First post

I owe my first encounters with celestial mechanics to a popular science magazine and a university-level supplementary textbook. The unlikely pair consisted of a special issue of Le Scienze (the Italian edition of Scientific American), devoted to the scientific biography of Sir Isaac Newton, and of the Italian translation of Schaum's Outline of Theoretical Mechanics, which, from its dusty appearance, had spent quite some time forgotten on a shelf of a surprisingly well-stocked high school library.
 

 
Still barely halfway through high school, and equipped only with a shaky understanding of limits and derivatives, I marveled at the genius of the Man who invented Calculus, while the dusty textbook inspired, intrigued, and (more often than not!) frustrated me. These two oddly complementary readings cemented my choice of Physics as university major.

More than twenty years later, the better part of which I have spent pursuing a PhD in Astrophysics and later working as a researcher, I am still awestruck with the mathematical elegance and tremendous predictive power commanded by the laws of orbital mechanics. Their remarkable accuracy is manifested in some of the technologies which we nowadays routinely take for granted (satellite-based remote sensing, GPS...), or are promised by the currently unfolding second space revolution (satellite mega-constellations, space tourism, asteroid mining, ...?).

In writing this blog, I have two main purposes. First, it is meant as a personal log of my own explorations of celestial mechanics and astrodynamics, free of the constraints imposed by standard academic publications. At the same time, I hope that it might resonate with others who share my fascination with these subjects, and could be interested in some technical, practical, or computational aspects discussed in my posts.

Just as the word "planet" implies, not all those who wander are lost.

Comments

Post a Comment

Popular posts from this blog

Trajectory Optimization with a Solar Sail: My GTOC13 Experience

Image
The Global Trajectory Optimization Competition (GTOC) brings together astrodynamics, optimization, and creative problem-solving: it is the  "America's Cup of rocket science" . This year I took part in the competition for the first time, and managed to enter the leaderboard with a respectable final score.  In this post, the first part gives a high-level overview of how I approached the challenge, while the (more technical) second part will discuss the implementation details of my solution.   This year's edition revolved around the exploration of the exoplanetary system of the fictional star Altaira, whose planets sport a variety of pop-culture-inspired names. Assuming the interstellar leg is already taken care of, the task was to design a trajectory that maximizes the number and scientific value of reconnaissance close approaches with Altaira’s planets, asteroids, and comets. The dynamical model includes unpowered gravity assists with the major planets (minor bo...
Read more

The "Sphere of Influence" of the Moon is not really spherical

Image
A tool often employed in the early stages of space mission design is the patched conics approximation. In this formalism, a trajectory is approximated by a sequence of two-body orbits, defined with respect to an appropriately changing primary body, according to the updated position of the spacecraft. The validity of this approach rests on the assumption that in each portion of the trajectory the acceleration of the spacecraft mostly arises from the gravitational attraction by a single body, which dominates over all the other perturbations. For instance, to an excellent degree of approximation, the motion of an interplanetary probe is mostly governed by solar gravity, except when in the immediate vicinity of a planet. The "Sphere of Influence" (SOI) of a celestial body with respect to a distant, major primary is formally defined below. At the lowest order of approximation, the SOI is a sphere centered on the secondary body, and of radius $R_S = D \, \left(\frac{m}{M}\right)^{2...
Read more

The rhythms of the sea: a primer on tides

Image
West Sands Beach near St. Andrews, Scotland, where the tidal range (the difference between high tide and low tide) can be up to 4 meters.    Few natural phenomena capture the imagination and, at the same time, affect daily experience as much as the oceanic tides. With their daily rhythm, tides may have even shaped the evolution of life itself: it has been suggested that tides played a role in the transition from marine to land animals at the end of the Devonian period [1].   Understanding tides allows us to fully appreciate a hidden clockwork that connects celestial mechanics with the ebb and flow of the sea, and its impact on life on Earth.  Tides follow highly regular patterns, as is immediately obvious to anyone who lives near a coastal area with a tidal range of the order of meters (as opposed to the puny tens of cm in my Mediterranean hometown!). In this post I will discuss how the most readily observable periodicities in the rise and fall o...
Read more