Order Code RL33240
CRS Report for Congress
Received through the CRS Web
Kinetic Energy Kill for Ballistic Missile Defense: A
Status Overview
January 18, 2006
Steven A. Hildreth
Specialist in National Defense
Foreign Affairs, Defense & Trade Division
Congressional Research Service ˜ The Library of Congress

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Kinetic Energy Kill for Ballistic Missile Defense: A
Status Overview
Summary
For some time, U.S. ballistic missile defense (BMD) programs have focused
primarily on developing kinetic energy interceptors to destroy attacking ballistic
missiles. These efforts have evolved over almost 30 years and have produced a
significant amount of test data from which much can be learned. This report provides
a broad overview of the U.S. investment in this approach to BMD.
The data on the U.S. flight test effort to develop a national missile defense
(NMD) system is mixed and ambiguous. There is no recognizable pattern to explain
this record nor is there conclusive evidence of a learning curve over more than two
decades of developmental testing. In addition, the test scenarios are considered by
some not to be operational tests and could be more realistic in nature; they see these
tests as more of a laboratory or developmental effort. Success and failure rates (and
their technical causes) have shown relative consistency through this period.
The U.S. flight test effort to develop theater missile defense (TMD) systems
appears more promising. In relative terms, developmental and operational testing of
TMD systems has been more successful than the NMD effort. Nonetheless, TMD
systems that evolved from mature, existing ground and sea-based air-defense systems
have demonstrated greater test success than other TMD programs.
How effective has the U.S. investment been in developing kinetic energy BMD
systems? Observers could make any number of arguments as to what the record
means and what could be done to improve the effectiveness of systems under
development and of those deployed. This report will be updated as events warrant.

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Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Summary of Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Long-range Ballistic Missile Defense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Theater Missile Defense (TMD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

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Kinetic Energy Kill for Ballistic Missile
Defense: A Status Overview
Introduction
The U.S. effort to develop and deploy ballistic missile defenses (BMD) based
on the concept of hit-to-kill or kinetic energy kill1 began three decades ago.2 This
effort gained momentum as the primary focus of the U.S. BMD program in the mid-
1980s with the announcement of President Reagan’s Strategic Defense Initiative
(SDI).3 Since that time, the United States has pursued ten major kinetic energy BMD
programs; these have produced hundreds of various flight test results. These test
results and some very limited operational experience in wartime provide sufficient
data for at least some conclusions regarding the decades-long U.S. investment in hit-
to-kill as a concept for BMD. This overview report examines the U.S. investment in
that concept, what that investment has produced, and raises various questions that
might be considered. The development of BMD has shown important technological
differences between efforts designed to attack and destroy short or medium-range
ballistic missiles and those designed for long-range or intercontinental ballistic
1 Kinetic energy kill interceptors seek to destroy targets through a direct collision at high
speeds. The force of the impact destroys the attacking missile or warhead, renders it
inoperable, or diverts it from its intended target. With such an approach, a near-miss has the
same effect as a large miss distance: the targeted warhead or missile is not destroyed. From
its beginnings, kinetic energy kill concepts held the promise of destroying attacking missiles
without the potential collateral effects of nuclear weapons explosions inherent in earlier
BMD concepts and deployed systems.
2 During the 1960s and early 1970s, the United States developed and tested a nuclear BMD
interceptor capability. This system was deployed in North Dakota for a short time in 1975-
1976. This system was dismantled for many reasons, including congressional and military
concerns over its cost ineffectiveness in the face of a potentially massive nuclear attack,
concerns over the adverse effects that nuclear detonations would have on nearby ground
based BMD radars, and growing support for agreed upon limitations of U.S. and Soviet
long-range nuclear arsenals. In the FY1976 defense budget, the Army initiated a program
to examine alternatives to nuclear BMD. A couple years later, this effort led to the first
specific kinetic energy program that sought to avoid the problems of nuclear effects on
ground-based BMD interceptors by seeking to place guidance and other sensors on a non-
nuclear missile interceptor itself.
3 On March 23, 1983, President Reagan delivered a policy address announcing the
establishment of the Strategic Defense Initiative (SDI) or what was quickly dubbed by others
the “Star Wars” program. In his speech the President expressed his vision that the nation’s
scientists could develop the means of rendering “nuclear weapons impotent and obsolete.”
Various contemporary and historical accounts confirm that the President intended the
development of U.S. BMD to be non-nuclear as well. Initial funding for the SDI program
began in FY1985.

