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6 Engagement In this chapter the committee examines technology for reducing the logistics burdens associated with combat engagements, including projectile weapon systems (gun tubes and missiles) with an emphasis on precision guided munitions, energetic s (propellants, explosives, and warheads), and directed energy systems. Technologies and systems are assessed in terms of their potential for reducing logistics burdens for an AAN battle force. The principal logistics burdens directly linked with engagement are the weight and volume of ammunition, the weight and volume of the lethal systems transported to, from, and within the area of operations (operational and tactical mobility), and the energy requirements for lethal systems that must be supplied from battlefield fuel. in general, technology could reduce logistics burdens by ensuring that every round of ammunition fired hits its target and is effective ("one round, one hit, one kill") or by decreasing the weight requirement per round. Significant reductions in both of these categories could be achieved through near-perfect situational awareness (SA), precision guidance systems, and highly lethal munitions (or other kill mechanisms). Of these, SA is critical not just to reducing the logistics burdens but also to engaging the enemy successfully. SITUATIONAL AWARENESS The DoD defines SA (situational awareness) as "knowledge of one's location, the location of friendly and hostile forces, and external factors such as terrain and weather that may affect one's capability to perform a mission" (GAO, 19981. The importance of SA to success on the battlefields of the next century cannot be overstated. Accurate information about the locations of forces, capabilities, and intentions of both friends and enemies, as well as details about the terrain and weather, have been uppermost in the minds of commanders throughout history. Even before the time of semaphores, scouts and couriers were essential to battlefield sensing and communications. Army XXT forces will have networked computers capable of passing digitized information, including detailed images and processed intelligence, to all levels of the command hierarchy. In the AAN time frame, continuing advances in information technologies should ensure even better SA. Appendix F discusses the range of opportunities for and the potential pitfalls of the information processing and telecommunications technologies with the greatest potential impact on AAN logistics. SA begins with knowledge of friendly and enemy locations, but SA technologies involve more than the global positioning system (GPS). Accurate SA will provide the 87
88 REDUCING THE LOGISTICS BURDEN FOR THE ARMYAFTER NEXT operational information required to project a battle force of appropriate size, with the right suite of weapons and equipment, at the optimum time and place. Determining the numbers of soldiers, units, vehicles, and systems for a "right-size" force is essential for Togisticians to provide "just enough" materiel (i.e., with allowances for risks) and to avoid burdening the force with excessive quantities of ammunition "just in case." SA has always been an important factor to support weapons systems for both standoff platfor~ns and close engagement. In Army XXI, and even more so in AAN, the reliance on maneuver and precision fire to achieve technological overmatch will make near-perfect SA a prerequisite for successful engagement. Figure 6-1 is a schematic representation of the system components needed for near-perfect SA. Computation functions at the sensors, at the command and control nodes, and at the response platforms will require detection, identification, and multisource fusion algorithms even more robust than they are today for mission-critical functions. Otherwise, an opponent skilled in camouflage and deception could defeat the SA system and escape detection. The Army's critical dependence on SA technologies increases the likelihood that information warfare techniques, including electronics countermeasures, will be used. The communications links must be exceptionally robust. Large amounts of data will have to be transmitted securely, with guaranteed reception, over a complex and rapidly changing network, in the face of sophisticated attempts at disruption and spoofing. At present, precision guided, or "smart," munitions are relatively expensive and are reserved primarily for high-value targets. Highly reliable, miniaturized, integrated systems for sensing and guidance control that can be produced inexpensively and in large quantities will be essential for an AAN battle force that relies on precision munitions for all of its indirect-fire close support. Networks of miniature, inexpensive sensors will provide the wide-area coverage and advanced warning inherent in the concept of near-perfect SA. Examples include sensor networks for detecting and identifying chemical and biological warfare agents and acoustic sensors for detecting vehicle movement, human movement, and voices. For the terrain guidance discussed in Chapter 5, the SA system will require a combination of (1) previously stored (in each vehicle) "unchanging" data, such as a terrain database, (2) "look ahead" sensor and processor systems on vehicles that can update information on transient and alterable features (e.g., visibility, soil conditions, road and bridge damage, and mine detection), and (3) remote sensing images and wide- area alerts (e.g., moving target indication) from satellites or UAVs. Real-time integration of data from all of these sources into a "here-and-now" presentation will have to be available on every vehicle to realize the AAN vision of open-formation, high-speed, collaboratively self-routing charges of combat vehicles through the killing zone. For shooters on these vehicles to achieve one round, one hit, one kill accuracy against targets that are beyond their line of sight, the in-vehicle presentation system must be linked with targeting and fire control systems. The SA system for logistics command and control will also depend on sensors, data processing, information integration, and decision-support aids. Technologies applicable to SA in the AAN battle space will have the capability to reduce logistics inefficiencies by minimizing the number of "just-in-case" support requirements. But the full range of opportunities will be realized only if the Army continues to exploit rapid advances in the underlying technologies, rather than assuming that SA has been optimized by a revolution in military logistics when Joint Vision 2010 has been realized (DoD, 1996~.
ENGA GEMENT Remote Sensor Suite D al n Command Center Data Fusion Target Prioritization Communications USES Link ~ (' _ Local Processing and Data Compression FIGURE 6-1 Schematic representation of the situational awareness system. 89 Remote Sensor Suite Parallel Interconnect Complex Sensor Array Weapon System Target Acquisition Guidance Smart Munition 1 ~)~9 During the study, committee members became concerned that AAN planners and proponents were sometimes complacent about keeping abreast of rapid changes in SA technologies. Even if Army ~ (the Army of the 2010 time frame) has "mental agility" compared with opponents of that era, this technological superiority could erode rapidly as the technologies continue to advance. Even if the Army has an unprecedented level of SA by 2010, it must be prepared to maintain its advantage to 2025 (and beyond). Appendix F highlights some of the technical reasons the committee believes that maintaining superiority in SA will be a demanding task. First, simply maintaining and upgrading the interconnecting hardware and software systems will be a daunting challenge for the Army, as it is for commercial organizations that have only a fraction of the Army's workforce and installed technology base. Second, much of the enabling information processing technology (i.e., "computers") will continue to be driven by commercial markets, rather than by military specifications or DoD requirements. However. the Armv cannot assume that commercial markets will solve all of its difficult , ~ ~ ~ ~ - ~ ~ . ~ ~ . ~ ~ ~ ~ ~ ~ . . problems te.g., t1eld1ng components that are reliable and rugged under conditions anywhere in the world). Third, the rate of advance of any specific SA technology over several decades will be unpredictable. Therefore, the Army can neither rely on a continuation of trends, even if they are well established, nor assume that a physical limit will inevitably halt
