U.S. patent application number 14/337634 was filed with the patent office on 2016-01-28 for low-collateral damage directed fragmentation munition.
The applicant listed for this patent is Raytheon Company. Invention is credited to Brian S. Botthof, Kim L. Christianson, Garrett L. Hall, Henri Y. Kim.
Application Number | 20160025468 14/337634 |
Document ID | / |
Family ID | 55166499 |
Filed Date | 2016-01-28 |
United States Patent
Application |
20160025468 |
Kind Code |
A1 |
Botthof; Brian S. ; et
al. |
January 28, 2016 |
LOW-COLLATERAL DAMAGE DIRECTED FRAGMENTATION MUNITION
Abstract
A directed munition has a non-fragmentation casing, and an
explosive within the casing that is configured to propel fragments
out an opening of the casing when the explosive is detonated. The
casing may be made of a material that does not produce lethal or
injurious fragments when the explosive is detonated. The explosive
may include an insensitive explosive portion that creates the shape
of an explosive front, and a secondary explosive containing a more
energetic explosive, which is closer to the fragments than the
insensitive explosive portion. There may be more of the insensitive
explosive than the relatively energetic explosive.
Inventors: |
Botthof; Brian S.; (Vail,
AZ) ; Christianson; Kim L.; (Oro Valley, AZ) ;
Kim; Henri Y.; (Tucson, AZ) ; Hall; Garrett L.;
(Tucson, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Raytheon Company |
Waltham |
OH |
US |
|
|
Family ID: |
55166499 |
Appl. No.: |
14/337634 |
Filed: |
July 22, 2014 |
Current U.S.
Class: |
102/475 |
Current CPC
Class: |
F42B 12/207 20130101;
F42B 12/76 20130101; F42B 12/22 20130101; F42B 12/32 20130101; F42B
1/02 20130101; F42B 12/24 20130101 |
International
Class: |
F42B 12/32 20060101
F42B012/32; F42B 12/20 20060101 F42B012/20 |
Claims
1. A directed munition comprising: a casing; an explosive within
the casing; and fragments operatively coupled to the explosive, to
be directed out of a front opening of the casing when the explosive
is detonated; wherein the explosive includes an insensitive
explosive portion containing an insensitive explosive, and an
energetic explosive portion that contains a relatively sensitive
explosive that is more energetic than the insensitive explosive;
and wherein the energetic explosive portion is closer to the
fragments than the insensitive explosive portion.
2. The directed munition of claim 1, wherein the insensitive
explosive portion has a larger circumferential surface area than
the energetic explosive portion.
3. The directed munition of claim 1, wherein at least part of the
explosive has a conical shape, with a wider end of the explosive
that is part of the energetic explosive portion, facing toward the
opening of the casing.
4. The directed munition of claim 3, wherein the insensitive
explosive has a conical shape.
5. The directed munition of claim 3, wherein the energetic
explosive portion has a disk shape.
6. The directed munition of claim 1, wherein the insensitive
explosive has a figure of insensitivity that is less than the
figure of insensitivity of the relatively energetic explosive.
7. The directed munition of claim 1, wherein the casing is a
non-fragmentation casing that is mostly pulverized upon detonation
of the explosive.
8. The directed munition of claim 7, wherein the casing is made of
a plastic material.
9. The directed munition of claim 7, wherein the casing is made of
a composite material.
10. The directed munition of claim 1, further comprising a ring at
least partially within the casing; wherein the ring is operatively
coupled to the fragments to control spread of the fragments out of
the opening, when the explosive is detonated.
11. The directed munition of claim 1, further comprising a fragment
liner between the energetic explosive portion and the
fragments.
12. The directed munition of claim 1, further comprising a
detonator operatively coupled to the insensitive explosive portion,
to detonate the insensitive explosive portion as a primary
explosive.
Description
FIELD OF THE INVENTION
[0001] The invention relates to fragmentation munitions and
warheads.
DESCRIPTION OF THE RELATED ART
[0002] 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. A typical warhead
includes an explosive inside a steel case. A booster explosive and
safe and arm device are positioned in an aft section of the case to
detonate the main explosive. A fragmentation assembly is placed in
an opening in a fore section of the case against the flat leading
surface of the explosive. The fragmentation assembly will typically
include scored metal or individual fragments (pre-formed) such as
spheres or cubes to control the size and shape of the fragments so
that the fragments are expelled in a 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.
