4
Technology Issues

OVERVIEW

The key goal for conventional prompt global strike (CPGS) systems, the ability to hit distant targets quickly and accurately, delivering damage only to the well-defined target area, entails serious technical challenges. A wide range of concepts has been proposed to meet the CPGS challenge, as illustrated in Figure 4-1. These solutions include modest modifications to existing ballistic missiles (such as the Conventional Trident Modification [CTM]), boost-glide missiles, and hypersonic cruise missiles. The weapons themselves can be launched from the continental United States (CONUS) or from forward-deployed land bases, submarines, or aircraft.

The principal proposals for CPGS build on technology designed for the rapid, long-range ballistic delivery of nuclear weapons. Since a conventionally armed prompt global strike system must be much more precise in its targeting accuracy and weapon delivery than a nuclear delivery system, no existing system can be used without modification. CPGS systems are being considered with varying degrees of modification from a ballistic trajectory, as illustrated in Figure 4-2. The simplest modification requires developing sufficient control, navigation, and guidance during reentry to enable the required terminal accuracy, as in the left-most options shown in Figure 4-2. For some options a gliding reentry vehicle (RV) is used to increase range, trajectory flexibility, and maneuverability, as illustrated in the two right-most options shown in Figure 4-2. In addition to the terminal accuracy challenge, these approaches also must solve the serious issues of managing the heat generated when traveling at high speed within the atmosphere.

A wide variety of CPGS payloads has also been proposed for use, as illus-



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4 Technology Issues OVERVIEW The key goal for conventional prompt global strike (CPGS) systems, the ability to hit distant targets quickly and accurately, delivering damage only to the well-defined target area, entails serious technical challenges. A wide range of concepts has been proposed to meet the CPGS challenge, as illustrated in Figure 4-1. These solutions include modest modifications to existing ballistic missiles (such as the Conventional Trident Modification [CTM]), boost-glide missiles, and hypersonic cruise missiles. The weapons themselves can be launched from the continental United States (CONUS) or from forward-deployed land bases, submarines, or aircraft. The principal proposals for CPGS build on technology designed for the rapid, long-range ballistic delivery of nuclear weapons. Since a conventionally armed prompt global strike system must be much more precise in its targeting accuracy and weapon delivery than a nuclear delivery system, no existing system can be used without modification. CPGS systems are being considered with varying degrees of modification from a ballistic trajectory, as illustrated in Figure 4-2. The simplest modification requires developing sufficient control, navigation, and guid- ance during reentry to enable the required terminal accuracy, as in the left-most options shown in Figure 4-2. For some options a gliding reentry vehicle (RV) is used to increase range, trajectory flexibility, and maneuverability, as illustrated in the two right-most options shown in Figure 4-2. In addition to the terminal accu- racy challenge, these approaches also must solve the serious issues of managing the heat generated when traveling at high speed within the atmosphere. A wide variety of CPGS payloads has also been proposed for use, as illus- 87

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88 FIGURE 4-1 Candidate concepts for conventional prompt global strike include ballistic missiles, boost-glide vehicles, and hypersonic cruise missiles. The range of these concepts varies from 1,000 to 3,000 nmi for forward-deployed systems to more than 10,000 nmi for land-based sys- tems. Options are being investigated to attack a range of targets from soft to hard to mobile. NOTE: Acronyms are defined in Appendix A. Figure 4.1, bitmapped, uneditable, color top is portrait size bottom is landscape size if caption is only 1 line

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CTM CSM-2 SLGSM CSM-1 Built on Mk 500 RV • Built on E2 and Built on AMaRV Technology being • • • experience LETB experience experience developed in 300-s TPS • FALCON program Small warhead 800-s TPS • • Large warhead • 3,000-s TPS • Error correction Large warhead • • Moderate trajectory • Large payload with • Limited footprint Footprint expansion • • flexibility dispense capability expansion with RV having Error correction • moderate lift-to-drag Significant footprint • Trajectory flexibility • ratio expansion with RV and footprint having high lift-to- expansion with RV drag ratio having moderate lift-to-drag ratio FIGURE 4-2 Illustration of the reentry vehicles (RVs) proposed for different stages of conventional prompt global strike (CPGS) systems. A previously developed modification to ballistic reentry, E2, is the basis for the proposed short-term Conventional Trident Modification (CTM) op- tion. For the Submarine-Launched Global Strike Missile (SLGSM), a scaled-up version of the previously developed Mk 500 is the proposed RV, which is designed to have a glide range less than 1,000 nmi. The Conventional Strike Missile (CSM)-1 concept builds on theAMaRV vehicle and is considered to have an 800-second glide segment to its trajectory. The CSM-2 concept builds on a high lift-to-drag (L/D) vehicle, which is be- ing developed by the Defense Advanced Research Projects Agency FALCON program, that has a 3,000-second thermal protection system (TPS). NOTE: AMaRV, advanced maneuvering reentry vehicle; E2, Enhanced Effectiveness (one of two test beds for demonstrating proof-of-principle concepts for ballistic missile delivery in CPGS and discussed in Chapter 4 in the subsection entitled “Guidance, Navigation, and Control Ac- curacy Issues”); LETB, Life Extension Test Bed (the second of two test beds for demonstrating proof-of-principle concepts for ballistic missile delivery in CPGS and discussed in Chapter 4 in the subsection entitled on “Guidance, Navigation, and Control Accuracy Issues”). 8

