Dr. Heywood Floyd: I do seem to remember a process where you people ask me questions and I give you answers, and then I ask you questions and you give me answers, and that's the way we find out things. I think I read that in a manual somewhere.
HAL 9000: I'm completely operational, and all my circuits are functioning perfectly.
HAL-9000: What is going to happen?
Dave: Something wonderful.
HAL-9000: I'm afraid.
Dave: Don't be. We'll be together.
HAL-9000: Where will we be?
Dave: Where I am now.
Answer: If they didn't, any further manoeuvring would require much more fuel. They would be moving the mass of two ships.