Method for predicting the operational capability of ship systems on a watercraft after enemy action

Abstract

The present invention relates to a method for predicting the operational capability of ship systems on a watercraft after enemy action, wherein the method is carried out in three steps, wherein a ship model for the watercraft is specified, wherein the ship model is specified functional chains with the locations of components of the functional chains, wherein each functional chain has components, wherein at least one damage event and a location of the damage event are specified.

Description

[0001] The invention relates to a method for predicting the operational capability of the ship's systems on a watercraft after enemy action.

[0002] The design of naval vessels must meet various requirements. These include assessing the impact of attacks and ensuring the (partial) functionality of the vessel afterward. More complex damage scenarios include explosions, for example, from missiles that have penetrated the ship's interior or from mines or torpedoes beneath the vessel. While immediate (mechanical) consequences, such as flooding, can be simulated relatively easily, considering the impact on the entire ship system is difficult. Many ship systems are highly interconnected or branched, so damage in one area can lead to failures in entirely different areas. For example, damage to a hydraulic system can prevent other systems connected to the same hydraulic system from operating.At the same time, explosions inside the ship, particularly those caused by gas blast and fragmentation, are extremely difficult to predict accurately. For example, the precise impact points of fragments are crucial for the damage pattern, but these cannot be reliably predicted. Therefore, it is impossible to perform a simulation of the entire naval vessel and thus obtain an exact description of the damage pattern. Consequently, simulating the impact of component failure, such as that caused by an explosion, on other, often remote, systems is extremely challenging. The goal is to identify weak points in the design process early on and adjust the design accordingly to ensure that essential ship systems remain reliably operational during or after a damage event.

[0003] This involves defining three essential survivability requirements, which must be met depending on the level of enemy action. The lowest requirement after a significant enemy attack is buoyancy. This ensures the crew's survival and enables rescue and evacuation. In cases of less severe enemy action, an escape route is preferred, meaning at least a rudimentary propulsion system with steering capabilities. This allows for a return home and thus rescue under one's own power. In cases of even less severe enemy action, a defensive capability should also be present to counter further enemy action, such as the functionality of a close-in weapon system. This, of course, further increases survivability.Depending on the required state condition, the functionality of different functional chains must be guaranteed.

[0004] The object of the invention is to provide a method for the most precise possible prediction of damage and thus to enable the development of the safest possible ship design.

[0005] This problem is solved by the method with the features specified in claim 1. Advantageous further developments result from the dependent claims and the following description.

[0006] The method according to the invention serves to assess the operational capability of ship systems on a vessel after enemy action. Enemy action within the meaning of the invention includes, for example, a grenade or rocket penetrating the ship's interior, particularly with an explosion inside the ship, or underwater detonations, for example, of mines or torpedoes. However, enemy action can also include, for example, and particularly in asymmetric threat scenarios, shelling with small-caliber ammunition, especially small arms fire, or shelling with armor-piercing weapons, for example, anti-tank weapons, or the use of improvised explosive and incendiary devices, for example, by means of drones. The assessment can be carried out with varying degrees of accuracy.Such enemy action can only be considered in a few exemplary scenarios, and, for example, fragmentation and fragment flight can only be determined using examples. Therefore, an exact prediction of damage occurrence is only possible to a limited extent. At the same time, the assessment can be simplified very quickly if, for example, no relevant system components are affected (in the positive case) or at least one critical system has completely failed (in the negative case). In both of these cases, a more detailed analysis beyond an initial estimate is not necessary.

