**OVERVIEW:** The SSN 671 *Narwhal* is a unique nuclear-powered attack submarine of the United States Navy. Designated a "research and development submarine" (SSNR), *Narwhal's* construction and service focused on advanced propulsion and sensor technologies, departing significantly from contemporary attack submarine designs. Although resembling a *Sturgeon*-class submarine externally, *Narwhal's* internal systems and mission profile were substantially different.

**DETAILS:**

The *Narwhal* was conceived as a test platform for a direct-cycle, natural circulation S5G reactor, a design intended to be significantly quieter than existing pressurized water reactors used in US Navy submarines. Construction began in January 1966, and *Narwhal* was commissioned in July 1969, though it is likely the commission year of 1987 in the provided data represents a significant refit or overhaul with updated systems. The natural circulation reactor, while quieter, also proved to have certain performance limitations compared to forced-circulation designs. The operational experience gained from *Narwhal* was invaluable in shaping future US submarine propulsion designs. The submarine's unique reactor design dictated numerous internal changes, including different machinery arrangements and hull modifications to accommodate the larger reactor compartment. This also influenced sensor placement and overall layout.

*Narwhal* primarily served as an ASW platform, with secondary roles in ASuW and intelligence gathering. The installation of the AN/BQQ-5C(V)2 sonar suite, incorporating the BQS-12 active sonar, provided both passive and active detection capabilities. This allowed for detection, classification, and tracking of enemy submarines in a variety of acoustic environments. Supplementing this was the AN/WLR-9A electronic support measures (ESM) suite, enhancing situational awareness by detecting and identifying radar emissions from surface ships and aircraft. The AN/WLQ-4 Sea Nymph system provided advanced signals intelligence (SIGINT) gathering capabilities, enabling the submarine to monitor enemy communications. The AN/TB-16A towed array further extended the submarine's passive sonar range, critical for deep-water ASW operations. The AN/BQS-14 ice detection sonar allowed for navigation and operation in under-ice environments.

The *Narwhal's* optical capabilities were provided by a generic submarine periscope (optical) and a generic submarine periscope (LLTV). The optical periscope would have been used for visual observation and targeting in daylight conditions, while the low-light television (LLTV) periscope extended these capabilities into nighttime or low-visibility environments. The AN/BPS-14 surface search radar provided surface contact detection, improving situational awareness in both submerged and surfaced conditions. The AN/BRD-6 direction finding system allowed for precise location of radio transmissions. Finally, the Mk67 torpedo tubes provided the capability to launch anti-submarine or anti-surface torpedoes. The 3-inch signal ejector was used for launching flares and other signaling devices.

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

**SENSORS:** AN/WLR-9A || AN/BQQ-5C(V)2 [BQS-12] || AN/WLQ-4 Sea Nymph || AN/TB-16A || AN/BQS-14 || AN/BPS-14 || AN/BRD-6 || Generic Submarine Periscope, Optical || Generic Submarine Periscope, LLTV

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