TeleTub

Thanks for the advice, I've decided to actually send up new tank modules with only nuke engines on them. This will save weight (no more oxidizer) and I won't have to worry about any shimmy (I have actually been using the normally sized docking ports, not the jr.s but it still had some wobble). I will also have another large docking port center mass freed up which I can use for larger landing modules.

Update: I sent up a new module with a small tank on it and it does run while there is fuel in that small tank but it requires me to be constantly transferring fuel into it for it to work. Even with that, it drains faster than I can transfer fuel. I don't really know what else to do. I might just send up new engine/tank modules altogether. However, if I do that I want to know what is the best thing to do. Should I go full nuclear and maybe even reduce my fuel capacity (I won't need any oxidizer). Should I still keep some kind of liquid engines around?

Ya, I was kinda thinking of doing something like this as a last resort. I'll give it a try but I'm afraid that it will just drain this tiny tank super fast and I will have to have fuel transfer constantly running to keep it going. And yes I checked crossfeed.

The part order goes as follows: nuke, coupler, coupler, service bay, service bay, battery, battery, coupler, coupler, sci junior, reaction wheel, hitchhiker can, and another set of couplers on either side attaching the engine/ tanks assembly. And I have made sure the engine is on. I've played around with about every setting and made sure that all the couplers displayed "disable crossfeed" (this disable and enable toggle thing is kinda confusing) on both sides of the pair.

I assembled a large and relatively modular ship in orbit recently for the purpose of interplanetary travel. I wanted to attach a nuclear engine to the bottom of the ship for more efficient long-range thrust however it seems that It isn't drawing fuel properly. It is attached using a few sets of decouplers and a few service bays and a few hitchhiker cans lie between the engine and the tanks. I make this configuration on the ground and it works just fine but no matter what I try in space it won't fire or even recognizes the fuel being attached to the engine. The only real difference between the ground config and the space one is that the space one was assembled in space and the ground one being assembled in the VAB. Here is a picture, any ideas?