Note: Descriptions are shown in the official language in which they were submitted.
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COMPACT DEPLOYMENT AND RETRIEVAL SYSTEM FOR A TOWED
DECOY UTILIZING A SINGLE CABLE EMPLOYING FIBER OPTICS.
FIELD OF INVENTION
This invention relates to towed vehicles and more particularly to a compact
system
for deploying and retrieving towed decoys so that they can be redeployed
multiple times.
BACKGROUND OF THE INVENTION
As will be appreciated, aerial towed objects are used for a variety of
purposes,
including decoys, testing, and scientific investigations. In one embodiment,
these decoys
are used to draw various types of guided weapons away from an aircraft that
the weapons
are intended to destroy. As will be appreciated, these towed targets and
decoys contain
various types of electronic circuits to create an apparent target to a weapon
to attract the
weapon to the decoy rather than the aircraft. One active electronic device
used in a decoy
is a traveling wave tube amplifier to which high voltages must be applied to
power the
traveling wave tube. Additionally, other controls for the traveling wave tube
or other
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electronics in the towed device are transmitted in one embodiment along a
fiber optic
transmission line, which is both frangible and fragile.
In the typical military operation, the decoys are sacrificed, meaning that the
cables
that attach the decoy to the deployment canister are severed after the decoy
has been used.
The practice of cutting decoys after use and using them as an expendable
commodity causes multiple problems. As a result it becomes important to be
able to
recover the towed vehicle itself, mainly because of the cost of the towed
vehicle, as well as
the fact that replacing towed vehicles often is difficult due to the long lead
times in the
manufacturing process and provision of such decoys.
For instance, typically a towed countermeasure decoy may cost as much as
$50,000
per decoy round. As many as eight decoys per sortie or mission can be deployed
and as
such, assuming 400 sorties per month, then the total expense of deploying
expendable
decoys is quite large, making the cost for the protection of the aircraft that
employ these
decoys excessive. Moreover, in a wartime setting, the decoy cannot be
manufactured
quickly enough. So bad is the situation that it may be necessary to scrounge
decoys from
the battlefield where they fall for reuse.
There is therefore a necessity for being able to deploy a towed decoy in such
a
manner that it can be powered and controlled during the countermeasure
operation, while
at the same time, being able to be retrieved and reused again.
.20 In the past, attempts to deploy such decoys in a rapid manner liave
included a
spinning reel-like spindle payout system in which the decoy is paid out behind
the aircraft
without the ability to winch it back in.
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It will be appreciated that priorly the only airborne towed devices that were
winched into the aircraft after use were sonobuoys or towed instruments
deployed from
helicopters in which the winching systems themselves occupied inordinate
amounts of
space. As such, these devices were unsuitable for combat aircraft due to the
current volume
constraints on tactical aircraft. Thus, due to both the size and problems with
slowly
winching out a towed vehicle, no such winching systems were applied to the
towed decoys
for combat.
It is noted that sonobuoys and pod-mounted countermeasures were typically
carried
in an equipment pod the size of an MK-84 aerial bomb or the ALQ-164 type
electronics
counter-measures pod. What will be appreciated is that these pods are
exceptionally large
and preclude, for instance, the carrying of armaments in the position where
the pod is
located. Thus the payload of any attack aircraft would be severely limited if
unwieldy
winching systems such as associated with sonobuoys along with the associated
housing
were used to deploy normal decoy rounds. Note that prior art winding systems
occupied a
space many times the size of the normal decoy round.
By way of further background, the types of decoys involved have included
devices
which countermeasure infrared guided and radar guided missiles that pose the
primary
threats to military aircraft engaged in a combat environment. It will be
appreciated that
these missiles use their radar guidance systems to get within striking
distance of the
aircraft, thereby substantially increasing their probability that the IR
systein on the missile
will be able to lock onto the target.
Current military aircraft are particularly vulnerable to attack from IR-guided
surface-to-air and air-to-air missiles. Statistical data of aircraft losses in
hostile actions
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since 1980 show that almost 90 percent of these losses have been the result of
IR-guided
missile attacks. As a result, the ability to deploy and then recover decoys
that can counter-
measure the IR guidance systems on these missiles is of great value to protect
aircraft
during combat situations. As mentioned above, the IR-guided system initially
utilizes radar
guidance and then switches over to IR guidance as they come into closer
proximity to the
target. If one can counter-measure the radar system, then the IR portion can
never lock
onto the particular infrared target. To do this, the missile is deflected away
by generating a
signal that causes the radar guidance system in the missile to think that the
target is
actually elsewhere than it actually is.
In the past, the ALE-50 Towed Decoy system currently in the inventory of the
US
Armed Forces includes a decoy round in a canister and a reel payout mechanism.
When
the decoy has served its purpose, it is cut loose and the ALE-50 decoy is
lost.
