Computational models for anti-air and anti-submarine warfare simulation

Resumen Modelos computacionales para simulación de guerra antiaérea y antisubmarina Date Received: December 2nd, 2010 Fecha de recepción: 2 de Diciembre de 2010 Date Accepted: March 6th, 2012 Fecha de aceptación: 6 de Marzo de 2012 Computational models for anti-air and antisubmarine warfare simulation 1 Corporación de Ciencia y Tecnología para el Desarrollo de la Industria Naval, Marítima y Fluvial COTECMAR. e-mail: gustavoperezv@gmail.com 2 Corporación de Ciencia y Tecnología para el Desarrollo de la Industria Naval, Marítima y Fluvial COTECMAR. e-mail: smarrugo@cotecmar.com 3 Corporación de Ciencia y Tecnología para el Desarrollo de la Industria Naval, Marítima y Fluvial COTECMAR. e-mail: jmgomez@cotecmar.com Ship Science & Technology Vol. 6 n.° 12 (29-40) January 2013 Cartagena (Colombia) 30 Simulation tools allow modeling phenomena or events of different complexity and are used as support tools in the decision making process because they base their predictions on mathematical methods that yield results that are very close to the real ones. In fact, simulation can be defined as the act of imitating a real system, representing certain characteristics or its behavior. This document seeks to describe the process of generating and simulating computational models of antisubmarine (ASW) and anti-aircraft warfare (AAW) by using discrete event simulation. The aim of the development of such models is to use them as tools for conceptual exploration of future units to evaluate the effectiveness of different weapons system configurations considered at this stage. That means that these models will be other tools to optimize processes of conceptual design of units afloat. The methodology used to develop the models begins with the selection of operational situations to simulate, then it is necessary to identify the different threats, weapons, and sensors and their possible combinations within the selected scenario; this is introduced to the selected simulation tool and results obtained will undergo statistical processing to successfully analyze them. Some key concepts related to this topic are presented to provide tools to improve understanding of the paper. Discrete Event Simulation Discrete event simulation is a computer technique for dynamic systems modeling. In this type of simulation, events are generated and managed over time using an event queue ordered by the simulation time in which events must occur, thus, the simulator can read the queue and trigger new events. Operational situation (OPSIT) Operational situations are the scenarios used as base for evaluating different configurations of weapons, sensors, and threats for both ASW and AAW. To select OPSITs that will be simulated, it was necessary to gather a group of experts in ASW, which comprised ASW officers and petty officers from ARC Almirante Padilla type frigates of the Colombian Navy and for a submarine warfare expert from the Colombian submarine fleet. For AAW, it was possible to obtain technical advice from an officer from DARET and an officer who is studying in the Naval Postgraduate School (NPS). For ASW the publication MXP-1 (D) (Navy) (Air) of the U.S. Navy (Multi-National Submarine and Anti-Submarine Exercise Manual) was taken as reference from which two operational scenarios were selected among several proposed. For ASW, the OPSITs selected are: 1. Port leaving with submarine opposition. (Similar to Casex C-7) 2. Coordinated submarine search in an area. The configuration of each OPSIT depends on the specific need to be evaluated. For cases presented in this document, the units involved in the first OPSIT are: two ships (with Helicopters), one tanker (main body), and one submarine. In the second OPSIT had: one ship (with helicopter) and one submarine. The first OPSIT mission is the main body protection and neutralization of the threat, while for the second OPSIT, the only objective is to neutralize the threat. Fig. 1 provides an overview of the AAW OPSIT, showing enemy aircraft in red and the unit attacked is in the center in blue. In this case, the unit’s Introduction OPSIT Selection and Description Conceptual Framework Ship Science & Technology Vol. 6 n.° 12 (29-40) January 2013 Cartagena (Colombia) Pérez, Marrugo, Gómez

Simulation tools allow modeling phenomena or events of different complexity and are used as support tools in the decision making process because they base their predictions on mathematical methods that yield results that are very close to the real ones.In fact, simulation can be defined as the act of imitating a real system, representing certain characteristics or its behavior.
This document seeks to describe the process of generating and simulating computational models of antisubmarine (ASW) and anti-aircraft warfare (AAW) by using discrete event simulation.The aim of the development of such models is to use them as tools for conceptual exploration of future units to evaluate the effectiveness of different weapons system configurations considered at this stage.That means that these models will be other tools to optimize processes of conceptual design of units afloat.
The methodology used to develop the models begins with the selection of operational situations to simulate, then it is necessary to identify the different threats, weapons, and sensors and their possible combinations within the selected scenario; this is introduced to the selected simulation tool and results obtained will undergo statistical processing to successfully analyze them.
Some key concepts related to this topic are presented to provide tools to improve understanding of the paper.

