Attitude-Controlling System and a Missile Equipped With Such a System

1. Field of the Invention

The invention relates to a system for controlling the attitude of a cylindrical body moving in a fluid, and more particularly to a system for controlling roll and its application to missiles. The roll-controlling system of the invention employs the fluid dynamic reaction forces set up by a rotating empennage.

2. Description of the Prior Art

In the text, the term "missile" is to be understood in its generic sense, which covers, inter alia, projectiles, rockets, and propelled or unpropelled missiles whose trajectory may or may not be controlled.

When a missile is moving in a fluid medium, either gas or liquid, it naturally tends to pivot about its longitudinal axis, also known as its roll axis, which axis is substantially coincident with the speed vector along the trajectory. This rotating movement is induced, when the missile is moving, by parasitic hydrodynamic or aerodynamic moments and/or thrust moments. These parasitic moments are due to constructional imperfections. The direction and magnitude of this rotational movement, or natural roll, are determined by the direction and magnitude of the resultant of the parasitic moments.

In certain missile firing applications, the attitude of the missile in roll needs to be positionally controlled and held by servo-control in a given direction, for example, when the missile is equipped with an auto-pilot or a military homing head. In other applications, on the other hand, it is desirable for the body of the missile to have imparted to it a rotary movement whose speed needs to be controlled within a more or less restricted range, for example, with the object of enabling a detector carried by the missile to operate at a known scanning frequency.

Techniques for controlling the attitude of missiles are widely known, in particular those which use aerodynamic control surfaces derived from the control surfaces of aircraft. Mention may be made of ailerons carried by the wings and canard control surfaces positioned at the front of the fuselage. A very different technique uses the reaction forces resulting from the expulsion of gases. These various techniques give rise to problems when the missiles are employed operationally in applications which involve special conditions of storage, handling and launching, in particular when this latter operation is performed from within a cylindrical tube or by gun-barrel effect.

The object of the invention is an attitude controlling system which employs the anti-roll torque setup by a rotating empennage and its application to controlling the roll of the body of a missile. Such a system is chiefly formed by a rotating empennage concentric with the body whose attitude it is desired to control. The system is applicable to any cylindrical body moving in a fluid. The connection between the empennage and the body is provided by a torque transmitter.

The following description, which refers to the accompanying drawings, describes a plurality of embodiments of the invention by way of entirely non-limiting example.

FIG. 1 is a diagram which shows the basic principles of the invention;

FIG. 2 is a diagrammatic cross-section showing the application of the attitude controlling system to a roll-stabilized missile;

FIG. 3 shows a modified embodiment applied to a missile equipped with means of propulsion; and

FIG. 4 shows a modified embodiment applied to a missile equipped with jettisonable propulsion means.

In all the figures the same reference numerals indicate similar components.

FIG. 1 shows the elements of the invention in a simplified and schematic form. There can be seen the body 1 of a missile of which it is desired to control the attitude in roll and an empennage 2 which is able to rotate freely about an axis X. The connection between parts 1 and 2 is provided by a torque motor 3 which consists of a rotor R and a stator S. Within the body 1 are mounted the known elements of servo-control means, namely an attitude detector 4, an amplifier unit 5 and an electrical power supply 6.

The fins 7 of the rotary empennage 2 are characterized by the angle .alpha. at which they are set, i.e., the angle which the plane of the fins 7 makes with axis X, and by their angle of sweep-back .beta., i.e., the angle which the edge of the fins 7 makes with the perpendicular and with axis X, and also by their length and width. The angle .alpha. at which the fins 7 are set is of a fixed value between 0.degree. and 5.degree..

The method of operation is as follows: the missile is moving in a fluid in direction X when the attitude detector 4, which may be gyroscopic for example, detects that the body 1 of the missile is rolling. It gives out an electrical signal proportional to the divergence measured. This divergence signal is amplified by the amplifier unit 5 and is applied to the rotor of the torque transmitter 3. The size of the restoring torque produced depends on the aerodynamic effectiveness of the fins 7 on the relative speed of movement of the missile and on the amount of divergence from the correct attitude. When the fins 7 are mounted on a pivot, they are able to be unfolded. The rotary empennage 2 and the associated components 4, 5, 6 form a means of servo-controlling position or speed, depending upon the desired application. In an example where speed is controlled, the attitude detector 4 is a rate gyro. The torque transmitter 3 may, inter alia, be a torque motor, an electromagnetic clutch, or an alternator. The stability of the servo-control means is determined by the transfer function of the components 4, 5 and 6 associated with the rotary empennage 2 as a whole. It is well-known to those skilled in servo-mechanisms how to obtain the characteristics of these components and more particularly those of the correcting electrical circuits inserted in the chain of control.

FIG. 2 is a sectional view of the system of the invention when applied to a roll-controlled missile. The rotary empennage 2 and its torque transmitter 3 are built into the base of the missile. The rotational independence between the body 1 of the missile and the empennage 2 is improved by using ball-bearings which are not shown. The fins 7, which are between 4 and 8 in number in practice, are advantageously of the unfoldable type. The torque transmitter 3 is an electrical torque motor whose field circuit S is formed by a permanent magnet attached to the inside of the body 1 of the missile. The rotor R connected to the rotary empennage 2 receives the torque generating current via a brush-type collector (not shown). The components forming the associated parts of the servo-control means, such as the attitude detector 4, the amplifier unit 5 and the source 6 of electrical energy are located within the body 1 of the missile. The auxiliary operations of starting, unlocking and uncaging the gyroscope are as currently employed during the launching phase of missiles.

FIG. 3 shows a modification of the previous appliction.

The sectional view shows the application of the system of the invention to a missile equipped with propulsion means 10. The fins 7 of the rotary empennage 2 are situated at the point where the nozzle 11 of the propulsion means 10 is situated. They may be of the unfoldable type.

FIG. 4 shows a modified application of the invention in the case of a type of missile equipped with a jettisonable propulsion stage 20. The propulsion stage 20, which is secured to the rotary empennage 2 of the missile stage proper, incorporates seatings 12 for the foldable fins 7 and an additional set of fins 13 situated near the nozzle 11.

When the missile is launched, the fins 13 situated in the vicinity of the nozzle 11 are unfolded and the fins 7 of the missile stage are held captive by the propulsion stage 20. At the end of the combustion period, the propulsion stage 20 is automatically jettisoned, thus freeing the fins 7 of the missile stage.

The system of the invention has a number of positive advantages over known systems. In particular it enables the roll of the body to be controlled using a single servo-control. The axial layout of the parts gives constructional strength, thus allowing launching by gun-barrel effect. The system is compatible with different designs of missile, certain of which are illustrated by way of example in FIGS. 2, 3 and 4.

The present invention and its application to missiles has however been described and illustrated simply by way of non-limiting explanation.