From the Nautilus (SSN-571) to the New Attack Submarine (NSSN), almost every U.S. submarine has incorporated an existing power plant or one under development. The U.S. Navy needs to design a submarine plant to meet a mission profile. We may be presented with a hiatus of several years between fourth- and fifth-generation Russian SSNs—which may be quieter than our Sea- wolf (SSN-21) and NSSN—we should take advantage of this fortuitous interval to get our own design house in order.1 The best approach is through the development of submarine prototypes, designed to satisfy operational requirements.
There have been two golden ages of submarine design:
- In 1926, the Submarine Officers Conference was set up to advise the Chief of Naval Operations and Secretary of the Navy on submarine matters. At this time, Andrew McKee, an ingenious naval architect, came to the Bureau of Construction and Repair (which, with the Bureau of Engineering, became BuShips in 1940). This combination of operational experience and design expertise resulted in design and construction of an extraordinary prototype, the Dolphin (SS-169), forerunner of the Fleet Type Submarine, one of the most successful boats of all time.
- The second golden age, which ran from about 1946 to the early 1960s, was led by a brilliant and imaginative group of engineering duty officers. These naval architects enhanced McKee’s legacy by introducing advancing technology to the Fleet. In the late 1940s, a body-of-revolution submarine design (a near ideal hull shape) was conceived and became the Albacore (AGSS-569), which was destined to change the art of submarine building. Nuclear power came of age with the delivery and sea trials of the Nautilus in 1955. By 1959, the Barbel (SS-580) and Skipjack (SSN-585) were in service, the first body-of-revolution diesel-electric and nuclear-powered fighting submarines, respectively. The Thresher (SSN-593), the first quiet attack SSN, was commissioned in 1961.
Belief in the efficacy of prototypes dates from the early part of the 20th century. Admiral Sir John Fisher, while First Sea Lord, wrote: “The submarine is the weapon of the strong—that is if they are sufficiently developed and diversified and properly applied—but you must have quantity and multiplicity of species.”2
During the 1950s, with technical guidance from the Ship’s Characteristics Board, the U.S. Navy produced seven unique prototypes. The trend away from submarine prototypes toward long production lines of the same hull started in the 1960s and continues to this day. Nearly every SSN has been built to fit a power plant, usually a restraint. Without prototypes, each new class is a compromise.
Today, the process of designing and building submarines is complex, costly, and slow. Project supervisors seem to be more concerned with management techniques than with an appreciation of technical and operational concepts. There is an urgent need to revitalize our approach to submarine design and construction.
Concept Formulation Versus the Los Angeles Class
In 1967, a glimmer of hope for competitive prototypes emerged during discussions of a successor to the Sturgeon (SSN-637)-class submarine. Concept Formulation (Con-Form), a little-known submarine design project, was created in NavShips under the leadership of Captain Donald H. Kern. More than 300 people (including Electric Boat designers under J. V. Leonard) eventually contributed to the project.3
The systematic analysis that preceded consideration of design characteristics for the new SSN included the production of a Submarine Data Book, which compiled the characteristics of all prototypes and first-of-class submarines designed and built since the Albacore. In addition to traditional dimensions, it included weight accounts by group as a percentage of normal surface condition, volume and cost accounts, RPM, and propulsive coefficient. Heat balance and distribution of power from the reactor also were accounted for. For the first time, it was possible to look at one document and see all characteristics. Banks of data were compiled based on operational power-level histories, excursions to test depth, and analysis of major casualties at sea.
ConForm was not a single prototype design, but an attempt to examine a range of submarine design concepts.
Admiral Hyman Rickover, who had absolute control over nuclear propulsion plant design, also was working on a prototype (Fast SSN), using a modified surface reactor design, which became S6G. The design outcome of the ConForm analyses and Rickover’s fast prototype both could have been ready for construction in 1971. Two prototypes could have emerged and competed, but it was not to be.
On 8 March 1968, during congressional hearings, Chief of Naval Operations Admiral Thomas Moorer established an ad hoc panel “to conduct an evaluation of the military characteristics of the [fast] SSN.”4 This panel devised the specifications of what was to become the Los Angeles (SSN-688).
