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The Quest for a Better World PUBLIC ACCESS

For Engineers at Work, One Clay's Achievement is the Platform for Another Day’s Advance.

[+] Author Notes

Henry Petroski, A. S. Vesic Professor of Civil Engineering at Duke University, was a member of the National Academy of Engineering selection committee for the greatest engineering achievements of the 20th century.

Mechanical Engineering 122(12), 46-51 (Dec 01, 2000) (6 pages) doi:10.1115/1.2000-DEC-2

This article highlights the pervasiveness of the products and processes of engineering in having improved the quality of life in the developed countries of the world. The airplane and its associated infrastructure of airports and ticketing schemes have come a long way since the Wright Brothers’ first flight in 1903, and the ensemble that goes under the rubric ‘airplane’ certainly warrants recognition as achievement. All the engineering achievements that have been identified as among the greatest of the past century leave room for improvement. Air conditioning and refrigeration are among the more domestic achievements of 20th century engineering, but at exactly what stage they became so is hard to say. Refrigerators especially came a long way in the second half of the century. Well-controlled air conditioning, for all the technological progress made in the field since air was fanned over a block of ice, seems to remain one of the great open problems of mechanical engineering. All achievements, engineering and otherwise, are relative to their time and circumstances.

Reviewing the greatest engineering achievements of the 20th century has been a wonderful way to celebrate the profession at the end of one millennium and the beginning of another. The list of 20 top achievements unveiled last February by the National Academy of Engineering highlighted the pervasiveness of the products and processes of engineering in having improved the quality of life in the developed countries of the world.

Indeed, the much-discussed list of achievements has been hailed as a virtual blueprint for bringing forth the advancement of conditions in less-developed countries. It is the nature of engineers to play a central role in such development, for it is the nature of engineering to effect change.

The top 10 mechanical engineering achievements of the 20th century, which have been highlighted in these pages throughout the course of the year, are essentially a subset of the NAE’s list and thus show the wide reach of the field.

Few areas of technology are not touched by mechanical engineering. But the greatest engineering achievements also provide incontrovertible evidence of the essentially interdisciplinary nature of all engineering achievements. The electrification of America, for example, has clearly been the success that it has been because of a collection of what might, in this context, be called subachievements. Each of these has been significant in its own field, but none of them individually would be as significant without the others. And the whole is clearly greater than the sum of the parts.

Electrical engineers provided the theoretical foundations whereby power distribution over long distances was made economical; mechanical engineers contributed their expertise to making efficient generators, chemical engineers to developing lubricants and coolants for the machines, civil engineers to building dams for hydroelectric plants, petroleum engineers and mining engineers to ensuring supplies of oil and coal for fossil-fuel plants, nuclear engineers to providing an alternative source of energy to generate power for the grid, materials engineers to providing effective conducting and insulating materials, structural engineers to designing steel transmission towers. No great achievement is wholly the province of a single engineering discipline, but each discipline can take pride in its contributions to the greater good.

Henry Petroski, A.S. Vesic Professor of Civil Engineering at Duke University, was a member of the National Academy of Engineering selection committee for the greatest engineering achievements of the 20th century.

Though the doubtful numerology of the year 2000 may have provided much of the impetus for compiling and elaborating on lists of great achievements, the opportunity to have done so was welcomed by many engineers and engineering societies. It provided the means to reflect on our profession and its central role in the advancement of the milieu of civilization. But now that the year of the zeroes is coming to a close, debates over whether it has been the last of the 20th or the first of the 21st century, and whether the list of engineering achievements should be reordered, can be put aside for other considerations.

Yet while thoughts of the millennium and the philosophical moods that it has engendered remain fresh in our minds, perhaps now is also an opportune time to reflect upon where we have been and where we are going with the great achievements themselves. The word “achievement” suggests a certain П g . completeness, a goal reached, a task finished. The great engineering achievements of a the 20th century do indeed represent in a metaphorical sense the culmination of great adventures for engineers. But engineering feats and exploits are really never-ending. Even the greatest achievements are but indistinct milestones passed on the road to the future.

Engineering, as engineers especially know all too well, is a continuing process. It is a journey, not a destination. What is engineered may, momentarily, be admired for what it is. But engineered things are like leaves fallen in a stream, where they are carried by the swift waters of the past into the still lakes of the future. There, they precipitate into the silt of technology, perhaps someday to be unearthed by an industrial archaeologist. What will such a muckraker find?

