WO2014064700A1

WO2014064700A1 - String assembly

Info

Publication number: WO2014064700A1
Application number: PCT/IL2013/050867
Authority: WO
Inventors: Abraham Aharoni
Original assignee: Israel Aerospace Industries Ltd
Current assignee: Israel Aerospace Industries Ltd
Priority date: 2012-10-28
Filing date: 2013-10-24
Publication date: 2014-05-01
Anticipated expiration: 2015-04-28
Also published as: WO2014064700A8; IL222717A0

Abstract

A string assembly is provided defining at least one open cell. In at least some example, each cell includes one or more continuous primary string segment in open looped configuration forming a periphery of a respective open cell, and a retainer arrangement. The one or more primary string segment in such an open looped configuration operates to selectively lock onto an external object in response to the external object being selectively introduced into the open cell and into abutting contact with the periphery. The one or more primary string segment in such an open looped configuration operates to selectively unravel in the absence of such abutting contact and in the absence of the retainer arrangement being operational. Furthermore, the retainer arrangement, when operational, is configured for retaining one or more primary string segment in such an open looped configuration, at least in the absence of such abutting contact.

Description

STRING ASSEMBLY

TECHNOLOGICAL FIELD

The presently disclosed subject matter relates to string structures and string assemblies, in particular to string structures and string assemblies that form nets.

BACKGROUND

Nets and net-like structures/assemblies, collectively referred to herein as nets, are well known and have many uses, including capturing objects therein. Nets commonly have a number of strings arranged in the form of a 2-dimensional array of open cells, and comprising nodes where the strings intersect. Conventionally, permanent knots are formed at the nodes, for maintaining the form of the net array.

By way of non-limiting background, an intercept device for flying objects is disclosed in US 6,626,077. The device is made of a light-weight, packable structure made of a pliable, tear resistant material that can be expanded to a large web-like structure by means of a deployment device, into the path of a flying weapon. To capture, hold and reduce the velocity of intercepted flying objects, activatable resistance bodies are incorporated into uniformly distributed masses that are connected to the perimeter of the web like structure. Contractable sections of the web, made of cable-like structures, connected to perimeter masses, act as drawstrings upon collision with flying object. This causes closure of the web around the flying object as a result of the mass's inertia and added resistance from deployable resistance structures that place tension on drawstring structures of the web. The flying object is subsequently captured within the web, held secure and it's velocity rapidly reduced.

Also by way of non-limiting background, WO 2007/008960 discloses a system having a containment blanket, and a launcher configured to launch the containment blanket and logic configured to deploy the containment blanket. The containment blanket is configured to encompass an incoming projectile.

Also by way of non-limiting background, various nets or the like are disclosed in US 2004/0132362 and US 6,244,803. GENERAL DESCRIPTION

According to a first aspect of the presently disclosed subject matter there is provided a string assembly defining at least one open cell, comprising;

at least one continuous primary string segment in open looped configuration forming a periphery of a respective said open cell, and further comprising a retainer arrangement, wherein:

(a) said at least one primary string segment in said open looped configuration is configured:

- for selectively locking onto an external object in response to the external object being selectively introduced into said open cell and into abutting contact with said periphery; and

- for selectively unraveling in the absence of such abutting contact and in the absence of said retainer arrangement being operational;

and wherein

(b) said retainer arrangement when operational is configured for retaining said at least one primary string segment in said open looped configuration at least in the absence of said abutting contact.

On the other hand, the retainer arrangement is considered to be "non- operational" when it is mechanically or otherwise incapable of retaining the primary string segment in the aforesaid open looped configuration at least in the absence of the aforesaid abutting contact between the external object and the periphery - for example the retainer arrangement can become non-operational by mechanically failing (e.g. breaking) or by becoming disassembled.

In at least some examples, the string assembly comprises a plurality of said open cells and a corresponding plurality of said primary string segments, each said open cell comprising a respective said primary string segment in a respective said open looped configuration, wherein said retainer arrangement is configured for retaining each said primary string segment in the respective said open looped configuration, independently from one another. Additionally or alternatively, in said open looped configuration each respective said primary string segment is configured to lock onto the external object at least partially via frictional contact between overlapping parts of the respective said primary string segment.

Additionally or alternatively, in said open looped configuration the respective said primary string segment is configured to lock onto the external object at least partially via frictional contact between a portion of the respective said primary string segment and the external object.

For example, at least one said looped configuration has a form of a clove hitch knot or equivalents thereof, or a form resembling a clove hitch knot or equivalents thereof, or alternatively comprises any one of: a girth hitch knot, a rolling hitch knot, a constrictor knot, or equivalents thereof, or any knot arrangement that is self-locking onto said external object that is inserted thereinto.

Additionally or alternatively, said retainer arrangement comprises at least one mechanical retainer configured to become non-operational when a respective primary string segment is subjected to a load exceeding a predetermined load threshold, said load being induced in the respective primary string segment in response to the external object being selectively introduced into said open cell and into abutting contact with said periphery.

Additionally or alternatively, said retainer arrangement comprises at least one secondary string segment engaged to a respective said primary string segment; alternatively, said retainer arrangement comprises any one of: a cement or resin material engaged to a respective said primary string segment; or a plastic element or a metal element clamped onto, molded onto or heat shrunk onto respective said primary string segment.

Additionally or alternatively, at least one said primary string segment is provided excluding strength-reducing knots formed therein, such strength-reducing knots being self-locking and including bends of small-radius as compared with a thickness of the primary string segment.

Additionally or alternatively, each said open looped configuration excludes, i.e., has an absence of, strength-reducing knots formed by the respective primary string segment. Additionally or alternatively, at least one said primary string segment in said open looped configuration is intertwined with respect to an adjacent said primary string segment in said looped configuration.

Additionally or alternatively, the string assembly comprises a string sub- assembly including a plurality of said primary string segments serially joined end-to- end forming a corresponding plurality of said looped configurations in adjacent serial relationship. In some examples, the string assembly comprises at least two said string sub-structures in juxtaposed relationship, or at least two said string sub-structures intertwined with respect to one another. For example, said at least two said string sub- structures are connected together via said retainer arrangement.

Additionally or alternatively, each of one, each of more than one, or each one of all of the primary string segments are extended to connect to a payload, for example a distant payload.

Additionally or alternatively, a continuous string element integrally comprises said plurality of said primary string segments in serial relationship.

Additionally or alternatively, said at least one primary string segment has a mechanical strength greater than a mechanical strength of the retainer arrangement.

Additionally or alternatively, said at least one primary string segment is configured for withstanding an impact from a body traveling at high velocity transverse to a longitudinal axis of the primary string segment. For example, said high velocity is a velocity greater than 400m/s, and/or greater than 500m/s, and/or greater than 600m/s, and/or greater than 700m/s, and/or greater than 800m/s, and/or greater than 900m/s.

Additionally or alternatively, said open cells are arranged in a general two- dimensional array and wherein said retainer arrangement is configured for retaining said plurality of primary string segments, each in corresponding said looped configuration, at nodes of said array. For example, said plurality of primary string segments that form at least one row of said open cells and/or that form at least one column of said open cells of said array is formed from a single continuous length of string. For example, the entire array is formed from a single primary string segment that is looped multiple times to form all the multiple open looped arrangements for the array. For example, each row of the array is formed from a single primary string segment that is looped multiple times to form all the multiple open looped arrangements for the respective row of the array. For example, each column of the array is formed from a single primary string segment that is looped multiple times to form all the multiple open looped arrangements for the respective column of the array.

In at least some examples, said cells of said array are generally polygonal. In at least some examples, said cells of said array are generally rectangular; optionally, said retainer arrangement comprises a secondary string segment co-extensive with a corresponding side of a plurality of said generally rectangular cells; optionally, said retainer arrangement comprises a pair of secondary string segments, each co-extensive with a corresponding side of a plurality of said generally rectangular cells.

Additionally or alternatively, the string assembly is configured for unraveling at least one said open looped configuration located adjacent to an impact cell while remaining mechanically connected hereto on impact of the external object with said impact cell.

Additionally or alternatively, some of said open looped configurations, located in a ring around and adjacent to an impact cell, are configured for unraveling while remaining mechanically connected thereto responsive to impact of the external object with the impact cell, said impact cell being chosen from said plurality of open cells. Additionally or alternatively, some of said open looped configurations, located in each of two or more concentric rings around an impact cell, are configured for unraveling while remaining mechanically connected thereto responsive to impact of the external object with the impact cell, said impact cell being chosen from said plurality of open cells. Optionally, said respective open looped configurations are configured for unraveling via mechanical failure or disassembly of the respective said retainer arrangements, wherein said mechanical failure of the respective said retainer arrangements being responsive to loading of the failed retainer arrangements beyond a failure loading limit due to said abutting contact between the external object and the respective said periphery of the impact cell.

Additionally or alternatively, said external object is a moving object.

Additionally or alternatively, said external object can comprise, for example, a projectile for example a missile or warhead, moving in the atmosphere, or moving through water, or moving in space. Alternatively, such an external object can comprise a satellite or spacecraft travelling in space. Alternatively, such an external object can comprise an aircraft or any air vehicle, manned or unmanned, travelling in the atmosphere. Alternatively, such an external object can comprise water borne craft, for example a surface water craft, or an underwater craft, for example a torpedo.

For example, said external object has a transverse cross-sectional profile that increases along a longitudinal direction generally orthogonal to a respective said cell. For example, the external object has a conical, frusto-conical or ogive shape.

Additionally or alternatively, said at least one primary segment is made from any one of Kevlar, Dyneema, Carbon fiber artificial spider web.

Additionally or alternatively, each said primary string segment comprises a plurality of strand elements.

Additionally or alternatively, each said primary string segment comprises at least a first strand element and a second strand element, and wherein said first strand element is configured for providing better performance than said second strand element with respect to said locking, and wherein said second strand element is configured for providing better performance than said first strand element with respect to said unraveling.

Additionally or alternatively, at least one said open cell comprises at least two said open looped configurations in general concentric relationship with one another and having respective said peripheries of different lengths one from another. Optionally, each said open looped configuration in said concentric relationship is configured for locking with the external object in succession with one another.

According to the first aspect of the presently disclosed subject matter there is also provided a net comprising a string assembly as defined above. Optionally, the net further comprises a payload. For example, said payload is one of:

affixed to the net via a length of string section different from said at least one primary segment of a respective said open looped configuration, said length of string section having greater elasticity than that of the respective said at least one primary segment; and

comprises a plurality of payload items distributed over the net.

In at least some examples, said payload is an explosive device; optionally, said payload is configured for detonating according to predetermined criteria after the external object establishes said abutting contact with said net. Additionally or alternatively, said payload is configured for selectively inducing a drag force to said net; for example, said payload comprises at least one parachute; additionally or alternatively, said payload is configured for deploying according to predetermined criteria after the external object establishes said abutting contact with said net. For example, said predetermined criteria include an elapsed time after the external object establishes said abutting contact with said net.

