Inshore Countermine Warfare
INTRODUCTION AND BACKGROUND
The inshore area is measured from the very shallow water (VSW) zone, with a depth from 40 ft to 10 ft, through the surf zone (SZ) and the craft landing zone (CLZ), and onto the beach through the beach exit zone approximately 200 ft across the beach. This is the area that, for example, would have to be traversed by an amphibious landing force against opposition. Also, however, much of the material applicable to inshore mine countermeasures (MCM) applies to clearing port approaches for the U.S. Transportation Command (TRANSCOM), as discussed in Chapter 2.
Amphibious landings against significant opposition are a rare event. Few such landings have been needed since the heavily opposed landings during World War II.1 The Inchon landing in the Korean War was made without major oppo-
sition, and in particular without having to overcome maritime mines. Plans for a landing at Wonsan in the enemy’s rear during that war were delayed by extensive minefields. Eventually, plans for the Wonsan landing were canceled because the South Korean Army captured Wonsan as it moved north. Plans were made for landings in Soviet-threatened areas during the Cold War, and Soviet mining doctrine for protecting beaches is expected to inform future U.S. opponents along the littoral. The Soviet defensive mine doctrine, which was followed only in part by Iraq in defending against a possible coalition landing in 1991, called for a succession of mine barriers starting with a perimeter minefield about 25 nautical miles off the beach, extending through a main mine barrier with several lines of mines about 7 to 9 nautical miles offshore and a VSW barrier, and ending with a heavy deployment of mines and obstacles from the surf zone through the beach exit zone.
The last time a major amphibious landing against opposition was contemplated by the United States in wartime was during the Gulf War in 1991, but although landing forces were kept in place offshore to tie down Iraqi forces it was decided not to make a landing.2,3 The mined approaches to the landing beaches were one, but not the only, factor in the decision. The only operational over-the-beach landing since that time was in Somalia in 1992, but the greeting force was mostly the U.S. media. Future such landings with relatively small forces might easily be thwarted by a combination of sea mines, beach mines, and obstacles even if no shoreside opposing force is present.
The declared U.S. policy continues to be to maintain a capability for opposed over-the-beach assaults, and much of the Marine Corps combat development and modernization planning envisions them. Amphibious landings remain a part of contingency planning for wartime expeditionary force operations along the littoral, and should the need for one occur, time and maneuver space can be critically limited.
Such landings might be needed, for example, on islands of modest size that have no easy landward approach for operations in a country that has only a short coastline, or where ports may not be available and over-the-beach approaches represent the only way to support follow-on logistics early in a campaign.
While amphibious landings of the scale of those seen in World War II are an anachronism when contemplated in terms of currently developing U.S. national and military strategies and operational concepts, a landing of the scale contemplated during the Gulf War could well be called for, into the indefinite future. For example, a Marine expeditionary brigade (MEB)-size landing to protect a major U.S. interest, carried out as a component of the “Operational Maneuver From the
Gordon, Michael R., and General Bernard E.Trainor, USMC (Ret.). 1995. The Generals’ War: The Inside Story of the Conflict in the Gulf, Little, Brown and Company, New York, pp. 192–194.
Amphibious planning during the Gulf War is described in Appendix B.
Sea” and “Ship to Objective Maneuver” concepts,4 could be needed. And “opposition” can come in many forms, from opposing forces massed behind a potential landing beach (which would be bypassed if at all possible under the new maneuver concepts) to waters and landing zones that are mined and that may or may not be overwatched by protective forces. Despite the natural preference to avoid hazardous opposed landings, such operations may be unavoidable.
Even in the reduced cases referred to above, the resources needed for an amphibious landing against opposition can be large. An amphibious landing of the size that can be contemplated today (described below) would be an extremely complex affair, fraught with risks and requiring extensive advanced planning. For the readers of this report who are not familiar with the intricacies of such operations as planned under the new operational concepts, Appendix A describes the process in some detail. If such landings were to be routine, the cost might be prohibitive. Given that they are rare but urgent when the need arises, planners are justified in calling for the development and availability in reserve of extraordinary, joint resources. However, even in that case, the statement of resources required to support a landing must be in keeping with the size landing that the planned amphibious resources will permit. This is not currently the case, as is indicated below.
State of Navy Responsibility and Attention to the Need
Although the Navy has moved smartly to increase capability for offshore countermine warfare in support of amphibious landings and subsequent logistic operations, the same cannot be said for inshore countermine warfare. Currently, the Navy has responsibility for mine clearance up to the high-water mark in support of Marine Corps amphibious landings, with the Marines being responsible for clearing the beach and the exit points. Responsibility for the beach zone is under discussion between the Navy and Marine Corps. However, there is no joint Navy/Marine concept of operations that involves Navy and Marine mineclearing systems in a continuous operation. Attention to this joint operations area admittedly needs to be expanded and should be included in the current draft concept of operations for MCM in support of amphibious landings that is currently under consideration in the fleet.
Until very recently, the inshore region has not been a major focus of the Navy’s mine warfare program planning. Consequently, the inshore capability at present is more “paper” than real. The major modernization programs as embodied in the organic MCM initiative, and the operational command structure as
Headquarters, U.S. Marine Corps. 1996. “Operational Maneuver From the Sea,” U.S. Government Printing Office, Washington, D.C., January 4. Available online at <http://www.220.127.116.11/omfts.htm>.; Van Riper, LtGen Paul K., USMC. 1997. “Ship to Objective Maneuver,” Marine Corps Combat Development Command, Quantico, Va., July 25. Available online at <http://www.18.104.22.168/stom.htm>.
evidenced by the role of the Mine Warfare Command, focus on the countermine warfare challenges in deeper water. While there have been some general requirements for MCM support of over-the-shore logistics, specifics await the further development of the sea-basing aspects of the “Operational Maneuver From the Sea” concept.
State of Current Capability and Efforts vis-à-vis Marine Corps Requirements
Capability for inshore mine and obstacle clearance today is only slightly better, in effectiveness and speed, than it was in preparation for the Normandy landing during World War II. Essentially all of the nation’s inshore/surf zone countermine warfare capability currently resides in the explosive ordnance disposal (EOD) teams, with their divers, mammals, and expectations for unmanned undersea vehicles (UUVs). The sizing and posturing of these units are not coupled with current operational plans for amphibious warfare in major regional contingencies. Mines are likely to be accompanied by obstacles to block movement of landing craft to the beach. Reliable clandestine ways to locate mines and obstacles in the surf zone are limited, although overhead observation as tides vary and water is disturbed by breaking surf can be of some help both for near-surface moored mines in VSW and obstacles in the SZ and CLZ. Thus, swimmers— humans or other mammals—are needed for these purposes, and they cannot remain unobserved if the opposition has night observation equipment. Sea mammal systems remain the only currently fielded way to find buried mines in the VSW zone. Mine and obstacle clearance in support of amphibious operations under these conditions will be time consuming and dangerous.
In contrast to these realities of current capability, the Marine Corps requirements for mine and obstacle clearance call for clearing six transit lanes, each 165 yd wide, from the line of departure to the surf zone. The completion threshold is 72 hours in the near term, shrinking to 24 hours in the mid and long term. This step is to be followed by mine and obstacle clearance from two 50-yd-wide assault lanes departing from each transit lane (to permit, e.g., two rifle companies to land in parallel), a total of 12 assault lanes, in 60 to 90 min. This requirement describes the quantitative implementation of “in-stride” mine clearance, a term variously defined but meaning that mine clearance should not delay a planned operational schedule that is driven by considerations other than mine clearance. For comparison, during the Gulf War, the plans for a landing by a force of two regimental landing teams, had one taken place, reduced the above 12 lanes to 3, since that was the only size landing the available amphibious lift could accommodate.5 That situation has not changed.