The automobile heads the list of mechanical engineering achievements of the 20th century and places second on the NAE’s list. But what is an automobile? Unlike a fin-de-siecle driver of a Stanley Steamer, who had to be prepared to water his machine when it was dry and fix it when it broke down on a rutty rural road, today’s car owner need hardly look under the hood of what has become an easy-to-operate and most reliable machine.

When did the automobile become an incontrovertible achievement? Was it when the toolbox disappeared from the running board? Or was it when the electric starter replaced the hand crank? Perhaps it was when roads became paved and numbered. Would the automobile be what it is today without the infrastructure of filling stations and repair shops? The achievement captured under the rubric “automobile” really connotes that of an entire system.

But like all engineered systems, the system of the automobile and its infrastructure is an ever-evolving one. Who but the collector today wants a car without a radio, intermittent windshield wipers, cruise control, and cup holders? Need the automobile have included all of these things before it qualified as a great achievement? Even if we could specify a checklist of what it takes for an automobile to achieve majority, we might be dissatisfied with our present model as soon as the next model year comes out with the latest driving aids and comfort gadgets.

It takes someone who read Motor Trend and attended the annual auto shows of the 1950s to remember the differences between the 1955 and 1956 model years. As a rule, from year to year, the automobile changed slowly, but the cumulative effect of a hundred years of small changes has made a big difference.

Thus it is with a lot of engineering achievements that we sweepingly summarize in a word or two. Was the steam engine an achievement of the 17th or 18th century? Will the World Wide Web ultimately be associated with the 20th century or with the 21st, when it will truly be accessible to all people in developed and developing nations alike?

Engineers always want to make everything better, but they cannot make anything perfect. This simple characteristic of the profession’s practitioners is what drives change and makes achievement a process rather than a goal.

Understanding this essential fact enables us to speculate with some degree of certainty about future improvements of even the greatest engineering achievements. By identifying what is still wanting in today's technology, we can predict with considerable confidence what will be standard in tomorrows. This is not to say that we can see exactly what form the future will take, for engineering differs from mathematics in that it makes no claim to unique solutions. Whether videocassette recorders today would use the VHS or Betamax format was not at all obvious at the time to many of those closest to the development of the systems.

Consider a car from 1950. It typically had manual transmission, no power steering, a flat windshield, and one-speed windshield wipers. Yet it was perfection to any teenager. New-car owners were extremely pleased with the latest styling and technology, but they were also very much aware of its limitations. Learning to drive a stick-shift car was difficult, requiring the coordination of clutch and gearshift, and it was tricky getting started on a steep hill after stopping for a red light. The automatic transmission has made driving a car much less of a test of mechanical aptitude and foot/arm coordination. Power steering has removed the need for weight training to be able to turn into a parking space. Wraparound windshields obviated the obstructive posts in the field of view. Intermittent windshield wipers eliminated the need to turn a knob on and off while driving through a drizzle.

To predict how the automobile will continue to change over the next century we need only look at what annoys us about it today. Design is effectively proactive failure analysis, and so if we perform a conceptual failure analysis on the late-20th-century automobile, we can predict with some degree of confidence what changes are likely to occur over the coming years, decades, and centuries.

In a recent interview, Ray Bradbury was asked, “If you could eliminate one invention from the last 100 years, what would it be?” He answered, “the automobile,” because it has “killed two million people.” Bradbury likened the highway carnage to “a major war” and lamented the fact that “we’re not paying any attention to it.” Making safer cars should clearly be a goal of engineers in the 21st century. What these cars will look like and what protective features they will have should be of less interest than the accomplishment of the goal.

Another problem with today's automobiles is that they lead drivers into unknown territory. We get lost. The use of global-positioning satellite technology is clearly going to be incorporated increasingly into future generations of cars.

But not knowing our coordinates is only one way of getting lost. I was told recently of a woman who was listening to a book on tape while driving around Philadelphia. She got so engrossed in the story that she found herself in Ohio, three hours from home. The development of smart vehicles, which can operate like airplanes on automatic pilot, would mean that we could actually read books and watch television while cruising down the highway.

The airplane and its associated infrastructure of airports and ticketing schemes have come a long way since the Wright Brothers’ first flight in 1903, and the ensemble that goes under the rubric “airplane” certainly warrants recognition as an achievement. Yet as crowded as airplanes are with passengers, they still leave plenty of room for improvement, especially in the area of safety.

This past year saw two aircraft accident firsts that were particularly shocking. In the summer, an Air France Concorde crashed shortly after takeoff from Paris, and in the fall a Singapore Airlines Boeing 747 broke up after hurtling down a closed runway. In each case, the accident resulted from the plane striking something on the ground. Such incidents are likely to lead to procedures for ensuring that runways are clear of debris and clearly marked “closed” when that is, in fact, their condition.