9o RED UCING THE LOGISTICS B URDEN FOR THE ARMY AFTER NEXT advances in SA capabilities for which that technology seems to be essential. An example (described in Appendix F) is the current debate in the semiconductor and microprocessor technical community about the applicability of Moore's Lawt to 2010 and beyond. The bottom line is that the Army cannot assume that trends in advancing the fundamental technologies for SA will remain constant until the AAN era. If and when technology trajectories change, the Army must be prepared to adjust its planning assumptions for maintaining SA dominance and must then follow through with the efficient execution of a timely strategy. If a trajectory shift occurs, an opponent with less advanced technologies may no longer have to modernize a large installed base. This change could give an otherwise overmatched opponent a technological agility that could unde~ine the near-perfect SA on which an AAN battle force will depend. Rapid innovations in all SA-relevant technologies-including those for basic computing and information processing capabilities will continue well beyond the time frame for incorporating today's technology into Army XXI. Opponents with later, and therefore better, technology must not outpace AAN forces. SA capabilities must be continually upgraded beyond Army XX], within resource constraints, without compromising system integrity. The committee believes continuing modernization will be a daunting challenge, especially because new SA systems will be required to meet as yet unidentified AAN engagement system requirements. PROJECTILE WEAPON SYSTEMS Technologies for projectile weapon systems can reduce logistics burdens by helping to achieve "one round, one hit, one kill" and by decreasing the total weight transported per round fired. Total weight transported includes the weight of the lethal system and supporting elements (including troops), as well as the weight of the round. This section examines prospective technologies for gun systems, small missile systems for precision attack, precision guided munitions, and energetics, primarily in teas of their potential for reducing logistics burdens of ammunition and fuel. In several instances, the committee uses current system concepts to illustrate the significant factors that can increase or decrease logistics demands and that will be needed in AAN battle force engagement systems. Gun Systems Alternative gun propulsion technologies with significant implications for logistics burdens include the electrothermal chemical (ETC) gun, the electromagnetic (EM) gun, and liquid propellants for conventional gun systems. All three have advantages and disadvantages in terms of reducing logistics burdens. Moore's Law is an empirical generalization first stated in 1965 by Gordon Moore, then the chairman of Intel Corporation. Moore observed that a graph of the growth of memory chip capacity (measured in numbers of transistors per chip or millions of instructions executed ner second) approximated an exponential growth curve with a doubling time of one year. --a ~rr
ENGA CEMENT Electrothermal Chemical Gun 91 One way to increase the range of solid propellant, cartridge-based rounds is to add energy to the propellant combustion via an electrically generated plasma. This is the basis for the ETC gun currently under development by the Army. By implementing the ETC concept, muzzle velocity can be increased using the same amount of gun propellant as in current rounds. This should enable the design of smaller guns and ammunition in the future. The drawback to the ETC gun is the high power required to generate the plasma. The potential logistics implications of the ETC gun are that the same perform- ance as current rounds could be achieved with smaller, lighter rounds, or rounds of the same weight would need less solid-propelIant energy and would thus be less sensitive to hazards. Alternatively, rounds of current weight could have more than a 10 percent in- crease in muzzle velocity, a greater range, and a higher probability of kill by incorporat- ing projectile guidance sensors and controls. Among the disadvantages to be considered are the added weight of the external power source and the fuel needed to re-energize it. Army demonstrations of the ETC gun concept have proved that it can augment the chemical energy from gun propellants. The Army objective for this concept is 18 MJ muzzle energy (i.e., combined chemical and plasma energy) and I.9 km/s muzzle velocity. The basic design of the plasma generator has been completed and could be added to new shells with minimal changes in production processes. A principal barrier to implementation is that energy storage devices, which must be compact but have the high power density required to develop the 0.5 to 5 M} plasma energy, have not been developed. Other major hurdles are the sensitivity of the plasma generator to rough handling and the lack of solid-state switches that can handle high power densities. Electromagnetic Gun (Rai! Gun) A propulsion technology with the potential for greatly increasing the muzzle velocity of projectiles is the EM (electromagnetic) gun, also known as the rail gun. The projectile is accelerated by the strong magnetic field generated when a large electrical current passes through the projectile as it crosses between two conducting rails running the length of the gun tube. Because EM gun technology has the muzzle velocities needed to fire kinetic energy projectiles capable of penetrating the best passive armor (velocities of 2.4 km/s and higher), it is often promoted as the antiarmor armament for a combat vehicle capable of direct-fire "duels" in tank-on-tank engagements. The high muzzle velocity attainable even for large rounds also makes it suitable as a long-range, indirect- fire weapon, particularly if the round carries a guidance system for homing in on the target. A 1987 study by the Army Science Board found that that EM technology might save on weight and volume because fuel to make electricity would replace the propellant charge (not the warhead). Fuel consumption would increase somewhat, but the decrease in ammunition logistics would be significant (ASB, 1987~. The STAR 21 Lethal Systems report included the following information about high velocity, kinetic energy penetrator (KEP) technology:
92 REDUCING THE LOGISTICS BURDEN FOR THE ARMY AFTER NEXT Two factors are fundamental to defeating armored vehicles: (1) penetration and (2) target damage. Penetration of advanced armors, such as ceramics, can be enhanced by increasing the penetrator velocity to above 1.7 km/s. This velocity is close to the upper limit of high performance conventional guns. There are also practical limits to the mass that can be propelled by conventional guns. But the EM launch technology offers the prospect of a substantial increase in both factors. Although armor design can continue to be improved, the possibilities are limited inherently on the defensive side by the weight of armor that can be tolerated in a vehicle. Further, it is very difficult to divert or intercept a KE projectile. (NRC, 1993c, p. 2) The STAR 21 main report included the following statement on the potential of the EM gun for Tong-range heavy artillery: One potential [long-range heavy artillery] systems concept would combine hypervelocity propulsion, to achieve range, with on board terminal guidance for accuracy. Although hypervelocity projectiles are often discussed for direct-f~re antiarmor applications..., the first fielded systems to use high-velocity electric propulsion (whether electrothermal or electromagnetic) could well be long-range artillery.... If the range of existing artillery could be effectively doubled, with accuracy maintained or even increased through terminal guidance, the firepower resulting from this technology would be of immense military significance. (NRC, 1992,p.85) The Army-sponsored Institute for Advanced Technology (IAT) and the Center for Electromechanics at the University of Texas at Austin have been working on EM gun technology since 1979 in coordination with the ARL, the Army Armaments Research, Development, and Engineering Center, DARPA, and the U.S. Marine Corps (University of Texas, 1998~. Muzzle kinetic energies of 9 M] and muzzle velocities up to 6 km/s have been routinely achieved in the laboratory. lAT has now installed the first fully self- contained rail gun at Yuma Proving Ground, Arizona, for field tests. The Materials Research Laboratory, Ascot Vale, Australia, is also working on an EM gun. EM gun technology is not subject to the same limitations on increasing the ki- netic energy of a projectile that apply to conventional chemical propellants. Constraints on projectile velocity begin to appear only at much higher muzzle velocities. Cowan (1992) reports a 6 km/s velocity limit for high-performance EM guns because of a limit on increasing momentum as the current increases. Aerothermal heating of an EM pro _ _ , . , ., . ,, , ,, . , ., , , , , . ,, . , in, . .. . . . . ... Jechle requires that the projectile have heat shielding above ~ kilos. At higher velocities, an increasing amount of the muzzle velocity is quickly lost to aerodynamic resistance (NRC, 1993c). The strength of the projectile materials may also become a limiting fac- tor. However, KEPs with velocities of around 4 km/s can defeat all known armors. One logistical advantage of the EM gun is the smaller weight and volume of the round compared to a chemically propelled round with the same projectile mass (see Figure 6-2~. A second advantage is that the round is less sensitive to inadvertent reactions because it contains no energetic materials for propulsion. Third, because of their higher projectile velocity, rounds fired from EM guns have a significantly higher probability of kill, given a hit, than chemically propelled rounds. A tactical limitation of EM guns as vehicle armaments is that they are line-of- sight weapons until the aim point can be corrected while the projectile is in flight. This
