What Engineers Know
WALTER VINCENTI has had whole careers both as a cutting-edge aeronautical engineer and as a leading historian of technology. Looking back over them, he discusses what his dual vantage point has taught him about how technological innovation works.
QUITE A FEW PROMINENT HISTORI ans of technology have been trained in engineering, and some of them have had careers as practicing engineers before turning to the study of the past. But not many have attained such eminence in both realms as Walter G. Vincenti, who in 1997 marks his fortieth anniversary on the faculty of Stanford University. Vincenti has provided extremely perceptive historical analysis of engineering knowledge, much of it summed up in a remarkable 1990 book, What Engineers Know and How They Know It , but long before he began writing history, he made history in his own right. After finishing graduate work at Stanford in 1940, he spent seventeen years as a research scientist for the National Advisory Committee for Aeronautics (NACA), working at the Ames Aeronautical Laboratory at Moffett Field, near Mountain View, California. During that period he contributed significantly to experimental aerodynamics and transonic and supersonic aerodynamic theory.
In 1956, when he was approached about returning to Stanford as a professor of aerodyocus his attention on high-temperature gas dynamics, the behavior of flowing gases at temperatures that turn them into chemically reactive compounds. Vincenti, as Stuart W. Leslie writes in The Cold War and American Science , brought Stanford’s aerodynamics program “into the space age.” And today Stanford’s department of aeronautics and astronautics still ranks among the top three in the nation, along with those at Caltech and MIT.
Vincenti is a man who has always sought new challenges, and in the late 1960s his interests began shifting more and more to the study of history. In 1971 he cofounded Stanford’s Program in Values, Technology, and Society (now Science, Technology, and Society, or STS), later chairing that program for three separate terms, most recently from 1992 to 1995. Today, at the age of seventy-nine, he is still writing provocative articles on such topics as the “technical logic” of Thomas Edison’s system of electric lighting. In this interview, conducted in Vincenti’s office at Stanford, he addresses the role of engineers in society, describes his transition from technological practitioner to historian, and considers how his practical experience has helped him in better understanding the history of technological innovation.
Walter, you were born in Baltimore but studied engineering here at Stanford. How did you end up on the West Coast?
My father was an Italian immigrant who came to Baltimore when he was about sixteen years old with thirty-five dollars in his pocket. Then he went back to Italy seven or eight years later and married my mother, who was eighteen at the time and arrived here not speaking a word of English. My father began by sweeping out saloons on Light Street on the Baltimore waterfront. By the time of Prohibition he had a wholesale liquor business. But he had no desire to be drawn into bootlegging, so he decided to pack up his family—by then there were four children with one more to come—and move to California. He settled in Pasadena.
How old were you when your family moved?
I was born in 1917, and we moved to Pasadena when I was about three. My father built a house in 1922 on South Hill Avenue, only three blocks from the California Institute of Technology. I grew up there and have always thought of myself as a Californian.
Did the proximity of Caltech have something to do with your interest in engineering?
Oh, definitely. It was wonderful growing up near Caltech. I went to school with the children of some of the professors, and I watched the school expand. At that time, and I guess it’s still true, there was a Friday-evening lecture series by Caltech faculty. I heard Robert Millikan and Carl Anderson and Thomas Hunt Morgan; I remember hearing Edwin Hubble lecture on his new idea of the expanding universe. I climbed around the Guggenheim Aero Lab when it was under construction, and I saw [the aeronautics pioneer] Theodor von Kármán there when I was a kid. I sort of took this kind of environment for granted.
I remember very well when Lindbergh flew the Atlantic. I was ten years old. I was at a Saturday matinee for children, and in the middle of the show they projected a yellow typewritten bulletin saying that Lindbergh had just landed in Paris. Everyone in the theater stood up and cheered. Afterward I became very interested in building model airplanes, and it was this that got me into aeronautics.
So by the time you were a teenager you had decided that you wanted to become an engineer?
Yes. In particular I wanted to do aeronautics. That was at the leading edge of technology. The kind of people who become computer hackers today tended to gravitate in those days into aeronautics.
But you went to Stanford, not Caltech.
