EP0437126B1 - System for transmitting guidance instructions for optoelectronically remote-controlled missiles - Google Patents

Description

The present invention relates to a missile order transmission system, for example a surface-to-air missile, guided in optoelectronic mode, that is to say for a missile receiving information from a remote fire control station. guidance transmitted via a laser beam.

The term "remote control" will be understood in its broadest sense, that is to say comprising both beam guidance modes (so-called beam-riding guidance or by simple remote control), in which the guidance is done by following the beam, that the guidance modes except beam (sometimes designated by the term of "remote control" taken in the strict sense), in which one does not follow the beam, the directions of fire control / missile and fire control / target n ' then not being collinear.

The wavelengths used for the transmission of a fire control signal in optoelectronic mode are optical wavelengths, typically in the infrared range (wavelengths generally between 12 and 0.8 μm ), as opposed to signals transmitted using wavelengths in the radio domain.

When an optoelectronic guidance is used, the problem arises of the disturbances introduced by the flame of the missile during the propelled phase of the latter.

In fact, during this propelled phase, the flame can produce disturbances liable to significantly affect the infrared guide beam passing through the flame and the surrounding area. This problem concerns both direct disturbances (own infrared emission from the propellant) and indirect disturbances (turbulence created in the environment producing variations in the refractive index, absorption and diffusion of the beam by the fumes).

However, these disturbances, in particular atmospheric disturbances, manifest themselves over the entire band of usable wavelengths. To minimize the influence of these disturbances, it is therefore necessary to move the sensors away from the axis of the missile and therefore of the flame as far as possible in a transverse direction.

FIG. 1 represents such a missile 1, provided with infrared detectors 2 receiving the optical signal conveyed by the beam 3. To avoid disturbances in the zone 4 around the propellant flame, the sensors 2 are generally mounted at the ends of the fins or of the 5 missile control surfaces.

However, in particular for reasons of storage convenience, the wingspan or control surfaces of current missiles are generally reduced to a minimum. This therefore means that the spacing obtained by placing these sensors at the end of the wing or of the control surface will always be small and, in practice, insufficient.

One of the aims of the invention is to propose a system making it possible to separate the receptors from the missile flame more significantly, while disturbing the aerodynamics of the latter as little as possible.

This last condition excludes in particular the use of deployable rods or similar devices at the end of which would be placed the sensor, (as described, for example, in GB-A-930,961).

Indeed, given the high speeds of modern machines (Mach greater than three), the bending forces exerted on these rods due to their own drag would be such that only thick rods could resist these forces; these rods, due to their own drag, would then have a substantial influence on the aerodynamics of the craft.

To resolve this difficulty, the present invention proposes, essentially, to separate by aerodynamic effect the (or) optical transducer (s), by mounting the sensor on an aerodynamic carrier designed so as to move away from the body of the missile, at least during the powered phase of it.

More specifically, the invention provides a system for transmitting guidance orders for a guided missile, comprising at least one optoelectronic detector receiving a guidance signal transmitted by an optical beam from a remote fire control station, and characterized in that that it comprises at least one aerodynamic carrier, not propelled, connected to the body of the missile by a non-rigid connection allowing it to be towed by the missile during its flight; the assembly is configured so that, under the effect of this traction, the aerodynamic carrier takes an incidence allowing it, in transverse direction, to deviate from the missile body by a distance greater than the extent of the area in which the transmission of the beam is essentially disturbed by the flame of the missile propellant; and this aerodynamic carrier is provided at its rear end, turned in the direction of incidence of the optical beam, with an optical transducer capable of picking up the optical guide signal transmitted by this beam.

Very advantageously, said non-rigid connection comprises an optical fiber optically coupled, at one of its ends, to the transducer arranged on the aerodynamic carrier, so as to inject into the fiber the optical signal received by this transducer and, at its opposite end , to the optoelectronic detector arranged in the body of the missile, so that this detector receives from the fiber the received optical signal injected into it at its other end, and transforms this received optical signal into an electrical guide signal.

Preferably, the non-rigid connection then consists of an optical fiber mechanically and thermally reinforced by sheathing, the tensile force then being essentially transmitted by the sheath of the fiber.

