IL277430B2 - Steering system - Google Patents

Description

0270259229- STEERING SYSTEM TECHNOLOGICAL FIELD The presently disclosed subject matter relates to steering systems and methods for projectiles .

BACKGROUND Conventionally, missiles have a steering systems for enabling steering of the missile towards a desired target. In some applications, it is required to steer the missile rapidly from a relatively vertical attitude to a more horizontal attitude. For example, some types of anti-missile missiles are conventionally launched from a ship or other fixed platform against an oncoming low flying threat. However, such threats are often difficult to detect until the threat is very close, for example about 20km, since such low flying can be under the radar and also because of the curvature of the Earth. In such cases, conventional anti-missile missiles can be launched vertically and then quickly turned into a generally horizontal trajectory at the desired horizontal direction of azimuth to thereby neutralize the threat. In cases where the azimuth direction of the on-coming threat cannot be known in advance, vertical launching provides a quick way of launching the missile rapidly, while allowing the missile to attain the deaired horizontal azimuth thereafter. Conventional micro rocket at nose of the missile can enable the missile to be directed along the desired horizontal azimuth direction, but such a solution can be slow in turning the missile, with potentially fatal consequences. An alternative solution is providing the missile in which the solid propellant engine has vanes in the exhaust that operate to steer the missile at the early stages of the trajectory. 0270259229- GENERAL DESCRIPTION According to a first aspect of the presently disclosed subject matter, there is provided a projectile comprising: a first longitudinal projectile portion having a first longitudinal axis and a first center of gravity; a second longitudinal projectile portion having a second longitudinal axis and a second center of gravity; a steering mechanism including an actuator system operatively coupled to an interface portion, the interface portion longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said interface portion configured for selectively and reversibly changing an angular relationship between the first longitudinal axis and the second longitudinal axis along a reference plane, between a datum configuration and a turning configuration, responsive to operation of the actuation system, wherein: in said datum configuration, the first longitudinal axis and the second longitudinal axis are parallel to one another, said first center of gravity is at a first minimum transverse spacing with respect to the second longitudinal axis, and said first center of gravity is at a first longitudinal spacing with respect to the second longitudinal portion in a direction parallel to said second longitudinal axis; and in said turning configuration, the first longitudinal axis and the second longitudinal axis are at a non-zero angular displacement with respect to one another along said reference plane such that said first center of gravity is at a second minimum transverse spacing with respect to the second longitudinal axis, and such that said first center of gravity is at a second longitudinal spacing with respect to the second longitudinal portion in a direction parallel to said second longitudinal axis; wherein said steering mechanism is further configured for ensuring that: 0270259229- - said second minimum transverse spacing is greater than said first minimum transverse spacing, to thereby enable a turning moment to be applied to the projectile; and - said second longitudinal spacing is not less than said first longitudinal spacing. For example, said steering mechanism is configured for providing the projectile with said turning moment, independent of external aerodynamic forces.

Additionally or alternatively, for example, the first longitudinal projectile portion comprises a plurality of first vanes.

Additionally or alternatively, for example, the second longitudinal projectile portion comprises a plurality of second vanes.

Additionally or alternatively, for example, the projectile comprises a propulsion system.

Additionally or alternatively, for example, said angular displacement is in the range of 1  to 25 .

Additionally or alternatively, for example, said angular displacement is in the range of 10  to 15 .

Additionally or alternatively, for example, said angular displacement is up to any one of: 5 , 10, 12, 15 , 20 , 25.

Additionally or alternatively, for example, said second longitudinal spacing is equal to or greater than said first longitudinal spacing.

For example, and in at least a first example, said interface portion comprises a first linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said first linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said first linkage mechanism is based geometrically on 0270259229- the so-called Peaucelier-Lipkin circle inversion mechanism. For example, said first linkage mechanism is pivotably mounted to said first longitudinal projectile portion at a respective first fixed position, and wherein said respective first fixed position is displaced away from the second longitudinal projectile portion along a direction parallel to the second longitudinal axis in said turning configuration by a respective first longitudinal displacement. For example, said first center of gravity is displaced towards said respective first fixed position along a direction parallel to the second longitudinal axis in said turning configuration by a respective second longitudinal displacement, said respective second longitudinal displacement being less than respective first longitudinal displacement.

For example, and in at least a second example, said interface portion comprises a second linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said second linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said second linkage mechanism comprises: - a first bracket fixedly mounted to the first longitudinal portion, - a second bracket fixedly mounted to the second longitudinal portion, - a link having an axial length, a first end pivotably mounted to the second longitudinal portion at a first position, and a second end pivotably mounted to the first longitudinal portion at a second position, - the first position being fixed with respect to the second longitudinal portion, - the second position being fixed with respect to the first longitudinal portion, - relative movement between the first bracket and the second bracket being constrained at a third position, different from said first position and said second position, wherein said third position is fixed with respect to the second longitudinal portion.

For example, said second linkage mechanism is pivotably mounted to said first longitudinal projectile portion at a respective second fixed position, and wherein said respective second fixed position is displaced away from the second longitudinal projectile portion along a direction parallel to the second longitudinal axis in said turning 0270259229- configuration by a respective first longitudinal displacement. For example, said first center of gravity is displaced towards said respective second fixed position along a direction parallel to the second longitudinal axis in said turning configuration by a respective second longitudinal displacement, said respective second longitudinal displacement being less than respective first longitudinal displacement.

Alternatively, for example, said second longitudinal spacing is equal to said first longitudinal spacing. For example, in third example said interface portion comprises a third linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said third linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said third linkage mechanism is based geometrically on the so-called Peaucelier-Lipkin exact straight line mechanism. For example, said third linkage mechanism is pivotably mounted to said first longitudinal projectile portion at a respective third fixed position, and wherein said first center of gravity is located at said third fixed position.

Additionally or alternatively, for example, the projectile comprises a roll system configured for selectively rolling at least the forward longitudinal part about the second longitudinal axis about any desired roll angle.

For example, the roll system comprises a reaction control system (RCS) including at least one impulse nozzles configured for selectively providing a thrust component spaced by moment arm from the second longitudinal axis ,to thereby induce a rolling moment to the projectile about the second longitudinal axis.

Additionally or alternatively, for example, the roll system comprises the interface portion rotatably mounted to the second longitudinal portion, to thereby allow the interface portion ,together with the first longitudinal portion to be rotated with respect to the second longitudinal portion about the second longitudinal axis. 0270259229- Additionally or alternatively, for example, the projectile further comprises a boost stage comprising one or a plurality of boost stages fitted at an aft end of the second longitudinal portion.

Additionally or alternatively, for example, the projectile further comprises a controller operatively coupled to the steering mechanism and configured for controlling operation of the steering mechanism to provide a desired trajectory for the projectile.

Additionally or alternatively, for example, the projectile is configured for being launched in a general vertical direction, and for operating the steering mechanism at a predetermined height to provide a desired said angular displacement to thereby turn the projectile away from a vertical trajectory.

Additionally or alternatively, for example, the projectile is configured for providing a trajectory along a desired azimuth.

According to a second aspect of the presently disclosed subject matter, there is provided a launch system comprising: - a projectile as defined herein regarding the first aspect of the presently disclosed subject matter; - a launcher configured for launching the projectile in a generally vertical direction. For example, the launcher comprises a launch tube configured for launching the projectile from a pre-launch configuration in which the projectile is accommodated in the launch tube For example, the launcher is rotatably mounted to a fixed base, to allow pivoting or rotation of the launch tube with respect to the base about a vertical axis.

According to a third aspect of the presently disclosed subject matter, there is provided a method for steering a projectile, comprising: - providing the projectile, the projectile as defined herein regarding the first aspect of the presently disclosed subject matter; - operating the steering mechanism to provide a desired said angular displacement. 0270259229- According to the first aspect of the presently disclosed subject matter, there is also steering mechanism for a projectile, the projectile comprising a first longitudinal projectile portion having a first longitudinal axis and a first center of gravity, and a second longitudinal projectile portion having a second longitudinal axis and a second center of gravity, the steering mechanism comprising: an actuator system operatively coupled to an interface portion, the interface portion configured for longitudinally interconnecting the first longitudinal projectile portion and the second longitudinal projectile portion, said interface portion configured for selectively and reversibly changing an angular relationship between the first longitudinal axis and the second longitudinal axis along a reference plane, between a datum configuration and a turning configuration, responsive to operation of the actuation system, wherein: in said datum configuration, the first longitudinal axis and the second longitudinal axis are parallel to one another, said first center of gravity is at a first minimum transverse spacing with respect to the second longitudinal axis, and said first center of gravity is at a first longitudinal spacing with respect to the second longitudinal portion in a direction parallel to said second longitudinal axis; and in said turning configuration, the first longitudinal axis and the second longitudinal axis are at a non-zero angular displacement with respect to one another along said reference plane such that said first center of gravity is at a second minimum transverse spacing with respect to the second longitudinal axis, and such that said first center of gravity is at a second longitudinal spacing with respect to the second longitudinal portion in a direction parallel to said second longitudinal axis; wherein said steering mechanism is further configured for ensuring that: - said second minimum transverse spacing is greater than said first minimum transverse spacing, to thereby enable a turning moment to be applied to the projectile; and - said second longitudinal spacing is not less than said first longitudinal spacing. For example, said steering mechanism is configured for providing the projectile with said turning moment, independent of external aerodynamic forces. 0270259229- Additionally or alternatively, for example, said angular displacement is in the range of 1  to 25 .

