The Mars Rover is an incredible reliability story. And as you may know they have decided to permanently shut it off. A friend recently sent me this email when he saw an article on it.
The Opportunity rover was supposed to last 90 days, and instead lasted 15 years.
Is that due to remarkable engineering, or was the machine really supposed to last that long and the scientists blew their calculations as to its “lifespan”?
I know it’s amazing! It isn’t that they made any errors in calculations. The way a design is made highly reliable is to make it robust to the variabilities of manufacturing, use, and environment. In this case “environment” was wildly undefinable. So the solution was to carefully define all the factors for these types of variabilities and make it as robust as possible to each. So it won’t be until an environmental case that hit’s an extreme past their robustness margin that it will fail. All the margins addressed the stresses associated to random failures and wearout. It’s interesting to see what the wear-out was like. I wrote this article on the wheels a few years back.