ENGA CEMENT FIGURE6-2 Railgun projectile. 93 limitation means that a vehicle-mounted EM gun for antiarmor assault is basically a frontal or side-attack weapon although the most vulnerable part of most armored vehicles is the top. The major logistical disadvantage of EM gun systems is that they require a sub- stantial source of battlefield electric power. They also require fast, solid-state switches that can rapidly switch very high current Toads, which must still be developed. The committee was briefed on a concept for a vehicle-mounted 105-mm EM gun. The gun system, comprising the gun and autoloader, 42 rounds of ammunition, and the power management system for the gun, was projected to weigh 10.3 tons. The power manage- ment system included a 202-MJ pulsed power source (a compensated pulsed alternator, called a "compuisator"), a lOO-M] lithium-ion battery for intermediate storage, thermal management and high-power subsystems, and 50 gallons of fuel for the compuisator (Johnson, 1997; Halle, 1997~. An Army integrated idea team also envisioned a 120mm EM grenade launcher (Freeman, 1997~. The spoiler in these concepts is that weight, packaging, and high power requirements severely limit the feasibility of EM armaments. From the standpoint of logistics burdens, the EM gun system is too heavy to serve as an antiarmor armament for an AAN armored combat vehicle. A concept briefed to a member of the committee was a 40-ton vehicle with a 120-mm gun capable of muzzle velocities greater than 2.1 km/s. A more likely application of EM gun technology to the AAN battlefield would be as a long-range artillery weapon, which could support battle force operations from as far away as 500 km, perhaps from the staging area. Fuel supply logistics would be substantially simplified, and the principal technological obstacle would be a terminal guidance system to ensure long-range accuracy. A "corps artillery" system concept briefed to the committee would use essentially the same 120-mm EM gun as the combat vehicle concept, but with the compulsator on a separate vehicle platform. While this concept could be used for long- range support, 20 tons per vehicle is probably still too heavy to meet AAN battle force operational mobility constraints. Liquid Propellant Gun All of the services, including the Army, have explored the use of a liquid gun propellant. One advantage would be the potential for much lower sensitivity to accidental ignition, which could reduce the weight and volume of protective packaging used with current rounds. Another potential logistical advantage over cartridge-loaded
94 REDUCING THE LOGISTICS BURDEN FOR THE ARMYAFTER NEXT solid propellants is that, in principle, one liquid propellant, transported and stored in bulk, could be used for all calibers of guns except small arms. However, there are unresolved storage and chemical issues related to ignition. For example, using liquid propellants in large quantities on the battlefield would require new methods of storing, pumping, and replenishing the propellant at each gun tube, much like distributing fuel to vehicles. A separate succlv vehicle would only add to the logistics support requirement rr ~ -a---- ----I Although the chemistry of liquid propellants has been studied for more than 40 years, the technology is not yet mature. There are major problems, which are still not well understood, with both chemical decomposition and run-away kinetics when the propellant is in contact with transition metals. Variability in propulsive performance is thought to be a function of gun breech temperature. Pressure transients and oscillations continue to be a problem, and the observed transients have not yet been successfully modeled. Significant logistics advantages would result if the ETC gun concept could be combined with liquid propellant technology. if liquid propellant technology succeeds, the shell casing could be eliminated, allowing the entire breech to be filled with propellant. ETC enhancement of muzzle velocity would compound the increase in projective force for a given breech volume (i.e., gun tube diameter). Thus, the combination of these technologies has the potential for a synergistic combination of much greater muzzle velocity for a given caliber of gun and weight of propellant _ _ _ _ , , tclecreased weight per round and decreased system weighty, together with lower sensitivity of the munition to unintended detonation (which reduces weight and volume of packaging). Because of these potential benefits, the Army should undertake a study to see if combining the ETC gun concept with liquid propellants would lead to a technological breakthrough. Small Missile Systems for Precision Attack Small rocket, or jet propelled, missiles are both a battlefield complement to gun- fired projectiles and a potential replacement for them in meeting some AAN lethality requirements. This discussion focuses on potential substitutions as alternative means of reducing logistics burdens for AAN missions. However, the committee expects that the larger Army of 2025 (AAN forces plus Army XXT forces) will continue to use a number of complementary systems, both gun tubes and small missiles. From a logistics standpoint, missiles have an important advantage in precision guidance, which the committee believes is the most important technological route to reducing the logistics burden of ammunition weight and volume. Gun tubes have the traditional advantages of direct-fire and high-fire-rate weapons, as well as a lower acquisition cost per round and munition weight per round. (A comparison based on total cost per kill, including indirect logistics burdens for transporting "dumb" rounds in quantity, will reveal meaningful system trade-offs for AAN.) The Advanced Fire Support System (AFSS), a current DARPA program for close-support indirect fire (e.g., artillery accompanying battle force elements, as opposed to standoff platforms), illustrates the existing missile technology and emerging system concepts. An example of a potentially competitive "gun-tube" technology is the Marine Corps Dragon Fire system. The discussion below of these two systems is intended to
ENGA CEMENT 95 explore the state of the art and highlight important logistical issues, rather than argue for or against a general technology (missiles versus gun tubes) or particular system. For long-range precision artillery, at distances comparable to or greater than those of the "corps artillery" EM gun concept discussed above, missile technology offers an obvious potential substitute for gun-tubes. Cost per kill and nontechnical considerations, such as acquisition competition with other joint-force standoff platforms, may be important factors in deciding whether to develop one or both of these technology options. Missile Systems for Kinetic Energy Attack on Armor High velocity KEP ammunition can be used to attack enemy armor using conventional, ETC, and EM gun system technologies, or using missile system technology. The advantages of missile KEPs are that they can kill at longer ranges, use larger projectiles, and enable in-flight guidance. A missile system can also be used for top attack, increasing the potential kill probability against currently configured combat armor (namely, battle tanks). KEPs traditionally have been gun-launched using direct-fire aiming, which limits them to line-of-sight targeting of the front or sides of an enemy tank, which are usually better protected and harder to penetrate than the vehicle top. However, a ramjet or rocket could propel a KEP warhead over longer distances (over the horizon), and the target impact location could be precisely controlled. A disadvantage of relying on a missile system in close engagements is that a KEP missile would have to reach a speed of Mach 6 (roughly 2km/s) or more to reach maximum velocities and establish terminal guidance control. An EM gun system that could put the same energy on the target repeatedly would be too heavy for a high- mobility platform. Because of its lighter weight and greater standoff range, the KEP missile would provide the only feasible approach to meeting AAN engagement system requirements. There appears to be no perfect solution (within the time frame for fielding initial AAN capabilities), and difficult trade-offs will have to be made on the basis of thorough analyses. The Army, which is currently exploring KEP missile technology in the Compact Kinetic Energy Missile (CKEM) Program should ensure that this program and the corresponding work in EM and ETC gun development will produce the data needed for trade-off analyses, including logistics burdens and other performance measures, within the AAN decision window. General Purpose Indirect-Fire Weapons The AAN battle force will need one or more lightweight, precision-guided indirect-fire weapons. This requirement meshes well with the intent of the DARPA AFSS program, which is exploring conceptual weapons systems that combine weight reductions and ease of deployment with enhanced fire support. The program objectives of AFSS are to develop and test systems that can provide the rapid response and lethality of existing gun and missile artillery, enhance system survivability, but require significantly fewer personnel and less logistics support. The program's tasks include developing and demonstrating (1) a highly flexible system, including a guided projectile
