Assumptions for Discussion
The U.S. Naval Theater Ballistic MISSILE DEFENSE, tasked against the threat of ballistic missiles that may be armed with Weapons of Mass Destruction (WMD), will be one of the new, key military capabilities deployed in support of joint operations over the next ten years. Technical development issues and doctrinal command and control questions are gradually being resolved as near-term systems approach initial operational capability. As with many new military capabilities, programs and studies tend to focus on discrete areas rather than on an integrating overview of flag-level concerns affecting operational naval TBMD. This paper addresses that need by examining the issues that the Joint Force Maritime Component Commander may need to consider when operating against a TBM-WMD threat.
The intended approach of this study is straightforward, written by a serving surface line officer with extensive AEGIS experience. The assumptions that inform the remainder of the study are detailed immediately to avoid the loss of credibility by a reader who encounters "emergent assumptions" down the line.
The nature of the missile and WMD proliferation threat and the worldwide dynamics that drive it provide a background in the nature of the TBMD challenge, now and into the future. The basic tenets of Joint TBMD are set forth, and the current baseline capabilities to respond to the threat are examined along with an overview of naval active defense TBMD capabilities as currently projected to 2008.
Chapter III is the heart of this study. In logical progression, it sorts and sets forth those critical issues to which the Joint Force Maritime Component Commander must pay personal attention when tasked to operate against a TBM-WMD threat. Quite simply: what questions will keep him awake at night, and how might he possibly address them? Much like a Defense Support Program (DSP) satellite will soon cue a TBMD AEGIS cruiser, the intended purpose of this study is to detect and pass on the nature and parameters of the problem, not to consummate the intercept and solve that problem. Too much is yet uncertain; too much is still evolving. This paper is successful if it illustrates the scope and direction of that evolution, thereby providing a sound intellectual basis for dealing with uncertainty.
An Unprecedented Challenge
Theater ballistic missiles transcend the accepted boundaries of conventional warfare. In speed and altitude, they exceed the envelope of conventional Air Warfare (AW) defenses. In range, they may cross AOR boundaries of geographic CINCs, thus exceeding the "envelope" of traditional in-theater command and control. When armed with weapons of mass destruction or targeted against population centers, the asymmetric political leverage they potentially provide to otherwise impotent aggressors is a new and profoundly unsettling phenomenon. The military response to such unprecedented capability must inevitably be joint.
In an era of reduced U.S. presence overseas, the first American theater ballistic missile defense capability on the scene of a developing crisis is likely to come from the seabut it will be enabled, supported, and eventually reinforced by the complementary capabilities of all branches and possibly bolstered by the synergistic contributions of allies and coalition partners. The ability of these forces to stand firm, build up, and wrest the initiative from hostile forces either diplomatically or operationally may well rest on the ability of the Joint Force Maritime Component Commander to execute the theater ballistic missile defense mission, not in isolation, but in the midst of the messy complexity of multimission warfare in the littoral.
Bounding the Problem. The current state of ferment in the TMD/TBMD arena is the sure sign of a dynamic challenge dynamically addressed. Different concepts, architectures, and systems compete for funding and patronage in an evolutionary process that will eventually produce coherent doctrine and capable hardware. However, in order to examine the theater ballistic missile defense issues of concern to the Joint Force Maritime Component Commander in 2008, the problem must be bounded. The following assumptions do so:
As theater ballistic missile defense concepts continue to evolve, common themes emerge from otherwise disparate documents. It is assumed that by 2008, some of these themes will be fully accepted as tenets of joint theater ballistic missile defense doctrine, to include:
Operational Assumptions. Finally, this study examines what is assumed to be the most challenging kind of operational contingency envisioned for a U.S. Joint Force Maritime Component Commander:
While other kinds of situations are expected to arise, the above conditions are regarded as the most stressing while remaining within the time frame of the next decade.