[0003] 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 of, for example,
25-50 meters. 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 example, the lethality
threshold may occur when 1% of people at that radius are killed.
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. This means that the
aimpoint and detonation timing tolerances to engage and destroy the
threat while minimizing collateral damage are tight.
[0004] Detonation of the high explosive produces a blast that has a
much smaller lethality radius, maybe 3 meters in this example, in
all directions caused by the pressure wave of the blast. The
detonation and subsequent expansion also fractures the steel case
into metal fragments of various shapes and sizes that are thrown in
all directions, beyond the lethality radius of the blast. In this
example, the expelled metal fragments from the case may have a
lethality radius of 5-8 meters. Fragmentation of the steel case
increases the potential for collateral damage without improving the
lethality of the warhead to destroy the threat.
[0005] One approach to this problem has been to replace the steel
case with a casing that is pulverized into fine particles upon
detonation, as described in U.S. Patent Publication 2011/0146523
A1, in conjunction with use of a metal ring and a pattern shaper.
However this approach does not fully address the problems of
producing a desired spread of fragments while reducing potential
collateral damage from the munition.
SUMMARY OF THE INVENTION
[0006] According to an aspect of the invention, a directed munition
includes: a casing; an explosive within the casing; and fragments
operatively coupled to the explosive, to be directed out of a front
opening of the casing when the explosive is detonated. The
explosive includes an insensitive explosive portion containing an
insensitive explosive, and an energetic explosive portion that
contains a relatively sensitive explosive that is more energetic
than the insensitive explosive. The energetic explosive portion is
closer to the fragments than the insensitive explosive portion.
[0007] To the accomplishment of the foregoing and related ends, the
invention comprises the features hereinafter fully described and
particularly pointed out in the claims. The following description
and the annexed drawings set forth in detail certain illustrative
embodiments of the invention. These embodiments are indicative,
however, of but a few of the various ways in which the principles
of the invention may be employed. Other objects, advantages and
novel features of the invention will become apparent from the
following detailed description of the invention when considered in
conjunction with the drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0008] The annexed drawings, which are not necessarily to scale,
show various aspects of the invention.
[0009] FIG. 1 is an oblique view of a munition in accordance with
an embodiment of the present invention.
[0010] FIG. 2 is a side sectional view of the munition of FIG.
1.
[0011] FIG. 3 is an illustration showing effects of detonation of
the munition of FIG. 1.
DETAILED DESCRIPTION
[0012] A directed munition has a non-fragmentation casing, and an
explosive within the casing that is configured to propel fragments
out an opening of the casing when the explosive is detonated. The
casing may be made of plastic or a composite material, or another
low density material that does not produce lethal or injurious
fragments when the explosive is detonated. The explosive may
include an insensitive explosive portion that creates the shape of
an explosive front, and a secondary explosive containing a more
energetic explosive, which is closer to the fragments than the
insensitive explosive portion. There may be more of the insensitive
explosive than the relatively energetic explosive, with the
insensitive explosive for example constituting a majority of the
circumferential surface area of the explosive.
[0013] FIGS. 1 and 2 show a munition 10 that uses an explosive 12
to direct fragments 14 out of an opening 16 in the front of a
casing 20 that encloses the explosive 12 and the fragments 14. The
munition 10 that is shown in FIG. 1 may be a warhead that is part
of an interceptor that is fired to engage and destroy an incoming
threat, such as a rocket-propelled grenade. The explosive 12 is in
two parts or portions, an insensitive explosive portion 22 and an
energetic explosive portion 24. The insensitive explosive portion
22 contains an insensitive explosive, a term which is used herein
to refer to explosives that are chemically stable enough to
withstand mechanical shocks such as impacts (for example from
bullets, explosive-driven fragments, or shrapnel) without inducing
an undesired reaction. The insensitive explosive portion 22 acts as
a primary explosive, with detonation of the insensitive explosive
initiated by a booster 28. The booster or detonator 28 is at one
end of the explosive 12, on the opposite end of the casing 20 from
the fragments 14 and the opening 16. Firing of the booster or
detonator 28 may be initiated by a suitable device, perhaps
including a suitable safe-and-arm mechanism. The detonation of the
insensitive explosive portion 22 creates the shape of the
detonation front, which propagates toward the energetic explosive
portion 24. The munition 10 may be axisymmetric about a
longitudinal axis 30.
