U.S. patent application number 10/450063 was filed with the patent office on 2004-01-22 for infra-red emitting decoy flare.
Invention is credited to Callaway, James Dominic, Sutlief, Timoth Douglas.
Application Number | 20040011235 10/450063 |
Document ID | / |
Family ID | 9886604 |
Filed Date | 2004-01-22 |
United States Patent
Application |
20040011235 |
Kind Code |
A1 |
Callaway, James Dominic ; et
al. |
January 22, 2004 |
Infra-red emitting decoy flare
Abstract
An infra-red emitting decoy flare capable of diverting an
incoming missile equipped with a counter-countermeasures system
away from an intended target consisting of a primer flare (2), a
spectral flare (4) and a means for igniting the primer flare (22,
30), all contained within a flare casing (6). The primer flare (2)
is formed from a fast burning pyrotechnic composition and is
adapted to produce an intense infra-red source of short duration on
ignition. The spectral flare (4) is ignited by the burning of the
primer flare (2) and is adapted to produce a slower burning
composition having a fixed ratio in the intensity of infra-red
radiation emitted, when burning, in at least two fixed bands.
Inventors: |
Callaway, James Dominic;
(Salisbury, GB) ; Sutlief, Timoth Douglas;
(Salisbury, GB) |
Correspondence
Address: |
JOHN S. PRATT, ESQ
KILPATRICK STOCKTON, LLP
1100 PEACHTREE STREET
SUITE 2800
ATLANTA
GA
30309
US
|
Family ID: |
9886604 |
Appl. No.: |
10/450063 |
Filed: |
June 9, 2003 |
PCT Filed: |
December 13, 2000 |
PCT NO: |
PCT/GB00/04762 |
Current U.S.
Class: |
102/336 |
Current CPC
Class: |
F42B 12/70 20130101;
F42B 4/26 20130101; F41J 2/02 20130101 |
Class at
Publication: |
102/336 |
International
Class: |
F42B 004/26 |
Claims
1. An infra-red emitting decoy flare comprising a flare casing (6),
two pyrotechnic components housed within the flare casing and an
ignition means (30) for igniting the pyrotechnic components
characterised in that the two pyrotechnic components comprise a
primer flare (2; 50) and a spectral flare (4) wherein the primer
flare (2; 50) consists of at least one primer pellet (8; 42; 52),
each primer pellet being composed of a fast burning pyrotechnic
composition and being adapted such that, in use, ignition of one
primer pellet causes rapid ignition of all the primer pellets to
produce an intense infra-red source, wherein the spectral flare (4)
consists of at least one spectral pellet (10), each spectral pellet
being of a pyrotechnic composition adapted such that, in use,
ignition of the spectral pellets produces a spectral infra-red
source wherein the ratio of the intensity of the infra-red spectrum
at at least two fixed bands is within a fixed range, and wherein
the primer flare (2; 50) and spectral flare (4) are adapted such
that, in use, the spectral flare (4) is still burning after the
primer flare (2; 50) has finished burning.
2. An infra-red emitting decoy flare as claimed in claim 1 wherein
the spectral flare (4) is adapted such that the intensity of the
infra-red radiation emitted, in use, is greater than that normally
emitted from an intended target.
3. An infra-red emitting decoy flare as claimed in claim 1 or claim
2 wherein the primer flare (2) comprises a stack of discs (8) of a
pyrotechnic composition.
4. An infra-red emitting decoy flare as claimed in any preceding
claim wherein the primer flare (2) is provided with a central hole
(12).
5. An infra-red emitting decoy flare as claimed in any of the
preceding claims wherein the primer flare (2) is provided with a
plurality of holes (44).
6. An infra-red emitting decoy flare as claimed in any of claims 1
to 4 wherein the primer flare (50) has a plurality of grooves (54)
in its surface.
7. An infra-red emitting decoy flare as claimed in any preceding
claim wherein the burn time of the primer flare (2; 50) is within
the range of 100 to 600 ms.