Moreover, the same scenario is true for the more modem ALE-55, or in fact, any
type of expendable towed vehicle.
In summary, prior art decoys were intended to be sacrificed and the towline
was
typically cut at the aircraft at the end of flight or mission. Thus, these
systems did not
contemplate the winching in or reeling in of the decoy. The reason is because
these decoys
needed to be rapidly deployed. One rapid deployment method included a spindle
that paid
out the towline in much the same way as a spinning reel pays out fishing line.
Although
.20 spinning reel-like techniques have existed for fishing, in the area of
rapidly deployed
decoys they were not used to winch decoys. Also, the spindles themselves were
not
necessarily driven.
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As will be appreciated, there are a number of US patents that in general cover
towed vehicle deployment, such as US Patents 5,836,535; 5,603,470; 5,605,306;
5,570,854; 5,501,411; 5,333,814; 5,094,405; 5,102,063; 5,136,295; 4,808,999;
4,978,086;
5,029,773; 5,020,742; 3,987,746 and 5,014,997. In none of these patents is the
subject
retrievable system shown or taught.
SUMMARY OF THE INVENTION
In order to deploy, retrieve and reuse towed decoys, in the subject system,
the
decoy is housed in a canister with a towline wound around a level winding
winching
system, which during the deployment of the decoy, winches out the decoy at a
moderately
high speed. In the subject system, both the high voltage electrical signals to
the traveling
wave tube within the decoy and the controls for the countermeasure system
carried by the
decoy are transmitted over an electro-optic cable into which is embedded a
length of high
voltage tension line to be able to power the traveling wave tube. In one
embodiment, there
are five lines that carry a voltage, including three at high voltage, one at
low voltage and a
ground. The signals to control the countermeasure device within the decoy are
carried by
the relatively fragile fiber optic cable, which, in one embodiment, is
connected to drive
circuitry through a fiber optic rotary joint, such that the decoy can be
winched out and
retrieved with the signals passing through the center shaft of the level
winding winching
system. Additionally, high voltage slip rings are utilized along with the
fiber optic rotary
joint such that all the necessary signals and voltages can be applied to the
decoy without
any twisting of lines. It will be appreciated that in winching systems where
the same line
is utilized which winches the decoy in and out and is utilized for signal
transmission,
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twisting inevitably occurs, which would damage both the fiber optic cable and
the high
voltage transmission lines.
In the past when towed decoys were deployed in the so-called spimling reel
type of
environment, the amount of twist imparted to the cable itself was not
sufficient to cause
damage to the cables.
However, when considering a fully-winched system, it is important to consider
how
it is that the cables can be deployed without fracture or injury, thus to
permit multiple
deployments.
As part of the subject invention, the feeding of the line from and to the
level winding
winching system is accomplished with means to prevent backlash and jamming of
the line
during the retrieval process, as well as damage to the line during deployment.
Secondly,
the tension of the line during the retrieval process is continuously monitored
so that
excessive loads are avoided.
Central to the subject invention is a telescoping or extensible cradle or
saddle
which is extended after deployment of the decoy and which is utilized to
capture the
retrieved decov as it is reeled in. After the decoy has reached its captured
position, the
entire telescoping assembly is retracted such that the decoy and the assembly
are retracted
into the canister from which the decoy can be redeployed.
The result is a decoy deployment system which can be used multiple times, due
to
the fact that the deployed decoy is captured and stored in the original
canister. Secondly,
multiple deployments of the decoy do not result in damage to the single towing
line such
that through the utilization of the fiber optic rotary joint, high voltage
slip rings and the
level winder traverse mechanism, decoys can be carried on an aircraft in a
space that is
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one-tenth the size of prior equipment pods and at the same time permits the
decoy to be deployed and redeployed even during the same mission.
In summary, a decoy deployment and retrieval system includes an
extensible boom and corresponding cradle or saddle for use in the retrieval of
the
towed decoy such that upon retrieval the extensible boom with its decoy
captured
in the cradle is retracted into a chamber so that the decoy can be deployed
over
and over again. In one embodiment, the decoy is both towed by and controlled
over a fiber optic line in which a load cell is used to detect tension on the
line to
prevent damage, and a fiber optic rotary joint is utilized along with high
voltage slip
rings to permit electrical and optical coupling without backlash, fouling, or
damage
to the line.
In one broad aspect, there is provided a decoy deployment and
retrieval system for a decoy tethered by a towing cable, comprising: a
canister for
housing and deploying said decoy, said canister including an extensible boom
having a cradle for capturing said decoy upon retrieval and translatable from
a
stowed position to a decoy retrieval position; a winch located in said
canister for
reeling in a deployed decoy by its towing cable for capture by said cradle;
and, an
actuator for extending said boom during retrieval and for withdrawing said
boom to
said stowed position after capture of said deployed decoy, whereby said decoy
is
restored for redeployment within said canister.