Various means have been under consideration to meet the Marine Corps requirements. Transit lanes would be cleared by the organic MCM systems, in combination with the dedicated force if necessary; resource availability to perform the clearance in the required time would be a critical issue. The LMRS and RMS mine-hunting systems can penetrate only part-way into the VSW zone. The helicopter-based systems, ALMDS, RAMICS, AMNS, can do some of the task physically if they are not under shore fire, but the towed sonars for mine detection and the OASIS sweeping gear need some water depth for safe operation. And they cannot detect buried mines, nor can they operate clandestinely if that is required to avoid “telegraphing” where the landing will take place. Finally, as might be expected, the process using these assets would be slow.
To clear the SZ and CLZ, the Navy and Marine Corps have been developing the combined SABRE explosive line charge and the DET explosive net (discussed further below). However, both face technical and operational problems that include their inability to handle obstacles and the space they would occupy on scarce assault landing craft. The Army’s armored plow-type machine for sweeping mines in the SZ and CLZ, and on the beach, has been discontinued. Navy MCM investment in the water regime from a 40-ft depth into the beach is limited to several long-term technology base efforts of ONR, described in Chapter 4 and (in a few cases) below in this chapter. As useful as some of these may prove to be, these technology base programs do not constitute a Navy plan to acquire the needed inshore countermine capability in a timely fashion.
The Physical Environment
Modern sensors and their projected improvements are becoming increasingly sensitive to environmental parameters. Foreknowledge of these parameters is, therefore, becoming more critical to the operational effectiveness of countermine warfare (CMW) systems. Nowhere is this more obvious than in the VSW, SZ, and CLZ, which encompass a high-energy, changeable, and complex environment ill suited to the effective performance of MCM systems and equipment.
The VSW region, submerged following the last Ice Age, still bears past erosional irregularities softened by more recent sedimentation, a condition leading to variability in bathymetry, patchiness in bottom-type distribution, and a wide range of distances between the 40-ft contour and the SZ (taken in this report to have an average slope of 1:300, or a distance of 9000 ft). Due to the shoaling bottom, wave heights tend to build, tidal currents become more pronounced, sound conditions are more complex, and bottom mines tend to bury more rapidly. And due to heavier pleasure, fishing, and commercial traffic, the density of nonmine, minelike bottom objects (NOMBOs) is here at its greatest.
The SZ also presents a wide range of distances between the offshore bar and the high-water mark (a nominal distance of 1750 ft is used here for purposes of calculation, although the distance is much less for many beaches). The offshore
bar, its depth controlled by storm waves and seasonally variable incident wavelengths, causes waves to build and break, creating a deepening of the bottom in the plunge pool landward of the bar. Where waves strike the coast at an angle, swift alongshore currents are formed, and breaks in the offshore bar can cause dangerous riptide currents.
The slope of the beach, and therefore the distance from the high-water mark to the beach exit zone (BEZ) (a beach width of 300 ft is assumed in this report), are controlled by the beach’s composition, which can range from rock to shingles to sand, and by tidal range, which may run from inches to many feet.
While the basic infrastructure is largely in place for receiving, managing, and presenting environmental data on the VSW, SZ, and CLZ, the collection of data during peacetime is difficult and lags far behind requirements. A robust peacetime environmental data collection program is essential if MCM planning and systems performance are to function at their potential
AN INSHORE COUNTERMINE WARFARE SEQUENCE OF SYSTEMS
From the background presented it is possible to describe the countermine warfare systems, broadly defined, that are required to allow such operations to proceed along lines previously outlined. The emphasis is on dealing with the mine and obstacle threat in the VSW, SZ, and CLZ, a region extending from the 40-ft depth contour to that area immediately landward of the BEZ. The objective is to reduce the threat from mines and obstacles to an absolute minimum and to leverage scarce MCM systems whenever possible. Above all, the intent is to define a countermine warfare sequence of systems, and not an uncoordinated set of CMW assets.
The exemplar problem set for this section is the one described in Appendix A—clearance of six 165-yd-wide transit lanes from the 40- to 10-ft contour, and for each, the breaching of two 50-yd assault lanes through the SZ and CLZ, and the clearance of an 80×80 yd offloading zone on the beach, the initial craft landing zone (ICLZ) for each assault lane. Attention is also given to the need to broaden these lanes for the transit of heavy logistics and follow-on echelons immediately after the initial assault, and the larger potential task of satisfying joint logistics over the shore requirements. The problem is in keeping with the Marine Corps requirement to land a MEB against opposition.
Intelligence, Surveillance, and Reconnaissance for Inshore Countermine Warfare
The importance of intelligence, surveillance, and reconnaissance (ISR) for mine warfare is discussed and emphasized in Chapter 2. Clearly, ISR systems encompass all activity that might be related to mining and minefields, onshore and offshore. Nevertheless, several additional observations and details of ISR
systems that are especially pertinent to inshore countermine warfare are given here. Details of the inshore physical environment are given above. The threat environment is outlined in Appendix A.
In a 1994 report,6 and again in its 1997 report on undersea warfare,7 the Naval Studies Board (NSB) recommended strongly that the Navy increase its mine warfare intelligence effort to a level comparable to that enjoyed by such areas as antisubmarine warfare (ASW) and antiair warfare (AAW) during the Cold War. As a result of extensive data gathering, and during its briefings from and discussions with Navy and Marine Corps leadership during this study, the committee saw no evidence that such priority has been assigned to mine warfare intelligence. Funding necessary to evaluate the hardware that has been obtained appears to be as scarce as ever, and the cadre of mine experts needed for such evaluations has dropped below a critical mass. Funding and priority for ISR must be increased, as is indicated in several parts of this report.
As discussed in Chapter 2, inshore MCM could begin with surveillance that indicates minefield building activity. Surveillance of mining activity could enable mines to be interdicted between bunker and minefield if and “when ROE permit. If not, it allows mined areas to be avoided, given alternative routes. If both of these fail it still allows an efficient concentration of limited MCM assets.
In the past most mine-laying activities were conducted beyond the reach of then-available surveillance assets. Today, thanks largely to the Cold War buildup and the more recent developments in response to the requirements of the emerging electronic battlefield, no mine-laying activity is beyond the reach of available U.S. surveillance assets.
Relevant surveillance assets consist of imagery and signal intelligence from satellites and both manned and unmanned atmospheric vehicles,8 submarine elec-
tronic support measures (ESMs) and passive acoustics, Special Forces, unmanned sensor networks, and human intelligence. Since mine surveillance should be utilized at the first indication that intervention might be required, all of these sources will not be available at the outset. The information flow from all-source surveillance will be required in order to monitor and track the movement of mines from bunker to minelayer to minefields.
As an example, the nominal mine defense lay-down used in the threat (Appendix A), if it were applied by a modern-day opponent, would require 2670 mines weighing up to 2000 lb each to be loaded on trucks or rail cars, transported to piers for offloading onto mine-laying platforms that would then be moved to three offshore locations, and then laid at precise intervals in relatively straight rows. While the pier to minefield transit might be masked by other traffic, the precise and repeated pattern of mine laying would be more easily distinguished. Similarly, the establishment of an SZ/CLZ defense extending for 3.5 nautical miles along the beach, and consisting of 13,700 antitank (AT)/antipersonnel (AP) mines and 600 obstacles, is a highly visible engineering task given the resolution of present sensors. Such massive and localized activity would be detected by surveillance sensors whether tasked or not, as was the case in Desert Storm. In the latter case it is not necessary to be able to distinguish individual mines and obstacles. Given the breaching techniques likely to be required, determining the existence of a beach defense with boundaries and existing gaps is all that is needed.
Since the NSB pointed out in its 1994 report that ISR should be the number-one MCM priority, some progress in mine surveillance has been made. The Hamlets Cove/Radiant Clear exercises, ONR’s Littoral Remote Sensing program, and the Third Fleet’s evaluation of the littoral surveillance system (see Appendix A) have all been positive steps that made limited use of national systems. There is little evidence, however, that all-source surveillance has been addressed as a unified program, that tasking priorities have been addressed, or that the required architecture for converting all-source data into an evolving tactical picture for commanders has been considered.