8. An infra-red emitting decoy flare as claimed in claim 7 wherein
the burn time of the primer flare (2; 50) is in the range of 150 to
250 ms.
9. An infra-red emitting decoy flare as claimed in any preceding
claim wherein the spectral flare (4) comprises a single pellet
(10).
10. An infra-red emitting decoy flare as claimed in claim 9 wherein
the spectral flare (4) is provided with a central hole (14).
11. An infra-red emitting decoy flare as claimed in any preceding
claim wherein the spectral flare (4) and primer flare (2; 50) are
adapted such that, in use, the spectral flare is ignited by the
burning of the primer flare
12. An infra-red emitting decoy flare as claimed in any preceding
claim wherein the primer flare (2; 50) is formed from a fast
burning magnesium-Teflon-Viton composition.
13. An infra-red emitting decoy flare as claimed in any of claims
1-11 wherein the primer flare (2; 50) is formed from a pyrotechnic
composition adapted such that, in use, ignition of the primer
pellet produces an intense spectral infra-red source wherein the
ratio of the intensity of the infra-red spectrum at at least two
fixed bands is within a fixed range.
14. An infra-red emitting decoy flare as claimed in claim 13
wherein the primer flare (2; 50) is comprised from a composition of
potassium benzoate, potassium perchlorate and a binder chosen from
the group of RDX, HMX or HNS.
15. An infra-red emitting decoy flare as claimed in any preceding
claim wherein the spectral flare (4) is formed from a pyrotechnic
composition which produces quantities of gas on ignition.
16. An infra-red emitting decoy flare as claimed in any preceding
claim wherein the spectral flare (4) is formed from a composition
having an organic fuel, an oxidant and a binder.
17. An infra-red emitting decoy flare as claimed in claim 16
wherein the organic fuel is chosen from the group comprising
sucrose, lactose, starch and potassium benzoate.
18. An infra-red emitting decoy flare as claimed in any of claims 1
to 15 wherein the spectral flare (4) is formed from a composition
having a boron fuel, an oxidant and a binder.
19. An infra-red emitting decoy flare as claimed in any of claims
16-18 wherein the oxidant is chosen from the group of potassium
perchlorate, potassium nitrate, sodium nitrate and ammonium
nitrate.
20. An infra-red emitting decoy flare as claimed in any of claims
16-19 wherein the binder is chosen from the group of Viton A,
dextrin or polybutyl rubber.
21. An infra-red emitting decoy flare as claimed in any of claims
16-19 wherein the binder is an explosive material having a waxy
composition.
22. An infra-red emitting decoy flare as claimed in claim 21
wherein the binder is chosen from the group of RDX, IMX and
HNS.
23. An infra-red emitting decoy flare as claimed in claim 1 wherein
the spectral flare composition (4) is formed from a mix of 30-40%
by mass of potassium benzoate and 60-70% by mass of potassium
perchlorate together with 3-8% by mass of Viton A, RDX, HMX or
HNS.
24. An infra-red emitting decoy flare as claimed in claim 1 wherein
the spectral flare composition (4) is formed from a mix of 30% by
mass of boron and 70% by mass of potassium nitrate together with a
Viton A binder.
25. An infra-red emitting decoy flare as claimed in any of claim 18
wherein the spectral flare composition (4) comprises an additive
such as silicon.
26. An infra-red emitting decoy flare as claimed in claim 25
wherein the spectral flare composition (4) is formed from a mix of
20% by mass of boron, 10% by mass of silicon and 70% by mass of
potassium nitrate together with a Viton A binder.
Description
[0001] This invention relates to an infra-red (IR) emitting decoy
flare capable of being launched from a target to divert a missile
equipped with an IR seeker system away from that target, and
particularly to an IR emitting decoy flare capable of diverting a
missile having a seeker operating with a counter-countermeasures
(CCM) system using a spectral discriminator.