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0 U.S. CONVENTIONAL PROMPT GLOBAL STRIKE trated in Figure 4-3. In the terminal phase of flight, the RV or cruise missile may attack the target with a unitary warhead (which may be designed for penetration), or a warhead that disperses kinetic energy projectiles (KEPs). The reentry vehicle may fly a nominally ballistic flight path with entry angles of less than 30°, or the reentry vehicle may maneuver aerodynamically for vertical attack of the target. Alternatively, the delivery platform may slow sufficiently to deploy existing munitions, sensors, communication relays, or unmanned aerial vehicles (UAVs). The dispensing sequence may occur at low speed following deceleration of a low-β reentry or may be required to occur at supersonic or hypersonic speeds for survivability reasons. The following sections review the CPGS options and technology challenges, including the system requirements, system concepts, research and development (R&D) issues, and technology readiness time lines. REQuIREMENTS In its most general definition, the mission of a CPGS system is to provide the capability to attack and defeat with conventional weapons a time-sensitive target anywhere in the world. In considering a CPGS capability, one must address the complete end-to-end system-of-systems capability to identify potential targets, determine their geolocation, define attack options, estimate collateral damage, communicate effectively with a decision maker who chooses to go forward with the strike, deconflict flight through air and space domains, engage the target, and assess the impact of the attack. The time required to complete the entire target prosecution time line must lie within the target’s period of vulnerability. A version of the attack time line is shown in Figure 4-4 as consisting of the following phases: Find, Fix, Track, Target, Engage, and Assess (F2T2EA). As illustrated in Figure 4-4, the development of a robust and flexible CPGS capability requires shorten- ing all aspects of the target prosecution time line. With respect to the engagement portion of the F2T2EA process, CPGS options that have the potential to engage a target within 1 hour are being explored. Compression of the time line to the extent required will necessitate seamless integration of disparate systems; development of detailed tactics, techniques, and procedures (TTPs); and personnel training. It appears likely that time lines consistent with the CPGS mission can be achieved, but additional development work will be required. For the near to mid-term, some of the steps will need to have been accomplished in advance of when the 1-hour clock begins. In the mid- to-long term, improved procedures and technology may make it possible that the entire process could be accomplished within the hour under some conditions. In fact, in examining several scenarios and looking at historical cases analogous to what is envisioned (see Chapter 2), the committee found that many of the missions postulated for this capability can largely be preplanned on a contingency basis, reducing the stress on these enabling activities. What cannot be preplanned is the

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FIGURE 4-3 The need to attack different types of targets drives a requirement for different terminal-phase maneuvering and warhead charac- teristics. Terminal-phase options for conventional prompt global strike include minimal error corrections to the ballistic trajectory to achieve terminal accuracy, aerodynamic maneuvering for vertical impact to allow attack of buried structures, long-range glide for range extension and Figure 4.3, bitmapped, uneditable, color potential dispensing of munitions, and low-β reentry with deployment of an unmanned aerial vehicle (UAV) for attack of a moving target. top is portrait size NOTE: Acronyms are defined in Appendix A. 1 bottom is landscape size if caption is only 1 line

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2 U.S. CONVENTIONAL PROMPT GLOBAL STRIKE Days Find Fix Track Target Engage Assess Today Decide Hours F2T2 EA CPGS Decide FIGURE 4-4 Conventional prompt global strike (CPGS) will require compression of the time line across the entire Find, Fix, Track, Target, Engage, and Assess (F2T2EA) strike process. With strategic warning and preparation, Days key aspects of this process can be ac- complished in advance. For those portions of the process that need to occur inside the compressed time, technical means for seamlessly integrating systems that are currently Find Fix Track Target not interoperable will need to be developed. Engage Assess Today decision and validation time when the contingency actually occurs. The speed of execution time required in CPGS decision and validation, including the time for Decide earlier steps in those limited cases when preplanning has not occurred, exacerbates an already difficult command, control, communications, computers, intelligence, surveillance, and reconnaissance (C4ISR) situation for the U.S. military, as dis- cussed in a recent report of the National Research Council.1 The “global” requirement for a CPGS system places significant requirements on potential engagement systems, one that the committee concluded should not be taken literally.2 The “prompt” requirement for a CPGS system also significantly Hours 1 National Research Council. 2006. CISR for Future Naval Strike Groups. The National Academies Press, Washington, D.C. 2 If “global coverage” were free, it would not be an issue, but the committee found, from its own analysis, that modest restrictions of coverage (e.g., not worrying about a sudden need to fire on Antarctica) would in some cases allow material improvements in payload and more flexibility in A F2T2 E CPGS system choice. Decide

