The Structural parts of your spaceship constitute the frame to which all other parts are attached. There must be sufficient Structure to connect the other parts together or the others cannot function. A Module or Component that is not connected by Structural parts appears in a red box in the spaceship display. When enough Structural parts are added, the red box disappears.
Aqueduct • Bank • Barracks • Cathedral • City Walls • Colosseum • Courthouse • Factory • Granary • Hydro Plant • Library • Marketplace • Mass Transit • Mfg. Plant • Nuclear Plant • Palace • Power Plant • Recycling Center • SDI Defense • SS Component • SS Module • SS Structural • Temple • University