Dilating Door

"The door dilated."

- Beyond the Horizon by Robert A. Heinlein.

As you might know, a "dilating door" is science fiction Fan-Speak for the trope that we call "Cool but Inefficient". This trope refers exclusively to Cool But Inefficient doors and hatches - doors that slide up into the ceiling, doors that dilate like an iris, doors that dissolve and rematerialise... Apparently, plain old hinges are extinct in the future.

It's probably a reference to Heinlein's advice that you could make a futuristic air by casually throwing out details like "the door dilated", as if such things were nothing to really notice, like your use of a globally interlinked computer network for information and entertainment.

Subtrope of Our Doors Are Different.

Anime and Manga

 * The doors on the industrial ship in Ghost in the Shell: Innocence don't make any sense. They consists of four squared panels fixed to two hinges on each side of the doorframe at middle height which are tilted sideways and into the walls. However, it looks quite cool when Batou charges through the coridors and every 15 meters one of these opens just a split second before he reaches it.
 * Seriously, any Sci Fi anime (especially pre-2000) has these doors. A case of Seen It a Million Times.

Film

 * Alien
 * Played for Laughs in the film of Barbarella, when Jane Fonda is wearing (little more than) an animal-skin suit with a long tail and the tail gets trapped in the closing iris.
 * The doors on the Death Star in Star Wars. "Close the blast doors! Open the blast doors!!"
 * While the blast doors are the only dilating doors seen, nearly all other doors in the franchise slide either sideways or up. And then there's the Gungans' bubble tech, which keeps out water but permits solids to pass through.
 * A bizarre aversion in Tron: Legacy. The interior of house in the Grid has obviously visible hinges and door knobs on all of the doors, such that they wouldn't be out of place in a regular modern house. This, of course, is taking place in the entirely virtual world where Cool but Inefficient is king. Even stranger when compared with the Ascetic Aesthetic design of the rest of the house. In particular, the windows stand out, as they are not made of a solid substance, but instead seem to be Some Kind of Force Field, marking a pretty stark contrast with the doors.
 * Amusingly averted in the 2009 reboot of Star Trek. Whereas the Star Trek universe does other things (see below), the Starfleet facility on Delta Vega has a normal exterior door with a panic bar.
 * In Star Trek VI, the Enterprise halls were designed with various decorative pipes along the ceilings. Problem was they often led to walls with doors that opened upward...

Literature

 * Robert Heinlein's Beyond This Horizon had a dilating door. There was probably one in Friday as well (it said "the door contracted").
 * James White was fond of this in his Sector General books, even having a speech about what kind of doors there are in the universe. Essentially, doors can open through hinges, slide in or out, open up or down, dilate clockwise or counterclockwise, or create a quantum-physics manipulating field around themselves so that every atom of a person can pass through without hitting the atoms in the door. The person making the speech went on to say that no civilization in the universe was known to be advanced enough to use the last option, and if any were ever to be encountered, "we will be sure to be very polite."
 * Ships in Animorphs are 'living metal'.
 * Samuel R. Delany's Stars in My Pocket Like Grains of Sand had "the door deliquesced".
 * Parodied in David Langford's first drabble.
 * G. Martynov's Starfarers, a fairly average late day Interplanetary Voyage novel, features Sufficiently Advanced Humanoid Aliens from the planet Phaeton, who used the disintegrating-and-rematerializing doors in their spaceship.
 * Older Than Radio example: In H. G. Wells' The Sleeper Wakes "And then came a strange thing; a long strip of this apparently solid wall rolled up with a snap, hung over the two retreating men and fell again".