Dr. John Foster, then director of Defense Research and Engineering, originally had visualized concept formulation as a basis for creation of an effective new SSN design. The perennial problem was the choice of a power plant. Nearly every nuclear submarine hull in the U.S. inventory had been forced to fit a propulsion plant specified by Admiral Rickover, whose rapport with powerful committee chairmen in Congress is legendary. The spirited hearings before the Senate Preparedness Investigating Subcommittee in March 1968 resulted in defusing Dr. Foster. ConForm was killed when Foster refused to approve two prototypes.5
One of the more attractive ConForm options included a natural circulation reactor, geared turbine drive, and contra-rotating propellers. Such a design would have:
- Achieved speeds comparable to SSN-688
- Maintained the depth capability of the Permit (SSN-594) and Sturgeon
- Been built with weight reservations that would have enhanced future alterations
- Had a much more favorable length-to-diameter ratio
- Been less expensive
Submerged Resistance and Maneuverability
The optimum length-to-diameter ratio for minimum resistance of a body of revolution, either airship or submarine, is about 6.6 Practical considerations (e.g., draft limitations) favor a ratio larger than 6 for a naval submarine. All cross sections of the hull of a body-of-revolution submarine are circular, and the teardrop shape usually includes a cylindrical section in the middle.7 The best length-to-diameter ratio so far for a U.S. fighting submarine was that of Barbel. 7.6. The Skipjack had a ratio of 7.9. The Albacore introduced the X-stern—adapted to naval submarines by Sweden, Germany, and The Netherlands—which greatly improved maneuverability. The Albacore’’ s turning diameter was 165 yards, compared to 340 yards for the contemporary Tang (SS-563).8
Table 1 illustrates the growth in size of attack boats over the years. Generally, submerged displacements are increasing and length-to-diameter ratios are not improving. This has an adverse effect on maneuverability, which is crucial to operations, especially in shallow littoral waters. None of our attack boats can bottom safely, a capability that has been mentioned as required with regard to littoral operations.9
The Future
The 637 class probably was the last truly effective multimission submarine built by the U.S. Navy. NSSN cannot do all things well, even with modularization. It will be 17 feet longer than SSN-688 and has a length-to-diameter ratio of 11.1. The stem is cruciform. Maneuverability in shallow water will be far from optimum.
Table 1: Growth of U.S. Nuclear Attack Submarines* | ||||||
Class | Delivery Date | Length (feet) | Diameter (feet) | Length/ Diameter Ratio | Submerged Displacement (tons) | Number Authorized |
Skate (578) | 1957 | 267.1 | 25 | 10.7 | 2,860 | 4 |
Skipjack (585) | 1959 | 252 | 32 | 7.9 | 3,500 | 6 |
Permit (594) | 1961 | 278.5 | 31.7 | 8.8 | 4,465 | 14 |
Sturgeon (637) | 1966 | 292 | 31.7 | 9.2 | 4,780 | 37 |
Los Angeles (688) | 1976 | 360 | 33 | 10.9 | 6,927 | 62 |
Hampton (6881) | 1993 | 360 | 33 | 10.9 | 7,147 | - |
Seawolf (21) | 1996 | 326 | 40 | 8.2 | 9,150 | 3 |
NSSN | 2004 | 377 | 34 | 11.1 | 7,700 | ? |
*Characteristics of SSNs from Skate through Seawolf were taken from various editions of Combat Fleets of the World (Annapolis, Md.: Naval Institute Press). Length, diameter, and submerged displacement of NSSN appeared in Edward J. Walsh, "NSSN 'Enhanced' for Littoral Operations, Connectivity," Sea Power, July 1995, p. 15. An updated displacement of 7,700 tons was revealed at the Naval Submarine League Symposium on 6 June 1996. |
Table 2: Comparison of Littoral Submarine (LS) and New Attack Submarine (NSSN) | ||||||
Design | Shaft Horse-power | Speed (knots) | Length (feet) | Diameter (feet) | Length/ Diameter Ratio | Submerged Displacement (tons) |
LS-1 | 10,000 | 25+ | 245 | 31,75 | 7.7 | 4,049 |
LS-2 | 12,500 | 27+ | 248 | 32.8 | 7.6 | 4,450 |
NSSN | 24,000? | 28+ (est.) | 377 | 34 | 11.1 | 7,700 |
A pragmatic approach to the problem of operations in shallow water would be to design and build prototypes with characteristics such as:
- Length: 245-250 feet
- Hull diameter: 31-33 feet
- Length-to-diameter ratio: 7.6-7.9
- Submerged displacement: 4,000-4,500 tons
- Ballasting: Should be capable of submerged operations in fresh water at the mouths of littoral rivers
- Test depth: 700 feet
- Propulsion plant: Natural circulation reactor, Turbine-electric drive, Power electronics, Contrarotating propellers*
- Ship control: X-stem, In-Out clamshell bow planes on hull
- Ability to bottom: Requires study for littoral
- Quieting: Equal to or better than expected level of fifth-generation Russian SSN
*Advances in contrarotating propeller technology and details of contrarotating electric drive concepts appear in: Jeffrey L. Dutton, “Contrarotating Electric Drive for Attack Submarines,” Naval Engineers Journal, March 1994.
