1. Responding to the Emerging Threat of Chinese DF-21D (CSS-5 MOD 4) Anti-Ship Ballistic
Missiles in the Near-Space Environment
LTC Wallace E. Steinbrecher, GA ARNG
Joint Forces Staff College
AJPME 11-07B
March 1, 2011
Faculty Advisor: LTC Larry Dotson

2. Biography
Lieutenant Colonel Wallace Steinbrecher is the Commander of the 170th Military Police
Battalion with headquarters in Decatur, Georgia. He concurrently serves as the Executive
Officer for the Pre-Mobilization Training and Assistance Element with headquarters at Fort
Stewart, Georgia. He was commissioned in 1990 through the Officer Candidate School at Fort
Benning, Georgia. He began his Army career in 1982.
He received his B.S. (Criminal Justice) from Armstrong State University in Savannah,
Georgia, his M.S. (Administration of Justice) from Andrew Jackson University of Montgomery,
Alabama, and is a second-year law student at the Concord School of Law.
He is married to the former Tamra Jean Tebo of South Bend, Indiana, and has two
daughters ages 21 and 19.
THE ORIGINAL VERSION OF THIS PAPER WAS WRITTEN TO SATISFY WRITING REQUIREMENTS OF THE
JOINT FORCES STAFF COLLEGE (JFSC). THE CONTENTS OF THIS PAPER DO NOT NECESSARILY REFLECT
THE OFFICIAL POLICY OF THE U.S. GOVERNMENT, THE DEPARTMENT OF DEFENSE, OR ANY OF ITS
AGENCIES.

3. Thesis
The Chinese are preparing to operationally deploy a new variant of ballistic missiles
specifically aimed at US aircraft carriers. This system can acquire, track, and engage at ranges
greater than 1000 miles.
In the near-term, the US has existing technologies that can be quickly modified to counter
this threat in the near-space (less than 60 miles in altitude) environment. In the long-term,
developing technologies can be used to defeat this threat at all points during the flight envelope.
Defining the Threat
Historically, U.S. aircraft carriers and their associated carrier strike groups (CSGs) have
operated relatively freely under an air defense umbrella and an anti-submarine screening force.
These screening and defense forces provide a stand-off distance that exceeds the range of
conventional anti-ship missiles such as the French-made Exocet with a range of 70 km (MM38)
or 180 km (MM48) (Friedman 1994, 109). One technology that threatens the U.S. carrier fleet in
the Pacific is a variant of the Chinese DF-21/CSS-5 solid propellant medium range ballistic
missile (MRBM). This system has a range of over 2000 km and travels at a speed of Mach 10
(approximately 7612 mph) making it extremely difficult for some shipboard Close in Weapons
Systems (CIWS) to acquire, track and engage successfully. Since the warhead is arriving at the
end of a ballistic arc instead of a flat trajectory as would a conventional ASM, CIWS would be
challenged with a target arriving at an angle anywhere from 20 degrees at long range to 45
degrees at shorter range (Hobgood et al. 2009, 5). If this weapons system were coupled with the
growing Chinese system of space-based and land-based sensors, the integrated system could
acquire, track, and engage targets at over-the-horizon distances exceeding 1000 miles. When
1

4. such integration is achieved, this system could significantly restrict U.S. naval operations during
a crisis in the Taiwan Straits and could threaten US assets in Okinawa and mainland Japan.
Ballistic Missile Flight Envelope
Most research and development into ballistic missile defense has concentrated on
countering strategic weapons such as intercontinental ballistic missiles (ICBMs) and was
centered on kinetic (direct strike) kills. While the DF-21 exhibits a flight envelope like any other
ballistic missile during most of its flight, its ability to maneuver during the terminal phase
enormously makes present kinetic anti-ballistic missile (ABM) systems unsuitable. The primary
difficulty in defending against a ballistic missile is the number of calculations necessary to strike
one object moving at hypersonic speeds with another object moving at hypersonic speeds.
Modern digital computers have moved the solution closer to reality. The US Missile Defense
Agency (MDA) divides a ballistic missile flight into 4 main phases:
 Boost Phase
The missile boost phase is only from one to five minutes. It is the best time to track the
missile because it is bright and hot. The missile defense interceptors and sensors must be
within close proximity to the launch, which is not always possible. This is the most
desirable interception phase because it destroys the missile early in flight at its most
vulnerable point and the debris will typically fall on the launching nations' territory.
 Ascent Phase
This is the phase after powered flight but before the apogee. It is significantly less
challenging than boost phase intercepts, less costly, minimizes the potential impact of
debris and reduces the number of interceptors required to defeat a raid of missiles.
 Midcourse Phase
This phase begins after booster burns out and begins coasting in space. This phase can
last as long as 20 minutes. Any debris remaining will burn up as it enters the atmosphere.
2

