Submarines: Post-Virginia SSN Specifications


December 6, 2023: The U.S. Navy has 22 Virginia Class nuclear attack aka SSN (nuclear-powered attack subs), submarines and is planning to eventually have at least 60 of them. Not all the Virginians will be the same because construction of the first one began in 1999 and it entered service in 2004. Only one or two can be built a year. That means the navy will be building Virginians into the 2040s. Those 2040 Virginias will be quite different than the ones entering service in the 2020s. The navy recognizes this by designating each distinct variety of Virginian with a Block number. Currently the navy is building Block 4 Virginias and the first Block 5s will show up in the late 2020s.

The navy is pushing new technology to its undersea fleet to make it safer, smarter and deadlier, while seeking to develop its next-generation SSN. This decision won’t be made until the 2030s. That enables the navy to determine which new technologies are most likely to work in current and future SSNs. One of the key, and foundational new techs, is AI (Artificial Intelligence), particularly an AI system that can track and evaluate the performance of new systems. Many of the new systems are quite complicated and that makes it more difficult to determine if you have tested a new system sufficiently to validate its usefulness and reliability. There are several capabilities that are critical, including speed which is a major asset for SSNs because they are faster submerged than on the surface. This is due to their unique teardrop shape. Speed is only useful if it gets a well-armed sub where it needs to be to use the many weapons onboard. Finally, the SSN has to be robust and reliable to be available when needed. This includes the ability to remain on patrol for a long time with all capabilities intact.

Among the changes that will have the most impact is moving the Submarine Warfare Federated Tactical System to a cloud-based common computing environment. SWFTS coordinates sub’s sonar, imaging, electronic warfare, and combat systems, ship control, navigation and other new systems as they are introduced. This is where the work on AI is most important because effective AI is the key to this systems coordination working.

The navy believed they had a breakthrough naval weapon with the Block 5 Virginias. Just like the battleship revolutionized naval power a few years before World War I (1914-18), along with ocean-going submarines during that war and, by the 1930s, aircraft carriers, the Block 5 Virginia can carry a lot more guided missiles, high-tech torpedoes, and naval mines than ever before because all these weapons on an SSN have proved to be a decisive weapon. SSNs can travel at high speed underwater to trouble spots and deliver massive firepower before aircraft carriers can. As the Block 5 Virginias begin to enter service, so will a lot of new, or renewed, guided missiles and “smart mines” that became available as the first Block 5s get closer to their first appearance.

The Navy is already spending a lot of money on its new SSNs. The Navy has twenty Virginia class SSNs in service with 60 to 70 or more to be eventually built, depending on how much money is available and how well the substantially improved Block 5 models do. Over the last five years the speed of construction has increased as well as the rate of delivery in order to replace the aging Los Angeles class boats.

Each block of Virginias represents improvements, some of them substantial. There are currently five subclasses of Virginia, each identified by a Block number. There are four Block 1s, all in service by 2008. The six Block 2s were all delivered by 2013. Eight Block 3s were all in service by 2020 and ten Block 4s, with three in service by 2021 and the rest by the mid-2020s. The ten Block 5s won’t all be in service until the early 2030s and future Blocks will be based on the larger and more heavily armed Block Vs.

The Navy currently expects to build 66 Virginias, but the importance of the large and more heavily armed Block Vs may increase that to over 70 subs with most of those based on the Block 5. Blocks 1-4 of Virginia are all armed the same way but eight of the ten Block 5s have additional space to store and launch missiles and can carry 65 missiles and torpedoes, 75 percent more than earlier Virginias. This is accomplished by adding a VPM (Virginia Payload Module) to the current design. This adds 25.6 meters to the length of the sub and increases displacement to 10,400 tons. The VPM adds four more large launch tubes that can hold different sizes of missiles. For example, each of the launch tubes can carry seven Tomahawk cruise missiles or a smaller number of new missile designs in development, like the hypersonic missile. Earlier Virginias have their vertical launch tubes forward of the sail (conning tower). The VPM is added behind the sail. The VPM design was not ready when the first block 5 began construction so the first two Block 5s will lack the VPM and be the same size as earlier Virginias. These two Block 5s will have all the other additional features common to all Block 5s. This includes improved electronics and sensors, and it is believed that the passive sonar in these model Virginias have much longer and more accurate detection ranges. Block 5 will also receive a large number of other equipment upgrades.