[0002] Most infra-red seeker systems operate in a certain
wavelength range, or band, of the infra-red spectrum. In this band,
the radiated energy from non natural sources is generally easy to
detect and the hot components of aircraft exhausts or tank engines,
for example, radiate strongly, enabling targets to be easily
identified and located.
[0003] Known decoy flares conventionally comprise pyrotechnic
compositions bound together with an organic binder and pressed to
form pellets. When an incoming missile is detected a pellet is
launched from the target and ignited. The pellet burns over its
surface to produce an intense infra-red source in this band, which
can lure the infra-red seeker system of the missile away from the
target.
[0004] UK patent application GB 2,300,035 describes an infra-red
decoy flare which is formed from a pyrotechnic composition which
burns to emit infra-red radiation. The composition is formed into a
plurality of different blocks with different volumes and different
surface areas so as to have different rates of burning. Ignition of
all the blocks produces an infra-red source which is intense enough
to cause the missile to lock onto the flare. After a short time the
aircraft will be outside of the field of view of the missile and
some of the fast burning blocks will burn completely away. The
flare will then radiate comparatively weak radiation for a time in
order to complete the diversion of the missile.
[0005] However, advances in missile seeker systems and CCM systems
have led to seeker systems being able to recognise a decoy flare
and ignore it. Some advanced seeker systems are equipped with CCM
systems that compare the ratio of the intensity of IR radiation in
one band with the intensity of IR radiation in another band of the
IR spectrum. Due to the temperature difference between a
conventional flare and the radiating parts of a typical target and
the corresponding different `grey body` radiation spectrums, the
CCM system can identify and disregard the flare.
[0006] It is therefore an object of the invention to provide a
decoy flare which alleviates at least some of the aforementioned
disadvantages and which is capable of diverting a missile equipped
with an infra-red seeker system and a spectral
counter-countermeasures system away from its intended target.
[0007] Thus according to the present invention there is provided an
infra-red emitting decoy flare comprising a flare casing, two
pyrotechnic components housed within the flare casing and an
ignition means for igniting the pyrotechnic components
characterised in that the two pyrotechnic components comprise a
primer flare and a spectral flare wherein the primer flare consists
of at least one primer pellet, each primer pellet being composed of
a fast burning pyrotechnic composition and being adapted such that,
in use, ignition of one primer pellet causes rapid ignition of all
the primer pellets to produce an intense infra-red source, wherein
the spectral flare consists of at least one spectral pellet, each
spectral pellet being of a pyrotechnic composition adapted such
that, in use, ignition of the spectral pellets produces a spectral
infra-red source wherein the ratio of the intensity of the
infra-red. spectrum at at least two fixed bands is within a fixed
range, and wherein the primer flare and spectral flare are adapted
such that, in use, the spectral flare is still burning after the
primer flare has finished burning.
[0008] In use, the ignition of the primer flare creates an intense
IR source of short duration. The sudden increase in energy can
trigger a missile's CCM system. Due to the short duration of
burning of the primer flare however, by the time the missile's CCM
system is active the primer flare will have stopped burning but the
spectral flare will still be burning. The spectral flare has
pre-set ratios of intensity between different bands of the IR
spectrum and therefore appears to the missile's CCM system to have
the intensity ratios that an intended target would have. Indeed,
due to the varying aspects that a target may present to a missile
seeker and the fact that the ratio of intensities of the different
bands alters when viewing a target from a different angle, say an
aircraft head on as oppose from the rear, the spectral flare may be
judged by the missile seeker and CCM system to be more target like,
in terms of the required ratio of intensities at different bands,
than the actual target itself.
[0009] Preferably the spectral flare is adapted such that at the
fixed bands of the IR spectrum the flare is more intense than the
intended target. The spectral flare will then be the most intense
IR source with the correct spectral characteristics. Further, the
very intense radiation from the primer flare can saturate some
missiles seeker systems. This would not only cause a missile to
activate its spectral CCM system but could also cause automatic
brightness compensators to come into operation. After the primer
flare has stopped burning the automatic compensators will start to
reduce to their previous levels. However, if the intensity of the
spectral flare in the bands measured by the missile is greater than
that of the intended target then the intensity compensators of the
missile seeker may not reduce to a level that would include the
target. Therefore the spectral flare will be the only object with
the correct spectral characteristics in the field of view of the
missile.
