Stoker, from Martian Dreams
When the Avatar met him in Martian Dreams, Stoker was unable to do his work, since the conveyor belt was broken and out of power; thus, he couldn't get any coal from Coker. Unlike Coker, Stoker was quite chatty, explaining in detail how the power grid of Mars worked. Stoker made it clear that without power, almost nothing would work, and that the conveyor belt needed to be repaired. Lt. Dibbs suggested the Avatar seek out Captain Trippet in Olympus for the task, which they did.
After repairing the belt and jump-starting the furnace to power it, Stoker got all the coal he needed to again do his job.