For example, the net is further configured for maintaining a particular spatial attitude with respect to the Earth, at least until the external object establishes said abutting contact with said net. For example, said spatial attitude includes a non- horizontal attitude of the net. According to a second aspect of the presently disclosed subject matter there is provided a method comprising:

• providing a net as defined above for the first aspect of the presently disclosed subject matter;

• deploying said net at a location intersecting a projected path of the external object;

• allowing the external object to become introduced into any one said open cell and into abutting contact with a respective said periphery thereof to thereby lock said cell onto the external object. According to a third aspect of the presently disclosed subject matter there is provided a method comprising:

• intercepting a moving object with at least one of a plurality of open looped elements of a net assembly, each said open looped elements being formed by respective primary string segments and configured for providing a friction lock when in contact with the external body therein, said looped elements having an absence of structural ties;

• frictionally locking the moving object with the respective at least one said open looped element.

Optionally, the method further comprises the step of allowing unraveling of at least one said open looped elements located in at least one concentric ring around the at least one said open looped element. According to a fourth aspect of the presently disclosed subject matter there is provided a net assembly comprising a plurality of open cells, the net assembly comprising a plurality of primary string segments, each primary string segment being looped in an open looped configuration to define a respective said open cell, wherein said open looped configurations have an absence of a strength-reducing knot formed by the respective primary string segment, the net assembly further comprising a mechanical retainer arrangement configured for retaining said primary string segments in said looped configuration while the respective said primary string segments are subjected to loads below a predetermined threshold, each said cell being configured for locking therein an external object that is brought into abutting contact with a periphery of the respective cell to thereby load the respective said primary string segment to loads exceeding said threshold while being mechanically connected to a remainder of the net assembly via at least some of said primary string segments. According to a fifth aspect of the presently disclosed subject matter there is provided a net assembly comprising an array of primary string segments defining a plurality of open cells and nodes, said primary string segments being in open looped configuration to define respective said open cells, wherein said primary string segment s have an absence of strength-reducing knot formed therein.

According to a sixth aspect of the presently disclosed subject matter there is provided a net assembly comprising open looped elements formed by respective primary string segments and configured for providing a friction lock when in contact with an external body therein, said looped elements having an absence of structural ties therein.

According to one or more of the above first through sixth aspects of the presently disclosed subject matter, and without being bound to theory, the impact between an external object and an open cell of a corresponding string assembly is considered to develop as follows.

First there is an initial contact between the external object and the respective open cell, and this is followed by close abutting contact between the full perimeter of the open cell and the external object. In an ideal case, when the cross-section of the external object is circular and the trajectory of the external object is accurately centered so that the external object enters the respective open cell (which is also assumed to be circular) at its dead center, then such contact is made simultaneously over the full periphery of the open cell. Statistically, such a collection of circumstances is not considered to have a high probability of occurring in practice. Rather, in general such initial contact is often made at one point or area on the periphery, or perhaps a small number of points or areas.

In at least some examples of the presently disclosed subject matter, the respective open cells are formed as polygons. In cases in which the trajectory of the external object is centered with respect to the open cell, and the open cell is in the form of an equal-sided polygon (i.e., at sides of the polygon are equal to one another in length, such as a square or other regular polygon for example), such initial contact is nominally made on all the sides of the polygon simultaneously, with the number of contact points equal to the number of sides. Alternatively, in cases where the open cell is formed as a polygon with unequal sides, such as a rectangle (or another irregular polygon) for example, such initial contact is nominally made on the longer sides (which are closer to the center of the polygon or rectangle), and if there are a number of sides of equal length, such as the in a rectangle, then such initial contact can be made on these sides simultaneously.

Finite element simulations of an external object impacting on an open cell of string assembly indicate that the worst case in terms of the maximal stress buildup in the respective primary string segment after impact occurs when the impacting external object impacts the center of the cell, wherein several sides or points of the open cell are impacted simultaneously by the external object. Other such simulations also indicate that an open cell formed as a polygon shape with un-equal sides can withstand a higher velocity impact than an open cell formed as a polygon shape with equal sides.

It is considered that, emanating from each point of such initial contact, tensile shock fronts propagate in either direction along the respective primary string segment away from the initial impact point (also referred to interchangeably herein as the initial contact point). Without being bound to theory, it is further considered that the magnitude of the tensile shock fronts depends only on the relative velocity between the external object and the primary string segment of the open cell, and on some material properties of the string segment of the open cell. Again without being bound to theory, it is considered that the magnitude of the tensile shock fronts does not depend on the mass of the external object (with respect to which, the mass of the primary string element can be negligible), nor on the diameter of the primary string element (and thus the cross-sectional area thereof). Again without being bound to theory, it is considered that this non-dependence on the diameter or cross-sectional area of the primary string element is due to the nature of the impact which forces the primary string element to strain at the rate it is impacted onto by the external object; further, due to the large differences in mass between the primary string element and the external object (which is expected in many applications), the rate of strain is determined only by the relative velocity between the primary string element and the external object. Thus, even if a thin primary string element is replaced with a thicker primary string element, it will still be strained by the same amount, and the resulting stress (which is related to the aforesaid tensile shock fronts) is thus independent of the diameter or cross-sectional area of the primary string element.

The level of stress induced at the initial impact point determines whether or not the primary string segment can withstand the direct impact between the primary string element and the impacting external object. At very large relative impact velocities the stress induced at the point of contact can exceed the breaking stress of the material from which the primary string element is made, and the primary string element then breaks at the point of impact. In examples where this material is chosen from high tenacity materials, for example materials marketed under the name of Dyneema or Kevlar, breakage of the corresponding string segments at the contact point will occur at impact velocities much higher than 400m/s, and even exceeding 800 m/s or 900 m/s.

In conditions under which the primary string segment does not break due to the initial impact stress, the primary string segment still has to withstand the interaction of tensile shock fronts emanating from each of the different points of contact. This interaction can be in the form of constructive interference, and the magnitude of the resulting tensile shock fronts depends on the geometry of the impacted open cell and the location of the points of contact along the periphery of this open cell. For example, if the open cell is in the form of a regular polygon such as a square, for example, and the cell is impacted directly at its center, tensile shock fronts emanate at each of the four initial contact points at the center of the four sides of the open cell. The geometrical symmetry of the open cell results in the nominally simultaneous arrival of tensile shock fronts from two adjacent contact points at half the distance between these initial contact points (which occurs at the location of the corner of the square cell). The time interval t to this arrival from the initial contact can be determined from the following relationship: t = ac/2 (1)

where a is the length of the side of the square cell, and c the velocity of the stress front.

Depending on the actual geometry of the open cell, higher stress levels in the primary string segment can be induced due to superposition of the tensile shock fronts and the reflections from sharp bends along the periphery of the primary string (such as the corners of the square cell, or the rejoins of intersection of the loops forming a circular open loop cell). Clearly, the primary string segment will break under conditions in which such higher stress levels exceed breaking stress of the primary string segment.

Relationship (1) above indicates that the timing for arrival of two tensile shock fronts at a corner of the open cell can be staggered so that the overall superposed stress level at the corner is correspondingly reduced. Thus, if the open cell is formed as an irregular polygon with unequal sides, the arrival of each of the stress fronts from adjacent initial contact points at the corner is staggered, and the maximal stress level at the corner is thus lower than would be the case if the cell is formed as a similar polygon but with equal sides. Hence, providing the open cells as polygons with unequal sides, for example rectangles, provides advantages over other forms (such as for example regular polygons, equal sided polygons, or circles) for the open cell regarding its capacity to withstand the initial impact of an external object.

Furthermore, in cases where the trajectory of an external object is not accurately centered with respect to the respective open cell, the timing of the arrival of the shock fronts from adjacent initial contact points to corners of the polygonal open cell is similarly temporally staggered. Therefore, as indicate above, the highest stress induced in the primary string segment is when an eternal object strikes and impacts the respective open cell accurately centered with respect thereto rather than when the impact is off-center. Following the initial stress that develops in the primary string immediately following impact, the primary string is gradually forced into full abutting contact with the external object while two secondary processes take place:

In the first secondary process, the open cell is forced onto the external object, the primary string segment of the respective open looped configuration eventually stretches over the perimeter (e.g. circumference) of the external object, and the primary string segment experiences a circumferential stress as the front section of the object thrusts forward to tighten the respective open looped configuration outward. Such a front section increases in cross-section in an aft direction, and can be, for example, conical in form.

In the second secondary process, tensile stress fronts propagate outward towards the ends of the respective string assembly. In some examples the string assembly comprises payload items connected to the string assembly via extended portions of the primary string segment of the string assembly, for example. In such examples, as the stress fronts reach these payload items they are reflected and proceed to accelerate each of the payload items. The outcome of this process depends on the elasticity of the respective primary string segment, the length of these extended portions, the elasticity of these extended portions of the primary string segment, and the mass of the payload items. For sufficiently long extended portions of the primary string segment, sufficiently elasticity of these extended portions, and sufficiently small object mass, the primary string segment is able to accelerate the payload items so that these eventual move at the same velocity of the external object. The extended portions of the primary string segment attached to the payloads can optionally be made from a separate string section with increased elasticity to optimize the process of accelerating the payloads.

Either of these two secondary processes can lead to a break of the primary string segment of the open looped configuration of the respective open cell, as further discussed below. Nevertheless, for an impact within a specified performance envelope, the respective string assembly remains intact, is attached to the external object, and is carried by the external object at the object's velocity, while the extended portions of the string assembly with their payload items are carried along.

In examples where the front section of the external object increases in cross- section in an aft direction (for example, the front section is conical), the external object impacts and makes abutting contact with the primary string segment of the respective open looped configuration via this front section. As the external object continues along its trajectory and the open looped configuration accelerates, the open looped configuration is displaced over the surface of the front section in an aft direction, effectively "climbing" up towards the base of the cone. As it progresses aft, the open looped configuration is forced to stretch to occupy a larger inner circle defined by the increasing cross-section of the external object. This increases the normal force, N acting on the respective primary string segment, which, in turn increase the contact friction force

Such increase in the normal force N continues until the resulting friction force F reaches a threshold preventing the open looped configuration from displacing further aft.

If the cone angle of the front section of the external object (or at least the slope of the front section at the point of contact, taken on a longitudinal cross-section of the front section - such a slope is referred to herein as "local slope") increases, then so does the strength of the corresponding normal force N, and of the resulting friction force F. For small cone angles (or small local slopes) the friction is lower and the external object continues to stretch the open looped configuration for longer. Therefore for small cone angles, the more likely failure is by stretching the primary string, whereas for larger cone angle (or large local slopes) if the primary string segment survives the initial impact, it will remain intact when subject to the circumferential stressing by the conical projectile. Similar considerations apply to other external object forms - the larger the slope of the surfaces of the front section, the more likely it is for the failure mode to be related to the direct impact stresses (and will occur at higher relative velocities). In as much as the design of the open cells of the string assembly can accommodate the external object geometry, a higher maximum limiting value for the impact velocity can be achieved with external objects that form larger sloping surfaces at the points of contact with the primary string segment than is the case with external objects that form shallower sloping surfaces at the points of contact with the primary string segment.

Furthermore, it is suggested that, as the process of stretching of the open looped configuration differs from the process of impact in that the stretching process introduces a stress boundary condition, while the latter corresponds to a strain boundary condition, it can be possible to increase the resilience of an open cell of a string assembly to stretch over the increasing cross-section of an impacting external object by correspondingly increasing the cross-sectional area of the primary string segment thereof. As noted above such increase in the cross section of the primary string does not improve the resilience of the string to the initial impact.

