U.S. patent application number 12/272044 was filed with the patent office on 2011-04-28 for forward firing fragmentation warhead.
This patent application is currently assigned to Raythenn Company. Invention is credited to Kim L. Christianson, James H. Dupont, Henri Y. Kim, Travis P. Walter.
Application Number | 20110094408 12/272044 |
Document ID | / |
Family ID | 41264268 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110094408 |
Kind Code |
A1 |
Dupont; James H. ; et
al. |
April 28, 2011 |
FORWARD FIRING FRAGMENTATION WARHEAD
Abstract
A forward firing fragmentation warhead is constructed with
casing materials that are pulverized upon detonation of the
explosive. As a result, the lethality radius of the pulverized case
fragments is no greater than that of the gas blast, thus reducing
potential collateral damage. Warhead lethality may be improved by
forming the fragmentation layer and explosive with dome-shapes that
approximately match the shape of the advancing pressure wave. This
increases fragment velocity and improves the uniformity of the
fragment distribution over the forward-firing pattern. A
variable-thickness pattern shaper may be placed between the
fragmentation layer and explosive to provide additional shaping of
the forward-firing pattern. Warhead weight and cost can be reduced
by eliminating explosive at the aft end of the warhead that does
not contribute to the total energy imparted to the fragments. More
specifically, the aft section of the explosive and explosive
containment structure may be tapered to approximately match the
expansion of the pressure wave from the single-point aft
detonation.
Inventors: |
Dupont; James H.; (Bowie,
AZ) ; Kim; Henri Y.; (Tucson, AZ) ; Walter;
Travis P.; (Tucson, AZ) ; Christianson; Kim L.;
(Oro Valley, AZ) |
Assignee: |
Raythenn Company
|
Family ID: |
41264268 |
Appl. No.: |
12/272044 |
Filed: |
November 17, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12123158 |
May 19, 2008 |
|
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12272044 |
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Current U.S.
Class: |
102/492 |
Current CPC
Class: |
F42B 1/028 20130101;
F42B 12/32 20130101; F42B 1/024 20130101 |
Class at
Publication: |
102/492 |
International
Class: |
F42B 12/32 20060101
F42B012/32; F42B 1/024 20060101 F42B001/024; F42B 12/22 20060101
F42B012/22; F42B 12/10 20060101 F42B012/10 |
Claims
1. A forward firing warhead, comprising: a case; an explosive
containment structure inside the case, said case and containment
structure formed of materials that are pulverized upon detonation
eliminating metal fragments thrown radially from the warhead; an
explosive in the explosive containment structure that is in
conformal contact with an inner surface of the containment
structure, said explosive having a dome-shaped forward section; an
initiator aft of the explosive to initiate detonation of the
explosive to produce a pressure wave; and a forward-firing
fragmentation assembly including a dome-shaped fragmentation layer
positioned forward of the explosive, the curvature of said
dome-shaped fragmentation layer approximately conforming to the
shape of the front of the pressure wave that reaches the
fragmentation assembly to expel fragments in a forward-firing
pattern.
2. The forward firing warhead of claim 1, wherein said
fragmentation layer comprises pre-formed fragments.
3. The forward warhead of claim 2, wherein the forward-firing
fragmentation assembly comprises: a containment ring around the
periphery and aft of said dome-shaped layer.
4. The forward warhead of claim 3, wherein the containment ring
overlaps at least an aft portion of the dome-shaped layer.
5. The forward warhead of claim 2, further comprising a
variable-thickness pattern shaper between and in conformal contact
with the dome-shaped fragmentation layer and the dome-shaped
forward section of the explosive, said pattern shaper shaping the
front of the pressure wave as it propagates through the pattern
shaper.
6. The forward warhead of claim 5, wherein the pattern shaper is
thicker in a central region than in a peripheral region to slow the
central region of the pressure wave relative to the peripheral
region.
