Two ways of defining the Poincaré astrocentric coordinates in the planetary problem are considered and compared. Both ways are shown to lead to the same system of equations of planetary motion after ...the elimination of the center of mass. Formulas for the transition from the osculating elements in the Poincaré coordinate system to the ordinary astrocentric osculating elements are given. The analytical apparatus constructed here is suitable for the practical application of perturbation methods, in particular, averaging methods.
We measured concentrations and isotopic ratios of noble gases in the Rumuruti (R) chondrite Mount Prestrud (PRE) 95410, a regolith breccia exhibiting dark/light structures. The meteorite contains ...solar and cosmogenic noble gases. Based on the solar and cosmogenic noble gas compositions, we calculated a heliocentric distance of its parent body, a cosmic‐ray exposure age on the parent body regolith (parent body exposure age), and a cosmic‐ray exposure age in interplanetary space (space exposure age) of the meteorite. Assuming a constant solar wind flux, the estimated heliocentric distance was smaller than 1.4 ± 0.3 au, suggesting inward migration from the asteroid belt regions where the parent body formed. The largest known Mars Trojan 5261 Eureka is a potential parent body of PRE 95410. Alternatively, it is possible that the solar wind flux at the time of the parent body exposure was higher by a factor of 2–3 compared to the lunar regolith exposure. In this case, the estimated heliocentric distance is within the asteroid belt region. The parent body exposure age is longer than 19.1 Ma. This result indicates frequent impact events on the parent body like that recorded for other solar‐gas‐rich meteorites. Assuming single‐stage exposure after an ejection event from the parent body, the space exposure age is 11.0 ± 1.1 Ma, which is close to the peak of ~10 Ma in the exposure age distribution for the solar‐gas‐free R chondrites.
Yves Simonin, a rather obscure professor of hydrography in Bayonne, submitted five scientific papers to the Paris Academy of Sciences between 1738 and 1740, which only survive in the original ...manuscript versions. The topics Simonin deals with in these texts are essentially three: the rectification of navigation charts of the Southern Sea, the shape of the Earth, and the heliocentric theory. Far from acknowledging Simonin's contribution to the ongoing academic debate as a valuable one, the institution systematically rejected his work. In this paper, I first provide a critical analysis of Simonin's manuscripts. As I argue, their originality lies in the adoption of the perspective of a practitioner of and expert in navigational techniques. I then investigate the reasons behind the Academy's negative reception of Simonin's papers, casting light on the expertise required to participate in academic debates in the mid‐18th century, and on the limits set by the institution to the possibility of external intervention.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The transfer between two coplanar Keplerian orbits of a spacecraft with a continuous-thrust propulsion system is a classical problem of astrodynamics, in which a numerical procedure is usually ...employed to find the transfer trajectory that optimizes (i.e., maximizes or minimizes) a given performance index such as, for example, the delivered payload mass, the propellant mass, the total flight time, or a suitable combination of them. In the last decade, this class of problem has been thoroughly analyzed in the context of heliocentric mission scenarios of a spacecraft equipped with an Electric Solar Wind Sail as primary propulsion system. The aim of this paper is to further extend the existing related literature by analyzing the optimal transfer of an Electric Solar Wind Sail-based spacecraft with a Sun-facing attitude, a particular configuration in which the sail nominal plane is perpendicular to the Sun-spacecraft (i.e., radial) direction, so that the propulsion system is able to produce its maximum propulsive acceleration magnitude. The problem consists in transferring the spacecraft, which initially traces a heliocentric circular orbit, into an elliptic coplanar orbit of given eccentricity with a minimum-time trajectory. Using a classical indirect approach for trajectory optimization, the paper shows that a simplified version of the optimal control problem can be obtained by enforcing the typical transfer constraints. The numerical simulations show that the proposed approach is able to quantify the transfer performance in a parametric and general form, with a simple and efficient algorithm.
Forest fires that occurred in Portugal on June 18, 2017, caused several tens of human casualties. The cause of their emergence, as well as many others that occurred in western Europe at the same time ...remained unknown. Taking into account consequences, including loss of human lives and endangerment of ecosystem sustainability, discovering of the forest fires causes is the very significant question. The heliocentric hypothesis has indirectly been tested, according to which charged particles are a possible cause of forest fires. We must point out that it was not possible to verify whether in this specific case the particles by reaching the ground and burning the plant mass create the initial phase of the formation of the flame. Therefore, we have tried to determine whether during the critical period, i. e. from June 15-19 there is a certain statistical connection between certain parameters of the solar wind and meteorological elements. Based on the hourly values of the charged particles flow, a correlation analysis was performed with hourly values of individual meteorological elements including time lag at Monte Real station. The application of the Adaptive Neuro Fuzzy Inference System models has shown that there is a high degree of connection between the flow of protons and the analyzed meteorological elements in Portugal. However, further verification of this hypothesis requires further laboratory testing.
nema
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Using a Newtonian model of the Solar System with all 8 planets, we perform extensive tests on various symplectic integrators of high orders, searching for the best splitting scheme for long term ...studies in the Solar System. These comparisons are made in Jacobi and heliocentric coordinates and the implementation of the algorithms is fully detailed for practical use. We conclude that high order integrators should be privileged, with a preference for the new
method of Blanes et al. (
2013
).
