what would become of an attack submarine? What would it look like when constructed not so much to fight torpedoes but to get down and play with the sea?
The USS Jimmy Carter (SSN-23) sitting at the center of USS Jimmy Carter is the most extensively altered Seawolf-class boat in the U.S Navy and a platform, in an informal setting, commonly referred to as a nuclear “spy submarine”. In contrast to most fast-attack submarines, which are designed with employment of forward weapons and high-speed maneuver, Jimmy Carter was designed to render the undersea environment an operational place, rather than a transitional place. The outcome is a submarine that fills a gap in the fleet that is not filled out in detail even as official characterizations of attack submarines talk of intelligence gathering, Special Operations support, and mine warfare being fundamental SSN missions.
The Multi-Mission Platform is the hull extension 100 feet long that Jimmy Carter introduced, a 100-foot hull extension known as the Multi-Mission Platform that Navy describes as a 100-foot hull extension known as the multi-mission platform that would have additional payloads and new technology to do classified work. The engineering implication is easily seen: increased volume of mission equipment, increased internal routing of power and services, and special areas where anything hard to perform in the cramped, weapon-centric geometry of a conventional SSN can be done at full scale. This is not simply “extra room.” It is a purposely unbalanced redirection of the internal real estate of the submarine towards interfaces and handling equipment and mission management areas responsive to the offboard systems and specific teams.
Within that extension is the part that makes the boat look like an undersea workshop that has been made: an “ocean interface”. Practically, it enables the submarine to launch and retrieve divers and remotely-operated vehicles, without relying on torpedo tubes. The design has been said to be a “wasp waist” design-a smaller passage of pressure-hull which joins the front and rear parts of the submarine yet surrounding spaces can be flooded and provides a controlled environment to deal with equipment in the sea. Such an architecture is important as it alters the working rhythm of the submarine: the payloads can be staged, tended and cycled without posing as directly as weapons loading, the congestion of the torpedo-room or the constraints of normal lockout trunks.
The other half of the equation is station-keeping. Jimmy Carter is equipped with aids to manoeuvre which allow it to hold station at a point in the seabed within complicated currents which are needed to conduct operations within fixed infrastructure and fine positioning. Wikipedia observes that the boat has other maneuvering equipments installed at the front and back to maintain position over desired targets. This in engineering terminology is not really about high-end speed but rather about fine control, which is an underestimated need should the mission be flying on top of cables, sensors and seabed equipment where meters count.
All of this does not exist in vacuity. Purpose-built submarines have been designed by the U.S. Navy previously, with one such example being the NR-1, a nuclear-powered midget submarine that pushed the concept of accessing the seabed to its boundary. NR-1 had a potential top depth of 724 meters (2,375 ft) underwater, and it drove on the bottom of the ocean using wheels and used manipulator arms to collect items- a strategy that focused on mechanical engagement and salvage. Jimmy Carter is another philosophy: start with a front-line SSN hullform and replace the aft with a modular, floodable mission bay that can accommodate divers, vehicles and payloads, and still have the same baseline performance as the Seawolf class.
Performance does not go away since special missions boats should not be detected before arriving, loitering, and leaving. The Seawolf lineage is linked with high speed and deep-diving margins and popular discourse tends to provide examples of speeds of Seawolf-class, in the mid-20-knots range or higher. The best feature of Jimmy Carter, however, is more than any single number; the seabed has been transformed into navigable terrain by an engineered section in the shape of an “ocean interface”.
The number of Seawolf-class submarines available to serve, and only one of them outfitted in this manner, means that Jimmy Carter is one of the few instances where a navy decides to design a submarine based on the mechanics of covert undersea access as opposed to an improvised addition to it.
