Most engineers know how orbits work, especially Kepler's laws of planetary motion. Some engineers also know that Newton's laws of motion and of gravity can be used to plot orbits. Relativistic orbits are however somewhat "mysterious".
This page and its download will show you all the basics of orbits, both for Newtonian and relativistic situations.
Relativistic orbital situations normally arise when the closest point or periapsis of an orbit comes close to a very massive body. More specifically, it is when the fraction: Newton’s gravitational constant (G) times the primary mass, divided by (the periapsis distance times the square of the speed of light) becomes larger than roughly 1 in 100 million. All values are in SI units (kg, m, sec).
In the case of our solar system, it is only planet Mercury that enters a (slightly) relativistic scenario, where the above "relativistic fraction" is about one in 30 million - still very tiny. It is however enough to make Mercury's perihelion shift by an additional 42 arc-seconds per century. This is over and above what can be predicted by using Newton's theory.
To learn more about orbits, you can download a free PDF below. The ultimate engineering view of orbits is contained in the eBook Relativity 4 Engineers.
The eBook Relativity 4 Engineers and the downloads of this website decrypt the 'code', the 'science-speak' of Einstein's theory of relativity into something that us engineers can relate to.
In publications on Einstein's theory of relativity, the popular book is usually too popular and the technical book too technical, with nothing in-between. This eBook and website bridge that gap in a way that will satisfy your engineering curiosity. At the same time, the inevitable mathematics are kept within your engineering "comfort zone".