The maximal stress developed after impact with a rectangular-shaped open cell is thus considered to be less than the maximal stress developed after impact with a square-shaped open cell, when impacted by a similar external object, such as a missile for example, of circular cross-section. On the other hand, for an impacting external object having elliptical cross-section, a square form for the open cells can better ensure that the impact on adjacent sides of the open cell is staggered, depending on the aspect ratio of the elliptical cross-section.

A feature of at least one example of the presently disclosed subject matter is that the respective string assembly avoids any permanent knots, which could otherwise significantly reduce the overall strength of the respective primary string segments in the string assembly and thereby reduce the loading limit of the string assembly to well below the loading limit of the individual primary string segments of the string assembly. This feature ensures that the strength of the string assembly is not compromised by the presence of permanent knots, or at least minimizes the risk of such strength being compromised, while concurrently allowing the external object to be captured by the string assembly.

Two other features of this and/or at least one other example of the presently disclosed subject matter are that part of the string assembly, for example one open cell thereof, locks onto the impacting external object via the respective open looped configuration, while another part of the string assembly, comprising other, non- impacted, open cells, unravels. The locking feature ensures that the string assembly locks on to the external object after impact and stays affixed thereto, or at least minimizes the risk of the string assembly separating from the external object after impact. The unraveling feature ensures that the non-impacted open cells of the string assembly are minimally loaded after impact, and thus minimizes the risk of reducing the impact resilience of the string assembly. BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the disclosure and to see how it may be carried out in practice, examples will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Figs. 1(a), 1(b), 1(c) are, respectively, an isometric view, a plan view and a side view, of a string assembly according to a first example of the presently disclosed subject matter.

Figs. 2(a), 2(b), 2(c) schematically illustrate various stages in forming the string assembly of Figs. 1(a), 1(b), 1(c).

Fig. 3 illustrates, in isometric view, the string assembly of Figs. 1(a), 1(b), 1(c) in relation to the trajectory of an incoming object.

Fig. 4 illustrates, in isometric view, the string assembly of Fig. 3 just prior to impact with the respective incoming object.

Fig. 5 illustrates, in isometric view, the string assembly of Fig. 4 after impact with the respective incoming object.

Figs. 6(a) and 6(b) schematically illustrate forces between the impacted object and the string assembly, where the object has a relatively large and relatively small cone angle, respectively.

Figs. 7(a), 7(b) are, respectively, a plan view and a side view, of a string assembly according to a second example of the presently disclosed subject matter.

Figs. 8(a), 8(b) are, respectively, a side view and a plan view, of the string assembly of Figs. 7(a) and 7(b) just prior to impact with an incoming object; Fig. 8(c) identifies various rings of open looped configurations of the string assembly of Figs. 8(a) and 8(b) with respect to the projected impact zone.

Figs. 9(a), 9(b) are, respectively, a side view and a plan view, of the string assembly of Figs. 8(a) and 8(b) just after impact with the respective incoming object at the projected impact zone.

Figs. 10(a), 10(b) are, respectively, a side view and a plan view, of the string assembly of Figs. 8(a) and 8(b) after impact with the respective incoming object at the projected impact zone and unraveling of a first ring of open looped configurations of the string assembly around the impact zone.

Figs. 11(a), 11(b) are, respectively, a side view and a plan view, of the string assembly of Figs. 8(a) and 8(b) after impact with the respective incoming object at the projected impact zone and unraveling of a second ring of open looped configurations of the string assembly around the impact zone.

Fig. 12 is a plan view of a string assembly according to a third example of the presently disclosed subject matter.

Figs. 13(a), 13(b) are, respectively, a plan view and a side view, of the string assembly of Fig. 12, illustrating further details thereof.

Fig. 14 is a plan view of a string assembly according to a variation of the example of Fig. 12.

Fig. 15 is a plan view of a string assembly according to another variation of the example of Fig. 12.

Fig. 16 is a plan view of a string assembly according to another variation of the example of Fig. 12.

Fig. 17 is a plan view of a string assembly according to another variation of the example of Fig. 12.

DETAILED DESCRIPTION

Referring to Figs. 1(a), 1(b), 1(c), a string assembly (also referred to interchangeably herein as a "string structure") according to a first example of the presently disclosed subject matter, generally designated 100, comprises a primary string segment 110 and a retainer arrangement 120.

The primary string segment 110 is a continuous length of flexible, high tensile material, typically of generally uniform cross-section along its length, such as, but not limited to, a string. The primary string segment 110 is arranged in a continuous, single, open looped configuration 160 to define an opening 151 having a periphery 155. This opening 151 and the corresponding open looped configuration 160 thereof are collectively referred to herein as an open cell, or simply as a cell 150 of the string assembly 100, the open cell 150 having a characteristic peripheral length CL along the periphery 155. For example, in examples where the open cell 150 is disk-shaped or circular, the peripheral length CL is a circumference length and is related to the diameter of the open cell 150.

As shall become clearer below, the primary string segment 110 in the open looped configuration 160 is configured: - for locking with respect to an external object in response to the external object being selectively introduced into the open cell 150 and into abutting contact with the periphery 155; and

- for unraveling in the absence of such abutting contact (i.e., for unraveling under conditions of zero abutting contact) and in the absence of the retainer arrangement 120 being operational.

As shall also become clearer below, the retainer arrangement 120, is configured for retaining the primary string segment 110 in the aforesaid open looped configuration 160 at least in the absence of the aforesaid abutting contact between the external object and the periphery 155. The retainer arrangement 120 is considered being "operational" when retaining the primary string segment 110 in the aforesaid open looped configuration 160 at least in the absence of the aforesaid abutting contact between the external object and the periphery 155. Conversely, the retainer arrangement 120 is considered to be "non-operational" when it is mechanically or otherwise incapable of retaining the primary string segment 110 in the aforesaid open looped configuration 160 at least in the absence of the aforesaid abutting contact between the external object and the periphery 155 - for example the retainer arrangement 120 can become "non- operational" by mechanically failing (e.g. breaking) or by becoming disassembled.

In this example, the open looped configuration 160 is in a form resembling a clove hitch knot. The string segment 110 thus comprises two consecutive loops 110a, 110b, overlaid on one another, the string segment 110 extending to respective ends 111a, 111b along generally opposite directions. One overlying section 112 of the string segment is overlaid over corresponding sections 113, 114 of the loops 110a, 110b to form an overcross.

For example, and referring to Figs. 2(a), 2(b) and 2(c), such an open looped configuration 160 can be formed starting with the primary string segment 110 in general elongate form, i.e. in an essentially unlooped configuration in Fig. 2(a), double-looping the string segment 110 as illustrated in Fig. 2(b) to form consecutive loops 110a, 110b, and bringing the two loops 110a, 110b in overlying relationship such as to provide the overcross of overlying section 112 over sections 113, 114 of the loops 110a, 110b, as illustrated in Fig. 2(c). Alternatively, open looped configuration 160 can be formed by manipulating and moving one end of the string segment 110 along a trajectory defined by the final form of the open looped configuration 160 illustrated in Fig. 2(c).

It is thus evident that the open looped configuration 160, in this example in the form of a clove hitch knot, avoids, i.e., excludes, any permanent knots formed by the primary string segment 110 that can otherwise reduce the strength of the string segment 110.

Herein, "permanent knot" (interchangeably referred to herein as structural ties), in contrast to a clove hitch knot for example, refers to any type of fastening knot that fastens on a string segment by forming a loop around (and in load-bearing contact with) a circumferential periphery of the general cross-section of a part of the string segment, for example at least partially helically, such that application of tension to the string of the fastening knot locks the loop around the full periphery of the aforesaid part of the string segment, thereby significantly weakening the strength of the string segment. In other words, a "permanent knot" is locked by the string itself and is characterized by having loops of large curvature (small radius) in relation to the thickness or diameter of the string segment itself on which the permanent knot is tied. Thus, a "permanent knot" is a type of knot that results in the respective string segment having a relative knot strength significantly less than 100% in the vicinity of the permanent knot, and more precisely the relative knot strength is less than 80%, or less than 70%, or less than 60%, or less than 50%. Relative knot strength, also known as knot efficiency, is conventionally defined as the breaking strength of a knotted string in proportion to the breaking strength of the string without the knot.

Referring again to Figs. 1(a), 1(b), 1(c), the retainer arrangement 120 is engaged to the open looped configuration 160, and in this example retainer arrangement 120 comprises a pair of secondary string segments 122, distinct, i.e. different from or separate from, the primary string segment 110. Each secondary string segment 122 is tied to the open looped configuration 160 at a respective one of two positions PI, P2, which are spaced from one another. At each position PI, P2, the respective secondary string segment 122 is looped around and engages the primary string segment 110 at corresponding parts of the loop 110a, loop 110b and overlying section 112 retaining the open loop cell structure of cell 150. Thus, overlying section 112 is fully or partially defined between the two positions PI, P2. In this manner, retainer arrangement 120 (in this example in the form of the string segments 122) prevents the primary string segment 110 in the open looped configuration 160 from unraveling. In alternative variations of this example, the retainer arrangement 120 can comprise one such secondary string segment 122 (for example located at a position intermediate between PI and P2) or more than two such secondary string segments 122. In this example, each secondary string segment 122 is affixed to itself in its looped configuration, in which it is engaged to the primary string segment 110 at corresponding parts of the open looped configuration 160 in any suitable manner - for example the respective secondary string segment 122 can be tied to itself, or can be welded, mechanically affixed, or be formed as an integral loop (such as for example a ring).

It is evident that the retainer arrangement 120, when thus engaged to the open looped configuration 160, is operational to maintain the spatial relationship that defines the open looped configuration (even though there is, as yet, an absence of any external body in abutting relationship with the periphery 155 of the cell 150), in particular the spatial relationship between the loops 110a, 110b and overlying section 112.

In alternative variations of this example, the retainer arrangement 120 can comprise cement or resin or equivalents thereof, placed onto and around the primary string segment 110, securing the same in place. Additionally or alternatively, the retainer arrangement 120 can comprise pressed strips of metal or other metal elements, or equivalents thereof, used to hold the primary string in place. Additionally or alternatively, the retainer arrangement 120 can comprise plastic retainers or equivalents thereof, clamped onto, molded onto, or heat shrunk onto the primary string segment 110.

The retainer arrangement 120 is configured on the one hand to maintain the form of the open looped configuration even in the absence of any external body being in abutting relationship with the periphery 155 of the open cell 150. On the other hand the retainer arrangement 120 does not itself apply significant loads on the string segment 110, such as could otherwise reduce relative knot strength of the primary string segment 110 to significantly less than 100% in the vicinity of the secondary string segments 122, and more particularly such as could otherwise reduce relative knot strength of the primary string segment 110 to significantly less than 80%, or less than 70%, or less than 60%, or less than 50%. In addition, and as will become clearer below, the retainer arrangement 120 is configured for becoming non-operational, for example mechanically failing (for example breaking or disassembling), at a predetermined load level, allowing the primary string segment 110 to unravel if it remains without a locking external body in abutting contact therewith. As will also become clearer herein, the retainer arrangement 120 can optionally become non-operational once an external locking body is inserted into the open cell 150 in abutting contact therewith, and thus the primary string segment 110 in the aforesaid open loop configuration remains locked onto the external body irrespective of whether or not the retainer arrangement is still intact.

In this example, the ends 111a, 111b of the string segment 110 each extend to a length considerably longer than the peripheral length CL of the cell 150. For example, such a length can be at least 10 times the peripheral length CL.

