CA1050150A - Self propelled array system - Google Patents

Abstract

HYDROPHONE ARRAY SYSTEM
Abstract of the Disclosure A hydrophone array system comprising a plurality of hydrophones fastened to a cable is deployed beneath the sea in a substantially horizontal straight line. A small powered thruster fastened to one end of the cable urges it in a first direction and this urging is resisted by a member, such as a drogue or an anchored subsurface float, fastened to the other end of the cable. Individual signals from each of the hydrophones are conducted to the surface where they are processed and transmitted by a radio link to a nearby aircraft or surface vessel. Beam forming and analysis is performed aboard the aircraft or surface vessel.

Description

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~OS0150 Cross Reference to Related Application This application is a continuation in part of our copen-ding application Serial No. 494,154 filed August 2, 1974.
Field of the Invention This invention::relates generally to underwater listening devices and particularly to an array of such devices deployed in a substantiaIly horizontal straight line beneath the surface of the sea.
Background of the'Invention As the art:of underwater listening progresses, the equip-ment is required to detect fainter,and ainter sounds at greater and greater distances with more and more directional precision.
The art has advanced so that the designer now ha~ available,-very sensitive hydrophones and sophistioated beam ~orming tech-niques. One way to take advantage of these advances is to de-ploy the hydrophones in a substantially horizontal straight Iine beneath the surface as far removed as possible~from sources of unwanted sounds, or noise.
In the past, an array of hydrophones has been deployed in a straight line beneath the surace by stringing the hydrophones along a cable towed by a surface ship or low flying helicopter with or without an intermediate buoyant "ish" such as a long cylindrical body. Depth has been controlled by adjusting the buoyancy of the array~and/or by the use of weights on the cable itself, the whole being supported by surface floats.. Such an arrangement, although suitable for many purposes, has the dis-advantage of requiring the presence of the ship during operation which is not only expensive and.highly visible but which is a source of noise.
It has been proposed to dispen~e with the ship by suspend~

