ATTACK SUBMARINE DESIGN: LET’S WAKE UP AND WIN

Face it. Many submarine designers, engineers, and operators think we’ve been building the wrong submarine for 30 years. Maneuverability has been neglected.

Last year a friend described maneuverability to a lady at a cocktail party I attended by saying: 11 A short fat submarine is more maneuverable than a long skinny one.” The lady understood; why
can’t we!

When I was in Submarine School in 1953, one of our instructors pointed out that a small length to diameter (L/D) ratio was important to maneuverability. and his words were imprinted on my brain forevermore. A quick review of L/Ds for the body of revolution hulls:

A submarine design should be predicated on its m1ssmn profile. Operational boundary conditions that affect the size and maneuverability of a submarine destined to operate in shallow littorals include:

• Minimum water depth expectation for submerged operations with and without ice cover.
• Requirement to operate submerged in fresh water at the mouths of littoral rivers or in the Marginal Sea Zone (MIX) in summer.

Do we really want to skulk around in shallow littorals with Virginia, an ungainly $2 billion 7800 ton1 submarine 377 feet long?

Captain Ken Cox put the situation in perspective as follows: “With its submerged displacement of (7800 tons] and an expected crew of 113, the [Virginia] is larger than the Polaris class SSBNs, which displaced 6888 tons and had a crew of 112 officers and men. ” He continued: “What may be required is a blend of submersible platforms, not everyone a super submarine [emphasis in original], to cover the span of anticipated missions, while at the same time ensuring sufficient number [emphasis in original] of submarines and qualified, motivated personnel to do the job.”

The Fourth Estate is grumbling. A recent article states that VIRGINIA is “designed to prowl the world’s shallow coastal waters” in one uninformed breath and then wonders if we “may be preparing for a war that will never come. ”

The Defense Science Board (DSB) Report of July 1998 recommends:

“[The] successor to [Virginia] be 1large’ … [and] … future SSNs must have adjuvant [serving to aid] systems recognized as SSN payload instead of being a substitute or extra class of ship … ”

Is it too self-deprecating to ask if we have lost our ability to match rational thought with objectivity? Do we really want to build larger, less agile, more expensive submarines in long production runs? We need some large submarines to carry heavy payloads, but doesn’t it make sense to have at least one other class of smaller, less sophisticated, highly maneuverable, and cheaper submarines for littoral missions?

Part of the attractiveness of a long run of Virginias has been touted as technology insertion. All is well and good as far as hardware flexibility goes, but no amount of technology insertion can improve maneuverability.

Do we really want to rreet1.e hull dimensions or a big production run of long skinny submarines?

Who can doubt that agility in shallow littorals, with or without ice cover, requires a small, highly maneuverable SSN? One possible concept design was proposed nearly three years ago as Littoral Submarine LS-2;

Length
Diameter LID SUBD SHP Submit Speed 248 ft.
32.8 ft.
7.6 4450 tons
12,500
27 +knots

LS-2’s extraordinary SUP-Speed combination would be made possible by an electric drive propulsion plant and contrarotating propellers.

ALBACORE was a revolutionary design that advanced maneuverability dramatically. Using the thumb rule that Tactical Diameter (TD) with standard rudder and “Plus +” stern is roughly four times ship length, let’s compare ALBACORE with LS-2:

With an X-stem, ALBACORE’s TD was only 2.4 times ship length: TDx was 165 yards. {For the sake of simplicity, we have assumed that TDx relationships for the two submarines are linear. TDx for LS-2 is therefore a rough estimate.)

The DSB Report lists a Navy Role as “littoral sea control…, ” but does not mention ice cover. In winter, ice-covered shallow littorals of the Northern Hemisphere are interspersed throughout peripheral seas as low in latitude as 45° N on both sides of the globe, e.g., Gulf of St. Lawrence and Sea of Okhotsk.

When the last Sturgeon class submarine is decommissioned, we will lose all capability under the ice in shallow water.

Using the 4 x L thumb rule for VIRGINIA (with Plus+ stern), we come up with a 1D of 500 yards. This is not good enough for a shallow water transit under the ice.

The immediate goal would seem to be … to develop a highly maneuverable submarine that can transit [emphasis added] under the ice in shallow water. This would ensure U.S. dominance in shallow, open water littorals and restore operational/surveillance capability in MIZ shallows.”‘ [Emphasis added.}

A recent analysis came up with a sobering assessment of future force levels: “[With} the expected low-rate production of the Virginia SSNs, and continued accelerated decommissioning of the Los Angeles-class ships, by 2025 the Navy submarine force will be] … perhaps no more than 33 submarines … ”

The DSB Report recommended 11more, not fewer SSNs.”We are faced with the challenge of maintaining the 50 SSN force level mandated by the 1997 Quadrennial Defense Review. Large submarines are very expensive. The inclusion of smaller, cheaper submarines as part of a high/low mix seems to make a lot of sense fiscally as well as operationally.

As we look: to the future, let’s face up to the need for more than one class of attack submarine, and:

• Initiate design now of a prototype shallow water SSN which is highly maneuverable, functionally simple, and relatively inexpensive.
• Accelerate development of electric propulsion now and integrate the concept with plans for the prototype.