Everything You Need to Know About Death Star Orbital Physics
A fully armed and operational physics lesson about ‘Return of the Jedi’
It might seem silly to look at the physics from a movie that was released more than 30 years ago, but here we are. Yes, Star Wars: Return of the Jedi was first in the movie theaters back in 1983. So, why does it even matter? Well, first, it matters to me because I’m a huge Star Wars fan. Second, it seems like the Death Star from Return of the Jedi (or at least pieces of it) shows up in the upcoming Star Wars: The Rise of Skywalker.
So, let’s think about the physics of the Death Star II. Here is a quick refresher: The emperor is building a new (and slightly bigger) Death Star. Hopefully, this time it doesn’t have the vulnerable ventilation shaft — but who knows. While it’s under construction, the Death Star orbits the planet moon of Endor. You see, Endor has this bitchin’ shield generator that the Imperials project from the moon’s surface to protect the space station.
That’s it for the plot — now for the physics. I’m going to assume that the Death Star is in a geostationary orbit around Endor. That means that the space station is not flying under its own power, but is instead just moving due to a gravitational interaction. The geostationary part means that the orbital angular velocity of the Death Star is the same as the rotational angular velocity of Endor. The result is that the Death Star always appears in the same part of the sky relative to Endor.
But how does that work? How do you make something appear to stay in the same place as it orbits a planet? Let’s start with just a basic orbit. There are two big ideas you need to really understand orbital motion. The first is the momentum principle. It looks like this:
The momentum principle says that the nature of forces and motion is that a net force changes the momentum of an object, and the momentum is the product of mass and velocity. The other idea is the model for the gravitational interaction. This holds that there is a gravitational force between any two objects with mass. In particular, this gravitational force decreases in magnitude as the two objects move farther apart. Here is the mathematical model for the gravitational force.