Note: Descriptions are shown in the official language in which they were submitted.
CA 02990862 2017-12-27
PROPELLING CHARGE SYSTEM FOR ARTILLERY SHELLS
Technical field
The invention relates to a propelling charge system for firing artillery
shells, more particularly
for 105 mm howitzers, built on a combination of two different powder types,
one with
diffused inert plasticizer in the near-surface zones and the other essentially
without diffused
inert plasticizer.
Prior art
A howitzer is understood to refer to a piece of artillery characterized by a
relatively short
barrel and the possibility of firing relatively heavy shells with relatively
low charge masses,
wherein the shells can reach high trajectories and are launched at a steep
firing angle. For over
100 years, 105 nun howitzer systems, also referred to as field artillery, have
enjoyed
continuous popularity with many armies around the globe. This type of weapon
became
massively more widespread during the course of World War I, and since then,
battlefields
have been characterized by the destructive power of artillery weapons systems.
Field artillery
cannons are important instruments for achieving the desired destructive power.
The
ammunition to be fired is equally important for achieving this destructive
effect. This weapon
thus makes it possible to transport a shell to the target area reliably and
with pinpoint
accuracy, while the desired target effect is produced by the correspondingly
configured
ammunition. For a long time, the only known target effect of field artillery
was maximum
destruction. However, new technological possibilities have now made the
scenarios at the
point of impact more varied, allowing a wide variety of effects to be achieved
at the target
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area. An example of such an effect, in addition to the maximum possible
destruction, is the
provision of a smokescreen in order to protect one's own troops.
For many years, the 105 mm howitzers M101 and M2 were the light field
howitzers of the US
military and were widely used during World War II in the European and Pacific
theaters of
operations. The 105 mm family was completed by the air-chargeable version M3,
which was
based on the M2 system but had a barrel that was shorter by 690 mm and a more
effective
recoil brake. The M3 howitzer was capable of using the same ammunition as the
M2, but
because of its shorter barrel, more highly explosive powder had to be used as
the propellant.
Production of the M2 and M3 systems was begun in 1941. When deployed, these
weapons
systems showed impressive results due to their precise target accuracy and
highly lethal effect.
Because of these qualities, combined with the fact that they were mass
produced, this family
of weapons became the standard howitzer system used in many countries after
the war, and
they remain in widespread active use today. Overall, the M101 howitzer system
is used
worldwide by a total of 67 different armies and is thus the most successful
artillery system
ever produced. Over time, the original types of ammunition developed into the
standard for
various new ammunition variants of later systems that were tailored to the
specific
requirements of the country in question.
The M101 system has been out of service in the US for some time now. As its
successor, the
howitzer M102A1, which had been developed earlier, was introduced by the US
armed forces
in March of 1966. In many countries, however, the M101 and M2 systems,
together with the
more recent M102A1 systems, continue to be in active use. France and Vietnam
used such
systems during the First Indochina War, as did the North Vietnamese Army.
Modernized
M102A1 systems continue to be actively used by the People's Army of Vietnam
today.
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M102A1/M101 howitzers were also used in former Yugoslavia, and 50 of these
weapons are
still being used in Croatia.
A further example of a 105 mm howitzer system that remains in widespread use
worldwide is
the L118 Light Gun. These are externally purchased howitzers that were
originally produced
by the British Army in the 1970s and subsequently widely exported.
As a further widely-used 105 mm howitzer system, one should also mention the
LG1. This
modern system is also externally produced, is highly valued for its light
weight and high target
accuracy accompanied by its relatively long range, and is produced by GIAT
Industries (now
the Nexter Group). This system is currently in active use by the armies of
Belgium, Canada,
Colombia, Indonesia, Singapore and Thailand, among other countries.
As a last example, one should mention the system Oto Melara Mod 56. This is a
105 mm
howitzer of Italian origin that can use ammunition such as that of the US Ml.
The Oto Melara
105 mm Mod 56 howitzer was put into operation in the 1950s. Because of its
light weight, it
was primarily used by the Mountain Artillery of the Italian Alpini Brigade. It
is still possible
.. today to transport this weapon via helicopter without dismantling it, which
aroused the interest
of other, primarily western nations in the 1960s. Overall, the Mod 56 howitzer
was used in
more then 30 countries worldwide. This weapon is currently in active use in at
least 23
countries, including Argentina, Brazil, Chile, Greece, Malaysia, Mexico, Peru,
the Philippines,
Saudi Arabia, Spain, Thailand and Venezuela.
As described above, large numbers of 105 mm howitzers are therefore in active
use
worldwide, with these largely consisting of the various types described above.