The additional missile capacity of Block 5 and subsequent Virginias is also meant to replace the cruise missile capacity being lost as the four Ohio-Class SSGNs (cruise missile carrying subs) are retired. These four boats are SSBNs (ballistic missile carrying subs) that were converted so their 24 ballistic missile launch tubes could carry seven Tomahawk cruise missiles each. Two of the missile tubes were dedicated to carrying navy SEAL gear but the others carried 154 Tomahawks. The success of the Ohio SSGNs led to the VPM, although it will require 22 VPM equipped Virginias to replace the Tomahawk carrying capacity of the SSGNs. This was seen as an advantage because there were few instances where an SSGN had to fire all or most of their Tomahawks. The VPM does not turn Virginia into an SSGN because all Virginias are still attack boats.

The Block 1-4 Virginia's cost about $2.2 billion each. They displace 7,800 tons and are 114.9 meters (377 feet) long and 10.36 meters (34 feet) wide. Top speed is over 50 kilometers an hour, max depth is more than 250 meters (over 800 feet). The Block 1-4 Virginias are armed with twelve Tomahawk cruise missiles (in vertical launching tubes) and four 53.3 cm (21 inch) torpedo tubes that can fire MK 48 torpedoes or naval mines. The Block 5s with the VPM will cost about $3.5 billion each.

More important are the large number of electronic systems carried. These make the Virginias more difficult to detect, which enables these subs to be more effective at espionage and scouting. The electronics can also quickly detect and identify incoming torpedoes and rapidly use countermeasures. The passive (listen only) sonar system is backed by a huge library of sounds. Virginias are also designed to operate in shallow waters and carry a SEAL Delivery Vehicle (sort of a minisub for getting SEALs ashore) outside the sub. With a dozen or so SEALs on board, a Virginia will be carrying nearly 150 people.

Virginia’s nuclear reactors are a new type that does not have to be refueled, having sufficient nuclear material to last 33 years. The reactors generate enough heat to provide 40,000 horsepower, as well as ample electricity for all the electronics. The block 2 models used less costly construction techniques, while the eight Block 3 boats have some design changes and new technology. The most dramatic improvements came with Block 5.

Development of Block 5 was accelerated by the appearance of new weapons for Virginia. In 2018 the navy returned the ENCAP, a cylindrical container in a torpedo tube which is launched and then fires a Harpoon anti-ship missile, to active service. The Navy withdrew the ENCAP Harpoon in 1997 but in 2018 test fired one of them, apparently refurbished for the occasion, and found they still worked as they were supposed to. The ENCAP Harpoons were initially replaced by an anti-ship version of the Tomahawk, which was to be withdrawn but remained in service with more upgrades. With the collapse of the Soviet Union in 1991, the major naval adversary of the United States soon disappeared. The smaller Russian state could not afford to maintain, much less operate, the huge Soviet fleet. Now China is replacing the Soviet fleet as a major naval threat and new ship designs and weapons are back in favor.

By American 1999 subs were just carrying land attack Tomahawks, not just because the Soviet navy was gone but also because for either Harpoon or Tomahawk you have to have a general idea of where the target is before you fire the missile, which has its own terminal guidance system for locating a ship nearby and hitting it. But the subs rely on stealth for protection and that means few transmissions while underwater. For the ENCAP Harpoon, the 1990s passive sonar could, under the right conditions, locate a surface target out to about a hundred kilometers. Half that was needed, in most cases, for the Mk48 torpedo, which also had a terminal guidance system and could, at slow speed, reach a target out to about a hundred kilometers.

Since the 1990s there have been major improvements in the passive (just listening) sonar the subs use most of the time, as well as the tech used for a submerged sub to receive, or less frequently send, electronic information. When receiving data, the sub does not reveal its position to anyone monitoring that area of the ocean for transmissions. Sending data, even briefly, exposes the sub’s general location to being discovered.

