Both of the things I am designing need to be both good and cheap. Getting these designs right is not going to be quick. In both cases there are many constraints to consider, but working within constraints is what makes design interesting.
From a conceptual design point of view there isn't that wide a range of possible choices which are safe, cost effective and robust.. Both have to be exceptionally robust, and have additional physical as well as cost constraints.
The highly mathematical "Process Design" approach is of no use here- I am doing far more geometry than I am calculus.