Joint Littoral Awareness Network (JLAN)/Deployable Autonomous Distrib uted System (DADS)/Advanced Deployable System (ADS). Even using the combined sensor sources noted above, the naval forces cannot count on a perfect surveillance picture of mine-laying activity throughout the area of interest. Temporal and spatial gaps due to satellite orbital times, day/night conditions, cloud cover, inclement weather, conflicting tasking, and a staggered arrival time of data from various sensors must be factored in. To assist in filling these potential gaps in surveillance coverage, one additional system should be considered.
In the 1990s, JLAN was a project of the Naval Command, Control, and Ocean Surveillance Center’s RDT&E Division, with input from ONR’s
Deployable Sensor project and DARPA’s Internetted Unattended Ground Sensor program.9 The system consisted of a land/sea network of small, air-deployed sensor packages, the data from which was to be relayed via radio frequency (RF)/ acoustic transmission to a modem for low probability of intercept (LPI) uplink to either a satellite or aircraft to provide a common tactical picture to the commander, joint task force (CJTF) at sea in the joint maritime command information system/global command and control system (JMCIS/GCCS). The land packages consisted of acoustic, seismic, infrared (IR), and chemical sensors for detection of land vehicle traffic, defense preparations, and missile launches. The sea packages consisted of acoustic, seismic, electrical field, and magnetic sensors to detect ship and submarine traffic, and both the splash of mines entering the water (air or ship laid) and the thump on impact of an anchor or a mine with the bottom (air, surface, or submarine laid). JLAN sensors took advantage of an increase by a factor of 10 to 100 in acoustic, magnetic, and seismic sensitivity over the past decade, a power increase by a factor of 1000, and a volume decrease by a factor of 10 to 100. The number of sensors required to cover 2000 km2 was estimated to be 165 for land and 665 for sea, approximately one sensor per square mile.
DADS and the Autonomous Off-Board Surveillance Sensor (AOSS) program, both under development by SPAWAR with ONR support, are evolutionary steps in the integrated underwater surveillance system aimed at providing an ASW/ISR capability in the littoral.10 Deployed from aircraft or surface ships, individual sensors’ components are packaged in an “A”-size sonobuoy-like container. Each package contains a 1.3-m-long battery and processor module, acoustic communication transducer, and float, and a 100-m-long array containing 14 hydrophones, 3 magnetometers, and 1 E-field sensor. With a life cycle of up to 90 days, the arrays are deployed in a barrier sensor field in water depths of 0 to 500 m, with 200 m nominal. Contact and tracking data are transmitted acoustically to a receiver buoy for RF uplink to aircraft or satellite. Although intended primarily for detection of quiet diesel electric submarines, the system is capable of detecting aircraft, surface ship, and submarine mine-laying activity by monitoring traffic sounds and patterns as well as the water entry and bottom impact of mines.
The committee was not briefed on ADS. However, it is understood that the system, designed to be deployed in the littoral and capable of detecting mine-laying activity and quiet diesel electric submarines, has successfully passed its milestone reviews and is set for procurement in FY05. ADS appears to be better
suited than DADS to fill the mine-laying surveillance gap in both the offshore and inshore areas.
To more completely satisfy the OMFTS/STOM mine surveillance requirements, a land extension of JLAN/DADS/ADS technology is required in order to detect the erection of engineering beach barriers, shore defenses, and minefields directly landward of the BEZ. JLAN was a good start in filling this surveillance requirement.
Thus, it appears that existing surveillance assets, while capable of providing excellent surveillance of land and sea mine-laying and beach defense activity, may not provide perfect coverage. Critical gaps may occur in monitoring such activity.
To avoid this, the CNO and the CMC should ensure that the DADS or ADS technology is capable of monitoring surface, air, and submarine mine-laying activity in the inshore and offshore areas and should reevaluate the JLAN technology as a possible land extension of that capability.
Surveillance can detect the existence of mine laying and the rough boundaries of the resulting minefield, but reconnaissance is needed to provide ground truth and to begin filling in the details of inshore minefield boundaries11 and mine and minelike object density, and ultimately to focus detection and classification efforts on likely mine locations. Fortunately, the effort to achieve a minefield reconnaissance capability has been more aggressively pursued over the past 10 years than has the effort to fully utilize surveillance assets. Those efforts have included the Marine Corps coastal battlefield reconnaissance and analysis (COBRA) sensor payload for an unmanned aerial vehicle (UAV) using multispectral imaging for SZ and CLZ reconnaissance, the Army’s airborne standoff minefield detection system (ASTAMIDS) UAV using IR sensors for the detection of land mine fields (important to the Marines), and the submarine-launched long-term mine and reconnaissance system (LMRS) and surface-ship-launched remote mine-hunting system (RMS) for reconnaissance in the littoral. Too, there has been an aggressive and ongoing effort to develop a range of UUVs for limited littoral minefield reconnaissance and follow-on mine hunting, plus environmental surveys (SAHRV, CETUS).
The committee believes that COBRA has sufficient potential for reconnaissance in the SZ and CLZ to warrant completion of the program, and ASTAMIDS, because of its night reconnaissance capability and importance to the Marine Corps, warrants Navy encouragement. For the purposes of this section of the report, however, it is understood that LMRS has a 40-ft cut-off, and RMS is likely to have a similar depth restriction. It is assumed that this restriction is due to the signature of the two vehicles, the effect of a shoaling bottom on maneuver-
ability, and, in the case of RMS, the likelihood of snagging the towed sonar. In any event, both systems may have limited utility in the VSW. Recommendations in Chapter 4 on R&D for improving LMRS and RMS (e.g., SAS for LMRS) may eventually increase the capability of these systems in the VSW. However, for now, it is assumed that both systems may have limited utility in the VSW.
With respect to UUVs in general, the committee judges that unmanned autonomous or remotely controlled underwater vehicles and robotic devices represent a natural evolutionary trend in MCM, including minefield reconnaissance. There is now a grounds well of interest in removing (except for mine recovery for intelligence purposes) both swimmers and marine mammals from the job of minefield reconnaissance, mine marking, and mine neutralization. That step is probably inevitable at some point in the future. However, the same groundswell has been evident, at intervals, since the 1960s. Therefore, although the committee supports the ongoing R&D effort in UUVs, it cautions against any attempt to replace swimmers and marine mammals until UUVs have proved to be a more cost-effective solution, the naval community has learned to place equal confidence in them, they have demonstrated the ability to overcome countermeasures such as fishing nets (including mist nets, which can be strung in lengths of up to 40 miles), and they can successfully replicate the mammals’ unique ability to detect buried mines.
Clandestine Mine Reconnaissance and Countermeasures System (CMR/CS). The VSW (40 to 10 ft) is the area where mines are most likely to bury due to bottom impact, wave scour, and traveling sand ridges, and where the density of NOMBOs is likely to be the greatest. Therefore, an effective minefield reconnaissance system for this area should be capable of detecting, classifying, and identifying moored, bottom, and buried mines. A proposed system capable of accomplishing this difficult task has been on the table for much of the past decade.
The CMR/CS is a small small-waterplane area twin hull (SWATH) platform with displacement in the range of 15 to 20 tons that utilizes suitably adapted Sea Shadow technology to reduce radar cross section and acoustic quieting, and is equipped to transport, launch, operate, and recover two mammal systems. Except for the stealth modification, the SWATH platform can be similar in size and function to the MHS-1-like baseline discussed below in the section “The Mine Clearance Task,” or even the same vehicle for both purposes. A variant of the MHS-1 hull design has the ability to ballast down such that the SWATH superstructure is near water level.12 This variant, combined with Sea Shadow technology, may be preferred for the CMR/CS application owing to a further reduction
in profile and a better mammal-handling capability. The craft can then de-ballast for its own MCM operation in shallow water.
The baseline SWATH (MHS-1) is 40 ft long and 18 ft wide. It draws 4.5 ft and has a top speed of 18 knots and a range of 750 miles at an efficient cruise speed of 7 knots. It is operational in sea state 4. Therefore, the platform is capable of being launched from over the horizon, and operating in to the SZ, defense permitting. Thus it is capable of covering the three main mine belts described in the committee’s threat lay-down.