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3 TECHNOLOGY ISSUES impacts the design characteristics of potential engagement systems. In assessing the requirements for CPGS, it is important that the terms “global” and “prompt” be viewed in the context of the realistic time lines associated with gathering and evaluating credible intelligence, surveillance, and reconnaissance (ISR) data, planning of force packages for a precision strike, and the decision process autho- rizing the strike. The range of scenarios considered in this report is intended to illuminate the full spectrum of mission options. The concept of a prompt global strike capability initially evokes ideas involv- ing strategic ballistic missiles—either land- or sea-based—that can deliver pay- loads over enemy defenses to targets 6,000 or more nautical miles away within 30 to 40 minutes of their launch. If one defines the term “global strike” to mean the ability to strike anywhere in the world without depending on basing or overflight rights, but perhaps with foresight in positioning launch platforms, one is led to look at approaches other than intercontinental ballistic delivery. In this approach, “prompt” might be measured from the time of decision or target-cue to the time of weapon effect. That is, preparations and decisions would have been made in advance. A number of technical system options are potentially available for CPGS. Specifically, platforms (e.g., submarines, land-based aircraft, carrier-based air- craft) can be moved forward to an area of interest and can loiter (in some cases covertly) with long persistence—for many days at a time—while the planning and approvals for the force package are proceeding in parallel. These platforms can carry fast-flying shorter-range stand-off weapons that have flight times of 30 minutes or less to arrival on target. Armed remotely piloted vehicles have been employed on several occasions and represent one end of the spectrum of this concept, as does a cruise missile with loiter capability, but both have far less loi- ter endurance than needed and are likely to be detected while they loiter. A naval battle group (with aircraft, cruise missiles, or both) can sometimes run undetected in an area for days or weeks, but it might be observed at any time. In contrast, a nuclear-powered attack submarine (SSN) or a nuclear-powered ballistic missile submarine (SSBN) deployed in a region of interest with medium-range ballistic missiles would meet the criteria of covertness and persistence without significant limitations, if necessary technical capabilities are developed and weapon effec- tiveness is demonstrated. Two other important desirable characteristics are embodied in the CPGS con- cept. One is the need to have a high probability of penetrating defenses and reach- ing the target, and the other is the ability to do this without risking U.S. personnel. These concerns are highest in the leading edge of an attack against a formidable adversary when the adversary’s air defenses have not been suppressed. These considerations favor longer-range ballistic missiles or boost-glide missiles or hypersonic cruise missiles that could be launched from submarines, long-range aircraft, or land bases. Some systems that would launch from CONUS, however, might be constrained by concerns about overflight (e.g., a missile over-

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 U.S. CONVENTIONAL PROMPT GLOBAL STRIKE flying Europe, Russia, or China) and about debris from booster stages (which might, for example, fall into Canada). Whatever scheme is proposed, there are ambiguity issues, potential compromise of other mission capabilities, and inter- national policy and arms stability questions to be considered (see Chapter 3). In discussing the range requirement for a CPGS system, it is helpful to look at the geography of the world overlaid with range contours and azimuths to and from various locations. The (nonrotating Earth) ranges3 from the coasts of the United States (where CONUS-based systems may be based) to various parts of the world are shown in Figure 4-5. One can see that a CONUS-based CPGS system must have a range of 6,500 to 7,000 nmi to reach most parts of the world if bal- listic trajectories are flown. If overflight considerations constrain operations, the required range may be as much as 16,000 nmi, since the system may be required to fly the long way around. Figure 4-6 shows ranges from a potential operating region in the Arabian Sea. One can see that a CPGS system operating from this area requires a range of approximately 2,500 to 3,500 nmi to reach most of the troubled regions of the area. With range requirements defined, the speed requirements for candidate con- cepts are shown in Figure 4-7, where the capabilities of existing conventional forces, hypersonic cruise missiles, and ballistic missiles are overlaid on lines of average Mach number (defined as the range divided by the time-to-target and stratospheric sound speed, assumed to be 968 ft/sec).4 The existing capability for conventional force projection is limited to subsonic speeds. With a 1-hour engage- ment window, this limits the range to approximately 460 nmi. The range-time trade-off for ballistic missiles is also shown in Figure 4-7. In this case, the time-to-target was calculated assuming maximum-range ballis- tic flight for each range. Ballistic missiles can engage targets within the 1-hour engagement window for both forward-deployed and CONUS-based systems. From forward-deployed platforms, ballistic missiles can engage targets in approx- imately 25 minutes, whereas CONUS-based ballistic missiles require a flight time of approximately 40 minutes. Finally, the capabilities of hypersonic cruise missiles are shown correspond- ing to flight at speeds of between Mach 4 and Mach 8. (In this report, the term “hypersonic cruise missiles” will be used to refer to missiles that cruise at speeds at or above Mach 4.) Even hypersonic air-breathing cruise missiles are not capable of deployment from CONUS in the 1-hour engagement window, but they can be deployed from forward-deployed forces with flight times between 30 and 60 minutes. 3 Unless specifically expressed otherwise, the range contours in this report are presented as nonro- tating Earth ranges. 4 Mach 1 defined in this context as the speed of sound in the stratosphere = 968 ft/sec (or equivalently 0.159 nmi/sec, or, 1,062 km/hr).

