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I saw some games or stories where space mines were used.
My question is: would it really work ?
I think the chance of hitting a mine is really really low in space. Where would you place a mine in space to be effective and how should the mines work, to be efficent ?
Mines could work if we stretch the definition of a mine.
The problem with space is...
So our mines can't be stationary as they'll hardly ever be in the right place at the right time. They also need to have a really big impact and they need to be invisible.
All of which, not ideal...
So first things first, you need to pick a place you want to defend... forget anything bigger than an asteroid as the area of space you need to protect from gets ridiculous.
Ideally, you need to limit your enemies movements, so get a load of mass and stick it in close orbit to your protected rock, not ideal but it does cut off some guys coming in.
Another limiting factor could be putting your rock in a gravity well of a bigger rock, making it more costly to reach you.
So now we have our place to protect, now we can look at the mines.
The mines need to be active and seek out their prey, some quick thoughts on this
But really, with all these put in place, mines are still not ideal unless someone is coming to enslave you instead of wipe you out. If I was fighting a war in space, I'd just keep throwing rocks at your base until one of them hit.
An alternative use of mines like this would be to deploy them around your ship if pirates come a-knocking - you can use them to drive ships off and make a safe zone for you hightail it out of there.
Edit - why not use a Dyson Sphere
In comment discussions, we have postulated the use of a Dyson sphere - directing all that power inwards towards a fleet would have a significant impact the same as a minefield and it solves the issue of trying to cover everywhere at once. The power level/damage would be massive but a co-opted civilian system would not be as accurate (otherwise bye bye fleet entirely)
Actually i think the viability of space mines depends on the technology available.
First, a mine is comparatively tiny. I don't think they'd be bigger than let's say 5-10 meters diameter, otherwise you can't transport any significant amount of them.
So how can a tiny spaceship of let's say 1km hit an even tinier mine in the vastness of space? It can't. The chances that a ship will pass close by, let alone HIT the mine are so tiny, that the costs of making a minefield would be so high that they wouldn't be effective at all.
The secret is to make cheap mines that destroy expensive ships. Otherwise you could build expensive ships to destroy expensive ships.
So our mines need to destroy or damage the ships when they get "relatively" close. In order for them to do that, they need passive sensors to know when a ship is nearby. Ladar or Radar ain't gonna do it, because they can be detected, giving away the minefield loooong before the ship is there. Maybe magnetic or gravitational (handwaving required) sensors could do the trick.
So once your mines knows there is a ship coming, it needs to "detonate" to destroy the ship. It could use several methods for that:
A mine in space will be something like a CAPTOR sea mine. Since space is vast, and you will have limited resources, the reason for having a "minefield" will be to deny access to something valuable, which is most likely a planet.
To do so, you will need to have your mines in orbit around the planet to make it difficult for enemy spacecraft to orbit your planet. This can be done in many different ways; the least sophisticated (and probably most expensive in terms of mass and lift) would be to fill LEO with all kinds of space junk. Particles of sand or ball bearings whining around the Earth at 7 km/sec would have a huge amount of kinetic energy relative to their size (An object impacting at 3 km/sec delivers kinetic energy equal to its mass in TNT. This is often known colloquially as "1 Rick" of energy). An incoming ship wold be effectively pelted with hand grenades and have sensors, radiators and other "soft" equipment rapidly stripped away.
The disadvantage of this minefield is it is going to be difficult and expensive to clear it, both for the attacker, and equally for you, should you need to launch your own spacecraft. If the "field" is in polar orbit, you effectively block both incoming and outgoing flight from the entire planet.
Captor type mines get around this problem by orbiting in defined paths, but having sensors and the ability to launch offensive weaponry at the target (A CAPTOR mine houses a torpedo). A simple form of this would be mines carrying missiles to launch at the target when it comes into range. Since multiple mines could be in range at a given time, the enemy ship suddenly has to deal with a saturation attack.