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~ 10501S0 one end of the array from a surface float. It has been found, by suitably adjusting the buoyancy of the.array and its hydro-dynamic characteristics and by termina:ting the other end of the array with a sea anchor, that such an array can be str~hed out into a substantially horizontal straight.line provided there is sufficient current at the required depth. However, when the current drops below a.critical value, the array will not hold its straightness.
It is a general ob~ect of the present invention to provide an improved system for deploying an array of hydrophones.
A more specific object~of the invent1on is.to provide an impr0ved system for deploying a series of hydrophones in a quiet environment beneath the surface of the sea in a substan-tially straight horizontal line.
Summary:of the Invention , Briefly stated, the lnvention is based in par~ on .the dis-covery~that very little~tension is required to maintain a neu~
trally buoyant line of hydrophones extended in a straight line -beneath the surface of the:sea. The invention is also based in part on the further discovery that such tension may be ob-tained by a small powered thruster on one end of the line, for urging the line forward, along with something.on the other end of the line for resisting such.urging. This provides the ten- ;
sion necessary to achieve array straightness while..maintaining a very low velocity of the array through the water to minimize flow induced noise. Vibration isolation, such as resilient motor mounts and a bungee in the line, improves performance.
Brief Description of~the Drawin~
For a:clearer understanding of the invention reference may be made to the following detailed description and the D-32~A
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1050~0 accompanying drawing, in which:
Figure 1 is a schematic elevation view showing how the components of the apparatus can be arranged within a sonobuoy;
Figure 2 is a schematic cross section view taken on the line 2-2 of Figure l;
Figures 3, 4, 5, 6 and 7 are schematic views showing successive stages in the deployment of the array system of the invention, with Figure 7 showing the apparatus fully de-ployed in operative position;
Figure 8 is a schematic cross section view taken on the line 8-8 of Figure:7;
Figure 8a is a schematic cross section view, with parts in elevation, of the thruster;
Figure 8b is a cross section view taken on the line 8b-8b of Figure 8a;
Figure 8c is a schematic diagram of a portion of the system;
~Figures 9, 10, 11 and 12 are schematic views of modified forms of the invention;
zo Figure 13 is a schematic cross seation view of another em-bodiment of the invention before deployment;
Figures 14, 15, 16, 17, 18 and 19 are schematic elevation views showing successive stages in the deployment of the embodi-ment of Figure 13;
Figure 20 is a schematic plan view of the embodiment of Figure 13 after deployment;
Figure 21 is a schematic diagram of the control e~uipment of the embodiment of Figure 13; and Figures 22, 23, 24 and 25 are schematic elevation views showing various stages during the recovery of the embodiment lOS~
of Figure 13.
Description of Preferred Embodiment The array system of the invention may be placed in the sea in various ways, for example, by lowering it over the side of a surface vessel, but it is believed that it will have its widest application when packaged in a sonobuoy casing and deployed by an aircraft. Accordingly, a preferred embodiment will first be described as so packaged and deployed.
Referring first to Figure 1 there is shown the casing 21 of a sonobuoy which is assumed to have been cut away so as to show how the various components may be arranged therein prior to deployment. At the top of the casing 21 there is shown a transmitter float 22 in its deflated condition with a trans-mitter 23 within. Beneath the float 22 is stored the signal and suspension cable 24 and beneath that an electronics package 25 which may contain various electronic components such as a ~ompass, a multiplexer, modulators, amplifiers and the like.
A sea anchor, or drogue, 26 is stored just below'the electronics package. Below the drogue 26, on the axis of the casing 21, is stored a powered thrus,ter, indicated generally by the reference character 27, and including a housing 28. Any of various kinds of internal or external power~sources, such as electric,ity or compressed gas, may be used with any of various propulsion arrangements, such as gas or water jets. The thruster should, of course, be constructed to generate as little noisé as pos-sible. Not only should the internal mechaaism operate guietly but the propulsion system should cause as little flow induced noise as possible. It is at present preferred that the thrus-ter 27 include a battery 29 and an electric motor 31 within the housing 28 and a propeller 32 mounted exteriorly at one D--3 2 ,?~ ~S
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~OS0150 end of the housing 28 and operatively connected to the motor 31.
As best shown in Figure 2, a plurality of hydrophone assemblies 34 are positioned beneath the drogue 26 and sur-rounding the housing 28 of the thruster 27. As indicated schematically in Figure 1, each of the aasemblies 34 comprises a preamplifier 35 ~onnected to and packaged with one electro-acoustic transducer such as a hydrophone 36 to form one hydrophone assembly 34. Immediately beneath the assemblies 34 and also surroundin~ the thruster 27~is a series of pack-ages containing a cable 37 which, as will be more fully dis-cussed, is connected to each of the hydrophone assemblies 34.
Referring now to Figure 3, there is shown a sonobuoy indicated generally by the reference character 41 and includ-ing an outer skin 42 and a rotochute 43. The sonobuoy 41, containing the components as explained in connection with Figures 1 and 2, is shown after its release by an aircxaft as it is about to enter the water 44. The rotochute 43, as is well known, is provided to slow the descent of the buoy so `that it does not strike the water too hard.
Figure 4 shows the buoy just after striking the water.
rrhe ~in 42 and the rotochute 43 are jettisoned and the remain-der of the sonobuoy starts its descent. At about the same time the transmitter float 22 is inflated and, as shown in Figure 5, rises to the surface with the transmitter 23 inside.
A previously retracted antenna ~5 is extended. The previously mentioned cable 24 inc1uded both load bearing and signal carrying elements. One end of the cable is mechanically con-nected to the float 22 and is electrically connected to the transmitter 23. As the buoy aescends, the cable 24 is payed RKr ~~

