2
Assessment of the ONR ASWT Program

INTRODUCTION

The Office of Naval Research's (ONR's) Air and Surface Weapon Technology (ASWT) program addresses a range of technology issues related to weapons for air superiority, precision strike, naval fire support, and ship-based defense. In addition the program includes 6.1 and 6.2 supporting science and technology (S&T) program components related to the operation and control of uninhabited combat air vehicles (UCAVs). Of necessity the coverage of these areas (air superiority, precision strike, naval fire support, ship-based defense, and supporting S&T) by ONR's ASWT program is not comprehensive.

AIR SUPERIORITY

Overview

Air superiority depends on many factors, including pilot training and tactics, aircraft signature suppression, airborne sensors, support by early warning sensors, effectiveness of suppression of enemy air defense (SEAD), efficiency of air-to-air-weapons, and the effectiveness of electronic countermeasures. In the mission area of air superiority, ONR's work is focused only on air-to-air weapons, directed exclusively to the following themes:

  • Rocket propulsion technology,

  • Missile kinematics,

  • Seeker performance,

  • Ordnance lethality, and

  • Affordability.

Air-to-air weapons are common to both the naval air forces and the U.S. Air Force, neither of which can act independently in regard to their development. The overall air-to-air weapons thrust of the naval



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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program 2 Assessment of the ONR ASWT Program INTRODUCTION The Office of Naval Research's (ONR's) Air and Surface Weapon Technology (ASWT) program addresses a range of technology issues related to weapons for air superiority, precision strike, naval fire support, and ship-based defense. In addition the program includes 6.1 and 6.2 supporting science and technology (S&T) program components related to the operation and control of uninhabited combat air vehicles (UCAVs). Of necessity the coverage of these areas (air superiority, precision strike, naval fire support, ship-based defense, and supporting S&T) by ONR's ASWT program is not comprehensive. AIR SUPERIORITY Overview Air superiority depends on many factors, including pilot training and tactics, aircraft signature suppression, airborne sensors, support by early warning sensors, effectiveness of suppression of enemy air defense (SEAD), efficiency of air-to-air-weapons, and the effectiveness of electronic countermeasures. In the mission area of air superiority, ONR's work is focused only on air-to-air weapons, directed exclusively to the following themes: Rocket propulsion technology, Missile kinematics, Seeker performance, Ordnance lethality, and Affordability. Air-to-air weapons are common to both the naval air forces and the U.S. Air Force, neither of which can act independently in regard to their development. The overall air-to-air weapons thrust of the naval

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program air forces, the U.S. Air Force, and ONR is to continue with existing AIM-9X-and AIM-120-class missiles and to concentrate on preplanned product improvements (P3Is) in the areas of propulsion, off-bore-sight capability, hard-kill countermeasures, and integration into a network-centric model. The stated long-range goal is to have a single, dual-range, air-to-air weapon by about 2015. Given the recent history of air warfare, these objectives may seem to be legitimate. Since the war in Vietnam the United States has not lost a fighter in air-to-air combat. However, the United States may have been lulled into a false sense of security. Recent advances in foreign air-to-air missiles such as the AA-11 and Python-IV find the U.S. Navy lagging in several areas of missile performance. In the continuum of air warfare, U.S. capabilities that include the airborne warning and control system (AWACS), electronic intelligence (ELINT), National systems,1 aircraft performance, electronic warfare, and pilot training have given this nation an edge that has resulted in an enviable record in recent air combat. Comments on Program Components With such supremacy in air-to-air combat and the heavy emphasis on strike warfare, the natural tendency is to assume continued supremacy and devote fewer resources to air-to-air missiles and their capabilities. However, the Navy and Marine Corps especially could be faced with a worthy opponent in a come-as-you-are fight, without the vast support resources that have come to be expected and demanded since the Persian Gulf and Kosovo engagements. For this reason, the committee believes that the ONR ASWT program must continue to maintain detailed awareness of the technical developments of other countries and must ensure that U.S. capabilities under development are at least as good as those, if not better. The air-to-air weapons component of ONR's ASWT program is designed to be evolutionary in nature. Performance improvements have been incremental but steady. The technology being used is at the forefront of propulsion and warhead technology. Current weapon performance is significantly better than it was 10 to 15 years ago. The ONR ASWT program has time-phased goals for 5, 10, and 15 years into the future. Although goals such as a 25 percent increase in weapon range (for the same weapon volume) and a 15 percent increase in weapon velocity may seem relatively modest, meeting them may well make the difference between success and failure in air-to-air combat. Air-to-air weapon research is a relatively mature field where current weapon capabilities may be well up on the curve of realizable performance. The committee believes that as long as modest, but significant, improvements in performance can be achieved at reasonable cost, the ONR ASWT program should continue to support such work. However, the committee cannot escape questioning the merit, on these terms, of some of the current effort. For example, success in a short-range air-to-air encounter depends among other things on how far off-bore-sight an infrared (IR)-guided weapon can be fired. If one asks what an incremental improvement in an off-bore-sight capability translates into in the time domain, the answer is generally about a few tenths of a second. While the ONR ASWT program is addressing this problem with considerable success, the committee does not find very reassuring the prospect of future air superiority depending on such marginal gains in capability. The committee 1    The term “National” refers to those systems, resources, and assets controlled by the U.S. government, but not limited to the Department of Defense (DOD).