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missiles.4 Therefore, this report will review and distinguish between the program
results of theater missile defense (TMD) and national missile defense (NMD).
CRS received historical flight test data5 from the Missile Defense Agency
(MDA).6 It is important to note that for each of these flight tests there were various
primary and multiple secondary objectives.7 Such flight tests are inherently complex
and relatively costly. Therefore, multiple test objectives are designed to maximize the
potential benefit derived from each flight test. The determination as to whether each
of these objectives was reached was made by each relevant agency or military branch.
All of the references to flight test results in this report are derived from the Flight
Tests Results memorandum provided by the MDA unless otherwise referenced.
Summary of Analysis
Analysis of flight test data shows that the U.S. effort to develop, test, and deploy
effective BMD systems based on this concept has had mixed and ambiguous results.
The actual performance in war-time of one kinetic-energy system currently deployed
by the United States (i.e., the Patriot PAC-3) is similarly ambiguous. Further, it is not
yet possible to assess the operational capabilities of the other deployed system (i.e.,
the National Defense System).
Long-range Ballistic Missile Defense
The United States has pursued four major kinetic energy interceptor long-range
BMD or NMD programs since the early 1980s: Homing Overlay Experiment (HOE),
Exoatmospheric Reentry Interceptor Subsystem (ERIS), National Missile Defense
(NMD), and Ground-based Midcourse Defense (GMD). Each of these is briefly
discussed below.
The Army developed HOE in the late 1970s and early 1980s to test the viability
of the emerging hit-to-kill concept. It conducted four intercept flight tests in 1983 and
4 For instance, some of the technological challenges are different because of where the final
engagement occurs (within the atmosphere or in space) and because the closing velocities
of these engagements can vary significantly (between shorter and longer range attacking
missiles).
5 There are any number of tests on systems, sub-systems and components prior to any flight
test of the actual missile and interceptor itself. Pre-flight test data are not included as part
of this report.
6 MDA, “Congressional Research Service Inquiry: Flight Test Results,” June 21, 2005. For
Official Use Only.
7 For illustration, an intercept flight test might have as primary objectives to: 1) demonstrate
integration of system elements; 2) demonstrate sensor operations; and 3) demonstrate kill
vehicle performance (intercept the target). Secondary objectives might include 1)
demonstrate test monitoring; 2) provide risk reduction for future tests; and 3) collect data
for model verification. Most primary and secondary objectives could be met, even if the
intercept objective failed, for instance.

