Possibly one of the most iconic moments of the Star Wars saga was the trench run on the first Death Star. However, I often see people criticizing this scene as being stupid tactics. To many the skimming of the trench to fire at the precise moment and angle so that the torpedo gets caught in the gravity of the Death Star and falls into the exhaust port starting a chain reaction, seems a bit to overcomplicated when they could just dive bomb the exhaust port and thus have a straight shot at the exhaust port. So why did the alliance opt for the more complicated strategy? Well because of a little thing called Trench Run Disease.
So what is Trench Run Disease? Well it is a characteristic shared of Imperial capital ships that allow snubfighters to better survive long enough to deliver their payload. But why does this work, and how? Well it is a combination of things that all contribute to this weakness. First being, like I have covered in my article on why the Star Destroyer replaced the Venator, the Empire no longer saw Starfighter combat as the most important aspect of naval warfare. Instead they favored heavily armed capital ships. As a result medium and heavy turbolasers cannons were favored over point defense and laser cannons. This is an issue as while the former are good at dealing with other warships, and if they did get a direct hit would absolutely shred through a snubfighter, their rate of fire is simply too slow to be considered effective. While the latter aren’t as powerful but provide a near constant rate of fire to increase the chance of a hit. As for exact figures on the rate of fire of the larger turbolasers I could not find anything. Though reviewing the footage from A New Hope there was an XX-9 heavy Turbolaser fire 6 times in a 3 second interval which would equal around 120 rounds a minute. For comparison, a 1.1”/75 gun used by the Americans as an anti aircraft gun in WWII had a rate of fire of 150 rounds a minute. Now that doesn’t sound like a big difference but consider that the 1.1”/75 was considered to be one of the worst AA guns of the war, and it still has a higher rate of fire. Fighters are fast and hard to hit, to compensate for this you need to be able to throw as much fire at them as possible. Or simply put more rounds per minute equals more fighters shot down.
Now this would not be as much of a problem, as Imperial ships and stations are loaded with so many turbolasers that their individual rate of fire is compensated by the sheer number of them that can fire at enemy fighters. So on their own, a slow rate of fire is not enough to make Imperial ships weak to
fighters. It is the close proximity of the fighters taking advantage of the Trench Run Disease. More specifically it is two characteristics of these defensive turrets that makes close proximity so deadly.
Now I want to first warn those reading this that in order to describe one of them some math is required. Don’t worry it is some basic geometry but still I apologize in advance. So let’s say you are stationary and are attempting to fire a weapon at a target that is 10 meters away from you. Usually no problem, but what if this target is moving at a rate of 5 meters per second directly perpendicular from you, and you were solving for how many degrees you would have to adjust your aim in that second to keep your firearm in a position to hit them when you fire. You would essentially be solving the angle of a right triangle with an opposite value of 5 (the running speed) and an adjacent value of 10 (how far away the target is).
To solve you would just have to take the tangent inverse of 5/10 which would be about 26.57 degrees. No what if the target was closer to you but moving at the same speed, say it was only 5 meters away? No problem same formula but instead you would be taking the tangent inverse of 5/5 which would be 45 degrees. So by reducing the distance between you and the target you have essentially increased the angle at which you have to pivot your aiming point in that 1 second to stay in line with the target, assuming said target is moving at the same speed. (Math over). Yes at longer ranges you would
still have to lead the target a bit to get a hit but that would not increase the amount you would have to rotate that much.
So what this means in the context of a turbolasers turret attempting to shoot down those pesky snubfighters, is that the closer said snubfighters are to the turret, the faster it has to rotate in order to track it. The problem being that big heavy turbolasers turrets don’t rotate very fast as they are heavy by nature and take a lot to move. That means that a snubfighter, if it gets close enough can essentially fly faster than the turret can rotate to get a bead on it. Yes being that close also makes the shot for the turret really easy, this is offset by the fact that the window that the turret has to make that shot is short. And again, they can’t fire that fast so they pretty much have in this scenario quite literally have 1 shot at it, and not a very high percentage shot at that.
Finally, by flying so close to an enemy ship you effectively reduce the amount of defensive batteries that can shoot at you. How is this possible? Well simply put the ship itself gets in the way. On an ISD for example, by flying on the port side sticking close to the hull, the entirety of the starboard side batteries would be unable to shoot at you due to the triangular shape of the dorsal side of the ship. Additionally, some turrets if they are located higher on the superstructure may not fire even if they are able to since any missed shots would hit their own ship. Or you could fly in a sweet spot where a turret simply cannot traverse its guns low enough to be able to hit you. These can often stack on top of each other leaving far less guns able to shoot at you than would be possible if you were farther out.
Getting back to the example of the Death Star trench run, and taking into account these factors it is easy to see why the Alliance went with this kind of tactic. By skimming the trench they took advantage of the defensive turret’s slow rate of fire, inability to keep a target in their sights, and the limited amount of firepower that could get a clear shot at that range. A dive bomb would have made the shot easier, but would also leave alliance fighters and the torpedoes they shot an even easier target (as intercepting Proton Torpedoes was a viable tactic for defensive fire making them more effective at shorter ranges to give the enemy less time to shoot them down.). Therefore, they took the safer route which only saw high casualties because of the defensive fighters, not the defensive batteries. But that is a topic for another day.
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