Although all of
these systems use the same caliber of 105 mm, each of the various howitzer
types requires
ammunition specifically tailored to the system in question. This is due to
differences in the
barrel structure (length, gas pressure limits), ballistic table, or available
charge volume.
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Despite these differences, however, all of these howitzer systems have common
features, i.e.
fundamental principles, that apply to every type of ammunition. Of particular
relevance here is
the fact that combat against a target generally involves indirect fire, i.e.
the shells are fired
upward, causing the projectile to follow a parabolic flight path. In addition,
an artillery charge
system is composed of a differing number of individual charges in order to
cover the widest
possible range of effect, with the number of charges corresponding to the
number of zones of
the respective ballistic table.
A common feature of all currently used 105 mm howitzer systems is thus that a
charge system
is used for firing ammunition composed of multiple individual charges. If only
a few
individual charges, e.g. charge 1 or charge 2, are used, the two lowest zones
of the ballistic
table can be covered with fire. However, if the maximum provided number of
charges is
loaded, e.g. all seven possible partial charges, the weapon can be fired with
the maximum
possible range, i.e. the highest zone of the ballistic table can be covered
with fire.
The conditions under which the powder of a propelling charge burns off vary
widely
.. depending on the charge used. In charge 1, which is used against the
closest targets (zone 1 of
the ballistic table), the powder mass is lowest relative to the shell mass.
There is thus only a
relatively small amount of gas available for accelerating the shell in the
barrel of the weapon,
with the result that the pressure conditions prevailing during powder
conversion are at a
relatively low level. This means that the powder for low charges must be
configured such that
.. complete burn-off occurs at the relatively low pressure in order to
minimize the discharge of
unburned powder particles. In use of the highest possible charge for the
respective howitzer
system, however, the maximum chargeable amount of powder is used. This allows
the
maximum possible amount of gas to be released in the barrel for accelerating
the shell, with
the result that powder burn-off takes place at a relatively high level of
pressure, which can be
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as high as the system limit of the 105 mm howitzer system used. As powder burn-
off is
significantly increased by higher pressure, the powder used in higher charges
must be
configured correspondingly, i.e. it must react significantly more slowly
compared to the
powders of low charges.
A drawback of the known propellant systems for artillery shells is that
important ballistic
characterizing data such as muzzle velocity and peak gas pressure are affected
by the ambient
temperature, wherein the lowest values occur at cold temperatures and these
values increase
continuously with rising temperature. Ambient temperature therefore has a
direct effect on the
performance and accuracy of the weapon.
A trend has also recently become established in which a significant majority
of armed
conflicts are taking place in hot climatic zones. Examples of this include
Iraq, Afghanistan and
Somalia. In order to achieve the high internal ballistic performance required,
large amounts of
explosive oils such as dinitrotoluene (DNT) and plasticizers such as
dibutylphthalate (DBP)
must be added to the propelling charge powders. However, such propellants have
been found
to be unsuitable under high thermal loads because pronounced changes in muzzle
velocity and
peak gas pressure occur after storage for several months. This effect reduces
the first-hit
probability, and because of the resulting increase in peak gas pressure of up
to 50%, this
constitutes a high safety risk during firing, because the pressure limit of
the weapon can be
significantly exceeded in an uncontrolled manner. However, exposure to high
temperatures in
hot climatic zones also sharply impairs the thermal stability of an explosive-
oil-containing
propellant in that, among other factors, the stabilizer is used up much more
quickly, which
increases the risk of uncontrolled autocatalysis due to aging. The detonation
reaction of a
propellant caused thereby can destroy an entire ammunition depot and injure
personnel. A
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modern propellant system for 105 mm howitzers should therefore provide the
high
performance required without containing explosive oil.
A possible approach for solving this problem is known and involves mixing a
crystalline
energy carrier, for example nitramine compounds such as e.g. RDX or HMX into
the particle
.. matrix. In this manner, high internal ballistic performance can be achieved
without the use of
explosive oils (US 8,353,994 B2; WO 2014/117280 Al). In addition, it is known
that the
temperature characteristics of a propelling charge powder can be selectively
improved by
means of surface treatment. By suitably selecting the treatment parameters, it
is thus possible
to attenuate both the decrease in the cold curves and the increase in the heat
curves of muzzle
velocity and peak gas pressure (US 7,473,330 B2; US 8,353,994 B2; WO
2014/117280 Al).
