Continuing on from Part 2: The Nacelles


How Maneuvering Will Kill Everyone Aboard

In order to understand this next part of the “USS Enterprise = Deathtrap” equation, it’s important that we understand two major forces in physics; inertial mass and center of mass.

Inertial mass is the mass of an object measured by its resistance to acceleration.

Sounds simple enough right?  Everyone has experienced it to some degree.  Imagine having to push a Buick out of your driveway; even though it’s on a level surface and it has wheels to reduce friction, it’s still a pain!  It’s a pain because of its inertial mass.  When people think “mass” they often mistake it for “weight”.  In truth, however, it’s much harder to describe what defines “mass” because scientists are still working on that definition themselves.  What they do know is that mass isn’t so much about how much something weighs as it is about how much of it is there.

So what if we put the Buick in space?  Easy to push, right?  No, actually.  Just because the “weight” of the car is gone doesn’t mean its mass is gone.  There’s still just as much car as there was before, and you’re still the same weakly human you were on the ground.

No, I am not calling her "A Buick"

Now with this in mind, imagine that the Buick is actually roughly double the size of a Nimitz-class  aircraft carrier.  Got it?  Good . . . now get out and push.  That’s the kind of mass we’re talking about when it comes to Star Trek ships.  Of course, this isn’t unique to Star Trek as nearly every other science fiction as well.  So instead of focusing on how all of sci-fi is wrong, we’re going to refocus on just the ships of the Federation.

Remember those stress points we talked about with the nacelles?  They were considered stress points because when the ship moved, the inertia of such movement would cause those areas to flex and warp.  That was just forward movement . . . trying to move the bow up or down would be worse.  See, inertial mass doesn’t just resist acceleration, it also resists changes in velocity as a whole.  If it’s stationary, it wants to stay stationary.  If it’s moving at 100MPH dead ahead, then it wants to STAY moving 100MPH dead ahead.  Suddenly banking to avoid an attack is a sure way to shear the ship in half.

The overall shape of the ships causes issues too.  The length of the ship compared to its beam (width) ensures that it’s going to take herculean efforts to increase or decrease its inclination while making it able to roll faster than you can control.  The Enterprise-D’s overall design made her as wide as she was long which conceivably would have helped with maneuvering  when compared to  the previous ships.  However, the change in design also messed with . .  .

Center of mass or barycenter of a body is a point in space where, for the purpose of various calculations, the entire mass of a body is concentrated.

Center of Mass isn’t a term used by the everday person a whole lot.  In school we learn it as center of gravity.  In space, that doesn’t make much sense since gravity is no longer a uniform field as it is on Earth but the forces that make it important still exist.  To determine an object’s center of mass, simply put it on a balancing point (or fulcrum) and move it till it’s balancing on its own.  Now do it on all three axes.

If you’ve ever owned a model of the Enterprise D, you know what happens when you put it down; it dives straight forward.  This wasn’t lost on the producers of the show, who had the worst issues trying to find a way to rig it for camera armatures:

“The armature was was really a difficult problem, which had to be solved right away, because, of course, everything is built around the armature. The old Enterprise has a nose mount in the center of its body–no mounts are on the dish, but right about the center of gravity, there are mounts going out each side and the bottom and the rear, The new Enterprise is generally a flat ship since the engine nacelles don’t stick up and the saucer is elliptical; the ship is very nose heavy because of the enormous elliptical dish, which puts the center of gravity somewhere up in the neck and dish area. We had to come up with a a really complicated armature that would allow us to shoot the ship from all positions–both together and then split apart, because this new Enterprise is essentially two ships. In concept, we would be dealing with 12 mounting points.
Ease came up with a pretty simple method that involved mounting the dish on the top or bottom and making the armature strong enough so that even if you grab it at one end with the other end of the ship just cantilevered, it would still hold. On our other ships, the saucer has an edge which is about two or three inches thick, so it would be possible to pop a panel off and run a mount arm in. But on this design, the saucer tapers down to almost a point–maybe a quarter of an inch. To run a mount arm in, we would need to do much more than pop in a panel, we would have to take a section out of pie out, and then we couldn’t shoot the model from the top or bottom.
Ease designed a mount arm that emerges out of the dish’s top or bottom and makes a right turn, it is structurally sound enough to support the entire ship–and this [is] the heaviest ship we ever built. There is another mount at the neck and others at the bottom, the rear and the front of the body. So, I guess there are six different mount points that allow you to shoot from any direction.” (The Official Star Trek: The Next Generation Magazine, issue 2, pp. 31-32)

This means that any RCS (Reaction Control System) thrusters that need to move a ship like this need to do so in relation to the ship’s barycenter.  The further something is away from that barycenter, the more stress it’s going to be under when the Captain needs to make a fast turn.  In layman’s terms, it’s like using a bullwhip; you only moved the handle a couple feet, but the tip just traveled 12 feet in the same time causing it to break the sound barrier.  Now we have a ship that’s by all accounts HUGE, making a turn while traveling at 0.25 c (25% the speed of light, or “Full Impulse”) and the poor rear section is literally tearing itself to pieces because of the incredible stresses caused.