Discrete Event Simulation
Discrete event simulation is a computer technique for dynamic systems modeling.In this type of simulation, events are generated and managed over time using an event queue ordered by the simulation time in which events must occur, thus, the simulator can read the queue and trigger new events.

Operational situation (OPSIT)
Operational situations are the scenarios used as base for evaluating different configurations of weapons, sensors, and threats for both ASW and AAW.
To select OPSITs that will be simulated, it was necessary to gather a group of experts in ASW, which comprised ASW officers and petty officers from ARC Almirante Padilla type frigates of the Colombian Navy and for a submarine warfare expert from the Colombian submarine fleet.For AAW, it was possible to obtain technical advice from an officer from DARET and an officer who is studying in the Naval Postgraduate School (NPS).
For ASW the publication MXP-1 (D) (Navy) (Air) of the U.S. Navy (Multi-National Submarine and Anti-Submarine Exercise Manual) was taken as reference from which two operational scenarios were selected among several proposed.For ASW, the OPSITs selected are: 1. Port leaving with submarine opposition.
(Similar to Casex C-7) 2. Coordinated submarine search in an area.
The configuration of each OPSIT depends on the specific need to be evaluated.For cases presented in this document, the units involved in the first OPSIT are: two ships (with Helicopters), one tanker (main body), and one submarine.
In the second OPSIT had: one ship (with helicopter) and one submarine.
The first OPSIT mission is the main body protection and neutralization of the threat, while for the second OPSIT, the only objective is to neutralize the threat.For AAW, the OPSIT was basically modeled as missile air defense, where a ship is the target of a coordinated enemy aircraft attack, using airsurface missiles (ASM).
In order to have metrics to evaluate each mission, some requirements have been designed to determine its success, based on the calculation of measures of performance (MOP) and a measure of effectiveness (MOE) for each OPSIT.
The measure of effectiveness is defined by the weighted sum of the measures of performance established; that is: Where W 1 , W 2 , W n are factors representing the importance of each MOP.For ASW, these values were determined from surveys made in that regard to two of the commanders of Almirante Padilla type frigates of the Colombian navy.
In the ASW OPSIT, the MOPs are: The AAW OPSIT takes into account three possible threats.Bear in mind that for this particular case, ASM missiles and not the planes are assumed as direct threats, given the assumption that a plane is not going to approach within the range of the ship guns. 1 are some of the features of the threats selected.

Mission Evaluation Threat Characterization
(2) Both ASW OPSITs take into account two possible threats.The general characteristics of the two submarines, which are relevant to the appropriate development of the models, are presented in Table 2.
It is worth stating that the selection of the threat and its operating characteristics are subject to change, depending on the needs of the situation.
For the ASW OPSITs, the technological weapons and sensors options taken into account are presented in Table 3.
For the AAW OPSIT, configurations of the ship weapons and sensors that will be evaluated in the simulation are shown in Table 4 and technological options taken into account appear in Table 5.To make the OPSITs models in the simulation tool it was necessary to develop a logic diagram to have greater clarity on the logical relationships among the different processes occurring in each.Fig. 2 presents one example.
The general scheme for the development of simulation models is presented in Fig. 3.
Endogenous variables that constitute the inputs or the simulation model are on the left side of Fig. 3; the state variables, which condition the simulation process, are on the central part, and -finally -the exogenous variables as result of the process are in the right side of the figure.
Then, the modeling process begins in the simulator.An example of the blocks created in the simulator is presented in Fig. 4 (see pag. 36).
For the AAW OPSIT, the model starts with the creation of a couple of objects, which will be necessary for assigned properties, these properties are read from an Excel spreadsheet that has all the values needed for the model to function.Once read, these properties are stored in the object in form of attributes.