Of significance in this context is that the parameters of the surface
treatment applied, more
particularly the amount of camphor used, have different effects on temperature
coefficients
depending on the class of weapon in question. For example, in medium-caliber
weapons, an
increase in the amount of camphor causes flattening of the heat curves of
muzzle velocity and
peak gas pressure, i.e. the increase in pressure is attenuated (US 8,353,994
B2). In mortar
weapons, in contrast, an increase in the amount of camphor has the opposite
effect, i.e. the
heat curves of muzzle velocity and peak gas pressure become steeper or the
increase in
pressure becomes sharper respectively (WO 20 14/1 17280 Al). It has been found
in practice
that in medium-caliber systems, the amounts of camphor must typically be
adjusted to 3-5
wt.% in order to minimize this steepening of the heat curves. In mortar
systems, however, the
amount of camphor must be set as low as possible (<0.5%) or the substance must
be omitted
altogether in order for the heat curves of muzzle velocity and peak gas
pressure to show the
smallest increase possible.
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Nitroglycerin-containing propellants, predominantly so-called ball powder, are
only used to a
relatively minor extent in artillery, being used only in special applications
such as e.g. high-
performance charges (unit charges). The most widespread powder type used in
105 mm
artillery is composed of a particle matrix essentially containing
nitrocellulose, approximately
10% dinitrotoluene (DNT) and approximately 5% of the plasticizer
dibutylphthalate (DBP).
However, the ballistic stability of this powder type is insufficient because
of diffusion of the
plasticizer, particularly when used in hot climatic zones. The two known types
of nitroglycerin
and dinitrotoluene containing powder types for 105 mm artillery applications
can both contain
dibutylphthalate as a plasticizer. However, dinitrotoluene and
dibutylphthalate are not
compatible with Regulation (EC) No. 1907/2006 (REACH) and therefore will no
longer be
allowed for use in the European Union.
The propelling charge system to be fired can generally also be used in other
caliber ranges,
e.g. in 155 mm systems. For this purpose, the wall thicknesses of the powders
used would
have to be adapted in a manner known to persons skilled in the art.
Description of the invention
The object of the invention is to provide a propelling charge belonging to the
technical field
mentioned above in which the peak gas pressure and thus the muzzle velocity
show the
smallest possible variation over a broad temperature range, more particularly
between -
46 C and 63 C, compared to the peak gas pressure and muzzle velocity at 21 C.
More
particularly, the peak gas pressure of the highest charge possible for
achieving the maximum
range at an ambient temperature of 63 C should not be substantially higher
than at an ambient
temperature of 21 C. In addition, powder burn-off should take place without
leaving any
residue, even in the case of low charges and an ambient temperature in the
range of -46 C,
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wherein the muzzle velocities achieved should not deviate substantially from
the muzzle
velocity at an ambient temperature of 21 C. Finally, the propelling charge
system should show
higher chemical and ballistic stability without requiring the use of any toxic
substances. In
addition, the propelling charge system should show a high thermal conversion
rate with low
charges, while the highest possible thermal efficiency should be achieved with
high charges.
According to the invention, a propelling charge system for firing artillery
shells comprises at
least two partial charges. Each partial charge has one powder type as a
propellant, said charge
comprising at least one crystalline energy carrier and at least one first
inert plasticizer. At least
one partial charge is composed of a first powder type, and the at least one
further partial
charge is composed of a second powder type. In the area of the near-surface
zones to a
penetration depth of at most 400 m, the second powder type contains between 2
and 10 wt.%
of a second inert plasticizer, while the first powder type contains no second
inert plasticizer in
the near-surface zones. "No second inert plasticizer" is understood to refer
to a concentration
of the second inert plasticizer of 0% in the near-surface zones of the first
powder type.
Surprisingly, it has now been found that a propelling charge system for firing
artillery shells,
more particularly for 105 mm howitzers, built on the combination of two
different powder
types with a second inert plasticizer and without a second inert plasticizer
in the near-surface
zones, provides internal ballistic properties that are favorable to an
unanticipated degree.
As the second inert plasticizer is preferably diffused in the near-surface
zones, the following
application refers to the use of the second powder type with a diffused second
inert plasticizer
and the first powder type without a diffused second inert plasticizer.
Ordinarily, the lowest muzzle velocities and peak gas pressures occur at the
lowest firing
temperature and rise continuously with increasing firing temperature, i.e. the
highest values
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Date Recue/Date Received 2021-08-06
CA 02990862 2017-12-27
are normally achieved at the highest allowable firing temperature for a given
powder type.
However, if the proper composition is selected, ambient temperature has only a
minor effect
on the characteristic internal ballistic data of muzzle velocity and peak gas
pressure. The
probability of a hit can be increased by selectively minimizing the range of
variation of the
muzzle velocities that occur over the entire allowable temperature range of
the weapons
system.