5.  Terminal Phase
This phase is the last chance to intercept the warhead. This contains the least-desirable
Interception Point (IP) because there is little room for error and the interception will
probably occur close to the defended target.
Missiles are vulnerable to attack at any phase, but especially so during the launch and the boost
and ascent portion of the midcourse phase.
Figure 1: Typical ballistic missile flight envelope. Some systems are
capable of departing from a ballistic path during the descent phase and
can maneuver upon reentry (From Missile Defense 101: ICBM
Fundamentals 2007, 9).
Prior to launch, if the location of the launcher is known, a strike on it and the associated
support equipment would stop the launch (known as “kill the archer, not the arrow”). However,
killing the archer requires precision-guided munitions (PGMs) systems located at relatively close
range to a known target location, along with associated spaceborne or airborne sensor platforms.
In the case of the DF-21, the use of transportable erectable launchers (TELs) dispenses with the
3

6. need to launch from prepared sites, further complicating the ability to employ “kill the archer”
techniques.
During the boost portion of the flight envelope the missile is easy to acquire since the
exhaust plume is extremely bright to IR sensors. Since the missile and warhead are mated during
this phase and are traveling in a more-or-less vertical manner, the target aspect is largest during
this phase, improving the probability of the kill system acquiring the target. Also during this
phase the missile is traveling through a region of maximum dynamic pressure (max Q) during
which time the airframe stresses are at a maximum value.1 If engaged with a kinetic system
during this phase, a hit anywhere on the missile would be sufficient to cause it to fail.
The midcourse phase of the flight consists of ascending and descending portions. During
the ascending portion, the missile completes staging (if a multi-stage system) and final velocity
is achieved (max ∆ v). The missile is no longer under powered flight and is coasting
(decelerating) to the apex of its ballistic arc (apogee). At apogee, the missile’s velocity is
instantaneously 0. If the payload vehicle is not independently maneuverable, it will begin to
freefall (accelerating) in a mathematically-defined ballistic trajectory just as an artillery round
would fall (this assumes a homogenous atmosphere).
During the midcourse phase, the missile is vulnerable to attack at several points. Once
the missile’s engine reaches burnout, velocity will continue to rise initially as the missile is
entering a region of the atmosphere where drag is decreasing, but will then begin to slow until
reaching apogee when the instantaneous velocity is 0, essentially becoming a stationary target.
Space dynamics are well understood, so as long as the missile is acquired, its subsequent ballistic
1
Considering the definition of dynamic pressure: q = ρ v² / 2, where q is the aerodynamic pressure, ρ (rho) is the air
density and v is the vehicle speed.
4

7. behavior (up to apogee) is reduced to a trajectory calculation. The trajectory calculation remains
valid for the descending portion of the trajectory if the payload vehicle is not independently
maneuverable. The intercept solution becomes much more complex if the missile carries a
maneuverable reentry vehicle. The reentry path can be calculated only as a probability whose
boundaries are determined by the amount of reaction control system (RCS) propellant carried on
board and/or the limits of the flight control surfaces.
Point to vary trajectory in mid-
segment
Apogee (∆v=0)
Terminal guidance
corrections applied
Point of impact
with terminal
guidance
X X’ corrections
X”
Point of impact Point of impact applied
Launch site assuming a pure assuming mid-segment
ballistic trajectory guidance correction
Figure 2: The ability to intercept a missile at X’ and X” represents a capability gap in existing U.S.
systems (From Erickson and Yang, 2009).
Again, just like a ballistic artillery round, these payloads will have a point of impact error
in both range and deflection (defined as Circular Error Probable, or CEP). In order to reduce
CEP to the absolute minimum, a missile can deliver maneuverable reentry vehicles. These
payload vehicles have either an active target acquisition system on-board (radar, IR, video) or
can receive guidance corrections from an external sensor system (spaceborne sensors, over-the-
horizon radar, AWACS). Once the guidance corrections are calculated, either on-board or
5

