Richard L. Garwin
P.O. Box 218
Yorktown Heights, NY 10598
(914) 945-2555
FAX: (914) 945-4419
September 3, 1991
The Honorable Les Aspin The Honorable Sam Nunn
Chairman, Committee Chairman, Senate Armed
on Armed Services Services Committee
2336 Rayburn House 303 Senate Dirksen Office Bldg.
Office Building Washington, DC 20510-1002
Washington, DC 20515
Dear Chairmen:
As you meet in September on GPALS and missile defense, we
hope that you will take into consideration our views as
expressed in this letter. As you know, we have long
participated in both the technological and programmatic
aspects of national security, including many relevant to
missile defense and space weapons. We both have been
members of the President's Science Advisory Committee, and
one of us (RLG) also of the Defense Science Board. Here are
our current views on defense against ballistic missiles, in
relation to the Missile Defense Act of 1991.
Defense of the U.S. against accidental or unauthorized
launch of strategic missiles.
The most important goal of the Missile Defense Act of 1991
is defense against accidental or unauthorized launch of
Soviet strategic missiles. Of course, the Senate is not
implying that the Soviet Union wants to destroy the United
States with an unauthorized or accidental launch-- quite the
contrary. And we have, ourselves, for several years warned
of the problems that could be posed by social and political
disintegration of the Soviet Union while it still possessed
some 30,000 nuclear weapons. We advocated a much faster
pace to the START negotiations, and in addition the
elimination of the Soviet non-strategic warheads. We still
make this recommendation, and hope that you agree.
However, the rebuilding of Grand Forks is likely to be seen
by the Soviets as a hostile act, however peaceful the
intention of the Senate. Reactivation of Grand Forks makes
it unlikely that the Soviets will agree to further reduction
of nuclear weapons, strategic or tactical. This effect will
be much aggravated if we were to renegotiate the ABM Treaty
as proposed in Subsection b.2 of the Missile Defense Act.
The enormous political changes inside Soviet territory do
not permit the U.S. to assume away all traditional concerns
of Soviet military planners. President Boris Yeltsin has
said, "We favor total elimination of nuclear weapons in
Russia" but also "We need to maintain parity with other
nations." President Mikhail Gorbachev would say no less.
Despite vast pending changes in the Defense and Foreign
Ministries, we cannot assume that U.S. actions with regard
to anti-ballistic missile systems will be met with unconcern
and inaction from the Soviets, whatever the organization of
their military. Moreover, the political situation inside
Soviet territory may revert to a more conservative tone.
Accordingly, we see the present moment as an opportunity for
the U.S. and the Soviet Union to proceed with removing, in a
secure and verifiable fashion, some of the excesses of the
assured destruction machinery and its hair-trigger
readiness. We believe this to be more timely, more urgent,
and more practical than attempting actions raising sensitive
issues of the ABM Treaty at the possible cost of derailing
progress toward reducing the Soviet nuclear threat in the
present climate of hope and cooperation.
If multiple ABM sites or a light nationwide defense,
probably permitting nuclear-armed interceptor rockets, were
allowed in the U.S., they would also be allowed in the
Soviet Union. This would degrade our deterrent. In
particular, in response to a possible limited Soviet
aggression, we could probably not retaliate with just a few
nuclear warheads, a measured response that is widely
regarded as essential to credibly deter such aggression.
The ABM Treaty continues to be basic to enhancing our
security through arms control. We endorse the enclosed
statement by the Arms Control Association.
Against the threat of accidents and unauthorized launch of
Soviet missiles, a better protection would be upgrading the
Soviet capabilities to prevent such launch. The U.S. should
offer the Soviets technological help in doing this.
Furthermore, the U.S. should encourage Soviet authorities to
join in an exploration of fundamental changes in both
states' nuclear postures that would sharply reduce their
present reliance on prompt retaliation. These initiatives
would strengthen cooperation rather than arouse Soviet
suspicions.
Defense of the U.S. against Third World ballistic missiles.
We believe that if a Third World state wishes to threaten
the United States with nuclear weapons, it would far more
likely try to introduce these on a cargo ship, a commercial
airplane, or on trucks, than on an ICBM. The same is true
for chemical or biological weapons. Defense against
ballistic missiles would seem to make an unlikely threat
even less likely, and the potential adversary would move to
the delivery means most likely in the first place.
Furthermore, a Third World nation capable of deploying a
nuclear-armed ICBM would almost surely be able to provide
elementary countermeasures against ballistic missile
intercept in space; this would make an effective ABM much
more difficult to achieve, as is discussed in the Appendix.
However unlikely, a threat to the U.S. from a nuclear-armed
ICBM in the hands of a Third World nation would be highly
objectionable. In the spirit of the Non-Proliferation
Treaty, the United States might get together with other
like-minded nations, and with the United Nations, in
agreeing that this will not be tolerated. As in the case of
the Iraq War, the resulting coalition might empower the
United States to destroy such ICBMs on their launch pads it
not before.