Subs now have many more “periscope” capabilities. The conventional optical periscope has been replaced by devices that can be sent to the surface tethered by cable. These tethered devices can receive satellite and other electronic messages, as well as send. That means a sub could send up its satellite signal receiver many times a day when in a combat zone to receive updates on enemy activity. These could include firing orders for distant ships or land targets to be fired on using missiles. The latest version (Block II+ER) Harpoon has a 300-kilometer range and much better terminal guidance and countermeasures. But it is still a slow, at 800 kilometers an hour missile while the most modern anti-ship missiles have terminal attack speeds of more than three times that. Then again, for a surprise attack Harpoon can be useful as it comes in very low, sea skimming mode and often avoids enemy radar. One possible situation would have an enemy ship be detected by satellite or UAV with location information sent to an SSN within Harpoon range, or able to move into range where it could fire one or more ENCAP Harpoons and then go hide. ENCAP Harpoons blasting from the sea surface makes a lot of acoustic and visual noise. Another option is the ENCAP UAVs proposed for subs. These can be launched more quietly and spend several hours searching an area for any targets and sending the sub brief message bursts with the location of any targets. One version of ENCAP UAV was developed that be launched from the smaller countermeasure launchers,

The navy is not spending a lot of money on bringing the ENCAP Harpoon back into service. It is going to upgrade some older Harpoons and ship them as ENCAP weapons for possible use under the right conditions. The navy, as expected, isn’t providing details and the details may involve some new tech or tactics that are best kept secret.

Another new weapon is the Hammerhead mobile mine. Hammerheads are encapsulated bottom mines that use a Mk 54 lightweight torpedo, which is normally carried by ASW helicopters and aircraft. Mk 54 has a range of ten kilometers and a guidance system that is regularly updated. Hammerhead is being used in a similar fashion to a larger version of this used during the Cold War that was deployed by surface ships and used the larger Mk 48 torpedo. In 1983 the navy introduced an earlier version of the Hammerhead concept as the Mk 67 SLMM or Submarine Launched Mobile Mine that carried the older Mk 37 torpedo. The Mk 37 was a late World War II design that was used into the 1970s. By 1987 there were still some in storage and they were adequate for SLMM. The SLMM was out of service by the 1990s with the end of the Cold War. Hammerhead is an encapsulated system equipped with improved passive sensors to detect and identify submarines and surface ships and attack specific types of targets, like diesel-electric subs or larger warships or commercial ships. Hammerhead is not only being carried by the Virginias, especially the Block 5, but also by the new Orca autonomous diesel-electric sub that can carry and deploy a dozen Hammerheads.

The U.S. currently has three classes of SSN. Most are the 6,900-ton Los Angeles-class SSNs. Sixty-two of these submarines were built and 26 are still in service. Armed with four 53.3 cm torpedo tubes, they carry twenty-six weapons for those tubes, either the Mk 48 torpedoes or BGM-109 Tomahawk cruise missiles. The last 31 Los Angeles-class SSNs added the Mk 45 VLS vertical-launch system, which carried another twelve Tomahawks. If built today these late model Los Angeles class boats would cost about $1.5 billion each. The first of these entered service in 1976, and the last one in 1996. These boats can last 30-35 years before they must be retired or undergo extensive repairs, as in over half a billion dollars’ worth of refurbishment and refueling. This can take 4-5 years and will keep the sub going for another 10-15 years. But there’s barely enough money to keep building Virginias and no time or cash to refurb elderly Los Angeles class boats. That was why the number of Virginias planned was increased to 66 and the tempo of construction speeded up. This means the American SSN fleet will not shrink from 55 in 2013 to under 45 by 2030. The current building plan keeps the SSN numbers at or above fifty and, with all of the new Virginias based on the Block 5s, the new SSN fleet will be a lot more capable than the old one.

The first attempt at upgrading the SSN fleet failed. Twenty-nine 9,000-ton Seawolf-class SSNs were supposed to replace the Los Angeles boats but Seawolf proved too expensive. Only three were built. The Seawolf was designed for the Cold War, carrying fifty weapons including torpedoes, cruise missiles, or Harpoon anti-ship missiles for its eight 660 mm (26-inch) torpedo tubes. Seawolf was fast with a top speed of over 60 kilometers an hour and much quieter than the Los Angeles boats. The Virginia-class was designed to replace the un-built Seawolves. Think of it as a Los Angeles size hull with a lot of Seawolf technology installed. The Virginia class boats ended up costing about half as much as the Seawolfs even though the Virginias used a lot of the new technology developed for Seawolf.

There were also crew problems with the SSN force. An investigation report into the 2021 collision of the Seawolf-class Connecticut SSN revealed problems with crew training. That began with revised navigation training of officers and senior NCOs on nuclear subs as well as implementing more intense scrutiny of how well that training is done. This includes more frequent checks on how effective the training is over time.

