A CORNER REFLECTOR FOR USE IN A RADAR BALLOON

Abstract: A balloon with an internal corner reflector for radio waves is built with the reflecting plane of the reflector freely suspended from a cord frame system which is only secured in the points of suspension. The reflector is suspended inside a balloon which is composed of single flat pieces of a resilient material. Manufacture of the reflector balloon may substantially be done in one plane and the balloon primarily envelopes the reflector very tightly. The suspension utilizes the resiliency of the balloon corners. Balloons which are observed from below may have four internal corners with downwards facing openings and may also be designed to provide rotation.

Description: A CORNER REFLECTOR FOR USE IN A RADAR BALLOON. The present Invention relates to a corner reflector for us in a radar balloon, especially for use In measuring meteoro logical parameters, furthermore, for use as a radar marker e.g. in life-saving service and for other objects. As regards known technology in the Art, we especially refe to US-PS 2 463 517, 2 888 675, and 3 276 017, DE-PS 1 12 192, and GB-publ. 2 152 785. All mentioned publications are more or less concerned wit the object which the present invention intends to achieve however, they fail to do so. A radar balloon should provide the best possible reflection at the same time as it should use a small volume of gas. Th principle of placing a corner reflector in a balloon i previously known, as mentioned, but it was difficult to hav the reflector fully expanded. Especially, in case o deviation from the orthogonality of various planes, efficien reflection is reduced. Expansion of the balloon when it i filled, or in connection with its ascent in the atmospher according to known technology, may deform the reflector, an cause high mechanical loads on the structure, especially i case of meteorological balloons, which are also subjected t great variations of temperature. A freely rotating balloo may remain in a position with one plane almost in paralle with the radar beam and may, thus, provide bad or even zer reflection. A corner reflector with eight internal corner will always have half of the internal corners positioned i radar shadow. It is an object of the present invention to improve know technology and to provide designs which in a novel manne increase the ratio between reflection/range and utilize volume of gas, and which are also simple in manufacture. Th invention is based on a reflector in which the reflectin plane is suspended from a cord frame system of substantiall non-elastic cords which at the same time defines the angl between planes and distends the radar reflector in the shap of a reflecting net, a cloth, a sheet, or the like, hereafte called a sheet. Accordingly, the present invention relates to a corne reflector to be suspended in a radar balloon, and th invention is characterized by the fact that the reflector i formed by a distended, substantially non-elastic cord fram system with a reflecting sheet attached to the same, so tha all three orthogonal planes are only in physical contact, vi the cord frame system, and the the external nodes at the sam time serve as suspension points. The invention also relates to a balloon of a flexibl material for internal suspension of the above disclose corner reflector, which is characterized by the fact that i has at least the same number of corners as the reflector and that they may be directly secured to the reflector t distend the reflector corners in case of gas filling an expansion. According to the invention the cord frame system is expande by the balloon. Each sheet member is in principle separate from the other sheet members and from the balloon cloth to b freely suspended, so that no friction will occur due t lateral forces, which might destroy the angle between variou planes. The shape of the reflector is only to a very smal degree influenced by variations in the tensional load fro the balloon if the tensional load exceeds a certain minimum An additional sheet area may be extended beyond the oute edges of the cord frame system by the aid of lightweigh stays or profiles resting or balancing on the distended cor frame system and on the sheet. A reflector used as a radar marker in- life-saving service o as a dummy target for civil or military purposes, should hav 8 internal corners to be able to reflect incident radiatio from all arbitrary directions. A reflector to be used for meteorological purposes need no have more than four internal corners, since the reflector ca be orientated by suitable means to make the same side alway face downwards. A balloon of the present kind is, preferably, made fro single, if desired, combined webs of a resilient gastigh cloth, sheet or the like, here called sheet. The shape of the web is selected to permit the reflector t fill a finished inflated ballon as much as possible, and t permit the reflector to be suspended at the corners. One of the attachment points may in this connection preferably, be combined with a valve/filler neck. Attachment at the corners provides for rapid distension o the reflector and utilizes the resiliency of part of th balloon cloth which is not otherwise subjected to grea elastic loads. In balloons which are to ascend through the atmosphere it i possible to utlize the effect that even a not fully distende reflector will not be able to provide sufficient reflectio at a close range for registration, and that distension i gradually improved as the balloon ascends and expands. Balloons which are intended for great heights may be provide with cords or the like which will adjust the expansion volum to begin with. It will, thus, be possible to achiev sufficient pressure in the balloon to distend the reflecto from the start. As mentioned above, it may be desirable in case of meteorolo gical balloons to ensure permanent orientation in a certai direction. This may, e.g. be achieved by the aid of a weight if desired in the shape of a probe wich is suspended belo the balloon, e.g. for registration