out until a predetermined depth is reached.
When the predetermined depth is reachedl the drogue 26, the electronics package 25 and the thruster 27 are released from the housing 21. As shown in Figure 6, the surface cur-rent drag on the transmitter float 22 acts, through the cable 24 and the electronics package 25, to pull the thruster 27 and the cable 37 away from the housing 21 and drogue 26.
This establishes a preferred direction for the subsequent extension of the array~, that is, downstream.
Next, as best shown in Figure 7, the thru~ter 27 is activated and further pulls on the cable 37 to whi~h each of the hydrophone assemblies 34 is attached until the array is fully extended and completely out of the housing 21. As shown, the housing 21 and the drogue 26 are fastened to the end of the cable which is remote from the thruster 27 and this at present is the preferred arrangement although it would be possible to have the casing 21 joined to the thruster 27.
The cable 37, like the cable 24, includes a plurality of elements sn~e of which are mechaaical load bearing elements and others of which are signal conducting elements. The entire array, including the cable 37, the hydrophone assem-blies 34, the housing 21 and the drogue 26 are constructed to be of substantially neutral buoyancy. The housing 28 of the thruster 27 is generally right cylindrical in shape and the entire thruster is negatively buoyantj that is, it tends to sink in sea water.
As best shown in Figure 8, the thruster 27 preferab~y`,i~s constructed so that its center of gravity 46 and its center of buoyancy 47 when submerged lie in the same txansverse plane but are displaced from each other as shown. With this construction, a force couple is generated, when the thruster D-~3,0-A
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27 is deployed in the water, which urges it to assume a pre-ferred attitude, as shown in the drawing, with its longitu-dinal axis horizontal and with its center of gravity 46 directly below its center of buoyancy 47. The thruster 27, is supported by the cable 24 preferably by means o~ a connec-tion including a rigid bracket 48 ,formed with two arms 49 and 50 which embrace and pivotally engage the housing 28 on opposite sides thereof in the aforesaid transverse plane.
The two pivots prefera~ly have a common axis which passes through the center of buoyancy 47. The electronics package 25 is electrically and mechanically connected to t~e cable 24 and is fastened to the bracket 48 which is preferably hol-low so as to accommodate conductors interconnecting the elec-tronics package 25 with the interior of the thruster housing 28. As shown in Figure 7, the cable 37 is mechanically con-nected to the end of the thruster 27 remote from the propeller 32 and its conductors pass through the~housing 28 to the in-terior thereof so that suitable electronic connections can be made.
It has been found that with the apparatus deployed as explained,above, the,thrust~ri~27 may e~pend very little power yet be capable of exerking enough tension on the cable 37 and the hydrophone assemblies 34, as restrained by the drogue 26, to hold the array stretahed out in a substantially hori-zontal straight line with little or no forward motio~. The pivotal connection of the bracket 48 allows the thruster to assume its preferred horizontal attitude, as previously ex-plained. The thruster 27 cannot rise, eveniif momentarily displaced from its preferred attitude, because it has insuffi-cient thrust to overcome its negative buoyan~y and that of D-~ ~-A
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cable 24. It cannot sink because it is supported by cable 24. The rigid arm 48 and the positively buoyant electronics package 25 serve as a stabilizing fin and prevent the thrus-ter 27 from rotating about its axis and winding up the cables.
By way of example, the array may comprise th~rteen hydrophone assemblies 34 logarithmically spaced about its center and covering a distance of approximately 300 feet.
The signal from each hydrophon~, as amplified by its preampli-fier, is passed to the electronics package 25 where the sig-nals are processed further and conducted up the oable 24 to the transmitter 23 in the 10at 22. In most cases it is pre-ferred that the signals be transmitted to a nearby aircraft or surface vessel where all beam forming and analysis takes-plaae although in some instances it may be desirable to in-clude beam forming equipment in the electronics package 25 and/or the float 22. AnalysiS and beam forming in the air or surface craft is usually preferred because by this arrangem~, the complexity of the equipment in the sonobuoy is~greatly reduced and at the same time full advantage can be taken of modern beam forming techniques.
It is to be noted that the various means and methods for deploying the apparatus such as the ejection of the skin 42 and rotochute 43, the paying out of the cable 24, the sensing of the proper depth, and the techniques for separating the various portions and for activating the thruster 27 all com-prise techniques well known in the sonobuoy art. Such tech-niques, in and of themselves, do not form a part o the present invention and accordingly have not been described in detail.
A hydrophone array system as so far described operates satisfactorily but is subject to certain limitations caused ~g_ RKT~
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by noise generated by the thruster. It has been found that such noise is transmitted both directly through the water and over the cable 37. I most of the noise is at frequen-cies outside the frequency band of interest, the noise may be unobjectionable. In any case, by making the cable 37 between the thruster and the first hydrophone very long, the noise reaching the hydrophones can be reduced substantially.
However, it is preferred at present to provi~de for isolation of the source of the noise within the thruster and to mini--10~ mize its transmission through the cable 37.
R~ferring now to Figures 8a and 8b, a pair of brackets 131 and 122 are mounted on opposite ends of the motor 31.
Each bracket i~ formed with two tabs such as the tabs 123 and 124 extending parallel to the motor axis on opposite sides thereof and with one above and the other below the axis as viewed in Figures 8a and 8b. A pair of similar but comple-mentary brackets 125 and 126 are fastened to the~housing 28 as shown. The motor 31~is~mounted by means of four vibration isolators 127, two:of whic~ interconnect the brackets 121 and 12~5 while the other two interconnect the brackets 122 and 126. Each isolator 127 is preferably a commercially available unite comprising a resilient material such as rub-ber into each end of which a stud 128 is molded. The studs extend through holes in the tabs and are fastened with nuts 129. The isolators 127 operate in the usual way to reduce the transmission of vibration form the motor 31 to the housing 28.
Power from the motor 31 is transmitted to its output shaft 131 and then through a flexible coupling 132 in the form of a sleeve of resilient material such as rubber to a RKT:EO' 1~50~50 shaft 133 to which the propellor 32 is fastQned. The coupling 132 serves to prevent the transmission of unwanted vibrations from the motor ~1 to the propellor 32.
Referring now to Figure 8c, there is shown an arrange-ment for minimizing the transmission of noise through the cable 37. Adjacent to the thruster 27, a section of the cable 37,is, in effect, composed of two portions. The first portion is a resilient porti.on of bungee 141 while the second portion is the signal carryiny portion 142. The resilient portion 141 may comprise a length o resilient.ma,terial such as a latex rubber cord capable of being stretched to three or more times its unstretched length without breaking. The portion 142 is wrapped loosely around the portion 141 and is fastened thereto a,t both its forward and aft ends~ The portion 142 is suffioient1y long between its points of attachment to the bungee.141 so that it remains slack at all ' times. From the aft:point of attachment,,the cable 37 ex-tends on to the array of'hydrophone assembLies 34.
The bungee 141 carries the complete mechanical load be-: 20 tween the two points at ~hich the portion 14~ is fastened to it. One satisfactory example is a bungee made of one quarter inch diameter latex rubber cord, twelve feet long in ltS unstretched condition and capable of extending to forty feet or so. The portion 142 is preferably.about sixty feet long between its points of attachment to the bungee. Prefer-ably there is about one hundred feet.of the.cable 37 between the bungee 141 and the first hydrophone assembly 34 of the array.
It has been found that the use of the vibration isolà-tors 127, the flexible coupling 132 and the bungee 141 as D-32~ -A ~ 5 O

