US3611367A

US3611367A - Airborne station for aerial observation system

Info

Publication number: US3611367A
Application number: US796234A
Authority: US
Inventors: Henri Billottet; Marcel Kretz
Original assignee: HOUSTON HOTCHKISS BRANDT COMP
Current assignee: FRANCAISE HOUSTON-HOTCHKISS BRANDT Cie; HOUSTON HOTCHKISS BRANDT COMP
Priority date: 1968-02-01
Filing date: 1969-02-03
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05
Also published as: SE370680B; DE1904795A1; DE1904795B2; GB1227724A; NL6901615A; DE1904795C3

Abstract

An airborne radar station, hovering at a fixed location above an associated ground station, comprises a supporting section with a gyrostabilized body held aloft by helicopter blades and a supported section suspended from that body for independent rotation about a substantially vertical axis. The coupling between the two sections includes a parallelogrammatic linkage with an upper base secured to (or part of) the body and a lower base rigid with the supported section or secured thereto through an adjustable mounting automatically maintaining the verticality of a suspension shaft for that section. The downdraft generated by the swirling rotor blades acts upon adjustable fins on the supported section to rotate the latter at a rate controlled by a governor and by signals from the ground station which also includes a tracking radar trained upon the airborne station to determine deviations from its assigned position in space, such deviations giving rise to corrective signals transmitted by short waves to the airborne station for altering the attitude of the supporting section and the effectiveness of its blades by changing the direction of thrust of one or more jets of compressed air issuing from the tip of each blade. A radar antenna on the rotating supported section scans the surrounding area, especially in the region close to the ground, and retransmits incoming echo signals to receiving equipment at the ground station.

Description

United States Patent [72] Inventors Henri Billottet Fontenay Aux Roses; 7 Marcel Kretz, Paris, both of France {21] Appl. No. 796,234 22 Filed Feb. 3, 1969 [45] Patented Oct. 5, 1971 [731 Assignees Compagnle Francaise Houston-Hotchkiss Brandt Paris, France; Giravions Durand Suresnes, France, part interest to each [32] Priority Feb. 1, 1968, Dec. 26, 1968 [33] France [31] 138,277 and 180,638

[54] AIRBORNE STATION FOR AERIAL OBSERVATION SYSTEM 17 Claims, 7 Drawing Figs.

[52] US. Cl 343/6 R, 244/17.1 244/17.17, 244/17.25, 343/65 R 51 Int. Cl .1 G01s 9/02, B64 c 25/00 [50] Field of Search 343/6, 6.5; 244/17.15,17.11,17.25,17.17;l70/135.4

[56] References Cited UNITED STATES PATENTS 1,526,657 2/1925 Bea 244/1 7.11 1,652,090 12/1927 Calvert 244/l7.15 2,001,529 5/1935 Dornier 170/135.4 2,569,882 10/1951 Bothezat 244/17;25 2,886,261 5/1959 Robert et al. 244/17.25

Primary ExaminerMalcolm F. Hubler AnomeyKarl F. Ross ABSTRACT: An airborne radar station, hovering at a fixed location above an associated ground station, comprises a supporting section with a gyrostabilized body held aloft by helicopter blades and a supported section suspended from that body for independent rotation about a substantially vertical axis. The coupling between the two sections includes a parallelogrammatic linkage with an upper base secured to (or part of) the body and a lower base rigid with the supported section or secured thereto through an adjustable mounting automatically maintaining the verticality of a suspension shaft for that section. The downdraft generated by the swirling rotor blades acts upon adjustable fins on the supported section to rotate the latter at a rate controlled by a governor and by signals from the ground station which also includes a tracking radar trained upon the airborne station to determine deviations from its assigned position in space, such deviations giving rise to corrective signals transmitted by short waves to the airborne station for altering the attitude of the supporting section and the effectiveness of its blades by changing the direction of thrust of one or more jets of compressed air issuing from the tip of each blade. A radar antenna on the rotating supported section scans the surrounding area. especially in the region close to the ground, and retransmits incoming echo signals to receiving equipment at the ground station.

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Attorney AIRBORNE STATION FOR AERIAL OBSERVATION SYSTEM for exploring, e.g. by radar, the surrounding terrain and the I area immediately above it. Such systems are useful, for example, to guard against sneak attacks by low-flying aircraft or missiles.

