Source: USNI, US Navy, MIT
The US Navy is building an upcoming Virginia-class attack submarine, the future USS South Dakota (SSN-790), with acoustic superiority features for the fleet to test out and ultimately include in both attack and ballistic missile submarines in the future.
Richard said the under-construction South Dakota will feature a large vertical array, a special coating and machinery quieting improvements inside the boat. The boat is on track to deliver early despite the changes, he said. Once South Dakota joins the fleet – in 2018, according to the boat’s commissioning committee – lessons learned from the acoustic superiority features will help inform enhancements built into future Virginia class boats and the Ohio Replacement Program boomers, as well as the legacy Ohio-class ballistic missile subs and some Virginia-class boats.
“Stealth is the cover charge, stealth is the price of admission, and while we have great access now we don’t take that for granted either,” Richard said.
“Making the right investments to maintain acoustic superiority over a potential adversary” is of high importance to the Navy today, and the South Dakota project represents “a clear national investment in acoustic superiority.”
Program Executive Officer for Submarines Rear Adm. Michael Jabaley told USNI News in a March 3 interview that acoustic superiority items, some of which will be built into the ship and some of which will be added during the ship’s post shakedown availability, “will kind of become the standard for what we do in various forms between Ohio Replacement, future Virginias and even backfit some on the Ohios and some of the delivered Virginias to make sure that submarine force is pacing the threat of these new highly capable submarines that are being delivered” from other navies like Russia and China.
Jabaley added that as the Navy looks at its next class of attack submarines, the SSN(X), stealth will be a key factor in the design and could lead to the Navy selecting an electric drive or other advanced propulsion system to eliminate as much noise as possible.
“I’m not just talking about the propeller or propulsor, it’s the whole propulsion system from power generation to motion through the water,” he said in the interview.
Electric drive is a propulsion system that uses an electric motor which turns the propeller of a ship/submarine. It is part of a wider (Integrated electric power) concept whose aim is to create an “all electric ship”. Electric drive should reduce the life cycle cost of submarines while at the same time improving acoustic performance
The British Royal Navy Successor submarine (the class replacing the Vanguard class SSBNs) state that the submarines may have submarine shaftless drive (SSD) with an electric motor mounted outside the pressure hull. SSD was evaluated by the U.S. Navy as well but it remains unknown whether the Ohio class replacement will feature it. On contemporary nuclear submarines steam turbines are linked to reduction gears and a shaft rotating the propeller/pump-jet propulsor. With SSD, steam would drive electric turbogenerators (i.e., generators powered by steam turbines) which would be connected to a non-penetrating electric junction at the aft end of the pressure hull, with a watertight electric motor mounted externally (perhaps in an Integrated Motor Propulsor arrangement), powering the pump-jet propulsor, although SSD concepts without pump-jet propulsors also exist. More recent data, including a Ohio Replacement scale model displayed at the Navy League’s 2015 Sea-Air-Space Exposition, indicates that the Ohio Replacement will feature a pump-jet propulsor visually similar to the one used on Virginia class SSNs. The class will share components from the Virginia class in order to reduce risk and cost of construction.
The British Royal Navy Successor submarine concept also includes a next-generation Naval Propulsion Plant, with extensive passive features and designed for disposal; extensive use of automation for submarine control, damage control and condition monitoring; full electric propulsion with shaftless drive; externally mounted tactical weapons; electrical actuation of control surfaces; and replacement of obsolete technologies with military and commercial off-the-shelf equipment.
The Advanced Hull Form submarine concept uses modular design techniques and advanced hydrodynamics to create an unorthodox external hull form, which offers enhanced signatures, manoeuvring and safety, and large volumes for payloads and equipment outside the pressure hull. This gives exceptional flexibility in design and operation, with the maximum opportunity for rapid role change or upgrading.
The Advanced Hull Form has been designed for low-cost fabrication using largely flat or single curvature surfaces. This approach also allows rapid repair and modification, giving the basis for a flexible, economical and resilient platform.
The US Navy is researching advanced propulsion and ship concept developments.
Shaftless Propulsion and Radical Ship HM and E Infrastructure Reduction. Develop submarine alternative propulsion and stern configurations with potential to significantly reduce submarine acquisition costs. Demonstrate critical performance parameters through appropriate scale demonstrators in realistic environmental conditions. Evaluate integration of technologies and approaches for cost reduction in future submarines. Develop understanding of ship concept studies and submarine cost drivers and model analysis. Develop and demonstrate technologies for future submarines in areas of hull and platform technologies, propulsors, ship control, electric actuation, sensors, and self defense.