from one of my working files for space development possibly applicable elsewhere:

"Only in hindsight does the development of what later turns out 

to be components appear linear - usually, what fits the greater 

puzzle at any point in time could be a result of little related 

component developments that nevertheless converge in a cohesive 

design of scale.

Where development of technology is not linear but drawn from 

an undefined distribution of sources, each invention and notion 

becomes part of the standing reserve to range from for each idea 

and even collective milestones."

full up to date working file link