On Starfleet vessels, Jefferies tubes are internal maintenance conduits that are used to provide crew access to various ship's systems. In emergencies they're also used for moving around the ship if turbolifts are not functional. Doors within the Jefferies tubes can be sealed for safety or security reasons. It should be noted that on all ship displays of internal structure Jefferies tubes are not displayed, and in some cases show no sign where they could actually fit within the ship. During the 22nd and 23rd century, Jefferies tubes were usually referred to as access tubes, access tunnels or service chutes. It wasn't until the 24th century that their official name was firmly established, though some officers referred to them as "service crawl-ways" (TNG: "Disaster").
During the 22nd century, starships were outfitted with long and small service tunnels what would later be known as Jefferies tubes.
They were hard, cold, cramped and poorly lit. Tunnels on some ships joined at the variable gravity "sweet spot." (ENT: "Broken Bow")
The NX ships had vertical tubes to help their crew manually reach decks above them or below them. These tubes were circular from one end to the other. Each tube was equipped with a single one-way ladder for crewmen to climb or descend. The ladders had dim lights behind them so the crew could see where to step.
The horizontal tunnels were not very different from the vertical ones. They were also circular and narrow. Crewmen had to bend their knees and crouch down at a bent posture while walking inside these specific tubes. A majority of the tube's space was filled with long and thick engineering pipes that went from one end to the other. These tubes were lit from the floor so a person could follow a path.
In the 23rd century Jefferies tubes were still round and small, but they were better lit and weren't just a means to get around. They served many different functions and purposes. It was not uncommon to find many technicians and engineers tinkering inside them.
Many diagonal tubes were scattered all throughout starships. These tubes were always densely connected with important system controls, relays, various conduits and vital engineering circuits. Some of these tubes led to crawl-way junctions, while some even continued on inside a nacelle pylon to one of the ship's actual warp nacelles. At the entrance of each tube were two red bars so a crewman could pull him or herself inside. A soft, yet strong light was always emitted from the top and filled the entire tube. Certain tubes had multiple functions, while others had single functions like the tubes which were only designated engineering circuit bays. Each diagonal tube was equipped with stairs for crewmen to walk up or down. (TOS: "Charlie X", "The Doomsday Machine", "Journey to Babel"; ENT: "In a Mirror, Darkly, Part II").
The vertical tubes on a starship, also known as gangways, allowed manual access to decks both above and below. These particular tubes were easily accessible in the open hallway alcoves located on every deck. On the walls of these tubes there was a reflective material that perfectly illuminated the entire tunnel. The tubes were equipped with a single "three-way ladder" to allow more than one crewman to climb or descend. (TOS: "Amok Time")
The horizontal crawl-ways on starships allowed manual access to various parts of a starship. These tubes were also densely connected with important system controls and vital engineering circuits. Some of these tubes even led to the matter-antimatter reaction chamber. Every few feet, a bright light could be found shining down. Crewmen usually had to crawl while traveling in some of them due to the cramped size. Other horizontal tubes were still cramped, but crewmen could still walk freely up straight in posture. This was especially true late in the 23rd century. Late in the 23rd century, the horizontal tubes were extremely well lit with lights coming from both above and below. (TOS: "That Which Survives"; Star Trek V: The Final Frontier)
On a starship, the Jefferies tubes had junction service crawl-ways. They served as interconnected points linking all the different tubes. On Constitution-class vessels, these junctions also gave access to critical starship systems like plasma flow regulators and warp and power relays. (ENT: "In a Mirror, Darkly, Part II")
During the 24th century, Jefferies tubes became more simple, less intricate and not as thoroughly filled with vital systems.
The vertical tubes on starships allowed manual access to decks both above and below, which were labeled inside these particular tubes. Dim lights were located behind the main ladder and other lights were found on every deck. These tubes were equipped with a single one-way ladder for crewmen to climb or descend.
The horizontal crawlways on starships allowed manual access to various vital parts of a ship or station. Dim lights were located near the floor and on each side of the tube. Crewmen usually had to crawl while traveling in them due to the cramped size. Inside these tubes were removable panels to important system conduits and engineering controls.
On 24th century starships, all Jefferies tubes had junction service rooms. They served as interconnected points linking all the different tubes. Every room had exposed conduits on the walls, sometimes with panels to access various power conduits or relays.
- TAS: "The Practical Joker"
- "Learning Curve"
- "Fair Trade"
- "Before and After"
- "Worst Case Scenario"
- "The Gift"
- "Scientific Method"
- "Year of Hell"
- "Waking Moments"
- "The Killing Game, Part II"
- "Course: Oblivion"
- "Someone to Watch Over Me"
- "The Voyager Conspiracy"
- "Blink of an Eye"
- "The Haunting of Deck Twelve"
- "Renaissance Man"
- Star Trek: First Contact
The Jefferies tubes were named in honor of Matt Jefferies, the designer of the original USS Enterprise and the Production Designer of Star Trek: The Original Series who later became the Art Director. (Star Trek Encyclopedia) The name was originally an in-joke, but came to be mentioned a number of occasions in The Next Generation. The term was first used in "The Hunted".
The access tubes have changed appearance many times in the past forty years, while still maintaining their basic function for both the series and films. The tubes were commonly used as a last minute deus ex machina, whether it was a relay circuit inside that needed to be repaired, or a straightforward means of physical escape.
The most unusual variation of the Jefferies tube was a vertical tube shown in the original Star Trek series. This access tube had a "three-way" ladder that allowed three people to climb simultaneously. This was no doubt convenient during red alert when crewmen needed to get to battle stations quickly. Unfortunately, this concept was never expanded upon, so we never saw a four, or even a six sided hexagon-shaped ladder. Instead, the Jefferies tubes ladders in the 24th century were only capable of supporting one individual.
An in-joke reportedly appearing in the Jefferies tube sets on the original Star Trek series (although written so small as to be invisible to the audience) are labels on the pipes marked "GNDN". This stands for "Goes Nowhere, Does Nothing." The marking also appeared on various sets for the Star Trek films.