above described, substantially eliminates the problem of noise transmission to the hydrophones.
Referring now to Figure 9, there is shown a modified form of the invention. This form includes a-subsurface, buoyant body 51 which is held at a predetermined seleated depth beneath the surface by a cable 52 which extends down-ward to an anchor 53 at the bottom of the sea. ~he body 51 contains an electronics package having components like those in the package 25. A thruster 54, which is made to be of substantially neutral buoyancy, is, as before, connected to one end of the cable 37. ~owever, the other end o~ the cable 37 is connected to the body 51 which, aided by the anchor 53, serves as the member which resists the urging of the thruster 54 in much the same way as the drogue 26 of the previous figures resists the urging of the thruster 27. In either case, the result is that the array of hydrophone assemblies 34 on the cable 37 is held in a substantially hori~ontal straight line. In the embodiment of Figure 9, the signals from the hydrophone assemblies 34 are conducted in a direction away from the thruster 54 and into the eleatronics package contained within the body 51 where they are processed further and then conducted up the cable 24, the lower end of which is attached to the body 51, up to the transmitter 23 within the float 22. The beam orming and analysæ~ is performed in the aircrat or surface vessel to which the signals are trans-mitted, just as it was in the case of the previously described embodiment.
Figure 10 illustrates an embodiment of the invention similar to that of Figure 7 but in which a negatively buoyant drogue 60 replaces the drogue 26 and in which there has been RKT:EO
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added an auxiliary buoyant body or surface float 61 and a cable 62 of substantially the same length as the cable 24 extending from the float to the drogue to insure that the latter stays at the proper depth.
Figure 11 illustrates an embodiment similar to that of Figure 9 except that the subsurface body 51, cable 52 and anchor 53 have been replaced b~ a weight 65 which also contains an electronics package similar to the package 25.
Figure 12 illustrates an embodiment similar to that of Figure 11 except that it employs the negatively buoyant thruster 27 and an auxiliary float 67 and cable 68 to hold the thruster 27 at the proper depth. -~
The embodiments of the invention so far described aresystems in which the array is aligned in a single direction, namely, the direction of the current and in which a very low power thruster is used which exerts only enough tension on the cable to hoId the array stretched out, with little or no motion relative to the water mass. Such systems are very valuable for many purposes and, beaause of the low flow noise, permit the use of extremely sensitive directional hydrophones. However, the principles of the invention are also applicable to controlled systems which are capable of aligning the array in a particular direction relative to geo-graphic coordinates and/or changing the alignment from time to time or continuously in response to a predetermined pro-gram or in response to commands. Such systems need not be deployed by a sonobuoy dropped from an aircraft but may be simply put over the side of a ship or set in the water from a helicopter. A preferred embodiment of a controlled system will now be described.

