The main task of the tank is to ensure effective firing from a cannon from a place and on the move in any meteorological conditions against a moving and stationary target. To solve this problem, the tank has devices and systems that provide search and detection of a target, aiming a gun at a target and taking into account all parameters that affect the accuracy of firing.
On Soviet and foreign tanks until the 70s, the FCS did not exist, there was a set of optical and optoelectronic devices and sights with an unstabilized field of view and optical rangefinders that did not provide the necessary accuracy in measuring the range to the target. Gradually, devices with stabilization of the field of view and weapon stabilizers were introduced on the tanks, which allowed the gunner to keep the aiming mark and the gun on the target while the tank was moving. Before firing, the gunner had to determine a number of parameters affecting the accuracy of firing, and take them into account when firing.
Under such conditions, the accuracy of firing could not be high. Devices were required to ensure automatic recording of firing parameters, regardless of the skill of the gunner.
The complexity of the task was due to the too large set of parameters affecting firing and the inability to accurately take them into account by the gunner. The following groups of parameters affect the firing accuracy of a tank gun:
- ballistics of the cannon-projectile system, taking into account the meteorological conditions of firing;
- aiming accuracy;
- the accuracy of the alignment of the aiming line and the axis of the cannon bore;
- the kinematics of the movement of the tank and the target.
Ballistics for each type of projectile depends on the following characteristics:
- range to the target;
- the initial velocity of the projectile, determined by:
a) the temperature of the powder (charge) at the time of the shot;
b) wear of the bore of the gun barrel;
d) the quality of the gunpowder and compliance with the technical requirements of the cartridge case;
- the speed of the crosswind on the trajectory of the projectile;
- the speed of the longitudinal wind on the trajectory of the projectile;
- air pressure;
- air temperature;
- accuracy of conformity of the geometry of the projectile to the technical and technological documentation.
Aiming accuracy depends on the following characteristics:
- accuracy of stabilization of the aiming line vertically and horizontally;
- accuracy of image transmission of the field of view by optical, electronic and mechanical units of the sight from the entrance window to the eyepiece of the sight;
- optical characteristics of the sight.
Line of sight alignment accuracy and the axis of the bore of the gun barrel depends on:
- accuracy of gun stabilization in vertical and horizontal directions;
- accuracy of transmission of the position of the aiming line vertically in relation to the gun;
- displacement of the aiming line of the sight along the horizon relative to the axis of the cannon bore;
- bending of the gun barrel;
- the angular velocity of the vertical movement of the gun at the moment of the shot.
Kinematics of tank and target movement characterized by:
- radial and angular speed of the tank movement;
- radial and angular velocity of the target;
- the roll of the axis of the pins of the gun.
The ballistic characteristics of a tank gun are set by the firing table, which contains information about aiming angles, flight time to the target, and corrections for ballistic data correction depending on the target range and firing conditions.
Of all the characteristics, the accuracy of determining the range to the target has the greatest influence, therefore, for the OMS it was fundamentally important to use an accurate rangefinder, which appeared only with the introduction of laser rangefinders, which ensure the necessary accuracy regardless of the distance to the target.
From the set of characteristics that affect the accuracy of firing from a tank, it can be seen that the entire task can be solved only by a special computer. Of the two dozen characteristics, the required accuracy of some of them can be provided by the technical means of the sight and the weapon stabilizer (aiming accuracy, gun stabilization accuracy, the accuracy of transferring the aiming line in relation to the gun), and the rest can be determined by direct or indirect methods by the input information sensors and taken into account with the automatic generation and introduction of the corresponding corrections by the ballistic computer during firing.
The principle of operation of the tank ballistic computer is based on the formation in the memory of the computer of ballistic curves for each type of projectile by the method of piecewise linear approximation of the firing tables depending on the range, meteorological ballistic and kinematic conditions of movement of the tank and the target during firing.
Based on these data, the vertical aiming angle of the gun and the time of flight of the projectile to the target are calculated, according to which, taking into account the angular and radial speed of the tank and the target, the angle of lateral lead along the horizon is determined. The angles of aiming and lateral lead through the angle sensor of the position of the aiming line in relation to the gun are entered into the drives of the weapon stabilizer and the gun is mismatched with the aiming line at these angles. For this, a sight with independent vertical and horizontal field of view stabilization is needed.
