Mr. Richard Boyle’s April 1999 SUBMARINE REVIEW article “Attack Submarine Design: Let’s Wake Up and Win”, on submarine maneuverability, missed the mark so completely on most of the issues involved that I feel compelled to reply. Submarine maneuverability in the littoral and under ice environments is certainly ripe for discussion, but not necessarily for the reasons Mr. Boyle mentions.
Mr. Boyle asks, “Do we really want to skulk around in shallow littorals with a Virginia class SSN, an ungainly $2 billion, 7800 ton 377 foot long submarine?” Along the same lines a few paragraphs later the question is, “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?” He of course implies the answer to the first question is “No” and to the second “Yes”. I think he has the answers very nearly reversed.
The sub we need to take to the littorals is one that will get the job done, and the majority of those littoral jobs are best accomplished by a sub capable of carrying a heavy payload. Delivering swimmers and carrying a few UUVs or UA Vs, all the while equipped with a meaningful mix of torpedoes and missiles, may not be the forte of a “smaller, less sophisticated” submarine. That said, I agree totally with Mr. Boyle that submarine maneuverability in the littoral and under ice environment is of great concern. The definition of maneuverability apparent in Mr. Boyle’s article, however, needs however, to be expanded a bit.
Defining maneuverability purely in terms of tactical diameter doesn’t adequately address some of the issues arising from operating submarines in close proximity to the bottom, ice, possible mines, or other hazards. We need to be able to precisely control our submarines at zero speed to maximize capabilities in any environment that brings us in close proximity to hazards. A definition of maneuverability including precise control of depth, heading, pitch, and their rate of change is a lot more useful when looking at this area of submarine performance.
Reasons to expand our capability to operate at zero speed include:
- Greater stealth for intelligence collection, surveillance and reconnaissance. Speed through the water has always been an attribute that discriminates a target from trash in the water, and increased digital processing power in surface search radars makes motion ever more detectable. We might be able to combine ship control at zero speed with photonics mast technology to make a photonics spar buoy feasible. Imagine conducting I & W missions with own ship at safe depth, and the amount of mast exposed instantly controllable by reeling in or out as desired, similar to an SSBN’s communications buoy.
- Better ability to operate UUVs and UAVs. Recovery of these vehicles in particular is enhanced by the submarine’s ability to be dead in the water.
- Reduction of undesired mine sweeping cross section. A central fact of mine-hunting is that the location of the mines is to a greater or lesser extent unknown. (That’s why you are hunting them.) This means that getting close enough to the estimated minefield position to deploy UUVs or UAVs is not risk-free. One really good way to cut ownship sweeprate to zero and maintain a position to control UUV ops is to proceed to the predetermined position using the utmost care, then stop and maintain a constant geographic position.
- Swimmer delivery. Without a drydeck shelter even a speed of one knot through the water significantly increases the work load for swimmers leaving or returning to the ship.
As for Mr. Boyle’s statement that no amount of technology insertion can improve maneuverability, consider the fact that cruise ships eight hundred feet long routinely maneuver next to the pier with great precision using bow and stem thrusters. While hydrodynamic control surfaces are reliable, rugged, and have served us well throughout our history, it’s time to look at supplemental means of ship control. Advances in variable speed electric motor technology may make pumps mounted in the forward and aft main ballast tanks feasible for precise control of heading, pitch, and depth with zero speed on the ship, plus increase maneuverability over conventional controls alone at slow speed.
The possibility of entirely replacing the bow planes with thrusters should be considered. Bow planes are typically used only at low speeds, with depth control at moderate to high speeds handled by stem planes only. Bow planes do serve to mitigate the effects of stem planes control casualties, so use of split stern planes would be necessary if bow planes were eliminated.
Lastly, our current fleet of 688s are much more maneuverable, and the 6881s more under ice capable, than Mr. Boyle implies in his article. This is due to the improved placement of the trainable secondary propulsion motor compared to earlier fast attack submarines. Mounted just forward of the rudder, a 688’s SPM provides an extremely small turning radius compared to the 637- class midships-mounted unit.
A lot of design effort in the past fifty years has been directed to expanding the top end of our speed envelope, both absolute top speed and maximum tactical speed. As we spend more and more time in the littoral areas, improving out ability at the low end of the speed envelope deserves some attention.
As package delivery littoral missions take on greater and greater significance to the Submarine Force, we can perhaps look to the package delivery professionals for some cues. Federal Express and United Parcel do not deliver using Chevy Corvettes. They use big trucks with short wheelbases. With a little effort we can give our submarines (including any Ohio class subs converted to SSN) the short wheelbase maneuverability needed to really improve our ability to operate safely in littoral waters.