In addition, the increase in peak gas pressure on transition from 21 C to 63 C
is minimal. This
opens up the possibility of operating the weapon under normal conditions, i.e.
at temperatures
around 21 C, at a higher pressure level than is possible with conventional
charge systems,
because the only minor variation in the peak gas pressure on increasing firing
temperature
prevents this pressure from exceeding the maximum allowable gas pressure of
the barrel of the
howitzer used. This allows the performance of a howitzer system to be improved
and opens up
the possibility of increasing its range by using an additional charge.
Placement of a second inert plasticizer in the near-surface zones of the
second powder type
should preferably take place by means of corresponding surface treatment, for
example by
mixing a semi-finished product of the second powder type with a solution of
the second inert
plasticizer in an organic solvent. Accordingly, the following application also
refers to powder
types with and without surface treatment, wherein the powder type with surface
treatment in
the near-surface zones contains the second inert plasticizer in a
concentration of 2 to 10 wt.%
and the powder type without surface treatment contains no second inert
plasticizer in the near-
surface zones. Both of the powder types contain as their main component
nitrocellulose
mixtures with a preferred average nitrogen content of above 13.25%. As further
key
components, the two powder types contain a crystalline energy carrier and at
least one first
inert plasticizer.
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Furthermore, the powder types comprise at least one muzzle flash suppressor,
such as e.g.
potassium sulfate, potassium bitartrate or potassium nitrate in amounts of 0.5-
5 wt.%,
preferably 1-3 wt.%. In addition, the propellants more preferably comprise
stabilizers such as
e.g. acardite II (CAS-4 724-18-5), centralite I (CAS-4: 90-93-7),
diphenylamine (CAS-4: 122-
39-4), or a barrel-protecting additive, such as e.g. calcium carbonate (CAS-4:
471-34-1).
Nitrocellulose is obtained by nitration of cellulose (cotton linters, pulp)
and has been the most
important starting material for the production of monobasic, dibasic, and
tribasic propelling
charges for over 100 years. Nitrocellulose is available in large quantities at
inexpensive prices
and is offered with a wide range of various physicochemical properties, such
as nitrogen
content, molecular weight and viscosity. These variations allow nitrocellulose
to be processed
into the widest variety of homogeneous propelling charge powder types. The
energy content of
nitrocellulose is adjusted via its nitrogen content.
Preferably, in an artillery shell, partial charges with the first powder type
are used for the
lower zones of the ballistic table, e.g. for charge 1, and partial charges
with the second powder
type are used for the upper zones of the ballistic table. This means that for
firing an artillery
shell, one to three, and preferably one to two partial charges with the first
powder type are first
charged into a casing, followed by one to six partial charges with the second
powder type,
depending on the zone of the ballistic table for which the artillery shell is
to be used. By using
a flexible number of partial charges, it becomes possible by means of the
propelling charge
.. system according to the invention to cover the widest possible range of
zones of a ballistic
table, wherein an outstandingly advantageous inner ballistic behavior can be
achieved in all
cases.
This is characterized in that with low charges, in which at least one partial
charge with the first
powder type is used, higher powder conversion rates (high thermal
efficiencies) can be
CA 02990862 2017-12-27
achieved, which minimizes the discharge of unburned powder material and
increases the
performance potential. In addition, the cold drop of the temperature curves of
muzzle velocity
and peak gas pressure is minimized.
On the other hand, the surface treatment of the second powder type of partial
charges, which
are used for high charges, causes the quotient of muzzle velocity and peak gas
pressure
(vo/pmax) to be as high as possible, i.e. the intended muzzle velocities
required to meet the
requirements of the ballistic table can be achieved with the lowest possible
gas pressure. It was
also surprisingly found that surface treatment of the second powder type
significantly reduces
the increase in the heat curves of muzzle velocity and peak gas pressure. In
this manner, the
muzzle velocity required for the highest zones of the ballistic table and thus
the highest
required muzzle velocity can be achieved without exceeding the gas pressure
limits of the
howitzer system used.
As initial tests have shown, the internal ballistic specifications could not
be met if the charge
system were composed of only one homogeneous powder type, e.g. in surface
treatment with
an average amount of the second inert plasticizer relative to the second
powder type according
to the invention. If only partial charges with the second powder type were
used, conversion
and ignition of the low charges would be poor, causing a large proportion of
unburned powder
to be discharged from the barrel. In addition, because of the poorer ignition
time due to
phlegmatization of the surface in the cold area in particular, significantly
lower values and an
unacceptable dispersion of muzzle velocity and peak gas pressure would be
expected. On the
other hand, if only partial charges with the first powder type were used, the
peak gas pressure
on firing of the highest charge for achieving the required muzzle velocity for
maximum range
would sharply increase at high firing temperatures and exceed the allowable
pressure limits.