All future mine threats will not necessarily follow the integrated antiamphibious assault (IA3) doctrine described in Appendix A. However, using the nominal threat lay-down described in Appendix A, and assuming that surveillance and reconnaissance have confirmed the location and boundaries of the perimeter, main, and VSW mine barriers, transit speeds between mine barriers could be at a level governed only by the platform and the need for covertness. This places the mine-hunting phase within the endurance of the mammal system.
The original proposal called for the SWATH platform to be unmanned and remotely controlled by either RF or fiber-optic link.13 It was believed that the mammal systems could be trained to operate without a handler. However, the committee believes that the first-generation CMR/CS should operate with a three-man crew—a boat handler and two mammal handlers.
It should be pointed out that the platform being suggested for CMR/CS can also be adapted for use by the VSW detachment. It would provide a long-range delivery and support platform with enough payload capacity to carry needed personnel, equipment, and neutralization charges.
Thus far, CMR/CS, with marine mammals trained to detect and classify moored, bottom, and buried mines, offers a minefield reconnaissance capability not equaled by any system now fielded. The CMR/CS platform evaluation issue is discussed further in connection with the description of the MHS-1 as an inshore mine-hunting craft below.
Recommendation: The Navy should fund an experimental prototype test series with the MHS-1 vessel to determine its potential as a CMR/CS platform, a delivery and support platform for the VSW detachment, and/or a delivery platform for an influence minesweeping system ahead of assault vehicles. The Navy should evaluate any other potential MCM missions and roles as a future surface MCM vessel prototype, inshore or offshore.
Buried Mine Detection by Electrical Resistivity. The VSW detachment and, later, UUVs need an ability to detect buried mines; this is especially important in
the inshore region, where surf and tidal flows are likely to bury mines. Since the introduction of the bottom influence mine in World War II, the burial of mines due to natural causes has been a sleeper threat to which we have given lip service, provided for only sporadic and incomplete research (e.g., magnetic acoustic detection of mines), and otherwise attempted to ignore. Today, although research on biosensor and SAS technology (see Chapter 4) appears promising, the marine mammal is the only means of detecting buried mines. And that problem becomes more difficult as the mines become smaller approaching the SZ.
Since the VSW is the area in which bottom influence mines are most likely to bury due to natural causes (and we still have not come to grips with the possibility of a self-burying bottom mine), if U.S. mine reconnaissance and clearance efforts in the VSW are expected to be fully successful, we can no longer ignore the problem of buried mines.
During the Desert Shield (the buildup to Desert Storm) phase of the Gulf War the JASONS14 proposed a buried-mine detection technique for use by swimmers based on electrical resistivity15—a technique long used in such applications as mineral exploration, and even for the detection of plastic bags of hashish in the belly of camels.16 The JASON suggestion featured two active electrodes spaced one ahead of the other a distance depending on the desired vertical dimensions of the electrical field generated between the two. The vertical dimension of the electrical field is several times that of the spacing between the active electrodes. The space between the active electrodes is filled with many small nonactive electrodes used to monitor the field with the aid of a small computer. The top surface of the rectangular device can be insulated to prevent interference from surface wave effects, and it is “flown” over the bottom a distance allowing the electrical field to penetrate to the desired depth (say, 12 in.). Given sufficient distance above the bottom, the device can detect the anchor and cable of moored mines, bottom mines, and buried mines. And since the field responds to both conducting and nonconducting anomalies, both metallic and nonmetallic mines can be detected.
Since the JASON recommendation, considerable research on interdigital dielectrometry magnetometry17 has produced systems requiring much less power,
reduced electrode cross section, and the ability to distinguish the small amount of metal in a nonmetallic mine. Dielectrometry and magnetometry sensors measure changes in circuit impedance at electrical terminals as a function of frequency to determine changes in terminal capacitance, inductance, and resistance due to the presence of buried objects such as mines. Such measurements can greatly improve sensor discrimination to significantly reduce the false-alarm rate.
Recommendation: The Navy (ONR) should investigate the utility of electrical resistivity, with particular emphasis on interdigital dielectrometry and magnetometry, for improved mine (including buried mine) detection, classification, and identification with decreased false-alarm rate.
Global Positioning System (GPS). The GPS provides highly accurate position, velocity, and time information to users anywhere in the world. Characterized as the most important MCM development since World War II, GPS adds the ability of all relevant platforms to navigate much narrower cleared channels, and the ability to better reacquire mine contacts. It is critical to the objective of this report—approaching the mine threat with maximum efficiency and asset leverage—that all MCM and assault platforms be equipped with GPS. Further, the GPS system should include a display that shows a cleared channel’s coordinates, or the coordinates of a channel that is to be cleared. All MCM and assault/ logistics platforms should be able to navigate these channels on GPS-connected autopilot. The objective, in addition to that noted above, is to eliminate the burdensome task of lane marking by systems that may be obscured at critical times during an assault.18
The Mine Clearance Task
The section “Amphibious Operations” in Appendix A stipulates that the VSW detachment, aided by CMR/CS, would use the 48 hours of D-2 to D-Day to
reacquire, identify, and place command-detonated neutralization charges on mines in at least the six transit lanes. However, to provide backup for that effort, immediately begin broadening all transit lanes, and clear additional logistics lanes following the initial penetration, a substantial increase in MCM assets is required. The organic airborne MCM assets, owing to reduced vulnerability to coastal defenses following the penetration, can supply a part of this increased requirement. However, the dedicated force will have to provide most of it.
The Navy recognized the need for MCM assets that could deploy with the fleet in the early 1960s. It also recognized, through long experience, that neither minesweeping nor mine hunting required a large platform to operate in the littoral. Experiments were conducted with two MCM support ships, the USS Catskill (MCS-1) and the USS Ozark (MCS-2), carrying 20 minesweeping launches (MSLs) and 3 airborne MCM helicopters. The MSL, a 36-ft open launch (patterned after the Boston whaler), was capable of mine hunting with a strap-on AN/SQQ-16 sonar, mine neutralization by lowering a charge from a Z-boat using the sonar for guidance, and minesweeping using lightweight airborne MCM gear. The helicopters were the forerunners of the present airborne MCM capability.
It was found that the MSL became a very wet boat at sea state 2 and that it was unable to operate in sea state 3. Also, it was found that when both the MSLs and the airborne MCM helicopters were loaded at the main deck level, the support ships became unstable in certain maneuvers and wave directions. However, with the eventual introduction of large well-deck/flight-deck amphibious ships, the perfection of airborne MCM, and demonstration of the stability characteristics of the SWATH hull form, all of the flaws in the original idea can be remedied.
Such a dedicated MCM support ship with both well deck and flight deck capable of deploying with the battle groups and amphibious ready groups, and carrying enough airborne MCM and surface MCM assets, could be able to handle the littoral mine threat.19 An MHS-1-like craft to supplant the MSL would be able to perform the functions originally intended for the MSL, in addition to the swimmer and mammal support tasks described above.
The MHS-1, procured through the Office of Special Technology and built for Mine Search Squadron One (later assigned to the Explosive Ordnance Disposal Mobile Unit (EODMU)-Seven upon termination of the Mine Search Squad-
Box 5.1 MHS-1 Characteristics
Box 5.2 MHS-1 Equipment Package
ron), would serve as an excellent baseline from which to design the surface MCM component.20
Due to twin submerged hulls, the MHS-1 can operate in sea state 4 and survive in sea states 5 and 6. With its excellent seakeeping characteristics the
boat has a vertical acceleration of 0.04 g (RMS) in sea state 4 and a motion sickness index of 1 percent (RMS). The threshold of malaise for motion sickness is at approximately 0.1 to 0.2 g’s, and the intolerable conditions occur at 0.2 to 0.5 g’s.
The MHS-1 is designed to rest on its twin hulls without a cradle. Thus it can be transported aboard virtually any ship with adequate main-deck or well-deck space. It is C-5 qualified (by removing the cabin) and can be transported aboard a flatbed truck. Its cost, fully equipped, is in the $2 million range.21
Due to its low acoustic and magnetic signature, the MHS-1 has been tested successfully against the versatile exercise mine system (VEMS) without actuation. Therefore, with its shallow draft and obstacle-avoidance sonar, it can operate with reasonable safety in moored contact/bottom influence minefields set for deeper-draft ships.
