Thanks for the help on the previous problem, everyone. The issue was indeed that the Gas Core is throttled way down for thermal power with the generator. I'd have never figured that out by myself... which brings me to......
TL;DR: Where are all these numbers coming from? Why does nothing add up?!
Now I'm getting to play with (and get a headache with) a whole new set of toys. I got the magnetic nozzles and am trying to make them work. Now, I understand that they are intended to be a very low-thrust solution, especially at this tech level, but once again I'm having issues getting my generator to work properly. As you can see from the screenshot, I am using a dusty plasma to generate particles and electric to power the nozzle. I believe the reactor isn't running at 100% because the magnetic nozzle is only requesting 256MW CP, though I'm not sure why the magnetic nozzle is capped at that. Any hints there would be welcome. I see that the Dusty Plasma has 45% efficiency when used with magnetic nozzles, but 256 is not 45% of any of the numbers that I see, nor are any other values!
Even more puzzling is that my generator thinks that 31% of 657 MW is 12 MW. The GUI shows that 40 MW is being requested, so it's not being limited by demand. Also, I'm not sure where that 40 MW number is coming from. Regarding magnetic nozzles, the table in the OP of this thread states that the magnetic nozzle needs 1% of its charged particle energy in electrical, so the (seemingly arbitrary) 256 MW CP should mean that it requires just 2.5MW in electrical charge.
[IMG]http://i.imgur.com/Y43NnDz.jpg[/IMG]
Again I've spent a good few hours going around and around trying to figure this stuff out. When I've got it all figured out I'm going to make some Youtube tutorials and / or bang some time into the Wiki so others don't have to go through this! Thanks again everyone, you're awesome.