7. (canceled)
8. The forward warhead of claim 1, wherein said containment
structure and explosive have a forward section with a diameter
conformal with said case and have a tapered aft section that tapers
to a reduced diameter to define a tapered void space between the
case and the containment structure, said initiator positioned aft
of the explosive to initiate detonation of the explosive at the end
of the taper.
9. The forward warhead of claim 8, wherein detonation of the
explosive produces a pressure wave that propagates forward through
the tapered explosive to expel the fragments in the forward-firing
pattern, wherein the taper is optimized to maximize the void space
without reducing the total explosive energy imparted to the
fragmentation layer.
10. The forward firing warhead of claim 8, further comprising a
base plate aft of the explosive.
11. The forward firing warhead of claim 1, wherein said pulverized
case material has a mass efficiency no greater than 1%, said
expelled fragments from said forward-firing fragmentation assembly
has a mass efficiency of at least 70%.
12. The forward firing warhead of claim 1, wherein said
forward-firing fragmentation assembly expels fragments in said
forward-firing pattern in a half-angle of between 3 and 45 degrees
about a long axis of the warhead.
13. The forward firing warhead of claim 1, wherein the pulverized
case material has a lethality radius to humans no greater than the
lethality radius due to the gas blast of the explosive.
14. A forward firing warhead, comprising: a case having a forward
section with an opening; an explosive containment structure inside
the case, said containment structure having a forward section with
a diameter conformal with said forward section of the case and
having a tapered aft section that tapers to a reduced diameter to
define a tapered void space between the case and the containment
structure, said case and containment structure formed of materials
that are pulverized upon detonation with a mass efficiency no
greater than 1%; an explosive in the explosive containment
structure, said explosive having a dome-shaped end, a forward
section with a diameter in conformal contact with an inner surface
of said containment structure and an aft section that tapers to
said reduced diameter in conformal contact with the inner surface
of said containment structure eliminating metal fragments thrown
radially from the forward section of the warhead; an initiator aft
of the explosive to initiate detonation of the explosive at the end
of the taper to produce a pressure wave; and a forward-firing
fragmentation assembly including a dome-shaped layer of pre-formed
fragments positioned in the opening forward of the explosive and at
least approximately conformal with the dome-shape end of the
explosive, the curvature of said dome-shape layer approximately
conforming to the shape of the front of the pressure wave that
reaches the fragmentation to expel said pre-formed fragments in a
forward-firing pattern with a mass efficiency of at least 70% upon
detonation of the explosive.
15. The forward warhead of claim 14, wherein the pressure wave
propagates forward through the tapered explosive to expel the
pre-formed fragments in the forward-firing pattern, wherein the
taper is optimized to maximize the void space without reducing the
total explosive energy imparted to the dome-shaped layer of
pre-formed fragments.
16. (canceled)
17. (canceled)
18. A forward firing warhead, comprising: a case; an explosive in
the case; an initiator to initiate detonation of the explosive to
produce a pressure wave; and a forward-firing fragmentation
assembly including a dome-shaped fragmentation layer positioned
forward of the explosive, the curvature of said dome-shaped
fragmentation layer approximately conforming to the shape of the
front of the pressure wave that reaches the fragmentation assembly
to expel fragments in a forward-firing pattern.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of priority under 35 U.S.C.
120 as a continuation-in-part of co-pending U.S. Utility
application Ser. No. 12/123,158 entitled "High-Lethality Low
Collateral Damage Fragmentation Warhead" and filed on May 19, 2008,
the entire contents of which are incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to fragmentation warheads and in
particular to a forward firing fragmentation warhead that expels a
mass of fragments in a forward-firing pattern.
[0004] 2. Description of the Related Art
[0005] Fragmentation warheads expel metal fragments upon detonation
of an explosive. Fragmentation warheads are used as offensive
weapons or as countermeasures to anti-personnel or anti-property
weapons such as rocket-propelled grenades. The warheads may be
launched from ground, sea or airborne platforms. A typical warhead
includes an explosive inside a steel case. A booster explosive and
safe and arm device are positioned in the case to detonate the
explosive.
