Such individuals pursue science for science's sake, in much the way that some artists engage in art for art's sake. If such scientists engage in design at all, it is through the formulation of hypotheses and the concoction of experiments to test them. Such activity may be useful to scientists and the scientific enterprise, but it does not necessarily benefit the larger society.
Engineers, on the other hand, are most directly doing engineering when they are engaged in the design of something for some particular purpose that does benefit society. Whatever relevant scientific knowledge and understanding are available to help achieve the goal will certainly be welcome, but in the absence of it, engineers forge ahead. Sometimes this means doing science themselves, such as by devising experiments and collecting whatever data might be necessary for design decisions to be made.
A classic example of this involves the Wright brothers and their pursuit of powered flight. In working toward their goal, they contacted the Smithsonian Institution seeking whatever scientific literature was available, but they found very little in the field of what we today know as aerodynamics. Among the information they sought was scientific knowledge that would guide them in determining what profile to give a propeller. In the absence of that essential information, they conducted their own goal-specific wind tunnel experiments in order to proceed with the engineering design.
Although, in their purest form, engineering and science may be
distinct endeavors, in many cases they are hybrid activities. In practice, engineering and science often work in partnership: Engineers exploit scientific principles and discoveries, while scientists rely on engineering and technology for sophisticated instruments and devices. This is certainly the case in high-tech fields such as microelectronics and nanotechnology. It is also necessary in the design and development of particle accelerators. Some students of science and technology even go so far as to say that without engineering advances in measuring instruments and detection devices, science itself could not advance.
Unfortunately, as with the Chilean mine rescue, all too often it is science -- rather than the engineering that really made the miracle possible -- that grabs the headlines.
Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University. His most recent book is The Essential Engineer: Why Science Alone Will Not Solve Our Global Problems