In another broad aspect, there is provided a decoy deployment and
retrieval system for a decoy tethered by a towing cable, comprising: a
canister for
housing and deploying said decoy; a level winding winching system having a
spindle about which said cable is wrapped; and, a drive coupled to said
spindle for
actuating said winch for paying out said cable during decoy deployment and for
reeling in said decoy during retrieval, said level winding winching system
operative
to pay out line at a controlled rate and for reeling in said line in a
backlash free
manner so as not to destroy said cable.
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BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the subject invention will be better understood in
connection with the Detailed Description in conjunction with the Drawings, of
which:
Figures 1 A and 1 B are diagrammatic representations of the deployment of a
prior
art decoy system, indicating the relative size of the equipment pod if used
for winching and
illustrating the cutting of the tow line after decoy deployment;
Figure 2 is a diagrammatic illustration of the canister utilized in the
deployment of
the decoy round indicating the storage thereof in a canister compartment above
level
winding deployment and retrieval apparatus;
Figure 3 is a diagrammatic illustration of the canister of Figure 2,
illustrating the
deployment of the telescoping boom or saddle for retrieving the decoy once
deployed,
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showing the capture of the decoy in the cradle or saddle prior to the
retraction of the boom
and the decoy into the canister;
Figure 4 is a schematic diagram of the deployment of the decoy in the system
of
Figures 1 and 2, in which a level winding spindle is shown driven through a
transmission
via motor under the control of a motor control unit which is in turn
responsive to a load
sensor that senses the tension on the tow line, also illustrating the
utilization of a fiber optic
rotary joint and a high voltage slip ring assembly; and,
Figure 5 is a diagrammatic and schematic representation of the retrieval
process
shown in Figure 3, indicating the utilization of a load cell and a spring-
loaded sheave in the
capture of the decoy, along with the drive for the telescoping boom.
DETAILED DESCRIPTION
Referring to Figure 1A, a typical attack aircraft 10 has in the past been
provided
with a decoy containing canister 12 from which a decoy 14 is deployed over a
tow line 16.
As can be seen from Figure 1 B, decoy 14 is cut loose from canister 12 after
the
countermeasure operation as indicated by the X, here illustrated at 18.
As has been mentioned above, these decoys were sacrificed and there was no
attempt to either winch them out or winch them in. Had there been such an
attempt
utilizing winching systems for sonobuoys, for instance, then the pod, here
illustrated by
line 20, would be clearly about 10 times the size of the canister necessary
for the
deployment of a decoy round.
This being the case, it was important to be able to provide a compact canister
for
both the deployment of the decoy and for retrieval in such a manner that the
decoy can be
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deployed multiple times even in the same mission. This would give the aircraft
the ability
to stay on station longer, without having to reload decoy rounds.
In the subject invention and referring now to Figure 2, a canister 30 is
illustrated as
housing a decoy round 32, shown in dotted outline, within a chamber 34 that
lies above a
level winding deployment and retraction system 36. As can be seen, canister 30
has a
framed aperture 38 through which the decoy round is deployed from whence it
streams aft
of the aircraft with a single tow line emanating from this aperture frame.
Referring now to Figure 3, during the retrieval process, an extensible boom 40
includes a decoy capture channel 42 which serves as a saddle or cradle for the
decoy when
it is reeled in via level winding system 36.
It is important to note that the boom is extended during the retrieval process
so as
to permit the capture of the deployed decoy as the decoy is reeled in. After
the decoy is
firmly secured to the saddle, the boom and decoy are retracted into chamber 34
by virtue of
the winding up of the single towline that is utilized. This is accomplished by
the electric
drive and lead screw 35 in Figures 2 and 3.
It is important during the deployment process that the decoy be released at a
moderately high speed, however controlled. It has been found that absent any
kind of
braking in prior art systems the single towline could break during deployment.
It is for this
reason that level winding apparatus 36 is utilized as a brake in the
controlled payout of the
towline to prevent wild gyrations of the decoy during deployment.
This sanie level winding system is utilized in the retrieval of the decoy,
with the
level winding mechanism assuring that the line as it is both paid out and
reeled in does so
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over a driven spindle in such a manner as to eliminate backlash, kinking and
other types of
jamming, which would cause the severing or damage to the single tow line.
Referring now to Figure 4, a spindle 50 is shown diagrammatically to carry
towline
16, which is passed over a number of sheaves, here diagrammatically
illustrated at 52. A
double helix rotating shaft 54 rotates at a predetermined speed and a
traversing wire guide
carrier 56 having an eyelet loop or other guiding mechanism 58 guides line 16
backwards
and forwards over the rotating spindle 50. As can be seen by dotted line 60,
the rotating
helically grooved shaft 54 is mechanically coupled to the spindle such that
the winding
pitch is mechanically controlled regardless of the speed with which the
spindle is rotating.
