Virginia class: The SSN of the future

Intro- USN was forced to reduce the number of most capable submarines to be procured as the cost of constructing and operating them was shooting up. Initial batch of 30 Seawolf would be reduced to just 3, with just 2 dedicated SSNs and 1 special operations sub which would replace the now legendary USS Parche SSN-683. Each of the 2 Seawolf SSNs would end up costing nearly $3 Billion and the spec ops sub would cost more than $3.5 Billion. USN clearly needed a new SSN, something akin the famous Los Angeles off which 62 units were built. The end of Cold War meant that the awesome performance of Seawolf was not needed, performance levels of the older LA were good enough for countering all the subs in service with potential adversaries. More importantly it was needed to fire TLAMs (Tomahawk Land Attack Missile) and upcoming TacTOM (Tactical Tomahawk) for taking out targets on the land, one of the new missions for USN subs which came with the LA flight 2. The new technologies which would go in this sub were decided after the exhaustive studies conducted under the name of “Centurion Studies” in the last decade of the 20th century. The Virginia would thus take shape from the findings of these studies and would step in the shoes of the respected LA class. In this article we will have a look on the Virginia class of SSNs, the ones which will serve USN for decades to come.

960916-V-0000B-009 GROTON, Ct (Sep. 16, 1996) -- The U.S. NavyÕs newest attack submarine, USS Seawolf (SSN 21) conducts ÒBravoÓ sea trials in preparation for its scheduled commissioning in July 1997.  U.S Navy photo courtesy of Electric Boat Corporation by Jim Brennan.  (RELEASED)Seawolf running on the surface

Sitting down and giving a clear thought to what you are going to do in the future is a tried and tested formula applied before taking important decisions.  USN did the same thing from Feb 1991 as part of the Centurion studies. They didnt have a clear idea of what they wanted as this sub would serve in a new age where technology was the mantra of success. They knew one thing for sure that this sub has to be cheaper than Seawolf, yet as quiet and pretty capable and ready for future conflicts. Before deciding the capabilities of the future sub some basic requirements with respect to the Seawolf were put up. They are as follows.

  1. Retain Seawolf quietening,
  2. Reduced maximum speed compared to Seawolf,
  3. Maintain basic capabilities,
  4. Reduced weapons payload compared to Seawolf,
  5. Reduced maximum diving depth compared to Seawolf,
  6. Reduced crew size compared to Seawolf.

With these requirements on their mind, they moved forward to decide the displacement of this new sub. They divided the prospective displacements into 3 bands. They are less than 6000, between 6000-8500 and more than 8500 tonnes. The made several prospective designs in each of the bands and studied their capabilities. Below 6000 tonne was discarded as even with the same quietening as the Seawolf it was deemed too slow and under-armed. Above 8500 was again rejected as it would end up being as costly as the Seawolf itself. The tonnage band between 6000 and 8500 was deemed ideal for the submarine, it offered balanced armament and speed along with the same level of quietening as the Seawolf itself. It was decided to use off the shelf products to reduce costs without compromising on the performance. Another proposal was to use the venerable design on the Los Angeles in the new sub and add these new technologies. It was deemed that this load of new technologies was impossible to integrate into the existing 688I  as it was an old design, past its prime and limited upgrade capability. It was also deemed impossible to integrate all the technologies at once in the new sub at once, from the lead boat itself. Thus a block wise construction under technology insertion programme was selected to avoid rise in costs and get a sub ready for the time frame it will serve in.

SHIP_SSN_Virginia_Class_Cutaway_lg

The programme was renamed to NSSN ie New SSN before being given the official designation of Virginia class or SSN-774. This new sub would have a tonne of novel features which would actually make it state of the art and give other countries a lot to catch up. It made way with traditional periscopes and sports photonic masts instead. This allowed greater quality images to be captured and shared with other assets inside or outside the submarine with ease. It also allowed greater flexibility in placing internal components like the control room. In older subs, it was supposed to be placed directly below the periscopes, but now it could be placed at a more suitable location. The torpedo tube and VLS cells arrangement were taken from Los Angeles class, however the rest of the sub features extensive redesigning. The entire sub was designed using computer aided designing softwares which allowed greater efficiency in designing it. Akin jet fighters, it sports fly by wire, or should I saw dive by wire? This system doesnt allow the sub to wander out of its operational envelope while optimizing its performance . A modified variant of the BSY-1 suite was used to process data from the various sources of information, including the 2 towed sonar arrays, ie variants of TB-16 and TB-29 used on the Los Angeles class SSNs, Wide Aperture Arrays , the bow sonar array, ESM sensors and radar arrays. This greatly increased it combat proficiency.

JAPANSUBS0121408907233Commanding officer of the USS Hawaii uses the digital plot, we can see that the conn (slang for control room) doesnt have the telltale signs of the periscopes and is roomy.

100129-N-3560G-003 PACIFIC OCEAN (Jan. 29, 2010) Lt. j.g. John Sines, left, damage control assistant, and Lt. Andres Aviles, navigation operation officer, scan the horizon through periscopes aboard the attack submarine USS Santa Fe (SSN 763) searching for contacts during a transit of the Pacific Ocean. (U.S. Navy photo by Mass Communication Specialist 2nd Class Ronald Gutridge/Released)Both the periscopes of USS Santa Fe SSN-763 being used simultaneously. The conn appears crowded due to the periscopes. 