Theater missile defense.
In addition to the planned improvements to Patriot, we
support R&D on systems to protect forward-deployed
expeditionary forces against theater ballistic missiles, but
believe the systems considered have not addressed the most
likely and effective near-term threats.
In particular, deployed forces will in the near future
require protection against multiple warheads (biological,
chemical, high-explosive) on a single missile, dispersed
early enough so that 10 or 20 or more effective interceptors
would be needed to nullify a single missile. This would
require emphasis on destroying the enemy missiles before
they can be launched.
In the Appendix we provide a more complete discussion of
Theater Missile Defenses. Here we urge great caution that
the contribution of the ABM Treaty to our security not be
impaired by premature action or legislation that will permit
or even challenge the Soviet Union to test and perhaps
deploy defenses that would not be in our interest. We
suggest that the broad and considered counsel of Generals
Colin Powell and Lee Butler be sought on this matter.
With great appreciation of the work of your two committees
under your leadership, we are
Sincerely yours,
Hans A. Bethe Richard L. Garwin
Cornell University IBM Research Division and
Columbia University
(Affiliation given for identification only)
Encl:
07/00/91 Arms Control Association background paper on
ABM deployments and amendments. (070091.ACA)
09/02/91 Technical Appendix re Missile Defense Act of
1991, etc. (090291MDAA)
RLGP:rlg:Q246LA:090391..LA
*******************************************************************
APPENDIX
TO
LETTER ON MISSILE DEFENSE
by
Richard L. Garwin
IBM Research Division
Thomas J. Watson Research Center
P.O. Box 218
Yorktown Heights, NY 10598
(914) 945-2555
(also
Adjunct Professor of Physics,
Columbia University)
September 2, 1991
ABSTRACT AND SUMMARY. It seems imprudent to suggest that we
want to modify the ABM Treaty of 1972 in such a way as to
permit the Soviet Union more capability against strategic
ballistic missiles. Protection of the entire world against
unauthorized or accidental launch of Soviet strategic
ballistic missiles could better be handled by launch-control
improvements than by deployment of an ABM system.
As for protection of the United States against some
third-world ICBMs armed with nuclear warheads, 100 ABM
interceptor missiles at Grand Forks is an excessive number--
perhaps 20 would be more appropriate, but our best
protection would be constant vigilance against a threat from
the emergence of such missiles and international (coalition)
diplomacy and potential military action against such
missiles.
For protection of our deployed forces, much more attention
should be paid to intercept of warheads (and bombs) at very
low altitude, and especially to the destruction of TBM
before launch.
The protection of allied cities against Theater Ballistic
Missiles (TBM) poses a particularly difficult problem, in
view of the fact that attack effectiveness is increased by
the simple and low-cost measure of splitting the payload
among multiple RVs, both for high-explosive and chemical
payloads. Destruction of the threatening warheads before
they can be launched is the best remedy here, too.
In all of this, U.S. space observation capabilities are
important, as proved by the effectiveness of the Defense
Support Program infrared warning satellites for detection of
missile launch. U.S. capability to operate in this medium
should be preserved and expanded by negotiation of a ban on
space weapons and on antisatellite tests.
Q245MDAA 090291MDAA DRAFT 6 09/06/91
Views of the author, not of his organizations
CONTENTS
INTRODUCTION. . . . . . . . . . . . . . . . . . . . .
DEFENSE OF THE U.S. AGAINST THIRD-WORLD NUCLEAR
WEAPONS. . . . . . . . . . . . . . . . . . . . . . .
DEFENSE AGAINST ACCIDENTAL OR UNAUTHORIZED LAUNCH OF
SOVIET STRATEGIC MISSILES. . . . . . . . . . . . . .
DEFENSE OF DEPLOYED U.S. FORCES AGAINST NON-NUCLEAR
THEATRE BALLISTIC MISSILES. . . . . . . . . . . . .
DEFENSE OF ALLIED CITIES AGAINST ATTACK BY
NON-NUCLEAR TBM. . . . . . . . . . . . . . . . . .
DEFENSE AGAINST A LIMITED BUT DELIBERATE NUCLEAR
ATTACK ON OUR RETALIATORY FORCE BY A RESURGENT
SOVIET MILITARY. . . . . . . . . . . . . . . . . .
SUMMARY. . . . . . . . . . . . . . . . . . . . . .
INTRODUCTION.
This Appendix is based on personal experience in both the
technological and programmatic aspects of national security,
including many relevant to missile defense and space
weapons. These involvements range from the first hydrogen
bomb, through strategic missiles and reentry vehicles, to
x-ray lasers, missile guidance systems, strategic offense
and defense and countermeasures, to current evaluation of
SDIO programs. I have also specifically reviewed the
lessons of the Gulf war in intercepting SCUDs, and have
considered their relevance for defense against theater
missiles and strategic ballistic missiles.