[0014] The energetic explosive portion 24 contains a relatively
energetic explosive material that is more energetic than the
insensitive explosive material of the portion 22, and that has a
faster detonation propagation speed than the insensitive explosive.
The insensitive explosive of the portion 22 has a figure of
insensitivity that is less than the figure of insensitivity of the
relatively energetic explosive material of the energetic explosive
portion 24. A sensitive explosive is such that its response to
shock or thermal stimulus is violent, for example detonation. The
energetic explosive portion 24 is a secondary explosive that is
detonated by the primary explosive, the insensitive explosive
portion 22. The faster detonation propagation speed in the
energetic explosive portion 24 acts to expel the fragments 14 with
great speed out of the casing opening 16.
[0015] The two-part explosive 12 provides good performance, with
the fragments 14 expelled with sufficient force (at sufficient
speed) to do damage, while still providing a munition that is safe
to handle and use. Since most of the explosive 12 is insensitive to
detonation from bullets or other impacts, the munition 10 is less
likely to be detonated before firing than munitions with only
energetic explosives. Thus the munition 10 provides improved
safety, especially when being carried in combat by or near friendly
personnel that could be injured by undesired detonation of the
munition 10.
[0016] The explosive materials in the explosive 12 may be any of a
variety of suitable explosive materials. For example, the
insensitive explosive for the insensitive explosive portion 22 may
be PBXN-9 explosive, and the more energetic explosive for the
energetic explosive portion 24 may be PBXN-5, PBXN-11, Octol, or
LX-14 explosives. The listed explosives are only examples, and many
other explosives may be used as alternatives, or in addition to
those listed above.
[0017] The insensitive explosive portion 22 may make up the bulk of
the explosive 12, for example providing a majority of the volume of
the explosive 12, with the insensitive explosive portion 22 having
a greater volume than the energetic explosive portion 24. By having
a significant volume of the explosive 12 taken up by the
insensitive explosive portion 22, the likelihood of detonation from
a stray bullet or other impact is reduced. This makes the munition
10 safer to handle, both before and during combat, than it would be
if all of the explosive was of a more energetic material.
[0018] Alternatively or in addition, a surface area of a
circumferential surface of the insensitive explosive portion 22
(the conical outer surface of the portion 22) may be greater than a
surface area of a circumferential surface of the energetic
explosive portion 24 (the conical outer surface of the portion 24).
The reduction of the side area of the most volatile portion of the
explosive 12 reduces the chance of undesired reaction of the
explosive 12.
[0019] The explosive 12 have a generally conical shape, with the
insensitive explosive portion 22 at the narrow end of the conical
shape, and the energetic explosive portion 24 at the wider end of
the conical shape. The wider end of the explosive 12, part of the
energetic explosive portion 24, faces toward the fragments 14 and
the casing opening 16. In the illustrated embodiment the
insensitive explosive portion 22 has a conical shape, and the
energetic explosive portion 24 has a disk shape. Alternatively the
explosive 12 may have a different shape, such as a being a right
circular cylinder.
[0020] A ring 44, such as a metal ring similar to that shown in
U.S. Patent Publication 2011/0146523 A1, may optionally be added
wholly or partly within the casing 20, for instance encircling part
of the explosive 12. Such a ring may, if present, aid in directing
the fragments 14 out of the opening, in a desired spread. The ring
44 may be omitted entirely.
[0021] A fragment liner 40 may be located between the explosive 12
and the fragments 14. The fragment liner 40 helps in supporting the
fragments 14 and in containing the high-pressure detonation product
produced by the explosive 12, to ensure that the high pressure is
confined to maximize the velocity of the expelled fragments. The
liner 40 may also maintain the fragments 14 in place, for example
by having the fragments 14 adhered to the liner 40, such as by use
of RTV silicone or another suitable adhesive. The fragment liner 40
also may reduce the chance of spalling of the fragments 14. The
fragment liner 40 may be made of aluminum or another suitable
material.