[0007] The procedure is carried out in three steps. A ship model is provided for the vessel. This model specifically defines the compartments and the components located within them. The failure of different components has varying effects on the survivability of the ship and its crew. Therefore, there are functional chains that are permitted to fail and those that must remain functional. This allows for an assessment of which damages from enemy action are acceptable and to what extent, meaning that the overall survivability is either not affected or only acceptably impaired. This also defines and specifies the maximum acceptable impact of enemy action. The ship model is defined by functional chains and the locations of their components. Functional chains are components that belong together to perform a specific function. For example, the propulsion system could be a functional chain.Obviously, the functional chain includes the engine, shaft, and propeller. However, this doesn't complete the functional chain. In the case of an internal combustion engine, the fuel tank, fuel line, and fuel pump would also be required. The fuel pump needs to be driven, for example, electrically. Even this simple and obvious example demonstrates that functional chains are comparatively complex and often overlapping. Furthermore, many functional chains are partially or fully redundant. For example, if an electrical circuit is designed as a ring circuit, damage to the ring circuit at one point might not lead to a complete failure, provided a short circuit can be avoided or the damaged section can be isolated. Therefore, it is essential to represent and specify these functional chains clearly and completely, including all components.However, there may be functionalities that are considered entirely unnecessary and therefore do not need to be represented in the functional chains. An entertainment system could be an example. Each functional chain contains the components used for its functionality, such as, in the case mentioned above, at least an engine, shaft, propeller, fuel tank, fuel line, and fuel pump. One or more components may be redundant, for example, on both the port and starboard sides. In addition to the arrangement of the components (in which space), their functional relationships (especially with regard to redundancies) are also depicted in the functional chain. Thus, all components assigned to a functional chain are identified, and their arrangement on the ship is clearly defined.At least one damage event and its location are specified. This corresponds to the requirements the naval vessel is expected to withstand. The damage event could, for example, be a missile impact in area XYZ or a collision with a mine at location ABC.

[0008] As a first step, an empirical calculation of the impact of the damaging event is performed using a damage radius model, thereby identifying the affected areas. This first step thus serves to make an initial spatial assessment of the impact, thereby defining the area to be examined more closely and minimizing the effort required for the subsequent step.

[0009] The damage radius model can result in very different sizes of damage zones. For example, while gunfire has a very limited local impact, even a very small hole in the hull can cause a list due to the water entering through it, which then affects all components of the vessel. Furthermore, a warhead exploding inside the vessel, for example, has a pressure effect, a fragmentation effect, and a shock effect on the adjacent ship structure. Both can have different damage zones. Therefore, even a single damaging event can have different damage zones for different types of damage.

[0010] In a second step, a numerical calculation of the damage effect in the damaged areas is performed using the finite element method. This allows for a more precise analysis. By limiting the analysis to the simplified damage areas, the effort can be reduced to a minimum. At the same time, the accuracy is significantly improved compared to the previous rough estimates, so that, for example, the effects of a pressure wave, the impact of flying debris, and the shock effect can be considered separately, especially with regard to their impact on the components located in the damaged area. Furthermore, separating the first and second steps allows the two steps to be performed in different environments, particularly in different software programs. This separation also results in a significant increase in efficiency.

[0011] In a third step, a vulnerability analysis of the functional chains is conducted based on the components located in the damaged areas and the impact of the damage. As a first approach, the failure of each affected component can be assumed. Then, the impact of the component's failure on the functional chains in which the component is involved must be considered. For example, if we consider the propulsion functional chain as described above, the failure of the propeller shaft (on a ship with only one propeller) will lead to the complete failure of the propulsion functional chain. Damage to a fuel tank, on the other hand, will typically only affect the range, since such tanks are usually provided redundantly on the port and starboard sides for trim reasons.

[0012] Different functional chains have different significance for the ship and fulfill different, sometimes overlapping (redundant) tasks. Therefore, it is essential to consider which functional chains are impaired or have failed. Consequently, the ship model also incorporates the interaction of these functional chains. Important systems, such as the rudder control, are preferably designed with redundancy. This allows the ship to have two separate functional chains, for example, for rudder control. In the event of damage, the failure of one of the two redundant functional chains may then be acceptable. On the other hand, there may be functional chains that are so essential that the failure of just one system, one functional chain, negates the ship's survivability.For example, severe damage to the ship's hull, which destroys its buoyancy, would be considered unacceptable on its own and without further interaction with other functional chains.

[0013] Furthermore, functional chains can be prioritized differently. For example, the loss of certain functional chains may be acceptable in some scenarios but not in others. In a lower threat situation, such as an attack by a much weaker adversary, the failure of only a few functional chains might be acceptable, whereas in a high-threat situation, such as from a superior adversary, the failure of many functional chains might be acceptable, for example, to allow for the evacuation of the crew before abandoning the ship. Thus, there is a direct, yet very complex, interaction between the damage event and the functional chains that are acceptably impaired. In addition, due to redundancies or overlapping functionalities, the acceptance of the failure is considered in the context of all functional chains as a whole.

[0014] Thus, different failure probabilities exist for different functional chains depending on the type of damage event. Different damage events can be grouped into different damage classes. Preferably, failure classes are then defined that specify tolerable failure rates in the functional chains corresponding to the damage classes.

