Hi Dave! Great info.
Can you remember anything about the Alien hardware that was used? It wasn't all CGI was it?
The only CGI was the water tentacle "psuedo-pod". The rest were all models. When Lindsay goes out to hook up the oxygen cylinders she encounters two alien ships. The first was the "Scout". The model was about 12 inches long and shaped kind of like a bicycle seat. The Scout leaves and the "Manta" ship rises up. That model was shaped like a Manta Ray and about 3 feet across. Jim Cameron wanted the alien ships to be transparent and for the audience to be able to see the strange mechanical workings inside. But for them to still be unmistakably vehicles, not the alien life forms (NTIs) themselves.
The hulls of both models were vacu-formed from clear UVEX plastic sheet. UVEX is often used for the vacu-forming of outdoor signage and letters. I think the Scout hull was made in three pieces and the Manta six. They were held together with clear packing tap along the seams. Both models had to be self illuminating. The most interesting thing was the use of custom blown glass plasma filled bottles inside the models that could be illuminated and give odd alien looking light patterns. In addition there were pieces of neon and fiber optics used for additional illumination. Since any internal structural armatures would be seen they were made in organic sculptural forms out of aluminum, which was then polished to a mirror shine. Polished plexiglass structures were also added for additional details.
Both ships were shot "dry for wet" on motion control rigs. Each different practical lighting component was shot as an individual pass to be composited together later on the optical printer (remember, this was long before the advent of digital compositing). Additional bluescreen mattes and reflection passes were also shot. One interesting byproduct of the UVEX hulls was that they flouressed ever so slightly under ultra-violet light. So and additional glow pass was shot as well.
The plasma bottles turned out to be very problematic. No two bottles would glow the same way. And the appearance of the light would change from day to day, depending on the temperature and humidity. One day though we had a literal partial meltdown! The plasma bottles are powered from very high voltage transformers. But unlike neon, they only have one cathode. The electrical energy was then discharged through a grounding wire taped to the outside of the bottle and then run around the aluminum armature and out the back to a ground connection. On one setup, the ground wire didn't get connected or came loose. During one of the long motion control passes, the MC supervisor, Scott, noticed an orange glow coming from behind the stage curtains where the Manta ship was being filmed. He thought "Wait a minute, the Manta is supposed to be glowing blue, not orange!" He ran over to discover the rear of the Manta model engulfed in flames! Molten plastic dripping onto the stage floor. Turned out since the electrical energy could discharge though the ground wire it turned into heat combusting the UVEX shell. Fortunately the hull shell was the only major damage, none of the intricate glass structures were broken by the heat. We had a replacement set of shells made and repaired the model for additional photography.
I'll bet CG models can't do that!