Referring to Fig. 3, the string assembly 100 further comprises a payload 180, which in this example includes two payload items 182, 184, spaced from one another. Each end 111a, 111b of the string segment 110 being affixed to a respective one of the items 182, 184 (together with the string assembly 100) are supported suspended in midair via lighter-than-air balloons or the like (not shown), or alternatively are following a particular trajectory in the atmosphere following deployment from a carrier projectile or an aircraft, for example, suspended by a pair of parachutes, for example. In alternative variations of this example, the items 182, 184 can be seated or supported on the ground (or on another structure such as for example a pair of spaced towers), such as to suspend the open looped configuration 160 above the ground (or above the other structure). In any case, the open looped configuration 160 is spaced between the two items 182, 184.

Such long lengths are considered to delay and/or dampen the impact experienced by the string segment 110 of the open looped configuration 160 originating from reflection of impact stress wavefronts from the inertia of the payload 180.

In an alternative variation of this example, the payload 180 comprises one such item or equivalents thereof affixed at one end 111a of the string segment 110, while the other end 111b is seated or supported on the ground or on a static structure.

Referring again to Fig. 3, in operation of the string assembly 100, the string assembly 100 and in particular the open cell 150 is positioned to intersect the projected trajectory T of an external object 10 that is moving towards the open cell 150. In particular the projected trajectory T intersects the cell 150 generally orthogonal thereto, i.e., at least sufficiently orthogonal thereto such as to allow the external object 10 to at least partially penetrate into the cell 150 and to subsequently become locked therein. Of course the converse can instead be the case, in that the external object 10 can be static 5 and the string assembly 100 can be moving towards the external object 10; or indeed both the external object 10 and the string assembly 100 can both be moving in the same or different directions but with a relative velocity towards one another.

Referring to Fig. 4 and Fig. 5, as the object 10 follows trajectory T, the object 10 eventually impacts the primary string segment 110, in particular the parts of the primary

10 string segments 110 forming the loops 110a, 110b as the external object 10 becomes introduced into the open cell 150 and comes into abutting contact with the periphery 155. As a result, the open looped configuration 160 of open cell 150 locks onto the object 10 in a manner similar to what would have been the case if the primary string segment 110 in general elongate form (i.e. in an essentially unlooped configuration in Fig.

15 2(a)) would have been manipulated to form the open looped configuration directly on the external object 10, i.e., while being supported by the object 10. In this example, the open looped configuration 160 is in the form resembling a clove hitch knot that locks onto external object 10 in a manner similar to what would have been the case had a general elongate length of primary string segment 110 been directly tied onto the object

20 10 in the form similarly resembling a clove hitch knot. As is well known in the art, a string segment that is tied over an object (e.g. a rod) as a clove hitch knot, such that the object is engaged within the loops of the clove hitch knot, is self supporting once sufficient tension is applied to the string segment. In this example, the aforesaid sufficient tension in the primary string segment 110 is induced responsive to the

25 abutting contact between the external object 10 and the periphery 155. Such a sufficient tension (referred to herein as the load threshold for the open looped configuration 160) is induced in the open looped configuration 160 of cell 150 by virtue of the impact and the subsequent loading of the primary string segment 110 as a result thereof.

Without being bound by theory, the inventor suggests that frictional forces are 30 induced at the overcross between overlying section 112 and sections 113, 114 in the zone Z (see Fig. 1(b), Fig. 1(c) and Fig. 5) between overlying section 112, and/or, frictional forces are induced between the loops 110a, 110b and the external object 10, when the object 10 is engaged in the open cell 150 and is in abutting contact with the periphery 155, in particular where such abutting contact applies the aforesaid predetermined tension to the primary string segment 110. Without being bound by theory, the inventor further suggests that these frictional forces lock the open looped configuration 160 onto 5 the object 10, and prevent the string segment 110 unraveling from the open looped configuration.

As the external object 10 impacts and becomes engaged with the string segment 110, the external object 10 carries the open cell 150 with it (and thus also payload items 182, 184) along its trajectory T. Accordingly, the external object 10 carries with it the 10 string assembly 100, at least directly after impact.

The payload items 182, 184 in this example each comprise at least one of an explosive charge and a velocity retardant mechanism, at least one of which is configured to become activated either via external control (for example by remote control) or in response to predetermined set of conditions (for example via sensors in 15 the payload items that determine that the external object 10 has been locked by the string segment, for example by sensing a sudden acceleration or velocity that accompanies the impact of the external object on the string segment 110).

In further operation of the string assembly 100, the payload items 182, 184 can be activated to disrupt the original trajectory T of the external object 10, in particular by

20 destroying or damaging the external object 10 via the explosive charge that is thus selectively detonated, and/or by significantly reducing the velocity of the external object via the velocity retardant mechanism. The velocity retardant mechanism can comprise, for example, one or more parachutes, balloons or other aerodynamic drag inducing devices or structures, that can be selectively deployed when the payload items 182, 184

25 are activated, which thereby induce a significant drag force and/or instability to the external object 10, forcing the external object 10 away from the trajectory T.

Referring again to Fig. 5, when the primary string segment 110 in the open looped configuration 160 of cell 150 is locked onto the external object 10, the retainer arrangement 120 is no longer necessary for maintaining the open looped configuration 30 160. Thus, optionally, the secondary string segments 122 can be configured to become non-operational (e.g., mechanically break or open or disassemble, etc) when the external object 10 is in the aforesaid abutting contact with the periphery 155 of the open cell 150. For example, the secondary string segments 122 can comprise weak bonds that hold the secondary string segments 122 in ring-form, and that are, on the one hand, mechanically competent to maintain the open looped configuration while the string assembly 100 is being handled, but on the other hand become non-operational (e.g. 5 break or otherwise open mechanically or disassemble), when said predetermined tension is induced in the primary string segment 110 as a result of the external object 10 being locked by the open cell 150. Alternatively, the retainer arrangement 120 is no longer necessary, but nevertheless remains relatively intact and in place after the external object 10 is in the aforesaid abutting contact with the periphery 155 of the open cell 10 150, and the secondary string segments 122 do not necessarily become non-operational (for example do not break or otherwise open mechanically or disassemble) nor significantly load the primary string segment 10.

It is to be noted that the string segment 110 in general, and the open looped configuration 160 in particular, do not have any permanent knots therein. Thus, the

15 ability of the string segment 110 to withstand a high velocity impact from the external object is not significantly diminished with respect to the ability of a datum string segment to withstand a lateral impact from the external object 10 under the same conditions. Such a datum string segment is a continuous length of high tensile material, identical to that of the primary string segment 110, but excluding any loops, bends, or

20 knots of any kind.

Referring again to Fig. 3, the external object 10 in this example comprises transverse cross-sections (i.e., cross-sections generally orthogonal to the direction of motion M or longitudinal axis 15 of the object 10) that are generally circular and that monotonically increase from the tip 11 to a base 12 thereof, defining a generally conical 25 (or alternatively frusto-conical) shape. Furthermore, the characteristic peripheral length CL of the open cell 150 (after allowing for the elongation of the primary string segment 110 under stress) is intermediate between the minimum peripheral length

(in this case, the minimum circumferential length) and the maximum peripheral length CL_max (in this case, the maximum circumferential length) of these circular cross-sections.

30 In alternative variations of this example the external object 10 can instead comprise a non-circular cross-section (for example, oval, elliptical, super-elliptical, polygonal, or equivalents thereof, and so on). Additionally or alternatively, the cross- section of the external object 10 can increase from the tip to the base in a non-linear manner, for example having ogive, part elliptical, part super-elliptical, rounded, or otherwise curved cross-sections taken along planes orthogonal to the transverse sections and aligned with the longitudinal axis 15 of the external object 10. While in this example the external object 10 is axisymmetric about the longitudinal axis 15, in alternative variations of this example the external object 10 can be non-axisymmetric.

In any case the external object 10 comprises a transverse cross-section (i.e., cross- sections generally orthogonal to the direction of motion M of the external object 10) that increases from the tip to a base thereof, and the perimeter of these cross-sections thus increases from a minimum perimeter to a maximum perimeter. Thus, and particularly for cases where the object does not have a circular cross-sections, the characteristic peripheral length CL of the open cell 150, which is the length along perimeter 155, is thus intermediate in value with respect to the aforesaid peripheral length CL_mi_n and maximum peripheral length CL_max of these corresponding cross-sections of the external object 10.

In yet other alternative variations of this example the external object 10 has a generally constant cross-section between the tip 11 and the base 12, and the external object 10 can enter the open cell obliquely to the plane of opening 151, for example.

In any case, the peripheral length CL of the open cell 150 can be designed to be smaller than the base periphery of the smallest external object 10, that it is anticipated to be intercepted by the string assembly 100, allowing for any elongation of the open cell 150 under its operational stress, thereby ensuring that the string assembly 100 can operate effectively with all anticipated external objects, for example in the form of projectiles.

In some cases, it is possible for the primary string segment 110 to mechanically fail after engagement with the object 10, rather than become locked thereon. This can occur immediately following impact with the external object or at a later stage when the primary string is stretched over the circumference of the external object. In such cases, the primary string segment breaks and it is possible, though not necessarily certain, that the string assembly 100 becomes detached from the object 10. Without being bound by theory, the inventor suggests that there are at least two possible mechanisms for such mechanical failure, referred to herein as fail mechanisms (a) and (b) as follows:

(a) Buildup of stress in the string segment 110 due to the transverse loading of the object's impact. This is essentially the same load that would have been applied to a datum string segment, i.e., to the primary string segment 100, had the string segment 110 not been part of the string assembly 100 and been impacted by the object under similar conditions, i.e. the load corresponds to the load that would have been applied transversely to the corresponding datum string segment under similar impact conditions. Again, without being bound by theory, the inventor suggests that this mechanism essentially poses a fundamental limitation on the strength and viability of the string assembly 100 that is a function of the material of the string segment and of the impact velocity between the object 10 and the string assembly 100. In ordinary use of the string assembly 100 according to the presently disclosed subject matter, the material of the primary string segment 110 and the expected impact velocity are such as not to exceed this limitation. The inventor has found the high tenacity materials, such as marketed under the names Dyneema or Kevlar for example, can withstand impact at relative velocities of higher than 400m/s, and up to 800m/s or 900m/s or greater. Thus, in at least some examples of the presently disclosed subject matter, the respective string assembly is configured for maintaining mechanical integrity of the respective primary string segments for impact velocities greater than 400m/s, or greater than 500m/s, or greater than 600m/s, or greater than 700m/s, or greater than 800m/s, or greater than 900m/s.

A subset of the above limitation occurs due to the closed loop geometry of the primary string segment, in that the stress fronts from more than one impact point on periphery 155 can propagate to superpose on one another at different locations along the open loop configuration 160 of open cell 150. This condition necessarily reduces the expected maximum allowable relative impact velocity relative to the theoretical limitation associated with a long, straight string segment where superposition of stress fronts is less likely.

(b) The stress that is induced in the primary string segment 110 along the periphery 155 that originates from the forces exerted on the primary string 5 segment 110 tangentially by the circumferential force generated by the circular sections of a cone-shaped object having respective peripheries increasing (e.g., monotonically) in size from less than to greater than the characteristic peripheral length CL of the cell 150, trying to force open the cell 150.