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The first powder type and the second powder type preferably comprise particles
with a circular
cylindrical geometry and longitudinal channels running in an axial direction,
wherein the
particles of the first powder type preferably have one to four longitudinal
channels and the
particles of the second powder type have seven to nineteen longitudinal
channels.
The longitudinal channels of the particles are arranged in an essentially
circular area around
the longitudinal axis of the particles. The particles have walls with a wall
thickness between
this area and the external circumferential surface of the particles.
Propellants composed of particles are used as pourable powder. They are
capable of pouring
(or trickling), which is important for the industrial filling of partial
charges into containers,
more particularly bags. The propelling charge powder can thus be handled like
a liquid during
filling into containers.
More particularly, the particles can be produced by extrusion.
The wall thicknesses of the two powder types depend on the artillery system in
question. For a
105 mm system, the wall thickness of the first powder type is 0.4-1.2 mm, and
preferably 0.5-
1.0 mm, while the particles of the second powder type have thicknesses of 0.3-
1.1 mm, and
preferably 0.4-0.9 mm.
Within the meaning of the present application, the term "wall thickness" is
understood to refer
to the distance between the external circumferential surface of the particles
and the area in
which the longitudinal channels are arranged.
The concentration of the second inert plasticizer in the near-surface zones of
the second
powder type is preferably between 3 and 6 wt.%.
The at least one crystalline energy carrier is a nitramine compound of the
general chemical
structure RI -R2-N-NO2 and preferably comprises hexogen (RDX) or octogen
(HMX), more
particularly in a concentration of 0 to 30 wt.%, and most preferably 5 to 15
wt.%.
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The energy carrier is preferably in crystalline form at room temperature. Use
of these amounts
in a base of nitrocellulose allows the average distances between the
individual crystals of the
crystalline energy carrier to be sufficiently large so that the individual
crystals predominantly
do not touch one another. As a result, on exposure to external mechanical
stimuli, the shock
pulse essentially cannot be passed on from one energy carrier crystal to the
adjacent crystals.
A primary shock pulse is therefore not multiplied and transferred over the
entire amount of
powder.
The two compounds RDX and HMX of the general formula R-N-NO2 (R = residue)
have a
relatively small residue R, which constitutes a relatively small portion of
the entire molecule
compared to the nitramine structural element. The two compounds thus show a
relatively high
energy content.
RDX is preferably used as a crystalline energy carrier. Compared to HMX, it
can be
manufactured more economically and safely. HMX is more expensive than RDX but
offers no
particular advantages. Compared to RDX, other nitramine compounds (e.g. NIGU,
etc.) have a
relatively low internal ballistic performance potential.
Particularly preferably, the crystalline energy carrier has a specified
average particle size. For
example, RDX with an average particle size of 4-10 um, and more particularly 6
rim, is
preferably used. It is important for the crystal energy carrier to have the
most homogeneous
and finest particulate size possible in order to improve particle burn-off and
thus improve the
internal ballistic performance potential.
As an alternative to the nitramine compounds, for example, a nitrate ester of
the general
formula R-O-NO would be conceivable. However, nitrate esters are less
chemically stable
than nitramine compounds. Moreover, it is possible to use nitramine-based
crystalline energy
carriers that have additional nitrate ester groups in their molecular
structure. Examples of
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crystalline energy carriers include: hexanitroisowurtzitane (CL-20, CAS-4
14913-74-7),
nitroguanidine (NIGU, NQ, CAS-# 70-25-7, N-methylnitramine (tetryl, N-Methyl-
N,2,4,6-
tetranitrobenzolamine, CAS-4 479-45-8) nitrotriazolone (NTO, CAS-4 932-64-9)
and
triaminotrinitrobenzene (TATB, CAS-4 3058-38-6). All of these energy carriers
can be used
either individually or in combination with one another.
Active substances knownper se, such as e.g. acardite II, can be used for
stabilization.
Preferably, the propellants contain the at least one first inert plasticizer
in a concentration of 0
to 10 wt.%, and preferably 1 to 5 wt.%, wherein the first inert plasticizer is
preferably
homogeneously distributed in the particle matrix.
By adding only relatively small amounts (e.g. <10 wt.%) of the at least one
inert plasticizer to
the particle matrix, resistance to mechanical stimuli can be significantly
improved. Depending
on the application, combinations of a plurality of inert plasticizers can be
used in order to
adjust the desired thermodynamic properties. The particle structure of such
propellants can be
adapted to the specific application (e.g. adaptation of burn-off
characteristics to the barrel
length, shell weight, etc. of the weapons system).
