By Norman Friedman*
IN March, the navy cancelled its Remote Minehunting System (RMS), which had been one of several modules planned for the Littoral Combat Ship. RMS was cancelled for low reliability and problems with its mine detection sonar (AQS-20A). What happens now?
The U.S. Navy has two choices. One is to fall back on the earlier tested technology of conventional mine hunting. A specialized minehunter goes into a suspected minefield. It examines suspicious objects one by one, using a high-frequency (short-range) sonar. Mine-like objects are subject to further examination and then to neutralization. To complicate matters, neutralization often does not mean destruction, but rather fatal damage to the mine mechanism (special anti-mine torpedoes do typically destroy the mine in a visible way). To keep a second minehunter from wasting time on a mine already attacked, the minehunter has to construct a precise map of all mines it has examined and attacked (and of all mine-like objects it has classified as non-mines). Whether mines in the sea can be recognized automatically remains a very controversial issue. Most navies rely on humans examining sonar images; typically a suspected mine is revisited by a second sensor, perhaps an underwater television, before the mine is attacked. The cycle of detection, examination, and destruction is lengthy. Progress through a minefield is slow, because each minehunter has to check on any previously unattacked possible mine before moving on. Minehunters are expensive mainly because they have to be protected against the mines they are attacking. That requires enormous attention to limiting their signatures, for example the sound they produce and their electromagnetic fields. To further complicate matters, every so often a new mine mechanism is devised.
The alternative choice is to develop a better remote minehunting system. Remote systems are attractive because they probe a potential minefield without requiring a ship to follow them. Their vehicles are inherently safe (why waste a mine on something small?). They can pass by objects they have already identified as mines. The objects may be attacked by some other mechanism, such as a helicopter carrying anti-mine torpedoes. Because an unmanned device can live inside an intact minefield, multiple vehicles can explore a minefield at the same time. There is no need for an expensive minehunter, because whatever ship controls the mine hunting vehicles stays clear of the minefield. A remote system can therefore be a modular system, interchangeable with other mission systems. All of these points explain why the U.S. Navy was very interested in the RMS. Other navies are beginning to follow this route, too.
Speed in mine countermeasures can matter a great deal. Imagine an amphibious operation, like the one planned for Kuwait (against Iraq) in 1991. The defender has to guess where along a long coast the invaders will come. It is vital to keep him guessing. That is why the U.S. Navy invested in air-cushion landing craft – they could land over much wider areas than conventional beaching craft. The attacker needs some assurance that mines have not been laid where he hopes to land. If it takes him two weeks to be sure the landing areas is clear (because he has relatively few of those expensive minehunters), it is unlikely that he will enjoy much surprise when the troops come ashore. At one time this was not a major issue, because minesweepers were so cheap and numerous that multiple beaches, including those not chosen for a landing, could be swept. With the advent of influence mines, particularly pressure mines and computer-controlled mines (set for particular signatures) came the need to adopt the inherently expensive minehunting technique. Look in Combat Fleets, for example, and see how few minehunters even the most mine-oriented navies now have.
To make matters worse, minehunters are almost all very slow, because they are so small (to minimize signatures) and yet have to accommodate so much equipment.
All of this suggests that there is really no alternative for the U.S. Navy but to develop some way of neutralizing mines using non-minehunting ships like the LCS. The question is what sort of system to adopt. The RMS was an integrated system using a specially-designed semi-submergible vehicle to tow a minehunting sonar near the surface. A ship carried a single vehicle, tethered to it by a radio link. Among other things, the radio link made it possible for a specialist on board the LCS to decide whether a minelike object was or was not a mine. The relatively large vehicle was designed for the purpose.
Ultimately all the RMS or its successor has to do is map a possible minefield with a high degree of precision. Mapping makes it possible for some other device or vehicle, such as a helicopter UAV, to revisit revealed mine positions carrying anti-mine torpedoes or other means of destruction. The data link back to the ship is useful, but it can be argued that if whatever sonar data the vehicle collects can be brought back, that is good enough for analysis. The sonar element of the RMS or some successor can presumably be made intelligent enough to know that it needs a better picture of whatever minelike object it sees.