Going just three blocks to college wasn’t all that exciting. My two older brothers had gone to Stanford, and I knew it had a good engineering school, and it was quite a bit larger than Caltech. Stanford had had the second formal course in aeronautics in the United States, taught by William F. Durand beginning in 1915. It was second only to MIT. But when I came here in the mid-1930s, aeronautics was still a specialty within mechanical engineering. And it was purely a graduate program, so I had to get my bachelor’s degree in mechanical engineering.
When you finished up your advanced degree in 1940, you went right to the Ames Aeronautical Lab?
Actually I went to Ames two weeks before I graduated, on June 1, 1940. It was hardly begun; the lab was a construction shack, two excavations for foundations, and a lot of mud when winter came. I was the fourth engineer on the staff there. My first couple of years were largely involved with construction work, inspecting the new wind tunnels as they were being built and the pouring of concrete runways and taxi aprons—something I knew absolutely nothing about.
Ames was located at a military air base?
Yes, at Moffett Field, which was built originally for the dirigible Macon back in the thirties. In fact, when I came to Stanford as a freshman in 1934, the Macon was still there, and we used to sit up on the fourth floor of the freshman dorm and watch it come in and go out.
It reminded me of the time my father took me down to the hills north of what was then Mines Field—now L.A. International Airport—to see the Graf Zeppelin arrive from Tokyo on its round-the-world flight in the late 1920s. That made a big impression on me.
What sort of research did you do at Ames?
At first my work was all in subsonics, but toward the end of World War II people in the NACA and particularly at Ames could see that we needed to start learning something about supersonic airflow. So along about ’44 we started the design of the NACA’s first supersonic wind tunnel of any real size. I worked on that design, and when the tunnel was put into operation, I was put in charge, supervising a staff of about forty-five people, maybe twenty of whom were engineers.
Did you enjoy that?
Well, I found that supervisory work wasn’t something I was mad about. But as it turned out, I was able to step out of those duties without getting demoted on the civil-service scale. About that time the Bell XS-1 attained supersonic speeds, and the theoretical field that seemed most exciting to me was transonics.
Pure supersonic flow is relatively easy, and so is pure subsonic. But a mixture of subsonic and supersonic flow in the same flow field is inherently difficult—extremely difficult — or at least it was in those days before we had computers and could beat problems to death. You had to be rather artful in your mathematics.
The numerical work was all done using mechanical calculators?
Well, yes, with hand-operated desk calculators. Every windtunnel group had a battery of six to ten young women in a room “fidgeting their digits,” as we said—punching information into these calculators, reading off the results, and recording them. The kind of thing that would take seconds today sometimes took weeks or months.
You were developing transonic theory after the sound barrier had already been broken. Hasn’t much of your historical study also involved engineering problems that were “solved” in a practical sense before they were understood theoretically?
Yes, and I think that’s a typical situation in technology. You have to look hard to find cases in which the theory is well worked out before the practice. Look at the steam engine and thermodynamics; that whole vast science got started because people were trying to explain and calculate the performance of the reciprocating steam engines that had been built.
In 1957, after seventeen years at Ames, you began your professorship at Stanford. How did that happen?
Frederick Terman, who was the dean of engineering and provost at Stanford, called me up one day and said, “Walter, come over and talk with me. I have something that might be of interest to you.” I went over, we chatted, and he made me an offer. I said that I wanted to go home and talk to my wife and to the people at Ames, where I was very happy. About ten days later I went back to Fred and told him that I’d like to accept, so we shook hands, and that was that. No search committee, and I don’t believe I ever signed any document.
And that’s the way Terman built the Stanford faculty?
Yes, even the history department. I’m told he had a kind of war chest that let him offer faculty positions on the spot. He was a personal search committee. That’s the way he operated.
So you shook hands, and that was it. What happened in your first few years as a professor?
We had expected the department to grow slowly, but in the fall of ’ 57 Sputnik went up, and the lid blew off everything. The people in Washington started pushing money at us to expand, saying, “Look, get into the business full tilt, produce Ph.D.s and research results.” So we found ourselves with a bull by the horns. We grew rapidly, and within five years we had one of the most vigorous academic research departments in the country.
Wasn’t one of the most prominent projects the “hotshot” wind tunnel, which was intended to simulate reentry conditions for spacecraft?