[0010] Also, on initial ejection the primer pellet lights up and
burns extremely quickly. Thus the flare will still be close to the
target on ignition and energy from the burning flare will be
reflected from the surface of the target. This can increase the
radiation seen by the missile's seeker system. Further, the
radiation reflected from the target can cause the target to appear
to be flare like to the seeker system thus prompting the missile to
actually ignore the target.
[0011] In order to achieve a fast burn rate the primer pellets are
preferably discs and the primer flare consists of a stack of said
discs. By dividing the primer flare into discs the surface area
available for burning is increased over that of a single pellet of
the same dimensions as the stack. The burn rate is therefore
correspondingly increased. The discs are also preferably provided
with a central hole which again increases the burn rate, but also
aids in rapid ignition of the primer flare by allowing the passage
of hot particles through the stack. Alternatively a single primer
pellet is used and is provided with plurality of holes through the
pellet. This again increases the surface area for burning and
increases the burn rate. Another means of increasing the burn rate
is providing the primer pellet or pellets with deep grooves to
create more burning surface area. Other arrangements for the primer
pellet will be readily apparent to the skilled addressee.
[0012] A fast burn time is required so that the primer flare has
finished burning by the time that the seeker system has adjusted.
The burn time of the primer flare is therefore preferably between
100-600 ms, more preferably between 150-250 ms. Too short a burn
time however can reduce the efficiency of the primer flare as there
would be insufficient time for efficient combustion processes to
occur.
[0013] The primer flare is conveniently comprised of a composition
of an oxidisable metallic material, an oxidising halogenated
polymeric material and an organic binder. Suitable metallic fuels
are well known in the art and include magnesium, aluminium, alloys
of magnesium or aluminium, titanium, boron and zirconium.
Preferable the oxidisable metallic material is magnesium. When
ignited magnesium undergoes an energetic and vigorous exothermic
reaction with halogenated polymers and therefore is particularly
suitable for the heat and speed of combustion required.
[0014] Similarly the oxidising halogenated polymeric material used
in preferred compositions for the primer flare is a fluorinated
polymer because fluorine is a better oxidising agent than other
halogens and therefore will react more vigorously and create a more
intense IR source. Suitable fluorinated polymers include
polytetrafluoroethylene (Teflon (.TM.) or PTFE) and its copolymers
with perfluoropropylene, polytrifluorochloroethylene, copolymers of
trifluoroethylene with vinylidene fluoride, homopolymers of
perfluoropropylene and copolymers of perfluoropropylene with
vinylidene fluoride, homopolymers of hexafluoropropylene and
copolymers of hexafluoropropylene with vinylidene fluoride. PTFE is
particularly suitable as it has a high percentage of fluorine in
it.
[0015] Suitable organic binders are well known in the art and
include polyvinylchloride, straight chain chlorinated paraffins
such as Alloprene (.TM.) or Cereclors (.TM.) and the tripolymer of
vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene.
Fluorinated organic binders are advantageous in that the binder,
also being an oxidising agent, will join in the reaction. A
preferred binder is a copolymer of vinylidene fluoride and
hexafluoroethylene, for example VITON A (.TM.), which coats and
binds the constituents very well as well as adding to the
reaction.
[0016] A preferred composition for the primer flare is therefore a
magnesium-Teflon-Viton (MTV) composition. The ratio of the
constituents will be chosen so that there is the smallest amount of
unreacted material after combustion, allowing for the amount of
atmospheric oxygen present that will join in the reaction in a
particular flare application. The ratio of the constituents will be
easily determined by the skilled person.
[0017] As the spectral flare needs to have a longer burn time than
the primer flare the spectral flare may usefully be formed from a
single pellet. The spectral pellet can therefore burn relatively
slowly and consistently.