Additionally or alternatively, for example, said angular displacement is in the range of 10  to 15 .

Additionally or alternatively, for example, said angular displacement is up to any one of: 5 , 10, 12, 15 , 20 , 25.

Additionally or alternatively, for example, said second longitudinal spacing is greater than said first longitudinal spacing.

Alternatively, for example, wherein said second longitudinal spacing is equal to said first longitudinal spacing.

For example, in at least a first example, said interface portion comprises a first linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said first linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said first linkage mechanism is based geometrically on the so-called Peaucelier-Lipkin circle inversion mechanism.

For example, in at least a second example, said interface portion comprises a second linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said second linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said second linkage mechanism is based geometrically on the so-called Peaucelier-Lipkin exact straight line mechanism.

For example, in at least a third example, said interface portion comprises a third linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said third linkage mechanism 0270259229- configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said third linkage mechanism comprises: - a first bracket fixedly mounted to the first longitudinal portion, - a second bracket fixedly mounted to the second longitudinal portion, - a link having an axial length, a first end pivotably mounted to the second longitudinal portion at a first position, and a second end pivotably mounted to the first longitudinal portion at a second position, - the first position being fixed with respect to the second longitudinal portion, - the second position being fixed with respect to the first longitudinal portion, - relative movement between the first bracket and the second bracket being constrained at a third position, different from said first position and said second position, wherein said third position is fixed with respect to the second longitudinal portion.

Additionally or alternatively, for example, the steering mechanism comprises a roll system configured for selectively rolling at least the forward longitudinal part about the second longitudinal axis about any desired roll angle.

For example, the roll system comprises a reaction control system (RCS) including at least one impulse nozzles configured for selectively providing a thrust component spaced by moment arm from the second longitudinal axis ,to thereby induce a rolling moment to the projectile about the second longitudinal axis.

For example, the roll system comprises the interface portion rotatably mounted to the second longitudinal portion, to thereby allow the interface portion ,together with the first longitudinal portion to be rotated with respect to the second longitudinal portion about the second longitudinal axis.

Additionally or alternatively, for example, the steering mechanism further comprises a controller operatively coupled to the steering mechanism and configured for controlling operation of the steering mechanism to provide a desired trajectory for the projectile. 0270259229- A feature of at least one example of the presently disclosed subject matter is that a steering system is provided for a projectile, which can operate to steer the projectile in the absence of aerodynamically induced forces, or in the absence of engine exhaust-induced forces.

Another feature of at least one example of the presently disclosed subject matter is that a steering system is provided for a projectile, which requires a relatively small actuator loads to operate the same.

Another feature of at least one example of the presently disclosed subject matter is that a steering system is provided for a projectile, in which the center of pressure of the first longitudinal projectile portion is located at or in close proximity to the first center of gravity, which requires a relatively small actuator loads to operate the same when the projectile is operating under significant aerodynamically induced forces..

Another feature of at least one example of the presently disclosed subject matter is that a steering system is provided for a projectile wherein the steering system does no require control vanes in the exhaust of the projectile rocket engine.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1(a) is a side view of a projectile according to a first example of the presently disclosed subject matter, in which the projectile is in the respective datum configuration; Fig. 1(b) is a side view of example of Fig. 1(a), in which the projectile is in the respective turning configuration. 0270259229- Fig. 2 is a side view of an interface portion according to a first example of the presently disclosed subject matter, comprised in the example of the projectile of Figs. 1(a) and 1(b). Fig. 3(a) is a side view of example of the interface portion of Fig. 2, in which the projectile is in the respective datum configuration; Fig. 3(b) is a side view of example of Fig. 3(a), in which the projectile is in the respective turning configuration. Fig. 4 is a side view of an interface portion according to a second example of the presently disclosed subject matter, comprised in the example of the projectile of Figs. 1(a) and 1(b). Fig. 5(a) is a side view of example of the interface portion of Fig. 4, in which the projectile is in the respective datum configuration; Fig. 5(b) is a side view of example of Fig. 5(a), in which the projectile is in the respective turning configuration. Fig. 6(a) is a side view of an interface portion according to a third example of the presently disclosed subject matter, comprised in the example of the projectile of Figs. 1(a) and 1(b), in which the projectile is in the respective datum configuration; Fig. 6(b) is a side view of example of Fig. 6(a), in which the projectile is in the respective turning configuration. Fig. 7 schematically illustrates a typical trajectory for the example of Fig. 1(a). Fig. 8 is a side view of a launch system according to a first example of the presently disclosed subject matter. Fig. 9 is a side view of a roll system according to a first example of the presently disclosed subject matter, for use in the projectile of the example of Fig. 1(a). Fig. 10 is a side view of a roll system according to a second example of the presently disclosed subject matter, for use in the projectile of the example of Fig. 1(a). Fig. 11 is a side view of an augmented projectile according to according to an example of the presently disclosed subject matter, including the example of the projectile of Fig. 1(a), in which the projectile is in the respective turning configuration. 0270259229- DETAILED DESCRIPTION Referring to Figs. 1(a) and 1(b), a projectile according to a first example of the presently disclosed subject matter, generally designated 10, comprises first longitudinal projectile portion 100 , a second longitudinal projectile portion 200 and a steering mechanism 400 (interchangeably referred to herein as a steering system).

In at least this example, the first longitudinal projectile portion 100 and the second longitudinal projectile portion 200together define the main body 15 of the projectile 10 , including the nose 110 and tail 290 .

The nose 110 is comprised at the forward end of the first longitudinal projectile portion 100 , which defines the forward part of the projectile 10 including an outer skin thereof, and typically, but not necessarily, the first longitudinal projectile portion 100 includes a payload (not shown). Such a payload can include, for example, one or more of the following features: one or more warheads; surveillance equipment and/or imaging equipment; navigation system; communication system; on-board computer; and so on.

The first longitudinal projectile portion 100 comprises a first longitudinal axis LA1 and a first center of gravity CG1 . The first center of gravity CG1 corresponds to the center of mass of the mass of the first longitudinal projectile portion 100 (i.e., including the mass of any payload and/or of any features affixed directly to the first longitudinal projectile portion 100 , and optionally including part or all of the steering mechanism 400 ), but excluding the mass of the remainder of the projectile 10 , in particular excluding the mass of the second longitudinal projectile portion 200 . While in at least this example, the first center of gravity CG1 is located on the first longitudinal axis LA1 , in alternative variations of this example, and in other examples, the first center of gravity CG1 is located in close proximity to the first longitudinal axis LA1 . By "close proximity" is meant that the first center of gravity CG1 is located at a first maximum transverse displacement from the first longitudinal axis LA1 , wherein such a first maximum transverse displacement is not greater than N1% of the maximum transverse dimension of the first longitudinal projectile portion 100 (at the longitudinal location of the first center of gravity CG1 ) wherein said N1% is any one of : up to 1%; up to 2%; up to 3%; up to 4%. 0270259229- In at least this example, the nose 110 can have any suitable aerodynamic shape, for example conical, pyramidical or ogive. The nose 110 as well as the remainder of the first longitudinal projectile portion 100 can have general circular cross-sections in planes orthogonal to first longitudinal axis LA1 . In alternative variations of this example, such cross-sections can have any other suitable shape, for example elliptical, super-elliptical, polygonal, etc.

In at least this example, the first longitudinal projectile portion 100 comprises such a feature in the form of a plurality of vanes 120 , in this example in cruciform "X" or "+" configuration. The vanes 120 can be attached to the first longitudinal projectile portion 100in a deployed-fixed configuration, or can be deployable with respect to the first longitudinal projectile portion 100 , for example between a stowed configuration and a deployed configuration. In at least this example, the vanes 120 are pivotable, or have pivotable control surfaces, to enable control moments in one or more of pitch, yaw and roll to be generated when the forward speed of the projectile 10 is sufficient for the airflow over the vanes 120to generate suitable aerodynamic forces corresponding to these control moments. In addition, the vanes 120can also provide or enhance longitudinal stability to the projectile 10 . However, in alternative variations of this example, and in other examples, the first longitudinal projectile portion 100 can have less than four vanes or more than four vanes, and/or, the vanes can be deployable or fixed in a deployed-fixed configuration, and/or, the vanes 120 are pivotable (or have pivotable control surfaces) to enable aerodynamically-based control moments in one or more of pitch, yaw and roll to be generated, or alternatively the vanes 120 are not pivotable or do not include pivotable control surfaces; in yet alternative variations of this example, and in yet other examples, the first longitudinal projectile portion 100 can completely omit the vanes, for example in cases in which the projectile 10 is configured as a shell, fired from a weapons barrel, or for example as ordinance dropped from an aircraft.