The Office of Naval Intelligence estimates that the fourth-generation Russian SSN, the Severodvinsk, will be slightly quieter than the improved Akula now at sea. NSSN is expected to have the same radiated noise level as the Seawolf.10 The urgency to improve ultra quiet technology was underscored in a statement made by Norman Polmar before the Subcommittee on Sea Power of the Senate Armed Services Committee: “If the past is any guide to the future, it is more likely that the Severodvinsk will be significantly quieter than the improved Akula—and quieter than the Seawolf, which was designed several years before the Severodvinsk.”11
A third Seawolf-class boat has been approved, and NSSN design and construction alternatives apparently involve plans to build three to five units before follow-on boats become competitive (Electric Boat versus Newport News Shipbuilding).12 During hearings before the Procurement Subcommittee of the House National Security Committee, chaired by Representative Duncan Hunter (R-CA), expert witnesses presented a case for “design and construction of advanced prototype submarines, rather than rushing to design and build the NSSN as the lead ship for series production.”13 On 29 March 1996, Chairman Hunter reportedly expressed his concern about an assembly line of NSSNs: “If we make it clear that we’ve ‘fixed’ this design with the first boat, there will be a cultural imperative in the Navy [to not alter it].”14
Table 2 data, comparing possible littoral submarine (LS) designs with the NSSN, have been calculated from submarine design concept equations.15 Some weight and space estimates used for the littoral boats are based on technology not yet proved. Research and development is under way to produce smaller, lighter, and quieter turbine electric drive components and power distribution systems.16 This work should be encouraged and continued at an accelerated pace. The technology panel headed by retired Vice Admiral Albert J. Baciocco, Jr., recently reported that a permanent magnet motor “could be incorporated into a sub’s electric drive system by FY-02 through FY-06.”17 We don’t know yet what speed would be best for the LS design, but two possibilities are displayed. Similarly, we don’t know the shaft horsepower of NSSN, but the speed deemed acceptable by the Reynolds panel was greater than or equal to 28 knots.18
Today, design and construction for a new submarine class takes 12 to 13 years. This is incredible. The Skate, lead ship of the first class of U.S. nuclear attack submarines, was conceived in 1953 and commissioned four years later. With a properly focused submarine design spreadsheet, an experienced submarine marine architect can establish all concept design characteristics of a new boat in about three hours. Using computer-aided design (CAD) techniques for detailed design has been said to have the potential to reduce a design period of nine years to five or six years.19 With the availability of more and more sophisticated CAD techniques, it seems as if the process could be shortened considerably more. We should simply make it happen.
If NSSN production is to start, plans should be made now to terminate the line after four or five units. Design of prototypes, to include boats with general features similar to LS, should begin now.
Reorganization
When Secretary of Defense Robert McNamara reorganized DoD a generation ago, analysts—many without technical experience—made cost-justification studies a way of life. Congressional testimony in 1968 was peppered with references to proclivity of the office of the Secretary of Defense to mandate cost-effectiveness studies that produced an “administrative time lag” in submarine building programs.20 The problem is still with us. In June 1995, the Sea wolf and NSSN programs were described as having been “studied to exhaustion.”21 We must eliminate wasteful administrative procedures and dedicate the intellectual energy saved to design of innovative prototypes.
It is essential that we return to a “structure conducive to progress”22 that ensures a technically proficient design authority, with inputs from modern equivalents of the Submarine Officers Conference and the Ships Characteristics Board. We also should reemphasize the ConForm philosophy. If the Navy is going to have any chance of expeditiously developing submarines to counter evolving threats, we need high-ranking technically trained advocates who can present objective recommendations for a new organization. Time lag must be reduced. Several recommendations for improvements in the submarine design process are on the table as a result of recent congressional hearings. Organizational reconstitution need not be a long process if we start now.