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8000 5000 6000 7000 5000 6000 7000 8000 5000 6000 7000 FIGURE 4-5 Sample great circle ranges (nmi) from (left) Kennedy Space Center, Florida, and (right) Vandenberg Air Force Base, California, illustrating the need for 6,500 to 7,000 nmi to reach most parts of the world for a continental United States–based system. Overflight restric- tions can result in significantly longer-range requirements, since the vehicle may be required to travel the long way around the globe. Figure 4.5, editable, color top is portrait size 5 bottom is landscape size

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6 U.S. CONVENTIONAL PROMPT GLOBAL STRIKE 3000 2000 FIGURE 4-6 Sample ranges (in nautical miles) from a notional nuclear-powered guided missile submarine (SSGN) launch location in the Arabian Sea illustrating the need for a conventional prompt global strike range capability of 2,500 to 3,500 nmi when launched from an SSGN. Target Figure 4.6, editable, color Types and Information Required The targets sets that are most relevant to CPGS can be divided into three general categories: (1) fixed soft targets (both point and area targets), (2) fixed hard targets (both hardened point targets and deeply buried complexes), and (3) mobile targets or targets with uncertain location. Only the subset of targets within these general categories that are considered to be time-sensitive will be candidates for attack with a CPGS system. Fixed Soft Targets A fixed soft target is one whose geolocation is known with accuracy accept- able for attack, whose location remains constant during the engagement window,

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FIGURE 4-7 Flight time versus range for existing subsonic systems, proposed hypersonic cruise missiles, and ballistic missiles. Overlaid are lines of average Mach number, defined as the ratio of block speed (range divided by flight time) to the sound speed at 390 degrees Rankin. For continental United States (CONUS)-based systems, only ballistic missiles are capable of meeting a 1-hour time line. For forward-deployed systems, hypersonic cruise missiles are candidates. 7 Figure 4.7, bitmapped, uneditable, color top is portrait size bottom is landscape size if caption is only 1 line

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127 TECHNOLOGY ISSUES applications discussed here, including battle damage assessment. With sufficient priority (and a presidential-release weapon should have it), satellite channels can be made available reliably. The Tactical Tomahawk has such a link. The potential for establishing such capabilities for CPGS may be influenced by the plasma sheath that can form during reentry, interfering with radio-frequency communica- tions channels (see the subsection “GPS/INS Navigation” above). The formation of a plasma sheath is highly dependent on the specific characteristics of the reen- try vehicle. Vehicle speeds above Mach 10 may result in a plasma sheath, while speeds about Mach 20 virtually guarantee it. Altitude is also a factor, with plasma effects occurring between approximately 30,000 feet and 300,000 feet. The shape of the reentry body is important, with blunt bodies causing higher-density plasma. Finally, ablative materials and materials high in plasma-inducing contaminants are likely to increase plasma density. Thus, careful design and testing to evaluate the impact of plasma formation around the reentry vehicle will be important for in-flight communication, as well as for GPS reception, as discussed above. Weapons Effectiveness One of the warheads proposed for employment in some proposed CPGS systems is a cluster of segmented tungsten rods that are explosively deployed through the heat shield of the RV at a time determined by a fuze. The result is a selectable pattern of the rod segments or KEPs that are dispersed over the desired target area, impacting at a velocity of more than 5,000 ft/sec. If the fuze is set not to fire, the resulting densely packed cluster of rods serves as a 250 lb unitary slug (penetrator) which, along with a RV structure, impacts with kinetic energy sufficient potentially to penetrate a multistory building or to create a crater several meters across and deep. The issues of the effectiveness of such kinetic energy weapons against various types of targets are discussed below. Fixed Soft Targets Most fixed soft targets are susceptible to attack by unitary blast-fragmenta- tion or kinetic energy warheads. As previously noted, the initial CTM would carry up to four reentry vehicles equipped with advanced navigation, guidance, and control capabilities. Each reentry vehicle would carry a warhead consisting of dispersible KEPs. Using approximately 1,000 small tungsten rods deployed by explosive charge, a relatively uniform pattern of small KEPs is created. The kinetic energy of a single rod is approximately the same as that of a 50-caliber bullet. The dispersion radius of the pattern can be varied by varying the height at which the warhead is triggered, with constraints imposed by atmospheric drag on the dispensed rods. If a completely uniform pattern could be achieved and a single rod placed in each square meter on the ground, the dispersion pattern would have a diameter

