Beyond being "claustrophobia inducing spaces to crawl around or get trapped in to increase tension in an episode" why are there so many small tubes* (crawlways) in Federation** ships?

  • Having to crawl while dragging a tool box is an incredibly inefficient way to move.
    • In the real world, having to drag a tool box into the crawl space under my house is a major pain in the neck (and other body parts).
  • Having a separate tube for maintenance access next to a hallway or room is a very inefficient use of space.
    • Everything inside these tubes is behind an access hatch of some sort, so putting the hatch on the other side and making it accessible to a hallway would make installation and maintenance much easier on all concerned.

To be clear, I'm wondering if there is an in-universe reason for this design aesthetic since realistically it seems so very impractical. Out-of-universe, I get that it's great as a plot device.

* I thought they were all called Jefferies Tubes, but it seems those are only the ones that go to the warp engines

** This isn't just limited to Federation ships, it seems the Cardassians designed Terak Nor/Deep Space 9 with a plethora of these little crawlways, too.

  • 1
    They're there to produce dramatic shots on a weekly TV series budget from the 1960s.
    – Zeiss Ikon
    Nov 3, 2021 at 16:57
  • I did note that. I was hoping, since there seem to be in-universe "reasons" for so many nonsensical things that maybe someone had an in-universe reason for this design aesthetic.
    – FreeMan
    Nov 3, 2021 at 16:58
  • 1
    IIRC the maintenance tubes were usually depicted as being perpendicular (normal) to the plane of a wall (i.e. as going straight into the wall rather than parallel to it). That implies that the tubes get you deeper into the ship than would be physically reachable via "regular" corridors and rooms. It may be the case that some systems cannot be positioned in a more accessible location due to technical requirements (e.g. "the shield generator has to be here, but we can't put an entire corridor there, it wouldn't make architectural sense, so we'll just put a tube for maintenance").
    – Kevin
    Nov 3, 2021 at 17:48
  • 3
    There's only limited space on a spaceship and a maintenance tunnel that is wide enough and tall enough for a person to stand in (which might only be used once in a blue moon) is simply a colossal waste of room.
    – Valorum
    Nov 3, 2021 at 19:08
  • 2
    1. It's cheaper to build a crawlspace than a basement. 2. Would you rather use a ladder to fix pipes in the ceiling, or lay down and fix pipes at arm level? 3. Pipes have to go somewhere: they can either be in the ceiling of your lowest level or on the floor of your main level. Would you rather trip over them everyday while making breakfast, or get a pain in the neck once a year when you have to be down there?
    – bishop
    Nov 4, 2021 at 3:36

5 Answers 5


Like pretty much everything in Star Trek, it's a combination of "inspired by reality", "made to fit a TV budget", and "whatever drama requires".

"Inspired by reality" usually means wet navy in the case of Star Trek, and ships certainly have plenty of cramped machine spaces, but in this case I detect an influence from the crawlspaces on the B-29 Superfortress and the B-36 Peacemaker. Gene Roddenberry himself piloted the B-17 Flying Fortress, and is likely to have kept up with info about the US's subsequent long-range bombers. The real-life examples are designed with practicality in mind, and usually have concrete reasons when they're impractical, but see the "whatever drama requires" point.

If you're looking for a coherent in-universe explanation, I don't believe there is one; I don't recall much attention being given to it onscreen (it's just a given that they exist), and I didn't find anything in the quasi-canonical Next Generation Technical Manual written by Rick Sternbach and Mike Okuda. I don't have the TOS Star Fleet Technical Manual to consult, but in any case that one has even less canon authority.


"I thought they were all called Jefferies Tubes, but it seems those are only the ones that go to the warp engines"

You were right the first time. The little tunnels throughout the ship ARE Called Jefferies tubes.

And the canonical reason for them: a network of power conduits run through them.

Example, from the episode Power Play.

[Jefferies tube]

(Geordi and Ro are pushing some equipment in front of them) LAFORGE: Section two B, A, section one.

RO: Finally. I never want to see this part of the Enterprise again.

LAFORGE: I hear you. This is what starship designers call easy access. Yeah, yeah, this is it. I thought we might have a problem with conduit number two twenty seven but it looks like we're going to be able to get by it.
(They remove deck grills and he hands Ro a small device)

RO: Thanks.
(She cuts through circuitry)


I dont know about the original series but in later series when we see the tubes in use its usually for some emergency Dr.Crusher evacuating sickbay in first contact, Suter hiding from the Kazon in Voyager, so in universe while it may never be explained they seem to be emergency access points that allow you to get from almost anywhere on the ship to almost anywhere else when the normal ways are compromised.


To my knowledge, it's never been mentioned on-screen why the tubes exist.

However, one of the reasons might be that a small, possibly reinforced tube is structurally more stable than a hallway built for comfort, so if there is an explosion the hallway might be blocked by debris, but the access tunnel could survive and be used to bypass the debris.

Since the tunnels exist as bypasses anyways, might as well use them as normal engineering access as well. That makes ships and stations cheaper and smaller, because you don't need comfortable access paths in addition to the bypass. The engineers probably got outvoted by the budget office on that one.


I'll start off with an out of universe and end up in universe.

Having built many large scale factories and other devices, you build the overall device first and then "thread" the cables from location to location. Not having crawl spaces precludes you from doing so.

In order to eliminate crawlspaces you would have to fit cables/conduits to the minimum volume that contains them. But doing so would be impossible because things like friction would make it impossible to drag a 5cm diameter 100m long cable through a 5.1cm diameter opening - and that doesn't even consider the problems of going around sharp corners.

The only future technological possibility would be to 100% 3D print/replicate a ship from scratch, and in doing so eliminate all "unnecessary" volumes.

But in every scene that has shown ship construction in a dock, it has shown people building them piece by piece. Nary a single 3D printer in sight.

So the obvious conclusion is that the future we have seen don't include 3D printers large enough to spit out a ship and that they are left with 20th/21st century production techniques. IE require extraneous volumes.

For fun, compare a ST vessel with another complex vessel that you have close at hand, and doesn't contain any extraneous values - your body. It wasn't built, but grown.

Of course there are other reasons for having "unnecessary" volumes. Such volumes can contain various environmental sensors. They allow access for inspection/repair. They can be used for emergency egress. Remove the volume and you remove all this epossibilities.

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