There has been little tactical application of the possible wide range of unmanned submersibles, indicating that their development has held a low priority in Navy programs. Remotely piloted air vehicles (RPVs) have received a bit more attention — mainly as targets for weapons testing and for tactical training of operational units. Yet, the concept of the remotely piloted vehicle including submersibles should have received a great boost because of the successes of RPVs in recent MidEast actions involving Israeli aircraft attacks on Syrian surface-to-air missile defenses in the Bekaa Valley of Lebanon. There they showed their value in tactical applications despite their high likelihood of being destroyed during the prosecution of the mission for which they were programmed.
Because unmanned remotely piloted vehicles must be considered expendable, th~y must necessarily be of relatively low cost, of limited technological complexity, capable of self destruction to prevent compromise of their functions, and yet be able to convey information back to their originators before their destruction. This latter capability has not been developed for submersible platforms either in use, or for those which could be readily constructed from existing technology. Wire-guidance of torpedoes is the rare exception. Until solutions for this difficult problem of linking back information from the underwater environment -unlike RPVs in the air — are developed, most of the very attractive uses of unmanned submersibles must be put on hold.
Submerged RPVs should be considered as lowcost force multipliers, i.e. their use can greatly magnify the effects of manned platforms while reducing the risk to the manned systems.
To understand the potential role o~ the unmanned submersible in Navy applications, it might be use~ul to recall bow the Israelis in 1984 used their RPVs in the ultimate destruction of most of the Syrian SAM sites while experiencing no losses to their manned aircraft. Much o~ this experience appears to be translatable to the use of unmanned, untethered submersibles o~ the future.
Israeli RPVs were ~irst ~lown into the Bekaa Valley to covertly record then transmit back -before their destruction — the radar frequencies controlling the Syrian surface-to-air missiles, as well as to identify the location of the controlling radars. The RPVs also recorded the location o~ the SAM control centers and their procedures. This function alerted the Israeli command as to any changes in technology or tactical procedures which could have recently been introduced by the Soviet suppliers o~ the SAM equipment. When missiles were actually fired at the RPVs — and this was encouraged by certain RPVs which were given the characteristics of manned aircraft — the RPVs ~ired-at then broadcast, in real time, their experience. Later, a flock of RPVs were flown in just ahead o~ the manned aircraft going in for an attack on the missile sites, to act as decoys and to greatly reduce the probability o~ the manned Israeli aircra~t being identified and tracked as missile targets.
It is reasonable to consider three distinct classes of unmanned submersibles that might fulfill naval tactical missions. The first are the small guided submersibles, the majority of which are either torpedoes, modified torpedoes (like mobile mines) or vehicles based on torpedo technology. ASW training targets and decoys resembling either torpedoes or submarines fall into this category. Such vehicles have limited tactical flexibility, are low in mission growth potential, are little overall torpedoes are interference or fleet operations dealt with.
The second class of unmanned submersibles, although well developed conceptually, have not seen tactical application. These are larger submersibles which can be deployed by a wide range or platforms. Ocean bottom-search vehicles are the most viable members or this class. The RUMIC mine search vehicle might soon enter development and should be the most sophisticated vehicle or this class. The Autonomous Remotely Controlled Submersible (ARCS), or the Canadians, is a forerunner of the RUMIC. Covert search and reconnaissance, frequently in hazardous areas, is the primary role of the ARCS, which is designed to surface in order to deliver its information. The requirement that such submersibles be launchable from a wide variety or platforms ranging from helicopters to minewarfare craft places a limit on submersible size. (Submarine launched RPVs remain undefined for lack of their total system practicality.) Restricted by their necessary low cost, the medium size submersibles are also limited in their functions, tending to be single function in nature. Since such submersibles also tend to be used in direct support or fleet operations they are generally unarmed and should pose few coordination problems. Also, since such untethered vehicles have simple, short-duration missions within a clearly defined limited operating area, complex external command and control provisions are rarely required. Precise navigation and programmed control are however necessary, particularly where the submersible’s mission is to search a hazardous area. Sophisticated onboard processing or sensor information and capability to alter mission objectives should rarely be necessary. Thus, since there are no high risk technical or operational problems to inhibit their development, early implementation of this class of vehicles is possible.
The third class of unmanned submersibles comprises long range autonomous vehicles. The missions of these submersibles would normally require a large payload capacity and long operational range. A 1982 Mine Delivery Vehicle study, for example, defined a vessel that looked like a small submarine.