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128 U.S. CONVENTIONAL PROMPT GLOBAL STRIKE of 35.7 meters. If the target is such that a denser pattern is required with, say, 16 rods per square meter, a 1,000-rod warhead would be capable of producing a dispersion diameter of 8.9 meters. In both cases, the dispersion diameter is greater than the expected miss distance, so the KEP warhead is anticipated to be effective against soft targets. If the target location error was somewhat larger and a dense pattern was needed over a larger area, the multiple RV capability offers the option of patterning entirely on the single target. In understanding the military effects of KEP weapons,12 it is important to realize that there is no explosive blast (other than that used to disperse the projec- tiles), and thus the extended damage due to overpressure does not occur. Instead, direct structural damage is dependent on the materials response of the target. Many structural elements, such as the wall of a vehicle, the face of a radar dish, or the roof a building, will experience local damage directly at the point of impact, comparable to the type of limited damage caused by meteor strikes, as shown in Figure 4-15. While an increased speed of the projectile increases its kinetic energy, the efficiency with which the energy is transferred to cause lateral damage to the target generally does not increase correspondingly. The size of the damage region will be comparable to the size of the projectile, as shown in Figure 4-15. In the case of the small tungsten rod fragments of a KEP, the structural damage area per particle will be much smaller. Thus, estimating the actual military weapons effectiveness has been the topic of analysis in terms of the susceptibility of the target to the specific action of the small kinetic energy particles of the CPGS warhead.13 In addition, the types of damage must be ranked in terms of how long lasting the damage is. Effectiveness rankings can include an attack that merely delays enemy action for a few seconds or minutes, or an attack that requires the enemy to delay action until a repair can be effected. The timescale required for the repair then becomes a further criterion for ranking the effectiveness. Analyses of a wide range of target types under con- sideration for CPGS have been performed. The results indicate that in most cases, a single CTM KEP will have a high kill probability against fixed soft targets if target geolocation accuracy and guidance, navigation, and control accuracy are as predicted. Current plans call for high-speed sled tests of the KEP warhead and for continued modeling of the effectiveness of the KEP warhead against classes 12 CAPT Terry J. Benedict, USN, Technical Director, U.S. Navy Strategic Systems Programs, “CTM Brief to NAS (U),” presentation to the committee, February 23, 2007, Washington, D.C. (classified); and David W. Lando, Distinguished SLBM Expert, Naval Surface Warfare Center, Dahlgren Division, “CTM: Weapon Effectiveness Presentation (U),” presentation to the committee, July 29, 2007, San Diego, Calif. (classified). 13 CAPT Terry J. Benedict, USN, Technical Director, U.S. Navy Strategic Systems Programs, “CTM Brief to NAS (U),” presentation to the committee, February 23, 2007, Washington, D.C. (classified); and David W. Lando, Distinguished SLBM Expert, Naval Surface Warfare Center, Dahlgren Division, “CTM: Weapon Effectiveness Presentation (U),” presentation to the committee, July 29, 2007, San Diego, Calif. (classified).

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12 TECHNOLOGY ISSUES FIGURE 4-15 Damage to a tile roof and the interior ceiling caused by the strike of a meteorite of estimated mass 0.7 kg with an impact speed of less than 500 ft/sec, illustrat- ing the limited damage potential of kinetic energy warheads. Increased speed of impact on structural elements such as walls and roofs does not cause proportional increases in lateral damage, but primarily increases the number of walls and such that can be penetrated. SOURCE: “The Glanerbrug Meteorite Fall,” posted by the Dutch Meteor Society, Leiden, The Netherlands, May 18, 1998; see . Figure 4.15, bitmapped, uneditable, color of targets. The committee recommends that efforts to define the effectiveness of the KEP warhead against targets of interest be continued, as this information will be relevant to several of the envisioned CPGS systems. The CSM concept envisions the deployment of existing weapons, such as the BLU-108, following deceleration from the reentry conditions. As discussed above, there are technology issues that must be addressed with respect to the dispensing of weapons at high speeds. In addition, the deployed weapons have been well characterized for most target classes of interest, and they are limited in utility for some cases. Some of the difficult issues in addressing mobile targets are described below in the subsection “Mobile Targets.” Fixed Hard Targets Hardened targets include above-ground hardened structures, shallow under- ground structures, and deeply buried targets. The issue of lethality against hard-

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130 U.S. CONVENTIONAL PROMPT GLOBAL STRIKE ened targets was studied recently by the National Research Council. 14 This study concluded that many strategic hard and deeply buried targets can only be attacked directly with nuclear weapons. By their conventional nature, CPGS weapons will not solve the existing shortcomings concerning the attack of these strategic targets. CPGS systems, with the exception of the initial version of CTM, will be capable of attack of hardened above-ground facilities and shallow underground facilities. The lethality against a hardened target depends on the ability of the weapon to penetrate the hardened features of the target, the ability to fuse the weapon properly, and the ability of the warhead to create the desired effects. Currently, penetrating warheads are limited by structural considerations to impact speeds of approximately 3,000 ft/sec, which sets the upper limit to the capability to penetrate hardened structures. Reducing reentry vehicles speeds to this level also creates technical issues of thermal protection and guidance, navigation, and control, as discussed above. The more significant challenges lie in the areas of fuse development and effects generation, although these challenges are not significantly different from those for tactical penetrating weapons. Additional R&D is required prior to the deployment of a smart fuse that is reliable and can operate in the presence of easily implemented countermeasures. Techniques to tailor the delivered effects are also required, especially with respect to buried structures containing or manufacturing components and systems for weapons of mass destruction (WMD). The commit- tee recommends robust investigation of techniques necessary to defeat hardened structures, with specific attention paid to the defeat of WMD components and systems. Mobile Targets Mobile targets represent one of the most challenging types of target for attack by a CPGS system. The problems are different depending on whether the targets move from time to time but are fixed when weapons arrive (e.g., mobile ICBMs parked somewhere in a dispersal area), or whether they are actually moving when weapons arrive (e.g., a caravan of terrorist leaders moving on a country road). Three technical approaches can be considered for attacking moving targets: (1) terminal sensors, (2) remote sensors and weapon data links, or (3) a combi- nation of both. A terminal sensor can be added to a CPGS system to correct for moderate uncertainties in target location. Incorporating the sensor directly in a high-b RV or hypersonic cruise-missile body presents significant challenges relat- ing to the integration with the thermal protection system. Incorporating the termi- nal sensor in a deployed weapon, as proposed in the CSM-2 concept, avoids the 14 National Research Council. 2005. Effects of Nuclear Earth-Penetrator and Other Weapons, The National Academies Press, Washington, D.C.

