Cracking the Line

Today we are honored to have a guest post from regular reader and contributor, Mr. Bustamante, who discusses the role of guided missile submarines in A2/AD scenarios.  You may recall his previous post, "Myth of the Unopposed Landing".  Read and enjoy!

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Cracking the Line

The Case for Guided Missile Submarines in Anti-Access and Area Denial (A2/AD) Scenarios

“But things have changed… the resurgence of Russia and the ascendance of China, both of which are producing numerous submarines, and in particular in Russia’s part, extremely capable submarines… we’re facing challenges of both quantity and quality from our competitors (1).

- Rear Admiral Michael Jabaley

War is a numbers game, even the peacetime deployments obey the rules of math; the challenge is that our submarine force numbers are inadequate and will further decline to approximately 41 boats by 2029 (2).  Projected wartime demands of submarine force call for approximately 35 operationally ready SSNs, in turn requiring 48 boats simply to ensure that 35 will be available (3).  Exacerbating the numerical shortfall is the proliferation of sophisticated anti-access and area denial (A2/AD) defenses, which present a lethal zone of land based maritime strike (aircraft, cruise, and ballistic missiles), sophisticated air defenses, and mines.  These A2/AD defenses can extend from 1,000 to 1,500nm offshore and the most viable naval counter is the submarine launched cruise missile.  However, our navy also faces loss of submarine cruise missile delivery capacity due to the retirement of the four Ohio-class guided missile submarines (SSGNs) without replacement (4).  It is worth noting that our submarines are expected to shoulder the high priority ASW mission, and also enable USAF bomber and naval strikes with cruise and missile strikes to defeat sophisticated anti-access and area denial (A2/AD) defenses.  Nor does this represent the full scope of submarine missions (5). 

There are several potential solutions if we desire a larger submarine force:

1.  Build more submarines.  Current shipyard capacity appears to be limited to at most three nuclear-powered submarines a year.  Even if budgets permit; there are only two shipyards in the country capable of building nuclear-powered ships and it is unlikely that construction rates can be increased without significant capitol infrastructure investment (6).  Nuclear submarine production capacity is also constrained by the requirement to build replacement SSBNs for our strategic forces to replace the aging Ohio class, as well as nuclear powered aircraft carriers.  Finally, a new construction SSGN, while highly desirable, is likely to be secondary in priority to the replacement SSBNs, 12 of which will be built before any new construction could start.

2.  Service Life Extension (SLEP) existing SSNs, if possible.  This alternative is a huge unknown and will require analysis of each SSN to determine the engineering and economic feasibility.

3.  Augment our SSN force with advanced Air-Independent Propulsion (AIP) submarines (SSKs) converted into SSGs by installing a hull section with at least 12 (or more) vertically launched missile cells (VLS) to address the land attack mission (7).  This could be done by purchasing the building rights (or outright buy) submarines from our allies.  

To be clear, the SSG is not a replacement for the SSN.  Furthermore, the U.S. should build SSNs at maximum shipyard capacity for the foreseeable future.  SSNs retain vital endurance and high submerged speed operational capabilities vital for open ocean operations.  These advantages allowed, diesel electric SSKs have always been the stealthiest of submarines within the constraints of battery power, making them highly survivable.  Modern SSKs have maximum submerged speeds exceeding 20 knots, and the ability to travel very long distances using fuel efficient diesels.  With the advent of Air-Independent Propulsion (AIP), SSKs now possess optimal survivability, submerged endurance, and speedto penetrate sophisticated anti-access and area denial (A2/AD) defenses owing to the research going into AIP technologies including: fuel cells, Stirling cycle engines, and Module d'Energie Sous-Marine Autonome (MESMA) (8).  Table 1. Follows and includes pertinent open source information comparing a modern SSN with competing SSKs:

Table 1. Submarine Characteristics Compared

Source: survey of current defense literature.

Further points in favor of the SSG are a comparatively low procurement cost of ~$600 million per boat (before installation of a Vertical Launch System), and reduced manning roughly 33% to 50% of the SSN crew requirements. Critically, AIP submarines can be massed produced: ThyssenKrupp Marine Systems GmbH (Howaldtswerke-Deutsche Werft GmbH) claimed to have nine submarines under construction or being upgraded at its Kiel facility, a vital capability in war (9).

Penetrating an A2/AD defense to launch strikes will require that our SSG get to a firing position within 750 nautical miles or so of an enemy coast.  We must assume that AIP propulsion must be used within the A2/AD zone, as a snorkeling SSK is vulnerable to detection and destruction by Maritime Patrol Aircraft (MPA); this will reduce submerged transit speeds to 6-8 knots.  At 6.5 knots, a modern AIP submarine can travel about 156 nautical miles submerged each day, so it will take five days for an SSG to travel from a position outside a 1,500 nautical mile A2/AD zone to a cruise missile launch point within 750 nautical miles of the coast (10). 