Yes. The new director of the Lockheed Missile and Space Company’s laboratories, Ronald Smelt, had come up with this idea of getting hypersonic speeds in wind tunnels by using a powerful spark. In the confined space of a supply reservoir, this would suddenly cause an enormous increase in the temperature of the gas, which would then blow out with great velocity through a convergingdiverging nozzle. At the time, this appeared to be a promising new type of wind tunnel. But it soon became apparent that it had one very bad, and in the end irreparable, problem. The sparks were so powerful that they caused material to come off the walls of the reservoir, and these would contaminate the airstream. The stream you got was not really pure air; it had other components, some dustlike, some gaseous. So interest in that type of tunnel gradually decreased.
But it had a lot of teaching value.
Oh, yes. The very problems that were so difficult made it a good teaching tool. It also inspired a great deal of valuable theory on hightemperature gas dynamics. I’m happy to say that many of the students we produced went on to outstanding careers, both in teaching and in the aerospace industry.
In the late 1960s you had been at Stanford for more than a decade and had made significant contributions in experimental aerodynamics, transonic aerodynamic theory, and then high-temperature gas dynamics. And you decided that you wanted to go into something quite different.
I had been very fortunate to have participated on the ground floor of three major fields, but each had sort of done its job, and although there were plenty of other exciting things around, history seemed to beckon.
Had you been interested in history before?
Yes, I’ve always had an interest in history. When I was an undergraduate at Stanford—and still today—engineering students were required to take a lot of nonengineering subjects. I got enamored of reading history, which I then continued to do all through my engineering career.
The dean of engineering in the sixties was Joseph Pettit. He encouraged me to put together a history seminar for a small group of interested graduate students; we read books about history related to engineering and met together one evening a week and talked about them—books like Lewis Mumford’s Technics and Civilization . I started this around 1965, and it became a rather successful course among graduate students in engineering. For a time I continued to teach gas dynamics, but I was putting more and more of my effort into my history course.
Soon I began looking around for something I could write about with a minimum of additional work, and it occurred to me that the Durand-Lesley propeller tests would be ideal. William F. Durand and Everett Lesley had worked testing propeller designs here at Stanford from 1916 to 1926. I got to looking into their work and thinking, “This is telling me something. What were these guys really doing aside from testing propellers? What was their methodology, and what was the sort of knowledge they were producing?” I found myself trying to understand the nature of engineering knowledge. After that, I started to use engineering case studies to say something about the cognitive side of technology.
Wasn’t it around then that you were getting under way with the Stanford Program in Values, Technology, and Society?
Yes. In those times the Vietnam protests were going on, and the social critic Jacques Ellul and others were portraying technology as a villain, so some people think our program came into existence to defend technology. But what really happened was that we began to realize that technology was a crucial part of modern culture, but nobody in the university was studying that. People in the humanities and social sciences, at Stanford and elsewhere, weren’t paying much attention to the fact that technology was central to the culture around them.
That technology has to be seen as an integral part of today’s culture is the most important single thing I’ve learned in the twenty to twenty-five years I’ve been seriously studying history. Even now most people, whether in the academy or outside, have the notion that technology is something out there . It either solves problems for the culture or lays problems on the culture, but whatever it does, it’s out there somewhere.
But the view we should have is that our culture, modernday culture, is a technological culture. It will be so viewed, I think, four or five hundred years from now—in the same way that we now look back on medieval culture as a religious culture. Our culture can be understood only in those terms. Now, I know this isn’t a new idea among historians (it’s sort of what Thomas Hughes is saying when he speaks of the “seamless web” of technology and society), but it’s the main thing I carry away from my studies. The old idea that technology is separate from culture dies hard, though.
What led you to collaborate on a book about the Britannia Bridge, the unprecedented tubular bridge built over the Menai Strait in the mid-nineteenth century?
That had to do with my growing interest in the cognitive side of technology. Nathan Rosenberg, an eminent economic historian at Stanford, had spent a year at Oxford and had run across some literature on the bridge and also had seen references to the bridge popping up in other areas of engineering—crane design, shipbuilding, and a number of places. He could see that something was be- ing carried over from one field to the others. This interested him very much, but he couldn’t see what it was that was being transferred. He assembled a lot of source material, but then he got stuck. So, when he joined the faculty at Stanford, he brought all this to me and said, “Walter, what’s going on here? What is it that’s carrying over?”