[0018] In order to ensure that the intensity of the spectral flare
is bright enough the spectral pellet may be provided with a central
hole through the pellet. The hole will not only increase the
intensity of the radiation from the spectral pellet by providing an
internal burning surface but with also ensure consistency of the
radiation. As the intensity of the flare is related to the surface
area of the burning pellet, a pellet burning from the outside only
will slowly drop in intensity as the surface area of burning
decreases. Having a central hole, however, means that as the
outside surface area of burning decreases, the internal burning
surface increases, resulting in a relatively consistent burn,
increasing the viability of a flare to be mistaken as the target by
the missile system. A central hole will also aid in rapid and
consistent ignition of the whole of the spectral flare.
[0019] Conveniently the spectral flare and primer flare may be
adapted such that, in use, the spectral flare is ignited by the
burning of the primer flare.
[0020] The spectral pellet may advantageously be formed to produce
quantities of hot gas. Conveniently the spectral pellet may be
formed from an organic fuel, an oxidant and a binder. Organic fuels
decompose to produce gases such as carbon dioxide which can be
similar to the elements produced by an aircraft engine say. Thus
use of an organic fuel can provide the required spectral
characteristics. Suitable fuels include organic compounds such as
sucrose, lactose or starch and also compounds such as potassium
benzoate. As an alternative to organic fuels the spectral pellet
may be formed from a boron fuel with a suitable oxidant and
binder.
[0021] Suitable oxidants include potassium perchlorate, potassium
nitrate, sodium nitrate or ammonium nitrate. Suitable binders
include Viton A, dextrin or polybutyl rubber although organic
binders are preferred as again they decompose into relevant gasses
thus binders such as Viton A or GAP are preferred. Particularly
advantageously however explosive materials with a waxy composition
may be used as binders. Such explosives will be able to function as
binders due to their consistency and will add to the energetic
reaction on ignition. Suitable explosives include RDX, HMX and HNS
and can also add to the hot gasses produced by the fuel and
oxidant. Other oxidants and binders may be used however and could
be easily determined by the skilled person.
[0022] One advantageous spectral composition comprise approximately
30% by weight potassium benzoate, 65% by weight potassium
perchlorate and 5% by weight of binder, say Viton A or RDX.
[0023] Another advantageous spectral composition has, excluding
binder, approximately 30% by mass of boron and 70% by mass of
potassium nitrate, with Viton A as a binder in a sufficient amount
as could be easily determined by one skilled in the art. The
composition may also include other materials to enhance the
spectral effect, Another advantageous composition has, again
excluding binder, 20% by mass of boron fuel with 70% potassium
nitrate and 10% by mass of silicon.
[0024] In some instances it will be beneficial that the primer
flare burn with some visible component or without a spectral
characteristic, say when utilising reflection from the target
surface. However, in other circumstances it would be advantageous
that the primer flare also burn with a spectral component. In such
instances the primer flare may comprise a fast burning spectral
composition. The actual composition could be the same as could be
used or the spectral pellet but to ensure a fast light up and
generation of sufficient energy grooves or a plurality of discs
would be used and smaller particle sizes would be used as is well
understood in the art. Explosive binders would preferably be used
to add to the intensity produced by the primer pellet.
[0025] Further advantages and embodiments of the invention will now
be described by reference to the accompanying drawing in which:
[0026] FIG. 1 shows a decoy flare according to an embodiment of the
invention,
[0027] FIG. 2 shows the spectral and primer flares used in a decoy
shown in FIG. 1,
[0028] FIG. 3 shows the IR intensity against time for a decoy flare
such as shown in FIG. 1,
[0029] FIG. 4 shows a primer flare pellet according to an
alternative embodiment of the invention,
[0030] FIG. 5 shows a primer flare pellet of a further embodiment
of the present invention.
