[0001] The invention relates to a drag reduction system, more specifically a forward mounted
drag reduction system for use on extended range artillery.
[0002] There is a military requirement to extend the range of artillery projectiles without
reducing payload, and concomitant increase in propellant.
[0003] Whilst modification of the aerodynamics of the general physical shape of current
conventional projectiles, is possible, it is desirable for the external dimensions
and mass of an extended range projectile to conform closely to the external dimensions
and mass of existing projectiles. This allows both extended range projectiles and
existing projectiles to be launched from the same existing ordnance, without any need
for providing further modifications to the breech to ensure that the extended range
projectile does not exceed the maximum acceptable breech pressure.
[0004] It is possible to extend the range of projectiles by incorporating a rocket motor
to provide thrust after launch. It also is possible to extend the range of projectiles
by means of a base bleed, such as
US5886289. The use of a base bleed unit increases the range by reducing the base drag of the
projectile by increasing its base pressure. This is achieved by the controlled burning
of a pyrotechnic material which exhausts gases into the base region of the projectile.
[0005] Base-bleed systems offer extended range, however, the location of large gas generating
pellets at the rear of the projectile, may not be desirable for a variety of rounds
where restrictions in geometry, mass growth, or operational needs preclude its use.
According to a first aspect of the invention there is provided an extended range artillery
projectile, having forward end, an aft located base unit, located therebetween a projectile
body comprising a payload, and, a forwardly located gas generator capable of generating
a gas flow, said gas generator comprising an ignition device to activate the gas generator;
preferably at a predetermined time after the projectile is launched.
[0006] According to a further aspect of the invention there is provided an extended range
artillery projectile having forward end comprising a fuze, an aft located base unit,
located therebetween a projectile body defining cavity which comprises a payload,
and a forwardly located gas generator capable of generating a gas flow, said gas generator
comprising an ignition device to activate the gas generator; preferably at a predetermined
time after the projectile is launched.
[0007] The forwardly located gas generator may be located between the fuze and the projectile
body, preferably located on the ogive section between the fuze and the projectile
body to maximise flow along the system.
[0008] The gas generator provides a gas flow which may be directed substantially along the
outer surface of the projectile body, so as to provide a controlled flow of gas to
reduce air resistance, preferably providing laminar, or near laminar conditions. The
gas flow provides a reduction in the drag experienced by the projectile during its
flight. The location of the gas generator (bleed unit) at a forward position on the
projectile may afford control of trajectory of the projectile by controlling the direction
and/or impulse of the gas flow, from the gas generator.
[0009] To provide an extended range projectile the gas flow may be directed substantially
rearwardly towards the aft of the projectile, such that the drag coefficient of the
projectile is reduced, thus allowing the projectile to traverse a greater distance
compared to an un-assisted round.
[0010] The gas generator may provide a portion of gas flow which is substantially normal
to the projectile, to increase air resistance. Thereby the forwardly located gas generator
may be used as an air brake. The gas generator may be caused to provide an impulse
at an angle other than that which causes gas flow along the surface of the projectile,
such as for example in a direction which is substantially perpendicular to the projectile,
or directed forwardly towards the fuze. The selection of the direction of the gas
flow and the impulse may be used to control the flight of the projectile.
[0011] The gas generator may comprise a compressed gas or at least one portion of an energetic
material, such as for example a pyrotechnic composition or propellant composition,
to provide the gas flow. The at least one portion of energetic material may be in
the form of a consolidated pellet, or a plurality of propellant grains or propellant
sticks.
[0012] The ignition device may be any conventional igniter suitable for initiating propellants
and pyrotechnic compositions. The ignition device may comprise safety and arming units
(SAU), explosive trains to provide sufficient stimuli to the at least one portion
of an energetic material.
[0013] The ignition device may respond to an action from a selected input or stimuli or
a combination of inputs, such as, for example, mechanical actions of the projectile,
such as the action of high g forces from gun launch or high spin rates from imparted
spin, timed delay, either mechanical or pyrotechnic, caused by separation from the
launch system, or proximity to a target.
