Star Trek has many high-concept ideas across the franchise's near-60-year history. In fact, because of its longevity, many commonplace concepts in science fiction were created or brought into the mainstream by the series. On such idea, starship shields and deflector screens are deployed better in Star Trek than possibly anywhere else in the genre. On the surface, it may seem like they "never work," but the shields used to protect ships work perfectly … the way the storytellers need them to.
In Star Trek: The Original Series, the 1960s-era budget and technological limitations meant producers and directors had to be creative to showcase ship-to-ship space battles. The most iconic way they created visual drama during them was with the "camera shake" technique. The actors would sway in their chairs or throw themselves violently across the set, depending on how well the shields and deflector screens were at blocking alien ships' attacks. As with anything in the episodes, the main goal is to create exciting visual drama for audiences and keep them tuned in. Yet, good science fiction creates, at least, an internal logic for how their significantly advanced technology (thus, indistinguishable from magic) works. But it goes beyond saying that Star Trek's shields are made using a "graviton" effect or that it's routed through the ship's "deflector dish." Shields and deflector screens have to work in the way the writers need them to while still making rational sense in the world of Star Trek.
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How Shields and Deflector Screens Work in the Star Trek Universe
Over the nearly six decades of Star Trek stories, the terms "shields," "deflectors," and "deflector screens" are used almost interchangeably. Shields and "screens" are seemingly the same technology, with the latter term being written off as a language quirk on Kirk's Enterprise. In the 1960s, shields may have conjured an image of armor plating of some kind. A screen better conceptualized the idea of a sci-fi force field that reduced incoming damage to the ship. The deflector, however, was a very well-considered concept. Even in the mid-1960s, series creator Gene Roddenberry understood a ship flying through space at a high rate of speed would encounter "space dust" that would pierce through the hull like a microscopic bullet. So, the deflector dish sends out a pulse that pushes dust, debris, or other smaller things out of the ship's way as it travels. It's since evolved to be used as a shield during combat and even a weapon in its own right.
Yet, keen Star Trek fans likely notice that even when "shields are at 80 percent," the ship still seems to take damage. Sparks and crewmembers fly from the impact, and if the budget allows, hull damage can be seen on the ship. This is because the shields, whether on their own or amplified by the deflector dish, don't negate damage. In some cases, they do (whenever the attacking aliens don't need to be a threat within the story). Yet, usually, the energy field that surrounds the ship in a bubble simply reduces damage. Think of it like a video game with a "block" feature that still causes the health bar to drop. It's not as much if the player didn't block, but it doesn't protect them from all damage. This is why when shields are up, Star Trek ships are still battered by enemy weapons, mysterious forces, or energy fields in space.
The shields work on a percentage countdown where a higher number is better. Even with shields at maximum (during a climactic battle, at least), Star Trek ships feel the brunt of phaser blasts and photon torpedoes. Adding the deflector dish allows some of that damage to be reflected into space. Still, even as the shields fall (dramatically) to 50 percent, 20 percent, and so on, they still protect the ship better than they would without them. As evidenced by a number of the series, without any shields, one or two photon torpedoes could ultimately destroy a starship down to the atoms.
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How Star Trek Storytellers Use Deflector Shields and Screens
While some of the more sci-fi purists in the audience may feel this is a cop-out, deflector screens, and shields work only as well as the Star Trek storytellers need them to. There are countless episodes where the shields are working fine one second and, in the next, the ship has lost all power to them or the deflector. The driving force behind these decisions isn't a lack of care about "canon" or anything like that. They are, instead, used to create the most interesting and dramatic circ*mstance in the story. Sometimes, the captain will push on, even though shields are dangerously low. This is either to create a heroic moment or, in rare cases, allow another character to chastise them for risking the ship for the wrong reasons.
In its second and third waves, Star Trek has employed experts in both science and the franchise canon in an effort to keep things consistent across the series and eras. Yet, these things serve the stories being told, not vice versa. Deep Space Nine's USS Defiant had "ablative armor," while the NX-01 from Enterprise had "polarized hull plating." These things are technically different than shields and deflector screens. However, they work functionally the same way. How well the work and how much damage the ship sustains depends not on the technical specs of the shields, but the needs of an individual series or story. While the storytellers endeavor to bring consistency to the universe, everything works better when the specific episode or film takes precedence over the "rules" of the technology.
Some level of suspension of disbelief is required of Star Trek viewers, especially where pretend technology like energy shields or deflector screens are concerned. Despite the needs of different stories and eras, these damage reduction elements are applied with relative consistency. Yet, suppose one battle is particularly harrowing or, conversely, far too easy for the crew. In that case, audiences should look for the reason the story requires that rather than taking to social media to lambast the storytellers for getting it "wrong."
