On p. 90 Petroski says, " Before the fact one must not only define the design "puzzle" but also verify one's "solution" by checking all the possible ways it can fail." If you are designing something new, how do you go about doing this?
Petroski goes on to say, on p. 105, that "success does not prove the hypothesis to be valid". So, even if you are looking at other similar designs, you can't know if they are truly successful or they just haven't failed yet! How do you move forward with a new idea?
Whether you are designing a structure, a new medical device or software, it must be an incredibly daunting task, in many ways. I would love to know more ( and I know my students would as well) how you go about this.
This is a monster of a toughy! Typically, the more important a/or innovative the design, the more important this step is. Often, independent reviewers are brought in. Sometimes, two separate designs are performed and compared. Almost always an engineer will look to other engineers with different backgrounds to brainstorm for flaws. Generally we focus our energy on looking for the problems. Sometimes this comes across as us being negative or pessimistic, but I think most engineers are looking for the potential problems in order to find a solution, and to avoid a failure, not because of negative view on the world. It is foremost a habit or state of mind that needs to be developed through practice. Think about how something will be used, analyze the consequences of that use. Think about how it may be mis-used, analyze again. Think about the more common general issues that lead to failure - heat/cold, moisture/dryness, fatigue, accidental or intentional overload - and see what affects these may have. I have a friend whose job is trying to make some design engineering software crash or spit out wrong answers - he has to think of all the things that an owner of the software might possibly do. In the end, after all the checks and thinking, there is still some risk, and I think all engineers are aware of it, and we push it to the side so that we can carry on. Many professions require this, from athletics to medicine to the military, mining, construction, fishing, etc. One nice parallel can be found in legislators - it is very difficult to foresee how a given law might be mis-used or reinterpreted, but laws must be written.
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