[0014] The ignition device may also function due to electronic activation, such as, for
example, from an input from a sensor or detector from on-board said projectile or
external to the projectile. On-board systems may be internal guidance systems. External
stimuli may be provided by fly-by wire, remote control, GPS, target activated laser
guidance, any form of instruction to cause a change in trajectory, or even to abort
the trajectory of the projectile from its intended target, and send it to a safe location.
[0015] The gas flow generator may comprise at least one nozzle, preferably a plurality of
nozzles, which may be used to control the direction of the projectile.
[0016] The nozzle may be any propelling nozzle, such as, for example a simple choke, venturi
or any other commonly used pyrotechnic or propellant gas controlling nozzle.
[0017] Where there are a plurality of nozzles, each nozzle may have its own at least one
portion of an energetic material, wherein each at least one portion of an energetic
material may be separately and independently ignited during the flight, as required
or ignited substantially simultaneously. The plurality of nozzles may consist only
of the at least one portion of energetic material, such that said plurality of nozzles
provide a uniform gas flow, from a single source, hence equally distributing the output
through said plurality of nozzles.
[0018] In order to provide an increase in the range of the projectile without causing any
change to the direction of the projectile, the gas flow must be a uniform, therefore
the at least one nozzle and concomitant gas flow must also be a uniform. The at least
one nozzle may be a single nozzle which extends uniformly around the circumference
of the projectile. Any non-uniformity may result in change in intended direction.
For example a projectile fired along the xy, plane, the decreased drag, caused by
the uniform gas flow preferably only increases the value of x, the total distance,
without causing substantial drift in the azimuth, xz, plane.
[0019] In a further arrangement, the plurality of nozzles, may located equidistant around
the circumference of the projectile, so as to provide a uniform gas flow along the
surface of the projectile.
[0020] In arrangements where directional control in the xz plane is desirable a non-uniform
gas flow may be required. Conventional base bleed units are not capable of providing
a directional gas flow, and only provide flow across the base.
[0021] In a preferred arrangement, the plurality of nozzles are each capable of being independently
ignited, so as to provide directional control by causing an unsymmetrical gas flow,
or substantially simultaneous ignited so as to provide a uniform gas flow, and an
extension of the range of the projectile.
[0022] The at least one nozzle may be a directionable nozzle, such that the direction of
the nozzle may be selected, such that the direction or thrust/impulse of the gas flow
may be selected and/or altered during flight, so as to provide active directional
control and/or air braking of the projectile during flight.
[0023] According to a further aspect of the invention there is provided a method of controlling
the trajectory of the projectile during flight, comprising the steps of activating
the gas generator, directing the gas flow so as to alter said trajectory.
[0024] The trajectory of an unspun projectile during flight may be caused to alter by selectively
changing the gas flow across the surface of the munition, and reducing drag to cause
the projectile to change trajectory.
[0025] The projectile may be any munition that has a flight trajectory. The projectile may
be such as for example a shell, mortar or missile. Whilst the invention has been described
above, it extends to any inventive combination of the features set out above, or in
the following description, drawings or claims.
[0026] Exemplary embodiments of the device in accordance with the invention will now be
described with reference to the accompanying drawings in which:-
Figures 1 shows a cross section of a prior art base bleed shell.
Figure 2 shows a cross section of forward mounted bleed unit, according to the invention.
Figure 3 shows a trajectory of a projectile fitted with a forwardly mounted gas generator
system.
Figure 4 shows a cross section of the nozzle configuration.
[0027] Turning to figure 1 there is provided a cross section of a, prior art, base bleed
assisted shell 1. A fuze 3 is located at a forward end of the shell body 8, and at
the rear of the shell body is a base unit 5. The base unit 5 contains a base bleed
unit 7, which contains an energetic material 9, and an ignition device 9a.
[0028] If the shell is to be spun, a driving band 6 is located around the circumference
of the shell body 8, towards the rearward end. The band 6 engages with the rifling
grooves in the launch barrel (not shown), to impart spin.
[0029] After the shell 1 is launched, the ignition device 9a will be caused to function
as a result of one of many stimuli, such as for example a delay composition initiated
during launch or activated by a high "g" force or high spin rate force. The ignition
device 9a will ignite the composition 9, which provides a gas flow 4. The gas flow
4 from the base bleed unit 7 fills the void 2a created by the high speed air flow
2 passing across outer surface of the shell body 8, as the shell 1 moves through the
air.
