GB2127944A

GB2127944A - Method for evaluating offset of point of impact of projectile in gun trainer or simulator

Info

Publication number: GB2127944A
Application number: GB08324112A
Authority: GB
Inventors: Dr Robert Stickel
Original assignee: Honeywell GmbH
Current assignee: Honeywell GmbH
Priority date: 1982-09-30
Filing date: 1983-09-08
Publication date: 1984-04-18
Also published as: FR2534011A1; GB8324112D0; FR2534011B1; DE3236206C1

Abstract

The method evaluates the vertical offset DELTA H of the simulated point of impact (X) of the projectile with respect to a target (Z) onto which a sight is aligned, and displays the offset according to the function DELTA H = k1. k2. DELTA E, where k1 is a factor dependent on the type of ammunition, k2 is a factor dependent on momentary target range and DELTA E is a value corresponding to the range error. The range error is determined by calculating the intersection of the projectile trajectory (F) with the line of sight (V). <IMAGE>

Description

SPECIFICATION Method for evaluating the offset of the point of impact of a projectile in gun trainers On gun trainers or simulators, it is desirable to make the point of impact of the projectile visible to the person being trained, so that the gunner can observe whether the aim is too short or too long and can then make an appropriate correction.

In one known form of simulator for the crew of ballistic weapons and missiles, the simulator allows the simulation of the point of impact of the projectile at a corresponding spot when the target is not hit by the projectile. The simulator comprises a computer in which is digitally stored a terrain model, the momentary coordinates of the projectile along the trajectory being computed in real time and concurrently compared with the height of the terrain below the projectile. If the height of the projectile is greater than the height of the terrain, then computation of the trajectory proceeds incrementally until the height of the projectile is smaller or equals the height of the terrain. If the target is located at the point of intersection between the trajectory and the terrain model, a hit is indicated; otherwise a lost round with a corresponding offset is indicated.This known simulator required a cumbersome survey and measuring of the coordinates of the terrain model as well as memorization of said coordinates in a digital mass storage. Furthermore, the terrain model must not experience any changes after its surveying and measuring.

To prevent such cumbersome storage of coordinates in a mass storage, it is known to consider only the momentary status of the terrain by scanning only this part of the terrain which is flown over by the projectile in a timely synchronous and concurrent manner during fire simulation.

This part of the terrain is of interest with respect to the simulated trajectory. To this end the direction of a range meter in real time is succeedingly directed to the different coordinates of the trajectory. The evaluated measured value of the momentary range between a reference point to an object or terrain point, respectively, i.e. the measured range, is compared with the range between the momentary coordinates of the trajectory and the reference point. In the event where both ranges are equal an intersection between said trajectory and the terrain exists which can be indicated.

During implementation of this method, a difficulty arises in that the range meter must be synchrononously directed, i.e. in real time, to the trajectory. This results in difficulties with respect to the follow-up by means of the control circuits, where each error due to possible terrain steps results in considerable inaccuracies of the method.

Finally it is known to survey three points of the terrain in the neighbourhood of the target and to approximate the terrain by means of an inclined plane with which the intersection point of the trajectory is computed and in impact of the projectile is simulated at this computed point.

These prior simulators and methods are too complex in view of the required computing time and costs, and.it is an object of the present invention to provide a simple and inexpensive method whereby a realistic simulation of the point of impact is provided.

According to the invention there is provided a method for evaluating in a gun trainer or simulator the offset of the impact point of a projectile with respect to a target onto which a sight is aligned, wherein the vertical offset of the simulated point of impact (X) of the projectile is displayed according to the function AH = k,. k2. AE where AH = vertical offset, k, = factor, dependent on type of ammunition, k2 = factor, dependent on momentary target range, AE = range error.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a sketch for a shot being offset with respect to the target; and Figure 2 is a diagram showing the relative deviation in height as a function of the terrain angle at different ranges of the target.

Referring to Fig. 1, an observer or gunner is located at point 0 and looks along a line of sight V to a target Z which is arranged in an inclined terrain G. If the trajectory F of a projectile is too short, it will intersect the terrain G at a point of impact X in front of the target Z. In the region of the target Z the projectile falls with the angle a with respect to the horizontal line. The terrain G is inclined under the angle ss with respect to the horizontal line and the point of impact X of the projectile is vertically offset by the amount AH with respect to the target Z. The range error AE may be evaluated by computing the intersection S between the trajectory F and the line of sight V and by subtracting the range OS from the range OZ.

The height of impact, i.e. the vertical offset, at a shot which does not hit the target Z may be computed as follows: tan α . tan ss #H=#E . ----------- (1) tan α + tan ss This equation is valid independent of whether the shot is too short or too long.

With respect to the sight this vertical offset results in the following error angle: A AH for AE E E With all direct firing weapons commonly the angle of fall of the projectile is very small. Even with slower types of ammunition and with larger ranges the angle of fall is smaller than 1 so that the value of tan a in equation (1) may be replaced by the angle a. Therefore equation (1) becomes: AH tan ss = a . (2) AE a+tan ss This relationship is shown in the diagram of Fig. 2, where the relative offset in height AH/AE is shown as a function of the terrain angle ss and the range E and the angle of fall a are chosen as parameters.The table below shows this relationship by means of actual figures: Table AH Terrain Angle ss/ Relative Offset in Height AE Parameter 1 Parameter 2 Parameter 3 E = 1500 m E = 2000 m E = 2500 m a = 28.4mrd a =48 mrd a = 74 mrd 1 0.0108 0.0133 0.0142 2 0.0157 0.0202 0.0237 5 0.0214 0.0310 0.0401 10 0.0245 0.0377 0.0521 15 0.0257 0.0407 0.0580 20 0.0263 0.0424 0.0615 25 0.0268 0.0435 0.0639 30 0.0269 0.0443 0.0659 90 0.0284 0.048 0.074 From the curves of the diagram and the figures of the table, respectively, one may note that all figures tend toward a final value of terrain angle of ss = 90 . This final value corresponds to the intersection value in the vertical target plain ZDE.Furthermore, one may clearly recognize that with small terrain angles a very steep increase of the vertical offset appears and that with a terrain angle of 5" at least 50% of the final value is attained.

From this fact a very important conclusion may be made; namely, that an estimation of the required fire correction is not possible from the visible vertical offset AH because of the unknown terrain angle ss which is also affirmed by the common firing instructions in practice.

Therefore, with trainers and simulators it is not necessary to take into account the terrain angles by means of a mathematical model; moreover it is sufficient to display the elevation or depression, dH of the point of impact X with respect to the target Z by means of a simple function as for instance AH = kl. k2. AE (3) where k1 is a factor dependent on the type of ammunition and k2 is a factor dependent on momentary target range.

Claims

1. Method for evaluating in a gun trainer or simulator the offset of the impact point of a projectile with respect to a target onto which a sight is aligned, wherein the vertical offset of the simulated point of impact (X) of the projectile relative to the target (Z) is displayed according to the function AH = k1. k2. AE where AH = vertical offset, k, = factor, dependent on type of ammunition, k2 = factor, dependent on momentary target range, AE = range error.

2. Method according to Claim 1, wherein the range error hE is determined by calculating the intersection of the projectile trajectory (F) with the line of sight (V).

3. A gun trainer or simulator method substantially as herein described.