The at least one first plasticizer preferably comprises a carboxylic acid
ester compound, more
particularly from the groups of the phthalate esters, citrate esters,
terephthalic esters, stearate
esters or adipate esters.
The second inert plasticizer preferably comprises at least one compound from
the group
comprising camphor, dialkyl phthalate and dialkyl diphenylureas.
Particularly preferably, camphor (CAS-4 76-22-2) is used as the second inert
plasticizer.
Each of the first and the second powder types of the at least two partial
charges is preferably
placed in a cylindrical cloth bag, wherein the cloth bags preferably have a
through opening
along their longitudinal axis.
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The partial charges for artillery propelling charges of the prior art are
filled into rectangular
bags. Depending on the zone of the ballistic table to be covered with fire, a
suitable number of
these bags is arranged in a casing of an artillery shell. However, the
drawback of said bags is
that because of their rectangular configuration, they cannot be optimally
placed inside the
cylindrical casing of the shell, resulting in a relatively large amount of
empty space inside the
casing, which has an adverse effect on the maximum possible additional amount
of powder
that can be charged into the casing and can lead to irregular burn-off.
The use of cylindrical cloth bags according to the present invention allows
more optimal space
utilization inside a casing. This also prevents folding or rolling up of the
bags prior to
insertion, which considerably simplifies handling of the propelling charge
system according to
the invention.
If the cloth bags according to a preferred embodiment have a through opening
along their
longitudinal axis, this allows them to be slipped over and aligned onto an
element centrally
arranged inside the casing, such as e.g. a priming cap.
The diameter of the cylinder bottom surface of the cloth bags preferably
corresponds to the
internal diameter of a casing in which the propelling charge system according
to the invention
is to be placed. The height of the cylinder can be varied depending on the
required amount of
powder of the respective partial charge.
A person skilled in the art will recognize that the disclosed cloth bags can
be used not only in
connection with the propelling charge system according to the invention, but
also generally
used in various types of propelling charge systems.
Preferably, at least one of the at least two partial charges contains at least
one piece of tin foil
as a decoppering agent.
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Compared to lead, which was previously conventionally used, tin has the
advantage of being
considerably more compatible with the environment and non-toxic.
In a preferred propelling charge system with seven partial charges, two pieces
each of tin foil
are preferably placed in several cloth bags.
The present application further relates to the use of a propelling charge
system according to
the invention for firing an artillery shell, wherein one to three partial
charges with the first
powder type is/are used in order to cover ranges in the lower zone of a
ballistic table and an
additional one to six partial charges with the second powder type is/are used
in order to cover
ranges in the upper zone of the ballistic table.
The following detailed description and the entirety of the patent claims
disclose further
advantageous embodiments and combinations of features of the invention.
Examples
Preparation example 1: Powder type 1 without surface treatment, for zone 1
A 1-hole (longitudinal channel) powder is produced by processing 150 kg of
powder paste
composed of the solid components 10 wt.% of hexogen, 1.3 wt.% of acardite II,
1.2 wt.% of
potassium sulfate, 1.5 wt.% of a phthalate ester (primarily composed of linear
C9-C11 alcohols
with an average molecular weight of 450 g/mol and an average dynamic viscosity
at 20 C of
73 mPa*s) and nitrocellulose with a nitrogen content of 13.20 wt.% (made up to
100%), while
adding diethyl ether and ethanol, into a solvent-wetted kneaded paste. After
kneading for 70
min, this kneaded paste is pressed (i.e., extruded) through a die having a 1-
hole geometry and
a 3.2 mm strand cross-section. After predrying in air, the extruded strands
are cut to the
desired length. After this, the remaining residual solvents are removed at an
elevated
temperature. The resulting semifinished powder product is then heated to 55 C
and mixed in a
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copper polishing drum heated to 55 C with 0.1% graphite and 2.5 L of an
aqueous ethanol
solution. The reaction proceeds under constant rotation for 2 h, during which
time the ethanol
continuously evaporates. After completion of graphitization, the powder is
placed in a bath for
22 h at 80 C, spread onto steel sheets and dried for 22 h at 60 C.
The resulting powder has the following physical properties: 2.00 mm external
diameter,
5.04 mm length, 0.91 mm average wall thickness and 0.17 mm hole diameter, 3754
J/g heat
content and 945 g/l bulk density.
Chemical stability:
Deflagration point = 174 C.
Heat flow calorimetry according to STANAG 4582 = 16.5 J/g resp. 20 p.W/g
(requirement according to standard STANAG 4582: maximum heat generation < 114
[tW/g).
