The image quality is admittedly terrible (being a scan of a print of a microfilm), but this might be of interest… a piece of NASA art circa 1963 depicting the Saturn V with an S-N third stage rather than an S-IVb third stage. The S-N was not a fixed design, but varied over the years; here, it was a fairly stubby stage ten meters in diameter, same as the S-IC and S-II stage. The S-N would vary in diameter and length from design to design, but one common element was the use of a single NERVA solid-core nuclear thermal rocket engine. As shown here, the distance from the nuclear rocket to the Apollo capsule up front just isn’t terribly far; consequently, this depicted a design with extraordinary levels of shielding, or depicted an unmanned Apollo (but then, why the abort tower), or it was just artistic license.