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131 TECHNOLOGY ISSUES challenging integration with the TPS but requires a high-b RV or cruise missile to slow to an acceptable dispensing speed, which will likely increase its vulnerability in a heavily defended area. The approach of launching a low-b RV to dispense a UAV, as discussed earlier in this chapter, appears an attractive one. Hitting the right moving target is a significant technical challenge. Boost-glide missiles and hypersonic cruise-missile options are assumed capable of deploying BLU-108 submunitions with Skeet warheads. These submunitions are capable of reliably finding motor vehicles (via infrared signatures) and striking them. They cannot discriminate one vehicle from another, however. Originally developed to stop a line of armored tanks, they can be usefully employed if collateral damage is of little importance or if the target vehicle is virtually alone—more than, say, a mile from any other motor vehicle. As a practical matter, in those situations where the target vehicle is moving among other vehicles and collateral damage is to be avoided if possible, human-in-the-loop operations will be required for a CPGS weapon. The committee believes that this will be as true in the year 2020 as it is now. Autonomous target-recognition technology is not advancing at a rate fast enough to solve the significant challenges associated with reliably differentiating one vehicle from another. In large part this is because one cannot predict how, in a given operational situation, the target vehicle will differ from the rest. Perhaps the target vehicle will be identified as “the middle one of three white SUVs traveling in a row.” Perhaps it will be identified by its license plate number. The UAV delivered by the CTM-2 (with UAV) option is assumed to have the necessary capabilities to (1) give remotely located human controllers the visual information that they need to identify the intended target, and (2) permit human control of the UAV, including authorizing it to attack. In this report, it is assumed that CSM-2 and the hypersonic cruise missile could deploy a 2,000 lb UAV capable of the same functions, although it would have less payload and/or range (or loiter time). One possibility for a weapon to arm the UAV is the Hellfire missile. It appears that carriage of at least two Hellfire missiles, at 100 lb each, on either a 3,000 lb or 2,000 lb UAV would be suitable. Battle Damage Assessment Near-real-time battle damage assessment is difficult in most strike situa- tions. Better BDA is seemingly always near the top of the commander’s list of most-desired capabilities. Unique aspects of CPGS option design, along with the application of modern technology, can potentially give CPGS weapons much better BDA capability than the military is used to with any of its existing strike weapons. The essence of a CPGS BDA is to carry in the delivery vehicle a deployable device that can hang in the air above the target as the weapon is delivered, take snapshots of the target before and after the target is (one hopes) hit, take a moment to compress the photos into fewer bits of data, and linger in the air long enough

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132 U.S. CONVENTIONAL PROMPT GLOBAL STRIKE to communicate the compressed photos through a UHF satellite link back to the commander who launched the weapon. What makes this concept potentially better than any existing capability is that the camera is very close to the scene, the photo sequence enables a direct comparison of “immediately before” with “immediately after,” taking time for photo compression and communication after the strike should enable a high-quality image, and the commander has the photos quickly. Any CPGS option could, in principle, incorporate this concept, as could any weapon system capable of carrying and releasing the BDA device. For example, in a later version of CTM, one of the reentry bodies could be such a BDA device. In the boost-glide missile or hypersonic cruise-missile concepts, the delivery vehicle itself could possibly perform the function or, probably better, it could dispense a BDA device along with the weapon. The evaluation of this concept is certainly possible outside the context of CPGS, and if it is technically reasonable, incorporating it within a CPGS system would be a valuable addition. Implications of a Possible Prohibition on Research and Development of Trident-Based Systems Some in the Congress have called for the Department of Defense (DOD) to proceed in its CPGS program in a manner that excludes systems based on the Trident missile. The intent is to maximize an alleged “bright line” between conventional and nuclear systems. The committee strongly recommends that no such prohibition be adopted or imposed. In particular, it believes that CTM R&D would be very valuable even if the CTM were not deployed. It further believes that the CTM-2’s two-stage rocket may sufficiently differentiate it from the full three-stage Trident when tracked by a sophisticated satellite-based system (see Chapter 3 and Appendix H for further discussion of nuclear ambiguity). Turning the issue around, the committee concludes that if Trident-based R&D were proscribed, the effect would be to delay—perhaps substantially—the devel- opment and deployment of any CPGS capability, without actually doing much to reduce the ambiguity problem. It is not that the knowledge gained from CTM (or CTM-2) R&D could not be gained in other ways in time, but rather that much would have to be done from scratch—squandering the many years of base-laying by the Trident Missile Program. In addition, the DOD would have to do substantial component testing for the other options, because the other options simply do not have the advantages of building incrementally from a firm foundation. The least delay (perhaps 2 years or so) would be caused if the alternative system approved were the SLGSM. TECHNOLOGY READINESS LEVELS AND TIME FRAMES Many of the advanced technologies that are needed to provide CPGS system capabilities have been under development in laboratory environments or flown as