The use of lighter-than-air vehicles, such as blimps or barrage balloons, as airborne observation stations has the disadvantages of bulky and costly equipment, vulnerability to hostile attack and lack of stability in the face of atmospheric disturbances. If cables are used to hold an airship in a fixed position above the ground, its maximum altitude is limited to several hundred meters; also, the cables tend to interfere with the radar beam so as to create blind spots in its panoramic sweep. On the other hand, the placement of an airborne station aboard a moving craft creates considerable problems of plotting the location of detected objects and of maintaining contact with an associated ground station, this being true even where the craft follows a predetermined course at relatively low speed and is being continuously tracked by Doppler-type radar equipment.

The general object of our present invention, therefore, is to provide an improved observation system of the character set forth in which the aforestated disadvantages are avoided.

A more particular object is to provide, in such a system, an airborne station adapted to hover in a virtually fixed position, at an altitude on the order of kilometers, above an associated ground station in constant communication therewith.

It is also an object of our invention to provide means for continuously rotating an equipment-bearing section of such an airborne station about a substantially vertical axis and for maintaining the verticality of that axis even under adverse atmospheric conditions, such as gale winds and strong gusts.

These objects are realized, pursuant to our present invention, by the provision of an aerodyne-type craft divided into a supporting section and a supported section, the latter being suspended from the former with freedom of independent rotation about a substantially vertical axis; the supporting section carries orientable propulsion means, such as a rotor having propeller blades with adjustable nozzles for the discharge of jets of a high-pressure fluid (preferably air) from their tips, whereby the attitude of this section can be controlled in response to command signals from the ground station to nullify deviations from its assigned location as detected by tracking equipment on the ground. Such tracking equipment may include an emitter of continuous or pulsed radar signals directed toward a transponder aboard the craft, the latter being advantageously positioned substantially at the center of gravity of the supported section so as to indicate precisely, by Doppler etTect and angle measurements, any displacement of that center (and therefore of the axis of rotation of the equipmentcarrying section) as well as, advantageously, the rate of such displacement. The positional information received by the tracking radar is then evaluated by a computer at the ground station which, via a ratio link of the UHF or VHF type, transmits corrective signals to the airborne station represented by the craft.

According to another important feature of our invention, we provide impeller means for rotating the supported section of the craft about its substantially vertical axis at a rate controlled from the ground station by way of the aforementioned radio link. In order to avoid the need for a separate power source to generate such rotation, the impeller means advantageously may comprise a set of peripheral vanes on the supported section positioned in the downwardly directed slip stream of the propeller blades of the supporting section. By driving these propeller blades through a discharge of highpressure fluid from their tips, as described above, we also avoid the need for a torque compensator designed to counteract the reaction otherwise exerted by the rotor upon its supporting body. The latter, therefore, may be conveniently stabilized against rotation by a conventional gyroscope drawing relatively little energy from the power supply aboard the craft.

A further aspect of our invention relates to the maintenance of the vertical position of the axis of rotation of the supported section or nacelle carrying the observation equipment. Since the supporting section mustbe orientable to compensate for drifts so that its own axis will not invariably be vertical, the two sections should be interconnected by a swing joint permitting relative inclination of their respective axis at least over a limited angular range. In order to permit a relative lateral shifting of the two axes in response to air pressure, a parallelogrammatic linkage with two parallel bases, i.e. an upper base coupled to or forming part of the supporting section and a lower base coupled to or forming part of the supported section, is advantageously inserted in tandem with the swing joint. Under normal atmospheric conditions, gravity alone may be depended upon to maintain the axis of the suspended nacelle practically vertical. In the presence of severe gusts or sustained air currents of extraordinary magnitude, however, means should be provided for automatically reestablishing the desired horizontal plane of rotation. Thus, pursuant to a more specific feature of our invention, we provide an adjustable coupling between the lower base of the parallelogrammatic linkage and a shaft tiltably mounted on that base by the aforementioned swing joint. This adjustable coupling may take the form of at least two extensible connectors, such as solenoids or fluid-actuated jacks, bearing in two substantially conjugate planes upon the lower base and a head or other projection on the shaft'axially spaced from that base. The term "substantially conjugate planes refers to a pair of planes which intersect at the center of the swing joint and lie approximately at right angles to each other as well as to the two bases. The extensible connectors may be selectively adjusted, in response to the direction of tilt, by a plumb detector disposed within the tubular shaft.