High payloads and long operational radius of these large submersibles result in full load displacements of 10 tons — about the lower limit — with some designs reaching into the 100 ton range. The characteristics of these submersibles raise a complex set of operational issues. With few exceptions, these unmanned submarines cannot be deployed from support ships. The Mine Delivery Vehicle, for example, could only be launched from certain large amphibious ships such as the LSD. The most efficient approach is therefore to shorebase such a vehicle — probably at an advanced submarine base. One study shows this type of vehicle to be about 70 feet long, 14 feet in diameter and with a net deliverable payload of up to 50 tons — with a maximum radius of action of several thousands of miles. In addition to its weapon-delivery configuration, its payload bays could be configured to give the submersible a multi-mission capability. Such a vehicle should provide the u.s. Navy with a cost-effective augmentation to the manned vessels of the fleet.
There are at least three important jobs for the Long Range Autonomous Submersible: covert surveillance, tactical probes, and forward-area weapon delivery — mainly mines. For the first mission of covert surveillance, the payload might include a TACTASS towed array if the mission were one of monitoring surface and submerged traffic through a choke point. Other sensors might be included to monitor radars and communication traffic. This capability could be applied as well for a mission for monitoring activity in port areas. Onboard processing of intercept data, pattern analysis and message composition could be handled by a computerized processor on the vehicle. The surveillance mission dictates low on-station speeds or the capability to bottom the vehicle and maintain station for periods up to as high as 90 days. Forward area deployments could extend into areas where defensive mining should be anticipated, or into port areas where ASW defenses — bottom listening devices, ASW patrols, magnetic detectors, etc. — present a high risk environment for SSNs over an extended period of time.
The second mission area for the long range unmanned submersible is the tactical probe. The Israeli RPV probes of the Bekaa Valley Syrian air defenses are illustrative of what might be accomplished by an underwater vehicle sent into a sea area of concentrated ASW activity. The probe might also explore the viability or harbor defenses as to sound listening devices, EW measures in operation, obstructions, anchorage protective measures, installations to protect against air and surface-to surface missile attacks, etc.. Submariners went into enemy harbors in WW II to sink ships — and anchorages and ports will increasingly be the place to find the highest concentrations of enemy ships. But today the same job is likely to become too hazardous for the costly SSN — even if it were probing for the eventual use of long range mobile mines. In any case, the necessary linking back of information — before probable destruction remains the critical element in the probing system.
If the probe is designed to activate enemy defenses so as to discover actual weaknesses, the large submersible must be able to emulate an SSN’s characteristics until put under attack — while gathering and providing for the link back of information gained — then become covert once more to protect the relatively high investment in such an underwater RPV. Designing such a “probe” is certainly a challenge for those who believe in the efficacy and value of underwater RPVs.
The third mission is weapon delivery. It offers the highest payoffs. It is also the one which is likely to be moat worrisome for U.S. naval planners. A weapon-carrying, unmanned vehicle is a potential threat to friendly forces. Even the long range mobile mine might be accidentally planted in shallow areas where ships can blunder upon the misplaced mine. Certainly, errant weapons are the submariner’s nightmare. Thus, the use of weapon-carrying autonomous submersibles will be viable only when they can be operated in modes which preclude their hazarding of friendly ships, including submarines. There is a development plan for the guidance and control system of a weapon-carrying large submersible — a joint effort by the Marine Systems Engineering Laboratory of the University of New Hampshire and the Shenandoah Systems Company.
There are few missions for the autonomous submersible that do not require a route through waters utilized by the ships of the u.s. Navy and its allies. This creates the particular problem of not interfering with manned vessels engaged in fleet operations. This problem may be greater than that of designing and constructing such submersibles. Since most of the important large underwater RPV missions are in or pass through manned submarine operating areas, the coordination of such unmanned vehicles with that of operating submarines must be resolved by present submarine commands. Modern technology and the use of operational constraints similar to those used to coordinate the movement of ships, however, should be able to help resolve this problem.
Significantly, the subsequent manned air attacks in 1984 by U.S. carrier aircraft against Bekaa Valley objectives — without the comprehensive use of airborne RPVs — resulted in an increased effort directed towards increasing U.S. air operated RPVs. The production in numbers of advanced types of unmanned submersibles may however have to wait for world situations which call upon the escalated use of manned submarines. Until then, the development of concepts and prototypes need to be pursued if the cost-effectiveness of such unmanned submersibles is to be realized.