In this post I’ll be proposing a model to understanding how Star Trek warp drive works. In doing so, I’ll be attempting to reconcile the way the TNG Technical Manual describes warp drive with the idea that warp drive somehow takes advantages of shortcuts through real space by warping space around the craft, yet still experiences inertial effects.
I want to point out at the outset that I am not proposing anything analogous to the Alcubierre drive that many fans seem keen on equating with Star Trek warp drive. My objections to conflating the two are laid out here. Ultimately, this model involves the ship actually moving at FTL speeds although spacetime distortion is involved.
I also fully admit I’m not a physicist, so I may - probably - have gotten many things wrong, even with the made-up science I’m going to talk about. I’d appreciate any discussions and suggestions to refine this model, even ones that outright say it’s rubbish and implausible (as long as you be constructive and explain why, so I can learn).
So let’s begin.
How Warp Drive deals with Relativity
To recap: the basic obstacle to superluminal or faster-than-light travel is Einstein's Theory of Special Relativity. Special Relativity says that as the velocity of an object with mass accelerates towards the speed of light (c), the mass of that object increases, requiring more and more energy to accelerate it, until at c, that object has infinite mass, requiring infinite energy to push it past c. In fact, Special Relativity says that nothing with mass can reach c - photons are massless and can only travel at c.
The first publicly available description of how Star Trek warp drive gets around this came from the licensed Star Trek: The Next Generation Technical Manual (1991). At page 65:
WARP PROPULSION
The propulsive effect is achieved by a number of factors working in concert. First, the field formation is controllable in a fore-to-aft direction. As the plasma injectors fire sequentially, the warp field layers build according to the pulse frequency in the plasma, and press upon each other as previously discussed. The cumulative field layer forces reduce the apparent mass of the vehicle and impart the required velocities. The critical transition point occurs when the spacecraft appears to an outside observer to be travelling faster than c. As the warp field energy reaches 1000 millicochranes, the ship appears driven across the c boundary in less than Planck time, 1.3 x 10^-43 sec, warp physics insuring that the ship will never be precisely at c. The three forward coils of each nacelle operate with a slight frequency offset to reinforce the field ahead of the Bussard ramscoop and envelop the Saucer Module. This helps create the field asymmetry required to drive the ship forward.
As we read here, Star Trek gets around Special Relativity by using a warp field to distort spacetime around the ship and lower its inertial mass so that the shaping of the warp fields and layers around the ship can push and accelerate the ship itself towards c with reasonable energy requirements. We see warp fields lower mass in TNG: “Deja Q” and DS9: “Emissary”.
Note that while ships are equipped with impulse drives, impulse operations are purely sublight in nature. In fact, the Tech Manual says that impulse doesn’t even enter into it at all when a ship goes to warp. It is the increasing strength of the warp field, shaped by the asymmetrical firing of the warp nacelles that produce it, that ultimately propels the ship without the need for impulse or reaction engines being involved. However, the ship still experiences inertial forces through this propulsion, necessitating inertial dampening fields (VOY: “Tattoo”, ST 2009).
As field strength (measured in units of millicochranes) increases, the lower the inertial mass gets and it becomes easier to accelerate towards warp (TMP). When the field hits a strength of 1000 millicochranes, the ship hits c, or Warp 1. Or rather, it straddles the boundary between 0.999c and 1.001c, spending no more than 1.3 * 10^-43 seconds at either velocity, so that it can apparently maintain velocity at c without the infinite energy requirements otherwise needed.
This is in contrast to sublight impulse engines which work in tandem with a warp field to take advantage of its mass-lowering effect. In the 23rd Century, it is implied the nacelles assist with impulse operations (SNW: “Memento Mori”), and in the 24th Century, impulse engines have driver coils built in which create a sub-1000 millicochrane warp field (TNG Tech Manual). In the 22nd Century, the NX-01’s impulse engines also had driver coils installed, but for the opposite reason - to increase the apparent mass of the ejected propellant as it exited the engines so it could provide greater thrust (USS Enterprise Haynes Manual).
What about subspace?
Now, to be fair, the idea of using a warp field to distort spacetime around the ship to propel the ship does sound an awfully lot like Alcubierre. But where warp drive differs is that unlike Alcubierre, the ship still feels inertial effects and is able to interact with objects outside of the warp field. In other words, the ship is still firmly moving through real space, not completely insulated and stationary within the warp bubble while space moves around it. Alcubierre’s bubble also doesn’t have a mass-lowering effect.
