Orbital Mechanics, Explained
By Inchara J, Edited by Kavya Gurunath, Laya Vijay, & Jeet Parikh, Layout by Inchara J, Art by Thejo Thattala, & Blogged by Kavya Gurunath
The Moon rotates around the Earth as the Earth’s natural satellite. The Earth orbits the Sun, creating seasons as human life knows it. Orbital mechanics is the application of math to help spacecraft launch and is based on orbits. The history of orbital mechanics and whether it should be studied or not is controversial, however, orbital mechanics help to calculate trajectories and understand the motion of planets.
The history of orbital mechanics is bleak and filled with controversy. The controversy mainly came from the church, because when orbital mechanics was first discovered, it disproved the widely believed fact that our universe was geocentric. Geocentric meaning the Earth was in the center of the solar system, not the Sun. Thus, studying orbital mechanics became shunned upon, since it went against traditional Christian (not current) beliefs and was marked as heresy. Johannes Kepler, an astronomer, was the first human to create a model of the orbit of a planet with high accuracy. Nicolaus Copernicus was the first man to suggest that the Earth was not the center of the solar system and Kepler worked off of this, creating Kepler’s laws, which are used in orbital mechanics today. Isaac Newton helped orbital mechanics grow by defining gravity and its laws.
Kepler’s laws are a huge aspect of orbital mechanics, and can be described as follows: The Law of Ellipsis: The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus. The Law of Equal Areas: An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time. The Law of Harmonies: The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun.
The first law is simple to understand, as one can refer to the graph of an elliptical shape and imagine it as the orbit of a planet, with one of the foci being the Sun. The second law pertains to the speed of a planet while orbiting, and sums up that a planet will travel quicker when near the sun and decrease in speed when further away from the sun. The third law is a comparison between the period of an orbit to the radius of an orbit. The third law is different from the other two in a way that doesn’t describe motion, but rather compares two necessary elements- periods of any two planets and the cubes of their distances- of an orbit.
Orbital mechanics is necessary when it comes to space travel and exploration. It is used for calculating trajectories, including maneuvers and plane changes that can be used to predict propulsive maneuvers (accelerating spacecraft). Orbital mechanics also helps physicists discover types of orbits, and helps engineers operate satellites and other important spacecraft. Satellites assist in our GPS receivers and orbits are applied to both this and classifying minor planets.
Celestial mechanics deals with the motion of objects in space. While it is incredibly similar to orbital mechanics, celestial mechanics is more generic, and orbital mechanics pertains to problems mainly spacecraft-related. However, much of orbital mechanics is based on celestial mechanics, but the application and Kepler’s laws are what make the two differ.
Orbital mechanics will definitely play a big hand in future space exploration. With all the space missions set in the near future, orbital mechanics is a subject worthy of learning, and with a better understanding of it, space exploration will be able to exceed our expectations more than ever.
References
Kepler’s Three Laws. (n.d.). The Physics Classroom. Retrieved April 19, 2021, from https://www.physicsclassroom.com/class/circles/Lesson-4/Kepler-s-Three-Laws
Orbital Mechanics. (n.d.). PRe-Engineering. Retrieved April 19, 2021, from https://tylerbirch.weebly.com/orbital-mechanics.html
Wikipedia contributors. (2021a, January 29). Orbital mechanics. Wikipedia. https://en.wikipedia.org/wiki/Orbital_mechanics
Wikipedia contributors. (2021b, January 30). Celestial mechanics. Wikipedia. https://en.wikipedia.org/wiki/Celestial_mechanics
Originally published at https://issuu.com.
