Elliptical Orbit Geometry

The orbit of a planet is an ellipse that goes around the sun at one focus point, according to Kepler’s First Law of Planetary Motion

This means that an ellipse will have two focal points (labeled F and F’ in the illustration), and the sun will take up one focal point.  It can also apply for small objects (moons or satellites) to orbit a larger body (planet or star).  Spacecrafts will orbit around their respective planet or larger body in an elliptical shape (as well as the other conic shapes such as circular, parabolic, and hyperbolic to be covered in upcoming posts). 

Now lets interpret these symbols above

What is eccentricity e ?

Eccentricity is the constant that determines the shape (roundness or flatness) of the orbit.  It’s the focal length divided by the semi-major axis.  (Note: It’s never negative!)

It is important to know the geometry of an ellipse in order to determine the Kepler equations as well and the Energy equations. 

Why Study Astrodynamics?

Image courtesy of Nasa.gov

Astrodynamics is the study of objects moving in space. Well technically the broader definition is called Celestial Mechanics, but the branch that focuses on how spacecrafts and other small objects move in space is called Astrodynamics. An Astrodynamicist is a person who studies Astrodynamics.

Porque estudiar Astrodinámica?

La astrodinámica es el estudio de los objetos que se mueven en el espacio. Bueno, técnicamente, la definición más amplia se llama Mecánica Celestial, pero la rama que se centra en cómo se mueven las naves espaciales y otros objetos pequeños en el espacio se llama Astrodinámica. Un astrodinámico es una persona que estudia astrodinámica.

It is a fun and fascinating topic that covers several different fields and is critical for the mission success of spacecrafts throughout ages. Without Astrodynamics , we would never know how or where a spacecraft will go and won’t be able to execute the right maneuvers to save fuel and time.

Es un tema divertido y fascinante que cubre varios campos diferentes y es fundamental para el éxito de la misión de las naves espaciales a lo largo de los siglos. Sin Astrodinámica, nunca sabríamos cómo ni dónde iria una nave espacial y no podriamos ejecutar las maniobras correctas para ahorrar combustible y tiempo.

Space is hard but doesn’t have to be impossible. I know Astrodynamics can be learned by anyone who loves math and physics, and has a passion for space travel. Not just another graduate school topic but for anyone , from engineers and scientists, to amateur enthusiasts.

El espacio es difícil pero no tiene que ser imposible. Se que la astrodinámica puede ser aprendida por cualquiera que ame las matemáticas y la física, y que tenga pasión por los viajes espaciales. No es solo otra tema de la escuela de posgrado, sino para cualquiera, desde ingenieros y científicos hasta entusiastas aficionados.