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RKTiEo Referring now to Figure 13 there is shown schematically a controlled array system as it may be packaged before de-ployment. The system includes a ~enerally cylindrical housing 71 the front p~rtion of which includes a re~ovable--drogue cover 72. Within the housing, immediately behind the cover 72, is the drogue shute 73. An array winch 74 has-wound around it the entire arrayiincluding the sensitive elements and is connected by means of the array cable 75 to the drogue shute 73. Adjacent to the winch ~4 is a guidance -and control package 76 which includes the neaessary control equipment such as relays, valves, solenoids, servo amplifiers, comparator circuits etc. necessary to control the operation of the system. Adjacent to the control pac~age 76 are stora~
batterles 77 which supply the energy for operation of the system. To the right of the batteries, as shown in Figure 13, is a motor and pump assembly 78 which maintains fluid under pressure in a tank 79 which serves as an accumulator and reservoir. T the right of the assembly 78 is à propul-sion motor 81 which is operatively connected to a propeller 82. The housing 71 is formed with openings 83 which allow water to be expelled from the rear of the propeller 82. A
rudder is positioned adjacent to the propeller 82 and is controlled by an actuator 85. An auxiliary housing 86 sep-arates the propeller 82 and the rudder 84 from the remainder of the apparatus, all~wing the propeller and rudder to engage the water while keeping the other components dry. ~he hous~
86 carries an electrical test plug 87 which facilitates elec-trical connections between the various components and external test apparatus. An elastic suspension link 88 is fastened to the housing 71 at the longitudinal center of ~ravity of the D--32 `fA
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entire system and normally is positioned flush against the exterior surface. The purpose of this link will be described subsequently. Immediately behind the propeller 82 is a sus-pension winch 89 around which is wound the suspension cable 91 and a signal cable 92 ~not shown se~arately in Figure 13) both of which are connected to a seperable float package 93.
The package 93 is buoyant and includes a radio ~ransmitter, a receiver, and an antenna and a re~overy mast.
Figures 14-18 illustrate the deploymant of the system. -~~
It may be dropped from a high flying aircraft in which case its descent should be slowed by means of a rotochute such as illustrated in Figures 3 and 4 or it may be simply deposited in the water by a surface ship or a low flying helicopter.
In any event, shortly after reaching the water, it will re-turn to the surface, as illustrated in Flgure 14, by virtue of the buoyancy of the package 93. ~hen, by mechanisms well-known in the sonobuoy art, the deployment se~uence is initi-ated. More particularly, the package 93 is separated from the housing 71 allowing the latter to sink with or without the aid of the propulsion motor 81 and propeller 82~ The suspension winch 89 is released allowing the suspension cable 91, with the signal cable 92 coiled in a series of concentric loops around it, to be unreeled. As the suspen-sion cable 91 pays out, the concentric coils of the signal cable 92 are extended to form a long loose heli~ along the length of the suspension ca~e 91 as shown for example in Figure 15.
As the suspension cable 91 nears the end of its pay out, a small stop 94 fastened to the cable 91 engages a ball 95 that up to this time had been resting on the mouth of the RKT:F~
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cable guide. The ball 95 is attached to the previously mentioned elastic suspension link 88, the other end of which, as previously mentioned, is fastened to the housing at its longitudinal center of gravity in the water. Thus as the last of the suspension cable is payed out, the weight of the system is gradually transferred to this compliant link 88, resulting in the gradual deceleration of the housing and causing it to swing 90 to a horizontal attitude, as shown in Figures 16 and 17. The compliance of the link 88 subsequen,tly serves to help isolate the housing 77 from wave induced motion of the sur~ace float 93. Concurrently with the descent of the system, the antenna 96 is raised up above the float 93.
When the housing 71 has reached its predetermined depth, the drogue cover 72 and the drogue 73 are released and the array winch 74 is unlocked permitting the array~to pay out from the tug as shown,in Figure 18. If the propulsion motor 81 has not already been,energized, lt may be energized now so as to hasten the extension of the array to a substantially straight horizontal position as show~ in Figure 19.
The cable 75 includes a plur~lity of elements some of which are mechanical load bearing elements a~d others o which are signal conducting elements. Like the cable 37, the cable 75 carries a plurality of hydrophone assemblies 97 spaced along its length appropriately to form an array and preferably includes a bu~gee as illustrated in Figure 8c. The cable 75 also carries a small compass 98, electrically connected to the guidance control package 76 within ~he casing 71.
If the array is to be oriented in other tha~ a downstream direction, the thruster must develop a force transverse to D-3230=A
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:~350~50 the array axis to counteract the force produced by the wind and current drag on the surface float, the suspension cable, and the array itself. For example, if, as shown in the plan view of Figure 20, the current and wind were running north to south as shown by the arrow 99 and it were desired to orient the array west to east, then the thruster must pro-duce a north directed force to balance the south directed drag force generated by the surfaae 10at and suspension cable and, in addition, of course~ must provide an east oriented thrust to tension the array. Figure 20 show~ the array in the process of being swung around from a north south direction to an east west direction.
The circuits by which the various controi operations are carried out are shown in block schematic form in Figure 21. In the simplest case, the compass 98 may be one which generates a voltage indicative of actual heading of the array and the programmer~ lOl,:which~may be.contained within the guidance and control package 76, could,:in the simplest case, simply be an adjustable voltage which is preset to the desired heading. In that case, the signal indicative of desired heading is compared, in the comparator ~02, with the actual heading so as to develop an error signal whiah in turn, through the rudder~motor control equipment 103,.contro~
the motor 104 which actuates the rudder 84 until the error signal vanishes. However, the invention contemplates a more flexible arrangement in which the programmer 101. is capable of changing the signal from time to time or continuously and also in which an external command may be received via the radio receiver 105 so as to override the previously estab-lished program and select any desired heading..