96 REDUCING THE LOGISTICS BURDEN FOR THE ARMYAFTER NEXT or munition; (2) a remotely commanded, self-positioning launcher; and (3) a command and control system compatible with military doctrine. The system concept on which the AFSS program has focused is commonly called the Rocket in a Box. This modular rocket system is similar in design to current multiple launch rocket systems (MERS) but has more firepower, is smaller, has precision guidance, and has Tower procurement and life-cycle costs. Because it can operate with no personnel at the container site, it also reduces the need for artillery crews. The Rocket in a Box design includes four subsystems: Six Pack missiles; a container-launcher unit; a computer and communications subsystem; and a shipping container. The full development of the system will require work on launchers, munitions, seeker-designators, warheads, and guidance and control and propulsion systems. An attractive feature of this design is that the missiles in their container-launchers can be fired immediately by remote control ("cold launch"), which makes every "uncrated" container, whether sitting on a truck, tank, or land site, a potential artillery battery. Although the charter for the AFSS program seems to cover gun-tube technology as well as missile systems, the program has focused on the missile artillery option. The rationale for this choice was not clear from the materials and briefings the committee received. Presumably it reflects a perception that logistics costs for gun-tube ammunition and crews are high. The economic advantage, however, is not obvious. For comparison, the Marine Corps Dragon Fire concept illustrates a gun-tube technology option that has many of the same advantages for the AAN that the Rocket in a Box has. Dragon Fire is a robotic mortar system that folds to a mere 18 inches for transport and can remain hidden in defilade on the battlefield until called into action by remote command. It then unfolds itself within three seconds to a standing position, automatically loads its ammunition, and fires. A single gun tube can fire a variety of munitions (packed in a 32-round magazine), including a munition guided by the GPS. The 120-mm tube has a range of 13 km with rocket-assisted munitions (Roos, 1998~. Thus, Dragon Fire can provide precision attack capability from a light, portable, relatively inexpensive platform. A similar system to accompany an AAN battle force could provide significant logistics savings in ammunition, crew, and transport for both, compared with traditional crew-served mortar and cannon artillery systems. Precision Guided Munitions Whatever launch technology is used, the critical element for hitting the target with every indirect-fired round is precision guidance of the projectile to its aim point. The opening section of this chapter on SA described some of the enabling technologies for precision guided munitions. These technologies can be integrated into different guidance regimes. In some regimes, the target is identified and tracked, aim-point control data for the projectile are computed either at the launch platform or at a target designator located separately from the launch platform, and the projectile and the control data are transmitted to the projectile. For a fast-moving battle force, however, the most useful guidance regimes are those that provide "fire and forget" capability. This means that, at some point during the flight to the target, the components of the projectile itself take over the functions of acquiring and tracking the target and computing path corrections.
ENGA CEMENT Squib Fire E\tronics Acoustic Sensors (4) Wing Flaps (4) Main Charge \ - - ~ \ Power Regulator Altimeter Infrared Seeker Impact Fuse Sensor FIGURE 6-3 Major BAT subsystems. 97 Deceleration and Stabilization Subsystem i\ Curved Tail Fin (4) 'c:'·~' gallery K~ Air Data Sensor Electronic Safe and Arm Device [3^ ~ Control Actuator System , ~ Central Electronics Unit ~ Inertial Measurement Unit Precursor In this section the committee uses the Anny tactical missile system (ATACMS) and the brilliant anti-tank (BAT) submunition to illustrate how the components of precision guidance are assembled in a present day "smart munition." The committee believes that the development of BAT, which began in the early 1980s, is an excellent example of how technology can be used to provide highly reliable, inexpensive, and compact munitions that could cut the logistics burden of ammunition to a fraction of today's requirements. It also illustrates how lengthy the process from conception to fielding is likely to be for AAN systems. A BAT can locate, attack, and destroy an enemy combat vehicle, including a tank. The kill mechanism involves attacking stationary or moving vehicles from the top, where they are most vulnerable. The BAT airframe, which provides the external aerodynamic configuration for the submunition, contains all of the subsystems to perform the terminal-phase functions for homing in on the target (Figure 6-3~. All necessary location and tactical data are downloaded from the parent missile system to the BAT submunitions prior to their release. The control actuator system provides the guidance and control for the submunition, based on control data (commands) from the central electronics unit, which is the computational focal point for the submunition. The central electronics unit integrates all sensor data and mission logic and generates the sequence of computer commands to complete the mission. The computations are based on mission logic software, inertial measurement data Tom the inertial measurement unit, air speed data from the air data sensor, and acoustic data from the acoustic data sensors. A thermal battery provides electrical power for the power regulator, which in turn supplies and conditions the various electrical voltages required by the BAT subsystems. After the main missile vehicle releases the BAT submunitions, each BAT deploys a gas-inflated ram air stabilizer (GTRAS) that stabilizes and decelerates the
98 REDUCING THE LOGISTICS BURDEN FOR THE ARMYAFTER NEXT submunition to its operating speed. The GIRAS is then jettisoned, the main parachute deployed, and the wings and tad! fins configured. Still attached to the main parachute, the BAT acoustically searches for and detects the target area. Once the target area is located, the BAT cuts itself loose from the main parachute and maneuvers into a specific target area defined by acoustic target detection. When the BAT reaches the target area, a secondary parachute is deployed and the infrared (TR) seeker begins to search for and select a specific target. When the target is selected, the BAT cuts loose from the secondary parachute and glides toward the target using TR point tracking. As it closes on the target, the BAT arms its warhead and selects an aim point, using image correlation. The BAT continues to track this aim point as it guides itself to the target. An impact fuse sensor in the forward section of the airframe detects impact and signals the electronic safe and arm device to detonate the precursor and main charges in the warhead. This description illustrates the complexity of operations required for a precision guided submunition. Multiple sensing systems are used at different stages for both environmental data (to control flight and staging operations) and target detection and tracking. The control and flight regime is likely to change at each stage; the intelligence to shift from one control mode to the next must be built into the electronics and software. As the variety of targets to be attacked by precision guided munitions increases-either by making the same munition more adaptable or by developing alternative terminal- phase munitions for the same delivery system the detection and guidance capabilities of the components will have to be increased. As potential adversaries learn how a certain munition is guided, they will hunt for evasive or deceptive counteractions, which will also drive the demand for more sophisticated sensing, processing, and controls. The hardware, software, and firmware to implement these sophisticated guidance systems must be exceptionally reliable, as well as inexpensive enough to keep costs reasonable, relative to the military value of the targets. Propellants, Explosives, and Warheads The weight and volume of energetics, the energetic materials used to project a missile to its target (the propellant) and to energize or provide a warhead kill mechanism, contribute directly to the weight and volume of the ammunition logistics burden. Materials with a higher energy density may require smaller, lighter delivery systems. Energetics that are less likely to react to heat exposure or accidental shocks (as opposed to impact on target) may also be used to produce "less sensitive" munitions.2 Less sensitive munitions reduce logistics burdens by reducing the packaging weight and volume necessary for safe handling and storage. More can be transported in a given volume, because distances between rounds (the magazine separation) can be minimized. Less sensitive munitions are also less likely to cause "fratricide" accidents (the accidental detonation of one round that causes rounds stored with it to detonate as well). Preventing munitions fratricide not only increases safety but also decreases the logistical requirement for ammunition resupply and for the repair or replacement of damaged munitions and equipment. (Less sensitive munitions are also inherently safer for the 2 Miltary Standard 2105 defines an "insensitive munition" as one that passes seven tests specified in the standard. For purposes of this report, the term "less sensitive munition" refers to munitions that have been designed or formulated to be less likely to react to thermal and shock stimuli ("threat stimuli"), whether or not they meet (or exceed) the seven specified criteria for an insensitive munition.