[0031] Referring to FIG. 1 a primer flare 2 and a spectral flare 4
are housed in an open ended cylindrical flare casing 6. The
spectral flare is made up of a single cylindrical spectral pellet
10 housed at the closed end of the casing whereas the primer flare
2 comprises a stack of primer pellet discs 8 located next to the
open end. Each of the primer pellets discs 8 and the spectral
pellet 10 are provided with a central hole, 12 & 14
respectively, extending throughout the pellets.
[0032] The open end of the casing 6 is sealed by a plug 16, the
plug being secured by crimping the rim 18 of the casing 6 into a
groove 24 in the plug 16. An expulsion charge 20 is located in a
recess in the outside face of the plug, as is a primary ignition
charge 22.
[0033] In use, expulsion charge 20 and primary ignition charge 22
are ignited, for example by conventional electric igniters (not
shown) in the flare tube of the target. The expulsion charge 20 is
formed from a propellant compositions such as a gunpowder or
nitrocellulose composition and on ignition generates a large volume
of gas which projects the flare from the flare tube (not
shown).
[0034] Once clear of the flare tube, spring 26 is released and
allows the ignition stimulus from primary ignition charge 22 to
travel down the channel 28 and ignite the secondary ignition charge
30. Should the flare casing 6 become jammed in the flare tube,
spring 26 is prevented from release and therefore stops the
propagation of the ignition stimulus, thereby preventing ignition
of the flare in the flare tube.
[0035] Ignition of the secondary ignition charge 30 provides a
source of ignition for the primer flare 2. The outer and inner
surfaces of the primer flare 2 and spectral flare 4 are also coated
in a primer paste to further aid ignition. Further, the primer
flare 2, and also the spectral flare 4, are wrapped in aluminium
foil 32 and 34 respectively, with both flares being then wrapped
together in aluminium foil 38. The aluminium foil aids the ignition
of the primer flare 2 and spectral flare 4 by initially confining
the ignition gases thus increasing the initial pressure and thereby
aiding the speed and reliability of the ignition stimulus. Wrapping
the pellets in aluminium foil also helps to protect the pellets
during storage. The high temperature generated during burning of
the primer flare 2 may additionally cause the aluminium foil to
combust, adding to the radiation from the primer flare 2.
[0036] Ignition of the primed surfaces of the primer flare 2 cause
the primer flare to be very rapidly ignited over all of its outer
surface. Hot particles and combustion gases also travel down the
central hole 12 igniting the inner surface and the faces between
the primer pellet discs 8. This is aided by the confining effect of
the aluminium foil 32.
[0037] The primer pellet discs 8, shown more clearly in FIG. 2; are
formed from a fast burning composition such as a composition of
MTV. Such a composition creates an intense source of IR radiation
having a fast burn rate and reaches temperatures of 1900.degree.
C.
[0038] The burn rate of the primer flare is also determined by the
thickness of the primer pellet discs 8. For an MTV primer pellet
composition where the discs are of 47 mm diameter and have a
central hole of 6 mm diameter, a stack of 4 to 8 discs of thickness
5-10 mm give the desired burn rates.
[0039] Alternatively the primer pellet could be formed from a
similar stack of discs formed from a composition of potassium
benzoate and potassium perchlorate of small particle size and RDX
as a binder.
[0040] Referring back to FIG. 1, ignition of the primer flare 2
causes ignition of the spectral flare 4 which is wrapped in
aluminium foil 34. Spacers 36 are located between the primer flare
2 and the spectral flare 4. This allows for hot particles produced
from the burning of the primer flare 2 to ignite the spectral flare
over its surface. The spacers 36 also help prevent premature
ignition due to friction during launch or transit.
[0041] In an alternative embodiment (not shown) an ignition
transfer medium, such as an MTV cord, could be located next to the
secondary ignition charge 30 and run through the hole 12 in the
primer flare 2 and the hole 14 of the spectral flare 4. Ignition of
the secondary ignition charge 30 could then ignite the ignition
transfer medium which would burn down its length igniting the
interior surfaces of the primer flare 2 and the spectral flare 4 in
turn.
