Lethality is one of the key concepts of the Army’s plans
for its transformation to the Objective Force of the 21st century.
The idea is certainly not new. The power that an army could bring
to bear on the battlefield always has been the focus of organized
military forces. Often overlooked is the potential lethality that
the individual soldier brings to the battlefield. Part of the transformation
is attempting to change that, as the Army looks for ways to increase
the power of every soldier.
The now-widely accepted systems approach to developing equipment
for the modern soldier, in the land-warrior program, has led to
the development of a new individual weapon. The Objective Individual
Combat Weapon (OICW) will be the lethality element of the land warrior
of the future. Its double barrels—one firing a low-technology,
standard 5.56 mm kinetic-energy round and the other launching a
high-technology, 20 mm air-bursting munition—are intended
to provide the individual soldier with a wider array of lethal options.
Its designers say the OICW is still in the early stages of development,
but many in the small-arms community question the effectiveness
of such a small caliber in an air-bursting munition. If soldiers
were going to deliver an air-bursting munition, how big could it
be before it was too big? If the design was too small, making it
easier to carry more rounds, would it still be lethal?
Part of the answer is found “under the hood,” in the
warhead of the new round. It looks just as it should, a bullet-shaped
warhead with a layer of scored metal inside. Similar to the scoring
found on a “pineapple” hand grenade, the inside of the
20 mm warhead has small, four-sided bumps intended to pre-determine
fragmentation of the round after detonation.
The problem with scoring sheet metal traditionally has been the
unpredictable behavior of that fragmentation. Stamped metal is not
a homogeneous material, which makes it easier to break into multiple,
rather than individual, fragments when the round goes off. This
can lead to unpredictable results.
Working with such a small warhead and the resulting tiny fragments,
Alliant Techsystems had to come up with a design that would guarantee
that each fragment broke away in a specified, predictable pattern
every time. The weapon’s designers have said that getting
the round to the target is the key.
Although the OICW design team at Alliant Techsystems won the competition
to deliver a 20 mm round that meets the Army’s lethality criteria,
many within the small-arms community question whether such tiny
fragments from such a small round can be lethal. The answer is not
only in the composition of the warhead, but in the manufacturing
technology applied to create it.
To reach the desired levels of lethality, the 20 mm air-bursting
warhead did not have to be just precisely on target. Its fragments
had to go through body armor with enough energy left over to penetrate
the person inside that body armor. Alliant Techsystems engineers
decided on a relatively old technology, hot isostatic pressing (HIP),
using metal powder to create a warhead that would be light enough,
yet lethal enough to meet Army requirements.
This process, developed in the 1950s at Battelle Laboratories,
has been used in making nuclear fuel rods and jet-turban vanes.
It makes hard metals harder and denser and improves their fatigue
strength. While the technology is not new, its application to the
warhead design is more recent. This results from a confluence of
other technological improvements, including powder-metallurgy manufacturing
and computer-aided design.
According to engineers from Bodycote IMT, Inc., where the OICW
warhead design was adapted to the HIP process, materials in the
warhead were engineered to withstand the high pressures of the launch
inside the 20 mm chamber of the weapon. Their HIP process also could
make a warhead that would deliver fragments to exacting specifications.
It is a type of casting that uses powder metals, usually steel,
stainless steel, high-speed steel, titanium alloy and refractory
metals.
The casting process begins with a single pellet, which forms the
actual fragment. The second material in the HIP process bonds the
fragments together to form the warhead. Isostatic processing makes
it possible to manufacture that warhead consistently to exact specifications.
The desired flexibility, density, strength, weight, hardness and
fragmentation design help determine the combination of materials
used.
This flexibility, when applying the HIP process, gives ammunition
manufacturers a wide variety of lethal options in warhead design,
with different applications, from anti-personnel to anti-materiel.
In addition to the warhead for the OICW 20 mm round, Bodycote engineers
have designed prototypes for a new warhead for the Stinger shoulder-fired
anti-aircraft missile with high density tungsten pellets embedded
in a titanium matrix. They also have designed a lightweight, controlled
fragmentation hand-grenade body. One of the trade-offs that the
Army will need to determine is the cost-to-lethality ratio.
The cost saving is in the precision of the manufacturing process.
Usually, a rough shape is cast or forged and machined to the finished,
final product. In the case of the HIP process, little machining
is necessary after the original casting is made.
The result is little waste, which saves money especially if the
materials, such as titanium, are expensive. Computer modeling creates
the original shape of the fragment design. This, combined with the
desired lethality, determines the types of metals needed for a specific
mission requirement.
Since its earliest design phase, lethality has been a primary component
of the OICW as the prospective replacement for the traditional individual
infantry weapon. Over the years, it has been assumed that a well-aimed
shot with a good assault rifle was good enough.
The OICW adds high technology to the marksmanship equation, giving
every soldier a greater chance of hitting his target. The design,
materials and especially the manufacturing process of the 20 mm
warhead of the OICW are intended to make him more lethal.