Though the Air France and Singapore Airlines disasters may not change much of the physical appearance of airplanes or runways themselves, the accidents will very likely influence the way airports are used, which is an implicit part of the achievement of the airplane.

Without faults or accidents, actual or imagined, there might be little driving change in large technological systems. The Concorde was nearing the extent of its original design life when the Air France accident happened. Yet, given the outstanding performance and safety record of the aircraft, there seemed to be little reason to take it out of service. Had the Paris accident not occurred, it is likely that aging Concordes would have continued to fly, perhaps until a serious accident of another kind occurred. Though the Paris accident had little to do with the Concorde’s supersonic speeds, the incident is likely to affect the way supersonic aircraft are perceived for the foreseeable future.

The conventional wisdom might have had it that to be listed among the greatest engineering achievements, a technology should have been “perfected.” In fact, there is no such thing as perfection in artifacts, for engineering is the art of compromise. The sleek Concorde had a relatively small passenger capacity because the plane’s fuselage was small in diameter, a structural necessity because the cabin had to be highly pressurized in order to carry people at almost 60,000 feet, which in turn was necessary to reduce drag. In a technological system, each part of the whole necessarily affects every other part. All other things being equal, flying fast requires more fuel than flying slowly.

All of the engineering achievements that have been identified as among the greatest of the past century leave room for improvement. Air conditioning and refrigeration are among the more domestic achievements of 20th-century engineering, but at exactly what stage they became so is hard to say. Refrigerators especially came a long way in the second half of the century.

At about mid-century, refrigerators were streamlined like automobiles on the outside, but inside they contained a freezer compartment no larger than a breadbox. It had to be defrosted of caked-up ice regularly and with no little mess left on the floor. The frost-free freezer was as welcome an addition to the kitchen as the self-cleaning oven has been. Making ice cubes became trouble-free as the process became automated freezer door. But even opening the door to trieve some ice cubes was apparently seen by some inventor-engineer as something to improve upon, and the ice cube dispenser was introduced into the front of the door.

How can refrigerators develop further? Clearly, they can improve in the way items are stored inside, for it is certainly inconvenient to have to grope behind the turkey carcass to find the cranberry sauce for a late-night Thanksgiving snack. Does this mean that future home refrigerators will acquire some of the features of vending machines, whereby the push of a button brings the desired item close at hand?

Air conditioning works wonderfully when there are wonderful air conditions. But when too many people crowd into a room on a hot and humid day, the room too often feels too crowded, too hot, and too humid. In such circumstances, the greatness of the engineering achievement might understandably be called into question. How is it that the HVAC systems of new and old buildings alike are so difficult to control? Like the little girl with a curl, when “modern” air conditioning is good, it can be very, very good, but when it is bad, it is horrid.

Air conditioning, perhaps the most unglamorous of achievements next to agricultural mechanization and codes and standards, seems also to be the most finicky. Who has not felt too cold when sitting across the table from someone who felt too hot? Who has not had to decide between the draft and the heat? Well-controlled air conditioning, for all of the technological progress made in the field since air was fanned over a block of ice, seems to remain one of the great open problems of mechanical engineering. It should not be surprising to see comfort control among a list of great achievements of the 21st century.

All achievements, engineering and otherwise, are relative to their time and circumstances. When we look back over the century just past, we see clearly that technological progress has been made, and we rejoice in it. But this is not to say that engineers have said the final word on automobiles, airplanes, air conditioning, or any of the other great achievements in mechanical or any other branch of engineering. Rather, these accomplishments have set down the standards, albeit ever-evolving ones, against which achievements of the next century will be measured.

It is no indictment of engineering that its achievements are not perfect, for nothing is perfect. What matters is that engineers of the last millennium, as engineers of all millennia, did the best with what they had to work with at the time. Engineers of the new millennium will do no less.

Just 40 years ago, I learned to use a slide rule, one of the great achievements of the 17th century. The slide rule worked well for what it did under the circumstances, but it clearly limited an engineer’s reach. During my career, the computer buried Napier’s bones, and has given us CAD, CAM, and a host of related CAE technologies. But the more we use these new tools, the more we discover their limitations and their faults.

This in no way diminishes their claim to being great achievements. It merely reemphasizes that engineering is a constant process of improvement. What made the 20th century different from the 19th, which itself saw the rapid rise of the railroad, was the rapidity with which improvements were achieved. (Is the personal computer really only a couple of decades old?) What is most likely to characterize the 21st century is an even faster rate of change from the good to the better. The engineering of the best is always yet to come.

Copyright © 2000 by ASME
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