Throughout the world there are hundreds of thousands of villages, remote communities, islands and commercial sites which do not have power or are supplied on an individual basis by small gas or diesel generator sets, small wind turbines and photovoltaic systems. Many of these sites are located in countries where centralized utility systems only exist in urban or industrial areas. The average cost to extend utility power lines, not including new power plant capacity, is approximately $15,000 to $30,000 (US) per kilometre at 1990 prices.

Diesel engine driven generating sets have the largest market share by far of all sources of remote power. Over 10 million diesel generator sets are utilized world-wide to provide power in locations remote from electrical grids. Unlike most energy sources which have a high capital cost with high operational costs, diesel generating sets have a low capital cost and high operating cost. Diesel engine manufacturers are conducting research to increase reliability, reduce emissions, and reduce manufacturing and operating costs.

The high costs are due primarily to the cost of purchasing the diesel fuel and delivering it to where it is needed. Operation and maintenance of the diesel generators may also contribute to high cost at remote sites. These costs generate a powerful economic incentive to find more cost effective alternatives. For many remote locations, the most attractive option is to be able to generate a significant amount of the power at the site.

CATCHING A TRIM

The process of accurately adjusting the state of a submarine to neutral buoyancy and longitudinal balance is termed ‘catching a trim’. This is an important operation which is carried out when a submarine first dives when going on patrol, having left harbour and started passage on the surface. It provides a datum state for the submarine from which subsequent changes in weight or buoyancy can be easily compensated for, and enabling subsequent checks on trim made regularly during the patrol to be soundly based. The importance of keeping in trim is heightened should a submarine be required to remain quiet for any length of time because the process of catching a trim involves running pumps and so tends to be noisy.

It is desirable that when the submarine first dives at the start of a patrol it should not be grossly out of trim, and this requires that a good approximation to being in trim should be achieved before diving. The first step towards that end should have been taken when the submarine returned to harbour from its previous patrol, because it ought then to have been in good trim. From then on all changes in weight, e.g. due to re-storing, are carefully recorded and adjustments made to the contents of the Trim and Compensation (T & C) Tanks in order to correct for them. A methodical way often used for the purpose is by means of a ‘trim crib’, which has been previously drawn up for the submarine and gives the change in amount of water in the T & C Tanks appropriate to each weight change expected to be made during storing.

TERMINOLOGY: SUBMERSIBLE AND SUBMARINE

2.1 There are fashions in the terms used to describe vessels capable of operating underwater, which are particularly evident when their history is under review. Some are well-established, like the preference for calling these vessels ‘boats’ rather than ‘ships’ even when – as applies to ballistic missile deploying submarines – their displacements are some tens of thousands of tons. Others, like the differentiation sometimes made between submersibles and submarines, are contentious and can be confusing. The argument for differentiating is that it was not until the advent of nuclear propulsion, and the associated atmospheric control capability enabling a boat to operate entirely submerged throughout a patrol of several months duration, that the ‘true’ submarine had arrived. The complementary picture of the submersible is that it describes a boat obliged to operate mainly on or near the sea surface – in order to have access to the atmosphere for oxygen for breathing and for combustion propulsion engines – and which submerges periodically when on patrol for the purposes of concealment, undertaking an attack with torpedoes or avoiding attack on itself.

Our preference is to use the term ‘submarine’ and we do so throughout this book with its primary focus on naval purposes. We prefer to leave use of the term submersible to commercial circumstances – if that is the wish of the workers in that field – in which it might more closely convey the modes of operation in use there. The fact remains that all submarine boats are submersible – used adjectivally – and to imply a sharp differentiation is misleading.

PURPOSE

4.1 We start this relatively brief chapter with an explanation of its purpose, because it is different in character from the other technical considerations involved in submarine design. In some ways it is not especially technical at all, but rather akin in nature to the debates on spatial design which architects indulge in. The issues which arise in consideration of the weight/space relationship for submarines might appear at first sight to be simple – they certainly are very basic – but that is deceptive because they become progressively more complicated as the relationship is explored in greater detail. Although the subject of weight and space and how they are related in submarine design is associated with hydrostatics, it goes beyond what can properly be treated under that heading because of the somewhat intangible nature of the relationship and its consequences in some regards as compared with the more matter of fact nature of hydrostatics.

The chapter is ultimately about ‘what determines the size of a submarine’? In a particular submarine design, does it have to be of a certain size to provide enough buoyancy to support its weight or does it have to be of that size to provide enough space for its contents, so that it then has more than enough buoyancy to support its weight? If the former, there would be some space to spare, so how could the extra space be utilised?

INTRODUCTION

7.1 In preceding chapters we have touched in a rather piecemeal way on a number of considerations which bear on the choice of geometric form of a submarine and on the way in which its contents, both inside and outside the pressure hull, could be arranged to best effect. Our purpose in this chapter is to collect those considerations together and also to introduce several other issues associated with arranging the contents of the submarine.