The above and other features of our invention will -be described hereinafter in greater detail with reference to the accompanying drawing in which:

FIG. 1 is an isometric view illustrating diagrammatically system according to the invention, comprising a ground station and two associated airborne stations;

FIG. 2 is an elevational view, partly in section, of a craft forming one of the airborne stations of FIG. I together with a mobile landing platform therefor;

FIG. 3 is a block diagram showing the components of the ground station and an associated airborne station in the system of FIG. 1; FIG. 4 schematically shows a parallelogrammatic linkage between a supporting and a supported section of an airborne station according to the invention, this Figure also including a vector diagram illustrating the interplay of forces acting upon that linkage; I

FIG. 5 is a view similar to FIG. 2, showing a modified airborne station according to our invention;

FIG. 6 is an elevational detail view, partly in section,,of a.

rotor blade and associated elements forming part of the craf of FIG. 2 or 5; and j I FIG. 7 is a perspective view, with parts broken away, of an adjustable coupling for keeping the supported section of the vehicle of FIG. 5 centered on a vertical axis.

In FIG. 1 we have shown two airborne vehicles I and l" hovering at substantially fixed locations above an associated ground station II which, as shown, may be a self-propelled vehicle or a trailer mounted on wheels but which for purposes of the following discussion will be considered stationary. The two airborne stations I, l" are assumed to be virtually identi cal, consisting each of a helicopter-type supporting section 101, I01" and a nacelle-type supported section 102', 102".

The centers of gravity G, G" of sections 102', 102" are maintained at substantially fixed locations given by the dimensions x, y, 2', respectively, in a coordinate system x, y, z with a vertical axis z; as illustrated, the elevations z, z" of the two centers G G" above ground may be identical.

By a tracking system, more fully described hereinafter, the ground station II detects any deviation Ax, Ay, Az of the center of gravity of either craft from its assigned position and transmits corrective signals to the craft via a respective radio link 103', 103"; these radio links need not be strongly directive and may operate on different UHF or VHF frequencies for the two stations I and I These radio links may also convey information to the ground station on the condition of the airborne equipment (e.g., on the state of the fuel supply aboard the craft) and, as also more fully described hereinafter, may transmit echo pulses picked up by an airborne radar receiver for indicating the location of reflecting objects on a panoramic screen or other display device viewable by the ground crew.

The use of two separate airborne stations I, I" enables continuous surveillance of the surrounding airspace and terrain by overlapping operations of their respective radars, with alternate servicing of the two crafts to replenish their fuel supply and 21 make necessary adjustments. Such servicing requires the descent of the craft to ground level, again under the control of command signals from station 11, and its subsequent return to its assigned position aloft.

Under ideal conditions, in calm weather, the rotor axes A, A" of the propellers 101', 101" should coincide with the vertical axes Z, Z" passing through the centers of gravity G, G, the propeller blades then generating just enough uplift to balance the weight of the craft whereby the latter is suspended motionless in space (except for a rotation of the

nacelles

102, 102" about axes Z, 2" as described hereinafter). In order to counteract air currents which would cause the craft to drift from its assigned position the rotor axis is headed into the wind by an angle sufficient to create a compensatory velocity component. With a substantially constant rotor speed, the ascent or descent of the craft may be controlled by changing the effective pitch of the blades; by periodically varying this effective pitch in the course of a revolution, we may achieve a desired inclination of the rotor axes with reference to the vertical axes Z, Z". As described in greater detail below, we may realize the effect of such variation in pitch by altering the direction of a high-pressure fluid stream issuing from the trailing edge of each blade.