[0022] A retainer 46 may be used to keep the fragments 14 and other
parts of the munition 10 in place in the casing 20 prior to the
detonation of the explosive 12. The retainer 46 may be a ring of
lightweight material, such as suitable plastic. A lightweight
covering 48 (not shown in FIG. 1) may be used to prevent ingress of
moisture and/or other impurities into the casing 20.
[0023] The fragments 14 may be in any of a variety of suitable
shapes, such as cubes and/or spheres. The fragments 14 may be made
a heavy metal, such as a tungsten alloy, or other suitable
materials, such as steel or other metals. Weight of each of the
fragments 14 may be from 0.5 grams to 10 grams, to give a
non-limiting range.
[0024] The casing 20 may be made of a material that is mostly (or
substantially all) pulverized or otherwise reduced to non-lethal
fragments by the detonation of the explosive 12. The casing 20 may
be formed of a material such as a fiber reinforced composite,
engineered wood, thermoplastic (resin, polymer), or even a foam
that may be pulverized into a cloud of harmless fine particles upon
detonation of the explosive. Another alternative material for the
casing 20 is a suitable plastic. The particles produced in the
explosion have a mass efficiency near 0% and no greater than 1%, so
that the lethality radius of the expelled particles is no greater
than the lethality radius of the blast from the detonating
explosives. Consequently, the threat to the soldiers on either side
of the munition 10 is reduced to the threat posed by the blast.
[0025] The munition 10 described above may be used as a warhead in
conjunction with a wide range of interceptors including projectiles
and self-propelled missiles and spinning or non-spinning and
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 guidance
system will determine when to fire a sequence of motors on the
interceptor and when to detonate the warhead. This sequence may be
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.
[0026] With reference now in addition to FIG. 3, the munition 10 is
shown as part of a missile 50. The munition 10, acting as a warhead
on the missile 50 may when detonated spread the fragments 14 in a
preferred direction, in a cone having a half angle 52 around the
longitudinal axis 30. The fragments 14 may be expelled with an
approximately uniform density over the half angle 52. The
half-angle 52 may be from 5 degrees to 10 degrees, or may have
other suitable values. It is desirable that the munition be
detonated at a location where it is able to destroy an incoming
threat with a high likelihood of success, while minimizing the
threat of collateral damage to the troops or, more generally, to
any person or object other than the engaged threat. To this end,
the munition 10 may be detonated at a standoff distance away from
the threat, to expel the fragments 14 in the prescribed half angle
52, to destroy the threat.
[0027] Ideally, the threat of injury or other damage outside of the
half angle 52 is minimal, for instance being reduced essentially to
the threat posed by the blast, since the casing 20 (FIG. 1) may be
reduced (pulverized) to a powder of fine particles 64 by the
explosion. As noted above, the particles 64 may have a mass
efficiency of 1% or less, so that the lethality outside of the half
angle 52 is approximately the same as the lethality from the blast.
For typical countermeasure-sized warheads the blast may pose a
threat only to a distance of a few meters.
[0028] The munition 10 presents many advantages over prior devices.
One advantage is the reduced danger to friendly troops through use
of the casing 20 that may be mostly or nearly completely pulverized
(or otherwise be rendered non-injurious) during detonation. Another
advantage is the reduced chance of unwanted detonation from impact
of bullets, shrapnel, or other objects, resulting from use of the
insensitive explosive. The munition 10 has a light weight (due to
the lightweight low-fratricide casing).
[0029] Although the invention has been shown and described with
respect to a certain preferred embodiment or embodiments, it is
obvious that equivalent alterations and modifications will occur to
others skilled in the art upon the reading and understanding of
this specification and the annexed drawings. In particular regard
to the various functions performed by the above described elements
(components, assemblies, devices, compositions, etc.), the terms
(including a reference to a "means") used to describe such elements
are intended to correspond, unless otherwise indicated, to any
element which performs the specified function of the described
element (i.e., that is functionally equivalent), even though not
structurally equivalent to the disclosed structure which performs
the function in the herein illustrated exemplary embodiment or
embodiments of the invention. In addition, while a particular
feature of the invention may have been described above with respect
to only one or more of several illustrated embodiments, such
feature may be combined with one or more other features of the
other embodiments, as may be desired and advantageous for any given
or particular application.
* * * * *