Jefferies Tubes

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.

Jefferies tubes can also be used for fitness training exercises. (VOY: "Learning Curve")

Geordi La Forge sarcastically remarked about Starfleet engineers claiming Jefferies tubes being "easy access." (TNG: "Power Play")

22nd century

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.

23rd century

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 nacelle. At the entrance of each tube were two red bars so a crewmen 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 crewmen 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")

24th century

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.

According to Nella Daren, the fourth intersect of Jefferies tube twenty-five was the most acoustically perfect spot on the USS Enterprise-D. (TNG: "Lessons")