[0030] In the absence of a base bleed unit 7, the air flow 2 creates disturbed air flow
behind the shell base which causes further drag on the rear of the shell.
[0031] Figure 2 shows a cross section of a projectile 10, as defined herein. The projectile
10 comprises a projectile body 18, with a fuze 13 located at a forward end 12, and
at the rear end 14 of the projectile body is a base unit 15. The base unit 15 may
have a general boat tail configuration.
[0032] The gas generator 17, is located forward of the projectile body 18, and is preferably
located on an ogive surface portion 11 of the projectile body 18. The gas generator
17 is most preferably located between the fuze 13 and the projectile body 18. The
gas generator 17 may be a separate device from the fuze or it may form an integral
part of the fuze 13. The gas generator 17 is ignited by ignition device 19. The stimuli
to activate the ignition device may be any of the commonly used stimuli, such as,
delay compositions which are initiated during launch or an electronic timer, an RF
signal from a remote source, or a mechanically activated ignition device, such as
those activated by a high g or high spin rate forces.
[0033] The gas generator 17 provides a gas flow 24, via nozzle 20, so as to provide a near
laminar gas flow (thick line) 21, which flows over the contours of the projectile
body 18. The gas flow 24 provides a low friction surface to interact with the air
flow 22 such that the projectile body 18 experiences less air resistance from the
air flow 22 as the projectile body 18 travels through the air. The gas flow 24, is
of sufficient force to ensure that the air flow 22 does not move into the void 25
behind the base unit 15.
[0034] The projectile body 18 contains a payload 23, which may be HE, illumination or any
commonly used payload. As this design does not need a base unit - this payload may
also take the form of a system/set of sub-systems with capacity for rear dispensing.
[0035] If the projectile is to be spun, a driving band 16 may be located around the circumference
of the projectile body 18, towards the rearward end 14. The band 16 engages with the
rifling grooves in the launch barrel (not shown), to impart spin.
[0036] Figure 3 shows schematic of a ground plane xz, a non-bleed projectile may follow
a typical trajectory 43 with a final target distance 41 along the x-axis. The bleed
assisted projectile as defined herein, would start out with the same launch angle,
but would follow an extended path trajectory 44 due to experiencing less air resistance
and therefore would be able to travel a further distance to the final target 42.
[0037] Figure 4 shows a side view of a nozzle 52, with a portion of propellant 51, which
when combusted, provides gas flow 53.
1. An extended range artillery projectile having forward end comprising a fuze, an aft
located base unit, located therebetween a projectile body defining cavity which comprises
a payload, and a forwardly located gas generator capable of generating a gas flow,
said gas generator comprising an ignition device to activate the gas generator.
2. A projectile according to claim 1 wherein the forwardly located gas generator is
located between the fuze and the projectile body.
3. A projectile according to claim 1 or claim 2 wherein the forwardly located gas generator
is located on the ogive section between the fuze and the projectile body.
4. A projectile according to any one of the preceding claims wherein the gas flow is
directed along the outer surface of the projectile body.
5. A projectile according to claim 4, wherein the gas flow is directed substantially
rearwardly towards the aft base unit of the projectile.
6. A projectile according to any one of the preceding claims, wherein the gas flow generator
comprises at least one nozzle.
7. A projectile according to claim 6 wherein the gas generator comprises a plurality
of nozzles equidistant around the circumference of the projectile.
8. A projectile according to claim 7, wherein the plurality of nozzles are each capable
of being independently activated, so as to provide directional control by causing
an unsymmetrical gas flow.
9. A projectile according to any one of claims 6 to 8, wherein the at least one nozzle
is a directionable nozzle.
10. A projectile according to any one of the preceding claims wherein the gas generator
provides a portion of gas flow which is substantially normal to the projectile, to
increase air resistance.
11. A method of controlling the trajectory of a projectile, as defined in any one of
claims 1 to 10, during flight, comprising the steps of activating the gas generator,
directing the gas flow so as to alter said trajectory.
11. A device substantially as described herein with reference to the accompanying drawings.