Throop Polytechnic’s Hydraulics and Mechanical Engineering Lab in the early 1910s. From left: Raymond Catland, Charles Wilcox, Harold Black, and Robert Bultman, all BS ME ’15.

Mechanical Engineering Celebrates Its Centennial

Mechanical Engineering at Caltech turns 100 this year, and a party called “It’s All About ME” was held on March 30 and 31. “I was in rather a quandary trying to organize it,” laughs Chris Brennen, the Hayman Professor of Mechanical Engineering. “The alumni only like to hear about the past, and the faculty only like to hear about the future. I got complaints from both groups, so I must have done a good job.” The hundred or so returning alums got a dose of history, but they were also treated to lectures and posters on current research, and talks by alumni on new directions in the field. There was also live entertainment, as it were, in the form of a restaged ME 72 design competition and a demonstration of Alice, Caltech’s self-driving entry in the upcoming DARPA Urban Challenge in which robot vehicles will try to navigate themselves through 60 miles of city streets.

In 1907, the then-Throop Polytechnic Institute was in a cluster of buildings in downtown Pasadena, at the intersection of Fair Oaks Avenue and Chestnut Street. The ME department’s start was modest enough—the only degree offered in engineering was electrical, and the sole ME course, Theoretical and Applied Mechanics (lab and lecture), was listed as Math 13. But as the catalog for 1907–1908 stated, “It is also the purpose of the Institute to extend the work along these lines as demand for it arises.” Arise it did—the 1910–1911 catalog listed two faculty associates in mechanical engineering and, in the tradition of the low student-to-faculty ratio for which Caltech remains famous, two juniors pursuing mechanical engineering degrees. By the time Throop changed its name to the California Institute of Technology in 1920, the ranks had grown to three professors, an instructor, and 81 students.

But it was Caltech’s Pump Lab, founded in the early 1930s by Robert Knapp (PhD ’29) and instrumental in developing the equipment needed to bring water from the Colorado River to a thirsty Los Angeles, that “marked the transition from the department being a technical school that trained engineers to inventing the engineering of the future,” says Brennen.

This transition was complete by World War II, when Knapp and colleagues turned their attention to broader
issues of hydrodynamics. Chief among these was the noisy cavitation caused by the high-speed propellers on submarines that alerted their prey to their presence, and gave their positions away to the destroyers waiting above. And on the other side of the battle, torpedoes dropped from airplanes tended to take off in any old direction upon hitting the water. The problem was solved by stabilizing fins invented at Caltech and tested first in the lab and then at full scale up at Morris Dam, in the San Gabriel River canyon above nearby Azusa. “The remarkable body of literature generated in those years is still sought out—50-year-old reports that are still read by people working in high-speed flow,” says Brennen. “And during the centennial, most of the people that wrote those reports were here.”

Caltech’s Hydrodynamics Laboratory’s high-speed water tunnel, designed by Knapp, seen in the mid-1940s.

The study of high-speed flows burgeoned in the 1950s and ’60s, with the development of the instruments and equipment needed to observe them. “The million-frame-per-second camera designs developed by Albert Ellis (BS ’43, MS ’47, PhD ’53), for example, are still in use today to observe fractures as well as flows,” Brennen remarks. [For more on cavitation and high-speed cameras, see E&S 2007, No. 1.] These instruments, in turn, allowed various faculty members to do basic analyses of how combustion chambers, gas turbines, and jet engines work, leading to the much more efficient designs of today. Similar strides were made in analyzing flows in which more than one state of matter is present, such as the solid-liquid jumble found in a mudslide, the solid-gas (granular) flow of coal in a power plant, or the three-phase flows of solid, liquid, and gas in a core meltdown in a nuclear reactor.

All of this analysis meant a lot of new mathematical techniques were needed. Various faculty members rose to the challenge, devising methods for grappling with random and nonlinear phenomena. A good example is the development of the mathematics underlying nonlinear elasticity, which refers to a situation where the force required to bend something is not proportional to the amount it bends. This includes the behavior of rubber or anything else that’s soft and squishy, as well as such exotica as the shape-memory alloys used, for example, in stents to hold open clogged blood vessels. Roughly half of these are made of a metal that, at body temperature, opens up from a collapsed, easily insertable form into a hollow tube.

An influx of young faculty in the 1980s took the department in a host of new directions, says Brennen. “Mechanical Engineering has broadened tremendously—thin films, robotics, computational mechanics, control and dynamical systems, bioengineering, nano- and microsystems. The centennial was a celebration of that diversification.” The professorial faculty now numbers 17, and the department is ranked third in the nation among graduate programs by U.S. News & World Report and fourth in worldwide impact by the Institute for Scientific Information’s Science Citation Index.

Two ME alumni speakers, Garrett Reisman (MS ’92, PhD ’97) and Robert Behnken (MS ’93, PhD ’97), seen at their day jobs training for their upcoming Space Shuttle flight to the International Space Station in February 2008. Reisman gets to stay there, replacing ESA astronaut Léopold Ehyarts.

The department’s next century will undoubtedly bring more new directions, says Brennen. “Engineers take ideas and turn them into practical solutions. Energy R&D is a big component of ME today—producing devices to make energy or use it more efficiently. But there are other threads. The mechanics of biological systems and biologically compatible systems will be big in the future. So will the engineering of complex systems—how do you engineer, design, and fabricate complex electromechanical systems from cars to spacecraft?” Not surprisingly, the Caltech-JPL connection was a recurring theme throughout the celebration. “JPL has gone a long way in inventing the organizational techniques needed to do this successfully. In my view, despite all the consumer-product effects one hears about, this is by far the biggest spin-off from JPL and from NASA, and the continuing development of these complex management and control methodologies is likely to be a major part of mechanical engineering in the future.” —DS