10 Again, without being bound by theory, the inventor suggests that the slope of the contact surface on the object 10 with the periphery 155 determines which one of the two above mechanisms dominates in any given combination of the material from of at least the outer surface of external object 10, and material from which the primary string segment 110 is made. Thus, in examples where the external object 10 has a conical or

15 frusto-conical part that engages with the string assembly 100, the corresponding cone angle determines which one of two above mechanisms can dominate in such cases. Referring to Fig. 6(a), if the cone half-angle, i.e., angle i is relatively large, such that the resulting friction forces prevent the open cell from moving aft towards the base of the cone, the primary physical effect is that of a transverse impact on the string segment

20 110 at the open looped configuration 160. In this case mechanism (a) dominates.

Conversely, and referring to Fig. 6(b), if the cone half angle, angle a.2 is relatively small such that the resulting friction forces do not prevent the open loop cell from moving aft towards the base of the cone, the primary physical effect is that of a stretching of the primary string segment over the cone, generating large tensile stresses in the primary

25 string segment, which acts to open the cell 150, and mechanism (b) dominates. The actual magnitudes of the angles i and a.2 depend on the material of the outer surface of the external object and the level of friction forces that are generated with the string material.

In any case, and as already referred to above, when such an object 10 having a 30 conical, frusto-conical, or similar forward part that engages with the string assembly

100 by being inserted into the cell 160 into abutting contact with the periphery 155, even a relatively small tensile force (the aforementioned load threshold) thereby applied to the string segment 110 of the open looped configuration 160 will lock and thus secure the external object 10 with respect to the string assembly 100. On the other hand, in the absence of such abutting contact with the object 10, and in the absence of the retainer arrangement 120 being operational, the open looped configuration 160 is unstable and will collapse or otherwise unravel when the smallest tensile force is applied to the string segment 110, even a fraction of the aforementioned load threshold.

For example, the external object 10 can be a projectile (for example a missile or warhead) that it is wished to intercept and optionally neutralize using the string assembly 100. In operation of the string assembly 100, such a projectile having a projected trajectory T can be engaged by the open looped configuration 160 when the trajectory T intersects the cell 150, and the projectile is locked by the string assembly 100. In turn the payload 180 is dragged along with the string assembly 100, and can selectively explode and/or induce significant drag and/or instability to the projectile, thereby causing the projectile to disintegrate or to at least veer significantly from the projected trajectory T, thereby becoming ineffective and/or missing an intended target at the end of projected trajectory T, for example.

In an alternative example, the external object 10 can instead be a probe of an aircraft, and the string assembly 100 can be used for enabling the aircraft to collect the payload 180 via the probe while airborne. Of course the payload 180 can be in this case any payload desired to be thus collected, and does not necessarily include an explosive charge or velocity retardant mechanism. In operation of the string assembly 100, such an aircraft can travel with the aforesaid probe moving along projected trajectory T. The probe can then be engaged by the open looped configuration 160 when the trajectory T intersects the cell 150, the probe becomes locked by the string assembly 100 and thus takes the payload 180 with it as the aircraft moves on. Such a payload can then be selectively released by the aircraft over a designated delivery area, whether the delivery is performed by low altitude dropping or with the aid of a parachute (which can be part of the payload). The release mechanism of the payload can be based, for example, on breaking the primary string segment mechanically (e.g. using a cutting tool) or by applying heat (for example the material Dyneema has a melting temperature of about 150°C, and thus a heating device capable of heating the primary string segment of cell 150 to temperatures higher than the melting temperature of the primary string segment can be used to effectively cut the primary string segment).

Alternatively, the external object 10 can be in the form of an aircraft or drone or other air vehicle, manned or unmanned, which it is desired to intercept and neutralize via the string structure.

Alternatively, the external object 10 can be in the form of a satellite or spacecraft travelling in space, which it is desired to intercept and neutralize via the string structure.

Alternatively, the external object 10 can be in the form of a surface or underwater craft, for example a torpedo, which it is desired to intercept and neutralize via the string structure.

As has already been discussed above, in this example the open looped configuration is in the form resembling a clove hitch knot. However, in alternative variations of this example the open looped configuration can include a form similar to or resembling, for example, any one of: girth hitch knot, rolling hitch knot, constrictor knot, or their equivalents, or any similar knot arrangements that are self-locking onto an external object that is inserted into them.

Referring to Figs. 7(a) and 7(b), a string assembly 200 according to a second example of the presently disclosed subject matter includes at least some of the elements and features as disclosed herein for the first example including alternative variations thereof as disclosed herein, mutatis mutandis, but with some differences, as will become clearer in the following disclosure.

String assembly 200 comprises an array of cells 250, each cell being similar to cell 150 of the first example, mutatis mutandis. While in this example, the cells 250 are similar in size and shape to one another and arranged in a two-dimensional rectangular planar array, in alternative variations of this example the cells 250 can be arranged in any other manner, for example: in hexagonal-type arrays (in which each cell 250 is surrounded by six other cells 250) or equivalents thereof,, and/or in which the cells 250 are arranged in a three-dimensional or non-planar array with respect to one another, and/or the cells 250 are not similar in size and/or shape to one another. Furthermore, while in the illustrated example there are four cells 250, comprising two rows and two columns of cells 250, in alternative variations of this example the array can include less than four cells, for example two or three cells 250, or more than four cells 250, mutatis mutandis.

String assembly 200 comprises a plurality of (in the illustrated example, two) string sub-assemblies, each string sub-assembly including a plurality of (in the illustrated example, two) primary string segments 210 serially joined end-to-end forming a corresponding plurality of looped configurations in adjacent serial relationship. Each primary string segment 210 is substantially similar to the primary string segment 110 as disclosed herein for the first example (or alternative variations thereof) of the presently disclosed subject matter, mutatis mutandis. In this example, each string sub-assembly corresponds to a row of the array of cells 250, and comprises a plurality of (in the illustrated example, two) two primary string segments 210 forming respective open looped configurations 260, each corresponding to a column of the array of cells 250. Each open looped configuration 260 and corresponding open cell 250 are respectively substantially similar in structure and function to the open looped configuration 160 and open cell 150 as disclosed herein for the first example and alternative variations thereof, mutatis mutandis. Thus, in the second example, each open looped configuration 260 is in the form resembling a clove hitch knot, and the corresponding portion of the string segment 210 thus comprises two consecutive and contiguous loops 210a, 210b, overlaid on one another, the portion of string segment 210 extending to respective ends 211a, 211b along generally opposite directions, with one overlying section 212 of the portion of the string segment 210 being overlaid over corresponding sections 213, 214 of the loops 210a, 210b to form an overcross, similar to the corresponding components as disclosed above for the first example, mutatis mutandis, including: consecutive and contiguous loops 110a, 110b; ends 111a, 111b; overlying section 112; sections 113, 114. Also as for the first example, mutatis mutandis, in alternative variations of the second example each of the open looped configuration 260 can instead be in a form similar to or resembling, for example, any one of: girth hitch knot, rolling hitch knot, constrictor knot, or similar knot arrangements that are self- locking onto an external object that is inserted into them.

Furthermore, for each row of the array, the respective plurality of open looped configurations 260, and thus the corresponding open cells 250, are serially joined to one another, so that, for each pair of adjacent open looped configurations 260, the end 211a of one open looped configuration 260 is joined to the other end 211b of the adjoining open looped configuration 260, for example as indicated at "J" in Fig. 7(b). In this example, these adjoining ends are integrally joined to one another and are thus formed from same continuous string element that forms the respective string sub-assembly. In other words, the string assembly 200 is constructed from a number of string subassemblies (corresponding to the number of rows of the array), each being in the form of a continuous string element comprising a plurality of primary string segment 210, and being used to successively form all the respective open looped configurations 260 of the respective row. Optionally, each of the separate string segments 210 can extend to reach and connect to the payload.

While in this example each of the rows of the array of the string assembly 200 is constructed with a respective single, continuous, string element, in alternative variations of this example each of the rows of the array of the string assembly 200 is made from a plurality of separate but contiguous primary string segments or equivalents thereof, joined serially to one another, each such primary string segments including a corresponding open looped configurations 260.

In yet other variations of this example, the full array of the string assembly 200 is constructed with a single, continuous, string element, or equivalents thereof which integrally comprises all the respective primary string segments 210 in serial relationship, and which is used to successively form all the open looped configurations 260 of the array, for example forming each row or column of the array in succession.

In any case, and as seen in Fig. 7(a) but not shown in Fig. 7(b), in each string sub-assembly, the respective plurality of primary string segment 210, the corresponding plurality of open looped configurations 260, and thus the corresponding open cells 250, are also intertwined serially to one another, such that for each pair of adjacent open looped configurations 260 thereof, the loops 210a, 210b of one open looped configuration 260 are also looped around the loops 210a, 210b of the other open looped configuration 260, as generally indicated at "A". Furthermore, each pair of adjacent rows of the array (and thus the respective primary string segments thereof) are also intertwined in parallel with one another, such that for every pair of adjacent open looped configurations 260 (one open looped configuration 260 from each adjacent row), the loops 210a, 210b of one open looped configuration 260 are also looped around the loops 210a, 210b of the other open looped configuration 260, as generally indicated at "B".

In alternative variations of this example, adjacent pairs of open looped configurations 260, and thus the corresponding open cells 250, are not intertwined with one another, but rather the loops 210a, 210b of one open looped configuration 260 are not looped around or otherwise connected in any direct manner to the loops 210a, 210b of the other open looped configuration 260 (except of course by virtue of being in adjacent primary string segments 210). Additionally or alternatively, adjacent pairs of open looped configurations 260 one each from a pair of adjacent primary string segments 210 are not intertwined with one another, but rather the loops 210a, 210b of one open looped configuration 260 are not looped around or otherwise connected in any direct manner to the loops 210a, 210b of the other open looped configuration 260. The entire string assembly 200 in this case is held together with retainer arrangements, 220, which then serve a dual function: retaining the open loop configurations of the open cells intact; and connecting adjacent open loop cells together to form the net-like assembly.

In alternative variations of this example, the retainer arrangement 220 can comprise cement or resin or equivalents thereof securing the primary string. Alternatively pressed strips of metal can be used to hold the primary string in place. Alternatively plastic retainers can be clamped onto, or molded onto or heat shrunk onto the primary strings.

Furthermore, referring again to the plurality of open looped configurations 260 of the string assembly 200, each open looped configuration 260 comprises a corresponding retainer arrangement 220, similar to the retainer arrangement 120 as disclosed herein for the first example and alternative variations thereof, mutatis mutandis.

Thus, the plurality of open looped configurations 260 defines a corresponding plurality of respective cells 250. In this example, the open loop configurations 260 are generally circular when viewed in plan view, as in Fig. 7(a), and thus in the respective rectangular array of cells 250 illustrated in this figure, the string assembly 200 further comprises relatively open nodal zones 290 defined at each node of the array by mutually-facing outsides of four mutually adjacent respective open looped configurations 260.