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133 TECHNOLOGY ISSUES part of the advanced-configuration development programs. An approximate time line for the various CPGS technology options discussed above is shown in Figure 4-16. These technologies build on the development of existing RV and technology development and existing demonstration programs such as the FALCON, X-43, HyFLY, and X-51. Capabilities beyond the basic ballistic missile and limited boost-glide sys- tems will require the development of more advanced technologies. Boost-glide concepts that use a significant endoatmospheric glide segment will require the operation of a reentry system in a manner that has not been previously demon- strated. One option for development of the CSM involves the exploitation of the reentry vehicle technology developed under the AMaRV program. As envisioned in the initial version of the CSM, the AMaRV vehicles would be scaled up to the size needed to carry the conventional payloads, and the vehicle would be flown with an extended glide segment. The capability of this extended glide segment would be limited by the existing capabilities of thermal protection systems. It is anticipated that this initial capability (labeled CSM-1 in Figure 4-16) would allow for an 800-second glide segment. The committee believes that there are significant technical risks in the operation of existing reentry vehicles in this new flight mode with an extended glide range and that these risks can only be mitigated through system-level demonstration testing. Very long range glide segments will require the development of new thermal protection systems. The DARPA FALCON flight-test program will explore one approach to the thermal protection system in a reentry vehicle with the high lift- to-drag ratio needed for long-range gliding flight. With demonstrations planned for 2009 and 2010, the FALCON program plans a near-term demonstration of the basic operating characteristics of a vehicle technology that may provide a long-range capability for the CPGS mission. The DARPA FALCON technology is envisioned to feed into a second-generation CSM system (labeled CSM-2 in Figure 4-16). If the FALCON program is successful in demonstrating the tech- nologies necessary for long-range gliding reentry vehicles, the ultimate capability of the CSM system could possibly be developed in a single effort, as opposed to a two-stage process. The forward-deployed AHW builds on technologies developed under the Sandia Winged Reentry Vehicle (SWERVe) program conducted in the 1980s. For deployment as a CPGS, the SWERVe vehicle technologies will need to be upgraded to enable flight at higher speeds and longer glide range within the atmosphere. The development of the thermal protection system necessary for a forward-deployed boost-glide system will be similar in nature to the development of the TPS for the CSM system. Significant overlap in technology development for boost-glide systems will likely occur if the forward-deployed boost-glide missiles continue to be seriously considered. The air-breathing Mach 6 missile (hypersonic cruise missile) represents a new class of delivery system, which is immature relative to the ballistic systems.

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E2 and LETB MK-4 RB 13 CTM GN&C accuracy Sea-launched KEP effectiveness ballistic Corona/Apollo CTM-2 with missiles deployed UAV CTM-2 RV scaling MK-500 RB Lethality Assessment SLGSM Sea-launched Medium lift-to-drag shape boost-glide Intermediate TPS missile 3600 s TPS 3000 s TPS FALCON Hypersonic L/D High lift-to-drag In-flight CSM-2 AMaRV CONUS-based Communications boost-glide CSM-1 missile 800 s TPS GN&C accuracy SWERVe Forward-deployed AHW boost-glide Advanced TPS missile GN&C accuracy ASALM Mach 4 Missile Mach 6 Missile X-51 HyFLY Sea- or air- X-43 A/B propulsion launched hypersonic Thermal management missile GN&C accuracy 1980 1990 2000 1970 2005 2010 2015 2020 2025 Year FIGURE 4-16 Technology development time lines illustrating a legacy to all proposed conventional prompt global strike systems. The time lines for future technologies are based on an assumption that investments will continue to be made in critical research and development activi- ties. NOTE: A/B propulsion refers to the four gas generators in the Post Boost Propulsion System on the Trident equipment section (bus) that burn in two stages: the first two burn together called “A” propulsion; once they burn out, a transition is made to the next two gas generators Figure 4.16 called “B” propulsion. The remaining acronyms are defined in Appendix A. landscape,editable color

