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The Kit:
This is a prototype kit (all 3-D printed) of USS Narwhal, SSN 671, developed by Jon Warneke of Iron Shipwrights. The final kit will feature a resin hull and 3-D printed sail, masts, planes, rudders and propeller. The propeller is an excellent rendition of the 7 blade J-type damped screw on the Polaris SSBNs, and the Skipjack, Permit and Sturgeon SSN classes. The kit should be available soon from Iron Shipwrights.
The Submarine:
The USS Narwhal, hull number SSN-671, was a totally unique and experimental nuclear-powered attack submarine and one of the most successful boats of her era. Her unique design made her the quietest attack submarine in the U.S. fleet in the 1970s.
The Navy challenged Electric Boat to build a quieter submarine. A unique design under project SCB 245, Narwhal was her own class. Forward of the reactor compartment she was broadly similar to the contemporary Sturgeon-class submarines, but with a slightly larger diameter to accommodate the natural circulation reactor setup.
Electric Boat identified reduced sound signature improvements. The first was the main reactor coolant pumps. These large, high-pressure pumps spin under heavy load and can be the most significant acoustic source of any nuclear-powered submarine.
General Electric designed Narwhal’s unique S5G power plant with the reactor vessel situated low in the submarine’s hull and the two steam generators situated above the reactor, cocked slightly to fit into the hull. This arrangement facilitated a natural flow of the reactor’s primary coolant. This pressurized-water reactor (PWR) design heated its primary loop in the reactor and convection moved the water into the steam generator near the top of the loop where energy is exchanged into the secondary loop system to generate steam for propulsion. After heat transfer, the primary coolant flows back down towards the reactor vessel in a return loop.
Both initial low power conditions as well as when high power for maximum speed require the reactor coolant pumps. However, there is a wide region of power between these two conditions that allow the main engines and turbines to run normally without the main reactor coolant pumps working.
To address acoustic noise from the standard propulsion turbines which required a large reduction gear system to slow the propeller to usable, efficient turns, a revolutionary, direct-drive main engine turbine that was mechanically linked to the shaft was installed. This system operated at a lower RPM and was larger than the original reduction gear design, 12 feet in diameter and 30 feet in length, resulting in a slightly wider submarine than the Sturgeonclass design, on which Narwhal was based.
The main seawater intake system is used to cool and condense the steam from the drive turbines. Two seawater scoops were added to the stern planes that would force water into the main seawater system as the Narwhal moved forward. During low speed, slow approach operations these scoops moved enough water to cool the condenser loads. Also, new ship service turbine generators which operated at a lower RPM (quieter).
In a subsequent overhaul, sonar was upgraded to the AN/BQQ-5D spherical bow array system along with a long line TB-23 towed array was added on the starboard side, with a deploy tube on the upper stern plane.
The natural circulation reactor design was incorporated into the Ohio SSBN S8G design, as well as the Seawolf class S6W and the Virginia S9G reactors. Other aspects, such as the direct drive turbine were not repeated in subsequent classes. Also, the condenser cooling scoops violated SubSafe principles by having long internal piping runs under sea pressure, so short direct runs with pumps were employed.
This is a prototype kit (all 3-D printed) of USS Narwhal, SSN 671, developed by Jon Warneke of Iron Shipwrights. The final kit will feature a resin hull and 3-D printed sail, masts, planes, rudders and propeller. The propeller is an excellent rendition of the 7 blade J-type damped screw on the Polaris SSBNs, and the Skipjack, Permit and Sturgeon SSN classes. The kit should be available soon from Iron Shipwrights.
The Submarine:
The USS Narwhal, hull number SSN-671, was a totally unique and experimental nuclear-powered attack submarine and one of the most successful boats of her era. Her unique design made her the quietest attack submarine in the U.S. fleet in the 1970s.
The Navy challenged Electric Boat to build a quieter submarine. A unique design under project SCB 245, Narwhal was her own class. Forward of the reactor compartment she was broadly similar to the contemporary Sturgeon-class submarines, but with a slightly larger diameter to accommodate the natural circulation reactor setup.
Electric Boat identified reduced sound signature improvements. The first was the main reactor coolant pumps. These large, high-pressure pumps spin under heavy load and can be the most significant acoustic source of any nuclear-powered submarine.
General Electric designed Narwhal’s unique S5G power plant with the reactor vessel situated low in the submarine’s hull and the two steam generators situated above the reactor, cocked slightly to fit into the hull. This arrangement facilitated a natural flow of the reactor’s primary coolant. This pressurized-water reactor (PWR) design heated its primary loop in the reactor and convection moved the water into the steam generator near the top of the loop where energy is exchanged into the secondary loop system to generate steam for propulsion. After heat transfer, the primary coolant flows back down towards the reactor vessel in a return loop.
Both initial low power conditions as well as when high power for maximum speed require the reactor coolant pumps. However, there is a wide region of power between these two conditions that allow the main engines and turbines to run normally without the main reactor coolant pumps working.
To address acoustic noise from the standard propulsion turbines which required a large reduction gear system to slow the propeller to usable, efficient turns, a revolutionary, direct-drive main engine turbine that was mechanically linked to the shaft was installed. This system operated at a lower RPM and was larger than the original reduction gear design, 12 feet in diameter and 30 feet in length, resulting in a slightly wider submarine than the Sturgeonclass design, on which Narwhal was based.
The main seawater intake system is used to cool and condense the steam from the drive turbines. Two seawater scoops were added to the stern planes that would force water into the main seawater system as the Narwhal moved forward. During low speed, slow approach operations these scoops moved enough water to cool the condenser loads. Also, new ship service turbine generators which operated at a lower RPM (quieter).
In a subsequent overhaul, sonar was upgraded to the AN/BQQ-5D spherical bow array system along with a long line TB-23 towed array was added on the starboard side, with a deploy tube on the upper stern plane.
The natural circulation reactor design was incorporated into the Ohio SSBN S8G design, as well as the Seawolf class S6W and the Virginia S9G reactors. Other aspects, such as the direct drive turbine were not repeated in subsequent classes. Also, the condenser cooling scoops violated SubSafe principles by having long internal piping runs under sea pressure, so short direct runs with pumps were employed.
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