This presentation is somewhat technical and the discussion
abbreviated; the intent is to provide background for
independent views on the various purposes and types of
missile defense.
In a March 1968 Scientific American article,
"Anti-Ballistic-Missile Systems," Hans Bethe and I explained
the capabilities and difficulties of the Sentinel "light"
ABM System that the Johnson Administration was proposing to
deploy against a potential Chinese nuclear-armed ICBM
threat. Although the Nixon Administration and industry
argued strongly for deployment of the Safeguard ABM, and the
Congress acceded, the system was dismantled in 1976 after
about a year of operation. Many arguments had been advanced
for the necessity of deploying Safeguard, but the nation
could have saved some $10-12 B by looking more closely at
the arguments before authorizing deployment.
Today, in 1991, the world has changed, in technology and in
political alliances. Not only has the technology available
for strategic defense changed, but also the nature of the
threats. What can be done about the threat of ballistic
missile attack? What should be done?
In "The Missile Defense Act of 1991" authorizing the
deployment of a 100-interceptor ABM system at Grand Forks,
ND, the Senate responds to a fear of nuclear destruction in
the United States which should be addressed. But the
proposed remedy does not stand up to analysis as a way to
get protection, without raising additional dangers.
First, one must distinguish sharply between nuclear weapons
and chemical warheads, in destructive power, in impact on a
defensive system, and in the ability simply to penetrate a
defense. Second, there is a big distinction between the
Soviet threat (even the accidental or unauthorized nuclear
threat) and a third-world nuclear threat.
We will address the proposed capabilities under five
categories and then return to summarize.
1. Defense of the U.S. against a primitive third-world
ballistic missile threat.
2. Defense against unauthorized or accidental launch of
Soviet ballistic missiles.
3. Defense of deployed U.S. forces against (non-nuclear)
theater ballistic missiles.
4. Defense of allied populations against non-nuclear
theater ballistic missiles.
5. Defense against a limited but deliberate Soviet military
threat against our retaliatory force by a resurgent
Soviet military.
DEFENSE OF THE U.S. AGAINST THIRD-WORLD NUCLEAR WEAPONS.
The proposed deployment of 100 interceptors is an
excessive response to this threat, which is better
handled by diplomatic and military initiatives to
eliminate any Third World nuclear-armed ICBM
threat to the U.S. ICBM delivery of chemical or
biological agents, although unlikely in comparison
with other delivery means, could well use many
bomblets dispensed early in flight and thus not be
vulnerable to any of the proposed defenses. In
any case, reliance on the DSP (Defense Support
Program) satellites for detection of missile
launch would allow a few interceptors at Grand
Forks to do about all that could be accomplished
by the proposed deployment.
We should recall that most third-world nations adhere to the
Non-Proliferation Treaty, are friendly toward the United
States, or certainly have no quarrel with the U.S. that
calls for the deployment or use of nuclear weapons. The
prospect that some 15 nations of the world possess or will
soon possess ballistic missiles is not at all equivalent to
a forecast that they will have ICBMs armed with nuclear
warheads.
The DSP (Defense Support Program) satellites provided
immediate detection of the launch of each SCUD fired by Iraq
during the Gulf War. There is no doubt that these same DSP
infrared detectors would provide immediate detection of the
launch of strategic ballistic missiles anywhere in the
world, and could readily provide trajectory information on
such launches. With that information alone, one could
launch from Grand Forks a small missile to provide intercept
near apogee, with the homing done by autonomous infrared
detectors on the interceptor. For reliability, probably two
such interceptors would be launched against each of the
incoming ICBM weapons. Thus, a deployment of 100
interceptors is excessive against any foreseeable threat,
although the interceptor population could be increased with
time if the threat developed.
But there are two problems-- effectiveness and alternatives.
As for effectiveness, a hit-to-kill intercept outside the
atmosphere can be defeated by the simplest countermeasures,
and it is best to understand this before authorizing
deployment rather than afterwards, as with Safeguard. These
countermeasures have long been published, and consist, for
example, in deploying a large balloon or umbrella around or
attached to the reentry vehicle. The purpose is not to hide
the existence of the reentry vehicle (RV) but to conceal its
precise location. Hypervelocity impact of the interceptor
with this balloon or umbrella at a distance of 20 meters or
so from the RV would cause no damage to the nuclear warhead,
even if the interceptor were loaded with explosive and
pellets.
If such countermeasures seem implausible, remember that we
are talking of a hypothetical third-world nation that is (by
assumption) capable of building and operating ICBMs with
nuclear warheads, in an era in which millions of automobiles
are equipped with "air bags" that inflate in less than one
tenth of a second.