The present Kline 5000 cannot detect objects directly beneath the towed body. Therefore, the 50-yd search path is cut in half by having to overlap along the return path. Efforts to correct this feature are under way.
To date, the MHS-1 has participated in three major exercises: Seahawk 98 (Seattle, Washington), Kernel Blitz 99 (off Camp Pendleton, California), and Foal Eagle 99 (Korea). In Seahawk 98 and Foal Eagle 99 the MHS-1 was transported on the main deck of a landing ship, dock (well deck devoted to other craft), and joined Kernel Blitz 99 under its own power from Coronado. In these exercises the MHS-1 performed above expectations, operated for 48 continuous hours with only crew changes, continued operation when other MCM craft had to return to port due to heavy weather, accurately identified 10 out of 11 contacts, duplicated the performance of MH-15 helicopters equipped with the AN/AQS-14 sonar, and demonstrated the ability to return to a mine contact four times in four tries.22
When a small SWATH mine hunter/neutralizer is designed with the MHS-1 as the baseline, the mine avoidance sonar should be upgraded to mine-hunting status and should be equipped with an expendable mine neutralization vehicle. To this end, plans to make AMNS common to both airborne and surface MCM platforms should be continued. The objective cycle time from launch to mine detonation should be no more than 10 min (the Norwegian MINE SNIPER cycle time is only 6 min).23 The Kline 5000 or 5500 should be retained for bathymetric
and minefield survey work, and the design should be capable of towing lightweight influence sweep gear for proofing cleared lanes. Additionally, a masthead lidar should be included for detection and avoidance of floating mines since the small SWATH will be expected to operate during night hours.
The ideal support ship should have a flight deck and a well deck and be able to transport, at fleet speeds, the number of the small SWATH MCM platforms tailored to clearing the necessary number of lanes in a specified time (perhaps up to 10, if space is available in the well deck), and a similar number of MH-60S (or more capable follow-on) airborne MCM helicopters. Additionally, serious consideration should be given to providing space to carry the VSW detachment and mammal systems, along with UUVs when they become available.
The MHS-1 has demonstrated its ability to do the work, in the littoral environment, of the MCM-1, MHC-51, and MH-53. A support ship designed or modified with the above capacity would transport, deploy, support, and recover the MCM equivalent of roughly the combined MCM capability of the coalition forces of Desert Storm (26 surface MCM hunter/neutralizers and 6 airborne MCM helicopters). The committee understands that the MCM(X) study,24 now under way, is considering a design along these lines, and it strongly endorses that option.
In conclusion, there is a clear need for a dedicated/organic mine control ship (MCS) with well deck and flight deck, capable of deploying with the fleet, and equipped with surface MCM and airborne MCM platforms capable of operating in both the offshore and inshore areas.
As noted in Chapter 2, planning and programming for replacing the USS Inchon (MCS-12) in the near term, and for the next-generation MCS, must consider the addition of a well deck along with a flight deck in order to fully address the mine reconnaissance and mine clearance problem in both the offshore and inshore areas. Existing and developing designs should be evaluated for this purpose.
Recommendation: As a baseline for future design, the Navy should fully evaluate the MHS-1 for inshore reconnaissance, as a VSW detachment delivery platform, as a UUV delivery platform, and for mine hunting and neutralization as well as mines weeping (with lightweight gear).
NEUTRALIZING INSHORE MINES AND BREACHING INSHORE MINE AND OBSTACLE BARRIERS
The U.S. Navy does not now have a mine neutralization charge suited to inshore mine clearance as defined by the requirements discussed in this report.
Swimmers now use a neutralization charge attached to the mine by a bungee cord and detonated by a timed fuse (up to 72-hour delay) attached to a float. Needed is a command-detonated (by coded acoustic pulse) cavity charge to allow more flexibility in detonation time and to reduce the logistic burden.
Delivery of a neutralization charge to a mine has long been a problem. Remote delivery systems have to use a bulk charge and settle for an instrument kill due to the inability to place the charge in contact with the explosive section of the mine. This leaves a minelike object to confuse subsequent minehunting sonars, an explosive charge in the environment, and a doubt as to whether the mine has actually been killed. Since mammals have not been trained and equipped to precisely place a charge against a mine, swimmers are now the only means of precisely placing a neutralization charge in contact with the explosive section of a mine as required by a small charge capable of ensuring a high-order detonation.
Attachment of a neutralization charge to a mine such that it remains in place under current conditions is a problem yet to be solved. The bungee cord works with moored mines and with proud mines but is less applicable with partially and completely buried mines. And it takes time to attach. Magnets do not work with nonmetallic material mines, and glues and bonding by vulcanization do not work because of marine fouling. The committee suggests a command-detonated neutralization charge for bottom and buried mines that can be placed in contact with the mine, but affixed to the bottom, rather than the mine, by a small embedded anchor pin. Since the time between setting the charge and detonating it is, in the case under discussion, measured in hours, the possibility of the mine moving due to storm-induced wave action is minimal. For moored mines, a small buoyancy ring, similar to those worked on by the Coastal Systems Station, Panama City, Florida, clipped around the mooring cable should be sufficient to hold the charge in contact with the mine case.
Recommendation: The Navy (ONR) should undertake a development program aimed at producing a small mine neutralization charge capable of achieving the high-order detonation of a mine, and easily and quickly emplaced by a swimmer, perhaps a marine mammal, and ultimately by an unmanned undersea vehicle (UUV). The charge should be capable of both timed and command detonation.
Pulsed power has been vigorously studied over the years and has been developed to serve many commercial applications. Versions have been developed for use in crushing kidney and bilial stones, in forming metal, and in crushing rock. Over the past decade, DARPA has funded research on the possible use of pulsed power to produce an instrument kill of mines, and to reduce obstacles to rubble.
Research over the past 3 to 5 years focused on the use of an electrothermochemical transducer with multiple firing ports (the proposed Water Hammer) that
could be remotely floated into the VSW and sunk to rest on the bottom. Using a mixture of aluminum powder and water (2 Al + 3 H2O → Al2O3 + 3 H2 + 797 kJ) for energy production, the research aimed to produce overpressure of 2000 psi over 0.5 msec at a range of 20 to 50 yd with a repetition rate of 5 to 15 sec. Earlier pulsed power testing proved that the desired lethality for mines at these ranges could be achieved. However, DARPA support for Water Hammer testing terminated at sublethal pulse levels based on the potential logistics footprint and employability issues associated with the Water Hammer device.
In operation, the Water Hammer proposal called for three transducer devices to be placed on the bottom in the VSW in a diamond formation, the purpose of the two transducers at the base of the formation being to broaden the swept path and to brush aside crushed mines and “rubbleized” obstacles. Advancement of the transducers, in unison, was to be achieved by venting some of the explosive energy both fore and aft of the transducer. The interaction of the shock waves with the bottom would lift the transducer clear of the bottom, at which time the energy vented aft would move the transducer forward.25
Although an instrument kill (sympathetic detonation is unlikely) against mines in deeper water appears feasible, the committee has concern about the application of pulsed power, as configured, in the SZ and CLZ. Besides the problem of maintaining the diamond formation, there is the problem of energy loss through surface venting as the water becomes shallower than the shock wave pattern, particularly as the transducers have to climb up over the offshore bar and down into the plunge pool. And creating and projecting a wave onto the beach through which the energy is focused appears problematic.
The committee understands that a research effort is ongoing to produce a small mine neutralization charge using aluminum powder and water. This effort appears to have merit and should be continued.
Massive Breaching of the SZ and CLZ
It is necessary to understand the magnitude of the breaching task. In considering how to breach the SZ and the CLZ to the desired dimensions of the ICLZ, the widths of the SZ (10 to 0 ft) and the ICLZ (high-water mark to beach exit zone) are critical. The Marine Corps requirement mentioned earlier in this chapter assume an SZ with a slope of 1:300 and a beach width of 100 yd. This section accepts the 100-yd width for the ICLZ. Published beach data26 show that 50
percent of the beaches surveyed have a gradient not exceeding 93, giving a maximum SZ width of 536 ft; 75 percent have a gradient of 208 or less, giving a maximum SZ width of 1200 ft; and 83 percent of the beaches have a gradient not exceeding 300, for a maximum width of 1750 ft. The discussions that follow use the 1750-ft width as the more stressing case.