Admiral William Owens and Colin Gray have reminded us that “change is constant” and a “surprise-free future” is unlikely.23 Research and development, the lifeblood of progress, when properly conducted, can lessen the impact of an undersea surprise.24 The longer the New Attack Submarine production line runs, the greater the risk we will miss out on emerging technology that could be easily adapted to prototypes. We are well into a window of opportunity. Let’s prove that we can overcome bureaucratic lethargy by starting a new prototype era now.
1 Norman Polmar, “The Republic Navies,” U.S. Naval Institute Proceedings, October 1995, p. 121.
2 Quoted in J. E. Moore and R. Compton-Hall, Submarine Warfare Today and Tomorrow (London: Michael Joseph, 1986), p. 64.
3 Personal communication, Captain Donald H. Kern, USN (Ret.), 30 August 1995.
4 Adm. T. H. Moorer testimony before the Preparedness Investigating Subcommittee of the Senate Armed Services Committee, 15 March 1968.
5 Patrick Tyler, Running Critical (New York: Harper & Row, 1986), p. 59.
6 R. A. Dodge and M. J. Thompson, Fluid Mechanics (New York: McGraw-Hill, 1937), p. 342.
7 Capt. Harry A. Jackson, USN (Ret.), “Submarine Parametrics,” Proceedings of the Royal Institute of Naval Architects, Symposium on Naval Submarines, 1983.
8 Capt. Harry A. Jackson, USN (Ret.), “The Influence of the USS Albacore on Submarine Design,” Proceedings of the Royal Institute of Naval Architects, Symposium on Naval Submarines, 1993.
9 LCdr. James E. Wright, USN (Ret.),“Submarine Design for the Littorals,” U.S. Naval Institute Proceeding, December 1995, p. 40.
10 Anonymous, Worldwide Submarine Challenges (Washington, D.C.: Office of Naval Intelligence, February 1996), p. 11.
11 Norman Polmar statement before the Subcommittee on Sea Power of the Senate Armed Services Committee, 27 March 1996.
12 Beth Jannery, “Senior Leadership Presents Options to Congress,” Inside the Navy, vol. 9, no. 13 (1 April 1996): p. 13.
13 Norman Polmar, “The U.S. Navy: A New Direction for Submarines,” U.S. Naval Institute Proceedings, March 1996, p. 122.
14 Quoted in Dale Eisman, “Navy Foresees New Sub as Stealthy as Any in World,” Norfolk Virginian-Pilot, 30 March 1996, p. A5.
15 Capt. Harry A. Jackson, USN (Ret.), “Fundamentals of Submarine Concept Design,” Transactions, Society of Naval Architects and Marine Engineers, 1992.
16 Thomas B. Dade, “Advanced Electric Propulsion, Power Generation and Power Distribution,” Naval Engineers Journal, March 1994.
17 Anonymous, “Submarine Panel Says Technology Insertion Strategy Is Not Clear,” Inside the Navy, vol. 9, no. 13(1 April 1996), p. 5.
18 VAdm. J. Guy Reynolds, USN (Ret.), “New Attack Submarine Independent Characteristics Review,” The Submarine Review, January 1995.
19 Steven Ashley, “Designing a Nuclear Attack Submarine,” Mechanical Engineering, April 1995, p. 67.
20 Appendix 1, Hearings before the Joint Committee on Atomic Energy, Ninetieth Congress, 25 July 1968, part 2 (Washington, D.C.: GPO, 1968), p. 161.
21 RAdm. R. E. Frick, USN, “The Submarine Building Program,” The Submarine Review, October 1995, p. 35.
22 N. Polmar, “New Direction,” p. 123.
23 Adm. William Owens, USN, High Seas (Annapolis, MD: Naval Institute Press, 1995), p. 177; and Dr. Colin S. Gray, “The Changing Nature of Warfare,” reprint of an address given at the Current Strategy Forum, U. S. Naval War College, 14 June 1995, p. 15.
24 Rod McLennan, “Avoiding the Undersea Surprise,” U.S. Naval Institute Proceedings, May 1994, p. 125.
Mr. Boyle served on the Sea Owl, X-I, and Skate between 1953 and 1960. From 1961 until his retirement in 1985, he worked as a research general engineer at the Arctic Submarine Laboratory at San Diego.