More advanced forms of this would exchange the missile bus for a nuclear warhead. Following the Atomic Rockets "Conventional Weapons" site, nuclear explosives can drive high velocity kinetic or energy attacks against spacecraft. This not only puts the craft at risk from long distances, but the extreme velocity of the projectiles ensures there is no left over space junk near your planet (although the objects will continue to move through space until something stops them in the future).
Nuclear explosions can drive "shotgun" pellets at 100 km/sec
Nuclear shaped charges which can drive slugs of liquid metal at up to 3% of the speed of light
Casaba Howitzers which are specialized shaped charges which emit a star hot spindle of plasma at 10% of the speed of light (enough speed and energy to be comparable to very powerful laser weapons at hundreds to thousands of kilometres away without a heavy and expensive laser generator.
Conceptually, nuclear explosions can also drive X ray lasers, providing huge energy dumps on a target at the speed of light.
Weapons like this extend the reach of a "mine" to distances from hundreds of kilometres to up to a light second (after that, light lag means the enemy spaceship has ample opportunity to evade incoming strikes).
Remember, mines are automated systems, so the enemy could spoof them or discover a means of disabling them. Alternatively, he could choose to sacrifice some ships (perhaps empty hulks) to discharge enough mines to create a clear space to operate. As mines become more sophisticated to deal with this, their advantage of being numerous and inexpensive declines (although they will still be far cheaper than spaceships with comparable weapons load outs).
Well, they may.
Explosions in space are nothing like Earth explosions. As this link points out, no flames whatsoever - it would be only the mine's debris going in every direction, in a straight line. If you're a tricky one, radiation too. So how could you injure a spaceship?
In our current world, fragmentation grenades already use this kind of technique to injure enemies. In space, you could have mine filled up with injuring parts (either cutting through or hurting the shell like a ram). Your blowing power, however, needs to be massive (depending on the ship which will detonate the bomb). The main problem with mines is that it is really hard, in a realistic manner, to immobilize them in space. Even the slightest force will result in it going through space (at a really slow pace, maybe, but still).
You may anchor them, but they'll be more visible, and the anchor itself may cause damage to the structure it is bound to.
With this kind of information, you can even make direction-oriented mines, with the center of your explosion not centered, and the debris in a certain position (I'm having a rough time explaining this but I'm sure you are understanding). Be the problem of the place ...
Usually, when we are talking about space travel, we are making the assumption that there are space routes. Star Wars even defines this as hyperlanes for hyperspace travelling, but no man would be fool enough to travel in space without any guidelines. If we're in space, we set up safe roads to travel there.
So let's summarize:
I guess it could work, in a world where space travel exists. The only difficult thing would be to keep them stationary, but really stationary, I think.
Mines generate a force when touched, this force, on Earth is represented as a shockwave that tears apart the offending ship, it's why, here on Earth countries are obliged by international law to declare when they're laying minefields so that shipping lanes and commercial vehicles can avoid the area, but these declarations do not have to be specific (See Here)
In Space, however, there's very little, if any material to use to generate such a shockwave, (Note: Space, despite its name is not empty) this means that, in order for a mine to be effective, you'd need your opponents to be really close to the mine.
Bearing in mind that any space-faring civilization is likely to have Faster-Than-Light travel to get anywhere in a remotely relevant time frame when compared to the average lifespan of a Human, this means that a mine probably won't have a chance of hitting said ship and explode... into empty space
Another thing is that, in Space, you're not bound by the laws of friction and aerodynamics, meaning the prevailing force in play is Gravity.
Any body of mass has its own gravity; the more massive an object, the larger its gravitational influence. 99.9% of this influence in our Solar System is generated by our Sun (Sol), so leaving a mine floating without any kind of thrust is just going to get said mine pulled into the Sun, this means that the mine will need to be constantly changing its location to compensate. (Newton's law of gravitation)
If by mine you mean a fixed or semi fixed single use automated defense system, they could work. If you mean a big bag of explosives that goes BOOM when something triggers the detonator, not so much.
