Though Russia continues to develop and build newer and ever more capable nuclear attack submarines such as the Project 885M Yasen-class, the U.S. Navy continues to maintain its technological edge by incrementally improving its Virginia-class attack boats.

“I think we have a very focused program called the acoustic superiority program to make sure that we in fact keep our technological lead—our acoustical advantage—and that's a focus of every one of our developmental programs,” Capt. Mike Stevens, Naval Sea Systems Command’s Virginia-class program manager told me at the Navy League’s Sea, Air and Space symposium on May 17. “It doesn't do any good to build submarines that aren’t up to par, so it’s a main part of our focus to make sure those submarine do maintain their acoustical advantage—not just today but 10, 20 years out.”

Indeed, while the highest profile planned improvement to Virginia-class boats is the addition of a new payload module that boosts the vessel’s Tomahawk missile capacity to 40, there are a host acoustical improvements to boats that are ongoing. “Acoustics are an essential element of a submarine,” Stevens said. “Stealth is the main aspect we focus on, so we always—from ship to ship even—we look at the acoustic health and make sure  we’re doing what we can improve it.”

Those modifications are often retrofitted to older vessels in the class where possible—but not always. However, Stevens explained iif the Navy does find a significant acoustical breakthrough, the service will make every attempt to retrofit older boats. Indeed, while the Navy used the Virginia-class as the basis for the Ohio Replacement Program, many of the technologies developed for the new ballistic missile submarines will eventually find their way back to the later Blocks of the Virginia-class.

Modern submarine design is an evolutionary process. The latest  Block V Virginia-class boats—which are the first to incorporate the Virginia Payload Module—will be some 83-feet longer than their predecessors as a result of the new missile compartment when the first boat starts construction in fiscal year 2019. Along with the increased length comes significantly greater displacement, however the performance degradation is minimal and the boats will meet the Navy’s requirements bandwidth even without modifications to the powerplant and other ship systems. “It’s in the bandwidth of our requirements,” Stevens said. “We exceeded that on our initial submarines, now we’re still going to be in that bandwidth, but little bit less.”

But that’s just the most visible improvement. There are a host of less obvious modifications to the submarine that will help to maintain its technical edge. Indeed, future Virginia-class Blocks will eventually form the basis of the next-generation SSN(X) replacement for current boats, Stevens said. That’s a pattern that’s been laid out for decades. Stevens noted that late-model Improved Los Angeles-class boats trialed many of the technologies for the Virginia-class and he expects that pattern to continue. “The Virginia-class leveraged a lot of technology from the last few 688s that were developed with the next class in mind,” Stevens said. “We’ll do that same thing.”

However, while America’s submarine fleet maintains its technical edge, the submarine fleet is too small. The Navy will need more attack submarines to counter a resurgent Russia and growing Chinese subsurface fleet.

Dave Majumdar is the defense editor of The National Interest. You can follow him on Twitter @DaveMajumdar.