http://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceMines

In Space The Dominion plays Minesweeper...

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Space Is an Ocean and sometimes your Space Navy needs to block access to a port, a space lane, or even an entire planet. How to do this? Why, Space Mines, of course. These are like their seagoing counterparts, but IN SPAAAAACE!!!

Just like there are several types of Sea Mines, so there are also many types of Space Mines. Most common are proximity mines, that go off when a ship gets too near, and contact mines that go off when they hit a ship's hull. Magnetic mines are attracted to metal hulls. Homing mines are essentially missiles that sit around until they detect a ship's engine or weapon energy signature, then angle themselves at the target and let fly. Some mines are miniature weapons platforms that open fire when ships get too close. Remote-detonated mines can be set off by a waiting vessel when a target ship gets in range. Nuclear mines have nuclear warheads in them. Then there are mines that rob ships of power (dampening fields) instead of just exploding. There are many other variations and combinations.

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In real life, there would be some major limitations to this trope. However, since Space Mines seem to be an ubiquitous part of Space Operas, sometimes the savvy writer thinks of the above limitations and writes around them - and real-life applications have even been discussed in military circles.

In order to secure a whole planet, you'd have to mine space three-dimensionally in order to be effective. In fiction this is often not done.

Earth's ocean and sea terrain contains a lot of inlets, natural harbors, bays, straits and other types of terrain that make natural choke-points where the use of mines is a practical way to deny or substantially delay passage to unwanted ships. No such barriers or terrain exist in space, and so such a barrier may be easily circumnavigated. Even protecting a very small moon with a density of one mine per every few thousand cubic kilometers would require massive numbers of mines and logistical support to successfully achieve coverage. While not completely impossible, the same logistical resources would be of better use in improving detection and interception/quick reaction capability, or outright constructing more battleworthy spaceships. Can be justified if there IS a conveniently narrow pathway to barricade, such as a local entrance to Hyperspace or the Portal Network, or if the object to be surrounded by mines is fairly small, such as an asteroid base.

Advertisement: Laying mines takes time, and for every increase in target area's radius, the number of mines you would need increase quadratically. To cover large or even moderate areas could take hundreds of years, even if it only took a few seconds to lay each mine. Justified if the mines have potential to locate and approach, or shoot, their targets from massive range, thus ensuring blockade functionality despite low minefield density, or can be all released in a single spot and relocate and organise autonomously. As for the matter of quantity, this can be explained by having automated manufacturing and minelaying facilities operating over lengthy time periods, or have the mines themselves be self-propagating Von Neumann machines.

Sea mines are deployed under water, greatly complicating the task of detecting and clearing them. Space Mines, however, are completely exposed, and easily detected since spaceships have to be able to detect debris of sufficient size to cause damage by impact. Unless there were some sort of mitigating factor (sensory disruption, cloaked mines, etc.) space ships could just pick them off with long range guns/lasers/missiles/decoys/whatever. May be partially justified by the fact that, unlike enemy ships, they can be inert, dormant and undistinguishable from generic space debris until they're close enough to strike.

Everything with mass has gravity. In space, little things that are relatively close to each other tend to clump up — this is how planets and stars are born, and why there are no Asteroid Thickets. The mines would need some way to fight or negate the effects of gravity on each other that also wouldn't run out of fuel. On the opposite end of the spectrum, if they're not close enough to clump up, they will tend to drift off, and potentially become hazards to navigation. Oceanic mines are moored to the sea floor; space mines cannot be.

Not to be confused with Space Mining operations, mining valuable materials from asteroids or other planets in space

Examples:

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Anime & Manga

There are massive space minefields around the Men's Planet (Tarak) that is visited towards the end of Vandread (second season). They are used to reveal First Mate BC as The Mole, since s/he knows the friend-foe codes of the mines that allow Nirvana to pass them.

as The Mole, since s/he knows the friend-foe codes of the mines that allow Nirvana to pass them. Mines are used in multiple battles in Legend of Galactic Heroes.

In Mobile Suit Gundam Wing, the area around the space colonies is seeded with mines to prevent any unauthorized travel. Trowa's first assignment upon enlisting with OZ is to help destroy the mines, as part of OZ's "kinder and gentler" facade. The original series had both the Gyan, which could deploy floating mines from its shield and the MSV model kit Zaku Minelayer, which was just the standard Mook with a bigger backpack that dropped mines.

Crest of the Stars has mines being one of the three main weapons being used in space battles (the other two being anti-proton beams and railguns). Ships deploy mines around themselves as defense, as the mines are self-piloting and follow the ship's movements; or employ them as self-guided missiles against distant enemies. The nature of space combat in the series makes them the most effective long-range weapons, with the particle beams and railguns being short-range options for when you can actually see your enemy.

Fan Works

In The Wrong Reflection the Terran Empire lays a minefield in the path of an oncoming Klingon/Cardassian attack fleet. The USS Bajor's Master Chief Wiggin spots the minefield and they're able to drop out of warp in time to avoid it, but much of the fleet runs right into it and the Klingon general is killed.

Films — Live-Action

The Tothian minefield in Galaxy Quest provides a rather dangerous shelter for the Protector when "Taggart" and his crew find themselves outgunned by Sarris. It comes into play again in the finale, when they use it to pull a variant on the Wronski Feint against Sarris' ship: the magnetic mines trail behind the ship, and Sarris runs straight into them . Averts the usual problem with space mines in that the field has enough layers to cover a significant portion of space (enough to look like a nebula from a distance which is why they fly into it in the first place), though still woefully small in the grand scale of things.

Literature

Live-Action TV

Tabletop Games

Star Fleet Battles. Ships can "roll a mine out a hatch" and leave it to blow up a ship pursuing them. Mines can be set to accept only certain sizes of ships as targets. Major space installations often had minefield belts protecting them. Some of the mine types available: The Romulans have a Nuclear Space Mine based on the Star Trek: The Original Series episode "Balance of Terror". Command mines can be ordered to detonate or to activate/deactivate themselves. Chained mines detonate when other mines explode. Transporter bombs can be beamed into position. Captor mines can fire weapons at targets.

Iron Crown Enterprises' Cyberspace game had Orbital Mines for use against enemy spacecraft in orbit. Some had onboard computers and could make their own piloting/targeting decisions, others had to be operated by remote control.

AKVs in Transhuman Space are not exactly mines, but similar enough: they are AI-controlled missiles that can float in ambush until a craft flies near and then attack.

Battlefleet Gothic has a large number of scenarios in which the defender can buy and deploy defence systems ranging from purely in-system patrol vessels and armed space stations through to this trope, with Orbital Mines (homing, slow moving, relatively myopic target acquisition) and Deadfall Torpedo Salvoes (ship-killing torpedoes, faster moving than mines, with slightly better target acquisition, but functionally non-homing once their drives come up). It's also possible to refit a carrier into a mine-laying role, swapping attack craft squadrons for the capacity to drop a pair of mines.

Video Games

Web Comics

Real Life