The October 2021 Connecticut incident was the second American SSN to suffer an accident involving collision with a seamount in the last fifteen years. The leadership of the Navy SSN force realized they had a serious problem. In mid-November 2021 the commander of subs based in the Pacific agreed that an emergency stand-down or halt in regular operations to assess the state of navigation training among SSN crews was in order. At that time of the Connecticut collision, the investigation was not yet complete but enough was known to attribute the collision to poor training and supervision of the officers and sailors who handle underwater navigation.

When Connecticut collided with an underwater seamount, its damage was so severe that it had to surface immediately. The ballast tanks were damaged so the sub could not remain underwater. It was also feared that there might have been a radiation leak but none of the radiation monitoring sensors on the sub detected any. The navy relieved the captain of the Connecticut along with the executive officer (second in command), and the COB (Chief of the Boat, the senior NCO on the sub). These key personnel were relieved because of poor navigation procedures and the failure to train the crew to do it right. Now the submarine command wanted to find out the extent of the problem by similarly scrutinizing the status of navigation training and capabilities on all SSNs.

The first such collision occurred in 2006 and the reason was a lack of updated charts, which are nautical maps showing underwater obstacles, on all SSNs in 2006. That was thought to be remedied after the 2006 collision and all ships are supposed to have the electronic charts that are part of the new VMS or Voyage Management System that not only uses electronic copies of charts, but quickly updates charts when new underwater obstacles are detected. This is done via space satellites or various seagoing data collection systems. In 2016 the navy installed a new version 9.3 VMS system in American SSNs, and it was eventually discovered that this was not an issue with the Connecticut. Crews are given initial training on these new systems before they depart on a cruise. The two senior officers, and especially the COB, are responsible for ensuring that all sailors involved with navigation are properly trained to handle the VMS and the new charts. By the end of 2021 the navy admitted that the Connecticut’s damage was extensive, and Congress agreed to provide $50 million for replacement components that must be manufactured, a process that could take months or longer. It is still unclear if the damage done is so extensive and expensive to fix that the navy budget might not be able to handle it. That could force the navy to retire the Connecticut.

The earlier collision of the USS San Francisco caused similar damage but was cheaper ($80 million) and easier to fix because the San Francisco was a Los Angeles class sub and many of those were being retired because of age. The San Francisco was not due to retire until 2017 because it had recently undergone a $170 million refueling and refurbishment. The navy did the math and realized that another Los Angeles class sub, four years younger than the San Francisco, was about to undergo a similar refurbishment. It was cheaper and faster to remove the forward portion of the younger sub and use it to replace the damaged portion of the San Francisco.

This approach would not work with Connecticut because it is a Seawolf class sub and there are only three of those. Connecticut entered service in 1998 and was expected to remain in service into the 2030s. The Seawolfs are larger and more capable than the Los Angeles class but too expensive to build in large quantities, so only three were built. Many of the innovations found on the Seawolfs were transferred to the smaller, more affordable Virginia class. This was a success and 66 are planned with 22 already in service.

The three Seawolfs were kept in service because they were already paid for and turned out to be quite effective. The new tech making that possible was now tested and it made the smaller Virginias much more effective, and not much more expensive than the Los Angeles class boats the Seawolfs were originally supposed to replace.

The Seawolfs themselves were another example of poor navy leadership in the key area of developing and building new ships. The Seawolfs were the first of a series of similar disasters that included the Zumwalt destroyers and the LCS frigates. Spending a lot of money to save Connecticut is not something the navy can afford anymore. The only exception is the third Seawolf, USS Jimmy Carter, which was heavily modified to become a longer, heavier, and unique intelligence collection sub. The Carter, which entered service in 2005, was a success in performing unique intel missions. The other two Seawolfs are not unique and useful, which makes them more likely to be retired early if unexpected and expensive-to-fix problems arise. This is what the navy is doing with many recently built but flawed LCS class ships. Connecticut now has a very expensive hardware problem and, like the LCS ships. is in danger of just being retired because of cost considerations.

Despite the greater capabilities of the Seawolf, the Connecticut collision demonstrated that crew quality is still a major factor. As much as the navy would hate to lose a Seawolf, the demise of the Connecticut makes it clear that crew quality is even more important and is not something you can build into a new ship. Crew quality is easier to misplace than ship quality and cost because the hardware cost is easier to demonstrate and justify.




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