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Celestial Mechanics and Astrodynamics
Published in K.T. Chau, Applications of Differential Equations in Engineering and Mechanics, 2019
In this chapter, we demonstrated that all three of Kepler’s laws are a natural consequence of the universal law of gravitation. Application of gravitational law to the studies of the orbits of artificial satellites is considered. The first, second, and third escape velocities from Earth’s surface are considered. The Hohmann transfer orbit is studied in the context of interplanetary travels, as an energy-efficient way of space travel. The striking speed of meteors on Earth is studied as a special case of the orbital equations. Einstein’s general relativity is employed in considering the precession of the perihelion of Mercury, through the use of Schwarzschild geometry of four-dimensional space-time. The problem of the flight of a rocket or missile near Earth’s surface is considered as a special case of elliptic orbits. The dynamics of re-entry of spacecraft back to the Earth through the atmosphere is introduced and Yarochevsky analytical solution is derived for the special case of shallow entry with constant gravitational acceleration. The Lagrangian Points of the restricted three-body problem are considered.
Remote Sensing Sensors and Platforms
Published in Ni-Bin Chang, Kaixu Bai, Multisensor Data Fusion and Machine Learning for Environmental Remote Sensing, 2018
The most popular platform for remote sensing aloft is a space-borne satellite. Over three-thousand remote sensing satellites have been launched since 1957 at which Russia launched the first man-made satellite of Sputnik 1. In addition, the space shuttle, which functions as a remote sensing satellite, belongs to this category. However, the space shuttle can be reused for multiple missions, unlike satellites. The path of a satellite in space is referred to as its orbit. Satellites can be classified based on either orbital geometry or timing for image acquisition. Two types of orbits, including geostationary/equatorial and polar/Sun synchronous, are commonly used as a broad guideline for the classification of remote sensing satellites (Natural Resources Canada, 2017). These orbits are fixed after launch and can be only slightly adjusted to maintain their anticipated position for environmental monitoring and earth observation over time. The type of orbit that affects the design of the sensor onboard determines its altitude with respect to Earth and the limit of its instantaneous field of view (i.e., the area on Earth which can be viewed at any moment in time).
From the Moon to Mars
Published in Jonathan Allday, Apollo in Perspective, 2019
An orbit exists when the gravitational force acting on a body provides the necessary centrifugal force, given the radial size and speed of the orbit. When two massive bodies are involved, the options for a much smaller third body become somewhat more interesting.11 There are five Lagrange (L) points in a two-body system in which an (in principle infinitesimal) third body can exist in a stable location relative to the others.
Bearing Models for Advanced Ball Bearing Simulation
Published in Tribology Transactions, 2023
L. Houpert, C. Penny, J. Clarke
Similar trends in the two models are observed, with surprising sign variations of the gyroscopic speed and pivoting speed but with large differences in the values of these parameters. For example, at maximum load in the model described here, = –673 rad /s and = –75 rad/s (hence = 677 rad/s), while in reference (10) values of = –440 rad/s and = –370 (hence = 575 rad/s) are reported. The orbital speed in both models ( rad/s), is similar. The ball rotational angle (in the plane of contact) varies between 8 and –6 degrees in the authors’ model, and between 39 and –39 degrees in Jain’s article. Pure rolling occurs near the contact centers using both models, but with a set of ball kinematics, contact angles, and angle that is quite different.
Recent advances in electro-Fenton process and its emerging applications
Published in Critical Reviews in Environmental Science and Technology, 2023
Puthiya Veetil Nidheesh, Soliu O. Ganiyu, Carlos A. Martínez-Huitle, Emmanuel Mousset, Hugo Olvera-Vargas, Clément Trellu, Minghua Zhou, Mehmet A. Oturan
As previously stated, the electrochemical reactor design is a key factor to improve the efficiency of the EF processes as well as the possibility to scale up the treatment technology. For this reason, different groups have investigated different alternatives for the electrochemical devices. Among the most interesting contributions, Zahrani and Ayati (2020a, 2020b) have reported the use of a nanocatalyst in a novel reactor with orbiting electrodes. In this case, the performance of EF process was significantly improved by using the heterogeneous approach. The EF reactor was constructed with cylindrical plexiglass with graphite electrodes, in which 4 anodes were placed around the main container, and 4 cathodes were putted in the middle using a rotating mechanical stirrer. The orbital speed of the electrodes in the center was adjusted. The described arrangement allows to decrease the effects of the mass transport due to the agitation flow in one direction as well as to reduce the diffusion layer. The results clearly evidenced that the treatment of organic compounds was suitable over a wide range of pH, and is able to eliminate 90% of organics without adjusting the pH of the effluent. The authors also showed the reusability of zeolites-based nanocatalyst, and the lower energy requirements due to the use of orbiting electrodes, allowing to develop an eco-friendly EF system. It is important to remark that orbiting electrodes enhanced the diffusion of the in-situ generated •OH and H2O2, favoring an efficient elimination of the organics.
Hypervelocity impact on honeycomb structure reinforced with bi-layer ceramic/aluminum facesheets used for spacecraft shielding
Published in Mechanics of Advanced Materials and Structures, 2022
Sid Ahmed Slimane, Abdelkader Slimane, Ahmed Guelailia, Abdelmadjid Boudjemai, Said Kebdani, Amine Smahat, Dahmane Mouloud
Structural shields for space application systems are necessary components due to the hostile environment found in space. Once the spacecraft is operating in Earth orbit, the micrometeoroids and orbital debris (MMOD) may impact the spacecraft at an extremely high velocity and can cause serious damage to the structural integrity or even render the payload partially or totally unusable [1]. Therefore, rigorous design parameters of shield structures under hypervelocity impact conditions must be fully understood for spacecraft safety design.