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- Dynamics of a gyrostat satellite with the vector of gyrostatic moment tangent to the orbital planePublication . Morais, Renato; Santos, Luis; Silva, André; Melício, RuiIn this paper, a gyrostat satellite in a circular orbit with its gyrostatic moment tangent to the orbital plane and collinear with the orbital speed is studied regarding its equilibria, bifurcation of equilibria, and asymptotic stability conditions. In the general case, where any gyrostat angular momentum is aligned with any of the orbital coordinate frames, interesting results arose regarding its equilibria bifurcation regarding conditions near to the ones presented in this paper, namely equilibria regions outside their main regions near to the orbital plane tangent. For equilibria and bifurcation of equilibria, a symbolic-numerical method is used to obtain the polynomial equations in function of non-dimensional parameters whose roots are equivalent to the number of equilibria positions. For the asymptotic stability, the results are tested using the Lyapunov stability theory scheme.
- Asteroids Deep Ocean Impact and the ShortTerm Consequences to the Portuguese Territory and PopulationPublication . Morais, Renato Henriques; Silva, André Resende Rodrigues da; Santos, Luís Filipe Ferreira MarquesThe impact of asteroids is an established global threat. Every location on Earth has a similar, a priori likelihood of an asteroid impact, which is limited by the current humankind’s knowledge. As Earth’s surface is mostly water, a water asteroid impact is twice as likely as a ground impact. Ocean impacts are naturally more distant from populated areas but can still pose a significant threat. Impact events have a low probability but high consequences making them a hard concept to the public as such happenings do not occur in the daytoday life. Even though asteroid impacts have been proven to be lethal in the past, increasing public awareness to this hazard is still needed. The potential global devastation obliges mitigation measures that would come naturally with the awareness. In this dissertation, an ocean asteroid impact was assumed and the immediate impact effects were assessed for the Portuguese municipalities. The impact location was set in a midpoint between mainland Portugal, Azores and Madeira islands. All asteroids were assumed to impact the Earth at a 45 degrees angle. The study covers seismic shaking, overpressure, ejecta deposit, thermal radiation and tsunami waves; as well as the possible global implications on Earth, in terms of orbit disturbance, change in rotation period, axis tilt variation, and lost mass. The vulnerabilities and casualties for each individual municipality and each impact effect were also estimated. In an asteroid ocean impact far from coastal regions, the ejecta deposit and seismic shaking are the less significant effects and can be disregarded. The thermal radiation has a small reach and can be disregarded for minor asteroids. The shock wave is experienced for all three impacts, but its damage is mostly structural. The tsunami is by far the biggest threat in an asteroid impact on the ocean.
- Short-Term Consequences of Asteroid Impacts into the Ocean: A Portuguese Case StudyPublication . Morais, Renato; Santos, Luís; Silva, A. R. R.; Melício, RuiAsteroid impacts are a proven global threat, meaning that any location on Earth might be a subject to their consequences. Such collisions are not likely in any person’s lifetime, but their aftermath could be catastrophic. As Earth’s surface is mostly water, a water impact is more probable than a ground impact, and tsunami waves could pose a significant threat. This study expands the knowledge about asteroid impacts in the ocean and their regional environmental consequences. Three asteroids were assumed to impact the Earth: (1) the Apophis asteroid, a 370 m wide asteroid, (2) a 204 m in diameter asteroid representative of the average impactor on the near-Earth objects, and (3) a 5 km in diameter asteroid. We evaluated the consequences of all impacts for a specific case study, where the chosen impact location was the midpoint between Portugal’s mainland, Azores, and Madeira Islands. The cratering process, generated seismic shaking, overpressure, ejected material, induced thermal radiation, and tsunami waves were assessed, along with the global effects. The overpressure mainly causes structural damage. The thermal radiation can be devastating but has a short reach. The tsunami is undoubtedly the most far-reaching and threatening effect of an asteroid impact in the ocean.
- Hypothetical Apophis deep ocean impact - Energy analysisPublication . Morais, Renato; Santos, Luís; Silva, André; Melício, RuiThis paper models a hypothetical Apophis asteroid impact on an chosen deep ocean point on the globe. To assess the potential vulnerabilities of an exposed coast population, the impact effects were assessed as a function of the distance to the asteroid's impact point as well as altitude for the tsunami case. All the tools and models used are valid and can be implemented for any other point on the Earth's surface. The impact modelling includes the analysis of cratering formation, generated earthquake, overpressure, ejected material, generated thermal radiation and tsunami, as well as the global geophysical effects of the impact. The vulnerability models entail best, expected, and worst case scenarios, which allows a reasonable range of results. As the impact occurs in the ocean, and if its a great distance away from populated areas, the population is safeguarded from most of the impact effects. The tsunami is undoubtedly the most far-reaching and threatening impact effect from an asteroid impact on the ocean.
- Asteroid Impacts on the Ocean and Its Short-term Consequences: a Portuguese Case StudyPublication . Morais, Renato; Santos, Luís; Silva, A. R. R.; Melício, RuiAny location on Earth might be considered a subject to an asteroid impact because, as previous studies show, they are a proven global threat. the consequences of a collision could be catastrophic, even though such events are rare to occur in a person’s lifetime. Tsunami waves can constitute the greatest threat as the Earth’s surface is mostly water, making the probability of a water impact greater than a ground impact. This work expands the knowledge about asteroid impacts on the ocean and their short-term regional consequences. Three asteroids were assumed to impact the Earth: (1) the 2015 JJ asteroid with a 130 m diameter, (2) the 2020 FA5 asteroid with a 210 m diameter, and (3) the Apophis asteroid, a 370 m wide asteroid. We evaluated the consequences of all impacts, at a 45 degree angle, for a specific case study, where the chosen impact location was the midpoint between Portugal’s mainland, Azores, and Madeira Islands. The cratering process, overpressure, induced thermal radiation, and tsunami waves were assessed, along with the global effects. The overpressure mainly causes structural damage. The thermal radiation has too short a range to reach the studied localities. The tsunami is undoubtedly the most far-reaching and threatening effect of an asteroid impact in the ocean.