The second longitudinal projectile portion 200 comprises a second longitudinal axis LA2 and a second center of gravity CG2 . The second center of gravity CG2 corresponds to the center of mass of the mass of the second longitudinal projectile portion 200 (i.e., including the mass of any propulsion system and/or of any features affixed directly to the second longitudinal projectile portion 200 , and optionally including part or all of the steering mechanism 400 ), but excluding the mass of the remainder of the 0270259229- projectile 10 , in particular excluding the mass of the first longitudinal projectile portion 100 . While in at least this example, the second center of gravity CG2 is located on the second longitudinal axis LA2 , in alternative variations of this example, and in other examples, the second center of gravity CG2 is located in close proximity to the second longitudinal axis LA2 . By "close proximity" is meant that the second center of gravity CG2 is located at a second maximum transverse displacement from the first longitudinal axis LA1 , wherein such a second maximum transverse displacement is not greater than N2% of the maximum transverse dimension of the second longitudinal projectile portion 200 (at the longitudinal location of the second center of gravity CG2 ) wherein said N2% is any one of : up to 1%; up to 2%; up to 3%; up to 4%.

The tail 290 is comprised in the second longitudinal projectile portion 200 , which defines the aft part of the projectile 10 including an outer skin thereof, and typically, but not necessarily, the second longitudinal projectile portion 200in at least in this example, includes a propulsion system 280 . In at least this example, such a propulsion system 280is a rocket propulsion system, and for example includes a solid-fuel rocket propulsion system. In alternative variations of this example, and in other examples, the propulsion system 280 can additionally or alternatively include a liquid-fuel rocket propulsion system or other type of rocket propulsion system. In yet other alternative variations of this example, and in yet other examples, the propulsion system 280can additionally or alternatively include different type of propulsion system, for example ramjet propulsion system . In yet other alternative variations of this example, and in yet other examples, the rocket propulsion system 280can be omitted, for example in cases in which the projectile 10 is configured as a shell, fired from a weapons barrel, or for example as ordinance dropped from an aircraft.

Thus, such a propulsion system 280 is aft of the steering mechanism 400 .

The propulsion system 280 provides a thrust T for propelling the projectile 10 in a generally forward direction. In at least this example, and unless otherwise stated, the thrust has a thrust vector TV parallel to, and in particular co-axial with, the second longitudinal axis LA2 . In alternative variations of this example, and in other examples, in which the respective projectile omits the rocket propulsion system, and forward speed is instead applied to the projectile by launching the projectile from a weapons barrel or 0270259229- by dropping the projectile from a high altitude, the corresponding acceleration of the projectile has a similar thrust vector, also parallel to, and in particular co-axial with, the second longitudinal axis LA2 .

In at least this example, the rocket propulsion system 280includes one or more rocket engines 285 and solid fuel propellant (not shown) accommodated in the second longitudinal projectile portion 200 .

In at least this example, the tail 290 has a blunt-end 295 accommodating the one or more rocket engines 285 . The tail 290 as well as the remainder of the second longitudinal projectile portion 200 can have general circular cross-sections in planes orthogonal to second longitudinal axis LA2 . In alternative variations of this example, such cross-sections can have any other suitable shape, for example elliptical, super-elliptical, polygonal, etc.

In at least this example, the second longitudinal projectile portion 200 , for example the tail 290 , comprises such a feature in the form of a plurality of vanes 220 , in this example in cruciform "X" or "+" configuration. The vanes 220 can be attached to the second longitudinal projectile portion 200 in a deployed configuration, or can be deployable with respect to the second longitudinal projectile portion 200 , for example between a stowed configuration and a deployed configuration. In at least this example, the vanes 220 are pivotable, or have pivotable control surfaces, to enable control moments in one or more of pitch, yaw and roll to be generated when the forward speed of the projectile 10 is sufficient for the airflow over the vanes 220 to generate suitable aerodynamic forces corresponding to these control moments. In addition, the vanes 220can also provide or enhance longitudinal stability to the projectile 10 . However, in alternative variations of this example, and in other examples, the tail 290can have less than four vanes or more than four vanes, and/or, the vanes can be deployable or fixed in a deployed configuration, and/or, the vanes 220 are pivotable (or have pivotable control surfaces) to enable aerodynamically-based control moments in one or more of pitch, yaw and roll to be generated, or alternatively the vanes 220 are not pivotable or do not include pivotable control surfaces; in yet alternative variations of this example, and in yet other examples, the tail 290can completely omit the vanes, for example in cases in which the 0270259229- projectile 10 is configured as a shell, fired from a weapons barrel, or for example as ordinance dropped from an aircraft.

For convenience, and referring again to Figs. 1(a) and 1(b), a projectile-based orthogonal axes system OAS can be defined, including three mutually orthogonal axes: a roll axis R , a pitch axis P and a yaw axis Y. The roll axis R is parallel with, and in this example co-axial with, at least the second longitudinal axis LA2 , while the pitch axis P is a lateral axis orthogonal to roll axis R , and the yaw axis Y is a transverse axis orthogonal to each one of the pitch axis P and the roll axis R .

The steering mechanism 400includes an actuator system 430operatively coupled to an interface portion 500 , the interface portion 500 longitudinally interconnecting the first longitudinal projectile portion 100and said second longitudinal projectile portion 200 . Thus, the steering mechanism 400 , in particular the interface portion 500 , is located longitudinally in-between the first longitudinal projectile portion 100 and the second longitudinal projectile portion 200 .

The interface portion 500, in operation of the steering mechanism 400 is configured for selectively and reversibly changing the spatial relationship, in particular the angular relationship, between the first longitudinal axis LA1 and the second longitudinal axis LA2in at least one plane, between a datum configuration DC and a turning configuration TC , responsive to operation of the actuation system 430 .

In particular, and according to an aspect of the presently disclosed subject matter, the transition (typically an angular movement) from the datum configuration DC and up to the desired turning configuration TC , two technical effects, herein referred to as feature (A) and feature (B), are provided by the steering mechanism 400 , in particular by the interface portion 500: (A) The first center of gravity CG1 is outwardly laterally and/or transversely displaced with respect to the second longitudinal axis LA2 ; (B) The first center of gravity CG1 is prevented from decreasing its longitudinal spacing (in a direction along the second longitudinal axis LA2 ) with respect to the second longitudinal portion 200 . 0270259229- For example, and referring again to Figs. 1(a) and 1(b), interface portion 500is configured for selectively and reversibly changing the spatial relationship, in particular the angular relationship, between the first longitudinal axis LA1 and the second longitudinal axis LA2in only one plane PL , between a respective datum configuration DC and a respective turning configuration TC , responsive to operation of the actuation system 430 .

Such a plane PL is referred to interchangeably herein as the turning plane or as the reference plane, and is associated with the interface portion 500 , and thus with the steering mechanism 400 .

While such a turning plane PL is illustrated in Fig. 1(b) as the yaw-roll Y-R plane, the plane PL can instead be the pitch-roll P-R plane, or any other plane intermediate the yaw-roll Y-R plane and the pitch-roll P-R plane. In the turning configuration TC the first longitudinal axis LA1is at angle  to the second longitudinal axis LA2 along plane PL .

It is to be noted that the steering mechanism 400 , in particular the interface portion 500 , can provide the projectile 10 with a plurality of different turning configurations TC , up to a maximum turning configuration TCmax , each turning configuration TC providing a corresponding different angle  between the first longitudinal axis LA1and the second longitudinal axis LA2 along turning plane PL , up to a maximum angular displacement, at angle max.

For example, maximum angle max can be for example in the range of 1  to 25 , or in the range of 10 to 15 , for example up to any one of: 5 , 10, 12, 15 , 20, 25.

Thus, and as will become clearer herein, in at least these examples, the projectile 10 is configured for selectively and reversibly changing the spatial relationship, in particular the angular relationship, between the first longitudinal axis LA1and the second longitudinal axis LA2effectively in each of two orthogonal planes, between a datum configuration DC and a turning configuration TC , responsive to operation of the actuation system 430 . While such a pair of orthogonal planes in the examples herein include the yaw-roll Y-R plane, and the pitch-roll P-R plane, they can instead include any other set of orthogonal planes that intersect the roll plane R, for example. In any case, the 0270259229- ability to change the angular relationship between the first longitudinal axis LA1and the second longitudinal axis LA2in each of two orthogonal planes, essentially enables the first longitudinal axis LA1to be set at angle  to the second longitudinal axis LA2 along any desired corresponding turning plane DTP in the respective turning configuration TC . In particular, in the above examples such a desired corresponding turning plane DTP can be achieved by changing the angular relationship, between the first longitudinal axis LA1and the second longitudinal axis LA2along the respective turning plane PL defined by the steering mechanism 400 (for example between the datum configuration DC and the turning configuration TC , or between two different turning configurations TC ), and by also rolling at least the forward longitudinal part 100 of the projectile 10about the second longitudinal axis LA2 , until the respective turning plane PL is aligned with the desired corresponding turning plane DTP , as will become clearer below. For this purpose, the steering mechanism 400 further comprises a roll system 470 configured for selectively rolling at least the forward longitudinal part 100 of the projectile 10about the second longitudinal axis LA2 about any desired roll angle.

Feature (A) is configured for providing the projectile 10 with a turning moment, that is not dependent (i.e., that does not have to rely) on external aerodynamic forces, i.e., on aerodynamic forces that may or may not be concurrently acting on the projectile. Feature (A) thus allows the steering mechanism 400 to be used immediately after launch of the projectile 10 , and at the beginning of atmospheric flight for the projectile 10 (when aerodynamic forces are still small or not significant), as well as in an airless environment, for example in space.