Simulation Models
Ship  When each object has its attributes, it is necessary to calculate whether threats are within the detection range of each sensor.If threats are within range, the sensor determines the distance and sends the information to a queue of weapons that will assign the appropriate defense (defense of barriers concept); otherwise, the sensor will continue sweeping the area until achieving detection.
In general, the AAW model block presented in Fig. 4 was used to simulate the dynamic approach (simulation sampling) of enemy missiles fired.When these missiles are within range of the sensors, detection occurs.This detection activates a weapons assignment queue, which is another object or event in the simulation.
Likewise, all OPSIT threats were modeled in the simulator.The activation of each threat constitutes an event in the simulation.For the AAW OPSIT, the specific threats are ASM missiles; therefore, these were modeled in the simulator, as shown in Fig. 5.
For the case shown in Fig. 5, the simulation begins with the activation of each threat in the Excel spreadsheet.The model loads the properties of each missile, which are read from the Excel spreadsheet that has all the values needed to run the simulation.Once the properties have been read, they are stored in the object (an object for each threat) in the form of attributes.
Subsequently, the algorithm that allows: • Calculate the path of the trajectory of the missile's towards the vessel.• Activate the missile radar when is located at a specified distance from the ship.Finally, the algorithm receives from the weapons queue the weapons assignment, the missile deactivation order, in case this was shot down by the weapon system.
To define the configurations of the experiments to be run in the discrete event simulator, it was necessary to perform an experimental design for which we used the JMP software, a tool for data statistical analysis.
Basically, the process consists of introducing the variable names that will result from the experiments, which in this case are the MOP raised on initial sections for each OPSIT and, factors that intervene in the experiments, which in this case are the different sensors and weapons selected for evaluation.
Once we have the necessary data, the experimental design is generated and a list of data is obtained for each experiment.Each experiment is run the necessary number of times to obtain acceptable statistical data.
For the first ASW OPSIT, the resulting design of experiments is 18, which means that it is possible to evaluate 18 possible scenarios.For each of them, Table 6 presents its measures of performance.In the second ASW OPSIT, the software showed that 30 experiments would be needed.The results of MOP for this scenario are presented in Table 7.
Finally, for the AAW OPSIT, six experiments were made, considering the two specific vessel configurations of sensors and weapons that were shown in Table 5, only varying the threat.
The results for this MOP scenario are shown in Table 8.
For these OPSITs, the reliability of the models simulated was evaluated in the statistical analysis software and the relative importance of each variable in each configuration was verified.The analysis of variance results provided by the software allows having a high level of confidence on the statistical model because correlation coefficients were obtained between 0.88 and 0.99, meaning that the models in the discrete event simulator produce consistent data.

Experimental Design and Results
Considering the results presented in the Pareto plots, similar to what is presented in Fig. 6 for both ASW OPSITs, it was possible to note that at least 45% of the variability of the model depends on the presence or absence of helicopters.Also, it was clear the relevance the VDS/TAS-type sensor has; in fact, at least 18% of the variability of the model depended on the lack of these sensors on the platform.
The results obtained from the AAW simulation model, for characteristics raised in each experiment, show that configuration 1 has the best performance, given that it can attend all missiles simultaneously.This is a significant advantage, given that it reduces weapons reallocating dependence.Similarly, the weapons range of configuration 1 is higher than the weapons range of the other configuration, allowing saving time during the defense process.
Regarding threats, missile 2 showed that because of its high speed, the probability of survival of the platform to which it is confronted is greatly reduced and, in some cases, weapons systems are completely ineffective against this threat, given that the highest probability of survival obtained at the end of the simulations does not exceed 20% in any case.
With the tactical situations presented in the paper, it was possible to evaluate the relationships between weapons and sensors systems, which allow inferring that with a common configuration of weapons and sensors, it will be possible to evaluate tactical situations that ultimately lead to a study of doctrine or tactical procedures, using these same models.
The models structured have high flexibility to adapt to any type of analysis; these could be about threats or configuration of the platforms.Excel interfaces facilitate data input process and final statistics.Also, it was possible to observe, through the experimentation process, that a strong relationship exists between the sensor and weapon selected, i.e., it is not possible to obtain the expected results when the features of one of the two exceeds the other because it is not significant to have a sensor with a long range, if the weapon used cannot neutralize the threat detected.
Finally, it is important to note that the results obtained from the simulation of these models allow validating these methods; however, these are not convincing to make decisions on what is the best configuration because too much of the data or characterizations of the weapons, sensors, and threats provided to the model were speculative due to the absence of information available in the market.This implies that upon making the analysis of real equipment that could be installed in future ships; it is necessary for sensors and weapons manufacturers to provide the necessary information to perform an analysis that could help to conclude about the best configuration.

Fig. 1
Fig.1provides an overview of the AAW OPSIT, showing enemy aircraft in red and the unit attacked is in the center in blue.In this case, the unit's Tanker survival probability • MOP 2 = Survival probability of the ships • MOP 3 = Threat neutralizing probability And the MOE of this OPSIT is: For the second ASW OPSIT, the MOPs are: • MOP 1 = Survival probability of ships • MOP 2 = Threat neutralizing probability • MOP 3 = Time to detect the submarine And the MOE of this OPSIT is: Finally, for the AAW OPSIT, the MOP is equal to the MOE; due to this, only one MOP will be evaluated: • MOP1 = Survival probability of ships And the MOE is:

Table 4 .
Ship configuration options

Table 6 .
ASW OPSIT1 Experiment Design Results