I'm supposed to be doing important things. In particular, I should be finishing up my complete video analysis of the Star Wars VII trailer. However, I'm getting side tracked.

In my last analysis, I found that the Millennium Falcon pulled a 12 g maneuver as it flew near the ground. 12 g's is a lot, but wait - there was another high-g move in The Empire Strikes Back. Before going into a "cave" in an asteroid, Han does a nice little loop. Here, check it out.

You can't see the whole "loop" motion, but I think this is enough for an estimate of the Millennium Falcon's acceleration.

Estimation of Speed ——————-

Before looking at the actual loop, let me get an estimate of the Falcon's speed. I will look at the part of the motion with the ship moving in a mostly straight line as it enters "the cave" - which we all know is really a giant space worm.

This short clip will work great for video analysis (I use Tracker Video Analysis). Even though the camera pans during the motion, the Falcon is far enough away to ignore perspective problems and it moves perpendicular to the camera. For the scale, I can use the Millennium Falcon itself - it's about 25.6 meters across.

Here is a plot of the vertical position of the spaceship during this time.

From the slope of this line, we can see the speed of the Falcon is about 267 m/s. I like that speed. Why? I like it because the speed I estimated for the Falcon in the Star Wars VII trailer was 200 m/s. Those are about the same range.

G-Forces in the Loop ——————–

Now we can look at the looping maneuver. Sure, we can't see the whole thing, but we can still make some estimates. Right before the Falcon leaves the field of view, it seems to be going mostly "straight up". After 2.17 seconds, it seems to be going "straight down". It doesn't matter if did a circular loop or stopped and turned around. Either way, I can calculate the average acceleration during this time assuming it started and ended with the same speed of 267 m/s (but in different directions).

Be careful. Don't make the mistake I have seen many physics students make. The mistake is to say that since v 1 and v 2 are the same, the change in velocity (and thus the acceleration) is zero. No. This is wrong. The velocities ARE NOT the same, the speeds are the same. Acceleration depends on the change in velocity, not the change in speed. If I just want to find the vertical component of the acceleration, the initial velocity would be positive and the final would be negative. This means that the change in velocity would be -2*267 m/s and not zero.

Now to calculate the average acceleration (I'm just giving the magnitude).

This would be 25 g's. Yup. That quick maneuver in Star Wars VII doesn't look so tough anymore at only 12 g's. Actually, this loop might be a little less than 25 g's since the gravitational force from the asteroid would also be pulling down. However, I think that gravitational force would be fairly small.

At this point, I think I was wrong in my previous post about the Millennium Falcon. I said that there was nothing inside the spacecraft to help them make a high-g turn. Well, that can't be true. There is no way they could pull 25 g's while Princess Leia was just standing up in the cockpit.

Screen shot from Star Wars Empire Strikes Back

Standing up in a 25 g loop would be like holding up 2,500 pounds on your shoulder (if you are a 100 pound woman). Of course you would also pass out from the blood rushing to your legs. But since Leia doesn't pass out (as seen in the clip), the Millennium Falcon must have some type of acceleration compensation device. There, are you happy?

Could You Walk Inside an Asteroid? ———————————-

While I'm on the subject of Empire Strikes Back, I might as well consider the part right after the Falcon loop where Han, Chewie and Leia get out of the spacecraft and walk around. Could they do this? Would they need space suits?

How big is this asteroid? Here is a nice shot of the asteroid.

Screen shot from Star Wars Empire Strikes Back

I'm fairly certain that one of those two crater looking things is where the space lizard lives. If I can get an estimate of the size of the big circular thingy (I don't think it's actually a crater) then I can estimate the radius of the asteroid (assuming it's spherical). Ok, here's what I'm going to do. First, use the size of the Millennium Falcon to estimate the height of the crater wall. From that, I will use the curvature of the asteroid to estimate the radius. This diagram might help.

I know it's just an estimate, but from this I will go with an asteroid radius of 2.81 x 104 meters. Yes, that's big - but is it big enough? First, we need the mass. 3It seems that 2000 kg/m3 is a reasonable value for the density of an asteroid. If the asteroid is spherical, it would put the mass at 1.8 x 1017 kg.

With the mass and the radius of the asteroid, I can calculate the gravitational field on the surface using the following:

In the expression, G is the universal gravitational constant. Putting in my values, I get a field strength of 0.015 N/kg or just 0.1 percent the value on the surface of the Earth. Just for comparison, this gravitational field is low but it is still higher than the value on the surface of Comet 67P. Could you walk on this asteroid? Yes, but it would be very difficult because every little push from your foot would make you leave the surface for a little bit.

What if you travel deep inside the comet? Actually, this would be worse. It turns out that if the mass of the asteroid is spherically symmetric, the gravitational field doesn't depend on the material that is "above" you but only on the stuff closer to the center. I know that sounds confusion, but here is an older post that shows why this happens. As you go closer to the center of the asteroid, the gravitational field gets smaller (it would be zero in the center). This means it would be even more difficult to walk inside than on the surface.

But would you need a spacesuit? Or would you just need an air supply?

Screen shot from Star Wars Empire Strikes Back Screen shot from Star Wars Empire Strikes Back

For astronauts, a spacesuit does several things. It protects them from the the large temperature differences (hot in the Sun shine cold otherwise), it gives them air and it provides pressure. Here is one of the many online answers to "can you survive in space without a spacesuit?"

Han and Leia have air (it looks like it) - oh and also Chewie. I am going guess that the inside of a space worm is warm enough that they don't freeze. But what about air pressure? Calculating the pressure due to a gas pulled down by gravity isn't so simple. I'm just going to guess with a low gravitational field and an atmosphere that would only be perhaps 1000 - 2000 meters deep, the gas pressure inside the space worm would be quite low. I'm guessing you would still need a spacesuit.

A note from George ——————

I'm not even finished with my analysis of the Star Wars VII trailer. But this is getting out of control. Too many posts about Star Wars has me feeling like Luke laying in the snow on Hoth after escaping the wampa. Then in the distance, I see a faint figure of George Lucas walking towards me.

George: Rhett. Rhett. You must move on. Stop blogging about Star Wars. Who gives a crap about the g-forces on the Millennium Falcon or walking inside of a space worm? I don't care and I wrote this stuff. Really, it's just a movie. It's not a physics homework assignment. Me: I don't see a problem with my posts but I do see a problem with some of the physics in Star Wars. I'm not saying I don't like the movies. You know I think they are awesome. George: Well, just stop with the Star Wars physics posts. You are starting to ruin the movies. Me: Now you know how I feel when you go back and edit Star Wars IV to make it look like Greedo shot at Han and then Han fired back. Anyway, I think I'm finished with the g-forces on the Millennium Falcon. There are no more scenes to analyze. That asteroid scene was my last hope. George: No. There is another. Really, there is. What about the scene right after the Falcon escapes the space worm? The ship is moving away from a Star Destroyer and then turns around. It seems like you could analyze the acceleration in that scene too. Me: Maybe I will just leave that as a homework assignment.

One last note. I would like to report that I can now spell Millennium Falcon without having to look up the spelling online.