[0015] In a further embodiment of the invention, the functional chains are prioritized according to their importance. For a failure event, the failure can then be easily defined based on the highest priority chain that is permitted to fail. In a further development, it can be defined that the probability of failure may be inversely proportional to the prioritization of a functional chain. Thus, the probability of failure of the highest-priority functional chain must be the lowest.

[0016] In a further embodiment of the invention, after the first or second step, a further damage event can result from the damage radius model or the numerical calculation of the damage effect, for example, through the ignition of fuel or ammunition. Accordingly, the calculation according to step 1 and step 2 can then be performed again for this secondary damage event, and subsequently, provided this does not trigger a further damage event, in the third step the vulnerability analysis of the functional chains is determined based on the components arranged in the damage areas and the damage effect resulting from the combination of the original and the subsequent damage event generated by it.

[0017] It is therefore possible, with manageable effort, to represent the damage pattern much more precisely and thus to design the watercraft as a whole to be smaller and lighter, and therefore faster and more maneuverable and ultimately more survivable, since, for example, unnecessary redundancies can be avoided.

[0018] In a further embodiment of the invention, the functional chains are defined room by room. This simplification considers all components in a room as having failed if that room is affected. Particularly in the case of splintering, it is practically impossible to predict which components will actually be damaged and to what extent. It is therefore reasonable to assume that all components will fail; in reality, this can only be more favorable. For example, a threshold value can be defined for pressure, temperature, or shock. Only when this threshold value is exceeded are the components considered to have failed.

[0019] In a further embodiment of the invention, at least one limit value for the damaging effect is defined for each component of the functional chains, which defines a component failure. For example, in the event of shock, many assemblies are already designed for a certain shock resistance. If the shock load remains below the limit value, i.e., below the value for which the component is designed, the component is still considered intact. This is also very easy to understand if, for example, water ingress occurs due to enemy action and the watercraft lists. Since a considerable list is normal even during normal operation of a watercraft, most components are designed for a certain degree of tilt anyway. If this tilt exceeds the limit value, the component is also considered to have failed.

[0020] In a further embodiment of the invention, an individual limit value is defined for each component of the functional chains for each type of damaging effect, such as shock, fragmentation, pressure wave, temperature, and tilt, which defines a component failure. This allows for consideration of the very different susceptibility to various damaging effects. For example, a hydraulic system is likely to be more susceptible to fragmentation, whereas fuel is probably more sensitive to heat than to fragments. In particular, all components in a room whose limit value is below the calculated value for that type of damage can thus be considered defective. Naturally, with several different limit values ​​for different types of damage, exceeding a single limit value is sufficient for a component to be considered defective.

[0021] In a further embodiment of the invention, the three steps are performed using different programs. This allows for optimal processing by performing the three-step division and thus separate, step-by-step analysis in an environment optimal for each step.

[0022] A key aspect of using the method according to the invention is to question the arrangement of the components of a functional chain and, if necessary, to modify functional chains by rearranging components and then, if necessary, repeating the method. For example, if it is discovered during the execution of the method that a critical functional chain is damaged in a critical event, the components of this functional chain can either be relocated to protected areas, such as those further inward, or additional redundancy can be created. The aim is thus to ensure the ship's survivability without creating unnecessary redundancies and ultimately to save weight and space.

Claims

[1] Method for estimating the operational capability of the ship systems on a watercraft after enemy action, wherein the method is carried out in three steps, wherein a ship model is specified for the watercraft, wherein the ship model specifies functional chains with the locations of components of the functional chains, wherein each functional chain has components, wherein at least one damage event and a location of the damage event is specified, whereby in a first step an empirical calculation of the impact of the damage event is carried out using a damage radius model and thus damage areas are identified, whereby In a second step, a numerical calculation of the damage effect in the damaged areas is carried out based on the finite element method, whereby In a third step, a vulnerability analysis of the functional chains is determined based on the components located in the damage areas and the damage effect. [2] Method according to claim 1, characterized by that the functional chains are defined space-wise. [3] Method according to any of the preceding claims, characterized by , that for each component of the functional chains at least one limit value for the damaging effect is defined, which defines a failure of the component. [4] Method according to claim 3, characterized by , that for each component of the functional chains a limit value is set for each type of damaging effect, for example shock, splintering, pressure wave and tilting, which defines a failure of the component. [5] Method according to any of the foregoing claims, characterized by that the three steps are carried out using different programs.