Surface to Surface Missiles
Surface to Surface Missiles [SSM] are common ground-to-ground missile, though these may also be launched from a ship to another ship. Underwater weapons which are launched from a submarine also come under this class of missiles. Missiles which travel a distance of about 50 to 100 km are designated as short-range missiles. Those with a range of 100 to 1500 km are called medium-range missiles and missiles having a range upto 5000 km are said to be intermediate-range missiles. ICBMs belong to the class of long-range missiles which can travel a distance of 12000 km.
By definition a ballistic missile is one which covers a major part of its range outside the atmosphere where the only external force acting on the missile is the gravitational force of Earth, while the cruise missile is one which travels its entire range in the atmosphere at a nearly constant height and speed. However, a missile could have a combination of the two also where a missile could cover part of the flight in ballistic mode and later a terminal portion in cruise mode.
A liquid propellant system has many advantages. Liquid propellant missiles have a flightdemonstrated record for accurate impulse control. The manufacture of components and the production of liquid propellants involve standard industrial capabilities. On the other hand, a solid propellant rocket motor having the same range capability could be designed with significantly less weight and length. The solid propellant rocket motors consist basically of only four components: the motor case, the nozzle assembly, the propellant grain, and the igniter. Thus, the number of components attributable to a solid propellant motor is substantially less than the number required for a liquid system.
This reduction in components reduces complexity, and thus a solid propellant system has a greater inherent reliability. In addition, the use of solid propellants considerably simplifies the supply system. There is no separate element in the supply line that is associated with the propulsion system. The propellant travels as part of the missile. In contrast, the supply of oxidizer, fuel, and spare propulsion components for a liquid system requires complex storage, handling, and shipping facilities from the point of manufacture to the battle front.
Finally, because the propellant is already loaded in the solid rocket, it places no demand on the tactical organization. This organization, when handling liquid propellants, is forced to form a continuation of the supply line. Therefore, considerable checkout equipment and a large number of highly trained personnel must be devoted to testing and fueling before the liquid propulsion system is in a condition comparable to that of the solid rocket as delivered.
The success of surface-to-surface weapon systems depends on a reliable and accurate method for controlling range. There are several basic considerations involved in the design of a range-control system for any surfaceto-surface missile. One major problem in the development of ballistic missiles has been finding a suitable range guidance system for substantially eliminating target error. This may be solved by using either a thrust-termination system or a dragbrake system. Although the addition of dragbrakes to a missile presents serious aerodynamic, structural, and mechanical design problems, it is believed that these problems can be solved with less difliculty than would be required for a thrust-termination system.
A successful defense of a country depends preponderantly upon an efficient defense against enemy tanks. It is therefore very valuable to the defense of a country to be able to accurately combat tanks, and in particular large tank units, while they are still at a considerably distance from and before their entry into the direct combat zone.
Surface targets against which fire-control systems are useful include movable ground targets, such as tanks and rocket-launching sites, stationary ground targets, and surface targets at sea, etc. The missile launching sites are surface based and are preferably portable and for example vehicular mounted. By an indirect ballistic trajectory, it is meant as is known, the relatively higher trajectory of the available low and high missile trajectories for a particular target range.
For rocket artillery, the requirements have changed existentially in recent decades. Were previously under the national defense, the soft and semi-rigid surface targets in focus, so today dominates the demand must be avoided collateral damage and to be highly flexible in terms of the ability to transfer different payloads. The shipment of different payloads various rocket artillery missiles are controlled to the target and detonated nearby, at the destination, or shortly after a premium. According properties of a payload are programmed into a fire control system, so that it can fire the missile according to the payloads targeted.
The employment of live or combat projectiles having an automatic homing and steering device effective during the steep descent of their ballistic trajectory to automatically steer the live projectile to the target. This will improve the accuracy of the projectile and permit the projectile to be fired very effectively at great distances.
One type of guidance system which integrates well with both warhead requirements and the general characteristics of a ballistic missile is the so-called vernier type of control. A vernier type system is one in which all effects that could cause dispersion from the target are cancelled, either as early as they can be detected or as shortly thereafter as is practical. In a rocket-powered missile, essentially all of the large dispersion effects occur during the burning period which is a relatively small fraction of the total flight time. If a coarse-guidance system which operates either during burning or shortly thereafter is used to overcome these large dispersion effects, any further guidance need be only of a fine or vernier nature. This vernier guidance needs to have only the capability of overcoming the relatively small disturbances which occur later in flight in order to provide the final accuracy.
It is a characteristic of the ballistic type of trajectories to be used by such surface-to-surface missiles that during and shortly after the burning period the range is highly sensitive to axial acceleration, whereas late in flight it is sensitive to pitch acceleration and quite insensitive to axial acceleration.
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