Designed under project
SCB 150, the class overall was a somewhat smaller diesel-powered version of the
nuclear submarines, the first of which entered service only three months after
Barbel, having been laid down only 11 days later. Several features of the experimental were used in the
Barbel-class design, most obviously the fully streamlined "teardrop" hull.
Albacores single-shaft configuration, necessary to minimize drag and thus maximize speed, was also adopted for the
Barbels,
Skipjacks, and all subsequent US nuclear submarines. This was a matter of considerable debate and analysis within the Navy, as two shafts offered redundancy and improved maneuverability. For the first time, the
Barbels also did away with the conning tower, instead combining the functions of attack center and control room into the same space, another feature adopted for all subsequent US submarines. This was facilitated by the adoption of "push-button" ballast control, another feature of
Albacore. Previous designs had routed the trim system piping through the control room, where the valves were manually operated. The "push-button" system used hydraulic operators on each valve, remotely electrically operated (actually via toggle switches) from the control room. This greatly conserved control room space and reduced the time required to conduct trim operations. The overall layout made coordination of the weapons and ship control systems easier during combat operations. The
torpedo tube arrangement of the
Barbels was the same as the
Skipjacks, with six bow tubes in a three-over-three configuration. These (and the
Skipjack-derived
George Washington-class SSBNs) were the only US Navy classes to have this configuration, as subsequent SSN designs used four angled midships torpedo tubes to make room for a large bow sonar sphere, and most SSBNs had four bow tubes. The
Barbels were built with bow mounted
diving planes, but these were replaced by sail planes (aka fairwater planes) within a few years. This feature was standard on US Navy submarines until bow planes returned with the improved , the first of which was launched in 1987. ==Boats in class==