Post by thread:Microprocessors and Spacecraft design.

I found this at - http://www.islandone.org/Launch/AkinsLaws.html The writer intended it to refer to designing spacecraft but if you instead applied it to embedded system design most would apply - even the last one in some cases. Worth thinking on - humorous but ..... Even the jokes contain some useful truths. RM ___________________________________________________ Akin's Laws of Spacecraft / [[Embebbed Systems]] Design Engineering is done with numbers. Analysis without numbers is, at best, only an opinion. To design a spacecraft right takes a infinite amount of effort. This is why it's a good idea to design them to operate when some things are wrong. Design is an iterative process. The necessary number of iterations is one more than the number you have currently done. This is true at any point in time. Your best efforts will inevitably wind up being useless in the final design. Learn to live with the disappointment. (Miller's Law) Three points determine a curve. (Mar's Law) Everything is linear if plotted log-log with a fat magic marker. At the start of any design effort, the person who most wants to be team leader is least likely to be capable of it. In nature, the optimum is almost always in the middle somewhere. Distrust assertions that the optimum is at an extreme point. Not having all the information you need is never a satisfactory excuse for not starting the analysis. When in doubt, estimate. In an emergency, guess. But be sure to go back and clean up the mess when the real numbers come along. Sometimes, the fastest way to get to the end is to throw everything out and start over. There is never a single right solution. There are aways multiple wrong ones, though. Design is based on requirements. There's no justification for designing something one bit "better" than the requirements dictate. "Better" is the enemy of "good" The ability to improve a design occurs primarily at the interfaces. This is also the prime location for screwing it up. The previous people who did a similar analysis did not have a direct pipeline to the wisdom of the ages. There is,therefore, no reason to believe their analysis over yours. There is especially no reason to present their analysis as yours. The fact that an analysis appears in print has no relationship to the likelihood of its being correct. Past experience is excellent for providing a reality check. Too much reality can doom an otherwise worthwhile design, though. The odds are greatly against you being immensely smarter than everyone else in the field. If your analysis says your terminal velocity is twice the speed of light, the chances are better that you've screwed up than that you've invented warp drive. A bad design with a good presentation is doomed eventually. A good design with a bad presentation is doomed immediately. (Larrabee's Law) Half of everything you hear in a classroom is crap. Education is figuring out which half is which. When in doubt, document. (Documentation requirements will reach a maximum shortly after the termination of a project.) The schedule you develop will seem like a complete work of fiction up until the moment your customer fires you for not meeting it. Its called a "Work Breakdown Structure" because the Work remaining will grow until you have a Breakdown, unless you enforce some Structure on it. Space is a completely unforgiving environment. If you screw up the engineering, SOMEBODY DIES!