Remember that this is the same rear section with the barely shielded “death in a bottle” and supporting the ultra-dense warp coils that MUST remain in perfect alignment for the Warp Fields to form.

All of this is forgetting the central “neck” of the ship as well.  Despite the fact that it’s closer to the center of mass than the rear of the ship, it has the worst job because it still needs to support the entire rear of the ship.  For a better understanding of why this is, let’s try a thought experiment.  Instead of the Enterprise as it currently looks, let’s think of her in terms of mass and how it’s laid out from above.

Even in MS-Paint, my art skills leave much to be desired.

Now imagine that this is all one homogeneous rubber toy (no, that’s not dirty).  You hold it by the saucer section and shake it back and forth . . . what happens?  How about if you hold it by the Stardrive/Engineering hull and do the same thing?  In both cases, the entire thing flexes at the same point; the neck.

“But Zuke,” you say. “The Enterprise isn’t made of rubber! It’s made of  a fictional metal alloy!”

True, but just because rubber is flexible and metal isn’t doesn’t mean that the same forces don’t apply to both.  Rubber will bend and flex to dissipate these forces.  Metal shears, bends, and shatters.


How Do We Fix It?

Funny enough, Star Trek already has . . . just not for the humans!  There are many ships in science fiction that sidestep many of these issues (as best they can anyway) and more than a handful of them are already in the Star Trek Universe.  The Klingon “Bird Of Prey” (all models) actually manage to keep their design relatively balanced in terms of maneuverability and mass.  The more modern “Saber” and “Defiant” class Federation ships also try to balance things out but still fall short in our last area . . . .

The Details, or Part 4.


  • luxifer

    inertia dampeners, structural integrity fields? just saying 🙂

  • Yup! Right there with you. Be patient for part 5: Conclusion.

    Be sure to keep the thoughts coming, though! I’m sure I haven’t thought of everything.

  • You realize of course that your explanation of these “difficulties” is defined by the application of terrestrial physics right? The flaw…. the ship is in space, not on a planet…Extra-Terrestrial physics in a zero G environment with no resistance (thanks to that lovely deflector dish) means the application of energy/force required for any object, especially one with the ability to create and manipulate its own gravity and strengthen sections of the hull with the mere push of a button is substantially less then if done inside an atmosphere… With those crucial elements available a ship can be whatever size, shape or configuration you want it to be.

  • Thanks for your comments! It’s always funny when someone new stumbles across these posts.

    The thing about using the IDF or the deflector is that your argue them. It’s like saying “Everything works because of the ‘Ignore Physics’ button they installed in Season 3”. I love Star Trek tech, but it can’t be argued in terms of real world physics.

    Yes, you are right that we are working in a micro gravity environment. However, that doesn’t mean that all properties of mass are negated. The ship can create it’s own gravity within the ship, but that doesn’t mean anything to what’s happening to the outside. I mean, it should. But on the movies and TV shows, it doesn’t (can you imagine if the Enterprise’s 1G effects extended OUTSIDE the ship?! That’s enough force to keep the moon in orbit).

    I also pointed out that future materials may be strong enough to withstand these kids of forces. And yes, the magical IDF is build to withstand this anyway. But is it really the best use of resources to build a design that requires all of these safety measures just to make a course adjustment? You don’t thank your cars rollcage when you just want to back out of the driveway. There are other ships in Star Trek that are a better design that really would be more viable in terms of CoM.

  • Eric

    This is great! I’m a big Star Trek ship nerd (for lack of better word)… I do appreciate their details and find them fascinating, if a bit preposterous in terms of physics.

    I have two gripes: Reactors/Nacelles – I’ve wondered why the nacelles aren’t more apt to be attached in the power feed (directly) from the Reactor(S). That’s plural! How often did the ship have issues because the reactor (single) wasn’t producing enough power or had an issue? Simple solution is to build more power sources right? Or is that too simple?! Imagine if a Sovereign had 4 reactors: 1 for weapons, 1 for shields, 1 for life support functions and 1 for warp drive. Couldn’t you delineate power from each? Why not? The original USS Enterprise CVN nuclear carrier had 7 or more reactors! Seven!

    And then there is the issue with weapons: So… I am to believe a 1 km x 1km x 1km Borg cube wouldn’t be completely obliterated by a single very high yield nuclear device? You know, similar to what we have in the Trident III missiles today? I realize explosive qualities are lost a bit in a zero G environment… but still the power unleashed by a Trident III warhead is beyond immense. Then remember that scene from First Contact where the Borg were bombarding a silo housing the ever important Phoenix… if those photonic/quantum weapons are more powerful than a nuclear device that area would have been blasted into oblivion. Did I miss something? I understand the issue of propelling a warhead, but with ships 600m in length flying at speeds beyond light I think something could be engineered.

    Those are my biggest gripes.

    I’m eagerly awaiting the Conclusion.