According to feature (A), and referring in particular to Fig. 1(a), in the datum configuration DC , the first longitudinal axis LA1 and the second longitudinal axis LA2 are parallel to one another; in at least this example, in the datum configuration, the first longitudinal axis LA1 and the second longitudinal axis LA2 are co-axial with respect to one another. In the datum configuration DC , said first center of gravity CG1 is at a first lateral/transverse spacing SP1 with respect to the second longitudinal axis LA2 . Thus, the first lateral/transverse spacing SP1 is essentially the spacing of the first center of gravity CG1 with respect to the second longitudinal axis LA2 as taken in a lateral and/or transverse direction from the second longitudinal axis LA2 , in the datum configuration DC . 0270259229- It is to be noted that such a lateral and/or transverse direction is essentially orthogonal with respect to the second longitudinal axis LA2 .

Since in at least this example the first longitudinal axis LA1 and the second longitudinal axis LA2 are co-axial with respect to one another, and since in at least this example the first center of gravity CG1 is located on the first longitudinal axis LA1 , the first minimum spacing SP1is thus zero.

Referring in particular to Fig. 1(b), in the turning configuration TC , in at least this example the first longitudinal axis LA1 and the second longitudinal axis LA2 are non-parallel with respect to one another. In particular, in at least this example, in the turning configuration TC , the first longitudinal axis LA1 and the second longitudinal axis LA2 are at an angular displacement, i.e. angle , with respect to one another with respect to the aforesaid plane PL such that said first center of gravity CG1 is at a second lateral/transverse spacing SP2 with respect to the second longitudinal axis. Thus, the second lateral/transverse spacing SP2 is essentially the spacing of the first center of gravity CG1 with respect to the second longitudinal axis LA2 as taken in a lateral and/or transverse direction from the second longitudinal axis LA2 , in the turning configuration TC .

The second spacing SP2 is greater than said first spacing SP1 , and the second spacing SP2 provides a moment arm about the second longitudinal axis LA2 for the thrust vector TV , which thereby results in a turning moment TM for the projectile.

Feature (B) is configured for enabling actuator loads for the actuator system 430 to be minimized, particularly when selectively returning the projectile 10 from the respective turning confirmation TC to the datum configuration DC , or indeed when selectively returning the projectile 10 from a turning confirmation TC having a relatively larger angle  to any other turning configuration TC having a relatively smaller respective angle , with respect to the datum configuration DC . For example, in at least some implementations of this example actuator loads can be reduced by at least 50% as compared with a corresponding steering system in which feature (B) is omitted.

Referring in particular to Figs. 1(a) and 1(b), according to feature (B) the steering mechanism 400 , and in particular the interface portion 500 , for this and other examples 0270259229- of the presently disclosed subject matter, is further configured for ensuring that in the respective datum configuration DC the first center of gravity CG1 is at a first axial spacing AS1 from a reference transverse plane RTP along the second longitudinal axis, and for ensuring that in the turning configuration TC , the first center of gravity CG1 is at a second axial spacing AS2 from the reference transverse plane RTP along the second longitudinal axis LA2 , the second axial spacing AS2 being not less than the first axial spacing AS1 . In other words, the second axial spacing AS2 is equal to or greater than the first axial spacing AS1 .

The reference transverse plane RTP is an imaginary plane orthogonal to the second longitudinal axis LA2 , and located for example aft of the first longitudinal portion 100 , for example aft of the steering mechanism 400 in particular aft of the interface portion 500 . For example, the reference transverse plane RTP can be located at the forward end of the second longitudinal projectile portion 200 .

Thus, during the transition between the datum configuration DC and the turning configuration TC , and at the turning configuration TC , the first center of gravity CG1 is never displaced in an aft direction along the second longitudinal axis LA2 . It is to be noted that at least the first longitudinal portion 100can be designed such that the center of pressure of the first longitudinal portion 100is located at the position of the first center of gravity CG1 . In at least some examples, this can be accomplished, for example by suitably designing the shape of the first longitudinal portion 100and/or by suitably positioning the vanes 120 with respect to the first longitudinal portion 100 . Without being subject to theory, by not allowing the first center of gravity CG1 to be displaced aft of its original position (with respect to the second longitudinal axis LA2 ), it is possible to minimize the actuation forces required for turning the first longitudinal portion 100 with respect to the second longitudinal position 200 from the datum configuration DC to the turning configuration TC , and more particularly for returning the projectile from the turning configuration TC to the datum configuration DC , for example. For example, at launch acceleration forces on the projectile can be very high, for example 15g. If when turning the first longitudinal portion 100 with respect to the second longitudinal position 200 the first center of gravity CG1 were to be displaced aft of its original position (with respect to the second longitudinal axis LA2 ), then to return 0270259229- the first longitudinal portion 100 into alignment with the second longitudinal portion 200 the required actuation force would be a function of the weight of the first longitudinal portion 100 , times the acceleration, which would thus be extremely high, and in at least many cases not practical. By ensuring that the first center of gravity CG1 does not transit aft no such large actuation forces are necessary. It is also to be noted that in examples in which the center of pressure of the first longitudinal portion 100 is at the position of the first center of gravity CG1 , it is also possible to minimize actuator loads when returning the first longitudinal portion 100 into alignment with the second longitudinal portion 200 even when the projectile 10 is travelling at speeds in which significant aerodynamic loads can be induced on the projectile 10 .

Figs. 2, 3(a) and 3(b) illustrate a first example of the interface portion 500 , specifically designated with reference numeral 500A . The interface portion 500A in this example is in the form of a linkage mechanism based geometrically on the so-called Peaucelier-Lipkin circle inversion mechanism, and comprises a pair of first links 510A , a pair of second links 520A , a pair of third links 530A , a guide rod 550A , and a fourth link in the form of a crank 540A , a first fixed position P1 , a second fixed position P2 , and a third fixed position P3 .

The two first links 510A are essentially identical to one another, and each first link 510A has a respective first end 512A and a respective second end 514A , and an axial length L1 . Each said second end 514A being pivotably mounted to the fixed position P1 with respect to the first longitudinal portion 100 , at pin 515A . Fixed position P1 is associated with, and is fixed with respect to, the first longitudinal portion 100 , and in this example is located at an aft end of the first longitudinal portion 100 , at the center of an aft bulkhead 130 thereof, at or in close proximity to the first longitudinal axis LA1 .

Guide rod 550A has a first end 552A , a second end 554A , and axial length L6 . The guide rod 550A is fixedly mounted via the first end 552A to the first longitudinal portion 100 at position P1 , essentially axially aligned with the first longitudinal axis LA1 . The second end 554A is free and includes an axial slot 555A . 0270259229- The two second links 520A are essentially identical to one another, and each second link 520A has a respective first end 522A and a respective second end 524A , and an axial length L2 . The first end 512A of each first link 510A is pivotably mounted to a first end 522A of a respective different one of said two second links 520A , at respective pin 525A . The respective second ends 524A of the two second links 520A are pivotably mounted to one another and to the second longitudinal portion 200 at position P3 via pin 523A . Position P3 is associated with and fixed with respect to the second longitudinal portion 200 , and in this example is located at a forward end of the second longitudinal portion 200 , at or in close proximity to the second longitudinal axis LA2 , and is spaced aft of position P2 by spacing L5 . The pin 523A extends transversely and is slidably movable axially in slot 555A .

The two third links 530A are essentially identical to one another, and each second link 530A has a respective first end 532A and a respective second end 534A , and an axial length L3 . The first end 532A of each third link 530A is pivotably mounted to a first end 512A of a respective different one of said two first links 510A , and to a first end 522A of a respective different one of said two second links 520A , at respective pins 525A . The respective second ends 534A of the two third links 530A are pivotably mounted to one another at pin 533A .

The crank 540A a has a respective first end 542A and a respective second end 544A , and an axial length L4 . The first end 542A is pivotably mounted to the second longitudinal portion 200 at position P2 via pin 545A , and the second end 544A is pivotably mounted to second ends 534A of the two third links 530A at pin 533A . Position P2 is associated with and fixed with respect to the second longitudinal portion 200 , and in this example is located at a forward end of the second longitudinal portion 200 , at the center of bracket 240 that projects forward of a forward bulkhead 230 of the second longitudinal portion 200 , at or in close proximity to the second longitudinal axis LA2 .

Thus, position P1 is fixed with respect to the first longitudinal portion 100 , and positions P2 and P3 are fixed with respect to the second longitudinal portion 200 .

In at least this example, all the pins 515A , 525A , 533A , 523A , 545A provide respective pivoting axes that are parallel to one another and that are orthogonal to plane 0270259229- PN , thereby enabling the first longitudinal portion 100 to be angularly displaced with respect to the second longitudinal portion 200 to provide angle  along plane PN.

In the datum configuration DC, and referring in particular to Fig. 3(a), the first longitudinal axis LA1 and the second longitudinal axis LA2 are coaxial, and each of the pair of first links 510A , the pair of second links 520A , and the pair of third links 530A , are symmetrically disposed about the first longitudinal axis LA1 and the second longitudinal axis LA2 , and the crank 540A is aligned with the second longitudinal axis LA2 , with the second end 544B being closer than the first end 524A with respect to the first longitudinal portion 100 . The position P1 is at a spacing SA1 with respect to position P2 in a direction parallel to the second longitudinal axis LA2 .

