EPILOGUE: Perspectives in Design: The Deacon's Masterpiece and Hundred-Year Aircraft, Spacecraft, and Other Complex Engineering Systems

Summary

PREVIEW AND GUIDE TO THE CHAPTER

This text is but a small book about a broad topic. It does not pretend to be exhaustive in its treatment of durability related issues. Important topics such as product replacement or recycling, for example, have not been addressed. More specialized texts would do better justice to these subjects than a summary treatment in the present volume. This Epilogue highlights one particular problem related to durability that has not been addressed, but that is becoming increasingly important.

In 1858, Oliver Wendell Holmes published a poem titled “The Deacon's Masterpiece or the Wonderful One-Hoss Shay.” The distinctive feature of the carriage is that all its structural components degrade in such a way that they last a hundred years to a day, and then fail concurrently. Underlying Holmes's poem is a nontrivial design question that is discussed in this paper. To first order, the question can be formulated as follows: How should a system design lifetime be specified, given its underlying components' durability? Or conversely, how should the components in a system be sized given the system's intended duration of operation? A “translation” is undertaken of Holmes's work into engineering parlance, both his sound engineering judgment and his misconception about engineering design. Then, beyond Holmes's example of durability through structural integrity, this paper makes the case for flexibility as an essential attribute for complex engineering designs that can bring about their durability.