Introduction to Ships and Naval Engineering

Introduction

Ships are the single most expensive product a nation produces for defense, commerce, research, or nearly any other function. If we are to use such expensive instruments wisely we must understand how and why they operate the way they do.

Ships employ almost every type of engineering system imaginable. Structural networks hold the ship together and protect its contents and crew. Machinery propels the ship and provides for all of the needs of the ship's inhabitants. Every need of every member of the crew must be provided for: cooking, eating, trash disposal, sleeping, and bathing. The study of ships is a study of systems engineering.

There are many types of ships from which to choose from and each type has its advantages and disadvantages. Factors which may influence the ship designer's decisions or the 
customer's choices include: cost, size, speed, seakeeping, radar signature, draft, maneuverability, stability, and any number of special capabilities. The designer must weigh all of these factors, and others, when trying to meet the customer's specifications. Most ships sacrifice some characteristics, like low cost, for other factors, like speed.

The study of Naval Engineering is the merging of the art and craft of ship building with the principles of physics and engineering sciences to meet the needs of a naval vessel in the security and defense of our nation.. It is the study of the research, development, design, construction, operation, maintenance, and logistical support of our naval vessels. This introductory course in Naval Engineering is meant to give each student an appreciation in each of the more common areas of study. It is meant as a survey course that will give some good practical knowledge to every officer assigned to naval service on land, sea or in the air.

Categorizing Ships

The term “ship” can be used to represent a wide range of vessels operating on, above or below the surface of the water. To help organize this study ships are often categorized into groups based on either usage or means of support while in operation or both.

A list of classification by usage might include the following.

• Merchant Ships: These ships are intended to earn a profit in the distribution of goods. A cash flow analysis is done of income versus costs in the calculation of a rate of return on the investment. Engineering economy studies must include receipts earned, acquisition costs, operating and maintenance costs, and any salvage value remaining when the ship is sold in a time value of money study.
• Naval and Coast Guard Vessels: Classified as combatants or auxiliaries. These ships tend to be extremely expensive because their missions require many performance capabilities such as speed, endurance, weapons payload, ability to operate and survive in hostile environments and reliability under combat conditions.
• Recreational and Pleasure Ships: Personal pleasure craft and cruise liners are a specialized class of ships that are run to earn a profit by providing recreation services to the general public. Comfort and safety are of utmost importance.
• Utility Tugs: Designed for long operation and easy maintenance with a no frills approach.
• Research and Environmental Ships: Highly specialized equipment must be kept and often deployed into and out of the water.
• Ferries: People and Vehicles must be able to be loaded and unloaded with efficiency and safety in accordance with a strict time schedule in all weather conditions.

Ships can also be classified by the means of physical support while in operation. Three broad 
classifications that are frequently used by naval architects as shown at Figure 1 reproduced from an “Introduction to Naval Architecture” by Gillmer and Johnson.

• Aerostatic Support
• Hydrodynamic Support
• Hydrostatic Support

Figure 1 - Categories of Seagoing Vessels According to Their Mode of Support