AS the conflict in Iraq unfolded this
spring, the world watched in amazement at the accuracy of the latest
generation of precision-guided missiles. These weapons allowed U.S.
and allied air forces to operate unconstrained by the limits of
daylight, and they came to rule the night. Now, the
U.S. armed forces want to further extend this weapon capability
by developing armament that will reduce collateral damagethat
is, reduce destruction outside the radius of an intended targetwhile
enhancing its destructive force on the target.
this goal, explosives and composites experts at Lawrence Livermore
are leading an effort under a memorandum of understanding (MOU)
between the Department of Energy and the Department of Defense that
was formalized in 1985. The MOU established a joint munitions program
that takes advantage of the Laboratorys expertise in high
explosives, computer simulation, and other technologies. In the
present effort, a Livermore team led by engineer Michael Murphy
is working in partnership with the Air Force Research Laboratory
at Eglin Air Force Base in Florida and the Naval Surface Warfare
Center in Dahlgren,Virginia. The team is developing munitions with
carbon-composite casings filled with new formulations of a high
explosive that will greatly reduce damage to objects beyond the
researchers have studied high explosives for decades as part of
their work in designing nuclear weapons. The Laboratory is the first
to design a carbon-composite cased munition with an enhanced-blast-formulation
explosive. Much of the weight in todays munitions is
in the steel casing, explains Murphy. The heavy steel
case, coupled with a high explosive, can penetrate hard targets
such as reinforced concrete bunkers. However, the blast created
by conventional steel-cased munitions can send shrapnel to distances
of more than 1 kilometer from the target. This puts civilians and
friendly forces at risk. Were trying to change that by developing
carbon-cased munitions with penetration capability.
challenge for the Livermore team was to design a munition that could
penetrate hard targets as deeply as a steel-cased munition while
restraining the energy of the blast within a small radius. Murphy
notes, If you could get the job done without throwing all
that steel around, you would reduce collateral damage. It is a matter
of controlling the energy and putting it to better use. Carbon
composite is lightweight, and the weight of the carbon-composite
case will account for only 10 to 20 percent of a munitions
total weight. The Livermore team working on the composite-case design
and fabrication technology is led by engineer Scott Groves.
The first question facing the researchers was whether a composite
case could penetrate concrete as deeply as its steel counterpart.
In experiments conducted by Don Cunard at Eglin, Grovess team
demonstrated that it could. The steel-nosed composite penetrator
used in the experiments is a half-scale construction of the one
used by the military. Shot at a velocity of 494 meters per second,
it reached a penetration depth of 48 centimeters, far exceeding
the penetration goal of
15 centimeters. In another test (see figure below), a penetrator
traveled through 30 centimeters of concrete, 300 centimeters of
sand and plywood, a 1.3-centimeter-thick steel cover plate, and
another 15 centimeters of concrete, for a total distance of 3.3
meters. One advantage of the composite case, Groves surmises, is
that it may be more slippery than steel, which results in less friction
new munition is designed with an enhanced-blast explosive,
which increases the impulse delivered to the intended target,
and a carbon-fiber composite case, which eliminates collateral
damage caused by case fragments. The graph shows that even
though the new munition produces a more powerful blast, the
range of its damage footprint is smaller than that of conventional
Balancing Destruction and Safety
enhance the energy delivered to a target while also controlling
the radius of the damage area, Livermore researchers Randy Simpson,
Mark Hoffman, Roz Swansiger, Wardell Black, Rob Schmidt, and A.
J. Boegel are formulating and testing a triamino-trinitrobenzene-
(TATB-) enhanced explosive. TATB has long been used at Livermore
because it is a powerful explosive that is also very insensitive;
that is, it is highly unlikely to explode accidentally. At the
time, the Air Force is developing an enhanced-blast explosive with
cyclotetramethylene-tetranitramine (HMX). HMX delivers more energy
than TATB, but it is also far more sensitive. Its a
tradeoff between safety and energy, says Murphy. Weapons
need to be powerful enough to do the job but safe enough so they
are not vulnerable to accidents during transportation.
conducted at half-scale demonstrate the ability of the carbon-fiber-cased
projectile to survive the penetration through a target consisting
of high-strength concrete, packed sand and wood, and steel.
The lower part of the figure shows that the projectile survived
intact while penetrating through the multilayer target. It
penetrated deeper than expected and was not stopped by the
soft-catch chamber of sand and wood.
Testing the Enhanced Formulas
To test the new TATB-enhanced formulation, researchers conducted
static detonation experiments to measure the radius of the blast
created. The goal was to deliver the most damage at close range,
while leaving objects at a distance intact. In one test conducted
at the Air Force Research Laboratory, insulating foam bundles were
placed at distances of 2 meters, 3 meters, and 5 meters from the
charge as a method of collecting the resulting case fragments. The
foam bundle at the 2-meter range was obliterated while the foam
bundles at the 3- and 5-meter distances had no case fragment penetrations
and thus were unscathed. The few carbon case fragments that were
recovered at the 2-meter range measured less than 1 centimeter each;
no fragments were recovered beyond this distance. The Livermore
team and its Air Force and Navy partners are strongly encouraged
by the results.
The explosive fill in the munitions is fabricated from a mixture
that has the consistency of toothpaste. The mixture is cast into
the carbon-fiber case and cured. This process allows the munitions
to be created in a variety of shapes for use in many different applications.
The munitions created with the new technology will look and feel
the same as those in use today, so they can be used with existing
weapons. Aerojet, the company that builds the rocket boosters for
the U.S. space program, is fabricating the composite munition case.
along with Livermore researchers Estelle McGuire and Jack Reaugh,
is also conducting simulations of the target penetration
and detonation experiments to predict the warheads physical
and timing parameters, such as velocity, pressure, and energy delivery.
The simulations are performed using DYNA2D, CALE, ALE3D, and CHEETAH,
computer simulation programs developed at Livermore. The results
produced by these simulations reflect differences in timing and
behavior between conventional steel-cased, high-explosive munitions
used today and the unique design of the carbon-composite casing
with the enhanced-blast explosive.
Creating Tailored Warheads
Murphy believes that with adequate funding, the new composite-cased
TATB-enhanced-blast munitions can be ready in six months to a year.
The Livermore team is developing munitions for a few specific applications
that have been requested by the Air Force. These munitions can easily
be tailored to other applications as well. If we develop something
that looks interesting, someone will provide the funding for us
to make it. Because of recent military activities in Iraq and Afghanistan,
some of our armament resources are depleted and have to be replenished.
Now is a good time to bring in the newer technology, says
One of the current goals of military operations is achieved through
the ability of U.S. armed forces to reliably hit and destroy their
targets while minimizing collateral damage. In addition to providing
more safety to soldiers and civilians on the ground, the new, low
collateral damage munitions will also minimize the rebuilding that
is needed after a war. The Air ForceNavyLivermore team
is excited about these promising advancements that will bring low
collateral damage munitions to the next generation of armament technology.
Key Words: ALE3D, CALE, carbon composite, CHEETAH, collateral damage,
DYNA2D, HMX, munitions, TATB.
For further information contact Michael Murphy (925) 423-7049
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