ENGA CEMENT 99 soldiers who move and fire them.) The general challenge, then, is to develop affordable, highly lethal systems that can engage a broad range of targets and, at the same time, reduce the weight and volume of projectiles, missiles, warheads, and launch systems. The committee identified four areas of improvement in the broad area of energetic and warhead materials that could substantially reduce logistics burdens: missile propellants less sensitive munitions warhead materials and explosives multipurpose warheads In addition to research and development in these specific areas, general enabling technologies including materials processing techniques and analytical design tools (see Appendix C) are needed in all areas. Missile Propellants For many AAN operations, explosives and propellant materials and formulations will have to provide higher performance but be less sensitive to shock and thermal threats. For example, missile acceleration will have to increase dramatically over today's standards to achieve a relatively short fly-out time, the Mach 6 and higher velocities required of a missile system roughly equivalent to a gun system for KEP rounds. Missile propellants for both rocket and air-breathing (iet) propulsion will have to be throttleable, produce minimum smoke and thermal energy, and be less sensitive. For an AAN battle force in particular (but also for follow-on Army forces), missile systems with stealth and agility must be launched from small vehicles next-generation scout or utility vehicles, as well as AAN combat vehicles. Solid-fue! ramjet technology uses fuels that are not exotic and uses the air as the oxidizer (a small solid propellant booster is needed to accelerate up to Mach 2~. High- speed ramjet missiles could yield high payoffs for a lightweight AAN battle force (see Figure 6-4~. Ramjet missiles have high velocities (ca. Mach 6), can be as small as Stinger missiles, and are generally powered all the way to the target. Their range depends on their size. Above Mach 6, cooling does become an important consideration, and new materials would have to be used. Current and future generations of ramjets use gas generator chambers in which the propellant burning rate can be controlled by chamber pressure, resulting in a throttleable missile. However, new propellants will have to formulated that have a broad range of burning rates at safer low pressures to prevent the ramjet from exploding. The primary benefit of using air-breathing engine cycles in Army missile systems is the increase in propulsive energy over conventional rocket systems. This increased energy can be used to extend range or decrease time to target (or a combination of the two), to decrease the number of launchers required, to provide throttle control to enable "smart" propulsion, and to decrease missile size and weight while maintaining performance levels. Solid-ducted ramjets reduce maintenance, and liquid-fuel ramjets are available for extended high-speed cruise. Turbine engines are presently in use for long-range subsonic flight. The solid-fuel Air-Turbo-Rocket combines a simple expendable turbine
100 2 1.5 _` ~1 - F 0.5 o FIGURE 6-4 Comparison of engine technologies. REDUCING THE LOGISTICS BURDEN FOR THE ARMYAFTER NEXT 1 ¢ Turbojet Relative Engine Cost and Risk ~ , Ramjet ,, .' ~ At' J J - ~ ' ~ Scramjet 1 1 1 1 0 2 4 6 8 Speed (Mach number) with a ramjet combustor to attain subsonic to supersonic speeds, while maintaining throttle control. For high-speed systems, ramjet engines could upgrade existing missile systems for a fraction of the cost of a new weapons development program and substantially improve performance. Air-breathing engines can be expected to increase the propulsion unit cost by 20 to 100 percent over rocket propulsion. However, considerable savings can be expected at the system level, considering propulsion typically represents on 5 to 10 percent of the missile cost. Other cost factors include reduced procurement quantities because of improved coverage and reduced material losses. Fifteen years ago, many U.S. companies and the armed services were all working on ramjets. Today, only two U.S. companies have expertise in ramjets and, perhaps, only one military program is still active, the Beyond Visual Range Air-to-Air Missile (BVRAAM). In fact, the United States could lose all of its capabilities in this area, even though several foreign countries (Russia, United Kingdom, China, France, India, South ADica, Germany, Israel, and Japan) have ramjet missile systems, active flight testing, or ongoing development programs. The Army is participating in the Integrated High Payoff Rocket Propulsion Technology (THPRPT) Program to improve rocket motor performance dramatically. IHPRPT is a cooperative effort of government and private industry, with joint service participation. Its goal is to develop a strategy for doubling U.S. rocket propulsion performance in the next 15 years. Novel propellants and ingredients, higher pressure operating conditions, and multipuise and throttleable motors are all being considered. The committee believes that increased participation in this program, particularly with a clear focus on the needs of AAN systems, would be a good way for the Army to leverage its resources to reduce AAN logistics.
ENGAGEMENT Warhead Materials 101 The purpose of improving warheads for shaped charges and explosively formed penetrators is to increase the lethality of warheads. Promising materials for the mass element of the shaped charge or penekator include tantalum, molybdenum, and tungsten. These elements can be coupled with energetics in precise formulations to ensure "one hit, one kill" while decreasing the weight per round. As a prime example, shaped charge performance is strongly influenced by the precision of the explosive. Lethal performance can be increased by improving precision for a fixed energy. Multimode Warheads A multimode warhead can produce one of several compact, controllable pattern fragments, depending on the target type. For example, these warheads can be pro- grammed in the field to deliver a single explosively formed penekator (top attack on an armored vehicle); large chunky fragments (vehicles and other targets); or high blast with very fine fragments (antipersonnel and blast-sensitive targets). To reduce the logistics burden and increase versatility, the Arrny should continue to support basic work on multimode warheads. Advanced computerized detonation models are an essential aspect of this research. The Logistics Integration Agency provided the committee with an overview of relevant work at several U.S. Department of Energy national laboratories (Chase, 1998~.3 In 1994, for example, the Los Alamos National Laboratory reported that it had developed metastable interstitial composite energetic materials with the potential for tailored reaction rates with product gas conkoT that could enable warhead fragmentation patterns to be "tuned to achieve a kill while minimizing collateral damage." These materials could lead to smaller and more lethal warheads that reduce logistics burden. Smaller, highly efficient warheads could also be launched from robotic vehicles, such as UAVs or UGVs. Less Sensitive Munitions Decreasing the sensitivity of energetic materials and formulations is a difficult technical challenge because increasing the performance of a material as an energetic has historically tended to increase its sensitivity. However, if artillery rounds, warhead explosives, and missile propellants were less sensitive to impact and thermal exposure, they would not only be safer to handle, but they would also reduce logistics burdens. The most important direct consequences in terms of reducing logistics burden would be that packing densities could be increased, the amount of protective packaging could be reduced, and bulk shipping would be less complex. Because less sensitive munitions have less risk of fratricide, fewer rounds would explode accidentally during storage, movement, and handling. Box 6-1 describes the results of a Navy study indicating that the indirect effects on material costs could be substantial, in addition to reducing the risk of death and injuries. 3 Much of the work in this area is classified.
