The Sophistication of Early Stage Design for Complex Vessels

Abstract

Prior to the introduction of computers into Early Stage Ship Design of complex vessels, such as naval ships, the approach to synthesising a new design had been via weight equations. When it was realised that modern naval vessels (and some sophisticated service vessels) were essentially space driven initial (numerical) sizing needed to balance weight and space, together with simple checks on resistance & powering, plus sufficient intact stability (i.e. simple metacentric height assurance). All this was quickly computerised and subsequently put on a spread-sheet to iteratively achieve weight and space balance, while meeting those simple stability and R&P checks. Thus suddenly it became possible to produce very many variants, for both trade-off of certain requirements (against initial acquisition cost) as well (apparently) optimal solutions. However as this paper argues this speeding up of a very crude synthesis approach, before rapidly proceeding into feasibility investigations of the “selected design”, has not led to a quicker overall design process, nor have new ship designs been brought earlier into service, in timeframes remotely comparable to most merchant ships. It is the argument of this paper that such a speeding up of an essentially simplified approach to design synthesis is not sensible. Firstly, there is the need to conduct a more sophisticated approach in order to proceed in a less risky manner into the main design process for such complex vessels. Secondly, further advances in computer techniques, particularly those that CAD has adopted from computer graphics advances, now enable ship concept designers to synthesise more comprehensively and thereby address from the start many more of the likely design drivers. The paper addresses the argument for a more sophisticated approach to ESSD by first expanding on the above outline, before considering important design related issues that are considered to have arisen from major R.N. warship programmes over the last half century. This has been done by highlighting those UK naval vessel designs with which the author has had a notable involvement. The next section re-iterates an assertion that the concept phase (for complex vessels) is unlike the rest of ship design with a distinctly different primary purpose. This enables the structure of a properly organised concept phase to be outlined. Following this the issue of the extent of novelty in the design of a new design option is spelt out in more detail for the seven categories already identified. The next section consists of outlining the architecturally driven approach to ship synthesis with two sets of design examples, produced by the author’s team at UCL. All this then enables a generalised concept design process for complex vessels to be outlined, before more unconventional vessels than the naval combatant are briefly considered. The concluding main section addresses how a range of new techniques might further alter the way in which ESSD is addressed, in order to provide an even better output from concept to accomplish the downstream design and build process. The paper ends with a summary of the main conclusions.