Ammunition and explosives – Igniting devices and systems – Multiple mode fuzes
Reexamination Certificate
1998-04-03
2001-04-17
Jordan, Charles T. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Multiple mode fuzes
C102S200000, C089S006500, C244S003150
Reexamination Certificate
active
06216595
ABSTRACT:
BACKGROUND OF THE INVENTION
The technical scope of the invention is that of processes enabling the in-flight programming of a time to trigger a projectile element form the fire control system of a weapon.
Projectiles fired from a cannon theoretically have a well-known ballistic trajectory.
However, certain non-reproducible external factors are able to influence this trajectory.
It is known that the muzzle velocity (Vo) of the projectile can vary by a few percent from one powder charge to another depending on the firing conditions, for example, temperature, consistency of the characteristics of the powder, and barrel wear. This results in deviations in the impact on the ground of the projectile, the ground impact point varying from 1 to 35 km from the firing weapon system.
The atmospheric conditions as well as the differences concerning the drag coefficient of the projectile also notably influence its trajectory.
So as to improve firing accuracy, it is known to transmit an order to correct the trajectory to the projectile.
U.S. Pat. No. 3,995,792 thus describes a projectile whose actual trajectory is measured using laser tracking means. A fire control system using this measurement computes the deviation between the actual trajectory and the theoretical trajectory and transmits corrective orders to the projectile enabling the actual trajectory to draw nearer to the theoretical trajectory.
The trajectory is corrected, for example, using boosters or steering fins.
One drawback of such a solution is its cost. In fact, the tracking of the projectile trajectory requires the implementation of powerful (and therefore expensive) means whose range extends beyond 15 km.
Such tracking means are also bulky and are difficult to implement.
Additionally, the use of laser tracking over a major part of the trajectory prejudices firing secrecy and creates the risk of making it easier for hostile forces to locate the artillery.
A fully autonomous projectile is also known which locates its own position by means of a global positioning system (GPS).
Before firing, the projectile is programmed with its theoretical trajectory and the desired ground impact point. It measures its own actual trajectory and, using suitable algorithms, controls the implementation of trajectory correcting means.
Such a projectile is extremely costly, since it integrates an electronic unit combined with a global positioning system. Moreover, the global positioning system is bulky and prejudices the on-board load capacity of the projectile.
Patent WO84/03,759 describes a device which increases the precision of artillery firing. This device implements a speedometer, a projectile tracking radar and radio transmission means.
The radar tracks the projectile over its full trajectory and a second radar monitors the position of the target. The fire control system transmits a trajectory correction order at a given time to the projectile in order to bring it closer to its target.
Such a device is costly to implement, since two radars are required; one to track the target, the other to track the projectile. Secrecy is not ensured either, since the correction order is sent far from the firing platform.
SUMMARY OF THE INVENTION
The aim of the invention is to propose a process (and associated fire control system system) enabling the in-flight programming of a trigger time for a projectile element, process and fire control system which are free from the drawbacks characterizing known systems.
Thus, the process according to the invention enables firing accuracy to be substantially improved without requiring the use of expensive equipment.
Furthermore, it does not adversely affect the firing secrecy of the weapon system.
A further aspect of the invention is a fuse intended to equip a projectile and to be programmed by the process according to the invention.
This simple and inexpensive fuse can be adapted to any type of projectile and thus enables the firing accuracy of conventional projectiles already in store in the armed forces to be improved.
Thus, the subject of the invention is a process for the in-flight programming of a trigger time for a projectile element by a weapon fire control system, the process comprising the following steps:
the muzzle velocity (Vo) of the projectile is measured,
the distancing velocity of the projectile at at least one other point during its trajectory after exiting the weapon barrel is measured,
based on these measured values an optimal trigger time is determined for the projectile element so as to minimize the difference between the actual ground impact point and the desired ground impact point for the projectile or for a payload released during its trajectory,
a programming or corrective programming is transmitted to the projectile which takes this optimal trigger time into account.
Advantageously, in order to determine the optimal trigger time, it is possible to:
determine the difference with respect to the predictable ground impact point which can be attributed to the variation measured in the muzzle velocity (Vo) of the projectile,
deduct the predictable deviation with respect to the ground impact point attributable to the variation in aerodynamic drag by subtracting from a measurement of the distancing velocity the variation in distancing velocity attributable to the variation in muzzle velocity,
add the two predictable deviations thus estimated.
To determine the optimal trigger time, it is also possible to:
determine the predictable deviation with respect to the ground impact point by carrying out a linear combination of the differences in velocity measured at at least two points.
According to a variant embodiment of the process, it is possible to:
before firing, program a theoretical trigger time taking into account the characteristics of the required theoretical trajectory,
after firing, transmit a correction to the initial programming to the projectile.
Alternatively, a program is transmitted to the projectile after firing in the form of a trigger time counted from a reference time.
In any event, transmission to the projectile will be carried out in the first moments of the projectile trajectory, for example at a distance from the weapon less than or equal to ten kilometers.
A further subject of the invention is a fire control system implementing such a process, such fire control wherein the system comprises a speedometer, a computer and transmission means.
The tachometer will advantageously use radar technology.
The transmission means can be formed by the radar speedometer itself.
On other subject of the invention is a programmable fuse intended to be installed on a projectile and programmed by such a fire control system, the fuse comprises a timer, a receiver, a computation unit and an element which is triggered during the trajectory.
The element triggered during the trajectory can be means to brake the projectile thus modifying its aerodynamic drag, or else a pyrotechnic charge to eject at least one sub-munition.
One of the advantages of the invention lies in the fact that it enables the rapid acquisition of an estimated trajectory of a projectile using simple and inexpensive means.
Another advantage of the invention is that it promotes firing secrecy, the distancing velocity measurements being few in number (from one to three), carried out periodically rather than continuously and at a short distance from the weapon.
A further advantage is that the fuse is programmed at a reduced distance from the weapon thereby improving programming reliability and reducing its vulnerability to scrambling.
REFERENCES:
patent: 3995792 (1976-12-01), Otto et al.
patent: 4237789 (1980-12-01), Stauers et al.
patent: 4283989 (1981-08-01), Toulios et al.
patent: 4837718 (1989-06-01), Alon
patent: 5440990 (1995-08-01), Wiedefeld et al.
patent: 5787785 (1998-08-01), Muenzel et al.
patent: 5814755 (1998-09-01), Boss
patent: 5814756 (1998-09-01), Boss
patent: 5834675 (1998-11-01), Boss
patent: WO 83/03894 (1983-11-01), None
patent: WO 84 03759 (1984-09-01), None
patent: WO 89 07744 (1989-08-01), None
patent: WO 96/256
Bredy Thierry
Lamorlette Gérard
Giat Industries
Jordan Charles T.
Oliff & Berridg,e PLC
Semunegus Lulit
LandOfFree
Process for the in-flight programming of a trigger time for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the in-flight programming of a trigger time for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the in-flight programming of a trigger time for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2536776