In FIG. 2 we have shown in greater detail the two

sections

101, 102 of an aerodyne-type craft representing either of the two airborne stations I, I" of FIG. 1. Supporting section 101 comprises a gyrostabilized body 104 rigid with a tubular shaft 105 on which a propeller hub 106 is joumaled for rotation about axis A. Two hollow blades 107 extend radially from hub 106 and are provided at their tips with swivelable extensions 108 having slots 109 along their trailing edges, these slots thus forming orientable nozzles for the discharge of jets of air or other fluid admitted under pressure to the interior of the blades in a manner more fully illustrated in FIG. 6. As shown in that Figure, nozzle 108 has a tubular stem 110 joumaled in a fluidtight bearing 111 and open toward the interior of hub 106 which communicates through ports 112 with the interior of shaft 105. The position of each stem 110, and thus of the corresponding nozzle 108, is adjustable by a mechanism here shown to comprise a lug 113 projecting outwardly from each blade 107 and terminating in a roller riding on an annular swashplate 114 whose position relative to the stabilized body 104 is adjustable by the selective actuation of four peripherally equispaced extendable connectors 115 (only three shown), such as hydraulic or pneumatic jacks, solenoids, or threadedly interengaging and relatively rotatable members. The selective actuation of these connectors 115 enables the swashplate 114 to be bodily raised or lowered along axis A or to be inclined with reference thereto at a desired angle. Lug l 13, when contacting a raised portion of swashplate 114, turns the stem 110 against the force of a torsion spring 117 in a direction lowering the nozzle outlet 109 so as to generate an upward component of thrust. With the swashplate 114 in an inclined position, the orientation of the nozzle outlet will vary from downward to upward and vice versa during a 180 rotation of the corresponding blade 107 with resulting generation of an asymmetrical thrust component to incline the axis Awith reference to the vertical.

In the embodiment of FIG. 2, the shaft terminates in a ball joint 124 linking it with another tubular shaft 118 which rises vertically from a horizontal base 119 forming a parallelogrammatic linkage with a second, lower base 120, the two bases being articulatedly interconnected by three

rigid rods

121, 122, 123; it will be understood that the minimum number of such rods is three but that, if desired, a greater number could be provided. The lower base is rigid with a nacelle 125 which houses the observation and control equipment described hereinafter, this equipment being indicated diagrammatically in FIG. 2 by a block mounted on a platform 126 which is braced against the bottom and the sides of the nacelle housing by shock-absorbing suspension means here shown as a set of springs 127. The nacelle housing is advantageously designed as a radome and should include the necessary electromagnetic shielding between its sensitive equipment and other parts of the craft. An undercarriage 128, here shown as comprising essentially a tripod, is designed to facilitate a soft landing of the craft on the ground. A set of peripheral vanes 129, of adjustable pitch angle, extend peripherally from the nacelle 125 so as to set the latter in rotation about the vertical axis Z passing through the center of gravity of the nacelle, this rotation being caused by the downdraft forming part of the slipstream of the propeller blades 107. With the supporting body 104 held substantially nonrotating by its internal gyroscopic mechanism, the pitch of the vanes 129 is advantageously so chosen that the sense of rotation of nacelle 125 is opposite that of propeller 106-108.

In principle, the powerplant driving the propeller may be located either on the supporting section 101 or on the supported section 102. In the embodiment of FIG. 2 this powerplant is carried on the nacelle 125 and comprises a pair of symmetrically disposed air compressors whose output is delivered through respective pipes 171 to the interior of shaft 118 communicating with the interior of shaft 105. Each compressor 140 is driven by an associated prime mover 141, e. g. a Diesel engine or a turbojet, which also drives a main generator 152 supplying current to all the electric equipment aboard the craft.

If power should fails, e.g. because of exhaustion of the fuel supply for the engines 141 aboard the craft, the drive of the rotor 106-108 will stop and the craft will start descending. This descent will set the blades 107 in reverse rotation which, through a pinion 143 meshing with a set of teeth 144 (FIG. 6) on hub 106, drives an auxiliary generator 145 by way of a unidirectional clutch not shown. This low-power generator, besides exerting a braking effect on the propeller to slow down the descent, also provides an emergency supply of electric current to keep at least some of the equipment (e.g. the gyroscopic stabilizer of body 104) in operation .and to maintain some communication with the ground. In normal use, however, the craft will be brought down by a controlled descent while there is still enough fuel aboard to drive the propeller, e.g. after an operating period of 5 to 10 hours.

The construction of the undercarriage 128 and of the nacelle itself may be simplified by the provision of a mobile platform 146, FIG. 2, which may be rolled under the nacelle as the craft hovers at low altitude above the ground and which is shown to comprise a cradle 147 supporting a spherically convex rocker member 148 whereon a disk 149 is freely rotatable about a shaft 150. Thus, the craft may alight on the platform 146 with the nacelle 125 still rotating and with its undercarriage 128 inclined at a small angle relative to the horizontal.