The navy may already have a system with this capacity. For several years it has been running small Remus unmanned underwater vehicles (UUVs) in the Gulf and elsewhere for minehunting. Generally they have been launched from small boats, their missions programmed using laptop computers. Because they swim deeper than the vehicle towed by the RMS, they can make do with less powerful sonars. The UUVs collect sonar data and bring it back physically to their mother ship, where it is examined by the same sort of specialists who would have monitored the RMS sonar data. The Remus vehicles, which are about the size of a lightweight torpedo or smaller, have no mine neutralization or destruction capacity; they are merely sonar carriers whose paths can be preset. They do have the ability to register where they have been, and that is enough for a revisit by some other agency. Because the vehicles are considerably smaller than an RMS, they too can pass safely near mines. They are even less expensive, and clearly they are expendable in the event someone sets up a mine so sensitive that it will destroy a UUV.
What would a UUV-based mine neutralization system look like? A ship would launch multiple UUVs for the fastest possible exploration of a suspected minefield. Because they would proceed largely or completely submerged, an enemy on shore would probably have no idea they were present. They would be so inexpensive that multiple possible minefields could be explored at about the same time. Moreover, small UUVs could be deployed from a variety of platforms, including the most covert of all, submarines.
There would not have to be any physical link between the UUVs and whatever neutralized the mines. Operators aboard the ships using the UUVs would decide where on the sea bottom or in the water column real mines probably were, rejecting minelike objects which were not mines. They would contribute to a digital map of the minefield, which could be the basis for action by other means. The key to such action is precision navigation, which has become the key to many kinds of operations. It is certainly true that anti-GPS measures, such as the one which is now blamed for the Iranian capture of U.S. sailors, can frustrate such an operation – but any kind of minehunting demands precision navigation, and the presence of identifiable minehunters would surely encourage a potential enemy to set up GPS deception locally.
Given a digital map, some form of attack would be mounted. The obvious future choice would be lightweight anti-mine devices (which currently exist) dropped by unmanned helicopters which could be directed to the appropriate launch points. No observer could be certain that unmanned helicopters were necessarily associated with attacks on a minefield. They might well have other missions. For example, for some years the U.S. Navy has been interested in a form of littoral anti-submarine warfare in which arrays strewn on the bottom detect submarines moving above them, using reliable-path acoustics. This concept was the origin of the project for a very short-range ultra-lightweight torpedo (it is also a torpedo countermeasure).
The UUV/destructor combination sketched here is an example of an emerging approach to naval problems, in which a wide variety of sources of information feed into a tactical picture which is exploited by a variety of weapons. There need be no direct connection between the sensors feeding the picture and the weapons exploiting it. The current example is the new distributed fires approach to fleet air defense. We are accustomed to look at particular sensors, such as the radar of an E-2D, as the core of a system (the RMS fits this category). However, if we retain precision navigation (not a trivial point), we can meld the products of numerous sensors. The core of the system is now the tactical picture into which all the sensor data are melded. As long as the tactical picture is precise (in terms of location), we can send precision munitions to where they are needed. The tactical picture can also help us to avoid traps an enemy has baited.
This new way of visualizing warfare has been incubating for a very long time. It is the difference between the ‘kill chain’ so often discussed and the ‘kill web’ we are now beginning to hear about. A ‘kill chain’ connects a particular chosen target to the weapons attacking it. Once the target has been chosen, the system has a kind of target fixation which precludes attention to alternatives. The chain is, moreover, one-dimensional. Any failure breaks it. RMS fits into this way of thinking. A ‘kill web’ starts with sensors creating a picture of the battle space as a basis for decision. Many different sensors contribute to that map. Losing some of them does not ruin the operation. Moreover, the map gives a decision-maker a good idea of which targets matter more than others. Incidentally, the ‘web’ approach is really what most naval command and control already does, except that we tend not to look carefully enough at it.
* Norman Friedman is author of The Naval Institute Guide to World Naval Weapon Systems. His column is published with kind permission of the US Naval Institute.
