The Masked Man Reviews the Star Wars Movies

The Physics of Star Wars

Let’s just say that the physics of the Star Wars universe bears only a vague resemblance to that of ours. An in-depth analysis would easily fill a book. Still, before we get to the actual “movie reviews” section of this essay, I thought it might be interesting to discuss some of the more obvious ways that Star Wars physics differs from our own.

Spacecraft Performances and Related Phenomena:

The first thing you notice about spacecraft in the Star Wars universe is that the small ones seem to behave just like terrestrial aircraft, and the big ones move like terrestrial naval vessels. This is odd, since they’re usually moving in a near-vacuum, instead of air or water.

At this point, a brief discussion of how fixed-wing aircraft (as opposed to helicopters) fly seems to be in order. To fly, aircraft use their engines to generate thrust, which pushes them forward. Friction with the air creates drag, which will slow the aircraft – constant engine thrust is therefore necessary to overcome this drag and keep the aircraft moving forward at a constant speed. As air flows over the craft’s wings, it generates lift, which pushes the aircraft upward and overcomes the craft’s weight, keeping it from falling to earth. (If something happens so that the wings are no longer generating lift, the aircraft stalls. This has nothing to do with whether or not the engines are functioning properly; stalling occurs when the wings are no longer generating sufficient lift to keep the aircraft up.)

Exactly how wings generate lift is a surprisingly controversial topic. Still, there are some points that seem pretty clear -- basically, wings work by deflecting oncoming air downward, and thus pushing the aircraft upward. You’ve probably noted that aircraft wings are tilted so that the leading edge (the front of the wing, where moving air first hits) is usually rounded and is slightly higher than the trailing edge. So, as the aircraft moves forward, air hitting the underside of the wing is deflected downward. Since for every action there’s a reaction, as air hitting the wing is deflected downward, the air pushes the wing upward, helping to generate lift. Also, aircraft wings are typically shaped such that the top surface is convex. As oncoming air hits the smooth, rounded leading edge of the wing, it is split into two streams -- one of which travels along the top surface of the wing, and one of which travels along the bottom surface.

The Coanda effect is the tendency of a fluid to stick to a surface over which it is flowing. If the top of the wing is smooth-enough and if the trailing edge of the wing is angled downward, air flowing over the top of the wing sticks to the surface of the wing and is then deflected downward at the trailing edge, again helping to push the wing upward. (If the top of the wing is not smooth enough, instead of air traveling smoothly over the wing surface and then being deflected downward, turbulence is created and the plane may stall.) The faster the aircraft is moving, the greater is the force with which oncoming air is deflected downward, and so the more lift is generated.

Aircraft typically turn by using ailerons and rudders to push against the air they’re flying through. When you want your plane to turn left, for instance, you can elevate the ailerons on the left wing; this creates extra drag on the left side of the plane and slows it somewhat, causing the plane to turn left. It also has the effect of pushing the left wing downward, so the plane banks as it turns. To turn more quickly, you can elevate the ailerons on one wing and depress them on the other – this makes the craft bank even more sharply, since one wing is pushed upward and the other is pushed downward.

On a related note, since water is much denser than air, a ship moving through water must have a constant source of “thrust” too. Otherwise, friction between the water and the ship’s hull will soon slow the ship to a halt, relative to the water.

What does this have to do with Star Wars? Well, for one thing, there’s no particular reason that space-going craft should need wings, though most fighters and even larger craft in the Star Wars universe appear to be built with aerodynamics in mind. This is not necessarily a criticism, since the designers may have intended the craft to spend a fair amount of time operating in planetary atmospheres. It still seems odd, though.

Much less reasonable is the fact that Star Wars fighters bank just like terrestrial aircraft when they turn. There’s no reason why spacecraft should bank like that, because there’s no air to push against – ailerons and rudders wouldn’t work. Real spacecraft turn as the space shuttle does – by using rockets or other thrusters to push the craft in the desired direction. To be sure, if you put enough thrusters on your spacecraft, you could make it bank as it turns, but it would be a pointless waste of fuel.

Also, you’ve probably noticed that Star Wars spacecraft seem to have their engines going constantly while in space, which makes no sense. When in normal space, Star Wars spaceships don’t seem to be moving any faster than modern aircraft do, so there would be essentially no drag. This means that a spacecraft moving at speed “X” will continue to move at speed “X” if it shuts off its engines, since there’s no drag to slow it. As long as its engines are on, the craft should be accelerating. Oddly, though, we frequently see ships moving through space with their engines glowing brightly and therefore presumably generating lots of thrust – yet the craft don’t appear to be accelerating. For instance, as the Rebel X-wings and Y-wings approached the Death Star in A New Hope, we could clearly see their engines glowing, but they didn’t seem to be accelerating. (In fact, the attack leader told them sometime after this shot to accelerate to attack speed.) Similarly, in The Empire Strikes Back, we saw an Imperial stardestroyer approaching the planet Hoth with its engines glowing brightly, yet it didn’t appear to be accelerating at all.

Isn’t it odd that spacecraft in the Star Wars universe always agree on which end is up? “Up” is a virtually meaningless term in space, so why do spacecraft always orient themselves in the same plane? To be fair, this is probably due to viewer expectations more than anything else – many viewers would doubtless think it disorienting to see two spacecraft approach each other with Spaceship A “on its side” or “upside down” compared to Spaceship B. Supposedly, Gene Roddenberry (the creator of Star Trek) claimed that test audiences complained when he showed them footage of spaceships approaching each other while oriented on different planes.

Personally, I think it’d be neat if movies more-often dared to show us spaceships that actually moved like spaceships, and that didn’t pay any particular attention to their orientation. (The television series Babylon 5 showed us spaceships that generally moved realistically, but even the creators of B5 didn’t have the guts to show spaceships operating with different orientations.)

What is galling about Star Wars spaceships is that they’re asymmetrical – that is, they have definite “top” and “bottom” halves, which makes no sense at all for spacecraft, even if you accept Star Wars physics. In space, you have three complete degrees of freedom in your movements. This means you can approach ships from the front/back, from the sides, and from above/below! Despite this, you’ve no-doubt noticed that the fighters in the Star Wars movies virtually always attack capital ships from above, just as if they were terrestrial aircraft attacking naval vessels. Why not fly under the big ships to attack them, which they can certainly do? Why fighters don’t do this is even more inexplicable when you notice that the big ships appear to have few guns or none at all on their undersides. To say that this is a stupid design for a space-faring warship is quite the understatement!

At least some of the spaceships in the Star Wars universe use ion propulsion, notably the TIE (Twin Ion Engine) Fighters. Ion engines could be used to boost spaceships to quite impressive speeds, it’s true, but they would have terrible acceleration. Somehow, I doubt the Empire would be building interceptors that take weeks to reach speeds chemical rockets could achieve in seconds!