The very first sizable Classic Space set I had as a kid was 6928 Uranium Search Vehicle, which I loved. I decided to build an updated version.
I made a few intentional changes to the design, but they're all extrapolated from the original. Specifically, the two sections are joined with an articulated tunnel rather than a hinge, and there are modest living quarters (including two beds) inside.
Be sure to check out the full set of photos!