OVERVIEW: The SSN 671 *Narwhal* is a unique nuclear-powered attack submarine (SSN) operated by the United States Navy, notable for its pioneering use of a natural circulation reactor. Although designated as a *Sturgeon*-class submarine, its internal arrangement and reactor design deviate significantly, leading to its consideration as a distinct vessel.

DETAILS:
The *Narwhal*'s development was driven by a desire to create a quieter, more reliable nuclear propulsion system. Construction began in January 1966 at the Electric Boat Division of General Dynamics in Groton, Connecticut, and the vessel was commissioned in July 1969. The primary distinction of the *Narwhal* lies in its S5G natural circulation reactor. Unlike earlier designs which relied on pumps to circulate coolant, the S5G leveraged convection to achieve this, significantly reducing machinery noise and increasing the submarine's stealth. This innovative design served as a testbed for future submarine reactor technology, influencing subsequent classes. The *Narwhal*'s extended hull, longer than standard *Sturgeon*-class boats, accommodated the experimental reactor and associated equipment.

The *Narwhal*'s primary role was anti-submarine warfare (ASW), tasked with locating, tracking, and potentially neutralizing enemy submarines. However, its advanced sensor suite and torpedo armament also provided a credible anti-surface warfare (ASuW) capability. The improved stealth characteristics conferred by the natural circulation reactor made it particularly effective in covert operations, allowing it to operate closer to enemy coastlines without detection. Throughout its service life, the *Narwhal* participated in numerous exercises and deployments, gathering valuable data on the performance and operational characteristics of its advanced propulsion system. Data collected during these deployments directly informed the design of the improved reactors found in later *Los Angeles*, *Seawolf*, and *Virginia*-class submarines.

The *Narwhal*'s sensor suite includes a range of electronic warfare and acoustic detection systems. The AN/WLR-9A is a radar intercept receiver designed to detect and analyze radar signals, providing early warning of surface contacts. The AN/WLQ-4 Sea Nymph is an electronic support measures (ESM) system capable of identifying and locating emitters over a broad frequency range. Passive acoustic sensors include the AN/TB-23/BQ towed array and the AN/TB-16B towed array, providing long-range detection capabilities. The AN/BQS-14 is an active sonar used for close-range detection and navigation, while the AN/BPS-14 radar provides surface search capabilities. The NA-25X radar/IR likely provides enhanced surface search and targeting capabilities. The AN/BRD-6 direction finding system allowed for accurate determination of signal sources. Optical and low-light television (LLTV) periscopes provide visual situational awareness and target identification. The vessel is equipped with six 533mm Mk67 torpedo tubes, capable of launching the Mk48 advanced capability (ADCAP) torpedo, providing a potent anti-submarine and anti-surface capability. The 3-inch Signal Ejector is used for launching flares and other countermeasures.

SPECIFICATION: Length: 96.0 m || Beam: 9.7 m || Draft: 8.8 m || Disp: 5027 t

SENSORS: AN/WLR-9A || AN/WLQ-4 Sea Nymph || AN/TB-23/BQ || AN/BQS-14 || AN/BPS-14 || AN/TB-16B || NA-25X [Radar/IR] || AN/BRD-6 || Generic Submarine Periscope, Optical || Generic Submarine Periscope, LLTV

ARMAMENT: 533mm Mk67 TT || 533mm Mk67 TT || 3-inch Signal Ejector