[0006] A radial blast fragmentation warhead includes a steel case
that has been pre-cut or scored along the length of the explosive.
The booster explosive is positioned in a center section of the
case. Detonation of the explosive produces a gas blast that
emanates radially from the center point pulverizing the case and
expelling the pre-cut metal fragments in all directions in a
generally spherical pattern. Although lethal, the radial
distribution of the fragments also presents the potential for
collateral damage to friendly troops and the launch platform.
[0007] A forward blast fragmentation warhead includes a
fragmentation assembly placed in an opening in a fore section of
the steel case against the flat leading surface of the explosive.
The fragmentation assembly will typically include `scored` metal or
individual pre-formed fragments such as spheres or cubes to control
the size and shape of the fragments so that the fragments are
expelled in a somewhat predictable pattern and speed. Scored metal
produces about an 80% mass efficiency while individual fragments
are expelled with mass efficiency approaching 100% where mass
efficiency is defined as the ratio of fragment mass expelled
(therefore effective against the intended target) to the total
fragment mass. In other words, the mass efficiency is the ratio of
the total mass less the interstitial mass that was consumed during
the launch process (therefore ineffective against the intended
target) to the total mass.
[0008] In the forward blast warhead the booster explosive is
positioned in an aft section of the case. The steel case confines a
portion of the radial energy of the pressure wave (albeit for a
very short duration) caused by detonation of the explosive and
redirects it along the body axis of the warhead to increase the
force of the blast that propels the metal fragments forward with a
lethality radius. The lethality radius is defined as the radius of
a virtual circle composed of the sum of all lethal areas (zones)
meeting a minimum lethal threshold for a specified threat. These
fragments are generally expelled in a forward cone towards the
intended target. The density of fragments per unit area is maximum
near zero degrees and falls off with increasing angle with tails
that extend well beyond the desired cone. As a result, the warhead
has a maximum lethality confined to a very narrow angle and expels
a certain amount of lethal fragments outside the desired target
area that may cause collateral damage. As a result, the aimpoint
and detonation timing tolerances to engage and destroy the threat
while minimizing collateral damage are tight.
[0009] Detonation of the high explosive produces a gas blast that
has a much smaller lethality radius in all directions caused by the
pressure wave of the blast. The detonation also tears the steel
case into metal fragments of various shapes and sizes that are
thrown in all directions, beyond the lethality radius of the gas
blast. Detonation of the steel case increases the potential for
collateral damage to friendly troops and the launch platform.
SUMMARY OF THE INVENTION
[0010] The present invention provides a forward firing
fragmentation warhead that provides threat lethality and reduced
collateral damage.
[0011] In an embodiment, the warhead includes an explosive
containment structure inside a case. An explosive is placed in the
containment structure and an initiator is placed aft of the
explosive. Both the case and containment structure are formed of
materials that are pulverized upon detonation of the explosive. A
forward-firing fragmentation assembly is positioned forward of the
explosive to expel fragments in a forward-firing pattern upon
detonation of the explosive.
[0012] In another embodiment, the warhead includes an explosive
containment structure inside a case. An explosive is placed in the
containment structure and an initiator is placed aft of the
explosive. Both the case and containment structure are formed of
materials that are pulverized upon detonation of the explosive. A
forward-firing fragmentation assembly is positioned forward of the
explosive to expel fragments in a forward-firing pattern upon
detonation of the explosive. The fragmentation assembly includes a
dome-shaped layer of fragments that is at least approximately
conformal with a dome-shaped forward end of the explosive. A
pattern shaper may be inserted between the fragmentation layer and
the explosive, otherwise they would be conformal. The dome-shape is
approximately matched to the shape of the front of the pressure
wave that reaches the fragmentation assembly upon detonation. This
increases fragment velocity and expels the fragments in a more
uniform pattern.