of temperature an moisture. By the aid of a suitable design of the balloon or by the ai of attached fins it is also possible to achieve controlle rotation of the balloon about a vertical axis, which wil statistically provide for good reflection. The invention will be disclosed in more detail with referenc to the accompanying drawings, in which Figures 1-3 show sheet members for the reflector with cords in a dashed line; Figure 4 shows a completed reflector; Figure 5 shows a distension of the reflector area; Figure 6 shows a continuous and unfolded blank for a balloon; Figure 7 shows the same blank in a partly folded and welded design; Figure 8 shows a finished balloon with reflector and probe; Figures 8 and 10 show variants of the balloon cloth in Figure 7; Figure 11 shows a variant of the square marked ghij in Figure 6; and Figures 12 and 13 show a balloon blank for a reflector having eight internal corners. As mentioned above, it is a characterizing feature of th invention that the reflector is suspended in a substantiall non-elastic cord frame system which clearly defines th positions of three orthogonally intersecting planes, and i in principle provided with the reflecting sheet, so that eac plane adjusts quite freely in relation to the other plane and in a direction which is predetermined by the cord fram system. The cords may at the same time be used to tensio each of the planes. The reflecting sheet of a corner reflector according to th invention must show sufficient conductivity to provide thre separate reflections. Characteristically, a 0.003 m aluminium sheet at 9 GHz will provide approximately 0.9 time what is achievable by the aid of a thicker sheet, wherea 0.0005 mm provides 0.08 times what is theoretically achiev able. In Figures 1 - 5 the principle of a cord frame system an freely hanging sheet, as discussed above, is Illustrated b an embodiment comprising a reflector with four interna corners. Cords 2 may be secured in place on sheet members while th latter lie flat. Further mounting comprises connecting th cords from various members at the corners. With sheet 1 forming a horizontal plane, both vertical planes are to form diagonals AC, and BD, respectively in 1. At least one of said planes must be split along the line of intersection 6 between said two vertical planes for them to be freely tensioned in a right-angled manner. The other vertical plane must be split at least sufficiently to permit cords 2 to be freely tensioned. Also, the cords should go in differently at points of intersection F/F' of both vertical planes, so that the cords may arrange them¬ selves freely. A complete reflector, cf. Figure 4, is achieved when B i secured to B', D to D', C to C, A to .A*, and E to E'. Attachment of cords is essential to the invention, since th angle betwen planes i determined by the nodes. Outside th nodes the cords may be used to suspend the reflector. Figure 4 shows a finished reflector in a distended state Before it is arranged in the balloon, the vertical planes m be folded by simple folds on triangles 3-5, so that point will sit towards the center of 1 and the remaining reflecto will be in parallel with 1. Another variant of the reflector according to the inventio may be achieved by substituting triangle 3 in Figure 2 b corresponding members 4 and 5 in Figure 3. By placing a additional set of triangles in Figures 2 and 3 symmetricall to sheet 1, a reflector with eight internal corners i achieved. The shape of members is not limited to the shape indicated i Figures 1-4, as long as orthogonality is maintained. Figur 5, thus, shows a possibility of increasing the active are when the distance between points of suspension is given. I stead of cutting the sheet along straight line HI, a stay is attached to the sheet, which will, in turn, balance o cord 2, so that an additional area GHI is achieved which i in the same plane with the remaining sheet 7. The reflecto enlargement may be used along all external edges of th reflector, and one or a number of stays may also be use along each edge. Another embodiment for enlarging the reflector area i achieved by stretching cords 2 by the aid of small frame close to the point of suspension. Said frames will absor tension of the cords to ensure the same tension as If th cords had extended to their tie-up points. The frames may b plates or frames with three or four corners. An essential feature of the balloon according to the presen invention is that it consists of single and, if desired connected plane members of a resilient material, and that th edges to be secured to close the balloon have equal length in pairs, and that corners are shaped which may serve a points of attachment for the reflector. Balloon corners may be attached directly to reflector corner so that the balloon corners are retracted when the balloo expands. In this manner the resiliency of the balloon clot may be utilized in an area which is not otherwise subjecte to great tensional loads due to expansion. The shape of faces may be selected from manufacturin considerations, and based on the concept that the balloo should sit as tightly as possible around the reflector t reduce the utilized volume of gas. A balloon of the same original shape as the reflector o Figure 4 may be manufactured from a running web of cloth, a shown in Figure 6. Figure 7 shows the same cloth in a folded state along f'k' and, furthermore, welded along k'(l'/j'). For manufacture, the cloth may be folded in such a manner that pieces are cu for the balloon directly in the shape as shown in Figure 7. Another possibility in case of difficulties in procurement o wide cloth, may be to let one or both squares g'h'i'j', and e'f'k'l' be manufactured separately to be welded to squar f'g'j'k' to form the shape as shown in Figure 7. The reflector may be mounted in the balloon by providing plane folded reflector in the centre of square g'h'j'k' with reflector corners and securing cords facing the corners o the cloth. E" will sit centrally on the square and is attached to k' by lifting e' and pulling