The message is that: any deployment at Grand Forks desired
to protect against third-world threats must, from the first,
be effective against the warhead concealed in a balloon or
umbrella; there should be a few tens of interceptors, not
100; and the defense could be deployed without any
ground-based radar, relying upon DSP and its analogues.
Whether one either needs to deploy or should deploy such a
defense is another question.
A final point is that a nuclear-armed near-apogee intercept
would be far more reliable than a hit-to-kill intercept and
much less vulnerable to attack countermeasures. A few
nuclear-armed intercepters might be included both for the
real effectiveness that they might add and for their impact
on anyone designing a small nuclear-armed ICBM threat
against the United States.
But defense against third-world nuclear weapons can be done
in other ways, probably much more reliable and available
earlier. First there should be no tolerance of a threat to
the United States by third-world strategic ballistic
missiles, especially when paired with nuclear weapons.
There should be every expectation that these would be
destroyed on their launch pads or before, and the United
States should work with like-minded nations of the world to
see that this is done, preferably with the support of a
coalition, as was active in the Gulf.
The nuclear threat to the United States from newly nuclear
nations is probably far more significant from nuclear
weapons carried on cargo ships, on commercial aircraft, or
on trucks, than from ICBMs. Against such threats, a
missile-defense system obviously has no effectiveness at
all, and if the deployment of an ABM system were taken to
signify a reluctance to destroy an ICBM threat before launch
or to retaliate in case of use of any nuclear weapons (and
thus to deter, if possible, the development and use of
nuclear capability), then such deployment would be highly
disadvantageous.
A non-nuclear third-world ICBM could carry a chemical or
biological warhead, but the threat is overwhelmingly greater
from the dispersion of pre-delivered such agents at ground
level. As with third-world nuclear-armed ICBMs (not
theater-range ballistic missiles), deployment of a missile
defense might make an unlikely threat even less likely, by
moving an adversary toward the more likely and effective
delivery means. In any case the effectiveness of
ICBM-delivered chemical or biological agents would be
increased if the missile payload were distributed among many
small reentry vehicles dispersed just after boost phase of
the offensive missile, which would provide dispersion of the
agent difficult to achieve otherwise; against such a threat
none of the proposed systems would have any effectiveness,
except for an international commitment to destroy such
weapons before they could be launched.
DEFENSE AGAINST ACCIDENTAL OR UNAUTHORIZED LAUNCH OF SOVIET
STRATEGIC MISSILES.
Deployment of a "light" ABM protection of the U.S.
for this purpose would be self-defeating because
of the Soviet response in strengthening their own
ABM and in modifying their strategic offensive
force. Protection of the U.S. can be achieved
more effectively and sooner by helping the Soviet
Union to strengthen controls over the launch of
their weapons and by urgent negotiations to reduce
nuclear weaponry on both sides, destroying the
nuclear warheads rather than retaining them as was
done in the INF Treaty.
This is the most momentous goal of the Missile Defense Act
of 1991. Of course, the Senate is not implying that the
Soviet Union wants to destroy the United States with an
unauthorized or accidental launch-- quite the contrary. And
we have, ourselves, for several years warned of the problems
that could be posed by social and political disintegration
of the Soviet Union, while it still possessed more than
30,000 nuclear weapons. We wished and urged a much faster
pace to the START negotiations, and the elimination of all
Soviet non-strategic warheads; we still make this
recommendation.
Unauthorized launch is as likely to be an entire submarine
load of SLBMs as a single missile. Similarly, a whole
squadron of SS-18 missiles might be accidentally launched as
well as a single one. But is it not worth while to defend
against a single accidental or unauthorized Soviet strategic
missile, even if there are other possibilities against which
we would have no adequate defense? Yes, depending on cost,
effectiveness, and alternatives.
The proposed light missile defense would not, in fact,
provide significant protection against the most likely
accidents and it would seriously impede (or reverse)
reductions in the Soviet nuclear threat. The U.S. has long
considered a limited and discriminating retaliatory
capability essential to the credibility of our deterrent of
limited Soviet aggression. This would involve the delivery
of one or a few nuclear warheads against selected targets.
Therefore, if a light nation-wide defense were deployed in
the Soviet Union, the U.S. would need either to reinforce
these hypothetical small-scale options, or provide effective
countermeasures (penetration aids) against that defense.
Which course we would take depends upon the nature of the
defense.
