Back in the early 1980's I bought a cardboard model that was printed in a book. It was a space freighter which, when assembled, was about 3 feet long. It was an interesting design that had the main ship up front, attached to a Y shaped frame with six cargo containers then the engines at the back.
That book and model are long lost in the dust of the past and all I had to go on was a vague memory. Instead of the solid frame of the cardboard model, I did it as an open framework around a central tube. The cargo containers became cargo ships, able to land, load/unload then return to the parent ship. There is a tunnel system that lets the cargo ship crew go to the main module up front. The idea is that you have this large interplanetary freighter travelling between the bases scattered throughout the Sol system with the cargo ships delivering supplies etc. to them.
Nick Stevens is a real space modeller and artist. He is still active and can be found on Facebook where he shares his latest works.