In any turning configuration DC, and referring in particular to Fig. 3(b), as the crank 540A is turned about the pivot axis at position P2 defined at pin 545A , responsive to operation of the actuation system 430 , the angle between the two first links 510A diminishes, the angle between the two second links 520A diminishes, and the angle between the two third links 530A diminishes. Concurrently, the distance between pin 533A and pin 515A increases, thereby displacing position P1 away from position P2, such the position P1 is now at a spacing SA2 with respect to position P2 in a direction parallel to the second longitudinal axis LA2 .

The spacing SA2 in this example is greater than spacing SA1 . The first center of gravity CG1 is at a fixed spacing from position P1 , and as the first longitudinal portion 100 pivots about fixed position P1 , the first center of gravity CG1shifts closer to position P1 in a direction parallel to the second longitudinal axis LA2 ; however, this shift is significantly less or equal to than the longitudinal displacement LD (= [second spacing SA2] – [first spacing SA1] ) provided by transitioning between the datum configuration DC and the turning configuration TC , and thus it follows that in the turning configuration TC the first CG1 is not closer to (and in this example can be further spaced from) the second longitudinal portion 200 , in a direction parallel to the second longitudinal axis LA2 .

In other words, interface portion 500A is pivotably mounted to the first longitudinal projectile portion 100 at a respective first fixed position P1 , and the respective first fixed position P1 is displaced away from the second longitudinal projectile 0270259229- portion 100 along a direction parallel to the second longitudinal axis LA2 in said turning configuration TC by a respective first longitudinal displacement LD . Furthermore, the first center of gravity CG1 is displaced towards said respective first fixed position P1 along a direction parallel to the second longitudinal axis LA2 in said turning configuration TC by a respective second longitudinal displacement, said respective second longitudinal displacement being less than respective first longitudinal displacement.

The spacing between position P3 and pin 533A is L7 , while the spacing between position P3 and P1 is L8 .

To comply with feature (B) in this manner, the following conditions apply: L1 = L3 L2 > L1 L5 > L4 Furthermore, the interface portion 500A according to this example also satisfies the condition: L8 * L7 = L2 – L1 = k 2 …wherein " k " is known as an inversion constant.

As the projectile 10 moves from the datum configuration DC to any desired turning configuration TC , point P1 moves along a circle CL (on plane PL or on plane parallel to plane PL ) having center OC inside the first longitudinal portion 100 , forward of point P1 . Circle CL is the inversion of the circle described by the center of pin 533A . the center OC lies on a straight line passing through point P2 and point P3 , and the spacing between point P3 and center OCis L9 .

Dimensions L9 and L5 are related by the expression: L9 = L5 * k /(L5 – L4 ) The radius RA of circle CL can be determined from the following expression: RA = L4 * L9/L5 Thus, as the projectile 10 moves from the datum configuration DC to any desired turning configuration TC up to maximum turning configuration TCmax , the angle  0270259229- between the first longitudinal axis LA1 and the second longitudinal axis LA2 respectively increases from 0  to angle  ≤ angle max, and concurrently there is a axial displacement between the first longitudinal portion 100 and the second longitudinal portion 200 .

Figs. 4, 5(a) and 5(b) illustrate a second example of the interface portion 500 , specifically designated with reference numeral 500B . The interface portion 500B is based geometrically on the so-called Peaucelier-Lipkin exact straight line mechanism, and comprises a pair of first links 510B , a pair of second links 520B , a pair of third links 530B , and a fourth link in the form of a crank 540B , a first fixed position P1' , a second fixed position P2 ', and a third fixed position P3' .

In this example, the first center of gravity CG1 is at (or at very close proximity to) the first fixed position P1' .

The two first links 510B are essentially identical to one another, and each first link 510B has a respective first end 512B and a respective second end 514B , and an axial length L1' . Each said second end 514B being pivotably mounted to the fixed position P1' with respect to the first longitudinal portion 100 , at pin 515B . Fixed position P1' is associated with, and is fixed with respect to, the first longitudinal portion 100 , and in this example is also located at an aft end of the first longitudinal portion 100 , at the center of an aft bulkhead 130 thereof, at or in close proximity to the first longitudinal axis LA1 .

The two third links 530B are essentially identical to one another, and each third link 530B has a respective first end 532B and a respective second end 534B , and an axial length L3' . The first end 512B of each first link 510B is pivotably mounted to a first end 532B of a respective different one of said two third links 530B , at respective pin 525B . The respective second ends 534B of the two third links 530B are pivotably mounted to one another and to the second longitudinal portion 200 at position P2' via pin 533B . Position P2' is associated with and fixed with respect to the second longitudinal portion 200 , and in this example is located at a forward end of the second longitudinal portion 200 , at or in close proximity to the second longitudinal axis LA2 , and is spaced forward of position P3' by spacing L5' .

The two second links 520A are essentially identical to one another, and each second link 520B has a respective first end 522B and a respective second end 524B , and 0270259229- an axial length L2' . The first end 522B of each second link 520B is pivotably mounted to a first end 512B of a respective different one of said two first links 510B , and to a first end 532B of a respective different one of said two second links 530B , at respective pins 525B . The respective second ends 524B of the two second links 520B are pivotably mounted to one another at pin 523B .

The crank 540B a has a respective first end 542B and a respective second end 544B , and an axial length L4 '. The first end 542B is pivotably mounted to the second longitudinal portion 200 at position P3' via pin 545B , and the second end 544B is pivotably mounted to second ends 524B of the two second links 520B at pin 523B . Position P3' is associated with and fixed with respect to the second longitudinal portion 200 , and in this example is located at a forward end of the second longitudinal portion 200 , at the center of bracket 240 that projects forward of a forward bulkhead 230 of the second longitudinal portion 200 , at or in close proximity to the second longitudinal axis LA2 .

Thus, position P1 ' is fixed with respect to the first longitudinal portion 100 , and positions P2 ' and P3' are fixed with respect to the second longitudinal portion 200 .

In at least this example, all the pins 515B , 525B , 533B , 523B , 545B provide respective pivoting axes that are parallel to one another and that are orthogonal to plane PN , thereby enabling the first longitudinal portion 100 to be angularly displaced with respect to the second longitudinal portion 200 to provide angle  along plane PN.

In the datum configuration DC, and referring in particular to Fig. 5(a), the first longitudinal axis LA1 and the second longitudinal axis LA2 are coaxial, and each of the pair of first links 510B , the pair of second links 520B , and the pair of third links 530B , are each symmetrically disposed about the first longitudinal axis LA1 and the second longitudinal axis LA2 , and the crank 540B is aligned with the second longitudinal axis LA2 , with the first end 524B being closer than the second end 544B with respect to the first longitudinal portion 100 . The position P1' is at a spacing SA1' with respect to position P3' in a direction parallel to the second longitudinal axis LA2 .

In any turning configuration DC, and referring in particular to Fig. 5(b), as the crank 540B is turned about the pivot axis at position P3' defined at pin 533B , responsive 0270259229- to operation of the actuation system 430 , the angle between the two first links 510B and changes, the angle between the two second links 520B changes, and the angle between the two third links 530B changes. Concurrently, the distance between pin 545B and pin 515B increases, thereby displacing position P1' away from position P3', such the position P1' is now at a spacing SA2' with respect to position P3' in a direction parallel to the second longitudinal axis LA2 .

The spacing SA2' in this example is equal to spacing SA1' . Since the first center of gravity CG1 is fixed at position P1' , it follows that in the turning configuration TC the first center of gravity CG1 is not closer to (and in this example is equally spaced from) the second longitudinal portion 200 , in a direction parallel to the second longitudinal axis LA2 .

In other words, interface portion 500B is pivotably mounted to said first longitudinal projectile portion 100 at a respective fixed position P1', and said first center of gravity CG1 is located at said fixed position P1' .

The spacing between position P2' and pin 523B is L7' , while the spacing between position P2' and P1' is L8' .

To comply with feature (B) in this manner, the following conditions apply: L1' = L2' L1' > L3 L5 = L4 Furthermore, the steering mechanism 500B according to this example also satisfies the condition: L7' * L8' = L1' – L3' = k' 2 …wherein " k ' " is known as the respective inversion constant.

As the projectile 10 moves from the datum configuration DC to any desired turning configuration TC , point P1 ' moves along a straight line SL (on plane PL or on plane parallel to plane PL ), which is orthogonal to the second longitudinal axis LA2 . Furthermore, straight line SL is at a distance DH from position P2', which can be determined from the following expression: 0270259229- DH = k' /(2 * L4) Thus, as the projectile 10 moves from the datum configuration DC to any desired turning configuration TC up to maximum turning configuration TCmax , the angle  between the first longitudinal axis LA1 and the second longitudinal axis LA2 respectively increases from 0  to angle  ≤ angle max, and concurrently there is a axial displacement between the first longitudinal portion 100 and the second longitudinal portion 200 .

Figs. 6(a) and 6(b) illustrate a third example of the interface portion 500 , specifically designated with reference numeral 500C . The interface portion 500C comprises a linkage mechanism comprising first bracket 510C , a second bracket 520C , a link in the form of a crank 540C , a first fixed position P1 ", a second fixed position P2" , and a third fixed position P3" .

