http://www.wired.com/news/space/0,2697,66457,00.html?tw=wn_tophead_1
This is an article in wired.com about concept drawings for NASA and other
space agencies.
The reason I bring it here, is to point out an example of where
non-working-prototypes are valuable total product lifecycle process.
The artist put it this way:
"Conceptual space art provides the initial glimpse at what could be," said
Rawlings.