Preparation example 2: Powder type 2 with surface treatment, for zones 2-4
A 7-hole powder is produced by processing 225 kg of a powder paste composed of
the solid
components 16 wt.% of hexogen, 1.3 wt.% of acardite II, 1.2 wt.% of potassium
sulfate,
1.5 wt.% of a phthalic acid ester (primarily composed of linear C9-C11
alcohols with an
average molecular weight of 450 g/mol and an average dynamic viscosity at 20 C
of 73
mPa*s) and nitrocellulose with a nitrogen content of 13.20 wt.% (made up to
100%), while
adding diethyl ether and ethanol, into a solvent-wetted kneaded paste. After
kneading for 70
min, the kneaded paste is pressed (i.e., extruded) through a die having a 7-
hole geometry and a
7.0 mm strand cross-section. After predrying in air, the extruded strands are
cut to the desired
length. After this, the remaining residual solvents are removed at an elevated
temperature. The
resulting semifinished powder product is then heated to 55 C and mixed in a
copper polishing
drum heated to 55 C with 0.12% graphite, 2.5% camphor and 4.5 L of an aqueous
ethanol
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solution. The reaction proceeds under constant rotation for 2 h, during which
time the ethanol
continuously evaporates. After completion of the surface treatment, the powder
is placed in a
bath for 30 h at 85 C, spread onto steel sheets and dried for 22 h at 60 C.
The resulting powder has the following physical properties: 4.66 mm external
diameter, 9.03
mm length, 1.05 mm average wall thickness and 0.15 mm hole diameter, 3653 J/g
heat content
and 957 g/1 bulk density.
Chemical stability:
Deflagration point = 176 C.
Heat flow calorimetry according to STANAG 4582 = 22.2 J/g resp. 27 W/g
(requirement according to standard STANAG 4582: maximum heat generation < 114
uW/g).
Preparation example 3: Powder type 2 with surface treatment, for zones 5-6
A 7-hole powder is produced by processing 225 kg of a powder paste composed of
the solid
components 25 wt.% of hexogen, 1.3 wt.% of acardite II, 1.7 wt.% of potassium
sulfate,
1.5 wt.% of a phthalic acid ester (primarily composed of linear C9-C11
alcohols with an
average molecular weight of 450 g/mol and an average dynamic viscosity at 20 C
of 73
mPa*s) and nitrocellulose with a nitrogen content of 13.20 wt.% (made up to
100%), while
adding diethyl ether and ethanol, into a solvent-wetted kneaded paste. After
kneading for 70
min, the kneaded paste is pressed (i.e., extruded) through a die having a 7-
hole geometry and
an 8.0 mm strand cross-section. After predrying in air, the extruded strands
are cut to the
desired length. After this, the remaining residual solvents are removed at an
elevated
temperature. The resulting semifinished powder product is then heated to 55 C
and mixed in a
copper polishing drum heated to 55 C with 0.12% graphite and 7.5 L of an
aqueous ethanol
solution. The reaction proceeds under constant rotation for 2 h, during which
time the ethanol
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continuously evaporates. After completion of the surface treatment, the powder
is placed in a
bath for 30 h at 85 C, spread onto steel sheets and dried for 22 h at 60 C.
The resulting powder has the following physical properties: 5.66 mm external
diameter,
8.59 mm length, 1.31 mm average wall thickness and 0.14 mm hole diameter, 3679
J/g heat
content and 969 g/1 bulk density.
Chemical stability:
Deflagration point = 177 C.
Heat flow calorimetry according to STANAG 4582 = 25.1 J/g resp. 29 Wig
(requirement according to standard STANAG 4582: maximum heat generation < 114
W/g).
Application example 1:
System: Howitzer system 105 mm M119
Projectile: M1 with a mass of 14.5 kg
Charge bag: Donut-Bag NCW with central hole
Primer: M28E2 (Benite primer)
Table 1: Charge masses of powder used for zones 1-6
Zone Powder Surface treatment Charge mass
1 Preparation example 1 No 196 9
2 Preparation example 2 Yes 116
3 Preparation example 2 Yes 219 9
4 Preparation example 2 Yes 265 g
5 Preparation example 3 Yes 6259
6 Preparation example 3 Yes 640 g
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Table 2: Muzzle velocities in m/s at -46 C, 21 C and 63 C
Zone -46 C 21 C 63 C
1 177.1 183.0
2 215.5 224.1
3 - 277.2
4 340.3 358.2 374.0
472.8 504.0 494.7
6 651.5 651.8 6208.