[0013] In another embodiment, the warhead includes an explosive
containment structure inside a case. The containment structure has
a forward section with a diameter conformal with the forward
section of the case and has a tapered aft section that tapers to a
reduced diameter to define a tapered void space between the case
and the containment structure. An explosive is placed in the
containment structure and an initiator is placed aft of the
explosive. Both the case and containment structure are formed of
materials that are pulverized upon detonation of the explosive. A
forward-firing fragmentation assembly is positioned forward of the
explosive to expel fragments in a forward-firing pattern upon
detonation of the explosive. Upon detonation a pressure wave
propagates forward through the tapered explosive to the diameter of
the case. The taper may be optimized to match the expansion of the
pressure wave thereby maximizing the void space without reducing
the total explosive energy imparted to the fragmentation assembly.
The elimination of explosive reduces both the cost and weight of
the warhead.
[0014] These and other features and advantages of the invention
will be apparent to those skilled in the art from the following
detailed description of preferred embodiments, taken together with
the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a diagram illustrating the blast pattern of the
forward firing warhead to engage a threat without collateral damage
to friendly troops;
[0016] FIGS. 2a and 2b are diagrams of a section and exploded view
and a bottom view of the warhead;
[0017] FIGS. 3a through 3c are plots of the gas blast propagation
to expel the fragments in the forward-firing pattern; and
[0018] FIGS. 4 and 5 are diagrams of embodiments of the
forward-firing fragmentation assembly including an extended
containment ring and pattern shaper, respectively, to control the
half-angle of the forward-firing pattern;
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention describes a high-lethality low
collateral damage forward firing fragmentation warhead. The
reduction in collateral damage is accomplished by forming the case
of a material that is pulverized upon detonation of the explosive.
As a result, the lethality radius of the pulverized case fragments
is no greater than that of the gas blast, thus reducing potential
collateral damage. Warhead lethality may be improved by forming the
fragmentation layer and explosive with a dome-shape that
approximately matches the shape of the front of the pressure wave.
This increases fragment velocity and improves the uniformity of the
fragment distribution over the forward-firing pattern. A
variable-thickness pattern shaper may be placed between the
fragmentation layer and explosive to provide additional shaping of
the forward-firing pattern. Warhead weight and cost can be reduced
by eliminating explosive at the aft end of the warhead that does
not contribute to the total energy imparted to the fragments. More
specifically, the aft section of the explosive and explosive
containment structure may be tapered to approximately match the
expansion of the pressure wave from the single-point aft
detonation.
[0020] The forward firing fragmentation warhead was developed as a
short-range, low-speed countermeasure for land-based launch
platforms (e.g. tanks or personnel carriers) to intercept and
destroy threats such as rocket-propelled grenades (RPGs) while
minimizing the risk of collateral damage to friendly troops. The
fragmentation warhead is however adaptable to a wide-range of
battle field scenarios to include any type of land, sea, air or
spaced-based launch platforms and longer-range, higher-speed
engagements. The warhead may be configured for use as an offensive
weapon or for countermeasures.
[0021] The fragmentation warhead can be used in conjunction with a
wide range of interceptors including projectiles and self-propelled
missiles and spinning or non-spinning and with various guidance
systems. The aiming and detonation sequence may be computed and
loaded into the interceptor prior to firing. For example, in a
close-range countermeasure system, the fire control computer will
determine when to fire a sequence of motors on the interceptor and
when to detonate the warhead. This sequence is loaded into the
interceptor prior to launch. A more sophisticated longer range
missile might fly to a target and compute its own aiming and
detonation sequences or have those sequences downloaded during
flight.
[0022] As shown in FIG. 1 of an exemplary countermeasures system,
an interceptor 10 including a fragmentation warhead 12 having a
fragmentation assembly 13 is fired to engage and destroy a threat
depicted as a rocket-propelled grenade 14 in close proximity to
friendly troops 16. The warhead must destroy the threat with a high
likelihood of success and minimize the threat of collateral damage
to the troops or, more generally, to any person or object other
than the engaged threat. The aiming and detonation sequence are
loaded into the interceptor and is fired at threat 14. The warhead
is detonated at a standoff distance 17 to expel metal fragments 20
from fragmentation assembly 13 in a prescribed half-angle 22 of a
forward-firing pattern to destroy the threat. The forward-firing
pattern suitably occupies a half-angle of between 3 and 45 degrees
about a long axis of the warhead.
