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- E-Kerosene Potential for Commercial Aviation DecarbonizationPublication . Quaresma, Guilherme da Silva Nheu; Magalhães, Leandro; Ferreira, Ana Filipa; Silva, André Resende Rodrigues daReducing greenhouse gas emissions from aircraft transport is crucial to achieving climate goals. In this sense, the present study looks into the suitability of e-fuels such as e-kerosene in reducing CO2 emissions. The Fleet System Dynamic Model is employed to examine data and predict future trends in line with the Committee on Aviation Environmental Protection. While the findings suggest that achieving carbon-neutral growth is possible, it might take longer than current forecasts indicate. For instance, considering an e-fuel production rate of 15%, it is possible to cut emissions by half around 2060 concerning 2005 levels.
- Modelling Asteroid Trajectory in Earth’s AtmospherePublication . Morais, Renato Henriques; Santos, Luis; Silva, André Resende Rodrigues da ; Melício, RuiEarth’s atmosphere is humanity’s last defence against the potential threat of asteroid impacts. To assess the impact risk and devise effective mitigation strategies, it is essential to understand the interaction between asteroids and the atmosphere. This paper presents a comprehensive study that employs a system of differential-algebraic equations (DAEs) to model the trajectory and associated physical processes involved in an atmospheric entry and the consequent impact of an asteroid. The Apophis asteroid is utilized as a case study to compare and evaluate the performance of two numerical methods for solving these equations. The findings from this research contribute to advancing our understanding of asteroid entry dynamics and provide valuable insights for enhancing asteroid impact mitigation strategies. The Apophis asteroid, represented as a 340 m diameter sphere with a density of 3190 kg.m−3, enters the atmosphere at a velocity of 30759 m.s−1 and a 45-degree angle from an altitude of 81 km. The first method employed is the 4th-order Runge-Kutta method (RK4) with a constant time-step, commonly used for solving highly non-linear problems like this. The second method is based on the Dormand-Prince method, which utilizes a dynamic time step and provides a 4th-order solution with error estimation using a 5th-order solution. Computational efficiency and the resulting solutions are compared between the two methods. The study finds that the Dormand-Prince method offers a more accurate numerical solution with less computational effort. However, both approaches demonstrate a correspondence of at least three significant digits, confirming their validity. Overall, during its traversal through the atmosphere, the Apophis asteroid experiences a decrease in initial velocity by 0.83%, a loss of 22% of its initial mass, and a variation in its angle with the horizontal by 1.5%.