In dealing with the matter of arrangements we will be addressing an aspect of the activities of the submarine designer which are what one might call architectural by nature. As we are both naval architects by profession we can take that description for granted our regret is that so much of a naval architect's time is taken up with engineering matters that he can be limited in the attention he is able to give to architecture. Yet it is an area of activity in which there is still scope as well as need for some art amongst so much science.

It might appear at first sight that the form and arrangements of a submarine present much simpler problems than those of a surface ship. Essentially a submarine is a long tube in which the disposition of most of its contents is arranged longitudinally with little scope for vertical variations. In a surface ship, on the other hand, with its multi-deck configuration, there is freedom for spatial interaction longitudinally, vertically and athwartships to be taken into account.

INTRODUCTION

10.1 Attention in previous chapters has been focused on the technical considerations in submarine design which bear on achieving the required performance. In the first chapter, however, we did point out that the designer has at all times to keep in mind that the submarine should be capable of being produced at an acceptable cost to the customer and be considered value for money, and also that the resources are available for the detailed design and build. Although it is conceivable that performance might be regarded as paramount, and consequently that any costs incurred either directly or to create the resources necessary for building have to be accepted, in most designs it is necessary to keep a strict balance between performance, cost and resources.

It is pertinent to consider the comparison between the cost of building a submarine and that of a corresponding commercial ship. On the basis of displacement tonnage there is a considerable difference in cost per tonne for the two types of vessel. The difference between the two calls for explanation.

One factor is the difference in the way in which the size of a submarine and a commercial ship is expressed. The gross tonnage of a commercial ship is in fact determined by its cargo or hold space and does not involve the weight of the ship itself. It is better to compare costs on the basis of the actual weight of the ship as constructed, termed its lightweight. Making that change, the cost per tonne for a commercial ship is higher but still significantly less than that of a submarine.

INTRODUCTION

11.1 It can be recognised that throughout the book we have placed emphasis on conceptual formulation in submarine design and on the high level of interaction between the sub-systems. It must nevertheless be appreciated that the successful outcome of a submarine design is ultimately achieved by extensive detailed study of every aspect of the design. It is only by detailed studies that the multitude of interaction effects can be identified and resolved. However, such studies have to be conducted within a framework which adequately defines the total design and that is the purpose of the Concept Design phase. The objective is to determine a size and weight plus geometric configuration within which the detailed studies (often conducted by specialist designers) can take place. For example, there is little point in conducting a detailed design of pressure hull structure if the envisaged configuration of the hull precludes achievement of a weight/buoyancy and longitudinal balance. Similarly, there is little point in a detailed investigation of the weapon compartment layout and tankage if its location within the hull is inconsistent with the fore-end configuration.

11.2 Consequently, the designer has to be able to determine the broad design characteristics having an awareness of the details that must follow. He is unlikely to have much information on those details, particularly in an innovative design, but he must endeavour to ensure that the subsequent stages are capable of achievement.

In design, when the trim and compensation arrangements are being addressed, a procedure is required for sizing the tanks and assessing the amount of water in them, i.e. the weight of variable ballast. The method we now describe, which is widely used for the purpose, is to be read in conjunction with Figure A3.1.

1. (a) A standard condition of the submarine is defined, i.e. one with full crew, stores and fuel on board, with the boat in water of standard density 1.0275. A statement is drawn up of all the weights and locations of items which might vary during the course of a patrol, including buoyancy changes, especially those associated with extremes, e.g. maximum changes of seawater density between say 1.00 and 1.03 (or whatever is appropriate for the submarine under design).

2. (b) A graph is prepared with a horizontal axis for longitudinal moments and a vertical axis for forces, the origin representing the standard condition of the boat. The weight and buoyancy changes in the statement from (a) are plotted as a series of discrete points on the graph to the convention that reductions in weight forward are placed in the first quadrant. The aim is to cater for demanding combinations of weight and buoyancy changes which are sensible but nevertheless still serve to establish the boundary of extreme conditions in which the boat might find itself. Thus towards the end of a patrol a submarine, having consumed nearly all of its stores and fuel, might have to enter an area in which sea-water density is high; alternatively a submarine shortly after leaving base to go on patrol might have to enter water which is almost fresh. […]

INTRODUCTION

In this book we attempt to convey an understanding of those aspects of design which are specific to submarines. However, submarine design is just one of many engineering design activities and there are general features which are common to all. Before proceeding to the specific aspects of submarine design, we consider it worthwhile in this first chapter to address the more general aspects and show how they relate to the submarine design task.

DESIGN OBJECTIVES

1.1 Though there are many variations on what may be considered design objectives we suggest that the following three are primary in all designs and should be sustained throughout the whole design process:

1. (a) that the product should perform the functional purpose of the customer or operator;

2. (b) that the design should be suitable for construction within the capability of the technology and resources available;

3. (c) that the cost should be acceptable to the customer.

Though expressed as separate objectives they are interactive and may on occasion be incompatible. The circumstances within which the design takes place may lead to one or another becoming the prime objective with the others subsidiary.