The first bracket 510C is fixedly mounted to the first longitudinal portion 100 . The first bracket 510C comprises a base 512C and extends aft of aft bulkhead 130 a free end 514C of the first bracket 510C . The free end 514C includes a slot 518C extending along the first longitudinal axis LA1 .

Fixed position P2" is associated with, and is fixed with respect to, the first longitudinal portion 100 , and in this example is also located at an aft end of the first longitudinal portion 100 , at the center of base 512C , at or in close proximity to the first longitudinal axis LA1 .

The second bracket 520Cis fixedly mounted to the second longitudinal portion 200 . The second bracket 520C comprises a base 522C and extends forward of forward bulkhead 230 a free end 524C of the second bracket 520C . The free end 524C projects forward into a recess in the aft bulkhead 130 , at least in the datum configuration DC .

Fixed position P1" is associated with, and is fixed with respect to, the second longitudinal portion 200 , and in this example is also located forward of fixed position P3 ", at the center of free end 524C , at or in close proximity to the second longitudinal axis LA2 .

Fixed position P3" is associated with, and is fixed with respect to, the second longitudinal portion 200 , and in this example is also located at a forward end of the second 0270259229- longitudinal portion 200 , at the center of base 522C , at or in close proximity to the second longitudinal axis LA2 .

The crank 540C a has a respective first end 542C and a respective second end 544C , and an axial length L1" . The first end 542C is pivotably mounted to the second longitudinal portion 200 at position P1" via pin 545C , and the second end 544B is pivotably mounted to the first longitudinal portion 100 at position P2" via pin 523C .

Pin 533 is fixedly mounted to second bracket 520C at position P3 ", and passes thorough slot 518C , constraining relative movement between the free end 514C and base 544C to that corresp0nding to relative sliding the pin 533 in slot 518C .

Thus, position P2" is fixed with respect to the first longitudinal portion 100 , and positions P1" and P3" are fixed with respect to the second longitudinal portion 200 .

In at least this example, all the pins 533C , 523C , 545C provide respective pivoting axes that are parallel to one another and that are orthogonal to plane PN , thereby enabling the first longitudinal portion 100 to be angularly displaced with respect to the second longitudinal portion 200 to provide angle  along plane PN.

In the datum configuration DC, and referring in particular to Fig. 6(a), the first longitudinal axis LA1 and the second longitudinal axis LA2 are coaxial, and the first bracket 510C , the second bracket 520C , are each symmetrically disposed about the first longitudinal axis LA1 and the second longitudinal axis LA2 , and the crank 540C is aligned with the second longitudinal axis LA2 , with the first end 524C being closer than the second end 544C with respect to the first longitudinal portion 100 . The position P2" is at a spacing SA1" with respect to position P3" in a direction parallel to the second longitudinal axis LA2 .

In any turning configuration DC, and referring in particular to Fig. 6(b), as the crank 540C is turned about the pivot axis at position P1" defined at pin 545C , responsive to operation of the actuation system 430 , the angular disposition between first bracket 510C and the second bracket 520C changes. Concurrently, the distance between pin 523C and pin 533C increases, as the slot 518C moves with respect to pin 533C , thereby displacing position P2" away from position P3", such the position P2" is now at a 0270259229- spacing SA2 " with respect to position P3" in a direction parallel to the second longitudinal axis LA2 .

The spacing SA2" in this example is greater than spacing SA1 ". The first center of gravity CG1 is at a fixed spacing from position P1" , and as the first longitudinal portion 100 pivots about fixed position P1" , the first center of gravity CG1shifts closer to position P1 " in a direction parallel to the second longitudinal axis LA2 ; however, this shift is significantly less than (or equal to) the longitudinal displacement LD" (= [second spacing SA2 "] – [first spacing SA1 "]) provided by transitioning between the datum configuration DC and the turning configuration TC , and thus it follows that in the turning configuration TC the first CG1 is not closer to (and in this example is further spaced from) the second longitudinal portion 200 , in a direction parallel to the second longitudinal axis LA2 .

In other words, interface portion 500C is pivotably mounted to said first longitudinal projectile portion 100 at a respective first fixed position P1" , and wherein said respective first fixed position P1" is displaced away from the second longitudinal projectile portion 200 along a direction parallel to the second longitudinal axis LA2 in said turning configuration TC by a respective longitudinal displacement LD" . Furthermore, the first center of gravity CG1 is displaced towards said respective first fixed position P1" along a direction parallel to the second longitudinal axis LA2 in said turning configuration TC by a respective second longitudinal displacement, said respective second longitudinal displacement being less than respective longitudinal displacement LD" .

The above examples of the projectile 10 allows for the elevation of the projectile 10 to be rapidly changed from vertical to horizontal very rapidly enabling the projectile to be launched vertically to gain height quickly, and to also adopt a horizontal attitude along the respective direction to reach the target as soon as possible in as a direct manner as possible.

In at least one example, and for example, referring to Fig. 7, the projectile can be launched vertically or close to vertical (for example up to 10  to vertical - to provide a desired from a launch point LP , and at a predetermined time, when the projectile 10 reaches altitude H1 , the steering mechanism 400 operates to transition the projectile 10 0270259229- from the datum configuration DC at launch, to a turning configuration TC , with turning angle  being 10 to 15  for example, thereby causing the projectile 10 to turn towards the ground surface (or sea surface, as appropriate). For example, the steering mechanism 400 , in particular the actuator 430 , can be coupled to a controller 480(Figs. 1(a), 1(b)) for controlling operation of the steering device to provide the desired trajectory TJ towards any on-coming threat, for example.

As the projectile 10 turns and reaches close to a maximum height H2 , the turning angle  is reversed to a suitable angle in the opposite direction, for example in the range -5 to about -20 to change the trajectory TJ again towards a general horizontal direction, under the control of controller 480 . Thereafter, at or close to the desired cruising height H3 , the steering mechanism 400 operates to transition the projectile 10 from the respective turning configuration TC at launch, back to the datum configuration MC , with turning angle  returning to zero or close thereto.

It is to be noted that in at least some other examples, the projectile can instead be launched with a significant elevation angle, for example between 10  and 80 .

Referring again to Fig. 7, it is to be noted that once the projectile 10 achieves a sufficiently high forward velocity, which can be for example at or near the position where the projectile 10 achieves a horizontal or near horizontal attitude (for example at cruising height H3 ), the vanes 120 and/or vanes 220 can be used for further steering the projectile 10 towards the target.

It is to be noted, however, that in some examples, the above trajectory TJ can occur along a particular fixed vertical plane, which as discussed above is plane PL which is the turning plane associated with the interface portion 500 , and thus with the steering mechanism 400 . Thus, the above examples of the projectile 10 can be used with a launch platform that is fixed in azimuth, and thus the above type of trajectory TJ using the steering mechanism 400 is along plane PL that is thus also fixed in terms of azimuth with respect to the launch point LP . Such an example can be useful when it is always expected that the target will be in a particular general direction with respect to the launch point LP – for example coastal defenses, or ship defenses (wherein the ship is suitably oriented viz-a-viz known enemy/threat location. In such cases, the projectile 10 can optionally omit the respective roll system 470. 0270259229- Referring to Fig. 8, the projectile 10 is part of a launch system 20 that includes a launching platform 30 . The launch platform 30 is configured for mechanically holding the projectile 10 in place until launch and for firing the projectile 10when required. For example the launching platform 30 can include a lunch tube or launch tower and base.

According to an aspect of the presently disclosed subject matter, the above examples of projectile 10 can be used for launching the projectile along any desired azimuth via the launching platform 30 .

In one example, the launching platform 30 can be configured for setting the projectile 10 at also desired azimuth with respect to the launching platform, such that when the projectile 10 is launched, the plane PL associated with the steering mechanism 400 is aligned with the desired azimuth with respect to the launch point LP . For example, the launching platform 30 comprises a launch tube 35 in fixed spatial relationship with respect to a base 38 , and the projectile 10 can be accommodated in the launch tube 35 in any desired azimuth orientation prior to launch. In such cases, the projectile 10 can optionally omit the respective roll system 470.

In another example, the launching platform 30 can be configured with a turntable arrangement or other mobile arrangement, for enabling the launching platform 30 (and thus the projectile 10 ) to be effectively rotated about a vertical axis to provide the desired azimuth with respect to the launch point LP , such that when the projectile 10 is launched, the plane PL associated with the steering mechanism 400 is aligned with the desired azimuth with respect to the launch point LP . For example, the launching platform 30 comprises a launch tube 35 that is pivotably mounted with respect to a fixed base 38 , to allow pivoting or rotation of the launch tube 35 with respect to the base 38 about a vertical axis. Thus while the projectile 10 can be accommodated in the launch tube 35 in a fixed azimuth orientation, the launch tube 35 (together with the projectile 10 ) can be pivoted or rotated to any desired azimuth orientation prior to launch. In another example, the launching platform 30 is mounted onto a mobile unit, for example a truck, and the mobile unit can be steered such that the launch tube 35 (together with the projectile 10 ) can be moved to any desired azimuth orientation prior to launch. In such cases, the projectile 10 can omit the respective roll system 470. 0270259229- According to yet another aspect of the presently disclosed subject matter, the projectile 10 is itself configured for providing the desired azimuth for the trajectory TJ , in particular after launch of the projectile 10 . In this connection, the projectile 10 is configured for providing a rotation of at least the first longitudinal projectile portion 100 in roll, i.e. about the roll axis R of the second longitudinal projectile portion 200 , and thus includes the aforesaid roll system 470 .