102 REDUCING THE LOGISTICS BURDEN FOR THE ARMYAFTER NEXT BOX 6-1 Benefits of Less Sensitive Munitions The Center for Naval Analyses has studied the effects of insensitive munitions on board aircraft carriers (CNA, 1991~. Actual data on deaths, injuries, and materials costs for three accidents (on three carriers) in which no insensitive munitions were involved were compared with the center's estimates if the best existing technologies (at that fume) for reduced sensitivity had been in use. Actual Estimated Consequence (no insensitivity) (insensitive) Reduction Deaths 176 72 59% Injuries 552 63 89% Materials Costs $1,966.50 $469.60 76% (1999 $ million)a aReported cost data for fiscal year 1991 increased at 4 percent per year to fiscal year 1999. The absolute numbers for three incidents may not carry over from Navy to Army environments; aircraft carriers are much more expensive than Army combat platforms, and the personnel density aboard ships is very high. Nevertheless, the percentage reductions indicate that even with 1991 technology, which has since been improved significantly, less 1 = There are many ways the Army could decrease the sensitivity of its munitions, even with current technologies. Many Army warheads still use either pressed HMX (high melting explosive) (up to 98 percent) with a binder or melt-cast explosive formulations, such as Composition B (RDX trapid detonating explosive] and TNT t2,4,6-Trintrotoluene]) or Octo! (HMX and TNT). All of these formulations are much more shock sensitive then improved formulations and will detonate when exposed to shocks of 14 to 28 kbar. Figure 6-5 illustrates the roughly threefold decrease in shock sensitivity attainable by replacing these formulations with existing PBX (plastic-bonded explosives) that have the same performance characteristics as energetics. The Large Scale Card Gap Test on which data in Figure 6-5 are based uses a standard apparatus and procedure prescribed by Naval Ordnance Laboratory Technical Bulletin 700-2. A donor charge that produces a known shock pressure is detonated against the explosive to be tested. If the donor charge detonates the test explosive when in direct contact with it, cellulose acetate cards of a standard thickness (0.01 inch) are placed between the donor charge and the test explosive. Each card attenuates the shock pressure by a known amount, represented by the curve in the graph. The point on the curve where a given explosive formulation is detonated but at which one more card causes no detonation, is the score for shock sensitivity in this test. For the test results illustrated, conventional Arrny warhead explosives had test scores of 14 to 28 kbar. PBX alternatives had test scores of 50 to 69 kbar. (Bernecker, 1988~. Beyond the substantial improvements that could be made simply by adopting the best current technologies, the development of improved energetic s must be recognized as a system design problem. Army missile propellants and explosives will have to be less sensitive to both temperature and shocks and have higher specific energy (energy per unit mass and volume) and other performance values. In decreasing the sensitivity of munitions, many factors will come into play. Shock sensitivity is usually reduced
ENGA CEMENT 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 o 103 \~ Cards a ¢ :Current Warhead Fills I' POX Warhead Fill Replacements ~11 1 1 1 1 1 1 1 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 Pressure (kbar) a 1 card = 0.010 inches FIGURE 6-5 Calibration curve from large-scale card gap tests of conventional warhead explosives used by the Army and PBX replacements. Source: Bemecker, 1988. through changes in formulation and Processing techniques. Reductions in thermal O a ~ a ~ ~ . . . .. . . . . . . . . . . . sensitivity usually require soph~shcated changes in engineering design of the to configuration and casing to provide adequate venting under either slow or fast heating rates. Energetic s performance and sensitivity to diverse threats must be considered in the context of increasing the accuracy of targeting through precision guidance and SA. Smokeless rocket propellants are being developed today that have increased specific impulse but are less sensitive to shock. Plastic-bonded explosives dramatically reduce shock and thermal sensitivities. For example, the Air Force warhead explosive AFX-235 has the performance characteristics of an explosive that contains 96 percent (by weight) HMX, although it contains only 75 percent HMX in an energetic plastic- bonded binder. Shock-sensitive weapons or munitions could be more closely spaced by the clever use of mitigating materials (closely related to the development of armor materials) and by unique packaging layouts based on computerized shock models. Thermal threats could be mitigated by active or passive venting. The Navy has implemented a variety of concepts for less sensitive munitions, including the strategic use of barriers and mitigators. The Army, however, has only begun to recognize the logistical (and safety) implications of reducing munitions sensitivity. In terms of logistics burdens, more rounds can be stored in the same area if they are less sensitive, or an equivalent number of rounds (or equivalent amount of lethal force per projectile) can be stored in a smaller area. Platforms and operations can be designed to allow personnel and equipment to operate in closer proximity to ammunition stores. The chances of transportation or handling accidents would be reduced, as well as the logistics and operations planning margins, and the safety of Arrny personnel would be increased. If the AAN process forces the Army to design for the best systems solutions for achieving diverse performance goals, including substantial reductions in the logistics burdens of ammunition and lethal systems, the Army will have a golden op- portunity to make decreased munitions sensitivity a serious cost trade-off.