And even today not all mines fall into the latter category. For example the US Navy employs or employed the so-called CAPTOR mine, which operates by detecting a ship or submarine within its vicinity and then launches a small homing torpedo (of the same type typically used by ASW helicopters) at that target.
A space mine could work along the same lines, launching a guided missile at the detected ship.
Another variety could have a high power X-ray laser fed by a nuclear explosive. When a target is detected, the mine orients on the target, the explosive detonates, and a high energy pulse of X-rays is fired at the target as a result, destroying the mine in the process. Again, something similar has been done on earth, most famously the shooting aparatus installed by the East German government on the fences surrounding their country to shoot those attempting to flee, which would detect breaking wires in the fence and shoot towards the likely point of breach. These were single shot (or salvo) and could be reset and reloaded of course.
An alternative, low-tech approach would be using the mines not as a way to destroy enemy ships but to denial them the access or at least slow them (I read somewhere that this is the actual strategic usage of land mines; any mine that you deploy may be deactivated by the enemy, but it forces the enemy to slow down so your patrols can detect/fight it).
Imagine an incoming enemy fleet homing on your homeworld and going at 0.75c. Even if your network of scout satellites detected them at 1 light hour of distance, you will get the warning only 15 minutes before the enemy fleet arrives.
Now lay in the enemy path a bunch of rocks in stationary orbits. From you enemy fleet POV, that is a bunch of rocks coming towards them at 0.75c. If the rocks are detectable 1-light minute away, it means that the ships only have 15 seconds to try to alter course before collision (and that is without counting the time contraction in the fast moving ship!). That would be a more than enough reason for enemy fleets to move at slower speeds, giving your defenses more time to prepare for the coming battle.
And alternative use is to force the enemy ships to take active measures against your mines, which makes them visible. Imagine that your scout satellites work by detecting energy emission, and a fleet can be effectively hidden by just shutting down engines/weapon/comm/detection systems; that fleet could just set a path your world outside your network range and "drift" slowly towards their unsuspecting victims. It may involve some risks if they cross the eventual astray asteroid but their odds are good enough.
Put in the middle the same bunch of rocks and suddenly they need to start activating detection systems to detect the "mines", weapons to destroy them or shields to protect the ship or engines to avoid them, all of which will make them detectable by your scouts.
This plan is simpler but requires that you put a considerable amount of "mines" in orbit to ensure that they work as deterrent; that will depend of what is at stake and the power and number of enemy weapons (for example, if the enemy is fighting for its survival and has a planet-eraser bomb, they may send all of their ships anyway and hope that at least one of them survives and wins the war for them).
In orbit, you have Kessler syndrome - doesn't even require explosives.
Outside orbit, it relies on having commonly used routes. If you can find a way to accomplish this (wormholes or warp gates) then it's reasonable. Otherwise, the area you need to cover becomes quite large, so you'd need very advanced mine technology for it to be viable.
The mines themselves are only that by analogy. Land mines cover a 2D surface, so it's possible for them to intersect every path, thus they can just wait for someone to step on them. With space mines this will never work, you need the mines to have their own propulsion. They must also have their own sensors to detect enemy ships and target them, so we're talking "smart mines", more like automated guided missiles. This also gets around the issue of asteroids plowing through your minefield.
Every mine will have a "sphere of attack" which is a large volume (not necessarily shaped like a sphere or even a single bounded volume), bounded by its delta-V vs. the target, and where the target is coming from/how fast. So SOA depends on the target, and may not even necessarily center on the mine. When the mine detects a target intersecting this, it fires thrusters and attempts to intercept. The effect of this is that certain trajectories are precluded because if you follow them, you are guaranteed to have several missiles on you.