8. externally, the payload vehicle’s guidance computer system uses RCS thrusters while in the
vacuum of space and/or a system of moveable control surfaces while in the sensible atmosphere
to change its trajectory.
While there are systems in the US inventory that are capable of intercepting simple, non-
maneuvering ballistic threats during the descent or terminal portion of the midcourse phase, there
are no systems that have proven effective against maneuvering reentry vehicles during the
terminal phase. At present, there is no comprehensive, integrated system capable of defeating a
ballistic missile threat during all points of the flight envelope.
Existing Capabilities to Address the Threat
Current US Ballistic Missile Defense Systems (BMDS) are based on a layered defense
model. Each part of the system (both kinetic and sensor) are designed to acquire and attack an
incoming missile at specific phases of the missile’s flight envelope. Some examples of current
and near-term weapons systems and sensor systems are shown in Table 1.
System Name Phase Function
Weapon Kinetic Energy Interceptor (KEI) Boost Intercept
System Airborne Laser (ABL) Boost Intercept
Standard Missile (SM-3) Block 1A Midcourse Intercept
Patriot Advanced Capability-3 (PAC- Midcourse Intercept
3)
SM-2 Block IVA (SM-T) Terminal Intercept
Terminal High Altitude Area Defense Terminal Intercept
(THAAD)
Arrow Weapons System Terminal Intercept
Sensors Cobra Dane Radar Boost/Midcourse Detection/Tracking
Cobra Judy Radar Boost/Midcourse Detection/Tracking
Upgraded Early Warning Radar Boost/Midcourse Detection/Tracking
AN/TPY-2 (Forward Base Mode) Boost/Midcourse Detection/Tracking
6

9. Sea Based X-Band Radar (SBX) Midcourse Detection/Tracking
AN/SPY-1 Midcourse Detection/Tracking
AN/TPY-2 (THAAD Mode) Terminal Detection/Tracking
Green Pine Radar Terminal Detection/Tracking
PAC-3 Radar Terminal Detection/Tracking
Space Tracking and Surveillance All Detection/Tracking
System (STSS)
Space-Based Infrared System (SBIRS) All Detection/Tracking
Table 1: Existing Ballistic Missile Defense Systems (From Hobgood et al., 2009).
These current systems rely on a network of remote and on-board sensors to acquire, track
and maneuver to intercept a ballistic threat. The Chinese DF-21 system has been designed to
exploit shortcomings in the currently fielded systems. Using the example threat of a DF-21
system coupled with a fully-integrated sensor system, the missile could be traveling in excess of
Mach 10 and could maneuver during the terminal portion of the flight, altering its aimpoint and
ultimately forcing the current family of BMDS to estimate a false trajectory (Hobgood et al.
2009, 17). As there are systems that can engage a DF-21 during the flight envelope from launch
to midcourse, this report concentrates on an intercept during the terminal phase.
Terminal Phase Intercept
The terminal phase is very short and begins once the missile reenters the sensible
atmosphere. It is during this phase that the remains of the booster vehicle and any deployed
decoys begin to burn up, leaving the hardened reentry vehicle. This phase is the final
opportunity to make an intercept before the warhead reaches its target. A terminal phase
intercept is the most difficult and most undesirable type of intercept. The computing power
necessary to target a maneuvering vehicle during this phase is tremendous and the warhead will
likely be near its intended target when (if) it is intercepted.
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10. The warhead of a ballistic missile can contain one or multiple reentry vehicles
(warheads). Typically, these warheads are ballistic (free-falling) and their accuracy is totally
dependent on calculations made before launch. By contrast, the DF-21 system will employ a
maneuverable reentry vehicle that can calculate and command course corrections to a target such
as a ship whose position has changed since launch.
A Proposed System
All of the weapons systems illustrated in Table 1, with the exception of the Airborne
Laser (ABL), require the intercepting vehicle to maneuver in close proximity to the inbound
warhead to produce a kinetic kill. As stated, the use of maneuverable reentry vehicles during the
terminal phase enormously complicates the intercept solution. What is needed is a way to
engage the inbound warhead(s) during the terminal phase without having to calculate a precise
intercept trajectory. The desired point of attack for this proposed system is the DF-21’s terminal
guidance system.
One common feature of all maneuverable reentry vehicles is that they possess some sort
of terminal guidance system, whether on-board through a guidance computer or remotely
through a data/telemetry link. Early ballistic missiles such as the V-1 and V-2 of WWII used a
clockwork mechanism for guidance, but most systems since that time rely on an electronic
system (Neufeld 1995, 73).
Electronic systems are susceptible to attack through a mechanism known as an
Electromagnetic Pulse (EMP). In simplest terms, an EMP is a dramatic spike in induced current
through an electronic system that can physically damage it on the component level. Subjecting
8