There is no reason to believe that the Soviet Union plans to
use its strategic nuclear weapons any differently--
especially no reason to believe that it would not take all
feasible measures to retain the capability of detonating one
or a few nuclear warheads on U.S. soil. The deployment by
the U.S. of a hit-to-kill ABM system would without doubt
drive the Soviet Union to enhance the countermeasures that
it already has, in the nature of objects tethered to or
associated with the reentry vehicles, and in particular of
umbrellas or balloons to conceal the location of the actual
warhead. So the problem is not only that the U.S. might be
faced with an accidental launch of 10 SS-18s, each with a
complement of 10 real warheads, but that we could not
destroy even a single errant Soviet missile if the Soviet
force responded to the limited defense as we would respond
to such a light nationwide Soviet missile defense.
Furthermore, as has been well documented in Congressional
testimony by T.A. Postol, a single site at Grand Forks would
not do a good job in protecting even the 48 contiguous
states from a single Soviet SLBM launched from near U.S.
shores. What to do?
The severity of the problem of mid-course intercept is
addressed by Ambassador Henry Cooper in his "Special Defense
Department Briefing, SDI and Global Protection Against
Limited Strikes," of 02/12/91. Significantly, speaking of
the budgeted funds for the "Endo/Exoatmospheric
Interceptor," EEI, to intercept the RV as it reentered, he
said,
"That we believe is a more expensive system than
the other (space-based defense), but it may be the
only way to work the mid-course discrimination
problem, which is a very tough problem that has
challenged defense designers for 30 years, ever
since we've been working on this problem."
"If we're able to successfully solve the
discrimination problem in mid-course, then the
ground-based interceptor would be the interceptor
of choice, at least to intercept the missile and
the RVs as far away from the United States as
possible. It is less expensive and would allow us
to perhaps deploy a mix in that instance; a mix of
both ground-based interceptors and the EEI."
This makes the case for the greater effectiveness of
ground-based interceptors in comparison with space-based
weapons. But if the "mid-course discrimination problem"
cannot be solved, space-based weapons will not intercept in
midcourse, but if it can be solved, then ground-based
interceptors will do a better job.
The Director of the SDIO also argues that the space-based
interceptor (Brilliant Pebbles) is cost effective and
affordable, as well as survivable, at a launched cost of
$2-3 million each. He explicitly argues that this is a
"cost-trade that's reasonable" against even the
single-warhead Soviet SS-25. This is surely a conclusion
that will provoke a response from the Soviet Union (former
Secretary of Defense Caspar Weinberger indicated that it
would be the "worst strategic nightmare" he could imagine).
It is just that judgment that will drive analysts in the
Soviet Union to regard their retaliatory capability as being
at risk by a U.S. deployment of a "defense against
accidental launch" whether or not it includes space weapons.
In reality, there is no way in which such a population of
Brilliant Pebbles and Brilliant Eyes could be made
survivable against a specialized Soviet non-nuclear ASAT
that would destroy them over the months that would be
required to build such a population.(1) A deployment of
40-kg Brilliant Pebbles could be defeated much more cheaply
than it would cost to put up, and it would thus impair
rather than add to our security.(2)
The answer in this case is clear. If the U.S. is proposing
to spend some billions of dollars to protect ourselves from
a Soviet unauthorized or accidental launch, we could surely
work with the Soviet Union to have them deploy additional
safety systems, such that their nuclear warheads cannot
explode unless provided with the proper PAL code. We
repeat, it would be worth a lot of money to us to see that
the Soviets do this right, and it can be accomplished more
quickly and surely more reliably than a defense against
unauthorized or accidental Soviet launch, and without the
impairment of our own deterrent that would arise from a
similar Soviet nationwide defense.
In a New York Times OP-ED of 07/31/91, Senator Nunn states
that the Senate Armed Services Committee "is requiring that
the interceptor system it proposes be kept well below a
level that would threaten this philosophy" (of preserving
the other side's retaliatory force effectiveness after a
first strike and in the presence of the planned defenses).
But the problem has always been the "conservative"
evaluation of one's own capabilities against what the other
side might eventually have.
History is littered with "limited" programs that escaped the
bounds set by their originators-- for instance the MIRVed
missile itself remorsefully cited by both Robert McNamara
and Henry Kissinger.
It is quite the same here.
Once the United States begins a deployment of ballistic
missiles against Soviet forces (even with the avowed purpose
of countering unauthorized or accidental launch), the Soviet
Union has no reason to believe that this will stop with the
planned number, especially since the Missile Defense Act of
1991 emphasizes the expansion to multiple sites, not
permitted by the ABM treaty.
Finally, it is unlikely that the Soviet Union would accept a
U.S. deployment beyond the strict limits of the 1972 ABM
treaty without doing their own thing in the ABM field, which
could begin with a more widespread deployment of
ground-based nuclear-armed interceptors. And that would be
the end of U.S. or Soviet strategic force reductions under
START and any follow-on to START.
DEFENSE OF DEPLOYED U.S. FORCES AGAINST NON-NUCLEAR THEATRE
BALLISTIC MISSILES.