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135 TECHNOLOGY ISSUES Technology associated with air-breathing hypersonic propulsion systems has been under development in a laboratory environment for the past 30 years and has recently begun transition to the flight-test environment in programs such as the NASA-funded X-43, DARPA/ONR-funded HyFLY, and USAF/DARPA-funded X-51 programs. These programs have demonstrated or will demonstrate critical aspects of the propulsion technology necessary to enable a Mach 6 cruise missile. Furthermore, the Air Force Research Laboratory is exploring the technologies associated with a Mach 6 hypersonic cruise missile under its Robust Scramjet Technology program. In 1998, the National Research Council conducted a study evaluating the U.S. Air Force Hypersonic Technology (HyTECH) program.15 This study concluded that the development of a Mach 6 missile in 2015 was feasible. Although not all recommendations in that report were implemented, the technology readiness of hypersonic cruise missiles is such that this type of capability can be deployed in about 2020. SuMMARY The desire for conventional prompt global strike capabilities with the fewest constraints has led to proposals based on ballistic and hypersonic delivery sys- tems. While establishing such capabilities appears feasible, for some concepts it is at the cutting edge of aeronautic technology. The most-effective development of CPGS capabilities will require a spiral technology evolution in which interme- diate capabilities are developed and tested, with the results serving as the basis for evaluating and developing more-advanced capabilities. Preliminary testing of the CTM system is an excellent first step in such a development process, because it is strongly connected to proven capabilities and allows key new technologies to be evaluated at relatively low cost. Furthermore, the technologies that must be demonstrated for the success of CTM are common to the success of other proposed ballistic/hypersonic programs for CPGS. The development of CPGS options beyond the relatively limited capabilities of CTM will require additional investments in thermal protection and weapons dispensing. Supporting develop- mental efforts in these areas as proposed for FALCON and CSM also provides an important step in the future evolution to the most-effective future systems. FINDINGS AND RECOMMENDATIONS Finding 1. The command, control, communications, computer, intelligence, surveillance, and reconnaissance (C4ISR) systems needed to enable conventional prompt global strike (CPGS) are only sufficient to meet the CPGS time lines under 15 National Research Council. 1998. Review and Evaluation of the Air Force Hypersonic Technology Program, National Academy Press, Washington, D.C.

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136 U.S. CONVENTIONAL PROMPT GLOBAL STRIKE limited conditions. Significant additional effort will be required to provide seam- less integration of numerous disparate systems and to increase the global coverage of the Digital Point Positional Data Base. Recommendation 1. The Office of the Secretary of Defense (OSD) should fund the National Geospatial-Intelligence Agency (NGA) to speed production of the Digital Point Positional Data Base (DPPDB) to increase its geographic cover- age and to develop a means to determine rapidly and accurately the geographic coordinates of any visually identified point (e.g., from a recent photo taken in the field) when that point lies outside DPPDB coverage. Finding 2. Conventional Trident Modification (CTM) represents the only near- term option for a CPGS capability, but the system accuracy has not been demon- strated, and the kinetic energy projectile (KEP) warhead will likely be effective against only a subset of candidate targets. In addition, the limited maneuverability of the proposed CTM reentry vehicle will result in an inability to attack targets in many urban and mountainous regions. Recommendation 2.1. The accuracy of the CTM system needs to be demon- strated in end-to-end system tests. This accuracy demonstration will provide needed information for the CTM system concept, as well as providing important technical information applicable to all CPGS candidate systems. Recommendation 2.2. Evaluation of the KEP warhead effectiveness should be included in the CTM system tests and defined against candidate target sets. War- heads capable of defeating a wider range of targets should be developed. Recommendation 2.3. The baseline CTM system concept should include the development and use of reentry vehicles capable of vertical impact to allow the attack of targets in urban or mountainous environments. Finding 3. A modified version of the Trident missile system, designated in this report as CTM-2, could provide enhanced weapons effectiveness with larger and more flexible payloads. Recommendation 3. The Navy Strategic Systems Programs Office should con- duct a detailed technical assessment of the CTM-2 concept. If deemed feasible, CTM-2 research, development, testing, and evaluation should be provided to address overall system accuracy and weapons effectiveness. Finding 4. More-advanced concepts for CPGS, such as CTM-2, Conventional Strike Missile (CSM), and Advanced Hypersonic Weapons (AHWs), offer the potential for improved system performance through more flexible payloads and

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137 TECHNOLOGY ISSUES trajectories, but these concepts carry high technical risk that must be mitigated prior to any deployment decision. Recommendation 4. OSD should fund the technology development of the longer- term CPGS concepts to address the technical issues associated with thermal pro- tection systems; hypersonic aerodynamics and air-breathing propulsion systems; guidance, navigation, and control accuracy; and munitions dispensing systems. Finding 5. The attack of moving targets and incorporation of battle damage assessment in a CPGS setting will require the development of significant new capability, which could be accomplished with a combination of deployed terminal sensors and weapon data links. Recommendation 5. OSD should fund the technical evaluation of system con- cepts to address the attack of moving targets and incorporation of battle damage assessment, including the dispensing of unmanned aerial vehicles from ballistic missiles or boost-glide vehicles.