For calculation purposes, the committee stipulates that instead of focusing on the two 80×80 yd areas (the ICLZ) at the end of each 50-yd assault lane, clearance will focus on the 65×100 yd area between the two assault lanes projecting through the SZ and CLZ from each 165-yd transit lane. The purpose of the two ICLZs is for incoming landing craft, air-cushioned (LCAC) to sit down, unload, and then exit the same assault lane. If, instead, the beach area between the two assault lanes is cleared, LCACs can enter one lane, unload in the space between, and exit via the second lane. The committee also stipulates that if ISR indicates that no minefield or obstacles exist immediately landward of the BEZ, then that area will be used for LCAC unloading, thus avoiding the need to clear either the two ICLZs or the area in between the two assault lanes. The latter possibility, according to present plans, would save a critical hour of breaching time, remove the necessity of housing, transporting, and offloading mechanical clearance equipment at each of six locations, and save the clearance of a total of 960×960 yd (ICLZs) or 390×600 yd (area between assault lanes) for the six transit lanes.
Over the past decade, through numerous studies, workshops, and brainstorming sessions participated in by some of the best minds in the country, several ideas for breaching the SZ and CLZ within the desired time and area constraints have been put forward. Virtually all of these ideas have been rejected on sound technical, operational, or logistics grounds. Those that have been retained for further examination fall into four categories—kinetic energy, explosives, foam, and mechanical equipment.
Of the several kinetic energy approaches, all employ multiple high-velocity darts, impactors, or continuous rod warheads (CRWs) delivered by air-launched missiles or shipboard 5-in. or 155-mm guns. Darts are intended to neutralize AP/AT mines in the SZ and the ICLZ area, and impactors and CRWs are intended to reduce obstacles only in the ICLZ area.
Hydra-7, now in the R&D program, uses an FA-18 aircraft to deliver a wind-corrected tactical munitions dispenser (WC-TMD) housing five SUU 66/B munitions missiles, each carrying 926 high-temperature incendiary darts (2000 fps) or 14 explosively driven impactors for a total of 4630 and 70 penerators per WC-TMD, respectively. The expected kill radius for each munitions missile is approximately 25 ft.
An alternate approach is the mine/obstacle defeat system (MODS), which
uses a JDAM tail kit and Diamond Back folding wing (JDAM-ER) on either of two dispensers. One is the aerodynamic form of an Mk-84 2000-lb bomb to deliver, with circular error probable (CEP) of less than 3 m, 6320 (50 g) penetrators with a kill diameter of 60 ft. The other consists of two 650-lb CRWs with a kill diameter of approximately 78 ft. The former is intended to neutralize mines in the SZ and ICLZ, and the latter to reduce obstacles in the ICLZ area only. JDAM-ER has a standoff range of 30 nm.
A third approach under consideration is the use of two dispenser warheads fired from 5 in. or 155 mm naval guns. Again, chemical and reactive darts are used against mines (SZ and ICLZ), and CRW warheads are used against obstacles in the ICLZ, with a kill diameter of approximately 20 and 30 ft, respectively. The standoff range is 15 nautical miles.27
The committee considered the number of missile dispensers and the number of 5-in.-/155-mm rounds required to clear the SZ and ICLZ area for six transit lanes (12 assault lanes) and found them to be large within the time and assets available.28
SABRE and DET. The breaching approaches nearest to completion are shallow water assault breaching (SABRE) and distributed explosive technology (DET), although the status of both programs is now uncertain. SABRE is a 400-ft discontinuous line charge emplaced from an LCAC using an Mk-22 Mod-4 rocket, and DET is a 180×180 ft primer cord net (nominally 150×150 ft actual coverage) launched into place by two rockets. Neither is effective against heavy obstacles.
Due to wind effects and rocket inaccuracies, as well as its horizontal cleared path, 15 SABRE line charges are required to clear each 400-ft increment of an assault lane in the SZ. The LCAC moves in to the beginning of the SZ, backs off 200 ft for the desired standoff, and launches successive charges by moving sideways for each shot. If the obstacles begin at the offshore bar, then SABRE is restricted to the first 400 ft of the assault lane, leaving the remaining 1300 ft unreachable. DET is similarly affected. The now canceled ATD program for SABRE/DET called for a rocket capable of significantly greater range. If these
two systems are to be continued, consideration should be given to reviving the requirement for a longer-range rocket.
The SABRE/DET systems, although on hold, are near completion. They are the only breaching systems that might be available in the near term. There may be contingencies in which mines but not obstacles will be used in the SZ and CLZ, and where obstacles are also used they may be confined to the tidal range area of the SZ, thus significantly shortening the SZ breaching distance at high tide.
Harvest Hammer. In both its 1994 MCM study29 and its 1997 TFNF study,30 the Naval Studies Board concluded that air-delivered bombs used to create a line charge analogue were the only effective means of clearing both mines and obstacles from the assault lanes through the SZ and ICLZ within the time limit desired by the Marine Corps. In reaching that conclusion, after evaluating several different ideas, the NSB drew on a wealth of cratering and buried line charge analogue experiments conducted during World War II, during the Plowshare program, and during years of experimentation by the Army Corps of Engineers. Independent calculations drawing on this prior experience estimated that bombs carrying explosive charges equivalent to 10,000 lb of TNT, buried on impact to a minimum of 21 ft at 23-yd intervals, would excavate most mines and obstacles from a channel approximately 64 yd wide where the water depth was 3 ft and greater, and from a somewhat narrower dry beach. The result would be a smooth channel some 10 to 15 ft deeper than the original sediment surface. Both NSB studies recommended a scaled test of this concept to characterize the phenomena and to enable the adjustments necessary to a full-scale test and possible operational use.
Subsequent to the 1994 recommendation, the Indian Head Division of the Naval Surface Warfare Division did its own calculations (including several for this study), conducted scaled tests of buried charges (of up to about 250 lb of TNT) and surface-detonated bombs, and sponsored centrifuge experiments at the University of Maryland. Additionally, Lawrence Livermore National Laboratory has done calculations of the effects of a double line of smaller bombs. All of this work, while adding new knowledge and understanding, has confirmed the basic
findings of the NSB. For instance, in scale tests, Indian Head found, in confirmation of earlier Plowshare work, that buried charges simultaneously detonated leave a berm on either side of the long axis of the resulting channel, but not at either end of the channel—a phenomenon yet to be explained but one helpful to the transit of LCAC and advanced amphibious assault vehicles (AAAVs) into and out of the channel. Also, Indian Head found that surface-detonated bombs “sweep” both mines and obstacles some distance away from the blast site.
Unfortunately, the Indian Head effort has been only a part of a larger research task, and progress has, therefore, been slow; the scaled experiments have had to be performed in the United Kingdom and in Australia. Many of the questions posed by the 1994 report have yet to be addressed.
This committee endorses the earlier findings and recommendation of the NSB study group (see Appendix C). After reviewing the many ideas proposed over the past decade for clearing assault lanes through the SZ and CLZ within the desired time limits and ICLZ dimensions, the committee believes that the Harvest Hammer approach holds the greatest promise. However, additional research, scaled tests, and demonstration are required to prove the concept. The Navy should include, inter alia, the following:
Air Force demonstrations. The ability to deliver a string of bombs in a straight line (within GPS tolerances) and at the required interval is critical to the success of the Harvest Hammer approach to breaching the 50-yd assault lanes through the SZ and CLZ. During the course of this study, Air Force representatives expressed interest in demonstrating that a B-2 can meet these requirements. Since the Air Force has aircraft with the required payload capacity, and their use for the delivery job would free up naval aircraft for other missions, the committee recommends that the demonstration be conducted at the earliest opportunity.