According to an advantageous characteristic, the point of application of the tensile force exerted by the non-rigid connection is offset transversely relative to the body of the aerodynamic carrier by interposition of an intermediate element, so as to increase the moment of this tensile force relative to the center of gravity of the aerodynamic carrier and thus increase the incidence taken by it under the effect of traction.

Preferably, for the uniformity of aerodynamics and for the improvement of the signal / noise ratio, this system comprises a plurality of identical aerodynamic carriers, arranged axially symmetrically around the body of the missile.

Other characteristics and advantages of the invention will appear on reading the detailed description below, made with reference to the accompanying drawings.

FIG. 1, above, shows a missile in the propelled phase equipped with a system for transmitting guidance orders according to the prior art.

FIG. 2 is equivalent to FIG. 1, for the system for transmitting guidance orders according to the invention.

FIG. 3 is a more detailed view of one of the aerodynamic carriers 6 visible in FIG. 2.

As illustrated in FIG. 2, at least one aerodynamic carrier 6 towed at the end of a non-rigid link 7 is added to the missile 1.

Preferably, for uniformity of overall aerodynamics and to improve the ratio signal / noise of the signal received, two carrier / link assemblies are provided, diametrically opposite, but this number and this configuration are not limiting.

One could use as transducer 6 a component ("optoelectronic detector") directly transforming the optical guide signal (beam 3) into an electrical signal and transmitting this electrical signal to the piloting computer inside the missile, via an electrical connection by wire, which would then replace optical fiber.

However, it is preferred to use as a transducer 9 a purely optical transducer whose sole function is to capture, via a focusing lens, the infrared wave of the beam and to inject this signal into an optical fiber, which then constitutes the non-rigid connection 7.

At the other end of this optical fiber 7, there is, in the body of the missile, the optoelectronic detector 2 which will receive as an input the signal injected into the fiber and will output an electrical signal to the computer for guiding the missile. The optoelectronic detector could be a conventional infrared sensor of the same type as those used in current vehicles.

The aerodynamic carrier, shown in more detail in FIG. 3, can take various forms, for example the shape of a dihedral (the carrier will then have a privileged orientation plane), or else, as represented, the same shape as the missile but on a reduced scale, that is to say with a cylindrical body with an ogival end, provided with appropriate stabilization means, for example a skirt or else, as shown, fins 8.

It is important that the aerodynamic carrier is small in order to disturb the overall aerodynamics of the missile as little as possible.

Typically, the diameter of the aerodynamic carrier (its caliber) may be of the order of 1 cm, which will make it possible to accommodate there in the rear part an optical transducer 9 of conventional type, for example of diameter less than 1 cm with a field reception with an opening of around 30 °.

The shape of the aerodynamic carrier will be calculated so that it takes under the effect of the traction of the non-rigid link 7, a certain incidence α relative to the direction δ of the axis of the missile, thus coming to deviate from a distance x (Figure 2) from the axis of the missile, away from the disturbed area 4.

• de la force de traction T exercée par la fibre,
• de la portance aérodynamique F, exercée sur le centre de poussée du porteur aérodynamique, et
• des forces d'inertie, compte tenu de l'accélération imprimée à l'ensemble.

To determine the characteristics of the aerodynamic carrier, we will begin by taking stock of the forces and moments applied to it, under the effect:

• the tensile force T exerted by the fiber,
• the aerodynamic lift F, exerted on the center of thrust of the aerodynamic carrier, and
• inertial forces, taking into account the acceleration imparted to the assembly.

Having thus determined the equilibrium configuration, it will be possible to determine the length of fiber necessary to obtain the desired angular spacing ϑ and transverse x.

It may be necessary, given the high speeds, to take into account the proper drag of the wire (its linear drag is never zero). We then demonstrate that this one, under the effect of speed, takes the form of a parabolic arc.

To accentuate the phenomenon and make the aerodynamic carrier take a higher incidence α, it is possible, instead of directly applying the traction of the fiber to the body of the aerodynamic carrier, to apply this via an intermediate element 10, for example a rod rigid, the layout and length of which will be calculated so increasing the moment resulting from the tensile force exerted by the fiber on the center of gravity G, by spreading the center of thrust.

