Recent years have seen an increase in incidents of sea pirates using rocket propelled grenades and terrorists driving small craft packed with explosives to attack maritime traffic. The need for merchant ship designers and insurers to understand the effects of damage arising from blast, fragment, shock and flooding is becoming more important.

Bath-based warship and submarine designer BMT Defence Services Ltd, a subsidiary of BMT Ltd, has leveraged its expertise in the field of weapon damage assessment to help meet that need. BMT has developed a software package called PREVENT (PREliminary Vulnerability Evaluation of eNemy Threats), and has been using PREVENT for more than five years to meet the vessel vulnerability assessment needs of its defence customers, most recently in the preliminary design of the UK’s future aircraft carrier (CVF), under contract to Thales Naval UK.

PREVENT is a preliminary design tool used to assess a ship’s vulnerability against a variety of potential threats. It calculates the extent of damage following a weapon hit and assesses the possible damage to key systems and their major components; thus the vulnerability of the ship can be quickly calculated for a range of scenarios. These results may be used as an aid during the design process or to inform any quantitative analysis-based risk assessment.

Roger Cooper, Managing Director of BMT Defence Services, comments: “PREVENT allows users to quickly and easily model ship structure and organise system components throughout the vessel without recourse to specialist consultancy assistance. As a leading independent naval design house we have recognised customers’ emerging needs by providing an adaptive, cost-effective and proven software tool that can quickly and easily provide an overall vulnerability assessment for a vessel.”

PREVENT utilises Weibull’s equations for blast overpressure calculation and the THOR equations for fragment propagation to establish the damage to the ship following a hit by a weapon. The possible locations at which weapon detonation can occur are determined following selection of the weapon. The resulting damage profile can be displayed, along with the associated blast overpressure and fragment densities for each compartment damaged.

PREVENT visualises the ship in two dimensions and allows for pseudo-3D analysis by splitting the ship into longitudinal slices. This provides the user with both graphical and tabular output presentations of the extent of damage arising from blast, fragmentation, shock and flooding.

PREVENT has been used in various stages of the design process; for preliminary design to ensure optimal arrangement of key spaces before the general arrangement becomes established and, for existing vessels, the identification of key areas of vulnerability.

BMT has over 18 years experience providing naval design services for the UK Ministry of Defence and defence prime contractors. BMT’s most prominent projects have included the production of the winning platform designs for the Batch 2 Trafalgar-class (Astute class predecessor) submarine and the CVF aircraft carrier.