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program recommends that ONR devote more effort to the development of improved sensors and weapons that will provide situational awareness such that (even under restrictive rules of engagement) air targets can be engaged at much longer standoff ranges than current capability permits. Naval forces depend on short-and medium-range weapons today because of limits imposed by the rules of engagement. As a result, engagements occur with weapons that do not offer significant performance margins over those of potential adversaries. Being able to fire 5 degrees further off-bore-sight will not give a robust margin. New approaches should be sought toward meeting the objective of eliminating close-range air-to-air engagements, and the survival of U.S. aircraft should be supported by more than a marginal enhancement of current off-bore-sight capability. The committee was surprised to learn that the ONR ASWT effort did not include evidence of lessons learned from available information on Russian missiles, nor of incorporation or reverse engineering of Russian missile advantages into U.S. missiles. In the area of seeker performance the committee is convinced that the United States must not lose its advantage in acquisition range. Information on off-bore-sight angle acquisition and track capability should be shared with those friendly air forces that may have capabilities that exceed those of the United States. The United States holds advantages in ordnance lethality, and ONR's efforts in this area are exciting, particularly with respect to accuracy and payload size. Missile size is important, particularly in stealth platforms with internal carriage requirements. If a missile cannot be accommodated internally in a stealth aircraft, much of the advantage of the stealth treatment may be lost. One area not mentioned in the ONR ASWT review presentations related to air-to-air guns. It appears that U.S. leadership in this area of former dominance has been ceded with the announcement of the gun selection for the Joint Strike Fighter. The ONR ASWT program does not appear to be considering the development of a follow-on gun to the widely successful M-61-A1 cannon. Conclusions The committee's conclusions for the air superiority mission area of ONR's ASWT program are the following: Improvements continue to be needed in missile kinematics, enhanced seeker performance, increased off-bore-sight capability, and enhanced warhead lethality. Efforts should be increased toward sensors, weapons, and concepts of operations that will allow engagements at ranges beyond those currently projected for missiles, with the objective of reducing the occurrence of short-range air-to-air encounters. Recommendations Air Superiority. Taking into account the strong industrial capability in this area, institute systems studies to define sensors, weapons, and concepts of operations that will reduce the occurrence of short-range air-to-air engagements. Program component effort should continue toward significant and low-cost improvements in missile kinematics, seeker performance, off-bore-sight capability, and warhead lethality.

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program PRECISION STRIKE Overview The major problems encountered by the Navy and the Marine Corps in the mission area of precision strike are related to the following: Targeting of fixed, relocatable, moving, and ephemeral targets; Automatic target recognition (ATR); Response time for delivery of weapons to the target; Warhead lethality; Weapon range; and Weapon guidance. The current ensemble of precision strike weapons is usually considered to include accurate air-launched weapons (laser-guided bombs, the standoff land-attack missile [SLAM (ER)], the joint stand-off weapon [JSOW], the joint direct-attack munition [JDAM], the high-speed antiradiation missile [HARM] and sensor-fused weapons [SFWs]), and variants of the Tomahawk missile. In the area of precision strike, ONR's ASWT program is focused on the following themes: Responsive and accurate fire control, Precision target handoff, and Weapon sensor performance. When fixed targets are attacked, the guidance of existing weapons is generally dependent on a guidance system that uses an inertial measurement unit (IMU) that is updated by Global Positioning System (GPS) measurements. Image correlation techniques are also used for terminal homing. Weapons, such as HARM, home on the radiated signature of their intended target. Sensor-fused weapons operate on a variant of ATR, in the sense that they recognize and home on specific features of the target's signature (acoustic spectrum or IR signature). Jamming is a problem for some GPS-guided weapons. Of all the GPS/IMU-guided weapons, the performance of the Tomahawk missile is the most robust in the presence of GPS jamming. JDAM with short-range GPS/IMU guidance is also relatively immune to jamming. Unfortunately, the performance of many other U.S. GPS/IMU-guided weapons would be degraded by GPS jamming. If the effects of GPS jamming cannot be mitigated, many U.S. GPS-guided weapons will be ineffective. Approaches to mitigation of the effects of GPS jamming include an increase in the power radiated from the satellite, the use of alternative navigation systems such as terrain-aided navigation, null-steering antennas, pseudolites, improved signal processing, and extremely low-drift IMUs. Although a program in GPS anti-jam technology exists within ONR's precision strike area, navigation assurance is not one of ONR's major thrusts or “spikes.”2 If a target is relocatable, the problem is basically one of improving system reaction time in a series of interrelated definable steps. A relocatable target must first be geo-located by a sensor system. Target coordinates must be passed to strike planners who must then designate mission responsibility for 2    This concept is discussed in Chapter 1, in the section “Favorable Aspects.”