With regard to the fiber, a sheathed fiber will be chosen, for reasons of mechanical and thermal protection and so that the traction is exerted essentially by the sheath and not by the core of the fiber, with the smallest possible diameter, a compromise to be sought between the highest possible mechanical strength and minimized drag. Typically, the total diameter of the sheathed fiber may be less than 1 mm. Furthermore, the connection must be thin enough to work mainly only in traction, reducing to a minimum any bending force which could result from the inherent stiffness of the sheathed fiber. The length of the fiber will depend on the length of the missile and its flight conditions.

• en phase propulsée, la vitesse de l'engin s'accroît et le porteur aérodynamique prend alors une incidence créant de la portance ;
• il s'éloigne alors du corps de l'engin, ce qui permet au signal reçu par le transducteur optique qu'il porte de n'être que très peu affecté par les perturbations de la flamme ;
• le poste de guidage au sol envoie alors un ordre de guidage par laser, qui est capté par le transducteur et injecté dans la fibre par celui-ci ;
• le signal se propage dans la fibre et il est converti en sortie de la fibre en signal électrique par le détecteur optoélectronique 2 (transformation classique d'un signal optique en signal électrique) ;
• l'engin exécute alors l'ordre de guidage transmis.

The overall operation of the system is as follows:

• in the propelled phase, the speed of the machine increases and the aerodynamic carrier then takes an incidence creating lift;
• it then moves away from the body of the machine, which allows the signal received by the optical transducer which it carries to be only slightly affected by the disturbances of the flame;
• the ground guidance station then sends a laser guidance order, which is picked up by the transducer and injected into the fiber by the latter;
• the signal propagates in the fiber and it is converted at the output of the fiber into an electrical signal by the optoelectronic detector 2 (conventional transformation of an optical signal into an electrical signal);
• the machine then executes the transmitted guidance order.

Claims (7)

1. A guidance command transmission system for a remotely guided missile, including at least one opto-electronic detector receiving a guidance signal transmitted by an optical beam from the distant fire control post,
      characterised in that it comprises at least one non-propelled aerodynamic carrier (6), linked to the body of the missile (1) by a non-rigid link (7) allowing it to be drawn along by the missile during the propulsion phase of the latter,
      the assembly being configured so that, under the effect of this traction, the aerodynamic carrier takes up an incidence (A) allowing it, in the transverse direction, to move apart from the body of the missile by a distance (x) greater than the extent of the zone (4) in which the transmission of the beam is essentially disturbed by the flame of the motor of the missile,
      this aerodynamic carrier being provided at its rear extremity, turned in the direction of incidence of the optical beam, with an optical transducer (9) able to pick up the optical guidance signal transmitted by this beam (3).
2. The guidance command transmission system of Claim 1, in which the said non-rigid link (7) comprises an optical fibre optically coupled:

   - at one of its extremities, to the transducer (9) arranged on the aerodynamic carrier, so as to inject the optical signal received by this transducer into the fibre, and

   - at its opposite extremity, to the opto-electronic detector (2) arranged in the body of the missile, so that this detector receives from the fibre the received optical signal injected into the latter at its other extremity, and converts this received optical signal into an electrical guidance signal.
3. The guidance command transmission system of Claim 2, in which the said non-rigid link (7) is con stituted by an optical fibre mechanically and thermally reinforced by sheathing, the traction force (T) being transmitted essentially by the sheath of the fibre.
4. The guidance command transmission system of Claim 1, characterised in that the aerodynamic carrier (6) is constituted by a cylindrical body with an ogival extremity stabilised by fins (8).
5. System according to Claim 4, characterised in that the diameter of the cylindrical body of the carrier (6) is of the order of 1 cm.
6. System according to one of Claims 4 or 5, characterised in that the aerodynamic carrier (6) includes a rigid transversal stalk (10) to the extremity of which the non-rigid link (7) is fixed.
7. Guidance command transmission system of Claim 1, comprising a plurality of identical aerodynamic carriers, arranged axially symmetrically around the body of the missile.

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