[0023] The threat detection, guidance, navigation and control
systems are input to the fire control computer generate a firing
solution to destroy the threat. That solution has a composite
system error which means there is an aiming error that can be
translated into an area or volume. The area or volume of the cone
is typically 100 to 1,000 times larger than the presented area of
the target. The fragmentation warhead must engage the entire area
or volume with lethal force to destroy the threat. The area or
volume and the lethality requirement per threat determine the
number of fragments that must be expelled. Typically the threat can
be in any place within the volume with equal probability. In this
case, the fragmentation warhead is suitably designed to expel metal
fragments having a somewhat uniform pattern density (# fragments
per unit area) over the prescribed solid angle of the volume and
preferably no further.
[0024] To accomplish the dual objectives of improved lethality and
reduced collateral damage, the end of the explosive and the
fragmentation assembly 13 are suitably formed with largely
conformal dome shapes that approximately match the shape of the
advancing pressure wave. This both increases the amount of
explosive energy delivered to those fragments to increase their
velocity and serves to expel them in a desirable pattern (e.g.
half-angle and uniformity of fragment density over the half-angle).
A variable-thickness pattern shaper may be inserted between the
explosive and fragment layer to slow portions of the wave front to
further shape the forward-firing pattern. The case 18 is formed of
a material such as a fiber reinforced composite, engineered wood,
thermoplastic (resin, polymer), or even foam that is pulverized
into a cloud 23 of harmless fine particles 24 upon detonation of
the explosive. The particles preferably have a mass efficiency near
0% and no greater than 1% so that the lethality radius of the
expelled particles 24 is no greater than the lethality radius of
the gas blast from the detonating explosives. Consequently, the
threat to the soldiers on either side of the warhead is reduced to
the threat posed by the gas blast. For typical countermeasure sized
warheads this is a couple meters. Additionally, warhead weight and
cost can be reduced by eliminating explosive at the aft end of the
warhead that does not contribute to the total energy imparted to
the fragments. More specifically, the aft section of the explosive
and explosive containment structure may be tapered to approximately
match the expansion of the pressure wave from the single-point aft
detonation.
[0025] As shown in FIGS. 2a and 2b, an embodiment of forward firing
warhead 12 includes an explosive containment structure 30 placed
inside a case 32. A tapered aft section 34 of the containment
structure defines a tapered void space 36 between the case and the
containment structure. An explosive 38 having a fore section with a
diameter conformal with the case and a dome-shape end 40 and a
tapered aft section 42 is fit inside the containment structure. The
dome-shaped end 40 of the explosive suitably extends beyond an
opening in the containment structure and case. An initiator 44 (a
small booster charge) placed aft of the explosive initiates
detonation of the explosive at the end of the taper. This type of
single-point detonation is typical for these types of warheads.
Other multi-point configurations may be used. A safe and arm device
46 is positioned to ignite the booster when commanded. The
containment structure and case are formed of materials such as a
fiber reinforced composite, engineered wood, thermoplastic (resin,
polymer), or even foam that are pulverized with a mass efficiency
suitably no greater than 1% upon detonation of the explosive. As a
result, the pulverized case material suitably has a lethality
radius to humans no greater than the lethality radius due to the
pressure wave of the detonated explosive.
[0026] A forward-firing fragmentation assembly 50 is positioned in
the opening around the dome-shaped end of the explosive. The
assembly suitably includes a dome-shaped layer 52 of metal
fragments 54 that are expelled in the forward-firing pattern with a
mass efficiency of at least 70% upon detonation of the explosive.
