Atlas III was an American expendable launch system, used between 2000 to 2005, developed by Lockheed Martin to launch a variety of different satellites.The vehicle operated out of Launch Complex 36B at Cape Canaveral Air Force Station.
I recommend turning on "Advanced tweakables" in KSP settings.
To download each variant of Atlas III, go to the "Files" section.
Here are my other projects.
Atlas IIIA, Atlas IIIB
Modified Atlas G with RD-180
Centaur-D1A (SEC), Centaur III (DEC)