A feature of at least the second example of the string assembly 200 is that it has the appearance of, and much of the functionality of, a net, a net assembly, a net-like assembly, or a net structure. Furthermore, each open looped configuration 260 is configured to operate in a similar manner to the open looped configuration 160 of the first example of the presently disclosed subject matter, mutatis mutandis. Thus, as external object 10 (for example in the form of a projectile, but can be any other object, for example as disclosed for the first example, mutatis mutandis) follows a trajectory T that intersects one of the cells 250, the external object 10 eventually impacts the respective primary string segment 210 of the respective open cell 250. In particular, as the external object 10 becomes introduced into the respective open cell 250 and comes into abutting contact with its periphery 255, the external object 10 impacts the parts of the primary string segments 210 forming the respective loops 210a, 210b of the respective open looped configuration 260. As a result, the respective open looped configuration 260 of the respective open cell 250 locks onto the external object 10 in a manner similar to that disclosed herein for the open looped configuration 160, mutatis mutandis.

The net-like form of string assembly 200 of the second example of the presently disclosed subject matter, and in particular the inclusion of a plurality of open looped configurations 260 therein, increases the probability of aligning any one of the plurality of cells 250 with the trajectory T, as compared with attempting to align the cell 150 of the single open looped configuration 160 of the first example with trajectory T. At the same time, such increased probability is partly diminished by the statistical chance that such a trajectory T can instead intersect one of the open nodal zones 290, rather than an open looped configuration 260.

Thus, the greater the number of open cells 250 provided by the string assembly, 200, the greater the probability of facilitating intersection of a particular trajectory T of external object 10 with one or another of the respective open looped configurations 260 thereof.

The string assembly 200 is thus configured for locking onto an external object 10. Furthermore, the string assembly 200 can optionally be supported, suspended in mid-air, and/or can be configured for following a particular or random trajectory in the atmosphere, via lighter-than-air balloons or the like (not shown), and/or one or more parachutes, for example. Alternatively, the string assembly 200 follows a particular trajectory in the atmosphere following deployment from a carrier projectile or a carrier aircraft. Alternatively, the string assembly 200 can optionally be supported, for example suspended above the ground, for example on a structure, such that the structure is open and presents the plurality of cells 250 to enable at least one cell 250 to be intercepting an expected or desired trajectory T. In any case the string assembly 200 optionally carries a payload 280, for example similar to payload 180 as disclosed herein for the first example of the presently disclosed subject matter, mutatis mutandis.

Whether the string assembly 200 is made from a single, continuous string element integrally comprising a plurality of primary string segments, or whether the string assembly 200 is made from a plurality of separate primary string segments, the string assembly 200 is configured such that the payloads 280, remain attached to all primary string segments once they are completely unraveled.

The string assembly 200 operates to lock onto an approaching external object 10 with any one of the respective open cells 250. Referring to Figs. 8(a) to 10(b), and for facilitating understanding this mode of operation, the string assembly 200 is shown as net structure comprising a 8x8 rectangular array of 64 open cells 250, each defined by a respective open looped configuration 260, though it is readily evident that this mode of operation can be applied to other designs of the string assembly 200, including more than 64 open cells 250, or less than 64 open cells 250, and/or provided in symmetric or asymmetric arrays of any desired configuration, mutatis mutandis. Furthermore, the circular plan form of the open looped configurations 260 are depicted in these figures as octagons for easier comprehension.

The string assembly 200 operates in a similar manner to the string assembly 100 of the first example, mutatis mutandis. For example, and referring to Figs 9(a) and 9(b) the external object 10, in the form of a projectile for example, having a projected trajectory T can be engaged by one of the open cells 250 when the trajectory T intersects the respective cell 250, and the projectile is locked by the string assembly 200. However, in this example the un-impacted open cells subsequently unravel, in a cascaded effect as described below, reducing the loading on the impacted open cell 250. In turn, the string assembly 200 drags the payload 280, optionally via an additional flexible string segment connecting the payload 280 to the string assembly 200. The payload 280 can selectively explode and/or induce a very significant drag and/or instability to the external object 10, thereby causing the external object 10 to become damaged, to disintegrate, or to at least veer significantly from the projected trajectory T.

Optionally, for examples in which the payload 280 is explosive, the payload 280 can be distributed as a plurality of explosive charges at different locations in the string assembly 200, ensuring or at least increasing the likelihood that at least some of charges are in direct contact with or close to the locked external object 10, rendering the detonation of the payload more effective.

The external object 10 thereby becomes neutralized or ineffective by being damaged or destroyed, and/or by missing its intended target at the end of projected trajectory T due to the added drag/instability.

Thus, in this mode of operation the external object 10 first intercepts, impacts and becomes locked by the open looped configuration 260 of a particular open cell 250, and thereafter causes a cascade effect in which successive concentric "rings" of open looped configurations 260, around the impacted/locked cell 250, unravel in succession as the stress fronts travel (from the point of impact of the eternal object on open cell 250A) outwardly along the string assembly 200.

In greater detail, and referring to Fig. 8(c), it can be clearly seen that in this example the string assembly 200 comprises a generally centrally disposed open looped configuration 260 (further designated with the reference numeral 260A) corresponding to cell 250A, surrounded or circumscribed by and connected to a first ring Rl of looped configurations 260 (further designated with the reference numeral 260B corresponding to open cells 250B) adjacent to open looped configuration 260A. Similarly, the first ring Rl is surrounded or circumscribed by and connected to a second ring R2 of open looped configurations 260 (further designated with the reference numeral 260C corresponding to open cells 250C) adjacent to open looped configurations 260B, and the second ring R2 is surrounded or circumscribed by and connected to a third ring R3 of open looped configurations 260 (further designated with the reference numeral 260D and corresponding to open cells 250D) adjacent to open looped configuration 260C. In the example of Fig. 8(c), open cell 250A is designated as the open cell 250 that is impacted by the external object 10, e.g. a projectile. Nevertheless, a similar effect occurs in the string assembly 200 when any of the other open cells 250 in string assembly 200 is impacted by an external object. The stress fronts traveling outwards 5 from the points of impact will cause successive open cells (surrounding the impacted open cell) to unravel, until the entire assembly is unraveled. The unraveling reduces the load of the adjacent open cells on the impacted cell, introduces a delay for the arrival of reflected stress front from the ends of the assembly and thereby improves the impact resilience of the string assembly 200.

10 Each open cell 250 in the array of the string assembly 200 has a corresponding set (and pattern) of successive full (or partial) rings of other open cells 250 radiating therefrom to the outer edge 299 of the string structure 200, and the details of such corresponding set (and pattern) of successive full (or partial) rings of other open cells 250 will of course depend the location of the particular open cell 250 within the string

15 assembly 200.

Thus, and referring in particular to Figs. 10(a) and 10(b), after the object 10 becomes locked with open looped configuration 260A of open cell 250A, the respective retainer arrangements 220 of at least some, and typically each one, of the open looped configurations 260B in ring Rl are configured to become non-operational, for example

20 by mechanically failing, etc. Without being bound to theory, such mechanical failure is considered to be responsive to the loads induced in the parts of the respective primary string segments 210 that form the open looped configurations 260B, these loads having been generated due to the impact and locking of the object 10 with open looped configuration 260A. In this mode of operation the respective retainer arrangements 220

25 are thus configured for becoming non-operational, for example mechanically failing or disassembling, under such loads, after which the respective open looped configurations 260B progressively unravel, while corresponding parts of the respective primary string segments 210 are still connected to the open looped configuration 260A. At the same time, the unraveling open looped configurations 260B (marked in the Fig. 10(b) as

30 260B') are also still connected to the open looped configurations 260C of ring R2, but the unraveling of the open looped configurations 260B provides a delay in, and in a reduction of the magnitude of, the load that is in turn applied to open looped configurations 260C via the corresponding primary string segments 210 due to the original impact/locking of the object by the open looped configurations 260A. Without being bound to theory, such an effect can be understood to originate from the fact that the respective lengths of primary string segments that were previously looped to form the respective are now unlooped and proceed to extend out in the general direction of motion of the object 10, and in the meantime the remaining rings R2, R3 have not yet been dragged due to the motion of the object 10.

Unless this reduction in loading now applied to the open looped configurations 260C at ring R2 is such that the respective retainer arrangements 220 of these open looped configurations 260C are still operational, then the unraveling effect will cascade to ring R2. In such a case, and referring to Figs. 11(a) and 11(b), the retainer arrangements 220 of the open looped configurations 260C of ring R2 will also become non-operational, similarly causing unraveling of open looped configurations 260C (marked in the Fig. 10(b) as 260C), thereby providing a further delay in, and a further reduction of the magnitude of, the load that is in turn applied to open looped configurations 260C of ring R3 due to the original impact/locking of the object by the open looped configurations 260A.

Similarly, unless this additional reduction in loading at ring R3 is such that the respective retainer arrangements 220 of the open looped configurations 260D are still operational, then the unraveling will also cascade to ring R3. In such a case (not shown), the retainer arrangements 220 of the open looped configurations 260D of ring R3 will also become non-operational, similarly causing unraveling of open looped configurations 260D, thereby providing a further delay in, and a further reduction of the magnitude of, the load that is in turn ultimately applied to the payload 280 due to the original impact/locking of the object by the open looped configurations 260A.

In alternative variations of this example in which the string assembly 200 has a very large array of open cells 250 (for example hundreds or thousands of open cells, or more), and that for at least some such open cells have a large number of successive, generally concentric rings of open cells, the unraveling cascade can stop one or more rings away from the periphery 299 of the string assembly 200, in which the respective retainer arrangements 220 are still operational and conserve the open looped configurations. For example such a large string assembly 200 can be used for intercepting a plurality of spaced external objects (for example a barrage of projectiles) or the like, concurrently or in close succession.

In any case, after the last full or partial ring of respective open looped configurations 260 unravels, the string assembly 200 is dragged by the external object 10, and at some point in the trajectory the payload 280 can be activated, rendering object 10 ineffective by being damaged or destroyed, and/or by missing its intended target at the end of projected trajectory T due to the added drag/instability, for example.

In at least some variations of this example, irrespective of the number of primary string segments used, the string assembly is designed such that the payloads 280, remain attached to all such primary string segments once they are completely unraveled.

As will become clearer hereinbelow, the open nodal zones 290 are eliminated in other examples of the presently disclosed subject matter, essentially by reshaping the basic round shape of the open cell of the second example into other planar shapes, such as for example, rectangular shapes. Furthermore, such non-circular open cell shapes are maintained with the aid of retaining arrangements that are designed to break at sufficient loading, and once these retaining arrangements break, the open cell that is previously impacted by the external object is free to take the form of the cross-section of the impacting object, while surrounding cells that have not been impacted are allowed to unravel.

Referring to Fig. 12, a string assembly 300 according to a third example of the presently disclosed subject matter includes at least some of the elements and features as disclosed herein for the first example of the string assembly 100 and for the second example of the string assembly 200, including alternative variations thereof as disclosed herein, mutatis mutandis, but with some differences, as will become clearer in the following disclosure.