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program engaging the target to a weapon-launching aircraft, to a Tomahawk-type missile, or to an extended-range, guided missile (ERGM) firing platform. The objective (allowing for the time of flight [TOF] of the weapon to the last known target location) is to shorten the entire time of the chain of events from target detection to target kill, including the weapon's TOF, so that the target does not have a chance to relocate or hide before the weapon arrives. If the target has relocated (or was originally in motion when first detected) its position must be reacquired by a sensor, and new target coordinates must be provided to either the weapon in flight or its launch platform, or both. To achieve the affordability objective, there is an inherent need for a low-cost data link to a weapon in flight so that it can be redirected to a position such that the weapon's sensors can reacquire a relocated or moving target. This issue is not being addressed in ONR's ASWT program. Ephemeral targets represent an extreme example of a relocatable target in the sense that they are exposed to detection for periods of time that are short compared to the TOF of even hypervelocity weapons. Such targets can be destroyed only when a loitering platform with an appropriate sensor can detect the target and provide information that will initiate the launch of or guidance for in-flight short-TOF weapons. Clearly the most significant problems in precision strike are those of command, control, communication, and intelligence (C3I). The internal taxonomy of ONR is such that issues related to C3I are not the responsibility of the ASWT program. A coherent program component that addresses the critical problem areas that need attention in both precision strike and naval fire support does not exist within ONR. The ONR effort in precision strike consists of several program components with specific performance goals, base lined relative to 1995 weapon capabilities and time phased for completion by 2005, 2010, and 2015. The ASWT program's systematic linking of goals, objectives, technical challenges, and approaches (GOTChA), summarized in a chart presented to the committee, appears to be a useful technique for defining a path to future weapon technology. However, as presented, the flow-down pattern displayed within the individual GOTChA charts in the precision strike mission area tended to expand into what appeared to be a varied and disjointed set of projects that were force-fitted into the related GOTChA chart. Some of these efforts appeared to have been created with clear goals in mind. However, others appeared to have been allowed to proceed in isolation, without consideration of emerging alternatives and advances in the areas originally addressed. For instance, the “target/weapon pairing rate” and “GPS guidance” performance goals for 2005 as stated in the presentations on precision strike will be greatly exceeded in 2003 by the planned Tactical Tomahawk System without any need to benefit from ONR's technology effort. Although it may simply represent a failure in communication, this discrepancy leads to uncertainty about the coherence of the overall approach, in a broader view, and the value of some specific efforts. As a total set, the precision strike systems concepts did not appear to be sufficiently “system engineered” to allow a meaningful evaluation of the technologies' potential to evolve into an affordable set of strike weapon systems. Some of these components might appear to offer the Navy and Marine Corps the prospect of a significant enhancement in warfighting capability. However, they will be non-contributors if they require major breakthroughs in other technology, or if they require unaffordable changes in other systems needed to support the use of the new technology. The committee suggests that ONR support systems studies to identify the utility of some of the specific technologies in which it is investing its funds. A case in point might be an analysis of a program component for the development of hypervelocity weapons. The first issue to be resolved would be how the targeting process for such a weapon concept would operate. Would there be a maximum allowable time for mission planning after target detection? If that time budget were not achieved, would the

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program hypervelocity weapon still have tactical value? If so, how would the required reduction in the mission planning cycle be achieved? Systems studies focusing on such questions might result in a refinement of system concepts so that quantitative evaluations could then be done. Such studies would enhance critical decision making about which concepts to continue and which to abandon. An investment of this nature by ONR would provide a good return to ONR management as well as provide a quantitative rationale for technology transfer to key acquisition programs. It appeared to the committee that the overall set of precision strike projects could have a closer correlation with the ongoing acquisition programs they propose to augment in the future. Based on the material presented in the review, the committee concluded that a better alignment of the technology developments with the plans, goals, and schedule of these acquisition processes would focus investment toward those high-payoff concepts that have a reasonable chance of making a transition into the targeted acquisition programs. As a technology matures it must become increasingly aligned with the acquisition schedule. At the point of highly probable transition it must become incorporated into the acquisition schedule. This approach would present greater opportunity for ONR 6.3 and advanced concept technology demonstration (ACTD) efforts to join with, or serve as surrogates for, acquisition, demonstration, and validation, which have been largely eliminated by acquisition reform. Comments on Program Components Because of the diversity and extent of the program components in the precision strike area, the committee believes that it is appropriate to comment on each of the individual major efforts being pursued in this mission area. LADAR Automatic Target Recognition for Cruise Missiles The use of lasers on weapons has advantages in that they measure geometry, which is inherently stable. However, in the design of a weapon sensor to detect a mobile or moving target, consideration must be given to the overall system. The LADAR concept described in the program review might be useful. However, it is the committee's belief that the requirements need to be better understood. Answers should be provided to questions such as the following: What is the allowable false alarm rate? What is the required probability of correct identification? What other inputs can be used to augment the seeker? What sensor range is required under what weather conditions? Can other systems be used to narrow the search pattern and reduce the seeker requirement? A system study would indicate what target accuracy and what precision of target identification are achievable. Better targeting accuracy and increased precision of target identification would help to reduce the number of weapons expended on decoys and other false targets, increase the probability of correct identification, and relax the range requirement on the sensor. Understanding the context will crystallize the requirements for, and focus the design of, a seeker. The objective of this effort should be to develop a single sensor that can operate within a system (including reconnaissance sensors, command and control [C2], planning, and weapon seekers) to kill multiple movable or moving targets inexpensively.