Pre-formed fragments are generally preferred because they have a
known size and shape upon detonation and retain a mass efficiency
near 100%. The fragments may be shaped (rectangular, square or
other unique shapes) for a particular threat. For ease of assembly
the fragments are typically formed in a mold held by an epoxy that
is pulverized on detonation.
[0027] In a forward firing fragmentation assembly, the warhead and
fragmentation assembly are preferably configured to control the
velocity of the expelled fragments, the half-angle of the pattern
and the uniformity of the density of the expelled fragments over
the half-angle. In the forward-firing fragmentation assembly 50 the
provision of a dome-shaped explosive 38 and a dome-shaped layer 52
of fragments effectively addresses all three parameters. First, in
a conventional warhead of this type an aerodynamic nose cone is
placed over the flat leading surface of the warhead to provide
aerodynamic stability. At typical velocities for short-range
countermeasures, a semi-blunt or dome shape is used. In this
embodiment, the explosive is extended to fill the dead space and
the conformal fragment layer provides the aerodynamic surface. The
additional explosive volume upon detonation imparts greater total
energy to the fragments thereby increasing their velocity. Second,
as the simulation results will show the curvature of the dome is
suitably selected to approximately match the shape of the pressure
wave. As a result, the metal fragments are expelled in a
well-defined cone with improved density uniformity. In higher
velocity warheads, the explosive and fragmentation layer may be
shaped to match the front of the pressure wave and a more pointed
aerodynamic nose cone place over the warhead for aerodynamic
considerations.
[0028] A containment ring 56 may be placed around the periphery and
aft of the dome-shaped layer. This ring provides a degree of
confinement of the pressure wave to direct fragments axially
instead of radially. The ring contains the explosive blast
momentarily (e.g. a few microseconds) but long enough to direct the
pressure wave in a forward direction before the ring is itself
pulverized. The ring contributes to reducing or eliminating any
tails of the pattern beyond the prescribed half-angle. The ring may
be extended forward to provide additional confinement to narrow the
half-angle as desired. The ring could be extended to span the
entire length of the case. A variable-thickness pattern shaper may
be inserted between the explosive and fragment layer to slow
portions of the wave front to further shape the forward-firing
pattern. A base plate 66 may be placed between the assembly and the
safe and arm device to reflect the energy of the pressure wave
forward.
[0029] One might assume that the removal of a portion of explosive
38 to create the tapered void space would reduce the total energy
imparted to the forward-firing fragmentation assembly and degrade
the lethality of the weapon. However, as the simulations will
demonstrate, for an L/D (length/diameter) optimized forward-firing
aft-initiated warhead a tapered aft portion of the explosive
represents "dead" volumetric space. In other words, explosive in
that space does not contribute to the total energy in the forward
propagating wave. Essentially the single-point detonation expands
as the pressure wave moves forward until it fills the diameter of
the casing. Suitably, the taper of the containment structure and
explosive are optimized for a given warhead to maximize the tapered
void space without reducing the total energy in the forward
propagating pressure wave. Warhead weight and cost is reduced by
eliminating explosive at the aft end of the warhead that does not
contribute to the total energy imparted to the fragments. Tapering
of the aft section of the explosives is however optional, a
conventional cylindrical design may be used with the dome-shaped
fragmentation assembly.
[0030] In warhead analysis, the detonation pressure wave is
simulated using CTH analysis models. FIGS. 3a through 3c show the
detonation pressure wave 70 from detonation of an explosive 71
through expulsion of the metal fragments in the forward-firing
pattern. The CTH analysis models a forward firing warhead 72 that
includes a dome-shaped layer 74 of pre-formed fragments and an aft
tapered void space 76. The curvature of the dome-shaped layer
conforms to the front 77 of the pressure wave. A base plate 78 is
positioned aft and a containment ring 80 is around the periphery of
the dome-shaped layer. The design of the explosive is optimized to
a warhead's length to diameter ratio. In this case L/D=1 and the
taper is 45 degrees. For a forward firing warhead, increasing the
length much beyond an L/D of 1 (i.e. L/D>1) produces only
incremental improvements in the fragment velocity or warhead
lethality against the threat. However, should the L/D be >1, the
taper angle can be increased to optimize for an explosive length of
1 (or L/D of 1), thus reducing the explosive content for cases
where L/D>1.