The planned upgrade to Patriot will be helpful,
but no projected theater defense will deal with
the most effective threat, which, unfortunately,
can be implemented at low cost, with limited
technology, and with an increased military
effectiveness for missiles of poor accuracy-- the
division of the high explosive (or chemical or
biological) payload into bomblets separated at
high altitude just after the end of powered flight
in the missile launch area. R&D should go
forward, but emphasis should be given to
destruction of threatening missiles before they
can be launched, as well as to very short range,
point defense of individual military targets.
In this regard, especially, we refer to the Issue Paper of
the AAAS Program on Science and International Security,
"Ballistic Missile Defense After the Kuwait War," which
contains useful descriptions of the Patriot deployed
defensive system, as well as of various other candidates for
theater missile defense (TMD) in the development or in the
definition stage. Although in the NATO-Warsaw Pact
confrontation in Europe there was little merit in modifying
the Patriot interceptor to give it some capability against
Soviet short- and intermediate-range ballistic missiles,(3)
the situation is very different against adversaries with
limited numbers of missiles.
In Saudi Arabia and Israel, the technical performance of the
Patriot system against the Iraqi al Abbas "stretched SCUD"
800-km missile probably surpassed expectations, although
analysis is hindered by the absence of any engagement
recording capability on the deployed Patriot systems.
Nevertheless, although Patriot made "intercepts," it very
likely did not detonate the incoming warhead in some cases,
its job being complicated by fuzing problems and by the
tight helical trajectory of the incoming warheads, in view
of the breakup of the al Abbas missile.
The problem of defending our deployed military forces
against theater ballistic missiles (TBM) is not one of
defending against nuclear warheads but against missiles
armed with high explosive or chemical weapons. Clearly it
makes sense to build upon the widely available Patriot.(4)
The Patriot Advanced Capability 3 ("PAC-3") modification
will substantially improve Patriot performance against
aircraft and cruise missiles, as well as greatly increasing
the area defended ("footprint") against theater-range
ballistic missiles. There are several advanced missiles
under development-- ERINT, THAAD, etc.-- which would give a
greatly expanded footprint, and choices will soon need to be
made. Navy AEGIS cruisers with their capable radars could
use interceptors from their own Vertical Launch System (VLS)
or, significantly, could command the launch of ERINT or
Theater High Altitude Air Defense interceptors based in the
target region, providing a theater defense capability which
could be rapidly deployed.
For defending military forces, one could ignore almost all
SCUDS or al Abbas missiles, which because of their
inaccuracy of 1-5 km would for the most part land
harmlessly. Thus, it would be most useful to intercept at
an altitude of 1 km or so, after it had been determined that
the particular warhead was threatening a target of value--
leverage for the defense that is not available in defense
against aircraft.
It should be noted, however, that a low-drag RV on a 800-km
missile would reenter at 3 km/s, at which speed the kinetic
energy of an inert body is equal to that in the same mass of
high explosive (HE). Nevertheless, such energy is not so
damaging as that from HE, only in part because the RV slows
in the atmosphere.
It is far easier to discern the target of a reentering
ballistic missile than of an aircraft picked up by a Patriot
radar at a distance of 50-100 km. The aircraft is
maneuverable, and it could attack any target within the
region; furthermore, the aircraft is far more fragile than
the bombs that it will eventually deliver, and it costs
typically a lot more than the $0.6 M Patriot interceptor.
From all of these points of view, it makes good sense to
destroy such aircraft as soon as they can be intercepted,
with the additional benefit that more time remains for
additional attempts at intercept (shoot-look-shoot). There
is typically a big difference between the radar "appearance"
of an aircraft that has not been effectively intercepted and
one that has been killed by a Patriot interceptor, the
principal difference being in the Earth-intercept trajectory
of the destroyed aircraft itself.
Unfortunately, there may be little difference between the
radar appearance of the "destroyed RV" and one that has
escaped destruction, since pieces of the RV may continue on
the original trajectory. Thus, shoot-look-shoot may be far
less useful for TMD than for anti-aircraft systems, and
relatively more costly.
Enthusiasm for TMD should be tempered by the recognition
that there are sure-fire countermeasures to such systems,
well within the capability of the suppliers or operators of
such missiles. Among the simplest and most effective is the
recognition that the military effectiveness of
high-explosive warheads (or chemical warheads) is increased
by dividing the warhead into a substantial number of
packages, accounting for the popularity of cluster munitions
or "bomblets." For instance, a missile with a 500-kg
reentry vehicle (RV) might instead be equipped with 20-kg
RVs. To have even a chance of nullifying an attack by one
such missile, 20 successful intercepts would be required,
involving 20 interceptors. All that is required to negate
the defense system is for the warheads to separate earlier
in the trajectory than an effective intercept could be made.