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program The committee suggests that this effort be continued, and be supported by a re-evaluation of the total system concept. Responsive and Accurate Fire Control The committee found the discussion of this program component to be confusing, with several different objectives appearing to be intermingled. This apparently overarching program component includes the four tasks discussed immediately below. Precision Standoff Weapon Control The presentation on precision standoff weapon control made reference to the automatic generation of templates that would simplify the reporting over a weapon data link of data related to objects detected in the field of view of a weapon's sensor. This task will result in the achievement of an impressive capability if the predicted results can be realized. It is the committee's judgement that this task should be pursued to completion. Land Attack Battle Damage Indication The approach taken to battle damage indication appears to be appropriate. The work on high-range-resolution synthetic aperture radar under this task is generally well thought of in the precision strike community. The particular work discussed in the presentation to the committee may be somewhat dated because of the new Sandia Lucid Eyes system for land battle damage assessment. No contractor was mentioned in the presentation; however, Sandia National Laboratories is doing excellent work in this area with the specific application of Lucid Eyes. The committee suggests that the need for this task be re-evaluated in view of other work being done by other performing organizations. Precision Target Handoff The objective of the work under this task is precision target coordinate description and handoff for first-pass attack capabilities against targets of opportunity. The effort appears to be very similar to the controlled imagery rapid targeting approach being developed under the sponsorship of the Naval Air Systems Command (PMA-281). Based on the presentation, the goal is to get the target information into an airborne platform. Given that the efforts appear to be duplicative in some areas, the complementary nature of the tasks should be investigated. The committee suggests that this task be continued subject to a re-evaluation to determine if duplication of effort exists. Tomahawk-Predator Advanced Relative Targeting The concept of Tomahawk-Predator advanced relative targeting (TOPART) requires significant coordination between uninhabited air vehicles (UAVs) and incoming missiles. Conceptually, ship-or air-launched missiles must arrive within 10 minutes of identification and geo-location of a target by a UAV. Depending on the shooter-to-target range and on the weapon's velocity, this constraint might imply that a missile must be launched before the target's coordinates are actually obtained. Because UAVs are slow there could be significant time lags between different aim-points. It is not clear that a

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program system concept has been developed or that one exists that is practical. Questions to consider are the following: How is the UAV initially cued? What type of target is under consideration? Are ground observers designating time-critical targets? Can the UAV get there in time? What are the volume and speed of the aim-points generated versus the requirements? How dependent is the UAV on the GPS, and what is the impact of GPS jamming? Does this concept represent a significant improvement in accuracy over current systems coupled with anticipated improvements in GPS? The committee suggests that this task be re-evaluated from a total system perspective. The committee suspects that the view of the component might be too restrictive or that it might have an inherent capability to address a broader situation than the one presented. Weapon Sensor Performance The objective of the weapon sensor performance program component is to maintain a 3-meter circular error probable (CEP) in the presence of adverse weather, clutter, and GPS jamming. Three approaches to this ensemble of problems are being considered. One approach is to develop an inexpensive millimeter-wave seeker to increase weather penetration and to apply microelectromechanical system (MEMS) technology to aircraft and missile antennas to reduce costs. The millimeter-wave sensor and the employment of MEMS technology are sound ideas. However, the work as presented might have been overtaken by events. Some excellent work sponsored by the Defense Advanced Research Projects Agency's (DARPA's) Discoverer II—global moving-target-indicator (MTI) radar constellation—program will demonstrate, at the end of 1999, results based on the same approach. The committee suggests that this particular effort be re-evaluated in light of progress made by other organizations. In an effort to improve seeker performance in the presence of clutter and GPS jamming, specific signal-processing algorithms have been selected for implementation. The one being implemented for the purpose is one of the better algorithms. It is very fast, is of good quality, and directly supports progressive transmission. The effort described to the committee in the presentation is scientifically and technically sound and shows progress toward meeting the objectives. The committee hopes that ONR's efforts to produce robust, fast, noise-free compression for low-bandwidth transmission will continue to be supported along with the effort to develop a robust embedded zero-tree wavelet compression algorithm such as that described in the presentation to the committee. The committee believes that ONR's work on negating GPS jamming is of excellent quality but is inadequate in its scope. Specifically, it does not include development of high-performance nulling antennas for small-diameter weapons, application of coating technology to increase the value of body shielding, development of deep integration of GPS and the inertial navigation system (INS) through the application of improved Kalman filters, and development of an ultralow-drift, cheap INS. The work on bio-vision processing is attempting to identify and select a target aim-point with minimum computer capability. The approach is to examine analog and digital signal processing based on insect models, and then to transfer fly-eye strategies to IR focal phased array sensors in weapons. The work is interesting and imaginative, but based on the material presented, it is not clear that emulat-

