Feature Articles—November 2009 Issue
The Submarine as a Potent Weapon For Littoral Water OperationsSubmarines Offer Many Tactical Advantages In Shallower Waters Due to Their Stealth and Endurance
By Vincent Geiger
Whole Warship Architect
Direction des Constructions Navales
Services, Ingénierie Navires Armés
Lorient, France
Littoral waters are in the spotlight now more than ever. The growing importance of littoral water (i.e., brown water) operations can be explained by many factors, such as an increase in terrorism and asymmetric threats; traffic activities with more efficient means and organization; economic and political factors, including an increase in local conflicts leading to special operations; an increasing need to protect national sovereignty by making critical maritime import/export routes safe; and the interest in protecting offshore oil and gas platforms.
Submarines will undoubtedly play a central role in littoral operations because they are a potent weapon due to their invisibility and endurance. Submarines are often able to intervene without being detected, thus avoiding any provocation, crisis escalation or other political or legal implications. Moreover, opposing them requires a large team of naval assets that few navies can afford, and hunting them takes time. These advantages are especially enhanced when the submarine can hide in its environment.
It is of utmost importance that the designers of modern-day submarines carefully analyze these key factors.
Characteristics of Brown Waters
Brown waters are, in the general sense, waters less than 200 meters deep along sea coasts, straits, channels and gulfs. While this geographical configuration puts huge constraints on operations, it also gives numerous advantages to the submarine.
The shallowness of the water and high maritime traffic in these areas hampers a submarine’s horizontal and vertical maneuverability. The submarine will also have difficulty escaping threats like torpedos, hunting helicopters or anti-submarine warfare frigates.
On the other hand, the seawater reverberation and the irregular relief of the seabed provides the opportunity to hide from active sonar because the variable bottom creates many unwanted false echoes (e.g., from rocks or shipwrecks). Moreover, knowledge of the sea bottom is poor, and maritime traffic and rivers continuously modify the seabed.
When a submarine is in brown waters, it is generally close to the coast, which means that its operation space is small and its enemy’s ground support is nearby. The danger in being detected is thus increased, and the reaction to detection must be very quick. Finally, the submarine’s enemy is likely to react quickly after detecting it, since any such detection of a submarine will be sporadic. Therefore, the time available for detection, classification and reaction is shorter than it is in blue water—and could be a matter of minutes.
The environmental conditions of brown water operations are characterized by highly seasonally variable bathymetry, low-density waters, variable bottom topography and hydrography, and the noise of human and biological activities affecting the efficiency of the active sonar. Additionally, a huge quantity of information must be computed on short notice.
Brown Water Submarine Missions
A submarine operating near the coast can perform a variety of offensive and defensive missions.
In a convoy attack, the submarine waits in a hidden position, covering a small distance at submerged transit speeds (not exceeding six knots and with low signatures) and with moderate diving autonomy. Few weapons are required, since there is a very low probability of firing in this scenario.
Conversely, submarines can protect convoys with a small number of weapons. Eventually, the submarine will also take part in asymmetric interception, thanks to its stealth and weapons capability.
A littoral sub also can conduct harbor blockages, involving especially low speeds of about three to four knots.
Mine laying requires low speeds as well, but also good maneuverability in mine fields, an accurate navigation system and performant mine and obstacle avoidance sonar.
Another example of a brown water submarine mission is intelligence gathering (through optic, infrared, communication, sonar or radar data) in order to prepare a special operation discreetly. A submarine can be used to watch coastal activities, especially asymmetric threats, and to get information on illegal commercial traffic or fishing activities.
Special operations consist of not only the projection of armed forces, but also of preparing for a mission with intelligence gathering. Submarines in brown waters can get in touch through dedicated communication means, provide swimmer delivery vehicles and associated light weapons, and maneuver at low speeds for mission preparation and recovery.
A Sub for Brown Water Use
One submarine that can take on emerging littoral threats is the ANDRASTA submarine, a multipurpose submarine that can operate efficiently and effectively in brown waters. ANDRASTA possesses rugged and reliable platform systems, advanced combat system capabilities and architecture inherited from the Scorpène-class submarine.
ANDRASTA possesses growth potential for additional payloads, such as swimmer delivery vehicle capability and external capacities for mines. Provisions have been made for air defense weapons. Maneuverable in deep and shallow waters, ANDRASTA is fitted with an X-shaped aft steering gear developed for the new French SSN Barracuda class to allow for greater depth control. In addition, forward hydroplanes enable faster crash diving and good diving stability.
ANDRASTA has a high level of automation. In typical diving conditions, five crew members operate under a three-watch system for efficient and safe operations. The submarine is equipped with technologies inherited from the Direction des Constructions Navales Services combat system family. It can perform a range of functionalities, such as providing the raw data from all sensors, tactical situation elaboration and evaluation, tactical aids and target engagement.
It is equipped with a complete panel of acoustic sensors, including cylindrical array, distributed array, flank array, mine and obstacle avoidance sonar, interception array and active array antennae. The sub’s above-water detection includes a radar and attack optronic mast with high-definition television, low-light television, an infrared ranging system and electronic support measures. An extended communications suite consists of a multifunction communications mast, a high-frequency buoyant wire antenna and an INMARSAT (London, England) C antenna. Coherent with its littoral deterrence mission are six ready-to-launch heavyweight torpedoes and anti-ship missiles.
Finally, ANDRASTA is fitted with a dedicated diver trunk, enabling it to simultaneously support three divers at a time. A large area in the sail is designed to be the divers’ external meeting point before and after operations, and the sub is outfitted with dedicated equipment storage.
Vincent Geiger joined Direction des Constructions Navales Services in 1994 as an expert in sonar signal processing (SSBN Le Triomphant program). In 1998, he joined the Agosta 90B project in Cherbourg, France, as design chief. From 2002 to 2008, he was put in charge of Scorpène-class projects as whole warship architect. In 2008, he joined the submarine design department in Lorient, France, as the manager of future conventional submarine designs.
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