In FIG. 3 we have used the same reference numerals as before to indicate elements already described (or their equivalent). These elements include the block 130 of FIG. 2, here shown as a rectangle, as well as the main and auxiliary

current generators

142, 145, the powerplant 141, the propeller drive 140 (represented by the compressors of FIG. 2), the gyro stabilizer 104, and the attitude control represented in FIGS. 2 and 6 by the jacks 115. There is also provided a fuel reservoir 151 which may include a conventional floatttype level indicator, not shown, for transmitting information on its contents to the block 130 for transmission to ground station 11.

For the sake of clarity, we have indicated mechanical connections in FIG. 3 by dot-dash lines, power circuits by heavy solid lines and signaling circuits by thin solid lines.

The equipment forming part of block 130 includes a radar transmitter 31 with a directive antenna 30 also connected to an associated radar receiver 32. An omnidirectional antenna 341, associated with a transceiver 34, forms part of the radio link 103 described in connection with FIG. 1. Transceiver 34, coupled with radar transmitter 31 and receiver 32 for exchanging information therewith, also works into a command generator 35 delivering output signals to an automatic pilot 33 and to a governor 17 connected via a mechanical linkage 18 with the vanes 129. Governor 17 may be basically a centrifugal speed regulator adjustable under the control of signals from command generator 35; if desired, however, the centrifugal regulator may be omitted and the governor may respond only to the command signals received via radio link 103 and generator 35.

The autopilot 33, on the basis of the drift information Ax, Ay, Az supplied to it from command generator 35, sets the attitude control 115 to reorient the nozzles of flaps 108 as described above. These drift signals Ax, Ay, Az are derived from a computer 43 on the ground which receives positional information from a tracking radar including a transceiver 45 with directive antenna 44 and a plotter 46 evaluating the output of the transceiver as is well known per se. The radiation pattern of antenna 44 may be a relatively narrow cone trained upon the general location of the center of gravity of nacelle 125 which is assumed to deviate only slightly from its assigned position. This center of gravity substantially coincides with an aerial 371 of a transponder 37 aboard the craft 1, cooperating with the antenna 44 of the tracking radar, so that plotter 46 can determine at any instant the drift, if any, of the nacelle from a fixed reference point having the coordinates x, y, 2. Computer 43 then generates the magnitudes AI, Ay, A2 of the corrective signals which, via a transceiver 40 with antenna 401 forming part of the radio link 103, retransmits them to the craft 1. 7

Radar pulses picked up by antenna 30 in nacelle 125 are transmitted via the same radio link to a video stage 41 whose output appears on a display indicator 42, such as an oscilloscope screen. Indicator 42 is synchronized with the rotation of nacelle 125, and therefore with the sweep of scanning antenna 30, by timing pulses from a clock circuit 152 which also reach a scan-control network 153 connected in the output of a monitoring receiver 154. A sharply directive antenna 155 of receiver 154 detects, once per revolution of nacelle 125, a continuous beam 156 transmitted by an eccentrically positioned antenna 157 aboard the craft, this antenna forming part of a transmitter 158. The control network 153 delivers to computer 43 a signal representative of the speed of rotation of nacelle 125, thereby enabling this computer to transmit to command generator 35 other corrective signals acting upon speed governor 17 to keep the antenna sweep synchronized with the operation of indicator [4.

In FIG. 4 we have diagrammatically illustrated a parallelogrammatic linkage with upper and

lower bases

119 and 120, such as the one illustrated in FIG. 2, suspended from a fixed point 0 (such as the center of the ball joint 1240f FIG. 2) and supporting a load, such as the nacelle 125, having a center of gravity G. in the vertical position of the linkage, points G and 0 lie on a common axis Z representing the axis of rotation of the nacelle. The downwardly directed force p, representing gravity (together with a possible vertical acceleration), is then exactly balanced by an upward force q representing the uplift generated by the swirling propeller.

If, now, a lateral force f (due, for example, to a squall) acts upon the center 0, the linkage is deflected into a position partly illustrated in dotted lines in which, however, the

' resultant r is no longer in line with the point 0. This resultant r has two components r, and r the former being on a line L passing through 0 while the latter is perpendicular to that line and generates a torque (here clockwise) centered on 0. Whereas the force r can be compensated by a corresponding inclination of the vector q through a change of the propeller attitude, the component r, can be balanced only by a reorientation of the parallelogrammatic linkage, i.e. a transition from the unstable dotted line position to a stable position illustrated in dot-dash lines. In the latter position the

bases

119 and 120 are no longer horizontal, yet the resultant r of forces p and f now coincides with line L passing through the suspension point 0, the balancing force q 4 being then exactly equal and opposite to vector r.