When I started looking at this material, it fell right in line with my own inquiries; I could see that it was specific elements of knowledge that were carrying over. In building this new kind of bridge, a new body of knowledge was generated that proved useful elsewhere. And it was a kind of knowledge that was not based on any theoretical knowledge.
In the late 1840s it had become necessary to build a bridge across the Menai Strait in northwest Wales, on the main railway line from London to the point where ferries embarked to Dublin. Suspension bridges were coming into increasing use at the time, but engineers in Britain thought that a suspension bridge would be too flexible to carry the weight of railway trains. An arch bridge, which would have been suitable from that point of view, was ruled out because it would have interfered with the masts of the Royal Navy’s ships. So Robert Stephenson, the railway’s chief engineer, came up with an absolutely brand-new idea, a bridge consisting simply of two enormous box beams, each with unsupported spans of 450 feet. The trains would pass through the beams.
With his colleagues William Fairbairn and Eaton Hodgkinson, Stephenson began to study what would be required to build such large beams out of wrought-iron plate, which was a relatively new material in structural use. They found by running tests that their main problem was local buckling of the upper flange under compression. Such buckling was a new phenomenon, and it raised completely unstudied problems. Their studies gave rise to some basic understanding of the buckling of thin-walled structures, which, interestingly enough, is one of the main structural problems that confront us in building airplanes today.
So the engineers developed a certain amount of new knowledge, and they also defined a new class of problems. Their new knowledge could be used not only for railway bridges but for other thin-walled structures. It was used to design box-beam cranes. It was used to design ships’ hulls, which are like a box beam in that they are subject to bending as they go over waves. They began to develop a body of knowledge that carried over into much wider fields of engineering—even aeronautical engineering eventually.
Now, the very interesting thing is that only a few other box-beam bridges of Stephenson’s type were ever built. The bridge design was in a sense a failure—it used more materials than it should have, and ventilation was a problem—but the general body of knowledge that came out of its conception is widely used to this day. And the engineers had to feel their way in developing that knowledge. In the psychologist Donald Campbell’s phrase, the process they went through was one of “blind variation and selective retention.”
That’s a concept you’ve found very useful in analyzing engineering knowledge.
Yes. As Campbell says, in the acquisition and generation of any knowledge that is brand new , you simply have to try things. There’s no other way. What you try is blind, not in the sense of being random—there is a mental winnowing process that goes on—but in the sense that you can’t foresee the outcome. In designing the Britannia Bridge, though the engineers could not foresee the results of their experiments, there was an internal process of selection of what to try in the tests, a process hidden from historical examination. And that of course brings up the really basic question, How does human creativity work?
The Britannia Bridge had to be designed the way it was largely for nontechnical reasons, because of military constraints. Its tubular design did not reflect the unfolding of some technological imperative. Nevertheless, you are insistent that historians not forget the hard technological realities that constrain the engineer’s choices.
Yes, as I look back on it, my thirty-five years in engineering were spent struggling with those realities. And that real world out there can be very intractable. If technology is predominantly “socially constructed,” as some scholars seem to want to believe—shaped mostly by social influences, that is—I wonder what I and my students were doing for all those years. The real world, the constraints that are “out there,” places significant restrictions on one’s room to maneuver.
When we started talking, I thought Fd be asking about your two lives, in engineering and in history. But they’re really not two lives, are they?
No. They’re just different phases. I still have a Friday lunch with my colleagues in aeronautics, and though I don’t do any engineering anymore, I try to keep up with it. But at the same time, I participate in the activities of the Society for the History of Technology. And each side has helped me understand the other better.
From what you’ve said about building model airplanes and about Lindbergh and the Graf Zeppelin , I gather you were an aviation enthusiast. Are you still?
Yes. I’m an unabashed enthusiast to this day. I can get quite excited when I see a new 777 and think about the engineering activity it represents.
Looking to the future, do you consider yourself an optimist?
That’s a good question. I don’t know whether I am or not; it depends on the day of the week. Just a few nights ago I was reading an article on Lindbergh, on his increasing concern about the environment as he grew older. I’m really shocked at what technology is doing to our world and our environment, and I can identify with Lindbergh’s concerns.