k' to E" an oining. Securing in k' may suitably be combined with securing valve/fillerm neck. The balloon is finished tightly by e' being pulled to i' an f to h', followed by welding along g'(h'/f' )(i'/e' )-( '/I' ) Cords from the corner reflector may be attached to th balloon corners by binding, clamping, glueing, welding o attaching in another manner. The cords there may, suitabl be provided with small sferes, knots or the like to facilit ate securing operations. By evacuating remaining air balloon is, thus, achieved which can readily be packed an transported to the site of application. A distinctive feature is that the manufacturing operation maynly occurs in one plane. An inflated radar balloon with a probe, or a stabilizin weight 12, respectively, is shown in Figure 8. Afte inflation the balloon will look approximately like a spher with inwards curved points of attachment. Variants of a cloth blank, as shown in Figure 7, is shown i Figures 9 and 10. Inter alia, they are advantageous in tha they are simple and may be manufactured from a narro straight running web. In Figure 9 square g'h'i'j' is reduce to a parallelogram g"h"i"j", and in Figure 10 parallelogram e'f'k'l' and g'f'k'j' are reduced to a square e'"f'"k''' 1'", and g" - f ' 'k" '1" '. Manufacture of the balloon may b quite analogous with that of the cloth blanks in Figure 7 and for the rest similar variants are, obviously, true. The detail shown in Figure 11 shows another variant of squar g""h""i""j"". The distinct feature of this embodiment is possibility of achieving rotation by the aid of rotationa symmetry about a central normal so -that the balloon wil rotate during its ascent. Complete symmetry is not critical, provided that the balloo is made to rotate sufficiently and remains relatively stable In the same manner as for squares, other dynamically balance details may be arranged in other places of the balloon b design of the cloth blank, in welding operations, or b securing fins or the like. A balloon with eight internal reflector corners has si points of attachment. In the same manner as the reflector the balloon may also be made symmetrical about a correspond ing plane of mirror symmetry, closer to what would otherwis be the corresponding square ghij . Starting with the clot blank in Figure 7, the square may be replaced by a piec making the balloon blank symmetrical about a plane normal t the paper along line gj , as shown in Figure 12. The opening between e'l' and mJ' is most advantageous i mounting, as compared to a blank with the same extent wher e'l' and ml' are continuous. When m is displaced to M, and to N, as shown by arrows in Figure 12, it is immediatel possible to recognize the circumference of the blank i Figure 7. A corner of the reflector Is attached to o and the reflector is laid down on square g'NMj ' in a manner cor¬ responding to that mentioned above regarding square g'h'i'j'. Further mounting operations may correspond to what is indicated as regards the cloth blank shown in Figure 7. Alternative shapes may also be used, e.g. as shown in Figures 9 and 10, and this may, furthermore, be combined with various designs as regards the two halves divided by j ' , and individually with each of said flat pieces. In Figure 13 an additional variant is shown. Arrows indicat how the same circumference as in Figure 7 may be achieve using the above mentioned mounting.

Claims: PATENT CLAIMS: 1. A corner reflector to be suspended in a balloon, c h a r a c t e r i z e d i n that the reflector is mad of a tentered substantially non-elastic cord frame syste (2) with a fixed reflecting sheet in such a manner that th three orthogonal planes only are in physical contact, vi the cord frame system, which in external nodes at the sam time serves as a point of suspension. 2. A reflector as stated in claim 1, c h a r a c t ¬ e r i z e d i n that cords (2) are fastened along th edge of a partial blank (1, 3-5), which is to form th reflecting plane, and that cords with sheet are then joine to a substantially non-elastic cord frame system. 3. A reflector as stated in claims 1 and 2, c h a r a c t e r i z e d i n that one or a number o stays (8) are attached across one or a number of externa edges on the cord frame system to distend sheet beyond th edge of the cord frame system in the same plane as the shee inside said system. 4. A reflector as stated In claim 1, c h a r a c t ¬ e r i z e d i n that the projecting pointed corners ar cut off and that the tension of the cord frame system i absorbed by small frames which have, in turn, fastenings t distend the whole reflector. 5. A balloon of a resilient material for internal suspension o a corner reflector as stated in claim 1, c h a r a c t e r i z e d I n that it has at least a many corners as the reflector, and that they may be attache dvrectly to the reflector, and will curve inwards, and wit full force distend the reflector corners in case of ga filling and distension. 6. A balloon as stated in claim 5, c h a r a c t ¬ e r i z e d i n that it comprises balloon blanks (9, 10 11, 13, 14), which are folded and welded along lateral edge in pairs and of equal length to provide a tight balloon, an that the reflector is placed inside and is attached befor the balloon is welded. A balloon as stated In claim 5, c h a r a c t ¬ e r i z e d i n that one corner also comprises a filling means for gas. 8. A balloon as stated in claim 5, c h a r a c t ¬ e r i z e d i n that it comprises an internal reflecto (Figure 8) with four internal corners facing down. 9. A balloon as stated in claim 8, c h a r a c t ¬ e r i z e d i n that it, furthermore, comprises a weigh for directional stabilization of the balloon, preferably i the shape of a probe. 10. A balloon as stated in claims 8 and 9, c h a r a c t e r i z e d i n that it is designed t provide for rotation about a vertical axis during its ascent

Inventors: BJORDAL ODDVAR, FYKSE HAAKON, BJORDAL, ODDVAR, FYKSE, HAAKON
Applicants: BACO IND AS, BACO INDUSTRIER A/S
Application year: 1989
Main classification: H01Q15
IPC codes: H01Q15