The Physics of the Speeder Chase in ‘Solo: A Star Wars Story’

I make it my job to hunt through all the best trailers and find some cool physics thing to explore. In this case, it’s the trailer for Solo: A Star Wars Story—the Han Solo-led movie, scheduled to come out in May, that takes place some time before Episode IV: A New Hope. Right at the beginning, we see Han driving some type of speeder in a chase scene, taking a super-sharp turn with another speeder in pursuit. Here’s the interesting physics stuff: Notice how it looks like it is sliding around the curve? Why does it do that? Is that how you would actually drive a make-believe speeder?

To answer these questions, we need to think about the nature of forces. Suppose I push on some object at rest such that my push is the only significant force on that object. This could happen with a boat sitting in still water, a hockey puck on ice, or a small spacecraft out in deep space (don’t worry about how that object got into space). What does the object do? A common answer will be to say that the object moves. That’s not wrong, but “move” is not the best answer. With a constant a force, an object increases in speed—that is to say, it accelerates. Acceleration is a measure of the change in velocity of an object, so we could also say that a force changes an object’s velocity. That’s key.

There’s one more really important idea to understand—velocity is a vector. A vector is a quantity in which the direction matters (other vectors are: force, gravitational field, position). If a quantity doesn’t depend on direction, we call that a scalar (like time or mass or electric charge). Since forces change velocity and velocity depends on direction, this means that it takes a force to change the direction of a velocity. Or you could say it takes a force to turn Han Solo’s speeder.

How about a demonstration to show you how this works? Suppose I take a bowling ball and roll it along the floor (everyone should have a bowling ball handy for physics demos). This ball will essentially act like an object moving with a constant velocity since the frictional force is small. I want to make this ball change directions by hitting it with a stick. Which way should I hit it? Watch this.

Just to be clear, let me include this diagram showing the velocity of the ball and the direction of the force.

This sideways tap makes the ball change direction of its motion, but it doesn’t really change how fast it rolls. So really, you can break forces into two components. Forces in the same direction (or opposite) direction as the velocity either make it speed up or slow down. Forces that are perpendicular to the motion (sideways forces) make the object change direction. But you already knew that: When you swing a ball around on a string, it mostly moves at a constant speed but the sideways force from the string causes it to change direction and move in a circle.

Now back to Han Solo’s speeder. I’m not sure exactly how this vehicle drives, but I can make some assumptions (and you can’t stop me). First, it seems likely that those thrusters in the back of the speeder exert some type of force on it. Second, there has to be some significant frictional force pushing in the opposite direction of the speeder’s motion. f not, the thrust from the engines would just make that thing keep speeding up until it got to ludicrous speeds. My last assumption is that the speeder has to use these same rear thrusters for changing direction—unlike an Earth-bound automobile, which uses friction between the tires and the road to make a turn.

How about a breakdown of this slide turn from the trailer? I can’t really do a proper video analysis because of the camera angle, so instead I will just talk about it conceptually. Let me break down the motion into three moments as seen in the diagram below.

At position 1, the speeder is still moving to the left—but Han has turned the speeder so that the thrust can start to push perpendicular to the motion of the vehicle. Next at position 2 the speeder is in the middle of the turn. You can see that the thrust is making it turn. But you can also see that the vehicle thrust is pushing in a way that only changes the direction of the vehicle and not its speed. Finally, at position 3, the turn is complete. Han just needs to turn the speeder so that the thrust is in the same direction as the motion (I assume to counteract the frictional force).

If you don’t like thinking about moving in circles, you have another option. How about this? In position 2 (above) notice that the speeder thrust is to the left and up. The left-pushing part of this thrust is in the opposite direction as the motion of the vehicle, so that it makes it reduce its right-moving speed. The up-pushing part speeds up the vehicle in the upward direction. In the end, this whole maneuver has to do two things: stop the vehicle moving to the right and speed up the vehicle moving upward (in the diagram). That’s why the thrust has to angle the way it does.

Homework: Yes, I do have one question for you to work on. Suppose this speeder is about the size and shape of a terrestrial car. In that case, you can estimate the thrust force needed to move it along at a constant velocity. Now that same force has to make make the car turn—but the turning force depends on the mass of the car (unlike driving forward which only depends on the shape). Use this to estimate the thrust to mass ratio for the speeder. Yes, I think this can be done. You might need to make some rough estimates of vehicle speed and turning radius.

Can an Airplane remove for a going Runway?

This real question is probably as old because the airplane itself. It goes something such as this:

An airplane includes a takeoff speed of 100 mph (I just made that number up). What if it gets for a super giant treadmill machine that moves backwards at 100 mph. Could a plane with this giant treadmill machine remove or would it not simply sit there going at 0 miles per hour?

Initial question a reasonable individual would ask is “in which would you get yourself a giant plane-sized treadmill machine that goes 100 miles per hour?” Yes, which indeed a great question—but i will not answer it. Instead, i will offer this question top physics answer I am able to.

Before i actually do that, i ought to explain that others also have answered this question (not surprising as it’s super old anyway). First, there was the MythBusters episode from 2008. In fact, they didn’t answer the question—they did issue. The MythBusters made a giant conveyer belt having plane about it. It had been awesome. Next, there is the xkcd response to this concern (additionally from 2008).

Now you get my answer. I shall respond to with different examples.

A Car on a Conveyer Belt

This isn’t so difficult. Let’s say I put an automobile going 100 mph on a conveyer gear that is also going 100 mph? It could appear to be this (something like this):

Actually, there’s probably no real surprise right here. The vehicle’s tires would roll at 100 miles per hour as the treadmill machine (or conveyer gear) moves back at 100 mph so that the vehicle stays stationary. Really, here is a somewhat cooler example (with the same physics).

Let me reveal an test (also from MythBusters) which they shot a ball at 60 mph out of the back of a truck additionally going 60 miles per hour. You can view your ball stays fixed (with regards to the ground).

Super Brief Takeoff

Here is a airplane from Alaska that takes off in a really short distance.

How exactly does this work? We’ll provide you with a hint—there is definitely a strong wind blowing in to the front side for the plane. Without a headwind, this couldn’t happen. However if you consider it, this brief lose is certainly much such as the vehicle regarding treadmill machine. For the plane, it generally does not drive on the floor, it “drives” in the air. In the event that airplane possesses takeoff rate of 40 miles per hour and is in a 40 mph headwind, it doesn’t even have to go at all according to the ground.

Airplane for a Conveyer Belt

Now let us do it. This is a short clip from MythBusters launching a plane on a going treadmill machine.

Yes, it requires off. A plane takes faraway from a runway relocating the opposite direction? But why? It is because the tires for a plane never really do anything. The only function for the wheels would be to produce low friction between your aircraft together with ground. They do not also push the airplane forward—that is performed by the propeller. Truly the only distinction whenever releasing an airplane for a moving runway is the fact that wheels will spin at twice the standard speed—but that willn’t matter.

Therefore the airplane on a treadmill works, but how about a case where in fact the plane wouldn’t take off? Imagine if the plane ended up being similar to a glider with motorized tires? For a normal runway, these motorized tires would raise the rate for the glider until it reached takeoff speed. However, if you place this on a going runway, the tires would spin on right rate and cancel the motion regarding the treadmill so the airplane would remain motionless and not reach the proper rate for the launch.

okay, making sure that is the response to everybody’s favorite question. But never worry, this answer wont stop the endless discussion—that will go on forever.