104 REDUCING THE LOGISTICS BURDEN FOR THE ARMYAFTER NEXT Logistics Implications of Projectile Weapon Systems The foregoing discussion has only touched on the surface of potential system and application concepts, their potential logistical consequences, and the technological opportunities and issues relevant to providing projectile weapons for an AAN battle force. Even this limited review, however, demonstrates that there will be no obvious winners among the alternative systems. In many instances, data are not sufficient to make quantitative comparisons, particularly with respect to the logistical implications of an entire weapons system concept. Should an AAN "main combat vehicle" be armed with an ETC gun, an EM gun, or an improved missile system? Which alternative has the least logistics burden for an implementation that could be in the field by 2025? Would a general switch to liquid propellants meet AAN engagement needs while reducing logistics burdens? Which approaches to precision guidance will guarantee that every round hits its target? The answers to these and other questions will be required to support design decisions that must be made by 2010, ~5 years before the AAN becomes a reality. The general argument advanced in Chapter 3 for a systems engineering approach to logistics trade-off analyses will be crucial for selecting new projectile weapons for AAN. Current Army and joint programs run the gamut of research and development in the technologies for projectile weapons. Except for some of the electronics for enabling precision guidance, nondefense commercial markets will not take the lead or be a source of innovation. However, the Arrny can leverage the R&D program base in projectile weapons that already exists. The goal of many of these programs was, and still is, increasing lethality, not reducing logistics burdens. Fortunately, "one round, one hit, one kill" has substantial implications for both. But these programs have different constituencies responding to different requirements. Even for nonIogistical performance objectives, there are no common criteria for program success. The Army should try to coordinate resources from these programs for trade-off analyses of AAN engagement systems. First, the Army will have to formulate the questions about AAN performance capabilities that must be answered in teems that apply to the candidate projectile weapon systems. These performance capabilities must include logistical performance as a primary objective, not as an afterthought. Second, each existing program that supports a weapon system concept must be evaluated to determine whether, and in what time frame, it might provide answers-or the data needed to mode! solutions that will provide the answers to those questions. Finally, the Army should make adjustments to programs to ensure that answers will be available in time for AAN decisions on system designs. In many cases, existing concept demonstration programs will have to be modified to ensure that they provide sound data on logistics support requirements that can be fed into platform models and engagement models in the M&S hierarchy described in Chapter 3. If the current state of knowledge cannot support a technical basis for acquiring essential data empirically or for constructing a validated simulation to model it, the Anny might have to support applied or even basic research. DIRECTED ENERGY WEAPONS Directed energy weapons, which use electromagnetic radiation as their lethality mechanism, include laser, high-power microwave, and high-power millimeter wave systems. Because their lethality mechanism is the transfer of energy from this radiation
ENGAGEMENT 105 to the target on which it is focused, there is no mass or volume of ammunition, as there are with projectile weapons. Instead, the logistics burdens are the fuel and energy to supply the high power demands of these weapons, the weight and volume of the pulsed power subsystem that stores and transfers electrical energy, and the weight and volume of the subsystem that creates and directs the pulses of radiation at the target. For weapons systems that accompany an AAN battle force to the area of operations, the energy needed to recharge the pulsed power storage subsystem must be supplied by the battlefield fuel carried with the battle force or by some other store of energy, such as primary batteries. The conversion of fuel energy to electrical energy for the weapon power supply must be included in the sizing of the system that does the conversion- most likely the power plants in combat vehicles. Barring an unanticipated paradigm-altering discovery about the fundamental physical mechanisms on which directed energy technologies are based, the committee believes the position stated in the STAR 21 study remains valid. in the AAN time frame, directed energy weapons will be feasible options as tactical systems for antisensor, antiprecision guidance, and anti-SA weapons. It will not be feasible to develop directed energy weapons systems for heavy-duty structural attack, particularly for the highly mobile operational concepts envisioned for an AAN battle force. The STAR 21 report predicted that "heavy-duty directed energy weapons for vehicle kill against aircraft, missiles, and spacecraft are likely to develop first, if at all, as strategic defense systems" (NRC, 1992, p. 86~. Transportable versions of directed energy systems, probably developed for the defense of the continental United States, might eventually be usable in an AAN staging area, if adequate energy were available and if the battle force operation was vulnerable to antisensor and anti-SA weapons. From the standpoint of reducing logistics burdens for an AAN battle force, however, tactical directed energy weapons would complement and supplement projectile weapon systems, not replace them. Therefore, they represent a separate and additional class of logistics burdens. Lasers Various types of lasers have potential as offensive weapons against small and large protected targets, but they would require very high power densities and durations on target, as well as a direct line of sight to the target. The Night Vision Electronic Sensors Directorate of the Army Communications-Electronic Command (CECOM) has defined a notional directed energy warfare vehicle (DEW-V) that could serve as a "virtual test-bed" to determine the operational effectiveness of vehicle-mounted directed energy weapons for battle scenarios in 2015 and beyond. Although there is no hardware development plan, the concept may be expanded to include development of a DEW-V around an Abrams tank chassis or a Bradley fighting vehicle chassis for Army XXI (Knowles, 1996~. Because lasers use discrete wavelengths (primarily in the IR region), care must be taken to avoid wavelengths that can be degraded by atmospheric conditions. For example, the Navy stopped work on its high power deuterium fluoride laser because the laser could not accommodate extreme environmental conditions (Knowles, 1996~. A more practical use for lasers and other electromagnetic radiation beams, achievable in the near term, is to use them as antisensor weapons to disable the enemy's sensors and defend against enemy projectile weapons. The electro-optical sensors used
106 REDUCING THE LOGISTICS BURDEN FOR THE ARMY AFTER NEXT for precision guidance of smart munitions are vulnerable to laser attack. Tactical lasers that can put energies on the target of more than ~ k] are feasible. Tactically useful free- electron lasers (FELs) in the megawatt power range may be possible, although to date only low-power FELs have actually been built (Knowles, 1996~. One disadvantage of using lasers, even as tactical antisensor weapons, is the political and geopolitical ramifications of their use. Because they can cause permanent eye injury, lasers have been banned by international treaty agreements. Because current electro-optical sensors are also vulnerable to laser attack, both the CECOM and the Natick Research, Development and Engineering Centers have been working on notch filters to protect human eyes and electro-optical sensors from the discrete wavelengths used by lasers. The principal enabling technologies for laser weapons are efficient high power generators, efficient lasers, infrared sensors, and advanced processors and target extraction algorithms (DoD, 1998a). All of the services, and many of the national laboratories, are currently conducting research on lasers. The Air Force in particular has an extensive airborne laser program. The committee recommends research groups involved in these programs coordinate to leverage resources and avoid wasteful duplication. For a laser antisensor weapon to be incorporated into AAN combat vehicles. the power requirements for the laser and the sizing of the weapon system will have to be known before the Army can make realistic estimates for modeling its vehicle design (see Chapter 5~. Microwave Devices Smart weapons that depend on electronic components for precision guidance are vulnerable to high-power electromagnetic energy that overheats these components to the point of breakdown. Therefore, directed energy weapons are prime candidates for defensive applications. The effects of high-power microwaves (HPM) on electronics are similar in this respect to the electromagnetic pulse (EMP) from the detonation of a nuclear warhead, except that the HEM frequency range (0.5 to 100 GHz) is significantly higher. These microwaves can penetrate electronic systems either through the target system's antennas or through energy leakage into electronics enclosures. With its high frequencies, HPM can destroy electronic components that would not be affected by a nuclear EMP pulse. HPM weapons could disrupt or damage communication systems and the electronic subsystems of weapon systems, smart munitions, and airborne or ground vehicles. HPM could also affect friendly forces. For example, stealth coatings are designed to absorb microwaves, and an HPM pulse could have a thermal effect much like the effect of a microwave oven. Another drawback of HPM weapons is that the antennas will have to be large and located in the enemy's line of sight. These antennas have a significant EM signature, which would make them easy for an opponent to find and attack (Herskovitz, 1993~. High-power millimeter wave (HPMM) systems also appear to have great poten- tial. In short-range engagements (2 to 5 km), the power densities at the target would be almost the same as at the antenna. An advantage of millimeter waves over laser systems is that they can be used under a wider range of weather conditions. Progress continues to be made in the development of HPMM generators. The principal enabling technologies for HPMM weapon systems are efficient power sources, HPMM generators, precision