In some situations the performance of the design is paramount: only a design that is capable of fully performing the required function is of interest. In such circumstances the customer would have to be prepared to pay the cost of such a design and even the capital investment to create the technology and resources necessary to realise the design. Some major nations have accepted this situation for defence equipment in the past but it is less prevalent in current political circumstances.

The two authors of this book have been involved in the design of submarines for the Royal Navy for upwards of thirty years, and have also been involved on and off in the teaching of submarine design for much of that time. They both have connections with Vickers Shipbuilding and Engineering Limited (VSEL) the only builders of submarines in the U.K., Louis Rydill as a design consultant and Roy Burcher as the VSEL Professor of Subsea Design and Engineering at University College London (UCL). Roy Burcher runs a postgraduate design course at UCL, which is attended by students from many countries.

With this background, we are only too well aware of the dearth of textbooks on submarine design and engineering. There are also relatively few technical papers on the subject. There was a seminal paper in 1960, published by the Society of Naval Architects and Marine Engineers of the U.S.A., entitled Naval Architectural Aspects of Submarine Design by Arentzen and Mandel, which we regard as an outstanding contribution to the subject but, no doubt because of security issues involved in military submarine design and operation, that splendid opening up of the vistas made possible by the advent of nuclear propulsion for submarines has subsequently become largely closed off to view.

Yet there is still much about submarine design and engineering which can be said without risk of offending against security obligations. The course at UCL is, in fact, completely unclassified and is open to all prospective students with the appropriate qualifications.

INTRODUCTION

9.1 Whilst all vehicles and ships have operating systems, the submarine requires special systems to enable it to operate in its environment between the surface and fully submerged below the sea. The systems are required both for operation in underwater space and for the crew to work efficiently totally divorced from the atmosphere. In concept formulation and initial sizing the systems do not present issues that need to be considered in detail, though they do require provision of space and weight within the hull. Nevertheless, since they are so important to the general operation of the vessel, we devote this chapter to describing particular aspects of submarine systems, how they are operated and the usual form taken by their design. A particularly important aspect of the systems is their integrity and reliability.

The primary systems in a submarine can be categorised under the following headings, though in some cases they overlap:

1. (a) Hydraulic systems – these are provided for power actuation of many valves, systems and controls.

2. (b) High pressure air system – this is required mainly to initially discharge water from the main ballast tanks in changing from submerged to surface condition, but it also has many other uses on board.

3. (c) Water distribution systems – these are required to control the trim of the boat and to eject unwanted water taken on board during various operations.

4. (d) Ventilation and air-conditioning systems – these are distinctive in a submarine because of the special needs of the enclosed atmosphere once submerged.

INTRODUCTION

6.1 The powering of a submarine vehicle is one of the most important factors in the determination of its size. As shown in Chapter 4, power plants use a high proportion of the weight and space available in a submarine, some 35% of weight and 50% of the total volume being devoted to power generation and storage. As we go on to show, the power requirements are determined in conjunction with speed by the size of the vessel, and hence the designer encounters a loop in the design process whereby the output of the power assessment in terms of a volume requirement for propulsion plant is itself a significant input to that assessment. In control engineering terms this is a positive feed-back loop, which can all too easily cause a growth in the total size of the design.

The powering of a submerged conventional submarine is an exercise in efficient energy storage and its conversion to usable power. It is the solution of this problem which dictates the underwater endurance of the submarine. As described earlier, it was only when a nuclear power plant became available that a true submarine could be produced, because it was the development of an energy source totally independent of atmosphere that enabled the true submarine to become a reality. The successful production of a practical nuclear power source not only enabled the design of a true submarine but also shifted the endurance limits to other factors such as the crew and expendable stores, because the nuclear power source endurance is measured in years rather than days or weeks.

FIRST PRINCIPLES OF FLOTATION

3.1 To naval architects the hydrostatic properties of vessels floating on the water surface represent a fundamental part of their stock in trade, and that familiarity readily reads across to submarines on the surface; the hydrostatic properties of submerged submarines are less familiar to naval architects in general, but they can identify the parallels without difficulty. For most other engineers the subject of hydrostatics may not be so familiar. For that reason Appendix 1 is provided which gives the broad principles on which the following discussion is based.

The submarine, like any other marine vehicle, has to be designed to float in the water where its weight is supported by the buoyancy forces due to the displacement of water by its hull. For a surface ship the objective is not simply that it should float at the surface but also that it should remain afloat even if some damage resulted in part of the hull being flooded. To cater for this means the provision of a substantial watertight volume of hull above the normal waterline, (Figure 3.1). This enables the surface ship to accommodate changes in weight by adjusting its level of flotation, i.e. by slightly sinking or rising. The amount of sinkage is governed by the area of the hull at the waterline (the Waterplane Area).

As well as just floating, the ship must remain upright in calm water. This involves the consideration of transverse stability and the concept of GM (Metacentric Height) and GZ which, as shown in the Appendix, is also governed by the characteristics of the waterplane area. (Figure 3.2(a)).