With the arrangement heretofore described, in which the nacelle was rigid with lower base 120, the horizontal position of platform 126 (FIG. 2) could therefore not be maintained in the face of squalls or strong winds giving rise to an appreciable deflecting force f. For this reason, in a modified system more fully described hereinafter with reference to FIG. 5, we have shown in FIG. 4 an articulated suspension for the nacelle including a shaft 159 swingable about a ball joint 160 on base 120. Since the swing joint at point 0 now becomes redundant, we may connect the stabilized supporting body 104 rigidly with shaft 1 18 rising from base 119.

Since, under the assumed condition of strong atmospheric disturbances, gravity alone could not be relied upon to keep the nacelle from swaying, we provide an adjustable coupling between the shaft 159 and the base 120 in the form of a projection 161 on the shaft and an extensible connector 162, similar to the elements 115 of FIGS. 2 and 6, anchored to that projection and to the base 120. In the swung-out position illustrated in dot-dash lines, the connector 162 is automatically extended to restore the vertical position of shaft 159. The manner in which this is done will be described in greater detail with reference to FIGS. 5 and 7.

The supporting section 101a of the modified craft la shown in FIG. 5 is generally similar to section 101 of FIG. 2 and need not be described in detail, except for the fact that shaft 118 has been extended upwardly to replace shaft 105 and that the power supply units 140-142 have been relocated on the upper base 119 of the parallelogrammatic linkage, within a protective canopy 163, the gyrostabilized body 104 being now rigid with shaft 118 and with platform 119. On the other hand, nacelle 125 is rotatably suspended from shaft 159 through a bearing 164 also establishing, via one or more sliprings 165 and contact brushes 166, electrical continuity between sections 101a and 102a. It will be understood that these sliprings and brushes are connected to insulated wires extending within the shaft 159 and the suspending framework 167; a cable extending partly within

shafts

118 and 159 encompasses a portion of this circuit.

The aforedescribed swing joint between shaft 159 and base 120 comprises a ball 168 on the shaft held in a spherically curved ring socket 169 which is rigid with base 120. The jack 162 of FIG. 4 is representative of two such jacks 162x, 162y bearing upon a head 161 (FIG. 5) above base 120, or upon a pair of arms 161x, 16ly (FIG. 7) below that base symbolized by the similarly designated projection of FIG. 4; the two jacks thus serve to swing the shaft 159 in two mutually conjugate planes which may be respectively parallel to the x2. plane and the yz plane of the coordinate system of FIG. 1.

As more particularly illustrated in FIG. 7, the interior of shaft 159 contains a plumb detector in the form of a conductive weight 172 suspended from a wire 173, this weight being out of contact with a set of conductive segments 174 on the in.- side of the nonconductive or insulation-lined shaft 159 as long as the latter is substantially vertical. As soon as the shaft tilts in any direction, weight 172 engages one of the segments I74 and closes a circuit to a controller inside the bass 168 which energizes either or both jacks 162x, 162y in an extending and/or contracting sense to restore the shaft to its vertical position.

The nacelle 125 may, of course, be provided with any conventional supplemental equipment needed to ensure satisfactory operation, including protective screening against cosmic radiation. The platform 146 illustrated in FIG. 2 may be used for both landing and takeoff, thus sewing as aconvenient means for initially positioning the craft 1 in line with its desired airborne location. Naturally, compatible features from different embodiments (e.g. the provision of a protective canopy 163, FIG. 5, for the assembly 140-142 of FIG. 2) may be combined or substituted without departing from the spirit and scope of our invention.

We claim:

1. An aerial observation system comprising a ground station; an airborne station hovering above said ground station at a substantially fixed location, said airborne station including a supporting section provided with orientable propulsion means for holding same aloft and further including a supported section suspended from said supporting section with freedom of at least limited relative inclination and independent rotation about a vertical axis; a radio link interconnecting said stations; tracking means at said ground station for detecting deviations of said airborne station from a predetermined position in space; evaluation means at said ground station coupled to said tracking means for translating such deviations into corrective signals and for transmitting same to said airborne station via said radio link; control means at said airborne station coupled to said radio link for reorienting said propulsion means in response to said corrective signals to nullify said deviations; impeller means for rotating said supported section about said axis; observation equipment aboard said supported section for exploring the space around said airborne station and transmitting resulting information signals to said ground station by way of said radio link; receiving means at said ground station coupled to said radio link for directing said information signals to a load; sensing means aboard said airborne station responsive to tilting of said supported section with reference to said axis; and control means coupled to said sensing means for angularly adjusting said supported section to restore the verticality thereof.