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CRS-3
1984. Three of the tests failed to intercept the intended target,8 but the fourth was
considered a success. The Army did not identify any secondary flight test objectives.
Nonetheless, the nascent SDI program then viewed the single reported success as
evidence of the promise of non-nuclear BMD interceptor technologies.
The technologies tested in HOE served as the basis for its successor program,
ERIS. ERIS went through a lengthy development program before flight testing began
in 1991 with the first of four intercept flight tests. Although the first was considered
a successful intercept of the target, the following three intercept attempts through
1992 failed to destroy their intended targets.9 Even so, officials concluded that half
of the primary and secondary test flight objectives were accomplished, and that the
primary BMD concept being pursued held significant promise.
The NMD program followed ERIS with a series of eight flight tests from 1997
to 2001. The first three were planned “fly-by” tests. There were no intercept attempt
objectives. The first one failed to launch; however, the other two were deemed
successful in their primary objectives. No secondary objectives were identified. Of
the five planned intercept attempts, three reportedly intercepted their intended targets;
one ended in failure because the interceptor kill vehicle did not deploy and the other
failed because the on-board sensors designed to track and intercept the target failed.
Officials concluded that 17 of the 20 primary objectives were met or partially met
and all the secondary objectives by the planned intercept tests were met.
The current GMD program (NMD’s successor) began flight testing in 2002.
Since that time six flight tests have taken place. Five of these flight tests were
planned intercept attempts, with three resulting in failure to intercept.10 Officials
concluded that about 80% of the program’s 40 or so primary intercept flight test
objectives were met; all the secondary objectives were met fully or partially. In 2004,
the GMD undertook a new configuration with a different booster and interceptor. It
flew a successful integration flight test (non-intercept test) in early 2004 with all
primary and secondary objectives met. This system was deployed in Alaska and
California in 2004 and declared operational after eight missiles were placed in silos.
Subsequently, two planned intercept flight tests in December 2004 and February
2005 failed to launch. The currently deployed system thus remains to be tested
successfully against targets it might be expected to intercept.
Each of the four NMD programs were different, but they built on the limited
successes of their predecessors. Of the eighteen or so attempted intercepts since the
early 1980s, seven of them were considered successful, or roughly a 39% intercept
rate in tests. Officials cited several reasons, including program hardware and
8 Two failed tests were deemed failures because of hardware related problems. The other
intercept flight test reportedly failed due to software errors in the on-board computer.
9 Each of the three failures was due to a different reason: the interceptor failed to launch, the
target failed to launch, and the third attempt missed its intended target.
10 In one test, the kill vehicle did not separate from the booster rocket, in the other two
launch attempts the ground-based interceptor did not launch (once because of a software
problem and more recently because of a problem with the missile silo).

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software, as well as interceptor silo and target launch failures.11 From that, there do
not appear to be any recognizable patterns that emerge to account for the mostly
unsuccessful history of the effort. Nor is there conclusive evidence of a learning
curve, such as increased success over time relative to the first tests of the concept 20
years ago.
Program supporters can point to limited evidence that, under controlled
conditions, there is reason to support the contention that kinetic energy interceptor
technology for use against long-range ballistic missiles holds promise. Critics of the
flight test effort to date,12 whether they support missile defense or not in general, can
raise questions about the success rate and the realism of the testing effort, given a
generation of U.S. investment in its development.
Can kinetic energy interceptor technologies for use against long-range ballistic
missiles be developed successfully and deployed as an effective part of the U.S.
military posture? The answer appears to be ambiguous at this juncture. Can the now-
deployed NMD system protect the United States from long-range ballistic missile
attacks? Currently, there is insufficient empirical data to support a clear answer.
Theater Missile Defense (TMD)

There have been six major kinetic-energy TMD programs since the early 1990s:
Extended Range Intercept Technology (ERINT), Flexible Lightweight Agile Guided
Experiment/Small Radar Homing Intercept Technology (FLAGE/SRHIT), Navy
Lightweight Exoatmospheric Projectile (LEAP), the Navy Aegis BMD, Patriot PAC-
3, and Theater High Altitude Area Defense (THAAD). Each of these are briefly
examined below.
The Army’s FLAGE/SRHIT program conducted eight flight tests from 1984-
1987 to prove the feasibility of lower atmosphere intercepts. Five of these flight tests
were planned intercept attempts. From the data provided by MDA all the primary and
11 Although the causes of failures are varied (i.e., they include hardware, software, and
interceptor and target launch problems) and do not necessarily suggest any systemic causes
such as system integration, some might suggest that quality control throughout the
manufacturing, systems integration and test preparation process could be a common root
cause.
12 On occasion, private organizations and others such as the Government Accountability
Office (GAO) have released analyses of some of these tests. Sometimes they drew similar
conclusions as those provided by the Missile Defense Agency. On other occasions, they took
issue with the flight test results. Although many consider these efforts useful and
constructive, because such studies lack a common framework for analysis and also do not
examine all of the tests cited, their potential significance or meaning for the overall 30-year
research effort is unclear. For instance, see GAO. BMD: Information on Theater High
Altitude Area Defense (THAAD) and Other Theater Missile Defense Systems.
GAO/NSIAD-94-167, May 3, 1994; GAO. BMD: Records Indicate Deception Program did
not Affect 1984 Test Results; GAO/NSIAD-94-219, July 1994; and Federation of American
Scientists, Chronology of Hit-to-Kill Missile Tests, by George Lewis, April 16, 1997,
[http://www.fas.org].