As mentioned above, roll system 470 is configured for selectively rolling at least the forward longitudinal part 100 of the projectile 10about the second longitudinal axis LA2 about any desired roll angle. In particular, and referring again to Figs. 1(a) and 1(b), the roll system 470 is configured for selectively rolling at least the forward longitudinal part 100 of the projectile 10about the second longitudinal axis LA2 about any desired roll angle. According to an aspect of the presently disclosed subject matter such a desired roll angle is achieved in a manner that is not necessarily dependent on the velocity of the projectile 10 nor on any aerodynamically generated forces acting on the projectile 10 . In this manner, the roll system 470 can be operated, inter alia, in the initial stages of the trajectory of the projectile 10 – where typically the velocity of the projectile 10 can be low and aerodynamic forces induced by control surfaces (such as for example with respect to the vanes 120 and/or vanes 220 ) can be zero or not significant – as well as in an airless environment.

Thus, in at least some alternative variations of the above examples of the projectile 10 including the respective examples of the steering mechanism 400 (for example as illustrated in Figs. 2 to 6(b)), and referring now to Fig. 9 and Fig. 9(a), in a first example of the roll system 470 , the roll system 470 comprises a reaction control system (RCS) 472 including one or a plurality of impulse nozzles 472N configured for selectively providing a thrust component TR spaced by moment arm MX from the second longitudinal axis LA2, to thereby induce a rolling moment RM to the projectile 10 about the second longitudinal axis LA2 . For example, the RCS 472 includes a fuel source 472S , for example pressurized gas, operatively coupled to the impulse nozzles 472Nand a suitable control system (not shown) to control operation of the RCS 472 . For example, the impulse nozzles 472Ncan be longitudinally located close to the longitudinal location of the center of gravity CGT of the projectile 10 to minimize any yaw-roll coupling or pitch-roll coupling. 0270259229- In this example, half of the impulse nozzles 472N are configured for selectively providing a thrust component TR to thereby induce a rolling moment RM about the second longitudinal axis LA2 in a clockwise direction (when viewing the second longitudinal axis LA2 from above), while the other half of the impulse nozzles 472N are configured for selectively providing a thrust component TR to thereby induce a rolling moment - RM about the second longitudinal axis LA2 in a counterclockwise direction. In this manner, it is only necessary to rotate the projectile 10 up to a maximum rotation angle of +180  or -180 to provide the desired orientation of the turning plane PL . In alternative variations of this example, all of the impulse nozzles 472N are configured for selectively providing a thrust component TR to thereby induce a rolling moment RM about the second longitudinal axis LA2 in a clockwise direction (when viewing the second longitudinal axis LA2 from above), or alternatively in a counter clockwise direction, and it is necessary to rotate the projectile 10 up to a maximum rotation angle of 360  to provide the desired orientation of the turning plane PL .

Referring to Fig. 10, in a second example of the roll system 470 , the interface portion 500 is rotatably mounted to the second longitudinal portion 200 , to thereby allow the interface portion 500,together with the first longitudinal portion 100 to be rotated with respect to the second longitudinal portion 200 about the second longitudinal axis LA2 . In the second example thereof, the roll system 470 comprises a bearing arrangement 474 affixed to the second longitudinal portion 200 , and a shaft 475 affixed to an aft end of the first longitudinal portion 100,in particular to an aft end of the interface portion 500, and co-axial with longitudinal axis LA2 . The shaft 475 is rotatably mounted to the bearing arrangement 474for rotation about the longitudinal axis LA2 . The roll system 470 in this example further comprises a drive 476 , operatively coupled to the shaft 475 for example via gear wheel 475A (affixed to shaft 475 ) and gear wheel 476A affixed to the drive 476 . The drive 476 is configured for selectively turning the shaft 475 , and thus the first longitudinal portion 100 , about the longitudinal axis LA2 .

In this example, the drive 476 can selectively rotate the first longitudinal portion 100 about the second longitudinal axis LA2 in a clockwise direction (when viewing the second longitudinal axis LA2 from above) at least up to 180 , and in a counterclockwise direction also up to 180 . In this manner, it is only necessary to rotate the projectile 10 up 0270259229- to a maximum rotation angle of +180  or -180 to provide the desired orientation of the turning plane PL . In alternative variations of this example, the drive 476 can selectively rotate the first longitudinal portion 100 about the second longitudinal axis LA2 in a clockwise direction (when viewing the second longitudinal axis LA2 from above) up to at least 360 , or alternatively in a counter clockwise direction up to at least 360 , to provide the desired orientation of the turning plane PL .

According to another aspect of the presently disclosed subject matter, a boost stage comprising one or a plurality of boost stages can be fitted at the aft end of the second longitudinal portion 200,to provide an augmented projectile 10' . In at least one example, and referring to Fig. 11, the augmented projectile 10' comprises the projectile 10 , for example as disclosed in the above examples, mutatis mutandis, and at least one booster unit 600 . In this example the augmented projectile 10' comprises the projectile 10 , for example as disclosed in the above examples, mutatis mutandis, and two such boosters unit 600 , in co-axial mounted relationship with respect to one another. In alternative variations of this example the augmented projectile 10' comprises the projectile 10 , for example as disclosed in the above examples, mutatis mutandis, and more than two such boosters unit 600 , for example three of more such booster units 600 , in co-axial mounted relationship with respect to one another. Each booster unit 600selectively provides thrust to the augmented projectile in a direction co-axial with the second longitudinal axis LA2.

Each booster unit 600 comprises a rocket motor, for example a solid rocket motor, and propellant. The booster units 600 are affixed to the aft end of the projectile 10 , and are configured for selectively boost acceleration and range of the projectile 10 .for example, in operation of the augmented projectile 10' , the aftmost booster unit 600 is first used for launching and accelerating the augmented projectile 10' from the launch point. Once the propellants are expended the booster unit can be discarded and the next booster unit 600 is then operated to provide additional thrust until its propellant is expended, whereupon this booster unit can now be discarded. At this point, the projectile 10 can operate its propulsion system as in the above examples, mutatis mutandis. The steering mechanism 400 can be operated at any time during the trajectory from launch, i.e., during 0270259229- the time the first booster unit 600 or the second booster unit 600 is in operation, or after the two booster units have ben discarded.

It is to be noted that since the steering mechanism 400 for the projectile 10 is forward of the aft end of the second longitudinal portion 200 , the booster unit 600do not interfere with the steering of the projectile 10 . Thus, any number of booster units can be provided, and thus the same projectile 10 can be used for a wide variety of ranges by adding a respective number of booster units to the augmented projectile 10' such as to provide a desired range. Furthermore, the design of each booster unit can be simple since no steering is required to be provided by the booster units themselves.

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 scope of the presently disclosed subject matter as set out in the claims.

Claims (43)

- 37 - 0270259229- CLAIMS:

1. Projectile comprising: a first longitudinal projectile portion having a first longitudinal axis and a first center of gravity; a second longitudinal projectile portion having a second longitudinal axis and a second center of gravity; a steering mechanism including an actuator system operatively coupled to an interface portion, the interface portion longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said interface portion configured for selectively and reversibly changing an angular relationship between the first longitudinal axis and the second longitudinal axis along a reference plane, between a datum configuration and a turning configuration, responsive to operation of the actuation system, wherein: in said datum configuration, the first longitudinal axis and the second longitudinal axis are parallel to one another, said first center of gravity is at a first minimum transverse spacing with respect to the second longitudinal axis, and said first center of gravity is at a first longitudinal spacing with respect to the second longitudinal portion in a direction parallel to said second longitudinal axis; and in said turning configuration, the first longitudinal axis and the second longitudinal axis are at a non-zero angular displacement with respect to one another along said reference plane such that said first center of gravity is at a second minimum transverse spacing with respect to the second longitudinal axis, and such that said first center of gravity is at a second longitudinal spacing with respect to the second longitudinal portion in a direction parallel to said second longitudinal axis; wherein said steering mechanism is further configured for ensuring that: - said second minimum transverse spacing is greater than said first minimum transverse spacing, to thereby enable a turning moment to be applied to the projectile; and - said second longitudinal spacing is not less than said first longitudinal spacing. - 38 - 0270259229-

2. The projectile according to claim 1, wherein said steering mechanism is configured for providing the projectile with said turning moment, independent of external aerodynamic forces.

3. The projectile according to any one of claims 1 to 2, wherein the first longitudinal projectile portion comprises a plurality of first vanes.

4. The projectile according to any one of claims 1 to 3, wherein the second longitudinal projectile portion comprises a plurality of second vanes.

5. The projectile according to any one of claims 1 to 4, wherein the projectile comprises a propulsion system.

6. The projectile according to any one of claims 1 to 5, wherein said angular displacement is in the range of 1  to 25 .

7. The projectile according to any one of claims 1 to 6, wherein said angular displacement is in the range of 10  to 15 .

8. The projectile according to any one of claims 1 to 7, wherein said angular displacement is up to any one of: 5 , 10, 12, 15 , 20 , 25. .

9. The projectile according to any one of claims 1 to 8, wherein said second longitudinal spacing is equal to or greater than said first longitudinal spacing.