Live Action TV

 * The defensive iris used on the titular gate of Stargate SG-1. Arguably, this can be justified because the alien gate didn't come with a convenient slot to allow sliding a solid metal door over the event horizon. But then they completely forgot to explain where the iris disappears to when open and where the presumably complex mechanism for operating it is. By Stargate Atlantis, they just had a more prop-friendly generally-invisible Force Field that prevented invasion via "Unscheduled Off-World Activation."
 * On the original Star Trek they did everything possible to make the doors interesting; except for having it descend into the floor. That was too expensive.
 * The later series increased the budget. Of note are the airlock doors on Deep Space Nine, which look like gears with windows attached to mechanical arms and roll sideways.
 * This design was homaged/copied on Torchwood.
 * On the Star Trek the Next Generation episode "The First Duty", the Academy dorms have doorknobs and hinges.
 * Doctor Who has far, far too many "dilating doors" to list here, but special mention goes to a door in Day of the Daleks which curls up toward the ceiling in a slow, sinister fashion. The Ark in Space also features a sliding door that almost takes the Fourth Doctor's arm off. "I'm rather attached to it," he said.
 * In Firefly, on Serenity, the doors to the crew quarters were these elaborate swinging ladder/door combination things. Quite space-efficient, if a bit easy to lock from the wrong side. (And not wheelchair-accessible, although the guest quarters were.)
 * Still quite modest for this trope, since all the doors on the ship are opened by hand. The guest quarters have perfectly ordinary, manual sliding doors, again a matter of saving space.
 * In Mystery Science Theater 3000, the main characters are compelled through an elaborate series of variously opening doors and into the screening room.
 * Well, Cambot is. The audience never sees the other characters during the door sequence; they might be going into the theater through a side door.
 * And this might just be a shout out to the opening and ending sequences of Get Smart!
 * The doors to personal quarters on the eponymous Babylon 5 open by rotating clockwise. They have been known to fall on cast members. Others open like modern automatic doors, sliding to either side.

Tabletop RPG

 * In Traveller, spaceships could have iris (dilating) doors.

Web Comics

 * Subverted in this strip from The Inexplicable Adventures of Bob, when Bob is surprised that alien doors have doorknobs.

Western Animation

 * In one episode of Cyberchase, the kids go to Symmetria to find Ava. The building they encounter has a round door with four holes in it, mounted into a wall with four holes in it. By default, the holes don't align, but every once in a while, the door rotates so that they do align briefly. The trick to getting through is to jump through while it's moving. Nobody gets stuck in it, but it's just asking to happen. Good thing those kids are fairly nimble...

Video Games

 * The Metroid series is an excellent example given that pretty much every door neeeds to be shot to open. Sometimes they require multiple shots. Sometimes they need missiles.
 * This is explained in the Metroid Prime games as being a method of bypassing the door's normal opening mechanism; you're basically lowering a weak shield that's there to keep wildlife (or you in the case of stronger ones) out and the doors are opening automatically (presumably there's a more peaceful manner of opening the doors). The ones that need missiles explicitly have a blast shield (which disappears after being removed the first time) on them for extra security. Some areas of Super Metroid have doors which lack the shields and just let your straight through when you approach.
 * Although Golden Eye 1997 usually does fine with normal sliding doors, the Cavern level features iris doors. And yes, it is a pain in the ass when the door takes 5 seconds to open while you're fighting a horde of 20 enemies in your back...
 * The Vaults from the Fallout series are sealed behind doors in the form of enormous steel cogwheels that are rolled along a track by a mechanical arm and then slid shut.
 * Parodied in Fallout 3 in the Mechanist's Lair where the main entrance is a ridiculously complex set of doors that take easily couple of minutes to open entirely. It's also a Shout-Out to Get Smart and/or Mystery Science Theater 3000, being exactly the same as one of the doors in both those series' famous door sequences.
 * Half Life - quite a lot of the doors in the Black Mesa Complex do this vertically and horizontally. Half-Life 2 introduces Combine doors, which look like a ton of scrap metal held in place, which all individually slide out of the way when opened.
 * Halo. Most Covenant and Forerunner doors are like this. Covenant doors beep before they open though.
 * Sphincter and other doors from Prey.
 * In the future part of Day of the Tentacle, the doors open vertically with the original Star Trek the Original Series sound.
 * Knights of the Old Republic features a variety of oddly opening doors, ranging from the relatively boring two part doors that slide sideways to ridiculously complex systems of interlocking bars that unlatch and slide apart.
 * Quest for Glory IV has a cave with doors that look like giant sphincters; however, this is Justified since.
 * Spoofed, of course, in Season 3 of Sam and Max, where the doors on Skun'kape's ship dilate, slide in, and even tilt in -- from opposite sides!
 * The doors in Mass Effect are made of layers of interlocking parts.
 * Doors in Doom open upwards, primarily due to limitations of the engine. "Polyobjects" from the version of the engine used in Hexen and later source ports can be used to make doors that actually imitate real-world door behavior.
 * Despite the High Fantasy-esque setting, doors in The Legend of Zelda: Twilight Princess are surprisingly complicated, mechanically speaking. Many dungeon doors are round, and when pushed in, roll out of the way through some mystery of technology.
 * Starship Titanic's arboretum has a door that 'grows' open and closed and is made of metal plants.