We know from the show that subspace is its own realm, with its own layers and domains (TNG: “Remember Me”) where even life can exist (TNG: “Schisms”). That has led to a suggestion that when a ship enters warp, it enters subspace which serves like a sort of hyperspace shortcut or wormhole. However, this has its difficulties in that it doesn’t explain why a ship in warp can still interact with objects outside of subspace as if it were in real space.
It is clear, though, that subspace has its own physical laws and its own special frame of reference, one of which is that you can exceed the speed of light in it: for example, the use of subspace radio which transmits at, in TNG times, Warp 9.997 (approximately 79,000c). In Star Trek, they generate subspace fields like we generate electromagnetic fields - in fact, the warp field is a subspace field.
But how does this relate to warp drive? Allow me a little sidestep into another franchise to draw a rough analogy.
Domain amplification and subspace
In the manga/anime series Jujutsu Kaisen, one of the magical techniques that the most powerful sorcerers use to battle each other is called “domain expansion”. This creates a closed area centered on the sorcerer enclosing their target, an area in which the sorcerer sets the rules, akin to a zone in which they receive a power buff. Inside it, if the domain is not countered, the sorcerer’s strikes will always hit the target. The sorcerer’s abilities are enhanced and various other things can happen depending on the rules that the sorcerer has preset into the domain.
Another use of domains is called “domain amplification”. This is not a full domain expansion, but surrounds the attacking sorcerer with a skin or bubble that has domain effects. It doesn’t use as much power as a full expansion, but is used to nullify any defensive techniques the target sorcerer might have, by imposing the attacking domain’s own rules against the technique. This still allows the attacking sorcerer to interact with things outside this domain bubble while taking advantage of some of its effects.
(All this will make sense, I promise)
Let’s imagine that real space is a domain that follows the rules that we associate with an Einstein/Newtonian universe, where relativity holds sway. Then we have another domain - subspace - where relativity can be ignored or at least circumvented.
So what if generating a warp field is like domain amplification, creating a bubble of a subspace domain that encloses the ship? This subspace or warp bubble is then shaped by the nacelles, which distorts space locally, allowing the bubble and the ship to be propelled along at FTL speed. This is because while inside the bubble, the rules of subspace apply, not the relativistic rules of real space. It therefore becomes possible to exceed c in that special frame of reference. And yet, the bubble is still strongly connected to real space, so the ship can interact with objects outside the bubble. This explains the existence of Newtonian forces like inertia, acceleration and momentum still acting on the ship, and the continuing need for inertial dampers at warp.
This tight coupling to real space is also why we can see “stars” streaking by while in warp (more likely dust particles in real space being accelerated as they are caught in the ship’s warp bubble). The visual change in post-DIS Trek where the outside of the ship looks more like a Stargate-ish tunnel can be explained away as what the interior of the warp bubble looks like stretched out, as the ship speeds along within it like a canoe on a river, being propelled by layers of warp energy within the bubble and also carried along by the current within the bubble itself as it cruises along.
Subspace and spacetime shortcuts
The existence of subspace as a separate dimensional realm also provides us with a possible solution for the disparity between what the TNG Tech Manual gives us as absolute c values for various warp factors and the speed of plot that we see on screen. Often, the time taken between star systems and sectors is much shorter than what we would expect given the warp factors quoted, if the ship did indeed travel at the c values given by the Tech Manual.
My suggestion is that subspace is not a one-to-one correspondence with real space, but exists in a “higher” dimensional plane where distances in subspace are much shorter compared to their real space counterparts. For example, what would take 200 light years to traverse in real space would be, say only be equivalent to 20 light years travel distance in subspace.
(I’m just tossing out figures here - I don’t obviously mean this as an exact ratio, and for all we know depending on the architecture of subspace the exact correspondence can vary widely, which again helps fit the speed of plot.)
So this further suggests that the TNG Tech Manual c values are meant to reflect speeds in subspace, or rather the ship’s velocity within the warp bubble, which translates to faster velocities and thus further distances travelled in real space. In effect the ship, by surrounding itself with a subspace domain, creates its own shortcut/wormhole through real space.
Conclusion
So, TL;dr: Star Trek warp drive works by surrounding the ship with a warp field, a bubble of subspace which both lowers the inertial mass of the ship and removes it from the relativistic requirements of real space. Propulsion is achieved by shaping the field, but within the subspace bubble the ship still moves and can act on real space as well as experience inertial forces. Additionally, the warped relationship of subspace to real space means that distances travelled in subspace move the ship much further in real space, and that warp factor velocities reflect the speed at which the ship moves in subspace rather than real space.
Thank you for your attention.