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program ing an insect's visual processing will help with target identification, target tracking, and/or clutter cancellation. Hypersonic Strike Weapons. One of the major goals of ONR's ASWT program is to develop, by 2015, a family of responsive air-and ship-launched weapons that have fly-out ranges that are 200 percent greater than the ranges of 1995 baseline weapons, and average velocities of Mach 8. These goals are based on a scenario that assumes that a naval task force will be constrained, by the need for self-protection, to operate 100 nautical miles from the shore. (The committee notes in passing that this scenario is at variance with the ERGM scenario, which assumes that naval fire support platforms will operate 25 miles from the coastline.) In this scenario, the naval task force must provide fire support to locations 200 miles inland. The weapon range must therefore equal 300 nautical miles. The second assumption of this scenario is that fire support must be delivered to the target within two and one-half minutes after the initial call for fire. The scenario appears to assume that the command-and-control process has zero latency; that is, a call for precision strike fire support is presumed to be responded to instantaneously. This implies a mean speed of 7,200 knots, which equates to Mach 11.4. If the TOF delay can be extended to 3.75 minutes, the required mean speed would drop to an equivalent of Mach 8 (at 115,000 ft if the dynamic pressure is held constant at 500 pounds per square foot). The missile system described to the committee was powered by an integral boost dual combustion mode ramjet. After booster burnout, fuel is injected at an aft set of injectors and the propulsion unit acts as a classical subsonic burning ramjet. At some high Mach number, say 6, fuel is also injected at a forward set of injectors, and the fuel flow rates in the two injectors are controlled so that the propulsion system acts as a supersonic combustion ramjet, a so-called SCRAMjet. While subsonic combustion ramjets are fairly well understood, and have powered deployed supersonic weapons systems, this is not the case for the SCRAMjet or the dual combustion mode ramjets. The committee found no information in the open literature suggesting that subsonic combustion ramjet operation has successfully transitioned to a SCRAMjet. The committee suggests that additional experimentation and research be done prior to committing a new weapons system development to the dual combustion mode ramjet. The proposed dual combustion mode ramjet would use standard hydrocarbon fuels. This has the potential to present launch-on-command problems, which can be overcome by use of a solid propellant and a configuration called an integral rocket ramjet. The hydrogen-rich rocket exhaust is burned in the duct downstream of an air inlet. Such systems have been successfully flown at hypersonic speed by the U.S. Air Force and have been used by the Russians in the SA-6 missile. The committee suggests that this configuration should be examined as a candidate near-term, quick-reaction weapon. Alternatively, it may be useful to look at the use of a ballistic rocket exo-trajectory for application to this weapon system. Conclusions The committee's conclusions for the precision strike mission area of the ONR ASWT program are the following: To meet top-level requirements (performance goals), an effort is needed to define future strike weapons systems concepts. Such a definition should include all components (including limitations on system latency) of a responsive and precise sensor-to-target-kill chain that can engage ephemeral

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program targets. Dependence on GPS robustness, and the possibilities of alternatives to GPS, should be explicated in the concept definition. Also needed are an evaluation and survey of technology enablers for each major weapon system concept ONR is supporting. As an example, what role do weapons data links and seekers play in the total system, in achieving cost-effective, precision capability? Recommendations Precision Strike. Conduct a study (drawing on the expertise of all relevant ONR codes) to define all components and their key characteristics (including latencies) of a responsive and precise robust sensor-to-target-kill (and damage assessment) chain that can engage ephemeral targets. Based on such studies, the cost-effectiveness of key technology enablers could be evaluated and a small number of investments made to bring 6.2 concepts rapidly to advanced concept technology demonstrations (ACTDs). NAVAL FIRE SUPPORT Overview Both the naval fire support and the precision strike mission areas face a common set of problems related to the targeting of fixed, relocatable, moving, and ephemeral targets; automatic target recognition; response time for delivery of weapons on target; warhead lethality; weapon range; and weapon guidance. Modern concepts of naval fire support are based on the evolution of the ERGM, which is a 5-inch-diameter, GPS-guided missile that is gun-rather than rocket-launched. Current ERGM designs have a range of about 63 nautical miles. If current efforts in the naval fire support mission area are successful, ranges of about 100 to 200 nautical miles may be achieved within the next 15 years. ONR's ASWT program in the area of naval fire support is focused on the following themes: Weapon responsiveness, Rapid and accurate targeting, Improved lethality, and Cost-effective sustainability. The range of the ERGM weapon and its successors allows attacks on targets that are beyond the line of sight. Thus the naval fire support problem of guiding a weapon to a target is identical to the problem in precision strike. Comments on Program Components The committee found much of the work in support of ERGM-like weapon systems to be technically superb. However, the committee was concerned about what the work on the 5-inch round will contribute to improved weapons capability. The technology of the gun-launched missile appears to be well up on the knee of the curve—the technology is exquisite, but what will happen if the range to target grows by a factor of, say, two? If marines are engaged in combat in Kosovo, the range of the ERGM round or any of the derivatives presented at the review will be inadequate. The committee believes that it is in part ONR's mission to be thinking about how this problem will be resolved with future weapons systems.