This new sub would be powered by the new S9G reactor, with core life of 33 years, thus the sub wouldn’t need refueling throughout its entire life. The reactors through turbines powers a single shaft which turns a pumpjet propulsor. The propulsor greatly increases the maximum silent speed, a speed at which detecting the sub is very difficult. Its length would be 115m, beam 10m and displace 7800 tonnes of water on the surface. It sports 4 torpedo tubes and 12 VLS cells in the bow, akin the LA with around 28 weapons carried internally and 12 Tomahawks in the VLS cells thus a total of 30 weapons. HY-100 steel which is also used on the Seawolf was used to build the the Virginia giving it a similar diving depth of 400m, still less than upcoming Russian sub like the Yasen and Yasen-M. Its weapons payload and dimensions are again very close to those of Los Angeles class, giving rise to a popular opinion that this sub is a LA with extensive redesigning, however we lack any sources which confirm this opinion. I bet everyone has noticed the fillet at the base of its sail. The fillet was added to reduce the flow noises caused by the abrupt change in contour at the base of the sail. It was first used on the Seawolf and now on Virginia, showing the amount of work put on reducing flow noises. The costs also went down over the time, initially it costed $2.4 Billion per boat, which is being reduced to targeted $1.8 Billion over the time.

USS_North_Dakota_(SSN-784)_at_sea_in_August_2014This pic of PCU North Dakota SSN-784 shows the fillet at the junction between the sail and the hull

The first boat, the USS Virginia SSN-774 was laid down at Electric Boat yard on 2nd of September 1999, launched on 16th of August 2003 and commissioned on 23rd of October 2004. SSN 774 submarines are built by General Dynamics-Electric Boat and Huntington Ingalls Newport News Shipbuilding. The latter builds the stern, habitability and machinery spaces, torpedo room, sail and bow. Electric Boat builds the engine room and control room. Both contractors perform work on the reactor plant, final assembly, test, outfitting and delivery of alternate boats. The construction has been divided into blocks. The first 4 subs ie Virginia, Texas, Hawaii and North Carolina were part of the Block I, they took 84 months for completion. The next 6 boats, New Hampshire, New Mexico, Missouri, California, Mississippi and Minnesota for the Block II. They took 69 months for completion and thus were cheaper to build. One Block III sub named North Dakota is under going trials whereas the first Block III boat, John Warner has been commissioned at the time this article was written. Six more subs in the Block III are planned before the construction of 10 boat Block IV starts, followed by a 5-10 Block V. There are speculations that USN might end up procuring a Block VI, VII and even Block VIII Virginia in the future, where as a 774I ie Improved Virginia might be developed in a decade or two.

virginiaFore section of PCU Illinois SSN-786 being transported from one yard to another for completion.

The Block III features a near complete redesign on the bow. The older spherical sonar array is replaced by LAB (Large Aperture Bow) which is roughly triangular. The 12 individual tubes are also replaced by 2 modules having 6 tubes each. This will help reducing the construction costs further as stated by the designers. The Block V features a plug, 21m in length comprising of 4 modules having 7 tubes for Tomahawks. It is called as the Virginia Payload Module and would increase the armament by 28 missiles. This capability would be used to replace the 4 Ohio class SSGNs in service with the USN which are nearing the end of their useful lives.

virginia (2)Shows the difference between the bows of Block II and Block III Virginia class SSNs

Fulldiameterconcept

A conceptual image of what Block V Virginia would look like

Here is a list of its performance parameters.

Displacement

 7900 tonnes

Length  115m
Beam  10m
Max diving depth  ~400m
Propulsion  S9G reactor powering a pumpjet
Speed  Officially 25kn
Crew  135
Armament  ~28 internal weapons + 12 VLS cells
Weapons Carried
  •  Mk48 ADCAP
  • Tomahawk missiles
  • Mines
  • Harpoon AShM
Sonar Arrays
  • Spherical bow array in Block I & II, LAB in Block III
  • 6 Wide Aperture Arrays
  • Chin array
  • TB-16A and TB-29A towed array
  • MIDAS on sail
Extra features
  • Photonic mast
  • UUV capability
  • Pumpjet propulsor
  • Virginia payload module
  • BSY-1 suite
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2 thoughts on “Virginia class: The SSN of the future

  1. Should have looked at the Russian Oscar class. I did a study on repurposing SN688s to cruise missiles. Sublant loved it, but ..politics.

    Ship used the 688 sub with polyurea “saddlebags”, each sub holding 110 tomahawks and 6 trident ballistic missiles ( see Project Hydra ) along with an ASDS, 4 ea 5′ diameter swimmer delivery, assist vehicle and external stores. The fun thing about the design is that the saddlebags can be replaced with SAM, torpedo, mining capability. Lots of capability and can be re purposed easily by changing saddlebags.

    Retired Sr Project Engineer worked on subs my whole career.
    Bimetallic studs that hold the WAAs on is mine, split seal for main feed pumps is mine, 10 patents (3 subs). multiple cable hull penetrator that allowed the SeaWolf sail to Headed the ASHT team for SeaWolf at NNS, headed the internal combustion catapult effort and lots of little improvements.

    Any way, adding plugs looks like more of the same conservative Naval Engeering. Check out the story about the H9 catpult vs steam cats.

    Like

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