String assembly 300 thus also comprises an array of open cells 350, each cell being similar to open cell 150 of the first example (or alternative variations thereof) or open cell 250 of the second example (or alternative variations thereof), mutatis mutandis. Furthermore, string assembly 300 comprises a plurality of primary string segments 310, each being similar to the primary string segment 110 as disclosed herein for the first example (or alternative variations thereof) or to the primary string segment 210 as disclosed herein for the second example (or alternative variations thereof) of the presently disclosed subject matter, mutatis mutandis. Thus, each primary string segment 310 comprises a corresponding open cell 350, defined by a respective open looped configuration 360, each open looped configuration 360 being substantially similar in structure and function to the open looped configurations 160 and 260 as disclosed herein for the first example and the second example (and alternative variations thereof), mutatis mutandis. Thus, and referring in particular to Figs. 13(a) and 13(b), in the third example each open looped configuration 360 is in the form resembling a clove hitch knot, and the corresponding portion of the string segment 310 thus comprises two consecutive and contiguous loops 310a, 310b, overlaid on one another, the portion of string segment 310 extending to respective ends 311a, 311b along generally opposite directions, with one overlying section 312 of the portion of the string segment 310 being overlaid over corresponding sections 313, 314 of the loops 310a, 310b to form an overcross, similar to the corresponding components as disclosed above for the first and second examples, mutatis mutandis, including: for example consecutive loops 110a, 110b; ends 111a, 111b; overlying section 112; sections 113, 114; or similar to: consecutive loops 210a, 210b; ends 211a, 211b; overlying section 212; sections 213, 214. Also as for the first and second examples, mutatis mutandis, in alternative variations of the third example each of the open looped configuration 360 can instead be in a form similar to or resembling, for example, any one of: girth hitch knot, rolling hitch knot, constrictor knot, or equivalents thereof, or similar knot arrangements that are self-locking onto an external object that is inserted into them.

Furthermore, for each row of the array, the respective plurality of open looped configurations 360, and thus the corresponding open cells 350, are serially joined to one another, and the corresponding loops 310a, 310b can optionally be intertwined with one another serially and/or in parallel with the open cells of adjacent rows of the array, for example at "E" and "F" respectively, similar to as disclosed above for the second example at "A" and "B", mutatis mutandis.

In this example, the adjoining ends of adjacent open looped configuration 360 of each row of the array are integrally joined and the same continuous string element integrally includes the corresponding plurality of respective primary string segments 310. In other words, the string assembly 300 is constructed from a number of string sub- assemblies (corresponding to the number of rows of the array), each string subassembly integrally comprising a plurality of primary string segments 310 and being used to successively form all the open looped configurations 360 thereof of the respective row. Optionally, each of the separate string segments 310 can extend to reach and connect to the payload.

However, while in this example each of the rows of the array of the string assembly 300 is constructed with a single, continuous, string element, in alternative variations of this example each of the rows of the array of the string assembly 300 is made from a plurality of separate primary string segments or equivalents thereof,, joined serially to one another, each such primary string segments including a respective open looped configurations 360.

In yet other variations of this example, the full array of the string assembly 300 is constructed with a single, continuous, string element, or equivalents thereof, which is used to successively form all the open looped configurations 360 thereof, for example forming each row of the array in succession, and thus such a continuous, string element integrally comprises all the primary string segments of the array.

In any case, one difference between the string assembly 300 of the third example compared and the string assembly 200 of the second example is that the string assembly 300 at array nodes 390 eliminates, or at least minimizes the size of, the open nodal zones 290 of the string assembly 200. In so doing, the statistical probability of an object 10 impacting the open cells 350 of the string assembly 300 rather than the array nodes 390 thereof is higher than for the string assembly 200. Accordingly, string assembly 300 comprises a rectangular array of open cells 350, in which the relatively round plan form of the corresponding open cells 250 of string assembly 200 are essentially "squared off to the generally rectangular plan form of open cells 350, as illustrated in Fig. 13(a) at "Q". The adjacent corners of each set of four adjacent open looped configurations 360 of string assembly 300, marked "C", are thus located at the corresponding array node 390 of the array of open looped configurations 360. As can be understood from Fig. 13(a), each cell 350 is rectangular, having a length dimension L2 greater than a width dimension Li. However, in alternative variations of this example, the rectangular cells 350 can be square, i.e., with the respective length dimension L2 being equal to the respective width dimension Li. In any case, and as for the first and second examples disclosed above, mutatis mutandis, the dimensions of the cell 350 can be chosen so that the perimeter 355 of the cell (= 2xLl + 2 xLi) after it experiences the full elongation anticipated elongation by stretching over the impacted external object, is thus intermediate in value with respect to the aforesaid minimum perimeter and maximum 5 perimeter of these corresponding cross-sections of the object 10.

Furthermore, the corresponding retainer arrangement 320 for the open looped configurations 360 of the string assembly 300 are located at the array nodes 390, and retainer arrangement 320 can be configured to concurrently retain the form of the four of the open looped configurations 360 that meet at the respective array node 390 (or of

10 the two open looped configurations 360 that meet at the respective array node 390 where the array node 390 is at the periphery of the string assembly 300). In this example, the retainer arrangement 320 comprises at each array node 390 a pair of secondary string segments 322, distinct, i.e. different from or separate from, the primary string segments 310. Each string segment 322 is tied to two different diagonally

15 adjacent open looped configurations 360, each respective secondary string segment 322 being looped around the corresponding parts of the loops 310a, loop 310b of each of the respective pair of open looped configurations 360. Furthermore, and as can be seen from Fig. 13(a) at "C", the two looped secondary string segments 322 at the respective array node 390 cross one another when observed in plan view.

20 In this manner, retainer arrangement 320, in this example in the form of the secondary string segments 322, has a dual function: to prevent the primary string segments 310 that form the four open looped configurations 360 from unraveling; and to retain the rectangular form of the open cells 350. In alternative variations of this example, the retainer arrangement 320 can comprise one such secondary string segment

25 322 that holds together the "corners" of two diagonally adjacent open cells 350, and then extend in a contiguous manner to hold together the "corners" of the other two diagonally adjacent open cells. Alternatively, more than two such secondary string segments 322 can be used. In this example, each secondary string segment 322 is affixed to itself in its looped configuration, in which it is engaged to the primary string

30 segments 310 at corresponding parts of the open looped configuration 360 in any suitable manner - for example the respective string segment 322 can be tied to itself, or can be welded, mechanically affixed, or be formed as an integral loop (such as for example a ring).

In alternative variations of this example, the retainer arrangement 320 can comprise cement or resin or equivalents thereof securing the primary string. Alternatively pressed strips of metal can be used to hold the primary string in place. Alternatively plastic retainers can be clamped onto, or molded onto or heat shrunk onto the primary strings.

It is evident that the retainer arrangement 320, when thus engaged to the open looped configuration 360, is operational to maintain the spatial relationship that defines the open looped configurations 360 (even though there is, as yet, an absence of any external body in abutting relationship with the periphery 355 of the respective cell 350), in particular the spatial relationship between the loops 310a, 310b and overlying section 312 thereof.

The string assembly 300 can operate in the same manner as the disclosed above for the string assembly 200 according to the second example of the presently disclosed subject matter, mutatis mutandis, with the following main difference. Prior to impact of the object 10 with the string assembly 300, the trajectory T of the object intersects one cell 350, and as the object 10 enters the cell 350 it probably makes contact first with the longer sides of the periphery 355, particularly if the object has a cross-section that is circular or near-circular. As the external object 10 continues penetrating the cell 350, the open cell 350 is forced to deform and assume the shape of the cross-section of the object that is now abutting the full periphery 355. In so doing, the open cell 350, and thus the respective open looped configuration 360, locks onto the object 10, in a similar manner to that disclosed above for the first and second examples, mutatis mutandis. At the same time, the retainer arrangements 320 at the four corners of the respective open looped configuration 360 become non-operational, for example mechanically fail or otherwise break or otherwise disassemble. As the impacted open cell 350 is accelerated after impact by the external object 10, this open cell 350 exerts tensile forces on the surrounding open cells 350, which causes in turn their retainer arrangements to break or become disassembled, and their respective open looped configurations are, in turn unraveled. Eventually, the now-unraveled string assembly 300 is dragged by the external object 10, and at some point in the trajectory the payload 380 can be activated, selectively neutralizing or otherwise rendering object 10 ineffective by being damaged or destroyed, and/or by missing its intended target at the end of projected trajectory T 5 due to the added drag/instability, for example.

An alternative variation of the third example of the string assembly 300 is illustrated in Fig. 14, wherein the particular retainer arrangement 320 comprises a plurality of continuous secondary string segments 322', distinct, i.e. different from or separate from, the primary string segments 310. Each continuous string segment 322 10 follows a "row" of the rectangular array of the string assembly 300, and is thus coextensive with successive longer sides of the periphery 355 of respective cells 350 at the respective "row" of the array, while being tied around the array nodes 390 between the aforesaid longer sides of each successive pair of open cells 350.

However, when the external object 10 first impacts the longer sides of a 15 particular cell 350 it also impacts the part of the respective continuous secondary string segments 322' thereby loading the same. However, since the retaining continuous secondary string segments 322' are mechanically weaker than the primary string segments 310, the continuous secondary string segments 322' become non-operational (for example mechanically fail, for example break, or become disassembled), under the 20 load, which thus precipitates unraveling throughout the remaining open cells. As a result the open cells adjacent to the impacted open cell unravel more quickly reducing the initial load of the impacted open cell.

Another alternative variation of the third example of the string assembly 300 is illustrated in Fig. 15, and while similar to the alternative example of Fig. 14, the

25 particular retainer arrangement 320 now comprises a plurality of pairs of continuous secondary string segments 322', each string segment 322' thereof being distinct, i.e. different from or separate from, the primary string segments 310. Each pair of continuous string segments 322' follows a "row" of the rectangular array of the string assembly 300, and are thus co-extensive with successive longer sides of the periphery

30 355 of respective cells 350 at the respective "row" of the array, while being tied around the array nodes 390 between the aforesaid longer sides of each successive pair of open cells 350. However, the continuous secondary string segments 322' of each pair face the open cells 350 of adjacent open cells 350 along a "column" of the array assembly of the string assembly 300. Furthermore, the continuous secondary string segments 322' of each pair cross over one another at the array nodes 390. Operation of this variation of string assembly 300 is similar to that illustrated in Fig. 12, mutatis mutandis.

Similar to the case of the cells of the second example of string assembly 200, mutatis mutandis, in the third example and alternative variations thereof illustrated in Figs. 12 to 15, the respective primary string segments forming adjacent open cells can be intertwined (similar to the form shown in Fig 7(a), mutatis mutandis). Alternatively the open cells can be formed in a non-intertwined manner, i.e. separate from one another, and the respective string assembly is held together only with the retaining arrangements.

In yet a further alternative variation of the third example, each respective primary string segment is formed from a plurality of strands, and this feature can provide increased flexibility of the overall string assembly. Additionally or alternatively, such a multiple-stranded primary string can be formed from different materials so as to address different predicted situations. For example, the plurality of strands can comprise strands made from a relatively higher tensile material for high resilience at high impacts, combined with strands made from a relatively more flexible material for providing larger elongation. Such a combination of strands allows for different behaviors for the respective open cell, when impacted by an external object 10, enabling the impacted open cell to withstand high impact and high levels of tensile stresses, compared with the surrounding unraveling open cells which provide a cushioning and dampening effect with a highly flexible material. The open cells surrounding the impacted open cell are subject to high tensile loads, and should the high tensile strands break as a result, the high flexibility strands will remain intact and maintain the entire string assembly functional.