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secondary test objectives in the series were achieved. The targets included stationary
targets in the atmosphere and an air-launched target. Only one target, however, was
a short-range missile. The degree to which any conclusions might be drawn regarding
very short-range hit-to-kill in this effort is therefore limited.
Building on the SRHIT effort, the Army’s ERINT flight test program (1992-
1994) conducted five flight tests. Three of these were planned intercepts; two of these
three flight tests successfully intercepted their targets (the failure cited was hardware
related). Despite the missed intercept, the Army concluded that all of its primary test
objectives for the three tests were met fully or partially, and that all but one of the 26
secondary objectives in the three tests were met. As far as the two non-intercept flight
tests were concerned, the Army determined that all of its primary and secondary
flight test objectives were met.
The Navy developed its own indigenous LEAP program, which flight tested
from 1992-1995. Three non-intercept flight tests achieved all primary and secondary
objectives. Of the five planned intercept tests, only the second was considered a
successful intercept, however. Failures were due to various hardware, software, and
launch problems. Even so, the Navy determined that it achieved about 82% of its
primary objectives (18 of 22) and all of its secondary objectives in these tests.
Building on some of its previous efforts in SRHIT and ERINT, the Army’s
THAAD program nevertheless experienced significant challenges from 1995 to 1999.
After three relatively successful non-intercept flight tests (almost all of the primary
and secondary test objectives were partially or fully met), THAAD failed to intercept
in seven of its nine planned attempts. However, the THAAD intercept flight test
program met about half of its primary and secondary objectives. Because the last two
intercepts were successful (the last being in 1999), the Department of Defense and
Congress agreed to further develop, but revamp, the THAAD program. The current
THAAD program is a redesign of the former THAAD system. Recently, the program
conducted its first flight test (non-intercept) to examine the launch, boost, and fly-out
functions of the THAAD missile. MDA officials considered this test successful.13
The Army’s Patriot (Phased Array Tracking to Intercept of Target) program has
a history dating to the 1960s as an air-defense weapon. Only in the mid-to-late 1980s
at the insistence of Congress was the program given a specific anti-missile role.14
Using a focused explosive charge (non-nuclear and not hit-to-kill technology), Patriot
PAC-2’s (Patriot Antitactical Capability) 1991 Desert Storm performance remains
controversial. After the war, Patriot improvements for missile defense were widely
supported. Testing of the Patriot PAC-3 with a kinetic energy interceptor began in
1997. After the initial two successful non-intercept flight tests (most of the objectives
were met), the Patriot PAC-3 attempted 27 intercept tests, of which 21 (about 78%)
were considered successful intercepts. Additionally, some 92% of the primary
13 Missile Defense Agency Bills Last Week’s THAAD Flight Test a Success, Inside the
Pentagon, December 1, 2005.
14 U.S. Library of Congress. Congressional Research Service. The Patriot Air Defense
System and the Search for an Antitactical Ballistic Missile Defense. CRS Report 91-456F,
by Steven A. Hildreth and Paul Zinsmeister, June 16, 1991. Report available from authors.