[0042] The spectral pellet, also shown in FIG. 2, is formed from a
single cylindrical pellet. The composition may conveniently be a
potassium benzoate, potassium perchlorate and Viton A mix.
Potassium benzoate comprises 30% by mass of the spectral pellet
with 65% potassium perchlorate and Viton A making up the rest of
the pellet. The fuel and oxidant have particle sizes of less then
60 microns.
[0043] Alternatively the spectral pellet can be formed from a
boron, potassium nitrate, Viton A mix. The potassium nitrate is 70%
by mass of the composition and has a typical particle size of 100
.mu.m. The boron is amorphous and sub-micron size and makes up 30%
by mass of the composition or 20% by mass if an additive like
silicon is used. If used, the silicon particles are around 10 .mu.m
in size. Boron, potassium nitrate and Viton A gives a hard
composition which may be easily cast into the required pellet
shapes. Use of a binder such as polybutyl rubber would lead to a
more flexible composition which could, for example, be
extruded.
[0044] As the spectral flare 4 is formed from a single cylinder the
burn rate is much slower than that of the primer flare 2 and due to
the central hole 14, the intensity of the spectral flare 4 is
substantially constant throughout the duration of burning.
[0045] FIG. 3 shows a plot of the IR intensity against time for a
decoy flare as shown in FIG. 1 for two fixed IR bands. The primer
flare was 47 mm in diameter and 40 mm in length, consisting of 8
discs, each 5 mm thick, formed from an MTV composition. The
spectral flare was a single pellet of a potassium benzoate,
potassium perchlorate, Viton A mix and was 47 mm in diameter and
was 110 mm in length. Both the primer flare and the spectral flare
were provided with a central hole 6 mm in diameter.
[0046] It can be seen that as the primer flare ignites there is a
rapid increase in intensity to a very intense peak which rapidly
drops away again. The duration of burning of the primer flare can
be seen to be in the region of 200 ms. It can also be seen that one
IR band is very much more intense than the other. This is the
situation with conventional flares but not with targets such as
aircraft. After the primer flare has finished burning it can be
seen that the spectral flare is already burning and that the
intensity of both bands drop off to a lower level. However, the
band which was, during burning of the primer flare, of lower
intensity is now of greater intensity, which is the opposite
situation to what would be expected for a conventional decoy and is
similar to what the output from the target would be. This occurs a
few hundred milliseconds after the primer flare ignited and
therefore solely the spectral flare will be burning by the time the
spectral discriminator of a missile's CCM system will have been
activated.
[0047] It can be seen that the spectral flare burns with relatively
consistent intensity in both bands for a few seconds, more than
long enough for the target to be well outside the missile's field
of view when the flare finally stops burning.
[0048] FIGS. 4 & 5 show alternative embodiments of a primer
flare suitable for use in decoy flare according to the present
invention. Where appropriate like numerals have been used to
designate like components.
[0049] Referring to FIG. 4 the primer flare 2 is formed from a
single cylindrical pellet 42 having a central hole 12. The pellet
42 is also provide with a number of other holes 44 which pass
through the pellet, the inside surfaces of the central hole 12 and
the holes 42 being coated with a primer paste to aid in ignition.
The use of a single pellet with a number of holes can simplify the
production of the primer flare as a single pellet can be easily
machined, however the loss of material from the primer flare could
necessitate the use of a larger pellet, depending upon the
application.
[0050] For a 47 mm diameter and 40 mm long primer flare made from
an MTV composition the desired burn rate can be achieved with one
central hole 12 and five surrounding holes 42, each hole being of 6
mm diameter. Additionally or alternatively transverse holes could
be provided down the length of the primer pellet.
[0051] FIG. 5 shows an a rectangular primer flare 50 comprising a
single pellet with a central hole 52 and a number of grooves 54
running down the length of the pellet. The grooves may be a few mm
thick and about 15 mm deep depending upon the application and may
be filled with primer paste to aid ignition.
* * * * *