Scale tests. The scale, centrifuge, and modeling work at Indian Head should be accelerated, extended to determine what explosive size, spacing, burial depth, and timing are required to form a channel of sufficient width, measured at depths allowing safe passage of vehicles over any mines or obstacles that may not have been removed, or that may have been thrown in from other channels. Recommended to be addressed are (1) the dispersion of mines and obstacles, including partially buried posts, ejected from the explosion channel; (2) the probable condition of tilt rod, pressure, and magnetic AP/AT mines so ejected; (3) the slope of the lip at the terminal end of the channel; (4) the relationship between longitudinal berm formation and wash back following detonation of a line charge analogue; (5) the effects of longitudinal wash back on the slope of the terminal lip; (6) the probability of mines being moved back into the channel by wash back; and (7) the shape of the channel’s cross section following berm formation and wash back.
Bomb size. The calculations for the 1994 report were based on a 10,000-lb penetrating bomb containing around 5000 lb of explosive with yield equivalent
to 10,000 lb of TNT. Using modern explosives at three times TNT would reduce the charge weight for a 10,000-lb TNT equivalent to around 3300 lb, with a corresponding reduction in case weight. If, in the far term, a five times TNT explosive compound with acceptable sensitivity is achieved, then the charge weight could be reduced to around 2000 lb. Future calculations should obviously be based on the use of modern and anticipated explosives. Additionally, modern technology and materials should be brought to bear on reducing case weight while maintaining the penetration requirements. This work should be coordinated with the Air Force effort to develop penetrating bombs following Desert Storm.
Alternate delivery. Harvest Hammer is intended for use only in cases where both mines and obstacles are present, where there is no alternative to breaching, and where breaching time is critical. In such cases, IA3 could include antiaircraft guns and missiles. If the naval fire support has not been able to neutralize these defenses, a standoff delivery of bombs using JDAM delivery should be considered in the R&D effort.
Delivery accuracy. GPS guidance of bombs will be required to ensure impact precision under varying operational and atmospheric conditions. See footnote 18 in this chapter for a discussion of possible GPS jamming and means to overcome it.
Simultaneous detonation. In the 1994 NSB study32 it was estimated that to obtain the best results, bombs in a given channel should detonate within a time window of 0.01 sec, which was considered feasible using timed fuzes. The research program should evaluate timed detonation mechanisms, including trailing wire antennas for command detonation.
Dud rate. For this application, attention should be devoted to reducing the dud rate experienced in stockpile bombs.
Bomb requirements. The original NSB calculations in the 1994 report assumed bombs with 10,000 lb of TNT and spaced at 60-ft intervals. This number will obviously change when the results of the recommended research program become available.
Sandia National Laboratories has conducted extensive experimentation with a binary foaming agent—polymeric methylene diphenylene di-isoyante (PMDI) and a polyol resin.33 The foaming agent, mixed at the nozzle, has a 20:1 expan-
sion ratio and sets in about 5 to 8 min. Additional layers can be added after allowing 8 min for the previous layer to cure. The foam will set up and cure in water as well as on dry land. The result is a tough surface, buoyant in water, capable of supporting the weight of tanks and other armored vehicles without undue wear (55 tank transits result in a rut 1 ft deep). Also, foam stands up well under projectile impact and explosive attack, is fire resistant, and when damaged can be easily and quickly repaired with additional foam.
The advantage of foam is that it can be used to cover both mines and obstacles—at least to the extent of allowing exposure of only the maximum 10 in. tolerable for LCACs and Marine Corps assault vehicles. A free-floating foam causeway in the SZ could, under the pressure of traffic, activate tilt rod mines. However, where the causeway rests on the bottom or beach, tilt rods would be enclosed by and immobilized by the foam. Due to the distribution of weight, pressure mines, particularly those requiring a rolling pressure signature, would not likely be set off. Magnetic mines likely would be set off. However, the foam layer provides both standoff and cushioning of the blast. Experiments have indicated that an AP mine will not vent through a foam layer of only 30 in. in thickness.
A simple calculation from the expansion ratio shows that a 4-ft-thick causeway wide enough to accept a tank, say 20 ft, and extending through the SZ and ICLZ (20×4×2025 divided by 20) would require 8100 cubic ft of chemicals, or 16,200 cubic ft for two assault lanes.
In addition to the possible breaching application, the Marines and the Army might find foam useful inland for bridging AT and AP minefields, swampy areas, and small rivers. In the latter application the “sock” technique could be used to form the pontoon bridges before floating them.
In summary, experiments with binary foaming chemicals (PMDI with polyol resin) have demonstrated the ability to rapidly form roadways and causeways capable of bearing and withstanding heavy traffic, immobilizing or providing blast mitigation of mines, and reducing the exposure of obstacles. Further, such foams have application to bridging inland minefields, swampy areas, and small rivers.
Part of the ONR’s efforts would utilize the data from experiments on foaming agents to evaluate the logistics footprint, delivery and time of installation, and cost of using foaming agents both in the SZ and ICLZ area and inland. If the results are positive for foaming agents, the CNO could then initiate action for the Navy to acquire the capability.
Mechanical Clearance of the ICLZ Area
Present plans call for the Navy to assume responsibility for all breaching operations from the SZ to the BEZ by 2008. However, the committee believes that the Navy should continue its responsibility for clearing the assault lanes for
each transit lane up to the high-water mark to inland on the beach and the Marine Corps should retain the responsibility for clearing the ICLZ areas. This approach is in keeping with the need to clear land mines in maneuver areas that the Marine Corps will face in any case.
When two 50-yd assault lanes have been breached through the SZ and CLZ, and the first wave of AAAVs has passed, the MCM forces have 60 min (90-min threshold) to clear an 80×80 yd ICLZ area at the end of each assault lane for LCAC set-down and unloading. However, discussions with Marine Corps representatives indicated that clearing the 300×195 ft section on the beach between the two 50-yd assault lanes will suffice. Present plans call for landing mechanical equipment to perform this task. With the cancellation of Grizzly, the Marines retain a track-wide mine plow with magnetic rollers mounted on an M-1 tank (12 in each tank battalion) and the line charge system, which is a 300-ft rocket-propelled line charge (1750 lb of C-4).
Utilizing the nominal threat lay-down, and given the stated spacing between mines (18 to 24 ft) on the beach, approximately 22 AP mines and 11 AT mines will have to be cleared from the 300×195 ft area between the assault lanes. Stipulated are two 4×4×4 concrete blocks at the waterline spaced 50 ft apart, two steel tetrahedrons with equal spacing higher on the beach, and behind that a triple roll of concertina wire.
Inland AT minefields are usually sown with AP mines to prevent combat engineers from simply walking into the field and placing neutralization charges on the AT mines. To broaden the acquisition radius of the AP mines, and for concealment, AP mines with deployed trip wires are commonly used. The Army has a technique for clearing a tank lane through such fields in as little as 15 min. A small grapnel hook attached to a line is fired across the field and reeled in by hand—thus setting off all of the AP mines by snagging the trip wires in its path. Combat engineers then walk that line placing neutralization charges on the AT mines over the width of a tank lane. A variant of that technique would seem to have application to the ICLZ task outlined above.
Based on a suggestion made by the JASONs during Desert Shield/Storm for sweeping beach mines aside, a suitable vehicle could be equipped with a self-priming pump, a trainable nozzle, and a trailing intake hose for using seawater as the feed. Assuming that Harvest Hammer has been used to clear the assault lanes, the water cannon would be used to rearrange the slope of the terminal lip (if required) to cut the longitudinal berm on the interior side of the channel,34 and to
sweep AP mines to a central location—possibly against the upper border of the beach. AT mines would be more difficult to move, and, using the Army technique, it is not necessary that they be moved anyway. It should also be pointed out that due to wind, wave, and tidal action, many mines, both AT and AP mines, may be buried. The water cannon can be used to expose buried mines.
Once the 22 AP mines have been swept to a known location, combat engineers can place neutralization charges on the 11 AT mines, and on the two concrete blocks and two tetrahedrons. Since the triple roll of concertina wire will already have been cut by the two assault channels, this vehicle could simply drag the rolls inland for disposal.
