas – installed on the upper deck.

The first goal of the design process is to reduce the absolute RCS level of the ship, allowing some margin with respect to the environment RCS noise level which is dependent on the ship type and its perceived missions. Such a goal requires, as a general criteria, to clean up the 3D geometry of the superstructure. For example fig. 1 shows how a new generation ship could appear with respect to one using current design philosophies.

Fig. 1 – Pictorial examples of old/new ship aspect

To achieve this optimisation the approach to ship construction sensor integration and the use of special materials plays a fundamental role. They will require the appropriate application of suitable shipbuilding technology, innovative combat system design, advanced materials design capability and novel integration processes taking account of the whole range of ship requirements and constraints.

For instance, in the same EM engineering process, optimising the integration of combat system sensors can present a conflict with regard the optimisation of RCS and IR signatures. In order to approach these problems in the best way, industry and government departments are defining new team organisations that get involved as early in the design process as feasibility studies, with concepts such as Integrated Topside Design or Technology Mast concepts, in which the relevant new design processes are investigated.

Two main concerns are raised in such scenarios. The first is the need to identify metrics by which projects can measure the performance and the effectiveness of design alternatives to make informed design choices. The second is relevant to the re-definition of the methods and tools needed to perform the trade-off design studies. This requires innovative methodologies to deal with a concurrent design approach.