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program The naval fire support effort heavily favors the technology that supports improving naval gun performance capabilities through increasing the range and reducing the CEP when firing on coordinates. The committee regarded the NSWC Dahlgren 6.3 program component as particularly good in this respect. However, the committee thought that the scope of the naval fire support effort was too narrow and offered up only “stovepipe” solutions. The program components did not address important current and emerging weapon system needs. Underlying most of the naval fire support R&D was the assumption that Navy ships would be stationed some 25 nautical miles offshore and would be called upon to fire on designated (GPS) target coordinates that would somehow be available (probably from a forward observer). The objective is to deliver (small) warheads with small CEPs rapidly at a high rate of fire. The effort shows little evidence that the entire integrated sequence of detection, classification, target designation, communication of targeting information from the several surveillance sensor systems, and weapon response has been considered as an overall system. As weapon range requirements from offshore platforms increase, the limitation of gun launch forces a reduction in warhead size that essentially no practical amount of reduction in CEPs can offset. Requirements for increasing weapon range render the gun as the first stage of what would otherwise be a rocket solution. All-rocket weapons might be more effective for the long-range delivery of larger warheads to more distant targets at a higher rate of fire. In this respect the concentric canister launcher has merit. The naval fire support mission area needs more emphasis on missile solutions. The naval fire support mission area is also deficient in providing program components that address moving targets. Although the naval forces have a credible capability to attack stationary targets with a variety of weapons (mostly air-launched), they have no standoff, unmanned weapons to attack moving targets illuminated by MTI radar. The ONR ASWT program devotes only a limited effort to tasks that are directly responsive to a concept of operations that would allow a moving target to be attacked by weapons launched from ranges beyond the line of sight of the launch platform. Also, there is insufficient emphasis on a capability for attacking targets other than those for which the coordinates are given. In land warfare supported with naval fire, a soldier or marine close enough to the target to provide its coordinates may also be close enough to use a (laser) target designator. In addition, the target may have specific sensor-significant attributes (heat, radar return). Thus, a portion of the naval fire support mission area should address weapons that can perform either autonomously or with human-aided terminal guidance. Such a capability would also go a long way toward addressing moving targets or targets that have relocated during the time elapsed from target designation (by land forces) to weapon arrival time. The committee thought that the weapon guidance program components were valuable. Although several of the low-cost guidance systems are being developed for gun munitions, they are equally applicable to surface-to-surface missiles. In fact, the attempt to reduce costs for guidance systems so that they are affordable for gun munitions might lead to missile guidance systems with lower costs than those achievable by a missile guidance cost-reduction program. Conclusions The committee's conclusions for the naval fire support mission area of the ONR ASWT program are the following: The R&D portion needs to be better balanced by increasing the level of effort devoted to surface-launched missile solutions to naval fire support;

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program Naval fire support weapon system concepts are needed to enable the engagement of targets at ranges that exceed any extrapolation of ERGM ranges; Weapon sensors and terminal guidance systems are needed to provide for autonomous attack of sensor-significant targets or to respond to cooperative targeting with human-aided target designation; An increase in the level of effort on systems designed to attack moving targets is needed; and An overall increase in systems engineering is needed to ensure that emerging sensors, third-party (non-organic) targeting, and sensor-to-weapon communications are integrated into proposed R&D solutions. Recommendations Naval Fire Support. Rebalance the program components by increasing efforts on technology for surface-launched missiles for fire support at ranges beyond those expected for ERGMs. Increase the level of effort toward systems to attack moving targets. Provide sensors and final-stage guidance for autonomous or human-aided missile attack. Pursue technology for integration of emerging sensors and sensor-weapons communications. SHIP-BASED DEFENSE Overview In the mission area of ship-based defense, the generic problem is to increase the ability of existing ship self-defense systems to maintain (and improve) current levels of performance in the face of threat missiles with decreased radar cross sections, reduced altitude trajectories, and higher agility. A conscious decision has been made to limit the ONR effort in this area to the examination of a few novel concepts for terminal and intermediate-range defense systems. These program components are of interest in that they deal with an important niche market in the field of ship self-defense. However, they do not address the most significant problems, such as countering low-observable, low-trajectory, or maneuvering missiles except in intermediate and terminal engagement phases. In recent times, ship self-defense has come to mean defense against air-and surface-launched weapons. Ships are of course subject to attack by torpedoes. The committee notes in passing that no ONR-sponsored work related to torpedo defense was described during the review. Although this omission was undoubtedly an artifact of ONR's organizational structure (i.e., torpedo defense is not a responsibility of ONR's Naval Expeditionary Warfare Science and Technology Department, of which the ASWT program is a part), it is the committee's belief that commenting on the overall value of the effort in ONR's ship-based defense mission area would be inappropriate since a significant portion of the problem is not addressed in a coherent program component. The defense of a ship in the littoral areas of the world is a difficult task because of the variety and number of threats possible. The overall ONR effort in this regime encompasses an eclectic mix of technologies that reflect the diversity of these threats, which range from sea-skimming and ballistic missiles and land-based artillery to massive attacks by suicidal fanatics in small boats and water jet craft, and so on. Coupling these with the possibility of intense, high-power jamming gives an appreciation of the magnitude and danger of the potential threat.