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intercept test objectives were met, as well as almost all of the known secondary
objectives. In terms of actual wartime use, the Patriot PAC-3 was used in Operation
Iraqi Freedom (OIF) in 2003, but its role was very limited (four missiles fired in two
successful engagements) and thus, while suggestive of significant promise, its
operational effectiveness remains uncertain based on limited empirical data.15
Building on its previous efforts as well,16 the Navy more recently has conducted
six (of seven) successful intercept tests of its Aegis BMD (or Navy sea-based)
program using the Standard Missile-3 (SM-3) Block 1 missile (2002-2005).17 The
most recent test was against a warhead target that separated from the booster rocket
itself, in contrast to earlier intercept tests against SCUD-type ballistic missiles.
Primarily because of the Patriot PAC-3 flight test and operational record and the
more recent Navy BMD program, the concept of hit-to-kill for TMD appears
promising. Older TMD efforts were not as suggestive, and the foundation for the
current THAAD program is based mostly on prior test failures. Nonetheless, because
there is no flight test data yet on the current THAAD program, nothing conclusive
can be said about its potential future for success. And, although the Patriot PAC-3
shows promise, some might note that the Patriot system itself has been evolving for
about 40 years now. Additionally, much of the Navy infrastructure and technology
supporting the Aegis SM-3 is decades old and is comparable in evolution to the
Patriot air and missile defense system.
Conclusion
A central question might be: at this stage how well is the United States doing
in developing effective ballistic missile defenses based on this kinetic energy kill
concept? Since the announcement of the SDI program in the mid-1980s the United
States has spent about $100 billion on missile defense with a primary focus on the
kinetic energy or hit-to-kill concept. U.S. programs began looking at that concept a
decade earlier into the mid-1970s.
Supporters of hit-to-kill could argue that what the United States is striving to do
has indeed proven to be challenging, but that progress is being made. Furthermore,
15 Nine Iraqi ballistic missiles were targeted by Patriot. Another six were launched but not
targeted by Patriot because they were projected to land in areas that would not cause harm.
The missiles that Iraq fired in 2003 were slower flying and of shorter range than those fired
in 1991. The Defense Department concluded that the Patriot system successfully intercepted
all nine missiles it targeted. Seven of the intercepts, however, were made with the older
Patriot PAC-2 system (which still used a proximity warhead to destroy its target), while the
remaining two were intercepted by the newer PAC-3. One Iraqi cruise missile reportedly
eluded the Patriot radar and hit a sea wall in Kuwait City. And the Patriot system was also
involved in three friendly fire incidents that resulted in the loss of a U.S. and British aircraft.
16 The Navy program has evolved over several decades from a sea-based air defense and
cruise missile defense capability to include ballistic missile defense.
17 Sea-based Missile Defense “Hit To Kill” Intercept Achieved, News Release, Missile
Defense Agency, November 17, 2005.

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success measured in terms of operationally effective deployed BMD systems based
on this concept, loom on the horizon. They could also argue that threats posed from
the proliferation of ballistic missiles and weapons of mass destruction (WMD) must
be addressed by developing effective BMD systems.
Supporters and skeptics could argue the need for an independent, comprehensive
evaluation of the test record to determine whether any systemic or conceptual
challenges are impeding the U.S. effort. Although some defense officials have
provided testimony and private and government agencies have looked in detail at a
few of these tests, some might argue that a comprehensive and independent review
of the entire record to date has not been undertaken and is warranted.18
Other observers might argue that alternatives should be pursued as a hedge
against the possible failure of this concept for either NMD or TMD. Such alternatives
could be military in nature, such as reducing the emphasis on BMD in favor of
increased emphasis on counter-force (i.e., attacking and destroying enemy missile
systems before their missile could be launched). Alternatives also could focus on
other ways to mitigate ballistic missile proliferation (e.g., arms control). Some
alternatives, such as a return to nuclear BMD concepts or emphasis toward more
exotic technologies (e.g., lasers or weapons in space) might face opposition on
political or technical grounds.
Still other observers could argue that in general the United States needs to make
a more concerted effort to increase developmental testing across the board, before
these systems are ready for more realistic testing regimes. They could argue that
almost all the testing to date is of a developmental nature and that an operational
testing regimen has not been developed, but remains essential. Only then, they could
argue, could assessments to confirm the validity of the hit-to-kill concept for BMD
be made with confidence.
18 One such review, performed by experts for the MDA, examined the flight test record of
the NMD program and concluded among other things inadequate quality control in the flight
test record was a factor. See Missile Defense Setbacks Stall Program, CNN.com, July 11,
2005.

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