11. the guidance system to the effects of a strong EMP will render it nonoperational, thus destroying
the missile’s ability to maneuver to the target during the terminal phase.
The advantage of an anti-ballistic missile (ABM) armed with an EMP warhead is that it
does not have to impact with the incoming missile, so a precise trajectory calculation is not
required. The EMP burst radius is a direct function of the electromagnetic power delivered at the
instant of warhead detonation. Simply stated, more power = larger kill radius. A general
discussion of EMP is found in Appendix A and a technical discussion of the means to generate a
non-nuclear EMP can be found in Appendix B.
One of the obstacles to employment of EMP weapons in the past has been the weight of
the capacitors used to charge the EMP device. The introduction of lightweight ultracapacitors
has made it possible to equip current generation ABMs such as the PAC-3 or SM-2 block IV
with effective EMP warheads. A technical discussion of the capabilities of ultracapacitors is
found in Appendix B.
The proposed system envisions the mating of an EMP warhead to a Navy Standard
Missile-3 (SM-3), or an Army Patriot Advanced Capability-3 (PAC-3) missile providing both
land and sea-based capabilities. Flight guidance would be provided by existing AN/TPY-2 radar
systems operating in THAAD mode or by the PAC-3 fire control radar.
The SM-3 is the Navy’s current midcourse ballistic missile interceptor. The SM-3 block
IB features enhanced capabilities and would be the desired candidate for fitting with an EMP
warhead. The block IB design includes an advanced, two-color, infrared seeker for
discriminating targets at greater range. In addition, the missile is outfitted with a Throttleable
9

12. Divert and Attitude Control System (TDACS) that provides the warhead with greater agility,
making it ideal for use against a maneuverable target (Hobgood et al. 2009, 57).
Figure 3: SM-3 (Naval) Concept Architecture
The Patriot Advanced Capability-3 (PAC-3) is the newest iteration of the Patriot missile,
using kinetic kill technology to intercept and destroy tactical ballistic missiles. It is initially
guided by the PAC-3 Fire Control Radar, but receives terminal guidance from an on-board
seeker. The seeker could be reconfigured to act as a proximity detection device to initiate the
flux generator firing cycle.
10

13. Figure 4: PAC-3 (Surface) Concept Architecture
Summary
Future adversaries could have the means to render ineffective
much of our current ability to project military power overseas. (A)ttacks
with ballistic and cruise missiles could deny or delay U.S. military access
to overseas bases, airfields and ports… New approaches for projecting
power must be developed to meet these threats.
-Quadrennial Defense Review Report, 30 SEP 2001
With the DF-21, China may have found an effective way of countering the military might
of the United States in the Taiwan Straits. The limitations of current U.S. legacy ABM systems
create both a strategic and tactical vulnerability that must be aggressively addressed in order for
the U.S. to remain relevant in the Far East. The technologies exist to reliably counter the DF-21
11

14. and the similar systems that will undoubtedly follow it, what remains is the integration of those
technologies into a functioning ABM system.
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15. Appendix A
Electromagnetic Pulse (EMP)
One familiar example of an EMP is a lightning stroke that causes house lights to dim,
flicker, or to go out for a short period. The lightning stroke induces a brief transient of high
current in the power lines which act as antennas. This current spike will cause overcurrent safety
devices (fuses, fusible links, etc.) to “trip out” in order to protect devices connected to the line.
Power lines are engineered to routinely accept such induced surges and the protection devices
reset quickly.
Using an EMP weapon as a way to “blind” an enemy’s electronics grew out of an
analysis of a nuclear weapon test. The Sandia National Laboratory conducted a study of early
nuclear test EMP effects. Its 1989 report stated “(i)n July 1962, a 1.44 megaton US nuclear test
in space, 400 kilometers (250 mi) above the mid-Pacific Ocean, called Starfish Prime,
demonstrated to nuclear scientists that the magnitude and effects of a high altitude nuclear
explosion were much larger than had been previously calculated. Starfish Prime also made those
effects known to the public by causing electrical damage in Hawaii, about 1445 kilometers
(898 mi) away from the detonation point, knocking out about 300 streetlights, setting off
numerous burglar alarms and damaging a telephone company microwave link.” (Vittitoe 1989).
The mechanism of damage to an electronic system by an EMP event is the fast risetime
associated with the current surge. Electronic systems are engineered to “see” a gradual rise in
signal level, and can even recover from an overcurrent event if the risetime-to-peak current is
slow enough. However, as Figure 3 shows, an EMP overcurrent event rises from baseline to
peak (Imax) almost instantaneously. Protection devices such as inrush current limiters, fuses, and
13