Of course, it might be argued that some targets cannot be
injured significantly by such small RVs, so that the
military effectiveness of the attack would be reduced; in
such cases, clearly, the defense is particularly simple,
since one need only wait until an ultra-short-range radar at
this hard target detects a large warhead about to strike, so
that an intercept could be made at a distance of 100 meters!
We urge that such automatic, self-protection systems be
considered seriously, in view of their likely simplicity and
low cost.
Most military targets, however, would be more at risk from a
given TBM payload incident as sub-munitions, and the choice
and pace of investment in defensive systems must be guided
by this fact. Again, this is a significant difference
between attack by TBM and attack by aircraft-- the TBM
sub-munition falls to its target without significant
additional cost, whereas to divide an aircraft into
sub-munitions for delivery over 50-100 km (cruise missiles,
in fact) involves substantial difficulty and additional
cost.
Additional implications for TMD of our deployed forces will
become clear as we now consider protection of allied cities
against attack by TBM.
DEFENSE OF ALLIED CITIES AGAINST ATTACK BY NON-NUCLEAR TBM.
Ground-based interceptors in the theater (or
air-based, or ship-based) will do a better job
than space-based weapons. The existing DSP
(Defense Support Program) missile-launch detection
satellites can cue such ground-based interceptors,
but the overall effectiveness of a strictly
defensive system is very limited, in view of the
potential for attack by missile payloads that have
been separated into multiple (10 to 20) reentry
vehicles, with attendant increase in military
effectiveness. The emphasis should be on
diplomatic and military means to limit the threat
and to destroy the weapons before they can be
launched.
Aside from precious historical, cultural, and religious
sites, modern cities appear both more valuable and more
vulnerable to high-explosive attack than was the case in the
second world war. They may be less vulnerable to incendiary
attack. Nevertheless, one should not count on providing
perfect protection of cities against attack by missiles. In
particular, sub-munitions would get through any of the
proposed defenses, assuming that they are dispensed early
enough. This is particularly important for chemical attack,
which is much more significant against civilian populations
than against military, because discipline and training and
equipment can allow U.S. and allied military to operate in
the face of chemical attack.
Parenthetically, the sooner the United States and
like-minded nations can totally ban the possession as well
as the use of chemical munitions, the sooner it will be
possible to take measures against nations and organizations
that would then be criminals if they merely possessed such
weapons, even if they had not yet used them. Our capability
to detect TBM before launch may improve, particularly mobile
TBM launchers, but it should not be imagined that there will
long persist a requirement for 30 minutes of readying before
launch.
Paradoxically, only the U.S., the Soviet Union, and Iraq are
legally barred from possessing ground-launched ballistic
missiles with range exceeding 500 km; we might use a
long-range air-launched ballistic missile for destroying a
TBM before launch; we might attempt to extend the ban on
ground-launched missiles from a bilateral to an
international treaty; or we might work out with the Soviet
Union a shared joint stockpile of land-based missiles to be
used only for shared international security goals.
How about space-based weapons to intercept longer-range
TBMs? Clearly, one can fly a weapon to 800 km range while
maintaining the ballistic apogee below 100 km.(5) Descending
to that altitude, an orbital weapon would experience heating
of some 100 watts per square centimeter of frontal area,
which would make it difficult if not impossible to use
infrared or optical sensing of its quarry. Furthermore, the
1000 Brilliant Pebbles considered for GPALS would not be
sufficient to provide more than one or two to a given region
during the time a flight of missiles would be near apogee,
so penetration would be guaranteed if several TBM were fired
in a salvo.
In any case, it is perfectly clear that even long-range TBM
are better countered by ground-based interceptors than by
space-based interceptors. SDIO Director Cooper has stated
that the DSP satellites detected every launch of an al Abbas
missile; DSP and forthcoming improvements will continue to
provide such capability, together with a pretty good
indication of trajectory. This will enable a small
ground-based interceptor (THAAD, for example) from anywhere
within 100-200 km of the target area to be launched to
intercept the TBM at apogee, a far simpler job than
at-apogee intercept by a space-based interceptor like
Brilliant Pebbles. For instance, sensor heating on the
ground-based interceptor moving 2 km/s at 100-km apogee is
lower by (2/10)**3 (a factor 1/125) than that of a
space-based interceptor moving at 10 km/s at intercept.
Furthermore, any number of ground-based interceptors could
be launched simultaneously to counter a salvo of incoming
TBMs.
No ground-based radar would be required for such an
intercept, anymore than a ground-based radar would be
invoked to guide a Brilliant Pebbles intercept. Simply put,
if Brilliant Pebbles were expected to work (aside from the
heating of its sensor), then the same homing sensor could be
used on the ground-based interceptor, with the following
aspects that would ease its performance and reduce its cost:
o The electronics life in operation need be 5 minutes
instead of 5 years.
o The sensor need have a field of view of 10 degrees
instead of a hemisphere.
o The sensor need have a range of 100 km rather than
2000 km.
o Batteries can readily power the GBI for 5 minutes
instead of solar cells for the BP.