10. The projectile according to any one of claims 1 to 9, wherein said interface portion comprises a first linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said first linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said first linkage mechanism is based geometrically on the so-called Peaucelier-Lipkin circle inversion mechanism.

11. The projectile according to claim 10, wherein said first linkage mechanism is pivotably mounted to said first longitudinal projectile portion at a respective first fixed position, and wherein said respective first fixed position is displaced away from the second longitudinal projectile portion along a direction parallel to the second longitudinal axis in said turning configuration by a respective first longitudinal displacement.

12. The projectile according to claim 11, wherein said first center of gravity is displaced towards said respective first fixed position along a direction parallel to the - 39 - 0270259229- second longitudinal axis in said turning configuration by a respective second longitudinal displacement, said respective second longitudinal displacement being less than respective first longitudinal displacement.

13. The projectile according to any one of claims 1 to 9, wherein said interface portion comprises a second linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said second linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said second linkage mechanism comprises: - a first bracket fixedly mounted to the first longitudinal portion, - a second bracket fixedly mounted to the second longitudinal portion, - a link having an axial length, a first end pivotably mounted to the second longitudinal portion at a first position, and a second end pivotably mounted to the first longitudinal portion at a second position, - the first position being fixed with respect to the second longitudinal portion, - the second position being fixed with respect to the first longitudinal portion, - relative movement between the first bracket and the second bracket being constrained at a third position, different from said first position and said second position, wherein said third position is fixed with respect to the second longitudinal portion.

14. The projectile according to claim 13, wherein said second linkage mechanism is pivotably mounted to said first longitudinal projectile portion at a respective second fixed position, and wherein said respective second fixed position is displaced away from the second longitudinal projectile portion along a direction parallel to the second longitudinal axis in said turning configuration by a respective first longitudinal displacement.

15. The projectile according to claim 14, wherein said first center of gravity is displaced towards said respective second fixed position along a direction parallel to the second longitudinal axis in said turning configuration by a respective second longitudinal displacement, said respective second longitudinal displacement being less than respective first longitudinal displacement. - 40 - 0270259229-

16. The projectile according to any one of claims 1 to 8, wherein said second longitudinal spacing is equal to said first longitudinal spacing.

17. The projectile according to any one of claims 1 to 8 or 16, wherein said interface portion comprises a third linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said third linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said third linkage mechanism is based geometrically on the so-called Peaucelier-Lipkin exact straight line mechanism.

18. The projectile according to claim 17, wherein said third linkage mechanism is pivotably mounted to said first longitudinal projectile portion at a respective third fixed position, and wherein said first center of gravity is located at said third fixed position.

19. The projectile according to any one of claims 1 to 18, comprising a roll system configured for selectively rolling at least the forward longitudinal part about the second longitudinal axis about any desired roll angle.

20. The projectile according to claim 19, wherein the roll system comprises a reaction control system (RCS) including at least one impulse nozzles configured for selectively providing a thrust component spaced by moment arm from the second longitudinal axis ,to thereby induce a rolling moment to the projectile about the second longitudinal axis.

21. The projectile according to claim 19, wherein the roll system comprises the interface portion rotatably mounted to the second longitudinal portion, to thereby allow the interface portion ,together with the first longitudinal portion to be rotated with respect to the second longitudinal portion about the second longitudinal axis.

22. The projectile according to any one of claims 1 to 21, further comprising a boost stage comprising one or a plurality of boost stages fitted at an aft end of the second longitudinal portion.

23. The projectile according to any one of claims 1 to 22, further comprising a controller operatively coupled to the steering mechanism and configured for controlling operation of the steering mechanism to provide a desired trajectory for the projectile. - 41 - 0270259229-

24. The projectile according to any one of claims 1 to 23, configured for being launched in a general vertical direction, and for operating the steering mechanism at a predetermined height to provide a desired said angular displacement to thereby turn the projectile away from a vertical trajectory.

25. The projectile according to any one of claims 1 to 24, configured for providing a trajectory along a desired azimuth.

26. A launch system comprising: - a projectile as defined in any one of claims 1 to 25; - a launcher configured for launching the projectile in a generally vertical direction.

27. The launch system according to claim 26, wherein the launcher comprises a launch tube configured for launching the projectile from a pre-launch configuration in which the projectile is accommodated in the launch tube

28. The launch system according to claim 27, wherein the launcher is rotatably mounted to a fixed base, to allow pivoting or rotation of the launch tube with respect to the base about a vertical axis.

29. A method for steering a projectile, comprising: - providing the projectile, the projectile as defined in any one of claims 1 to 25; - operating the steering mechanism to provide a desired said angular displacement.

30. A steering mechanism for a projectile, the projectile comprising a first longitudinal projectile portion having a first longitudinal axis and a first center of gravity, and a second longitudinal projectile portion having a second longitudinal axis and a second center of gravity, the steering mechanism comprising: an actuator system operatively coupled to an interface portion, the interface portion configured for longitudinally interconnecting the first longitudinal projectile portion and the second longitudinal projectile portion, said interface portion configured for selectively and reversibly changing an angular relationship between the first longitudinal axis and the second longitudinal axis along a reference plane, between a datum configuration and a turning configuration, responsive to operation of the actuation system, wherein: in said datum configuration, the first longitudinal axis and the second longitudinal axis are parallel to one another, said first center of gravity is at a first - 42 - 0270259229- minimum transverse spacing with respect to the second longitudinal axis, and said first center of gravity is at a first longitudinal spacing with respect to the second longitudinal portion in a direction parallel to said second longitudinal axis; and in said turning configuration, the first longitudinal axis and the second longitudinal axis are at a non-zero angular displacement with respect to one another along said reference plane such that said first center of gravity is at a second minimum transverse spacing with respect to the second longitudinal axis, and such that said first center of gravity is at a second longitudinal spacing with respect to the second longitudinal portion in a direction parallel to said second longitudinal axis; wherein said steering mechanism is further configured for ensuring that: - said second minimum transverse spacing is greater than said first minimum transverse spacing, to thereby enable a turning moment to be applied to the projectile; and - said second longitudinal spacing is not less than said first longitudinal spacing.

31. The steering mechanism according to claim 30, wherein said steering mechanism is configured for providing the projectile with said turning moment, independent of external aerodynamic forces.

32. The steering mechanism according to any one of claims 30 to 31, wherein said angular displacement is in the range of 1 to 25 .

33. The steering mechanism according to any one of claims 30 to 32, wherein said angular displacement is in the range of 10 to 15 .

34. The steering mechanism according to any one of claims 30 to 33, wherein said angular displacement is up to any one of: 5 , 10, 12 , 15, 20, 25.

35. The steering mechanism according to any one of claims 30 to 34, wherein said second longitudinal spacing is greater than said first longitudinal spacing.

36. The steering mechanism according to any one of claims 30 to 35, wherein said second longitudinal spacing is equal to said first longitudinal spacing.

37. The steering mechanism according to any one of claims 30 to 36, wherein said interface portion comprises a first linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said first linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said - 43 - 0270259229- reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said first linkage mechanism is based geometrically on the so-called Peaucelier-Lipkin circle inversion mechanism.

38. The steering mechanism according to any one of claims 30 to 37, wherein said interface portion comprises a second linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said second linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said second linkage mechanism is based geometrically on the so-called Peaucelier-Lipkin exact straight line mechanism.

39. The steering mechanism according to any one of claims 30 to 37, wherein said interface portion comprises a third linkage mechanism longitudinally interconnecting said first longitudinal projectile portion and said second longitudinal projectile portion, said third linkage mechanism configured for selectively and reversibly changing said angular relationship between the first longitudinal axis and the second longitudinal axis along said reference plane, between said datum configuration and said turning configuration, responsive to operation of the actuation system, wherein said third linkage mechanism comprises: - a first bracket fixedly mounted to the first longitudinal portion, - a second bracket fixedly mounted to the second longitudinal portion, - a link having an axial length, a first end pivotably mounted to the second longitudinal portion at a first position, and a second end pivotably mounted to the first longitudinal portion at a second position, - the first position being fixed with respect to the second longitudinal portion, - the second position being fixed with respect to the first longitudinal portion, - relative movement between the first bracket and the second bracket being constrained at a third position, different from said first position and said second position, wherein said third position is fixed with respect to the second longitudinal portion. - 44 - 0270259229-

40. The steering mechanism according to any one of claims 30 to 39, comprising a roll system configured for selectively rolling at least the forward longitudinal part about the second longitudinal axis about any desired roll angle.

41. The steering mechanism according to claim 40, wherein the roll system comprises a reaction control system (RCS) including at least one impulse nozzles configured for selectively providing a thrust component spaced by moment arm from the second longitudinal axis ,to thereby induce a rolling moment to the projectile about the second longitudinal axis.

42. The steering mechanism according to claim 40, wherein the roll system comprises the interface portion rotatably mounted to the second longitudinal portion, to thereby allow the interface portion ,together with the first longitudinal portion to be rotated with respect to the second longitudinal portion about the second longitudinal axis.

43. The steering mechanism according to any one of claims 30 to 42, further comprising a controller operatively coupled to the steering mechanism and configured for controlling operation of the steering mechanism to provide a desired trajectory for the projectile. For the Applicants, REINHOLD COHN AND PARTNERS By: