Hi there, and welcome back. In order to further our understanding of any case, we need to select one or more disciplinary lenses. In this video, we will adopt one dominant disciplinary lens. We will also show you very briefly that other disciplines may add an additional angle for understanding the case as well. The dominant perspective for understanding the sinking of the Kursk, is that of a safety scientist. Safety Science covers a wide range of risks concerning humans and technology. For example, it studies safety at industrial plants, where people operate complicated machines or work with chemical substances. Safety Sciences always use various methods to indicate and calculate safety risks. It also aims to develop an optimized systems and processes to prevent, contain, or limit safety risk. In the case of the sinking of the Kursk, a safety scientist would look for risks, errors, and failures in both the design of the submarine and the safety culture on board of the ship. One of the methods used by safety scientists is that of a so-called fault tree, a fault tree is a method for risk analysis that helps us to identify, analyze, and visualize risk. It can be applied to a real incident to reveal its causes, or it can be used to think through a potential scenario for safety risk. Fault tree analysis explains how an underside state of event, or a system, called the top event came about as a result of a series of lower level events. In case of the Kursk, a fault tree helps us to reconstruct a chain of events that eventually led to the sinking of the submarine. A simplified fault tree of the Kursk could look like this. This fault tree demonstrates how the sinking of the submarine, the top event, can be explained by a series of lower level events. It all starts with the failures in the dummy torpedo, which enabled a chemical reaction. This, in turn, led to an explosion, the explosion blows off a torpedo door, which was not closed properly. Because of a failure in a bulkhead and the type of ventilation system on board of the submarine, the explosion rips through several compartments of the ship. This chain of events eventually leads to the flooding, and, consequently, the sinking of the submarine. Using this backward looking fault tree analysis, we can point out the root cause of this Kursk disaster, the exploding torpedo. Both the explosion itself, and the impact it had, can be explained as a mixture of technical, human, and organizational factors. Failures of welds, gaskets, bulkheads, and the ventilation system point at technical errors in the design and maintenance of the dummy torpedo and the submarine. The fact that the door of the torpedo tube was not closed properly, is a clear example of a human failure. Ideally, such failures would be prevented by means of safety protocols and checks, which is an organizational factor in play here. Using the disciplinary lens of safety science to understand the Kursk case, has led to a deeper understanding of the causes of this disaster. Fault tree analysis provided us with a clear and structured approach to organize the facts into a causal chain of events, focusing not only on the technical aspects, but also on the human and organizational aspects. Now let's find out how other disciplines would look at the Kursk. Unfortunately, our time is limited here, so we cannot discuss multiple disciplines in detail, but we would like to show you that different disciplines focus on entirely different aspects of the same case. For example, a chemist studying the Kursk would focus on the chemical reaction between the few HTP and kerosene in the torpedo triggering the explosion. In contrast, a radiation expert would focus on measuring the amount of radioactive release from the Kursk. Finally, a marine ecologist would study the impact on the marine ecosystem if there was any release of radioactive substance after this incident. Now that we've deepened our understanding of the case, let's move to the final phase, doing safety. By using the method of fault tree analysis from the discipline of safety science, we have unraveled a chain of cascading causal events explaining the sinking of the Kursk. We've also seen that other sciences might ask radically different questions about the same case. Note, however, that all of these sciences focus on the safety aspects of this incident. The sinking of the Kursk was the result of a chain of terrible accidental events, making it a safety case. What is important to stress here, is that complex safety cases can only be unraveled and understood deeply when applying multiple relevant disciplinary lenses. Now, let's wrap up. We analyzed the safety case of the Kursk by applying the three step model of explore, understand, and do. In the next video, our colleague Professor Edwin Walker will demonstrate the analysis of a security case. He will assess the Boston bombings in the USA in 2005. These were clearly the result of human intentional behavior, therefore the Boston bombings are a clear example of a security case. Thank you for watching this video, and see you back soon.