Henry Petroski

good judgement experience bad learn knowledge

“A good judgment is usually the result of experience. And experience is frequently the result of bad judgment. But to learn from the experience of others requires those who have the experience to share the knowledge with those who follow.”

― Henry Petroski

learn mistake success engineer avant-garde

“No one wants to learn by mistakes, but we cannot learn enough from successes to go beyond the state of the art. Contrary to their popular characterization as intellectual conservatives, engineers are really among the avant-garde.”

― Henry Petroski

NASA failure rate manager Feynman Challenger engineer

“In the early 1980s, managers at the National Aeronautics and Space Administration (NASA) estimated that the flights would be 99.999 percent reliable, which represents a failure rate of only 1 in 100,000. According to the physicist Richard Feynman, who was a member of the commission that investigated the January 1986 Challenger accident, in which the shuttle broke apart shortly into its flight, killing all seven astronauts on board, this “would imply that one could put a Shuttle up each day for 300 years expecting to lose only one.” He wondered, “What is the cause of management’s fantastic faith in the machinery?” Engineers, who were more familiar with the shuttle itself and with machines in general, predicted only a 99 percent success rate, or a failure every 100 launches. A range safety officer, who personally observed test firings during the developmental phase of the rocket motors, expected a failure rate of 1 in 25. The Challenger accident proved that estimate to be the actual failure rate, giving a success rate of 96 percent after exactly 25 launchings.”

― Henry Petroski

design scientist engineer nature art

“It is the process of design, in which diverse parts of the “given-world” of the scientist and the “made-world” of the engineer are reformed and assembled into something the likes of which Nature had not dreamed, that divorces engineering from science and marries it to art.”

― Henry Petroski

computer software cancellation hardware gain industry

"The most amazing achievement of the computer software industry is its continuing cancellation of the steady and staggering gains made by the computer hardware industry."

― Henry Petroski

engineer superhuman mistake check work

"Engineers are not superhuman. They make mistakes in their assumptions, in their calculations, in their conclusions. That they make mistakes is forgivable; that they catch them is imperative. Thus it is the essence of modern engineering not only to be able to check one's own work but also to have one's work checked and to be able to check the work of others."

― Henry Petroski

wooden toothpick simplicity single part material purpose

"The plain wooden toothpick, it may be argued, is among the simplest of manufactured things. It consists of a single part, made of a single material, intended for a single purpose-from which it gets its simple name. It is also among the most convenient and ready of things. It can be used directly out of the box-there being no instructions to read, no parts to assemble, no priming or booting required, and no maintenance expected. When it has served its purpose, it is simply discarded."

― Henry Petroski

engineering calculation failure criterion meaningless number

"I emphasize that virtually every engineering calculation is ultimately a failure calculation, because without a failure criterion against which to measure the calculated result, it is a meaningless number."

― Henry Petroski

engineering achieve function avoid failure

"Engineering is achieving function while avoiding failure."

― Henry Petroski

form failure

"Form follows failure."

― Henry Petroski