An alternative to using explosive charges to reduce obstacles might be the abrasive water saw. Such saws are now in use for a broad spectrum of applications, including EOD work.35 Abrasive water saws applicable to reducing obstacles use a nozzle size of 0.8 mm, a water pressure of 350 bar, and a flow rate of 8 liters per minute. The abrasive is 80-mesh (150 to 300 microns) garnet mixed with water at approximately 12 percent by weight. Although higher pressures are possible, an abrasive water saw with these specifications is capable of cutting 100 mm per min in 10-mm-thick mild steel, or roughly the leg of a tetrahedron in 30 sec. A hand-held version of the abrasive water saw for combat engineers could be used to quickly reduce tetrahedrons and hedgehogs, cut holes in concrete blocks for the insertion of explosive charges, and cut the tilt rod from AT mines.
An alternate approach would be to use cannon fire to destroy the mines as they are exposed by the water cannon, as well as the obstacles (except for the concertina wire). The AAAV is equipped with a 30-mm Bushmaster Mk 44 cannon and a 7.62-mm machine gun with a total of 600 and 2400 rounds, respectively, and its armor can withstand shrapnel from the nearby explosion of antipersonnel and antitank mines.
The combination of a water cannon, the AAAV’s 30-mm cannon, and a hand-held water saw offer the possibility of clearing the ICLZ of mines and obstacles in less than the time now allowed for this activity.
Wattenberg Antisnag Plow. Again as part of Desert Shield/Storm, the JASONs recommended a helicopter-towed mine plow invented by Dr. Willard H. Wattenberg.36 The plow consists of a strong-back, the bottom side of which
contains a series of cutting knives spaced 4 in. apart and capable of penetrating 10 in. into the soil surface. The antisnag label comes from the fact that the knives are capable of articulating in order to pass over immovable objects. Behind, and towed by the strong-back, is a chain “blanket” used to hold the strong-back on the ground under tow and to sift disturbed earth through the blanket while leaving buried mines proud of the ground. Disturbed earth and mines flow over the strong-back in a kind of standing wave. With the addition of a wire basket mounted on the chain blanket, mines can be accumulated for more efficient disposal.
A scale version of the Wattenberg antisnag plow has been tested at 20 knots in very tough terrain (lava boulders) without breaking the digging knives. And it has been demonstrated that an AT mine exploding under the blanket reduces the blanket by only 10 percent, and that repairs are rapidly and cheaply made by simply snapping in new chain segments.
The Wattenberg plow has two major disadvantages: The towing helicopter cannot be used until AA defenses have been neutralized, and it cannot be used efficiently for clearing beaches heavily populated by obstacles. However, for rapidly clearing those beaches where mines but not obstacles are used and where opposing fire has been neutralized, including the SZ, the Wattenberg plow, due to its clearance speed and its ability to clear buried AP/AT mines, would seem to have a unique role to play. Further, after the covering fire has been neutralized, the plow has a role to play in the broadening of inland minefields. As demonstrated by Desert Storm, the most time-consuming MCM job, both at sea and on land, comes after the initial assault.
Under benign operating conditions, the Wattenberg antisnag plow offers unique characteristics of clearance speed, modest initial and repair costs, and applicability in the SZ/CLZ (in the absence of obstacles) and on land.
The Navy (ONR) should evaluate the Wattenberg antisnag plow for application in the SZ and CLZ and on land.
The Navy and Marine Corps need a cleared-lane electronic marking system suitable to safely guide assault and logistics vehicles through narrow lanes and variable headings. An interim marking system consisting of a fresnel lens beacon on the beach now provides navigation guidance for assault and logistics vehicles approaching the beach. It must be placed on a presumably mined beach prior to the assault. It allows only for a straight-in approach and does not accommodate track segments with different headings.
There is no autopilot capability on assault or logistics vehicles which would allow them to conform to an electronically marked transit (165 yd) or assault (50 yd) lane. In situ visual lane markers could be used as an interim technique, but
they essentially “paint” the lanes to be used, making them equally visible to the enemy.
Acoustic pingers could be placed by clandestine clearance forces (divers, mammals, UUVs). The pingers would be energized by an acoustic modem on lead assault vehicles and serve as a backup for electronically marked lanes in a common tactical picture display in assault and logistics vehicles.
The key issue is that a satisfactory lane-marking and assault vehicle navigation system is needed to safely guide assault and logistics vehicles along relatively narrow transit and assault lanes under varying conditions of visibility. A system that does not depend on pre-emplaced navigational aids would appear to be the preferred methodology, such as one that relies on the GPS coordinates in conjunction with autopilot controls on the AAAV and LCAC, should be developed for this purpose.
CONCLUDING COMMENTS AND RECOMMENDATIONS
This discussion of inshore countermine warfare identifies many systems and techniques for clearing mines and obstacles from the VSW, SZ, and CLZ. The committee recognizes that funding for such systems and techniques will continue to be tight in the current defense budget environment and that choices will have to be made as to which ones to emphasize early. The committee believes that to solve the inshore MCM problem satisfactorily in the near term, the following systems and techniques deserve early attention and funding: JLAN/DADS/ADS; UUVs for mine hunting; Harvest Hammer; GPS on landing craft and all MCM craft; lane-marking systems; and continuing experiments with the MHS-1. The remainder of the systems and techniques mentioned merit continuing R&D at some useful level within the affordability constraints, consistent with designating mine warfare as a major naval warfare area.
Recommendation: The U.S. Navy and U.S. Marine Corps countermine warfare capabilities for the inshore region should be improved and harmonized, and responsibilities among the Services should be clarified. In general, efforts are needed to (a) improve the utilization of inshore intelligence, surveillance, and reconnaissance (ISR) information in order to better assemble a common operational picture so that maneuver units can avoid mined and obstructed areas, thereby limiting the need to conduct breaching operations; (b) improve U.S. capabilities for rapid breaching operations (when they are needed); (c) expand the focus of inshore countermine warfare to more fully reflect the need to provide assured, timely access for logistics support; and (d) agree that responsibility for countering land mines above the high-water mark should be retained by the U.S. Marine Corps. Specifically,
The Marine Corps Combat Development Command for the Marine Corps and the Navy Warfare Development Command for the Navy, under CNO and
CMC direction, should jointly define and approve preferred concepts of operation (CONOPS) for opposed amphibious operations, the size and operational character of which should form the basis for future landing force size and equipage requirements (including MCM requirements). The CONOPS should be consistent with the available amphibious lift and fire support resources, approved threat scenarios, and the requirements for logistics flows to and across the shore.
The CNO and the CMC should agree on, and the CNO should ensure that the Navy funds, the programs needed to fulfill the Navy’s responsibility to clear minefields from the VSW zone through the SZ that the Marines may have to traverse to make amphibious landings of up to two Marine expeditionary brigades in size against levels of opposition and on the time lines that have been jointly determined and agreed to be reasonable. These programs should include:
Expansion of the MCM capability supported by the dedicated MCM support ship(s) to include inshore waters;
Harmonization and funding of the automated navigation systems for Navy and Marine Corps landing craft as needed to minimize the width of the lanes that have to be cleared of mines;
A joint research, development, testing, and evaluation (RDT&E) program with the U.S. Air Force to develop and refine the Harvest Hammer approach to clearing channels through the SZ, perhaps as a variant of the JDAM weapon system, including expansion of the existing memorandum of understanding with the Air Force to reflect how the technique will be designed and proved, and how the service will be provided when needed; and
An aggressive program to reevaluate SABRE/DET and other line charge systems concepts.
In addition, the Marine Corps should retain responsibility for clearing the beach above the high-water mark of land mines and obstacles and should aggressively pursue a program to evaluate innovative techniques (such as water cannon) for use in fulfilling this responsibility.
The CNO should work with the Commander in Chief, Transportation Command to more clearly define the likely requirements for joint countermine warfare activities in support of the planned early arrival in the combat theater of maritime prepositioning ships and others that plan to put unit equipment and logistics supplies ashore, either through ports or over the beach—both of which are subject to inshore mining.