Over the past ten years, Frazer-Nash Consultancy has assisted UK and overseas navies with the management and reduction of electro-magnetic signatures of surface ships and submarines. This support has included:
- Supply of Frazer-Nash's FNREMUS software suite for signature prediction and management
- Consultancy support, including the use of FNREMUS for signature prediction and management
- System design
- Procurement support
Frazer-Nash possesses particular expertise in the following non-acoustic signatures:
Clicking one of the above links will scroll the page to the relevant section.
The management of the first three of these signatures can be extremely cost effective, often requiring only small changes to be made to the design of a surface ship's or submarine's equipment and systems. These changes can usually be easily applied to new vessels as well as at mid-life update.
Static Electric Signature
The Static Electric (SE) signature is detectable only in the seawater surrounding the vessel and represents a near field mine threat. It is also, importantly, the cause of the Corrosion Related Magnetic signature. The SE signature is caused by the use of electrically connected, but dissimilar, metals on the wet surface of the ship or submarine and by the action of its corrosion protection system. The signature is also very dependent upon the environment in which the vessel is operating.
Frazer-Nash has shown that the design of the corrosion protection system is important. A well designed Impressed Current Cathodic Protection (ICCP) system can be used to greatly reduce the signature and to ensure that it remains stable with minimum variation. A poor design of ICCP system can produce a large, detectable signature which is also highly variable and unstable. To design an ICCP system which offers a low, stable signature coupled to good corrosion protection requires the use of reliable, validated prediction software.
Although designing a vessel and its ICCP system for low signatures is important, it is also advantageous to periodically perform SE signature ranging and to set up the vessel's ICCP system for minimum signature.
Frazer-Nash's FNREMUS software can be used to predict the SE signatures of new build and updated vessels and to support SE signature ranging and ICCP set-up.
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The Corrosion Related Magnetic Signature
The Corrosion Related Magnetic (CRM) signature is caused by the distributed electric currents of the SE signature which flow in the seawater surrounding the vessel and return through its hull. The magnetic field caused by these currents is not limited to detection in the water, but extends into the air offering opportunities for airborne search. Like the SE signature, the CRM signature is dependent upon the environment within which the vessel is operating.
Since the signature is caused by distributed electric currents flowing remotely from the hull, it cannot be controlled using a de-gaussing system so other methods must be employed to counter this threat. Because the CRM signature is caused by the SE signature, reduction and management of the CRM signature can also be achieved through design and operation of the ICCP system.
FNREMUS can be used to predict the CRM signatures of vessels and support signature reduction and management activities throughout a vessel's in-service life.
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ELFE Signatures
ELFE signatures constitute a near field mine threat. They also potentially offer a means of far field detection since they propagate along interfaces and can contain information about the vessel causing them. These signatures are caused by mechanisms such as:
- Poor shaft earthing leading to modulation of the return currents of the SE signature
- Ripple on the ICCP system
ELFE signatures can be easily reduced or eliminated.
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Practical Signature Management
Frazer-Nash has practical experience of leading non-acoustic signature management and reduction programmes.
We also provide signature management and prediction services and software to the UK and overseas governments, to prime contractors and equipment suppliers. The company supports new build programmes and mid-life updates in addition to solving in-service problems.
The management of a vessel's SE, CRM and ELFE signatures can be extremely cost effective and often requires only small changes to be made to its equipment and systems. The following activities could form part of a wider signature process for a new build vessel:
- Use the FNREMUS Concept Modeller to determine whether the initial design is likely to conform to the SE and CRM signatures requirement and to determine the benefits offered by different numbers of ICCP anodes. Check signatures performance under a wide range of operational conditions
- Use the FNREMUS Detailed Modeller to determine the optimum configuration and set-up of the ICCP system including the number of zones, reference cell positions, current bias and controller set potentials and gains
- Specify the most cost effective ICCP and shaft grounding technologies necessary to meet ELFE requirements
- Support first of class and in-service ranging using the FNREMUS Range Module
- Continued signature management through routine ranging and ICCP set-up using the FNREMUS Range Module
Frazer-Nash can assist with the complete process described above including assisting with the provision of active shaft grounding and ICCP systems which will dramatically reduce ELFE signatures.
Ferromagnetic Signatures
Frazer-Nash is also deeply involved in research into and the design of measures to reduce ferromagnetic signatures.
The company has supported a wide range of customers with subjects as diverse as:
- Magnetic signature management
- Coiling fit assessments using mathematical modelling
- Prediction of internal magnetic fields
- Support to materials development programmes
- Research into novel construction techniques for magnetic signature reduction
Initial signature predictions are obtained using Frazer-Nash's own magnetic signature polar models. Detailed signature and internal field data are calculated using the electromagnetic finite element code MEGA.
If you would like further information about our services or products, or want to know if we can assist you in a particular project, please complete the form on the Contact Us page.