[0031] As shown in FIG. 3a at t.apprxeq.2 microseconds, the front
77 of pressure wave 70 moves forward from the single initiation
point through the taper and expands to fill the taper as it
advances. The highest pressure exists at the wave front 77. The
pressure in the aft section is much lower.
[0032] As shown in FIG. 3b at t.apprxeq.8 microseconds, the front
77 of pressure wave 70 has expanded to the diameter of the
explosive at the opposing end of the taper.
[0033] As shown in FIG. 3c at t.apprxeq.14 microseconds, the high
pressure wave front 77 has reached the dome-shaped layer 74. The
shape of the wave front substantially conforms to the shape of the
layer. Containment ring 80 momentarily confines the pressure wave
in region 82 thereby directing the pressure wave forward. At this
point, the casing materials have begun to pulverize and the
forward-firing fragment layer 74 will be expelled
instantaneously.
[0034] The CTH analysis models clearly demonstrates (a) that the
proper tapering of the explosive and containment structure to
create the void space does not degrade the forward energy of the
pressure wave and (b) that conforming the shape of the
forward-firing fragmentation layer and explosive to the shape of
the pressure wave front increases fragment velocity and pattern
uniformity. Other warhead configurations and configurations of the
forward firing fragmentation assembly may be employed within the
scope of the forward firing warhead architecture.
[0035] Different embodiments of the forward-firing fragmentation
assembly are depicted in FIGS. 4 through 5. As shown in FIG. 4, the
length of containment ring 56 is extended forward to overlap a
portion of dome-shaped layer 52. In this configuration, the
configuration ring will contain the pressure wave, directing the
front of the wave in the forward direction thereby reducing the
half-angle of the forward firing pattern.
[0036] A shown in FIG. 5, a variable-thickness pattern shaper 110
is placed between the end 40 of explosive 38 and dome-shaped layer
52 to augment the pattern shaping. Note, in this particular
embodiment the dome-shaped end 40 of explosive 38 is flattened in
the center 112 and only approximately conformal with dome-shaped
layer 52. The pattern shaper 110 is conformal with the dome-shaped
layer. The explosive is still considered to have a "dome-shape". As
the pressure wave reaches pattern shaper 110 it travels relatively
faster in the peripheral regions 114 and 118 on either side of the
center 112 because explosive 38 continues to detonate. Once the
wave goes through the thickest part of the pattern shaper it slows
down more than the wave going through the thinnest part. The result
is that the pattern shaper slows down the center fragments and
focuses the fragments, more in a straight line. How much the wave
slows down is dictated by the shock impedance of the shaper
material which is a function of the material's density and the
speed of sound in the material and the thickness of the pattern
shaper. Lower density materials such as composites are generally
preferred because they absorb less energy. However, higher density
materials can have a smaller volume leaving more space for
explosive. The range of materials suitable for the shaper includes
fiber reinforced composites, thermoplastic (resin, polymer), nylon,
rubber, stereolithographic (SL) materials, structural foams, and
metals. The only qualification is that it be either castable or
machinable. In general, we want to minimize or even eliminate any
material between the explosive and the fragmentation layer to
maximize the energy imparted to the fragments. However, in some
cases the pattern shaper may provide the optimal balance of pattern
shape and uniformity with velocity. Other shapes and designs of the
variable-thickness pattern shaper are possible to achieve different
patterns and to address different threat scenarios.
[0037] While several illustrative embodiments of the invention have
been shown and described, numerous variations and alternate
embodiments will occur to those skilled in the art. Such variations
and alternate embodiments are contemplated, and can be made without
departing from the spirit and scope of the invention as defined in
the appended claims.
* * * * *