Thus, in an alternative variation of the third example, illustrated in Fig. 16, includes a double-open loop cell configuration for the respective string assembly 300A, where an inner open looped configuration 360a (defining an inner open cell 350a) is provided concentrically within an outer open looped configuration 360b (defining an outer open cell 350b). The inner open looped configuration 360a (and thus inner open cell 350a) has a relatively smaller peripheral length than the peripheral length of the outer open looped configuration 360b (and thus of outer open cell 350b). In this example, the inner open cell 350a engages the impact of an external object 10 first. Should inner open cell 350a fail due to the high impact, however, the second, outer open cell 350b remains, and as the inner open cell 350a has already engaged the 5 external object and caused a certain acceleration of the string assembly, the outer open cell 350b experiences a relative smaller impact velocity and can therefore survive the impact. Of course any number of concentric open cells can be provided, nested in one another with cascaded sizes can be provided to improve the resistance of the overall assembly to the impact. Otherwise, the string assembly 300A comprises a retainer 10 arrangement 320A and payload as described for the third example, mutatis mutandis, and operates in a similar manner thereto, mutatis mutandis.

Another alternative variation of the third example of the string assembly 300 is illustrated in Fig. 17, in which the respective retainer arrangement 320B is similar to that of the example illustrated in Figs. 14 and 15, mutatis mutandis. However, in the

15 example of Fig. 17, each retainer arrangement 320B is further partially looped around part of the respective peripheries 355 of the open cells 350. Together, adjacent retainer arrangements 320B form retainer arrangement loops 320C around the periphery 355 of each respective open cell 350, each retainer arrangement loop 320C having a smaller periphery than the respective periphery 355. This configuration ensures that the

20 impinging object 10 in any particular cell 350 will first break the retainer arrangement loop 320C, and thereafter the string assembly will operate in a similar manner to that disclosed above with reference to the examples illustrated in Figs. 14 and 15. Alternatively, the respective retainer arrangement 320 is configured to have smaller elongation (or smaller breaking strain) before breaking than the primary string segments

25 310, and thus become non operational by mechanically breaking before the primary string segments 310 when subject to the same strain. In such a case, the retainer arrangement loops can have respective peripheries that are similar in size to respective peripheries 355 of the cells 350 (for example similar to the examples illustrated in Figs. 14 and 15, mutatis mutandis), but the retainer arrangement 320B will nevertheless be

30 first to become non-operational, for example by mechanically failing, when subject to the same stress as the primary string segment 310. In the method claims that follow, alphanumeric characters and Roman numerals used to designate claim steps are provided for convenience only and do not imply any particular order of performing the steps.

Finally, it should be noted that the word "comprising" as used throughout the appended claims is to be interpreted to mean "including but not limited to".

While there has been shown and disclosed examples in accordance with the presently disclosed subject matter, it will be appreciated that many changes may be made therein without departing from the spirit of the presently disclosed subject matter.

Claims

CLAIMS:

1. String assembly defining at least one open cell, comprising;

and wherein

2. String assembly according to claim 1, comprising a plurality of said open cells and a corresponding plurality of said primary string segments, each said open cell comprising a respective said primary string segment in a respective said open looped configuration, wherein said retainer arrangement is configured for retaining each said primary string segment in the respective said open looped configuration, independently from one another.

3. String assembly according to claim 1 or claim 2, wherein in said open looped configuration each respective said primary string segment is configured to lock onto the external object at least partially via factional contact between overlapping parts of the respective said primary string segment.

4. String assembly according to any one of claims 1 to 3, wherein in said open looped configuration the respective said primary string segment is configured to lock onto the external object at least partially via frictional contact between a portion of the respective said primary string segment and the external object.

5. String assembly according to any one of claims 1 to 4, wherein said looped configuration has a form of a clove hitch knot or a form resembling a clove hitch knot.

6. String assembly according to any one of claims 1 to 5, wherein at least one said looped configuration comprises any one of: a girth hitch knot, a rolling hitch knot, a

5 constrictor knot, or any knot arrangement that is self-locking onto said external object that is inserted thereinto.

7. String assembly according to any one of claims 1 to 6, wherein said retainer arrangement comprises at least one mechanical retainer configured to become non- operational when a respective primary string segment is subjected to a load exceeding a

10 predetermined load threshold, said load being induced in the respective primary string segment in response to the external object being selectively introduced into said open cell and into abutting contact with said periphery.

8. String assembly according to any one of claims 1 to 7, wherein said retainer arrangement comprises at least one secondary string segment engaged to a respective

15 said primary string segment.

9. String assembly according to any one of claims 1 to 7, wherein said retainer arrangement comprises any one of: a cement or resin material engaged to a respective said primary string segment; or a plastic element or a metal element clamped onto, molded onto or heat shrunk onto respective said primary string segment.

20 10. String assembly according to any one of claims 1 to 9, wherein at least one said primary string segment is provided excluding strength-reducing knots formed therein such strength-reducing knots being self-locking and including bends of small-radius as compared with a thickness of the primary string segment.

11. String assembly according to any one of claims 1 to 9, wherein each said open 25 looped configuration excludes strength-reducing knots formed by the respective primary string segment.

12. String assembly according to any one of claims 1 to 11 , wherein at least one said primary string segment in said open looped configuration is intertwined with respect to an adjacent said primary string segment in said open looped configuration.

30 13. String assembly according to any one of claims 1 to 12, comprising a string subassembly including a plurality of said primary string segments serially joined end-to- end forming a corresponding plurality of said looped configurations in adjacent serial relationship.

14. String assembly according to claim 13, comprising at least two said string substructures in juxtaposed relationship and/or comprising at least two said string substructures intertwined with respect to one another.

15. String assembly according to any one of claims 2 to 14, wherein a continuous 5 string element integrally comprises said plurality of said primary string segments in serial relationship.

16. String assembly according to any one of claims 1 to 15, wherein said at least one primary string segment has a mechanical strength greater than a mechanical strength of the retainer arrangement.

10 17. String assembly according to any one of claims 1 to 16, wherein said at least one primary string segment is configured for withstanding an impact from a body traveling at high velocity transverse to a longitudinal axis of the primary string segment.

18. String assembly according to claim 16, wherein said high velocity is a velocity greater than 400m/s.

15 19. String assembly according to any one of claims 2 to 18, wherein said open cells are arranged in a general two-dimensional array and wherein said retainer arrangement is configured for retaining said plurality of primary string segments, each in corresponding said looped configuration, at nodes of said array.

20. String assembly according to claim 20, wherein said plurality of primary string 20 segments forming at least one row of said open cells and/or forming at least one column of said open cells of said array is formed from a single continuous length of string.

21. String assembly according to claim 19 or claim 20, wherein said cells of said array are generally polygonal.

22. String assembly according to claim 19 or claim 20, wherein said cells of said 25 array are generally rectangular.

23. String assembly according to claim 22, wherein said retainer arrangement comprises a secondary string segment co-extensive with a corresponding side of a plurality of said generally rectangular cells.

24. String assembly according to claim 22, wherein said retainer arrangement 30 comprises a pair of secondary string segments, each co-extensive with a corresponding side of a plurality of said generally rectangular cells.

25. String assembly according to any one of claims 2 to 24, configured for unraveling at least one said open looped configuration located adjacent to an impact cell while remaining mechanically connected hereto on impact of the external object with said impact cell.

26. String assembly according to any one of claims 2 to 25, wherein some of said open looped configurations, located in a ring around and adjacent to an impact cell, are configured for unraveling while remaining mechanically connected thereto responsive to impact of the external object with the impact cell, said impact cell being chosen from said plurality of open cells.

27. String assembly according to any one of claims 2 to 26, wherein some of said open looped configurations, located in each a two or more concentric rings around an impact cell, are configured for unraveling while remaining mechanically connected thereto responsive to impact of the external object with the impact cell, said impact cell being chosen from said plurality of open cells.

28. String assembly according to any one of claims 25 to 27, wherein said respective open looped configurations are configured for unraveling via mechanical failure or disassembly of the respective said retainer arrangements, wherein said mechanical failure of the respective said retainer arrangements being responsive to loading of the failed retainer arrangements beyond a failure loading limit due to said abutting contact between the external object and the respective said periphery of the impact cell.

29. String assembly according to any one of claims 1 to 28, wherein said external object is a moving object.

30. String assembly according to any one of claims 1 to 29, wherein said external object is a moving projectile or an airborne aircraft.

31. String assembly according to any one of claims 1 to 30, wherein said at least one primary segment is made from any one of Kevlar, Dyneema, Carbon fiber artificial spider web.

32. String assembly according to any one of claims 1 to 31, wherein each said primary string segment comprises a plurality of strand elements.

33. String assembly according to any one of claims 2 to 31, wherein each said primary string segment comprises at least a first strand element and a second strand element, and wherein said first strand element is configured for providing better performance than said second strand element with respect to said locking, and wherein said second strand element is configured for providing better performance than said first strand element with respect to said unraveling.

34. String assembly according to any one of claims 1 to 33, wherein at least one said open cell comprises at least two said open looped configurations in concentric relationship with one another and having respective said peripheries of different lengths one from another.

5 35. String assembly according to claim 34, wherein each said open looped configuration in said concentric relationship is configured for locking with the external object in succession with one another.

36. A net comprising a string assembly as defined in any one of claims 1 to 35.

37. A net according to claim 36, further comprising a pay load.

10 38. A net according to claim 37, wherein said payload is one of:

15 - comprises a plurality of payload items distributed over the net.

39. A net according to claim 37 or claim 38, wherein said payload is an explosive device.

40. A net according to claim 39, wherein said payload is configured for detonating according to predetermined criteria after the external object establishes said abutting

20 contact with said net.

41. A net according to claim 37 or claim 38, wherein said payload is configured for selectively inducing a drag force to said net.

42. A net according to claim 41, wherein said payload comprises at least one parachute.

25 43. A net according to claim 41 or claim 42, wherein said payload is configured for deploying according to predetermined criteria after the external object establishes said abutting contact with said net.

44. A net according to any one of claims 40 and 43, wherein said predetermined criteria include an elapsed time after the external object establishes said abutting contact

30 with said net.

45. A method comprising:

• providing a net as defined in any one of claims 36 to 44; • deploying said net at a location intersecting a projected path of the external object;

• allowing the external object to become introduced into any one said open cell and into abutting contact with a respective said periphery thereof to thereby lock said cell onto the external object.

46. A method comprising:

47. Method according to claim 46 further comprising the step of allowing unraveling of at least one said open looped elements located in at least one concentric ring around the at least one said open looped element.

48. A net assembly comprising a plurality of open cells, the net assembly comprising a plurality of primary string segments, each primary string segment being looped in an open looped configuration to define a respective said open cell, wherein said open looped configurations have an absence of a strength-reducing knot formed by the respective primary string segment, the net assembly further comprising a mechanical retainer arrangement configured for retaining said primary string segments in said looped configuration while the respective said primary string segments are subjected to loads below a predetermined threshold, each said cell being configured for locking therein an external object that is brought into abutting contact with a periphery of the respective cell to thereby load the respective said primary string segment to loads exceeding said threshold while being mechanically connected to a remainder of the net assembly via at least some of said primary string segments.

49. A net assembly comprising an array of primary string segments defining a plurality of open cells and nodes, said primary string segments being in open looped configuration to define respective said open cells, wherein said primary string segment s have an absence of strength-reducing knot formed therein.

50. A net assembly comprising open looped elements formed by respective primary string segments and configured for providing a friction lock when in contact with an external body therein, said looped elements having an absence of structural ties therein.