"Yes, a flaw in the materials used to create the model resulted in the trench and the fight scenes. After I’d designed the original concept art, I was hired by George Lucas to build the models. For the Death Star, I ordered a styrene globe. It arrived in two halves, and I began scribing the individual hemispheres to create a villainous effect for the movie. After I’d done most of the work, I tried to connect the two halves together — and discovered that the equator of the plastic had shrunk around the edges. It would've been nearly impossible to connect the halves so that stage lighting would not show this flaw. So I thought about a solution and contacted George for approval: have a trench in the Death Star where the opposing sides would be shooting at each other in dramatic fight scenes. The result would be sending a missile into a tiny hole in the Death Star. George said "yes” to the changes, and the iconic Death Star fight scene was born."