Here it can be seen that spindle 50 is coupled through a transmission 62 to a
motor 64
under the control of a motor control unit 66 so that the rate at which the tow
line is paid out
is controlled, as well as the rate of retrieval.
In order to provide the appropriate connections to the rather fragile single
tow
cable, a fiber optic rotary joint 70 is employed at the distal end 72 of
spindle 50 such that
signals 74 from a control unit 76 are passed through a fiber optic coupler 78
so as to be
able to control the traveling wave tube in towed decoy 14. Also attached in
the vicinity of
the fiber optic rotary joint are high voltage slip rings, here
diagrammatically illustrated at
80 to provide the appropriate power to the electronic apparatus in decoy 14.
It will be appreciated that there are several fiber optic rotary joints
available
commercially, such as those manufactured by Focal Technologies Corp. of Nova
Scotia,
Canada and Litten Polyscientific of Blacksburg, Virginia.
It will also be appreciated that level winding apparatus is known and
commercial
available level winders are provided by Norco Inc. of Ridgefield, Connecticut.
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Of particular importance in the subject system is a load cell 84 which is
utilized to
monitor the tension in line 16, especially during the retrieval process, but
also during
deployment. The purpose of the utilization of load cell 84, which is seen
coupled to motor
control unit 66, is to permit the driving of spindle 50 in such a manner to
eliminate overly
high rates of retrieval or deployment under high loads.
It will be appreciated that in certain operational situations, it is important
to be able
to pre-deploy a decoy and for this purpose a moderately slow deployed decoy is
appropriate. In this case, the subject system is utilized to pre-deploy the
decoy, with load
cell 84 providing information to the pilot via indicator 90 in case a certain
tension has been
exceeded. It may then be appropriate for the pilot to know that excessive
tension exists and
that it would either be impossible to reel in the decoy or that the motor
utilized may fuse
due to the overheating associated with high tensions. Indicator 90 may
therefore give the
pilot the option to slow down the aircraft to a point at which the level
winding mechanism
and associated motor can be used effectively to reel in the decoy, or a
decision can be
made to sacrifice the decoy in those cases where it would be inappropriate to
slow down
the aircraft.
Referring now to Figure 5, in one embodiment the telescoping capture unit,
here
illustrated as boom 40, is provided with load cell 84, which is in the path of
line 16 as it
goes over sheaves or pulleys 92, 94 and 96 onto spindle 50 as described above.
Here will
be appreciated that line 16 goes over a sheave 100, which is spring-loaded at
102 and then
over the load cell so that its tension can be ascertained.
The purpose of the spring-loaded sheave is to provide necessary compliance
during
the decoy docking operations.
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In this figure, it will be seen that the retrieved decoy 14 is carried in a
saddle 104
with unit 40 being provided with a butt plate 106 so that as the decoy is
reeled in, its nose
108 butts against the surface of butt plate 106, thereby to effectuate
capture. As illustrated
at 110, the telescoping capture unit 40 is driven by a drive 110 such that it
moves in the
direction of arrow 112 until such time that it and the retrieved decoy are in
the stowed
position indicated by dotted line 14'.
It will be appreciated that in one embodiment, the telescoping capture unit 40
is
deployed only when the decoy is within a predetermined distance of the
canister. Since the
towline 16 in any event goes over and through sheaves or pulleys carried by
the boom, in
order to eliminate excessive damage to the telescoping member due to the
whipping
around of the decoy, it is only when the decoy, for instance, is within a
couple feet of the
canister that the telescoping capture unit is deployed. This can be sensed in
a number of
ways, one way being to know how much of the line has been reeled in. Other
ways
include optical sensors or other physical proximity sensors.
What has therefore been provided is a system for deploying decoys in which the
decoy can be retrieved and deployed multiple times even within one mission,
thereby
eliminating the wastage associated with sacrificial units. The utilization of
a fiber optic
rotary joint and high voltage slip rings eliminates the possibility of
fouling, jamming or
backlash along with the utilization of a co-driven, double helix, traversing
wire guide. The
result is that decoys can be flown with a single tow wire thereby limiting the
complexity of
the towing system. Additionally, fiber optic conimunications can be utilized
without fear
of the destruction of the fiber optic cable during deployment or retrieval.
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Having now described a few embodiments of the invention, and some
modifications and variations thereto, it should be apparent to those skilled
in the art that
the foregoing is merely illustrative and not limiting, having been presented
by the way of
example only. Numerous modifications and other embodiments are within the
scope of
one of ordinary skill in the art and are contemplated as falling within the
scope of the
invention as limited only by the appended claims and equivalents thereto.
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