2. A system as defined in claim 1 wherein said propulsion means comprises a rotor with a generally vertical axis having a set of blades and drive means for rotating said blades about the rotor axis.

3. A system as defined in claim 2 wherein said blades have tips provided with adjustable nozzle means, said drive means including a source of high-pressure fluid led to said nozzle means for discharge into the atmosphere, said control means comprising a mechanism for adjusting said nozzle means.

4. A system as defined in claim 2 wherein said impeller means comprises a set of peripheral vanes on said supported section adjustable disposed in the slipstream of said blades for rotation thereby.

5. A system as defined in claim 4, further comprising governor means controllable from said ground station via said radio link for varying the speed of rotation of said supported section by adjusting said vanes.

6. A system as defined in claim 2, further comprising generator means coupled with said rotor for entrainment thereby upon reverse rotation of said blades to supply emergency power to said airborne station upon an uncontrolled descent of the latter.

7. A system as defined in claim 2 wherein said sections are provided with a swing joint interconnecting same with freedom of relative inclination in different vertical planes.

8. A system as defined in claim 7, further comprising a parallelogrammatic linkage interconnecting said sections in tandem with said swing joint for permitting limited relative lateral shifting of said axes.

9. A system as defined in claim 8 wherein said supporting section comprises a rotor-carrying body and said linkage includes an upper base rigid with said body and a lower base parallel to said upper base, said supported section comprising a nacelle rotatable with reference to said body.

10. A system as defined in claim 9 wherein said nacelle has a shaft tiltably mounted on said lower base by said swing joint, further comprising an adjustable coupling between said lower base and said shaft, said sensing means including a detector on said shaft for ascertaining departures thereof from a vertical position, said control means including automatic means for adjusting said coupling under the control of said detector means to restore said vertical position.

1 1. A system as defined in claim 10 wherein said adjustable coupling comprises a projection on said shaft axially spaced from said lower base and a pair of extensible connectors eccentrically linking said projection with said lower base in two substantially conjugate planes.

12. A system as defined in claim 9 wherein said supported section further includes an instrument-carrying platform and cushioning means yieldably supporting said platform in said nacelle.

13. A system as defined in claim 9 wherein said nacelle is provided with an undercarriage for landing on the ground, further comprising a mobile cradle on the ground and a rotatable rocker on said cradle forming an alighting surface for said undercarriage.

14. A system as defined in claim 1 wherein said observation equipment comprises a radar antenna positioned to explore the area surrounding said airborne station.

15. A system as defined in claim 1 wherein said tracking means comprises radar equipment at said ground station and a transponder aboard said airborne station located substantially at the center of gravity of said supported section.

16. A system as defined in claim 1, further comprising a second airborne station hovering above said ground station at another substantially fixed location, said airborne stations being substantially identical for overlapping utilization under the control of said ground station whereby observation can be carried out continuously during alternate servicing of said airborne stations.

17. An aerial observation system comprising a ground station; an airborne station hovering above said ground station at a substantially fixed location, said airborne station including a supporting section provided with orientable propulsion means for holding same aloft and further including a supported section suspended from said supporting section with freedom of at least limited relative inclination, said supported section comprising a rotatable nacelle provided with an undercarriage; a radio link interconnecting said stations; tracking means at said ground station for detecting deviations of said airborne station from a predetermined position in space; evaluation means at said ground station coupled to said tracking means for translating such deviations into corrective signals and for transmitting same to said airborne station via said radio link; control means at said airborne station coupled to said radio link for reorienting said propulsion means in response to said corrective signals to nullify said deviations; impeller means for rotating said nacelle about a substantially vertical axis; observation equipment on said nacelle for exploring the space around said airborne station and transmitting resulting information signals to said ground station by way of said radio link; receiving means at said ground station coupled to said radio link for directing said information signals to a load; a mobile cradle on the ground; and a rotatable rocker on said cradle forming an aligning surface for said undercarriage.

Claims

11. A system as defined in claim 10 wherein said adjustable coupling comprises a projection on said shaft axially spaced from said lower base and a pair of extensible connectors eccentrically linking said projection with said lower base in two substantially conjugate planes.