Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B10/00—Means for influencing, e.g. improving, the aerodynamic properties of projectiles or missiles; Arrangements on projectiles or missiles for stabilising, steering, range-reducing, range-increasing or fall-retarding
  • F42B10/02—Stabilising arrangements
  • F42B10/14—Stabilising arrangements using fins spread or deployed after launch, e.g. after leaving the barrel
  • F42B10/16—Wrap-around fins
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B10/00—Means for influencing, e.g. improving, the aerodynamic properties of projectiles or missiles; Arrangements on projectiles or missiles for stabilising, steering, range-reducing, range-increasing or fall-retarding
  • F42B10/02—Stabilising arrangements
  • F42B10/26—Stabilising arrangements using spin

Definitions

• the present invention relates to a projectile adapted to be given a rotation on firing, which makes the projectile spin-stabilized.
• the invention can be used, in particular, as a terminally guided projectile and in general for projectiles which receive an explosive charge with a hollow-charge effect.
• a projectile is fired in a ballistic trajectory in conventional manner but at the end of the trajectory a target-seeking member and guidance electronics are activated which can lead the projectile to a hit or near hit on the target.
• a system with terminally corrected projectiles is less complicated than a robot because continuous guidance is not used.
• the projectile is more difficult to intercept when it follows a ballistic trajectory for great or greater portion of the flight.
• the target seeker is complicated and considerable difficulties arise in correcting the course since the roll position of the projectile must be determined when the guiding signal is given. It has been proposed that the roll direction should be determined in relation to a reference direction by means of the so-called rate-gyro and integration. This proposal is not without problems, however, because the gyro is sensitive to acceleration and can drift. With projectiles which are fired with a gun barrel, the sensitivity to acceleration is a particularly serious problem.
• a projectile which is spin-stabilized is altogether unsuitable for use as a terminally guided projectile or in general if the projectile is to receive for example an explosive charge with a hollow-charge effect where the explosive radiation is adversely affected if the explosive charge rotates.
• the dispersion easily increases since the projectile is sensitive to disturbances at the beginning of the trajectory, that is to say when the fins are extended, and the extension of the fins easily introduces disturbances.
• the length of the projectile has greatly exceeded that which applies to conventional projectiles, which imposes new demands on the handling of ammunition particularly where automatic loading systems are concerned.
• the present invention unites the advantages of the above system while at the same time the disadvantages are reduced to a minimum as a result of the fact that the projectile according to the invention is spin-stabilized when it is fired, after which, at a desired point in the trajectory of the projectile, the rotation is braked so that in the latter part of the projectile's trajectory, the projectile is finstablized.
• the projectile according to the invention is provided with stabilizing fins of the type which are known per se in fin-stabilized projectiles, wherein the fins are able to be extended from a retracted position on firing to an extended position at a desired point in the trajectory of the projectile and so to brake the rotation of the projectile, and wherein the projectile is so dimensioned that its aerodynamic centre of pressure in said extended position is situated behind the centre of gravity of the projectile, so that during braked rotation, the projectile changes over from being spin-stabilized to being fin stabilized.
• the projectile is shown with a base bleed unit 1 which gives an increased range of fire in known manner by giving off gas which increases the reduced pressure at the base end of the projectile.
• the projectile In its back portion, the projectile is provided with four stabilizing fins 6-9 of the type which is known per se in fin-stabilized projectiles.
• they consist of so-called wrap-around fins, that is to say fins which, in the retracted position, largely follow the outer shell surface of the projectile.
• the fins 6-9 are held in the retracted position by means of locking members in the form of four conventional covering plates 2-5, which are held in place by the base bleed unit 1 as a result of the fact that this tightly surrounds the back portion of the covering plates.
• a delay device not shown in the projectile is dimensioned so as to initiate, at a desired point of the trajectory, the throwing off of the base bleed unit 1 so that the covering plates 2-5 are automatically removed and expose the fins 6-9. These are so dimensioned, in known manner, that they extend through a combination of centrifugal forces and aerodynamic forces and afterwards, likewise in know manner, are locked in the extended position.
• the delay device which can contain a pyrotechnic charge, for example, is of conventional type well known to the expert so that it does not need to be shown or described here.
• the projectile In its front position, the projectile comprises four nose rudders 10 which can each be extended through its slot 10a, see Figure 3, to guide the projectile in its later, fin-stabilized part of the projectile trajectory.
• the nose rudders 10 are adapted to be extended through the slots 10a when a predetermined braking of rotation is reached in the projectile.
• the initiation of the extension of the nose rudders may alternatively be effected by means of a delay device of conventional type, not shown.
• the guiding of the projectile can alternatively take place by means of pulses from one or more steering nozzles, in which case the nose rudders can be dispensed with entirely.
• the projectile further comprises four covering plates 11-13 in a nose portion, which are adapted, through initiation by a delay device not shown, to be removed from the projectile after this has become finstabilized and to expose a target tracking optical system of the like, not shown, see Figure 3.
• the stabilizing fins 6-9 in the manner described above, and on the other hand such a dimensioning of the projectile that its aerodynamic centre of pressure, that is to say the point where the air forces act, are situated behind the centre of gravity of the projectile in the extended position of the fins.
• the projectile is further so dimensioned that its centre of pressure also lies behind the centre of gravity of the projectile when both the fins 6-9 and the nose rudders 10 are extended.
• the projectile is so dimensioned that its centre of pressure lies somewhat in front of the centre of gravity of the projectile when the fins 6-9 and the nose rudders 10 are in the retracted position, that is to say in the first part of the trajectory of the projectile, when the projectile is spin-stabilized.
• the centre of pressure should lie in front of the centre of gravity in this manner, it is nevertheless conceivable, within the scope of the invention, to position the centre of pressure in or behind the centre of gravity of the projectile instead.
• the mode of operation of the projectile described is as follows: When the projectile is fired from a barrel not shown, it is given a relatively high speed of rotation (of the order of magnitude of 300-2000 rad/sec), for example by means of conventional projectile driving bands. At a predetermined, desired point in the trajectory of the projectile the base bleed unit 1 is thrown away so that the covering plates 2-5 are removed and the fins 6-9 exposed. These are extended and brake the rotation of the projectile. As a result of the above-mentioned dimensioning of the fins and the projectile, the projectile changes over from being spin-stabilized to being finstabilized. The terminal guidance and target-seeking function of the projectile or the triggering of the explosive charge of the projectile with a hollow-charge effect can now take place.

Landscapes

• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)
• Analogue/Digital Conversion (AREA)
• Ultra Sonic Daignosis Equipment (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20338905

Family Applications (1)

Country Status (8)

Cited By (13)

Families Citing this family (32)

Citations (11)

Family Cites Families (8)

• 1979
  • 1979-09-27 SE SE7908002A patent/SE432670B/sv unknown
• 1980
  • 1980-09-25 US US06/570,423 patent/US4546940A/en not_active Expired - Fee Related
  • 1980-09-25 WO PCT/SE1980/000228 patent/WO1981000908A1/en active IP Right Grant
  • 1980-09-25 JP JP55502239A patent/JPS6136159B2/ja not_active Expired
  • 1980-09-25 DE DE8080901895T patent/DE3064144D1/de not_active Expired
  • 1980-09-25 EP EP80901895A patent/EP0039681B2/en not_active Expired
• 1981
  • 1981-05-26 NO NO811776A patent/NO148347C/no unknown
  • 1981-05-26 DK DK230081A patent/DK145939C/da not_active IP Right Cessation

Patent Citations (11)

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