Table 3: Peak gas pressures in bar at -46 C, 21 C and 63 C
Zone -46 C 21 C 63 C
1 344 461
2 427 433
3 - 512
4 737 849 948
5 1434 1697 1634
6 3262 3371 2923
5 Table 4: Thermal efficiencies for energy conversion of the individual
zones at 21 C
Zone Therm. efficiency
1 33%
2 32%
3 29 %
4 32%
5 35 %
6
41%
It can be seen that by means of the novel charge, composed of the combination
according to
the invention of two powder types with and without surface treatment, i.e.
with a diffused
second inert plasticizer and without a diffused second inert plasticizer for
low charges 1-2 in
the cold area, only extremely small decreases in muzzle velocity occur,
specifically - 5.9 m/s
in zone 1 and 8.6 m/s in zone 2. The energy conversion into kinetic energy
takes place with a
high degree of efficiency both in zone 1, where only the powder without
surface treatment is
used, and in zone 2, where the combination of the two powder types with and
without surface
treatment is used, which is reflected in high efficiencies of 33% (zone 1) and
32% (zone 2)
despite the low peak gas pressures of < 500 bar.
CA 02990862 2017-12-27
In the case of the higher charges for zones 4-6 as well, the combination
according to the
invention of two powder types with and without surface treatment astonishingly
makes it
possible for the cold drops of the muzzle velocities to be only relatively
small, specifically
between 20-30 m/s for zones 4 and 5, while surprisingly, there is virtually no
cold drop in
zone 6, i.e. the peak gas pressures at -46 C and 21 C are virtually identical.
This shows that in
the charge system described, because of the combination of two powder types
with and
without surface treatment, the muzzle velocities of the individual partial
charges on firing
within the temperature range of -46 C to 21 C are only affected to a minor
degree by the
ambient temperature, thus significantly increasing the hit probability.
For zone 6, the amount of powder was adjusted such that at 21 C, the muzzle
velocity was 652
m/s. The peak gas pressure occurring at this velocity is only 3371 bar, i.e.
the ratio vo/pmax is
relatively high, as hoped. In addition, no increase in pressure occurs on
transition to the
maximum firing temperature. This means that because of the charge structure
according to the
invention, the weapon can be operated over the entire temperature range far
below the system
pressure limits of 3965 bar. If needed in order to improve performance, the
pressure reserve of
600 bar can be utilized by means of an additional charge for increased range.
In use of a
conventional charge system having powder without surface treatment, a classic
burn-off
occurs, i.e. a continuous increase in muzzle velocity and peak gas pressure
with increasing
firing temperature. The result of this behavior is that at the maximum
allowable firing
temperature, one reaches the gas pressure limits, thus eliminating the
possibility of increasing
the range. If the increase in pressure is extremely high with a conventional
charging design in
a particular application, it may happen that the peak gas pressure at 63 C is
even exceeded on
reaching the muzzle velocity required at 21 C, i.e. the weapon can then be
operated only over
a limited temperature range.
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Brief description of the drawings
The drawings used to explain the example show the following:
Fig. 1 a propelling charge system according to the invention with
seven partial
charges in cloth bags;
Fig. 2 an arrangement of the propelling charge systems in a casing of an
artillery shell.
As a rule, the same parts are designated by the same reference numbers in the
figures.
Embodiments of the invention
Fig. 1 shows a propelling charge system according to the invention 1 with six
partial charges
2.1, 3.1-3.5. Each of the partial charges 2.1, 3.1-3.5 is placed in an
essentially cylindrical cloth
bag. The propelling charge system 1 shown comprises five second partial
charges 3.1-3.5 with
a second powder type as a propellant, containing between 2 and 10 wt.% of a
second inert
plasticizer in the region of the near-surface zones to a penetration depth of
at most 400 mn.
The propelling charge system 1 further comprises a first partial charge 2.1
with a first powder
type as a propellant, which contains no second inert plasticizer in the near-
surface zones. The
first partial charge 2.1 serves to cover the lower zone of the ballistic
table, while the second
partial charges 3.1-3.5 can be used to cover the upper zones of the ballistic
table.
Fig. 2 shows the arrangement of the propelling charge system according to the
invention 1 in a
casing 4 of an artillery shell. In this case, the first partial charge 2.1 is
arranged below the
second partial charge 3.1-3.5 in the casing 4. The cloth bags of the partial
charges 2.1, 3.1-3.4
have a through opening 5 along their longitudinal axis, through which a
priming cap 6 (shown
by the broken line) is guided. Because of their cylindrical shape, these cloth
bags can be
placed inside the casing 4 in a highly simple and space-saving manner.
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