Navy Theater Wide (NTW). Interception of theater ballistic missiles outside the atmosphere using Theater Wide active defense systems is fundamentally different from the more intuitive "goalkeeping" defense accomplished by lower tier systems. Conceptually, it may be helpful to think of Theater Wide defenses as being akin to long-range CAP engaged in the classic AW outer-air battle, with area defenses fighting the close-range battle within the battle group's missile engagement zone (MEZ). As with CAP aircraft, the area defended by an NTW ship depends more on the location of the defensive platform than on the location of the defended target.
Rather than an enclave-like defended footprint surrounding a single target, NTW involves an "area of negation" within which a single AEGIS ship can patrol in order to intercept TBMs en route from a hostile launch area to many different friendly targets. Herein lies the tremendous leverage of NTW, and the explanation for TBMD briefing slides that show a handful of NTW ships defending all of southern Europe or all of Japan from TBM attack. The kinematics of the NTW interceptor have eliminated the need for these ships to be collocated with single defended assets. Instead, the ships are positioned either somewhat forward in large areas of negation that allow multiple exoatmospheric midcourse and descent-phase intercepts in support of hard-pressed area defense systems, or well forward, where they can exercise the upper tier capability unique to the Navy Theater Wide systemascent phase intercept.
Ascent phase intercept is the holy grail of naval TBMD. The only active defense technique that can possibly exceed its leverage is boost phase intercept (BPI), attacking TBMs while the missiles are still accelerating away from their launchers. Boost phase systems and doctrine remain primarily in the Air Force corner of the joint TBMD arena. Ascent phase active defense, by contrast, engages the strengths of NTW AEGIS combatants, which can patrol in international waters off a hostile shore, with their SPY radars looking inland, awaiting (but not requiring) a DSP cue. As soon as a launch is detected and ROE are met, an NTW interceptor can be on its way to destroy the TBM as soon as it rises above the atmosphere.50 Such a proactive capability produces a defended area covering tens of thousands of square miles.
The only TBMD weapon that will do this is the SM3. Only four inches longer than the SM2 Block IVA, the SM3 missile is actually a four-stage system, starting with the Mk72 booster and Mk104 solid rocket motor it shares with the Navy Area interceptor. "The inertially guided, nozzle-controlled advanced solid axial stage (ASAS) [Now "TSRM" for "Third Stage Rocket Motor"] motor will constitute the third stage. . . . The fourth stage will be the autonomous LEAP KKV [Kinetic Kill Vehicle]."51 Guidance technologies used in this extremely long-range system include missile command uplink, inertial, GPS, and infrared terminal homing. The kinetic warhead (KW) contains no explosive charge. Maneuvering autonomously with thrusters, it homes on the IR signature of the hot TBM revealed against the cold vacuum of space, closing for the kill at several times the velocity of the fastest rifle bullet. The kinetic energy of a moving object equals one-half the object's mass times the square of its velocity. Thus the small but very fast KW packs a serious kinetic punch. When combined with the squared inbound velocity and much greater mass of the incoming TBM, the energy released in the intercept collision is tremendously destructive. If that TBM is carrying a chemical, biological, or nuclear payload, the components are shattered and dispersed outside the atmosphere.
The potential capability of this system is so significant that challenges to its development have proven to be not only technical but political. There has been considerable controversy surrounding the potential effect of NTW on the 1972 Anti-Ballistic Missile (ABM) Treaty. Again, though, it is necessary to review the numbers carefully. When considering Russian strategic systems, "ICBM speed of 6-7 km/sec easily outdistances the 4-5 km/sec of the interceptor, precluding an ascent phase intercept. If an AEGIS ship is near the terminal target of the ICBMby the time an interceptor can be fired and flown out to intercept, the RVs [Reentry Vehicles] are below the minimum altitude of the exoatmospheric hit to kill vehicle."52 Consequently, while the SM3 is potentially extremely capable against medium range ballistic missiles, it is not capable of effectively engaging the high-speed reentry vehicles of a strategic ICBM.
