Force, acceleration, velocity, speed, gravity, weight, G-force, Newton, meters/sec, meters/sec/sec
Next Generation Science Standards:
- HS-PS2-1. Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass and its acceleration.
Article Guide: X-wing part 1 Article Guide
A previous version of this post had an error in the calculation for X-wing speed in meters/sec. That mistake has been since been fixed.
After 2 painstaking years of waiting, Star Wars fans across the world will rejoice as Star Wars: The Last Jedi opens in theaters December 15th. I am a huge Star Wars fan. I own a lightsaber TV remote and full size, movie quality, Chewbacca costume. The only reason I became a science teacher was that I could not become a Jedi Knight.
To prepare for the new movie, I began watching the previous Star Wars films in sequential order. In re-watching my favorite space battles, I started to think about what would it be like to fly an X-wing. It would be unfathomably cool, of course. But the high speeds and constant maneuvering of a deep space dogfight would cause the pilot to experience huge changes in the forces on their body. I began to wonder if a human could even handle flying an X-wing.
So I did what any self-respecting science teacher would do: I went straight to work calculating the Newtonian forces on an X-wing pilot. Force is a function of how much an object accelerates and if I could calculate how quickly a starfighter changes its velocity, I could get a rough estimate of the forces being exerted on a pilot’s body.
Full disclosure: this is by no means is this an attempt to have an actual understanding of the physics of Star Wars. I’ve ignored Bernoulli’s Principle (an X-wing has no airfoil shape and would struggle to fly on a planet with an atmosphere) and I’ve made some assumptions about the X-wing’s speed. For the sake of this thought experiment, I am also going to stick to Newtonian physics and ignore any effects the Theory of Relativity may have in this scenario. This isn’t an attempt to understand how realistic the physics of Star Wars is, rather an awesome application of the concept of force and classical physics.
The Force according to Darth Newton
Before we can start calculating forces on a pilot, we have to establish a few key terms. You may recall from science class that a force is a push or pull on an object. You may also remember that force is calculated using Issac Newton’s second law of motion by the following equation:
As you can see, you can find the force of an object if you multiply its mass, how much matter it has, by its acceleration, how quickly it changes its velocity (speed or direction). We use the units kilogram (kg) for mass, meters per second per second (meters/sec/sec) for acceleration and Newtons (N) for force. While the math is important, the key concept here is that a force is exerted on an object only when it accelerates. This means if an object speeds up, slows down, or changes direction, it means a force is acting on it. You experience this in everyday life. When a car slows down, its breaks are applying a force to its wheels. If you kick a soccer ball, you apply a force and the ball speeds up. When you are on a roller coaster and go around a curve, you lean to the side. Those forces are due to inertia, which explain in more detail later.
The Force of gravity
In fact, you are accelerating towards the center of the Earth as you read this post. The Earth’s gravitational field is pulling all objects with at an acceleration of 9.8 meters/sec/sec. Even when you are just standing on the ground, you are still accelerating towards the center of the Earth. We call this gravitational force weight, which is different from mass. Mass is a measure of how much matter an object has, weight is a measure of the force of gravity on that object. You can test this by dropping a bowling ball and tennis ball from the same height at the same time. While their masses differ, gravity acts on them in the same way and they accelerate towards the center of the Earth at the same rate.
However, if the object that is pulling on you changes, the weight you will experience will also change. If you were on the Moon, whose gravitational field is much weaker than the Earth, it would be pulling you down at a much lower acceleration. The force would then be much less and you would experience a weight that is much lighter. The opposite would be true if you were on a planet with stronger gravity. You would experience a higher weight on Jupiter because it’s gravitational field is stronger and would be pulling you down with a higher acceleration, and therefore a stronger force. What is important here is that regardless of where you are in the universe, your mass stays the same but your weight changes based on the acceleration due to gravity.
Ain’t nuthin’ but a G thing
So how does all this relate to piloting an X-wing? Since a starfighter pilot is in space, he or she wouldn’t have a planet or moon’s gravitational force acting on them and wouldn’t experience any weight, but if they were to accelerate in any way, speeding up, slowing down, or changing direction, it would change the forces acting on the pilot’s body.
A term that we can use to describe this is G-force. One G-force is equal to the amount of weight person would experience on Earth at rest. However, if you accelerate, you change the amount of force acting on your body. For example, when you hit the gas in your car or take off on an airplane, you often feel like you are pushed back in your seat a little bit. That’s because there is an extra force acting on your body due to the fact you are accelerating.
Accelerating too quickly could mean a dangerous amount of force acting on your body; too much G-force and your heart will not be able to pump blood to your brain. Fighter pilots, who make turns at very high velocities, experience blackout symptoms at 10-12 G’s and death would likely happen at around 20-25 G’s. Which brings us to the essential question: How many G’s would you experience in an X-wing and would the human body be able to handle it? If we know how quickly an X-wing changes speed or makes a turn, we can fairly easily calculate how many G-forces would be acting on the pilot.
How fast can an X-wing go?
Before we are able to calculate the G-forces on an X-wing pilot, we’ve got find out how fast an X-wing can accelerate. To do that, we need to figure out the starfighter’s top speed. According to the Star Wars database Wookiepedia, the unit of speed used in Star Wars is the Megalight or MGLT, which doesn’t really give us anything that could be applied to a Newtonian physics equation. How do we convert a made up unit into something useful? The site claims that the top atmospheric speed for an X-wing would be 1,050 km/hr, but that’s barely faster than a commercial airliner, let alone modern fighter jets like the MiG or the F-22, and might not be enough speed to keep the X-wing aloft, given that the wings do not have an airfoil shape.
Let’s see if we can’t we can’t approximate something more like what we see in the movies. I am going to assume that MGLT uses the speed of light is a base unit. Mega in the metric system is equal to a factor of one million, but multiplying the speed of light by a million would be an absurd number that wouldn’t work in anyone’s universe, Newton, Einstein or George Lucas.
Instead, I am going to divide the speed of light by one million, make our unit a microlight. With the speed of light being 299,792,458 meters/sec, 1 MGLT would equal 299.79 meters/sec. Since an X-wing’s top speed is 100 MGLT, its speed in meters per second would be 29,997 m/s or around 107,925 km/h (67,061 mph). To give a little perspective, this would get you from the Earth to the moon in around 3.5 hours . In watching the movies, this seems like a reasonable assumption, especially when you see how quickly starfighters escape large objects like the Death Star. Now that we have a speed, we can now calculate acceleration and the force.