The Copernican question Westman, Robert S
2011., 20110702, 2011, c2011., 2011-07-28, 20110101
eBook
In 1543, Nicolaus Copernicus publicly defended his hypothesis that the earth is a planet and the sun a body resting near the center of a finite universe. But why did Copernicus make this bold ...proposal? And why did it matter? The Copernican Question reframes this pivotal moment in the history of science, centering the story on a conflict over the credibility of astrology that erupted in Italy just as Copernicus arrived in 1496. Copernicus engendered enormous resistance when he sought to protect astrology by reconstituting its astronomical foundations. Robert S. Westman shows that efforts to answer the astrological skeptics became a crucial unifying theme of the early modern scientific movement. His interpretation of this "long sixteenth century," from the 1490s to the 1610s, offers a new framework for understanding the great transformations in natural philosophy in the century that followed.
Propellantless propulsive systems such as Electric Solar Wind Sails are capable of accelerating a deep-space probe, only requiring a small amount of propellant for attitude and spin-rate control. ...However, the generated thrust magnitude is usually small when compared with the local Sun’s gravitational attraction. Therefore, the total velocity change necessary for the mission is often obtained at the expense of long flight times. A possible strategy to overcome this issue is offered by an Earth gravity-assist maneuver, in which a spacecraft departs from the Earth’s sphere of influence, moves in the interplanetary space, and then re-encounters the Earth with an increased hyperbolic excess velocity with respect to the starting planet. An Electric Solar Wind Sail could effectively drive the spacecraft in the interplanetary space to perform such a particular maneuver, taking advantage of an augmented thrust magnitude in the vicinity of the Sun due to the increased solar wind ion density. This work analyzes Earth gravity-assist maneuvers performed with an Electric Solar Wind Sail based probe within an optimal framework, in which the final hyperbolic excess velocity with respect to the Earth is maximized for a given interplanetary flight time. Numerical simulations highlight the effectiveness of this maneuver in obtaining a final heliocentric orbit with high energy.
We consider the dynamical evolution of planetary systems whose structure is nearly circular and coplanar. The analysis is performed by the Hori–Deprit averaging method within the theory of the first ...order in planetary masses. A convenient set of canonical elements and a rarely employed variety of astrocentric coordinates are used to derive the equations of motion. Owing to the use of the chosen system of canonical elements, the expansions of the right-hand sides of the averaged equations contain a relatively small number of terms. Compared to other widespread coordinate systems, the astrocentric coordinates used by us allow a more convenient representation of the disturbing function to be obtained and do not require its expansion into a series in powers of a small parameter. On time scales
years we have studied the long-term evolution of the planetary systems HD 12661,
Andromedae, and some model systems by numerical integration of the averaged equations. Possible secular resonances have been revealed in the systems considered.
We investigate the heliocentric in-orbit repositioning problem of a spacecraft propelled by an Electric Solar Wind Sail. Given an initial circular parking orbit, we look for the heliocentric ...trajectory that minimizes the time required for the spacecraft to change its azimuthal position, along the initial orbit, of a (prescribed) phasing angle. The in-orbit repositioning problem can be solved using either a drift ahead or a drift behind maneuver and, in general, the flight times for the two cases are different for a given value of the phasing angle. However, there exists a critical azimuthal position, whose value is numerically found, which univocally establishes whether a drift ahead or behind trajectory is superior in terms of flight time it requires for the maneuver to be completed. We solve the optimization problem using an indirect approach for different values of both the spacecraft maximum propulsive acceleration and the phasing angle, and the solution is then specialized to a repositioning problem along the Earth's heliocentric orbit. Finally, we use the simulation results to obtain a first order estimate of the minimum flight times for a scientific mission towards triangular Lagrangian points of the Sun−Earth+Moon system.
•This paper analyzes the in-orbit repositioning of an E-sail-based vehicle.•The problem is studied by evaluating the minimum flight time.•A mission towards Sun–Earth triangular Lagrangian points is discussed.
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