Towed Buoys Bring Network Centricity to Submarines

May 2007
By Capt. James H. Patton Jr., USN (Ret.)

 
Sea trial experiments demonstrate recently developed joint warfare capabilities, many of which could benefit from improved submarine connectivity. The USS Georgia was used in one such trial, called Silent Hammer, off the coast of San Diego several years ago.
Transforming old technology into new concepts offers potential to enhance the evolving role of submarines.

As vastly improved surveillance capabilities and long-range, low-observable, precision-guided weaponry proliferates, the nuclear-powered submarine is emerging as the most likely platform to reach congested regions rapidly, to enter them covertly and to survive there for long periods. In today’s FORCEnet environment, better near-real-time connectivity with submarines has become a goal of both technical and operational entities within the U.S. submarine force.

A submarine has intrinsic qualities of stealth, mobility, firepower and endurance that are unique in the aggregate. It is a crucial platform for intelligence, surveillance and reconnaissance (ISR) operations and for enabling access for other types of force or for fighting independently. But to optimize these capabilities, the modern nuclear submarine needs improved connectivity at operationally meaningful noncavitating speeds while moving significantly below periscope depth.

A single solution to submarine communication at speed and depth probably does not exist, but a family of partial methods, which includes expendables as well as organic assets, is possible. Several of the achievable near-term organic devices offer connectivity at depth but not at meaningful speeds. These products provide only a marginal value-added element. If a platform is constrained to being slow, communication at periscope depth might be preferred to exploit data and information not available elsewhere. Expendables and tethered floating platforms that require slow speeds and frequent retrieval and redeployment lack persistency, which is an important capability, especially when coupled with covertness.

A concept based on towed devices, the Remotely Actuated Sensor Platform (RASP), offers another approach to improving submarine communications.

In the mid-1970s, sailors on the USS Richard B. Russell demonstrated towing a communications buoy with an articulated whip antenna, the AN/BSQ-5, at speeds of up to 15 knots. The submarine towed the buoy at operationally significant noncavitating depths while the buoy enabled persistent two-way radio frequency connectivity at high, very high and ultrahigh frequencies. At the time, this demonstration was an interesting and effective answer to an essentially nonexistent question. No major requirement existed for persistent two-way connectivity from deep and fast submarines.

If the AN/BSQ-5 were being developed today, it would need to include more than a platform from which a whip antenna could be raised above the air-water interface. A buoy for today’s mission would have to be capable of maintaining an ordered depth autonomously. For instance, it could sustain a depth of several tens of feet for continuous passive reception of the ubiquitous very low frequency broadcast or a wave-following shallower depth from which an antenna-bearing mast could be erected. The buoy would not be continuously reeled in and out, using noisy handling gear.

With the weight, volume and capability improvements of electronics and supported sensors, a towed body the size of the AN/BSQ-5 could contain a passive sonar array to provide above-layer acoustic awareness and preprocessing of other signal trains coming to or from an erected antenna. Through advances in solid-state electronics, the antenna could be a directionally stabilized phased array that could boresight to the Milstar extremely high frequency satellite or its likely follow-on, the Mobile User Objective System satellite, while transmitting with an exceptionally low probability of interception. The mast and antenna assembly could be studded with photonic and radio frequency sensors, including infrared, blue-green laser, global positioning system and automatic identification system (AIS) receivers.

The AIS system is required to be on all merchant vessels with greater than 300 tons displacement. It constantly transmits information such as where the ship is from, where it is going and what it is carrying as well as data on the vessel’s operational parameters, including course, speed and location. This is valuable information for submarine personnel, especially in high-contact-density areas. A small sensor that captures airborne acoustics also could be used to enhance a submarine’s security.

 
 
The AN/BSQ-5 (l), as demonstrated in the 1970s, was towed at operationally significant noncavitating depths and enabled persistent two-way radio frequency connectivity at high, very high and ultrahigh frequencies.
With today’s enhanced electronics and sensors, a towed body the size of the AN/BSQ-5 could offer better communications capabilities. The Remotely Actuated Sensor Platform concept (r) is one example of how a towed platform might enable improved connectivity for submarines.
The type of buoy conforms with the RASP concept. The direct incorporation of RASP would be problematic on some ships, most significantly on the Los Angeles class of nuclear-powered attack submarines, which will constitute the bulk of the submarine force for years to come. Therefore, in addition to pursuing proper variants for the Virginia class and other ships yet to be built, workable variants of RASP that have as many of its features as is feasible should be developed to backfit the existing hulls.

The RASP concept currently is being explored by Lockheed Martin Sippican Incorporated, Marion, Massachusetts.

During Silent Hammer, an exercise held a few years ago, the USS Georgia played the role of a nuclear-powered cruise missile submarine operating as a command ship. This effort provided a glimpse of new capabilities for the U.S. military portfolio that could be possible with improved submarine connectivity. In this exercise, a U.S. Air Force Special Forces brigadier general was given about a day’s notice to assemble a staff and report aboard the Georgia, from which, after transiting to the simulated area of interest, he orchestrated a large number of other assets in a complex ISR and battle problem, largely through two high-data-rate masts. These assets, however, required the craft to spend most of its time at periscope depth and therefore kept it restricted in speed. Had a concept such as RASP been available, the commander and his staff would not have had to go offline during periods of repositioning, significantly enhancing this successful operational experiment.

Several factors are emerging that will further increase the importance of the submarine force within the U.S. Defense Department. One is the rapid ramping up of the Chinese navy in both quantity and quality, with an impressive potential not only to impose a credible level of anti-access/area denial to foreign warships within the first island chain (see page 67) but also, uncomfortably soon, to present a deepwater challenge to the U.S. dominance of the Pacific Ocean.

Another is the new chief of naval operations’ proposed maritime strategy, which reportedly highlights the demonstrated capability of deployed, major U.S. warships to provide meaningful aid anywhere in the world in a quick manner, such as during the Indonesian tsunami and Hurricane Katrina. During these events, the deterrent responsibilities of the deployed first responders would have to be assumed rapidly by other equally or more survivable forces such as submarines.

A third factor is what seems to be an inexorable opening up of Arctic sea lines of communications by global warming. The changing environment will add to the freedom-of-the-seas responsibility for the dominant sea power, and it is a situation that submarines based in the northeastern United States are capable of handling.

Improved connectivity, particularly with persistence at increased speeds and meaningful noncavitating depths, would enhance the ability of the submarine force to respond to these factors. A properly designed towed communications buoy such as RASP addresses this connectivity issue better than the other partial solutions.

Capt. James H. Patton Jr., USN (Ret.), is president, Submarine Tactics and Technology Incorporated, North Stonington, Connecticut.