"Good dramatic bullshit" - Ridley Scott
I hesitate to use the phrase just as Mr. Scott did in the interview I have seen so many times over the years. He didn't mean to make light of the work or thought put into the visual work of his legendary 1984 Apple commercial, he was simply commenting on the process. His reluctance was from an understanding that an average practical mind would want to understand how things work.
If you take any of my loves and influences - assemblage art, science fiction model making, creature effects - the truth is that there is much more fretting over the look than practicality. Many people over the years have taken the famous Star Wars lightsaber and Millenium Falcon and tried to back-engineer them with their imagination. It is a true testament to the intricacy of these models that it can be done, but there wasn't as much a question of "how would this work?" when making a model as a statement of "this looks good visually, and it could work."
This has been true through all the great science fiction movies of the past, from Metropolis to the new Star Trek; good design is a mix of aesthetic and a great deal of skill in improvisation. The answer to the question of "what does this hose on the Millenium Falcon do?" might sadden a professional Engineer, but it doesn't stop his imagination from creating it's own story, and that is the essence of"good dramatic bullshit."