ENGAGEMENT 107 large antennas, advanced passive electromagnetic sensors, and advanced processors and target extraction algorithms (DoD, 199Sa). LESS-THAN-LETIIAL WEAPONS Like today's Army, the AAN will face a wide array of adversaries. With "less- than-lethal" (LTL) weapons, the battle force would be able to make a measured response to an attack or provocation, facilitate the control of opposing forces, and avoid collateral casualties in situations, such as urban warfare. These objectives are very different from the objectives of destroying opposing forces with projectile weapons, which have the unfortunate side effect of harming noncombatants who happen to be in their effective range. LTL weapons include sticky foams, stun guns and bombs, bright-light flashes, and rubber bullets that can temporarily incapacitate opponents. Other techniques for controlling populations are disrupting communications and degrading infrastructure. Much of the technology development for less exotic LTL weapons has been led by the U.S. Department of Justice and civilian law enforcement agencies, mainly for crowd control or for use by special teams in hostage situations. A unique LTL approach with applications to urban warfare may be to capitalize on resonances with the human body. For example, the resonant frequency of a human chest cavity is about 20 Hz, and the frequency of brain waves is between ~ and 40 Hz. Matching those frequencies "resonantly" with a high-energy source could instantly incapacitate someone. A prototype pulse detonation engine has a frequency of about 15 Hz. The sound power level from this engine is extremely high-on the order of bets, rather than decibels, and resonant coupling with brain waves could seriously impair an adversary. A war-fighter would not have to be in the area of the conflict for this device to be effective. Like directed energy weapons, LTE weapons are likely to complement and supplement projectile weapons rather than replace them. Therefore, they will often add to logistics burdens by increasing the numbers and variety of systems required in the battle force's inventory. However, logistics efficiencies could be achieved by including logistics considerations in the design and development of LTE weapons. SCIENCE AND TECHNOLOGY INITIATIVES TO REDUCE LOGISTICS BURDENS OF ENGAGEMENT SYSTEMS Based on the preceding analyses of the logistics burdens assoc iated with engagement system options for AAN battle force operations and the technological opportunities for reducing these burdens, the committee concluded that the Army should pursue the following areas of scientific research and technology development. The order of the numbered items under a heading reflects a rough order of priority. Situational Awareness I. Continuation of SA Technology Insertion beyond Army XXI. Technologies that support near-perfect, near-real-time SA will be critical enablers for AAN engagement systems. The direct and indirect consequences of ensuring SA range from enabling effective support from standoff platforms, being able to deliver "just the right amount"
108 REDUCING THE LOGISTICS BURDEN FOR THE ARMYAFTER NEXT of logistics, and the right-sizing of battle force elements to providing the battlefield intelligence required for "one round, one hit, one kill" precision in indirect-f~re engagements. SA will thus be the single most significant determinant of both AAN combat effectiveness and the reduction of logistics burdens. Rapid innovations in the underlying technologies, most of which will continue to be driven by commercial market forces beyond the control of the military, will provide opportunities for improving SA but will also force the performance levels to rise continually for maintaining technological overmatch against potential opponents. The Army should not assume that "digitizing" the Army XXT force, through introduction of today's (or even the next decade's) state-of-the-art technology for information acquisition, processing, distribution, and representation, will suffice for the AAN in 2025. To ensure that AAN battle forces always have superior SA, the Arrny will have to find ways to upgrade the underlying technologies incrementally, within resource constraints, while maintaining system integrity. 2. Precision Guided Munitions. The precision guidance of projectiles (or other weapons effects, such as directed energy or LTE weapons) is the primary means of reducing the ammunition logistics burden. This burden has traditionally been second only to fuel in the weight and volume required per unit of combat effectiveness. As the battle space defined by lethal reach expands spatially but shrinks in time, precision guidance technologies will determine how well a force can effect "one round, one hit, one kill." Much of the information on state-of-the-art technologies and research to improve guidance systems is classified and, therefore, not available for this study. The committee assumes that the Army will continue its support of precision attack systems for the AAN. 3. Vulnerability of SA to Cascading Failure. A weakness or flaw in the technology on which SA depends could have catastrophic consequences if the system is vulnerable to single-point failure-or even to multiple-point failure. The commercial markets that drive many of the core technologies for SA subsystems and components can tolerate more vuinerabilities than the Army and the national defense generally. To the extent that SA elements are joint systems, the Army should encourage, and even demand, joint efforts to ensure that the AAN battle force is not defeated because of an SA failure stemming from a flaw in a communications network, computer operating system, or other technology built from commercially developed components. The same rigor will be necessary for SA elements developed and controlled by the Army. During AAN war games, the Army should allow the opposing forces to attack SA infrastructure and should mode! the failure of different SA elements to uncover vuinerabilities. Projectile Weapon Systems 1. Logistics and Performance Trade-off Analyses for Projectile Weapons. The committee found no clear, obvious winners among the potential alternative technologies for the main armament of an armored AAN combat vehicle or close-support artillery. Even on the level of broad technology options, such as liquid propellants, the available information is insufficient to make an informed choice, either on the basis of logistics burdens or trade-offs in which logistics is included with other performance characteristics. To remedy this situation, the Army should leverage the existing research
ENGA CEMENT 109 and development program base in projectile weapons and supporting technologies to obtain data for modeling system alternatives and making well grounded trade-offs. Data on logistics burdens should be among the required data about each enabling technology or system concept. By assessing disparate programs and developments from the standpoint of their contributions to the hierarchical simulation of system options and making informed design trade-offs, the Army will be able to determine where modifications or additions to the science and technology base should be made. 2. Systems Design Approach to Increasing Lethality of Energetics and Warhead Materials while Decreasing Weight, Volume, and Sensitivity. The most important enabler for reducing the logistics burden of ammunition (after precision guidance of munitions) is to increase (or at least maintain) lethal effectiveness per round while decreasing the total logistical weight and volume per round. The complexity of the issues, diversity of performance objectives, and broad range of technological opportunities will require a systems design and trade-off approach to achieve the best combination of technology for AAN needs. For example, the Army needs missile systems that are small and affordable enough to be incorporated into large numbers of smaller vehicles. The missile propeliantts) for such systems must enable higher acceleration, minimum smoke, less sensitivity to shock and thermal threats, and capability for precision guidance (i.e., controllable burn rate). New energetic materials and formulations must increase energy (or rate of energy release) per unit mass and volume of propellant or warhead explosive, while making the munition less sensitive. More effective warhead materials and multimode warheads can increase lethal effectiveness by ensuring that each hit is a kill. As the Army looks for ways to focus and strengthen its program to improve energetic s and decrease their sensitivity, it should attempt to leverage the very active Navy program in this field. Directed-Energy and Less-than-Lethal Weapons 1. Directed-Energy Weapons to Supplement, Not Replace, Projectile Weapons. The committee agrees with the STAR 21 study, which predicted that tactical directed- energy weapons would not be feasible for heavy-duty structural attacks on opposing platforms, weapons, or missiles and projectiles in the 2025 time frame. The logistics implications of these weapons-in terms of system weight and energy requirements- also preclude their consideration as weapons for an AAN battle force. However, tactical directed-energy weapons that can attack sensors, guidance subsystems, and electronic components are likely to be ready and useful for AAN operations. These tactical weapons would supplement, but not replace, projectile weapons. Their logistics burdens, therefore, constitute a separate class from those of projectile weapons. 2. Less-Than-Lethal Weapons to Supplement Projectile Weapons. LTL weapons for use in special situations, such as urban warfare, or for incapacitating opposing troops will be another supplement to the AAN engagement arsenal. From the standpoint of logistics burdens, however, they are not an alternative to projectile weapons.
