The automobile is the defining technological artifact of the twentieth century. Its familiarity, however, belies its complexity. It is no mean feat to design a car that is fast and powerful yet comfortable and safe-and still affordable. Factor in a few more constraints-durability, ease of repair, enough room for a few kids and the family dog, and an ample power supply for the electric windows, air-conditioning, CD player, and heated seats-and the challenge becomes clear. Precisely because the automobile has become an integral part of our lives, consumer expectations establish a set of formidable and often conflicting design objectives.
Over the last 25 years, automakers have faced growing pressure to incorporate environmental objectives into their designs as well. In particular, consumers and the federal government have pushed for improvements in fuel economy as a way to conserve oil and control pollution. The automobile industry has responded: the gas mileage of the average new car rose from 14.2 to 28.2 miles per gallon between 1974 and 1995.
Now public pressure to improve fuel economy is again rising, in part because of concern over the prospect of global climate change. (Automobiles account for about one-quarter of carbon dioxide emissions, a major contributor to the greenhouse effect.) The key to improving a vehicle’s fuel economy is weight reduction: the smaller a vehicle is, the less power it requires to accelerate and the less energy to maintain a fixed speed. Traditionally, the automotive industry has reduced weight primarily by downsizing, a strategy that has succeeded in cutting the weight of a typical car from 3,500 pounds to 2,500 pounds over the past 20 years. Today, that strategy has reached its limits. Substantial improvements will be possible only through a new approach: making the automobile body out of lightweight materials instead of basic carbon steel.
Although the body accounts for only about one-third of the weight of an automobile, reducing the weight of the body is the sine qua non of the lightweight, fuel-efficient automobile. A car with a lighter body can use a lighter engine, a less massive suspension, and a less elaborate structure. These secondary weight savings can roughly double the benefits: for every 10 pounds saved by reducing the weight of the body, another 10 pounds can be saved by downsizing other parts of the car.
What’s more, many new technologies designed to improve fuel economy are feasible only for cars that are substantially lighter than today’s. Automobile engines, for instance, must balance the goals of efficiency (energy per distance traveled) and power (the force needed to accelerate the car). High-efficiency internal combustion engines, electric engines, or hybrid engines that combine the two are all far less powerful than conventional engines and will achieve a comparable level of performance only with a much lighter vehicle. Reducing the mass of the body is essential to creating a synergy between light weight and new engine technologies.
In 1993, a highly influential paper by energy analyst Amory Lovins of the Rocky Mountain Institute suggested that major automakers (or anyone else with the gumption) could use existing materials and technologies to produce an ultra-lightweight, highly fuel-efficient vehicle. The “supercar” he envisioned would incorporate lightweight plastics, computerized controls, and a hybrid powerplant-a power system that would combine a traditional heat engine and an electric motor, like a modern locomotive. It would weigh roughly 1,000 pounds and achieve well over 150 miles per gallon-yet it would retain the safety and convenience features of today’s automobile.
Lovins pointed out, correctly, that the materials and technologies that would make a supercar possible are fundamentally incompatible with the design, manufacturing, and organizational processes around which the automobile industry is structured. He therefore argued that only a revolution in the industry would lead to a supercar; efforts to improve fuel economy and performance through the incremental adoption of new materials and technologies would cost too much and yield too little.
The supercar concept attracted a great deal of attention among environmentalists, auto industry leaders, and policymakers and even helped inspire an unusual alliance-though its goals fall somewhat short of Lovins’s. In 1994, U.S. auto companies and the federal government joined forces to launch the Program for a New Generation of Vehicles, an aggressive research and development project whose goal is to produce a car that meets a fuel-economy standard three times higher than today’s 27.5 miles per gallon and that offers the performance and convenience of a conventional car-for the same price. By combining the resources of the national laboratories and the major U.S. automakers, PNGV researchers hope to develop a prototype vehicle within 10 years and to mass produce and market it within 20.
The question is not whether an ultra-lightweight vehicle offering revolutionary improvements in fuel economy can be built. Automakers already know that it can. The question is whether such a car can be made affordable, and what kinds of changes in the automobile industry will be necessary to bring us closer to that goal. In particular, automakers and supercar proponents are debating the costs and benefits of two classes of materials that could serve as lightweight substitutes for steel in vehicle bodies: aluminum, which can be adopted with only incremental change in the industry’s design and manufacturing processes; and plastics, which cannot.