this is the E102 Industries fuel shuttle As you can see it is and many cases it is a traditional low-g rocket with its nuclear engine . But what this has what those don't is a docking port for the bulls eye station,and a rover at the bottom witch can refuel the rocket with ,fuel,rcs,and if needed electricity. it can also hold up to 4 crew members at a time. As you look somewhat closely at the image you will see that it stands only on 4 legs. and additionally if you look at the top of the rover and at the bottom of the rocket you will see that there are docking ports the reason being that i thought how is the rocket going to refuel after each mission because if it can't then it would serve as a one time fix and not as something that can be re-used. now this image shows the rcs linear ports that the re-fuller has and the standardazation of the ports so that it can be attached with everything else. mass unit's= 28.406 and here is the link to the craft http://www./download/gm4wkoteqktl4ha/E102_Industries_fuel_shuttle.craft I have added a embedded video in this to show you how to get the rover on the ground and re-fuel the rocket
i have modified the rover so that it could hold more fuel so here is the new photo