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I've been trying to identify this movie that I saw as a child for years, with no luck. I remember that a non-military ship visits a shipwreck and the crew downloads the logs from the main computer that's still operational. The logs shows that the wreck has been visited by a number of tubular, hexagon (octagon?) base vessels. Soon after these tubular ships show up and it turns out they are parts of a modular battleship as they lock to each other. They are asked to surrender, and they pretend to do so while they construct a "lightning cannon" that they use when the battleship attempts to dock. A person whom they probably picked up along the way built the weapon and dies when he holds a broken panel together by his hands when they fire it. Anybody could help me figure out which movie is this? Thanks!