I’m also bothered by the tendency of people—especially my colleagues on the faculty—to do more and more work at home, alone, to become more isolated, and to communicate by voiceless e-mail. I’m worried about what such practice may do to the sense of community at a place like Stanford. A scholarly community is really a wonderful thing, yet I see our technology leading us more and more in the other direction. I’m concerned about technology’s effects on the environment, but also on something equally fragile, our sense of community.
Certainly you’ve seen major changes to the environment here in the vicinity of Stanford.
Well, there is something intrinsically enjoyable about technology; it’s fun . People want to design and build things, and you can’t stifle this urge, because technology fulfills deep-seated human needs, emotional as well as practical. And yet the problem of technology’s unintended consequences is one of the biggest issues confronting us. When I was an undergraduate, in the thirties, the Santa Clara Valley here was mainly noted for its fruit orchards. The soil, the climate, everything was ideal, and it was one of the most fertile places in the world for growing peaches, cherries, plums, prunes, and apricots in particular. There were thousands of acres of apricot orchards. On a warm spring evening when the apricot trees were in bloom, there was a kind of perfume in the air over this whole valley. If you went up in the mountains to the west, you would see a carpet of white apricot blossoms covering everything. It was just breathtaking.
All that has certainly changed!
Now it’s wall-to-wall industry. It’s become Silicon Valley. Interestingly enough, for a short time during the war Lewis Mumford was on the Stanford faculty. Industry was starting to spring up even then, and he warned that we were in danger of losing the beauty we had here. He was saying, “Look, let’s zone this valley and let the agriculture survive.” Mumford’s was a voice in the wilderness, and now the orchards are gone. But he was right; the valley could have been developed on the Swiss model, combining industry and agriculture. Private enterprise is a wonderful thing, but a little government control could have assured something better than what we have now.
Regarding your remarks about a loss of community, it’s interesting that engineering remains a communal process, isn’t it?
We tend to think of the great men, the Edisons, but when you start looking closely, you find more and more that it’s a communal activity. Yes, successful individuals stand out, but there are other people around who may have been trying things that didn’t work . That’s as much a part of the communal learning process as the things that did work.
And of course Edison succeeded as well as he did because he relied on a team of people working together. The community of engineering is a major theme of yours, isn’t it? And isn’t that something that other historians, who haven’t been practicing engineers, perhaps miss?
Yes. My criticism of a great deal of technological history—though the situation is changing—is that it focuses too much on individuals. I know from my own experience as an engineer how much we engineers depend on each other, how much we talk to each other and learn from each other. More and more in my writing I’m trying to present this communal aspect of technology.
The problem—and I know this from my own engineering work—is that a lot of what went on never gets into the written record. A lot of going and coming, to-ing and fro-ing, both of people and knowledge, simply doesn’t get into the record. But the communal aspect that an engineer feels in his bones is something that historians from outside are unlikely to feel. I’m sure historians would agree with what I’ve said, but it’s one thing to agree from the outside and another to have lived through it. I’m trying to write some things now that reflect this.
But discounting the importance of individuals is also an ideological stance among some historians who have no actual engineering experience.
The communal nature that they see is, I think, a bit different from what I see. They see the right thing, but not sure for the right reasons. Engineers have to put their heads together just to cope with the real world that’s out there. They also have to cope with social and economic problems, but I think that people from outside tend to underplay the impact of having to struggle with the natural world.
You’ve said that during your career you’ve seen the scope of engineering problems expand increasingly to include social and environmental matters. Could you elaborate on that? Should engineers be redefining the problems they address?
I see this need surfacing here at Stanford. Some engineering faculty define their field quite narrowly in terms of “engineering science.” But I think that engineering must continually redefine itself. I can see a tension within the profession between people who conceptualize engineering in a rather restricted way, traditionalists looking toward the past, and those who realize that engineering has to broaden its scope as society asks different things of it.
Right now a group of young faculty is reinventing the STS program (interdisciplinary programs have to come up for periodic review by the university). They’re mostly from the School of Engineering, and they are really trying to bring engineering more into accord with the broadest concerns of society. Unfortunately, given the shrinking budgets in universities, it’s a difficult thing to bring off without an additional source of funds. But I hope they can do it.