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As previously mentioned, the present emboaiment con-templates recovery, refurbishment, and redeployment of the system. Recovery of the system is essentially the reverse of deployment. Upon command received via the receiver 105, or alternatively at the end of a preset period~ of time as determined ~y the programmer 101, a signal is transmitted ; to the propulsion motor control e~uipment 106 which in turn de-energizes the propulsion motor 81. At the same time, another signal is sent to the array winch motor control equipment 107 which energizes the motor 108 ~o as to actuate the winch 74 and start reeling in the array. At the same time the drogue is released by actuating a.mechanism such as a cable cutter adjacent to the point at which the drogue is - fastened to the cable 75. The drogue 73 is jettisoned and the array is reeled in as shown in Figure 22.
When the array is fully retrieved, a signal is sent to the suspension winch motor control eguipmant 109 which in turn energizes the motor 110 so as to acti~vate the suspension winch , 89 which begins to reel in the suspension cable 91. This causes the compliant link 88 to relax and return to its storage position as the housing 71 rotates into a vertical attitude and proceeds to winch its way up.to the surface as shown in Figures 23 and 24.
When the housing 71 reaches the surface 10at 93, the two parts fit back together again and a recovery mast 112 is extended upward into a position where it can be engaged by a suitable hook depending from a.surace ship or a heli-copter.
Refurbishment of the buoy normally involves simply re-placing the drogue and drogue cover, recharging the battery, RKT:E' ~
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and checking the components with the aid of the test plug 87. The buoy is then ready for redeployment.
It is to be noted that each embodiment includes a cable supporting the array of hydrophones and having a thruster at one end of the cable urging the cable in one directinn and something at the other end of the cable to resist the urging, thereby creating tension in the cable and causing it to ex-tend in a substantially straight line.
Although several specific embodiments of the invention have been described in considerable detail for illustrative purposes, many modifications will occur to those skilled in the art. It is therefore desired that the protection afforded by Letters Patent be limited only by the true scope of the appended claims.