Furthermore, the ground-based interceptor to counter TBM
would be immune to destruction by Soviet ASAT, unlike space
weapons. Nor would such anti-TBM ground-based interceptors
imperil the ABM Treaty or interfere with a ban on space
weapons or ASAT.
The "Global Protection against Accidental Launch System"
GPALS is expected to include some tens of Brilliant Eyes,
satellites that might be used to track TBMs once the
Brilliant Eyes are cued by Brilliant Pebbles. In fact,
Brilliant Eyes could just as well be cued by DSP. While it
is not at all clear that Brilliant Eyes can do what is
required of it, it is clear that whatever it does in the TBM
role can more readily be done by similar sensors on an
optical probe launched from the ground anywhere in the
theater. At most, one such optical probe would be launched
per TBM, but its required life would be only a few minutes
instead of 10 years. In view of the low-cost "consumer
electronics" proposed for Brilliant Eyes and Brilliant
Pebbles, it would be eminently affordable to expend an
optical probe under such circumstances.
Nevertheless, although GBI and optical probes will do a
better job of at-apogee intercept than will space-based
weapons and Brilliant Eyes, these hit-to-kill intercepts can
predictably be defeated by enclosing balloons or umbrellas.
We have already discussed this problem in the context of
strategic defense.
DEFENSE AGAINST A LIMITED BUT DELIBERATE NUCLEAR ATTACK ON
OUR RETALIATORY FORCE BY A RESURGENT SOVIET MILITARY.
This is not a threat that need nor can be handled
by deployment of an ABM system. The threat is
being reduced in START, and further reductions
should pay more attention to survivability by
allowing the retention of all U.S. silos,
emphasizing the benefit to the U.S. rather than
advantage over the Soviet Union.
No "limited" strike could significantly degrade the ready
silo-based force or the submarine-based missiles at sea. If
it were advantageous to the Soviet military to destroy
Washington by "limited nuclear attack," there are ways to do
so for which missile defense would be irrelevant. Our
command and control system for the retaliatory force is
supposed not to collapse under heavy attack, so it is not
clear why a "limited" strike should be more dangerous. Any
such deliberate limited nuclear strike would be well
equipped with countermeasures against the proposed system
and could be countered only by a defense that is likely to
call into question the effectiveness of the Soviet
second-strike retaliatory force, which would with high
probability be the end of negotiated reduction of the Soviet
nuclear threat.
SUMMARY.
In sum, it seems imprudent to suggest that we want to modify
the ABM Treaty of 1972 in such a way as to permit the Soviet
Union more capability against strategic ballistic missiles.
Protection of the entire world against unauthorized or
accidental launch of Soviet strategic ballistic missiles
could better be handled by launch-control improvements than
by deployment of an ABM system.
As for protection of the United States against some
third-world ICBMs armed with nuclear warheads, 100 ABM
interceptor missiles at Grand Forks is an excessive number--
perhaps 20 would be more appropriate, but our best
protection would be constant vigilance against a threat from
the emergence of such missiles and international (coalition)
diplomacy and potential military action against such
missiles.
For protection of our deployed forces, much more attention
should be paid to intercept of warheads (and bombs) at very
low altitude, and especially to the destruction of TBM
before launch.
The protection of allied cities against TBM poses a
particularly difficult problem, in view of the fact that
attack effectiveness is increased by the simple and low-cost
measure of splitting the payload among multiple RVs, both
for high-explosive and chemical payloads. Destruction of
the threatening warheads before they can be launched is the
best remedy here, too.
In all of this, U.S. space observation capabilities are
important, as proved by the effectiveness of the Defense
Support Program infrared warning satellites for detection of
missile launch. U.S. capability to operate in this medium
should be preserved and expanded by negotiation of a ban on
space weapons and on antisatellite tests.
----------------
1 Roger D. Speed, "ASATs vs. Brilliant Pebbles," Lawrence
Livermore National Laboratory report UCRL-ID-103669
(March 1990)
2 Richard L. Garwin, Nature, 344, 301-302, 22 March 1990.
3 (because the $600,000 cost of a Patriot interceptor
considerably exceeded the cost of a SCUD or other
short-range missile, so that in a large-scale attack the
defenses could have been predictably exhausted, by SCUDS
without nuclear warheads)
4 The U.S. Army reportedly has 53 Patriot batteries
already fielded, with a total of almost 1700 launch
tubes, and orders of Patriot worldwide amount to 190
batteries and 10,300 missiles.
5 D.C. Wright and L. Gronlund, "Underlying Brilliant
Pebbles," Nature, April 25, 1991.