Orbital Mechanics Part 1: Kepler's Law

After a long time, today, on AeroIntellect, I'm going to be talking about probably the most complex concept in aerospace engineering, Orbital Mechanics. I use the word 'complex' because of its dynamic and interdisciplinary nature, as well as its continuous advancements.

In simple words, orbital mechanics is the study of an object's motion in various orbits under the influence of gravity. Initially, humans were interested in studying this due to agricultural and religious reasons; as time passed, our interest deepened due to the desire for space exploration.

Kepler's Law of Orbital Motion

Johannes Kepler is considered the founder of celestial mechanics. He worked with multiple other scientists, including Tycho Brahe, to publish the three laws of orbital motion. These laws are based on observations of planetary motion and form the basis of modern orbital mechanics.

Kepler's First Law: The Law of Ellipses

Kepler's first law states that planets move in elliptical orbits with the Sun at one of the two foci. This essentially means that planets orbit the Sun in a path described as an ellipse. An ellipse is just a geometric shape that looks like an egg. It has two focal points, one of which is where the Sun is located.

Kepler's Second Law: The Law of Equal Areas

The second law states that a radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time. In layman's terms, when a planet or satellite moves through its orbit, its velocity is much higher when it is near the Sun in comparison to when it is further from the Sun. The variation in speed keeps the total area swept out by the satellite over a given period constant, as indicated by the equality, A1 = A2.

Kepler's Third Law

Kepler's third law relates a planet's orbital period to its average distance from the Sun. It states that a planet's orbital period squared is proportional to the semimajor axis of its orbit cubed.

In simple terms, this means that the farther a planet or satellite is from the body it orbits, the longer it takes to complete one orbit.

Thank you for tuning in to today’s blog. Look out for part two, where we talk about orbital transfers and their elements.