Claims (28)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A hydrophone array system comprising a first cable, a plurality of hydrophones connected to said first cable and spaced apart by predetermined distances thereby forming an array, a buoyant body, a transmitter within said body, a second cable extending from said body, and means including said cables for conducting signals from said hydrophones to said transmitter characterized in that said system includes a thruster connected to one end of said first cable for urg-ing it in a preferred direction and a member connected to the other end of said first cable for resisting the urging of said thruster and in that said first cable includes a section adjacent to said thruster which section comprises a first resilient portion and a second, signal carrying portion, said second portion being longer than said first portion, said portions being fastened to each other at each of their ends so that said second portion remains in a slack condition.

2. A hydrophone array system in accordance with Claim 1 in which said array is constructed to be substantially neu-trally buoyant and in which said thruster includes a housing of generally cylindrical shape and is constructed with a weight distribution such that when submerged said thruster is urged to a predetermined preferred attitude with its longitu-dinal axis horizontal so as to stretch out said array in a substantially horizontal straight line.

3. A hydrophone array system in accordance with Claim 2 in which said thruster is constructed to make its center of gravity and its center of buoyancy lie in the same transverse plane but displaced from each other so that a force couple is generated which urges said thruster toward an attitude with its center of gravity below its center of buoyancy.

4. A hydrophone array system in accordance with Claim 1 which includes a plurality of preamplifiers each connected to and packaged with one of said hydrophones thereby consti-tuting a hydrophone assembly.