16. crowbar circuits cannot react fast enough, so the overcurrent propagates throughout the circuit,
destroying it.
C Imax
u
r
r
e
n
t
Baseline current
Time
FigureSolid-state devices used theguidance systems such as t
3. A current spike. Note in almost vertical risetime.
Transistors and integrated circuits are especially susceptible to damage from an EMP
event, due to their low current handling capabilities. Since there is also a magnetic field
associated with an EMP event, magnetic storage media used for trajectory calculations such as
erasable programmable memories (EPROMs) and computer hard drives can also be corrupted.
As an aside, obsolete electronics technologies such as vacuum tubes are generally immune from
EMP events since their current handling capacity is magnitudes greater than solid-state devices.
Likewise, older media storage devices such as rope-core memories (such as used in the Apollo
Guidance System) are resistant to induced magnetic fields (Hall 1996).
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17. Appendix B
Generating the Electromagnetic Pulse
Until fairly recently, EMP generation has been associated with a nuclear detonation, but
there are non-nuclear ways of generating an EMP2. The concept of non-nuclear EMP was
studied as far back as 1960, when it was postulated that explosive compression of an initial
magnetic flux-containing structure, such as a charged helical coil, would generate an EMP on the
order of 109 J (1,000,000,000, or 1 billion joules of energy3) (Fowler et al. 1975, 2). Such a
device is known as an Explosive Magnetic Flux Compression Generator, or more simply, a Flux
Compression Generator.
To understand how a flux generator works, a basic knowledge of electrical and magnetic
forces is required. Although there are other structures that will work, it is easiest to illustrate
using a helical coil as the flux-containing structure. If a coil is charged with electrical energy
from a source of current, either a capacitor bank or a battery, a magnetic field (flux) is generated.
If an explosive charge is placed so that the conducting surface containing the flux (here, the coil
structure) is driven by the explosive wave front, the result is an electromagnetic pulse delivered
to a load coil (antenna).
2
An EMP generated by a nuclear event is a complex multi-part pulse consisting of the E1 (fast pulse), E2
(intermediate pulse), and E3 (slow pulse). A non-nuclear EMP is not so complex, but at close ranges the mechanism
of damage is the same. The difference in pulse types is due to the fact that nuclear events yield energies on the order
of one million times greater than a chemical energy yield of the same weight.
3
A Joule is defined as the energy expended in passing an electric current of one ampere through a resistance of one
ohm for one second.
15

18. Figure 4. A flux compression generator at rest. Borrowing terms from motor and generator
construction, the helical coil is referred to as a solenoid and the casing surrounding the explosive
charge is called an armature. Other non-moving parts of the structure are called stators.
Figure 5. A flux compression generator at initiation. The detonation is timed so that the explosion
wavefront opens the capacitor bank input at or near peak current. The wavefront propagates down the
coil, “driving” the conductors through the magnetic field. The load switch opens and the pulse is
delivered to the load coil.
16

19. Since non-nuclear EMPs are local in their effects, it is not necessary for the system to
actually impact the incoming missile. While the mechanisms for generating a non-nuclear EMP
are understood, there are several practical issues associated with delivering a workable system in
an anti-ballistic missile (ABM) configuration. Chief among these issues is the weight associated
with the warhead’s initial energy source,
Initial Energy Sources and Weight Reduction
The initial energy charge for the conductors of the generator can come from any of
several different sources. Options include capacitor banks, inductive stores, and battery banks
(Fowler et al., 11). This discussion is limited to a consideration of capacitor banks.
Typical high-energy density capacitors store energy at about 150 J/kg. Thus, to reach an
initial energy of 1 megajoule (106 J,) the initial charge capacitor bank alone would weigh
approximately 6666 kg. By way of comparison, a Sprint ABM missile from the 1970’s weighed
3500 kg, complete with a 1 kiloton W-66 nuclear warhead (Parsch, 2002). Rocket engines are
notoriously inefficient, having to lift their own fuel as well as their payload. While rocket
engines exist that can boost such a payload, a lighter solution is needed.
One possible solution is the Electric Double-Layer Capacitor (EDLC) or ultracapacitor.
The energy density of EDLCs is on the order of hundreds of times greater than standard paste-
filled electrolytic capacitors of the same mass. Thus, a 1 megajoule capacitor bank made of
EDLCs could weigh as little as 7 kg. The EDLC also has a fast discharge time due to its low
internal resistance. Conventional capacitor discharge times are reduced as capacitance is
decreased; with an EDLC, high capacitance values and fast discharge times are both possible
(Fowler et. al, 12).
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