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program Comments on Program Components. In ONR's ship-based defense mission area, the program components span two of the three main areas of ship defense, which are terminal defense (range less than 1 kilometer), intermediate defense (range out to 5 nautical miles), and extended-range self-defense (range greater than 5 nautical miles). The requirements for defense with respect to reaction times, warhead lethality, and so on vary depending on where the defensive action takes place. Program components have been structured to reflect these conditions based on input from a 1998 workshop that included resource sponsors and program executive offices (PEOs).3 The outcome of the workshop was that future technology efforts should focus about 50 percent on near-term technologies that can be used by engineering and manufacturing development programs and 50 percent on long-term S&T initiatives that can be applied to future naval requirements. The briefings presented to the committee included recently completed as well as ongoing tasks. Among the former were work on terminal-defense technologies like the Firebox composite gun, the semiactive radio frequency (RF) millimeter-wave projectile guidance system, and the water-barrier terminal-defense system. All three of these systems could provide developed technologies that might be applied now and in the future. The Firebox composite gun consists of multiple barrels (9 to 16), each of which can fire a 60-mm semiactive, hit-to-kill guided projectile at a launch energy of 4 to 5 megajoules. Thus it has a launch energy one-half that of the MK 45 5-inch/54 with one-tenth the weight of the 5-inch barrel and with multiple barrels can outperform the 5-inch gun for close-in defense. The projectiles were guided by a W-band radar. The water-barrier system, recently completed, is a last-ditch option in a layered defense concept. Tests and models indicate the viability of the concept in favourable geometries. Ongoing tasks in this mission area include technologies in sensors, particularly low-cost wideband seekers; warheads; and novel propulsion methods. These technologies should find application in gun-launched projectiles as well as missiles. Numerous studies4 have shown the effectiveness of guided rounds for close-in defense against sea-skimming missiles. In all cases detection in the presence of low-angle background clutter characteristic of littoral sea areas is a critical factor. This is also true for detection of high-speed surface craft. While the ship defense program component includes efforts to characterize low-angle propagation and clutter for radar and IR in littoral environments, the criticality of the problem indicates the need for a major effort in this area. Reactive-material warheads represent a promising technology because of the enhanced energy deposition that results on impact, including the kinetic energy of the fragments, the chemical explosive energy of the reactive elements, and the potential for release of energy due to the combustion of gases and materials. This translates into a two-to four-fold increase in destructive energy compared to the kinetic energy alone. Of several different reactive materials, only a limited number can survive an explosive launch. In fact, only aluminum polytetrafluoroethylene was found to not react when explosively launched, but to react when it struck a target. This technology program component is aimed at developing a notional warhead that incorporates reactive materials. Its effectiveness will be demonstrated in static arena tests. 3    ONR-35 Ship Defense Workshop, May 19, 1998. Attendees included RADM Baslile, USN, from NAVSEA, and representatives from N865, N86T, N911, OUSD/DDR&E, ONI, PEO TSC, NSWC, NAWC, and ONR 31 and 35. 4    Dawson, V.C.D., J.D. Love, C.A. Carney, G. Schecter (Battelle), C. Sharn (SDIO), D.S. Malyevac (NSWC), J. Connelly (SAIC), and G.J. Ferrebee (NSWC). 1990. The Naval Gun Study, Vol. 1: Summary, Center for Naval Analyses, Alexandria, Va., October, 1991. Dawson, et al. Vol. II: Support Analyses, August, 1992.

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program The rolling airframe missile (RAM) accelerator gun is a novel approach to achieving very high velocities (Mach 6+) in a terminal-defense system, thereby decreasing TOF and increasing keep-out range. There are engineering problems associated with a system of this type, particularly when a high rate of fire is desired. It also involves a special projectile shape, which may be costly. ONR has done an excellent job of restructuring its ship-based defense program components using the input from Navy resource sponsors and PEOs referred to above. In addition it has mandated progress reports and milestones with clearly defined completion dates. The program components in this ONR mission area involve many diverse technology areas but seem to be well balanced with clearly defined goals and objectives. The committee recognizes that the development of new technologies frequently requires many years of effort and funding. During such times the requirements often change because of new PEOs or sponsors, whose priorities differ from those represented by a particular technology. Thus, technologies like Firebox and the water-barrier terminal-defense system are currently on the shelf because of the Navy's emphasis on missile solutions to ship defense involving the evolved sea sparrow missile and the RAM, which are more attuned to the blue water threat. As emphasis on littoral warfare increases there will be an increased need for a time-critical layered defense at least three engagement levels deep. The technologies mentioned could provide a cost-effective solution. The committee notes in passing that the anti-ship cruise missile problem is still not solved. Although the combined effectiveness of U.S. long-range defenses, intermediate-range defenses, and terminal defenses presents a high cumulative probability of ship survival, the success rate is still less than perfect. The committee also recognizes that the Navy has evinced little interest in making major new investments in terminal-defense system and that the ship-based defense mission area is undergoing an orderly redirection. The committee hopes that the sensor work described in this review will survive program component reorientation and be applied to other defense applications as appropriate. Conclusions The committee's conclusions for the ship-based defense mission area of ONR's ASWT program are as follows: An effort is needed to develop a layered defense for countering low-observable, low-trajectory, and maneuvering missiles. Such a defense should not be limited to the terminal engagement phase of ship self-defense. A major effort is needed to detect low-flying missiles and high-speed surface craft in the presence of littoral clutter. Continuing support is needed for the sensor work described in this review so that it will survive program component reorientation and be applied to other defense applications as appropriate. Recommendations Since many of the tasks reviewed in the ship-based defense mission area have been completed, and since the program components are undergoing a substantial redirection, the committee did not believe that major recommendations were appropriate in this area. Ship-based Defense. Increase effort toward a layered defense against low-observable, low-altitude, maneuvering missiles in the presence of littoral clutter. Continue existing sensor-related efforts.

