Aeronautics and astronautics – Missile stabilization or trajectory control – Externally mounted stabilizing appendage
Patent
1981-11-20
1984-07-17
Schafer, Richard E.
Aeronautics and astronautics
Missile stabilization or trajectory control
Externally mounted stabilizing appendage
F42B 1516
Patent
active
044601379
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a ballistic artillery projectile, that is initially spin-stabilized and provided with extendable fins, designed to be extended after the projectile has covered a part of the trajectory.
The development in the artillery field, both the land and the sea artillery fields, has resulted in an increased range of fire, for example by means of so-called base bleed units. The increased range of fire is naturally desirable but it leads to increased aboslute dispersion of the projectiles. This increased dispersion is very unfavorable, all the more so as a change in the threat picture has become noticeable towards a greater frequency of smaller and harder elementary targets where each elementary target has to be combatted. In order to reduce the dispersion of the projectiles, terminal correction of terminal guidance of the projectiles has been proposed. This means that a projectile is fired in a ballistic trajectory in a conventional manner but at the end of the trajectory a targetseeking device and guidance device are activated which can lead the projectile to a hit or near hit on the target. Compared with a radical exchange of tube artillery for missiles, a system with terminally corrected projectiles is less complicated to handle and cheaper. The projectile is also less complicated than a missile because continuous guidance is not used. Moreoever, the projectile is more difficult to disturb as it follows a ballistic trajectory for a great or greater portion of the flight.
Different solutions to this problem have been introduced. Conventional artillery ammunition is spin-stabilized over the whole trajectory, that is it has a high speed of rotation (of the order of magnitude of 300-2000 rad/sec). Solutions to the problems of terminal guidance of projectiles which are spin-stabilized over the whole trajectory have been put forward. The advantages of such a system are that a completely conventional firing can be effected with ammunition effects which differ little in size and weight from conventional ammunition. The disadvantages are the very complicated guiding and the limited range of control as well as the very uncertain possibilities of realization.
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 so-called rate-gyros and integration. This proposal is not without problems, however, because gyros are sensitive to acceleration and can drift. With projectiles which are fired with a gun barrel, the sensitivity to acceleration is a particularly serious problem.
The majority of solutions hitherto put forward to the problems of terminal guidance mean that the projectile is provided with so-called rotating driving bands which means that the projectile has a low speed of rotation (of the order of magnitude 0-200 rad/sec) when it leaves the muzzle. This means that stabilizing fins must be extended immediately outside the muzzle. The advantage of this system with low or no speed of rotation in the trajectory is that target seeking and guiding can be fairly simple. In addition, certain warheads, such as explosive charges with a hollow-charge effect, require a low speed of rotation to give a good result. The disadvantages of this system are that the range of firing is adversely affected. Moreover, 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. Moreover, with the solutions hitherto proposed, 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.
Swedish patent application 79 08002-4 relates to an invention, which com
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Andersson Kurt G.
Axelsson Gunnar E.
Bartelson Nils E.
Bondesson Stig H.
Bryngelsson Arne H.
Ryan Maureen T.
Schafer Richard E.
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