5. A hydrophone array system in accordance with Claim 4 in which said first cable and said hydrophone assemblies are constructed so as to form an array having substantially neutral buoyancy.

6. A hydrophone array system in accordance with Claim 1 in which said thruster is constructed to have negative buoyancy.

7. A hydrophone array system in accordance with Claim 1 which includes an electronics package connected to said second cable adjacent to that end which is remote from said buoyant body.

8. A hydrophone array system in accordance with Claim 1 in-which each of said first and second cables includes both load bearing and signal carrying elements.

9. A hydrophone array system in accordance with Claim 6 in which said thruster includes a housing of generally cylindrical form.

10. A hydrophone array system in accordance with Claim 9 in which said thruster includes a motor within said housing and a propeller mounted exteriorly at one end thereof and operatively connected to said motor and in which said one end of said first cable is connected to the other end of said housing.

11. A hydrophone array system in accordance with Claim 10 including a connection between said thruster and that end of said second cable which is remote from said buoyant body.

12. A hydrophone array system in accordance With Claim 11 in which said connection includes a rigid bracket having two arms which embrace said housing and are pivotally con-nected thereto.

13. A hydrophone array system in accordance with Claim 12 including an electronics package connected to said bracket and to said second cable.

14. A hydrophone array system in accordance with Claim 13 in which said thruster is constructed to make its center of gravity and its center of buoyancy when submerged lie in the same transverse plane but displaced from each other.

15. A hydrophone array system in accordance with Claim 1 in which said member is a drogue.

16. A hydrophone array system in accordance with Claim 15 in which the end of said second cable remote from said buoyant body is connected to said thruster.

17. A hydrophone array system in accordance with Claim 16 in which said drogue is constructed to be negatively buoyant and which includes a surface float and a third cable of the same length as said second cable extending from said float to said drogue to support said drogue.

18. A hydrophone array system in accordance with Claim 1 in which said member is an auxiliary buoyant body and which includes an anchor, a third cable interconnecting said mem-ber and said anchor, and in which said first and second cables are also connected to said member.

19. A hydrophone array system in accordance with Claim 1 which includes a weight and in which the end of said second cable remote from said buoyant body is connected to said other end of said first cable and to said weight.

20. A hydrophone array system in accordance with Claim 19 including a second buoyant body and a third cable extend-ing from said second buoyant body to said thruster.

21. A hydrophone array system in accordance with Claim 1 which includes means for controlling the direction in which said thruster exerts said urging.

22. A hydrophone array system in accordance with Claim 1 including means on said first cable for generating a first signal indicative of the orientation of said array with res-pect to geographic coordinates.

23. A hydrophone array system in accordance with Claim 22 which includes means including a programmer for generating a second signal indicative of the desired orientation of said array and means jointly responsive to said first and second signals for controlling the direction in which said thruster exerts said urging.

24. A hydrophone array system in accordance with Claim 1 including a receiver within said buoyant body for receiving command signals and means responsive to said command signals for controlling the direction in which said thruster exerts said urging.

25. A hydrophone array system in accordance with Claim 1 including a housing containing said thruster and means within said housing for selectively either paying out said first cable and said array so as to extend exteriorly of said hous-ing or retrieving said array to lie within said housing.

26. A hydrophone array assembly in accordance with Claim 1 including a housing containing said thruster and in which said second cable includes a first end fastened to said buoyant body and a second end fastened to said housing and which includes means within said housing for selectively either paying out said second cable so as to extend between said buoyant body and said housing or reeling in said second cable so as to lie substantially entirely within said hous-ing with said housing in engagement with said buoyant body.

27. A hydrophone array system in accordance with Claim 1 which includes an extensible mast mounted on said buoyant body to facilitate recovery of said system.

28. A hydrophone array system in accordance with Claim 1 in which said thruster includes a motor, a housing, a plurality of vibration isolators mounting said motor to said housing, a propellor mounted for rotation exteriorly of said housing, and a flexible coupling operatively connecting said motor to said housing.