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program ASWT SUPPORTING SCIENCE AND TECHNOLOGY (6.1 AND 6.2) PROGRAM AREAS Introduction The ONR ASWT program includes a supporting 6.1 and 6.2 effort described as being devoted to air platform and weapons technology needs not addressed by other ONR departments. The ASWT 6.1 program area has three main research components: Shock-induced fluorine chemistry, Unsteady aerodynamics and active flow control, and Intelligent autonomous air vehicles. The 6.2 supporting technology program area is concerned only with Unsteady aerodynamics, and Unmanned combat air vehicles. The total funding devoted to these program components is about $6 million per year. Given the complexity of the subjects addressed, ONR, of necessity, must develop a focused effort if it is to have any significant impact. Comments on ASWT 6.1 and 6.2 Program Components Shock-induced Fluorine Chemistry (6.1) The committee was presented with only a minimal description of the shock-induced fluorine chemistry program component. The work is being done in support of the reactive material advanced technology demonstration (ATD) program and is being performed at the Naval Research Laboratory, Naval Air Warfare Center, Naval Surface Warfare Center, and Los Alamos National Laboratory. All evidence indicates that this program component is productive. Unsteady Aerodynamics (6.1 and 6.2) The unsteady aerodynamics program components grew out of a practical problem that arose during F-18E/F flight testing. When the F-18E/F is flying at a certain lift coefficient, whether in a turn or in level flight, one wing or the other tends to drop in an unpredictable, capricious fashion.5 If the underlying phenomenon is truly aperiodic, the Navier-Stokes code may require a large number of repeat runs to provide enough data to characterize the statistics. If this is the case, the investigators may have 5    The lift coefficient at which this event takes place, if it takes place at all, corresponds to a point where there is a slight reduction in the slope of the lift coefficient curve as a function of the angle of attack. For many airfoils, a gentle reduction in the slope of the lift coefficient curve as a function of the angle of attack is related to the aerodynamic interference between the flow near the airfoil's trailing edge and its wake. In the case of the F-18E/F, the aircraft motion seems at times to be preceded by or accompanied by a slight buffet.

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1999 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program difficulty in deciding when the solution has converged and when the fluctuations are in fact related to the phenomenon in question and are not just a by-product of the modeling. To complicate matters, other aerodynamic interference may play a role in the onset of this phenomenon. Although an explanation of the details of this phenomenon may be difficult to unravel, the committee believes that this is a potentially valuable research effort. On the other hand, it was not clear to the committee that the work presented that was related to active control of low-Reynolds-number flows has much future application to problems generic to naval forces. Intelligent Autonomous Air Vehicles (6.1) and Uninhabited Combat Air Vehicles (6.2) The 6.1 research work on intelligent autonomous air vehicle systems appears to be directed toward fundamental aspects of a networked command-and-control system for UCAVs, which is being further explored and demonstrated in various aspects in the ASWT UCAV 6.2 program component. Regarding UCAVs, the committee notes that there are several other important issues besides data links and control—e.g., sensors, payload, endurance on station, and aerodynamics (recovery and airborne agility)—and that there are major programs in the UCAV area funded by DARPA and the U.S. Air Force. Considering the interest in and work on UCAVs in industry, and developments supported by the major U.S. Air Force and DARPA programs, ONR's 6.1 and 6.2 work in intelligent vehicles and UCAVs should focus on areas not included in the efforts of these other organizations or services. While the ASWT 6.1 intelligent autonomous air vehicles research program component addresses several appropriate areas, the effort overall does not seem to be at the forefront of science. The 6.1 work on intelligent autonomous air vehicle systems appears to duplicate past achievements (e.g., sequential estimation, Bayesian belief networks, optimal sensor selection, and nonlinear inverse dynamic control with exogenous disturbances). The committee is concerned with how “basic” this research really is. While the cadre of principal investigators is impressive, they do not appear to be working toward cohesive goals for the ASWT program. The ASWT 6.1 and 6.2 supporting S&T should contain elements dedicated to other weapons areas requiring support at the fundamental level, such as described in several places above, e.g., GPS alternatives, guidance and control missile aerodynamics, and sensor backgrounds in the littoral. Conclusions The committee concludes that restructuring of the ASWT 6.1 and 6.2 supporting S&T program is needed. The number of projects in the intelligent air vehicles and UCAV areas is excessive. The scientific merit of some parts of the 6.1 intelligent air vehicles program is questionable. The 6.1 and 6.2 supporting S&T program should be restructured to assist other weapons areas needing fundamental support. Recommendations ASWT Supporting Science and Technology (S&T) (6.1 and 6.2) Program Areas. Reduce the number of intelligent air vehicles and UCAV projects, and then redirect 6.1 and 6.2 program components toward closer coupling to other important needs of ONR's ASWT program. Surviving 6.1 candidate program components also should be scrutinized carefully for scientific merit.

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