On my 8th birthday I opened up a large box to find a Nintendo 64. A few weeks later I opened up a smaller box to find a game about the adventures of a space-faring fox. A few years later the Internet helped create a meme that became larger than the game itself.
“Do a Barrel Roll!” spun its way into pop culture in 1997, when team member Peppy Hare encouraged the player in Star Fox 64 to deflect incoming enemy barrages by performing a horizontal spin. Peppy’s urgent advice lived on in the minds of nerds everywhere—an inside joke for gaming enthusiasts. The saying eventually became a meme, with the zenith of its popularity coming after Google used the phrase to make its whole search page do the roll.
While gaming aficionados laughed, aviation aficionados cringed. It can’t be stated more clearly, you never did a barrel roll.
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“Do An Aileron Roll!”
In aviation, barrel rolls are nothing new, and have long been one of the many staples of air shows. To perform a barrel roll (it’s a bit more complicated than tapping Z or R twice), you maneuver the aircraft in such a way so that it looks like you are going around the outside of a giant cylinder in the sky, while spinning the plane 360 degrees horizontally. What we see in Star Fox 64 is what we would expect from a programmer who simply guessed that a barrel roll is a simple spin. It turns out that this kind of horizontal spin has a name in aviation too: an aileron roll. It’s not nearly as easy to say, but at least it’s accurate (I should note that in a follow-up game, Star Fox: Assault, that you can do a corrected barrel roll.)
But there’s something else wrong here. How does spinning a ship help it deflect enemy projectiles? Does the maneuver have any basis in reality, and would it do more harm than good?
The Statistics of Spin
We can see from the game that the original intention of the roll was to deflect incoming plasma shots (they are travelling too slowly to be considered laser shots). But could even a vigorous spin increase deflections? We could look to our own attempts to deflect the enemy.
After World War II, militaries around the world started outfitting their tanks with sloped armor—metal plating crafted specifically to deflect deadly armor-piercing shell and bullet strikes. Technological progress chugged along however, and before long sloped armor fell out of favor for armor that could absorb impacts and reduce overall damage. But who knows, maybe sloped armor is more effective against the plasma projectiles in Star Fox 64.
Looking at the design in the game, Fox’s ship certainly looks like it has armor meant to deflect projectiles similar to the WWII tanks (though this probably has more to do with the graphics capabilities of the Nintendo 64). So, if Fox’s ship did have sloped armor, would Peppy’s incessant nagging to “Do a barrel roll!” (in reality an aileron roll) really help?
Unless there is some kind of additional shielding that could be spun around to hit a projectile out of the air before it hits Fox’s ship, which we don’t see, we have to assume that Fox’s roll is trying to increase the likelihood that his deflecting armor will save him. It’s a game of angles.
The benefit of sloped armor is that it is crafted with certain projectile angles in mind, and can deal with those angles. For example, a tank in WWII facing off against another tank is more or less going to deal with a projectile travelling parallel to the ground and aimed at the hull of the tank. If the engineers did it right, the armor handles the assault. However, if you change the angles at which projectiles hit the armor, the armor becomes much less effective.
Imagine skipping a stone on a quiet lake. As a kid, perhaps you spent an hour or two refining the right way to throw the smooth rock. You noticed that you needed to strike a glancing blow on the water—the angle you threw it at determined if you skipped the stone. But if you throw the stone directly down into the water, or at the wrong angle, it quickly sinks. Likewise, even sloped armor will take a direct hit and deflect nothing if the angle is wrong.
The right angle depends on where the projectile is coming from. In Star Fox 64, you are shot at from above, below, and straight on, and Fox often spins his way through a maelstrom of plasma. But how safe Fox will be depends on his ship’s shielding. Unfortunately, this is where it gets complicated. Just how armored was Fox’s ship, and at what angles is it protected.
We could assume that Fox has a state-of-the-art ship, protected by deflective shielding meant to take a hit from any direction. If that is the case, spinning around a horizontal axis doesn’t change anything—the bottom of the ship could deflect just as well as the top. However, if only the top (or the bottom) of Fox’s ship was shielded, like the WWII tanks or how it appears in the game itself, probability comes into play.
There are two important scenarios for a half-shielded ship: assuming that the projectiles will be coming in at random angles, or assuming that the pilot can sense the angle of fire and correct for it. If the incoming fire is random and you perform a spin, you have a 50% chance to deflect the hit with the shielding (given a 360 degree roll). But you have a 50% of deflecting a random shot if half the ship is protected in the first place! With random fire, spinning the ship is useless for deflection.
Maybe Fox was adept enough to recognize incoming fire and spin the ship accordingly. If a plasma shot comes from below, and Fox spins, he has a 50% chance of deflecting something that would otherwise be a direct hit. The same is true for any combination of top/bottom shields and top/bottom fire (the straight on hits do not matter because spinning would not change the angle).
The gameplay of Star Fox 64 best fits the “random angle” situation. You can be hit from many angles simultaneously, and therefore spinning gives you the same chance of deflection as flying steady. The best ship design would then be the one that could deflect multiples angles simultaneously, perhaps something resembling a giant cone. Spinning would then make no difference, unless you are a fan of showboating.
The real application of the Star Fox spin would be to make the wings harder to hit. Though the fuselage of Fox’s fighter would remain in the same place, spinning around a horizontal axis at high speed would reduce the chance the enemy hits a wing—given that the enemies were aiming for them. Aiming for the wings isn’t all that far-fetched either, as what first deteriorates in the Nintendo 64 game are the ship’s wings, seriously hampering further efforts to stick it to Andross.
Memes don’t go viral based on their scientific accuracy (though the term “meme” was coined in a scientific context by evolutionary biologist Richard Dawkins), but I owe it to all the geeks that loved Star Fox 64 like I did to correct the “Do a barrel roll!” phrase. Maybe there was a translation error, maybe the developers didn’t care to look up what a barrel roll actually looked like, or maybe Peppy had it out for you and was trying to get you killed (he did have a weird thing for Fox’s father…). In any case, if you are nerdy enough to get the meme, you should be nerdy enough to accept my pedantry. It’s what Slippy would have wanted.
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Screenshot from Nintendo’s Star Fox 64