In the end, the argument in favor of the SSG is not about optimum capability, but instead on procuring sufficient numbers of viable boats to round out the submarine force in the strike warfare mission.  Further improvements in batteries and AIP seem likely to improve the capability of submarines.  The AIP equipped submarine, operated by many potential adversaries, also makes an incredibly useful training asset for our navy to train against. Configured with VLS, the SSG is now an absolutely credible solution for strike warfare (land attack), commerce raiding, offensive mining, and ASW. 

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(1)Congressional Research Service report RL32418, Navy Virginia (SSN-774) Class Attack Submarine Procurement: Background and Issues for Congress, April 14, 2016, by Ronald O'Rourke, pg. 14.

(2)“The Navy’s FY2017 30-year SSN procurement plan, if implemented, would not be sufficient to maintain a force of 48 SSNs consistently over the long run.  The Navy projects under that plan the SSN force would fall below 48 boats starting in FY2025, reach a minimum of 41 boats in FY2029, and remain below 48 boats through FY2036.” Congressional Research Service report RL32418, Navy Virginia (SSN-774) Class Attack Submarine Procurement: Background and Issues for Congress, April 14, 2016, by Ronald O'Rourke, summary page. 

(3)“The peak projected wartime demand of about 35 SSNs deployed within a certain amount of time … is an internal Navy figure that reflects several studies of potential wartime requirements for SSNs.”  Congressional Research Service report RL32418, Navy Virginia (SSN-774) Class Attack Submarine Procurement: Background and Issues for Congress, April 14, 2016, by Ronald O'Rourke, pg. 11.

(4)“From FY2026 through FY2028 the Navy will retire its four Ohio-class guided missile submarines (SSGNs).  Each SSGN can carry a maximum of 154 vertically launched BGM-109 Tomahawk cruise missiles per boat, seven (7) Tomahawk cruise missiles in 22 large-diameter vertical launch tubes (two (2) of the 24 tubes cannot carry the missiles).  The four SSGNs can carry a combined total of 616 vertically launched Tomahawks.  The navy plan is to build Twenty-two Virginia-class boats built with Virginia Payload Modules (VPM) to carry a combined total of 616 Tomahawk missiles.  This plan better distributes the cruise missile across the submarine force, but these same submarines will have many competing tasking’s and the impact of VPM on operational characteristics of SSNs cannot be stated due to classification.”

(5)Additional missions include: Intelligence, surveillance, and reconnaissance (ISR); offensive and defensive mine warfare; anti-submarine warfare (ASW); and anti-surface ship warfare.

(6)Virginia-class boats are built jointly by General Dynamics’ Electric Boat Division of Groton, CT, and Quonset Point, RI, and Huntington Ingalls Industries’ Newport News Shipbuilding, of Newport News, VA.

(7)For comparison, the SSN 688 and 774 class nuclear-powered attack submarines (SSNs) employ a 12-cell VLS for Tomahawk missiles.  Additionally, the Navy is planning to add Virginia Payload Modules (VPM) to the SSN 774 block 5 SSNs - the additional launch tubes in the VPM could carry a total of 28 additional Tomahawk cruise missiles (7 per VPM), which would increase the total number of torpedo-sized weapons (such as Tomahawks) from 37 to about 65.

(8)Manufacturer claims must be taken with great skepticism, but German, Japanese, and Swedish firms are now claiming submerged endurances exceeding 10 days at sustained submerged speeds in excess of 6.5 knots using Air-Independent Propulsion!

(9)‘Why German company ThyssenKrupp Marine Systems wants Australia’s Future Submarines contract’, by Ian McPhedran May 21, 2015.

(10)This figure is somewhat arbitrary and it is based upon a cruise missile with approximately 1,000 nm range (e.g. the UGM-109 Tomahawk variants).  The 750 nm, allows for deep inland strikes.  Wayne Hughes, Capitan USN (RET) presents additional tactical scenarios in his book: “Fleet Tactics and Coastal Combat.”  Andrew F. Krepinevich, Jr. of the Center for Strategic and Budgetary Assessments has also written numerous papers with useful scenarios.

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Mr. Bustamante is a retired naval officer who served the majority of his career as a Naval Special Warfare Officer and also served as a Surface Warfare Officer and Foreign Area Officer.  He is a graduate of the U.S. Naval Academy with a degree in Systems Engineering.  He also holds a Master of Science degree in Defense Analysis (Operations Research) from the Naval Postgraduate School in Monterey, California. After retiring from the Navy, Mr. Bustamante worked for the legislative branch as an auditor and analyst, as a civil servant with the United States Department of State, and also in the private sector as an analyst in information technology project management.

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