The eventual influence of modern theater ballistic missile defense technology on a treaty involving strategic defense signed nearly a quarter century ago is still being hotly debated, but naval TBMD active defense development is continuing apace and could be available as currently envisioned in 2008. "Both the Navy Area TBMD and the Theater Wide capability have been certified by the Department of Defense to the Congress as fully treaty compliant."53
Sensors. The primary sensor for naval TBMD active defense will be the AEGIS SPY radar. The TBM-tracking capabilities of SPY are being explored and expanded through the use of non-tactical data collection (NTDC) software "patches," experimental modifications that will lead to a tactical TBMD-capable program version. Thus modified, SPY radars have "demonstrated the ability to track TBMs at ranges well in excess of 500km. . . ."54
As with any radar, tracking range is highly dependent on the radar cross section (RCS) of the target, and SPY autonomous ranges against more challenging TBMs will decrease accordingly. Here, battle space can be regained through cooperative tracking by two AEGIS ships, the forward "picket" linking tracks to a consort downrange until the second ship can acquire the target. This capability has been demonstrated in several TBMD extended tracking exercises, including Joint Task Force (JTF-95) demonstrations of the new Cooperative Engagement Capability (CEC), the present-day precursor to the joint composite tracking network postulated for 2008. JTF-95 tests included "a CEC cueing and composite tracking of a TBM target, initially detected by USS ANZIO's SPY-1 radar just after launch. . . . Other CEC units . . . were all automatically cued to acquire the target within seconds. Each maintained a single composite track on the target until it splashed down."55
Cooperative tracking against low-RCS targets can also be enhanced by stationing ships off-axis from the threat trajectory. Multiple aspects of the TBM are thus illuminated by the SPY radars of more than one ship. What might be a very challenging target head-on may give a useful return from its beam aspect. The composite data shared via CEC takes advantage of this phenomenon and thus provides all platforms in the network with the best possible track on the target TBM.
Battle space can be gained not only through sharing track data between radars, but also by using the RF energy of any given radar more efficiently. SPY must search for and detect a TBM before it can acquire and transition-to-track. If radar waveforms and anticipated search volume can be "fine-tuned" early for TBM detection, SPY can acquire and track much faster, thus gaining time in the all-important TBMD OODA loop. Off-board cueing is the key to efficient radar management and early detection.
In 2008, cueing to AEGIS will be primarily a USSPACECOM function via theater-based JTAGS, CONUS-based ALERT, and the third component of the tactical event system, the Navy's Radiant Ivory-derived TACDAR (tactical detection and reporting) capability. The Joint Force Maritime Component Commander must therefore bear in mind that "as friendly operations shift in time and place, the T[B]MD planner must continually reevaluate the areas to be covered by DSP, and effect continual coordination with USSPACECOM to obtain that coverage."56 He must remember, however, that these sensors are in a geosynchronous constellation and are therefore far out in space. Any modification to the geometry of that constellation will therefore involve many miles of satellite repositioning, with the associated consumption of limited thruster fuel. It will also take time. The need for stereo DSP coverage should be established and agreed upon in the initial TBMD planning process, rather than when enemy launches commence.
A significant limitation of national overhead sensors such as the DSP constellation is an inability to gather data on TBMs after boost phase, when the hot plume of the rocket motor no longer exists. This cueing gap will not be fully remedied until the space-based infrared systemlow earth orbit (SBIRS-Low)is deployed (pending full funding). Even then, since SBIRS-Low is by definition a low-earth orbit system, it will have periodic, multipass coverage rather than the continuous "staring" coverage given by a geosynchronous sensor. Without post-boost information, JTAGS-type data will be sufficient to support search volume limitation and waveform selection for SPY, but will not meet criteria for an optimum single beam cue, "an uncertainty volume small enough to be covered by a single beam of a Fire Control Radar system."57
The importance of post-boost-phase sensors for supporting single beam SPY cueing has been clear to the Navy for several years, as shown by the work of Robert Powers, advocating the adaptation of infrared search and track (IRST) equipment to the E-2C aircraft.58 Airborne IR systems can continue to track a TBM after its motor burns out by sensing skin heating of the missile body caused by the friction of its passage through the atmosphere. The E-2C/IRST concept was first known as Gatekeeper.59