What Are Inertial Dampeners? The Oblique Star Trek Technology Explained

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Welcome to Trekspertise, a series where we break down the technology, history, details, and decisions that make the Star Trek universe so complex — and so fun.

Remember the inertial dampening field? Of course you do. They bring it up all the time on "Star Trek."

What would "Star Trek" be without multiple reams of impenetrable multisyllabic technical jargon? Technobabble is so common on "Star Trek" that fans have taken to calling it "Treknobabble," and Trekkies tend to love it because it gives the franchise a certain degree of scientific verisimilitude. Unlike something like "Star Wars," "Star Trek" actually pays attention to physics and the realities of space travel, leading the show's creators to invent imaginary technologies that can force ships to travel faster than the speed of light. 

As the franchise progressed and more laws of physics were explored, the fictional technology became more and more elaborate. For "Star Trek: The Next Generation," Rick Sternbach and Michael Okuda even authored an invaluable sourcebook called the "Star Trek: The Next Generation Technical Manual," which explains just how warp engines operate, how replicators work (you eat your own poop!), and the function of the Enterprise-D's main deflector dish. 

The book also goes into detail about the intertial dampening field, which is, in brief, an invisible shield around the Enterprise that absorbs inertia. It's the thing that prevents the crew of the Enterprise-D from being crushed against the back wall when it travels forward at sublight speeds. When traveling at warp, the crew is generally protected by the warp field, so the intertial dampening system is typically more active when traveling at impulse speeds. As Sternbach and Okuda themselves pointed out, the tremendous accelerations on "Star Trek" would instantly transform the crew into "chunky salsa" without some kind of protection. 

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According to the "Technical Manual," there are actually two invisible shields that are always operating on an active, moving starship. There's the inertial dampening field, or the IDF, and there's the structural integrity field, or the SIF. If the IDF were to malfunction, a starship would only be able to travel at speed the humans inside could handle, and given the vastness of space, they wouldn't be able to get very far. There are six primary IDF generations of the Enterprise-D on "Star Trek: The Next Generation" and six backups. It's vitally important that thing is always humming. As stated in the "Technical Manual": 

"[T]his field is distorted along a vector diametrically opposed to the velocity change. The IDF thereby absorbs the intertial potential, which would otherwise have acted upon the crew."

The field, it seems, changes shape depending on the speed and heading of a starship, thereby protecting the crew at all times. Of course, this technology is completely imaginary. As we all remember from physics class, inertia needs to go somewhere; it can't just be stopped. On "Star Trek," though, the showrunners realized that traveling at blazing speeds would create inertia problems and invented the IDF to handle it. 

The field, in brief, produces artificial "counter-acceleration" to match the force that is meeting it head-on. This isn't so far-fetched when you realize that most "Star Trek" vessels can magically generate their own gravity that keeps the crew stuck to the floor (although we asked a real-life astrophysicist, and he corrected many things about interstellar travel as seen on the franchise). Why not throw some of that gravity forward to match a natural acceleration vector comin' straight at 'em?

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Of course, if there are intertial dampeners in place, then why are there so many scenes on "Star Trek" wherein the crew is tossed about the bridge as the entire ship shakes? Surely an IDF would also absorb any minor jostling that a ship would undergo, right? Even if the USS Enterprise were hit by an enemy photon torpedo, the IDF would be able to absorb any "knockback" the ship would encounter, right?

It turns out the "Technical Manual" accounted for the Enterprise's shaking by explaining that there is a very brief lag in the shifting on the IDF's field geometry. Essentially, it takes a split second for the IDF to adjust to sudden course changes. The delay is only 295 milliseconds, but that's enough for a ship the size of the USS Enterprise to shudder under enemy fire. Whenever the Enterprise makes very sudden shifts in direction — whether through a battle or just a sudden and unexpected sharp turn — the IDF will lag behind a bit, and everyone will feel it. Luckily it's rarely more than just throwing people to the floor. Ordinary course corrections can be predicted, and the IDF will adjust itself accordingly. 

The writers of the "Technical Manual" did admit, however, that the shaking of the Enterprise was included for dramatic reasons. It's more exciting for the audience if a starship is under attack and it shakes and jostles in front of their very eyes. The "delay" conceit was added to cover for a filmmaking decision while also trying to keep the tech on the show consistent. Technological limitations are vital for the drama in "Star Trek."

And if humans ever do invent faster-than-light travel, let's hope they also have intertial dampeners in mind.