Such a system for preparing and firing a shot provides the highest firing accuracy and elementary simple gunner's work. He only has to put the aiming mark on the target, measure the range to the target by pressing the button and keep the aiming mark on the target before firing a shot.
The introduction of a laser rangefinder and a tank ballistic computer on a tank led to revolutionary changes in the creation of a tank fire control system, which combined a sight, a laser rangefinder, a weapon stabilizer, a tank ballistic computer, and input information sensors into a single automated complex. The system provides automatic collection of information about firing conditions, calculation of aiming angles and lateral lead and their introduction into the gun and turret drives.
The first mechanical ballistic calculators (adding machines) appeared on American tanks and the M48 and M60. They were imperfect and unreliable, almost impossible to use. The gunner had to manually dial the range on the calculator and the calculated corrections were entered into the sight through a mechanical drive.
On the M60A1 (1965), the mechanical computer was replaced by an electronic analog-digital, and on the M60A2 (1971) modification, the M21 digital computer was installed, which automatically processes information about the distance from the laser rangefinder and input information sensors (speed and direction of movement of the tank and target, wind speed and direction, roll of the gun axle axis). Data on air temperature and pressure, charge temperature, gun barrel wear were entered manually.
The sight was with vertical and horizontal stabilization of the field of view dependent on the weapon stabilizer, and it was impossible to automatically enter the aiming and lead angles into the gun and turret drives.
A FLER-H digital ballistic computer was installed on the Leopard A4 tank (1974), which processes information from the laser rangefinder and input information sensors in the same way as on the M60A2 tank. On the Leopard 2 (1974) and M1 (1974) tanks, digital ballistic computers were used, operating on the same principle and with the same sets of input information sensors.
The first Soviet analog-digital TBV was introduced into the LMS on the first batches of the T-64B tank (1973) and subsequently replaced by a digital TBV 1V517 (1976). The ballistic computer automatically processed information from the laser rangefinder and input data sensors: a tank speed sensor, a turret position sensor in relation to the tank hull, a signal from the gunner's guidance panel (which was used to calculate the speed and direction of movement of the tank and the target), a crosswind speed sensor, roll sensor of the gun axle axle. Data on air temperature and pressure, charge temperature, gun barrel wear were entered manually.
The gunner's sight had independent stabilization of the field of view and the calculated TBV aiming and lateral lead angles were automatically entered into the gun and turret drives, keeping the gunner's sighting mark motionless.
Soviet tank ballistic computers were developed at the Branch Laboratory of the Moscow Institute of Electronic Technology (MIET) and introduced into mass production, since at that time there was no industry experience in the development of such devices. The ballistic computer 1В517 was the first Soviet digital ballistic computer for a tank, subsequently MIET developed and adopted a number of ballistic computers for all Soviet tanks and artillery. MIET also began the first studies on the creation of an integrated tank information and control system.
In the first generation MSA, a significant part of the characteristics that affect the accuracy of firing were manually entered into the TBV. With the improvement of the LMS, this problem was solved, almost all characteristics are now determined and entered into the TBV automatically.
The initial velocity of the projectile, depending on the wear of the bore of the gun barrel, the temperature and quality of the powder, began to be recorded by a device for determining the velocity of the projectile when flying out of the gun, installed on the barrel of the gun. With the help of this device, TBV automatically generates a correction for the change in projectile velocity from the tabulated one for the second and subsequent shots of this type of projectile.
The bend of the gun barrel, which changes depending on the heating of the barrel during tempo fire and even from sunlight, began to be taken into account by the bending meter, which is also installed on the gun barrel. The alignment of the aiming line of the sight along the horizon and the axis of the gun barrel bore began to be carried out not at a constant averaged range, but according to the calculated TBV range at the target location.
Air temperature and pressure, crosswind and longitudinal wind speed are automatically taken into account and entered into TBV using a complex atmosphere state sensor installed on the tank turret.