The weird part is that while land mines define these trajectories based purely on space, with space mines you would also consider velocity (of both target and minefield - moving minefields are possible in absence of friction), delta-V and thrust of the mine/target. A military that uses mines would have access to competent statistical expertise and artificial intelligence (not the terminator kind, but the cruise missile kind) to set them right, although that's probably a given for space navies. They would decide on what enemy movements by what kinds of vessels are most dangerous, and lay the mines accordingly to get the most bang for their buck. Nimbler ships will tend to escape, and other ships if they are going too slow or too fast or in a different direction will also be unaffected.
Since the mine is a fair bit of technology, you have some nuances that can serve as plot points:
Although I would expect to find mines primarily in some sort of useful orbit. Orbiting/deorbiting is the bottleneck of space travel, and most useful space travel does it often enough. Just denying commonly used orbits to your enemy could go a long way. Failing that, mass foci in deep space (such as space stations used for resupply) would be a good place. Trying to just carpet mine all of space seems as pointless as trying to mine an open field or ocean on Earth.
Think something along the lines of the Very Dangerous Array (VDA) used in Schlock Mercenary. Basically, you have a massive number of missiles/torpedoes, each fitted with a basic AI and a suite of sensors. All the torpedoes are deployed, spread out, over the area you want protected.
The VDA was originally meant as a giant telescope, but it had the wonderful side effect of having all the projectiles already deployed, waiting to be sent at targets at any instant. Thus the name.
The more torpedoes you have deployed, the more area you can deny, and the better resolution your explosive telescope array can provide.
Of course, since we're using torpedoes, you could argue that they're not really mines. But when they're deployed but not actively trying to kill a target, they're basically motionless and lying it wait just like naval mines.
So to answer your question, space mines would work if they're self-propelled, smart-ish, and deployed in massive quantities. They can also double as a telescope array if you're smart about it.
There's these interconnected issues: Range of the mine and distance to target.
It's hard to estimate how far away a spaceship needs to be from an explosion to be safe. However, the project Orion proposed to propulse rockets by detonating small nukes (0,15kt) just tens or hundreds meters away from a (specifically designed) pusher plate. So my guess is that a ship is safe if it's a a km or a few away from the mine.
Along with project Orion came the idea for a directional nuke, where a bit less than half of the blast is concentrated into a narrow arc of maybe 30°, a bit less than half goes out in a semisphere the other way (conversation of momentum). If you can aim that narrow arc at your hostile ship, it would need to be farther off but not by orders of magnitude.
In conclusion, my guesstimate is our small mine needs to be closer than 1 km to do real damage.
How about bigger bombs? Let's take the Tsar, at 50MT or roughly 330.000 x the yield of our small Orion nuke. Whatever effect our nuke has it will likely drop with the square of the distance so we need to be ~580 times as far to be as safe, compared to the small nuke. So in case my guesstimate holds, maybe 600 km from the Tsar.
Take this all with a huge load of salt however: Shockwaves don't really work in space so we would probably look for a bomb that produces a huge load of hard radiation which I think the Tsar is not.
Now space is big, so keeping a 600km berth should be easy, right? Well there is this idea of the interplanetary transport network, a set of routes that are very efficient (if slow) for rockets. Supposedly. One trick is to fly through lagrange points like the one between moon and earth, which are also stable positions (or rather orbits) to put your mine.
But even so, flying around the lagrange point by a few thousand km is probably not a huge deal for any rocket and many missions don't use these low energy transfers. OTOH, a mine on a lagrange point would be an easy target for a far cheaper weapon to clear, and would be comparatively easy to find. It's hard for me to imagine mines being effective in space.
Taking away all the issues with how explosions have limited utility in space, and the fact that space is so huge that you can't really hit anything with anything without trying super hard, the fundamental concept of a mine is simply put incompatible with space.
A mine derives its danger from the fact that it's hidden, but in space it's not really possible to hide. In order to sense nearby targets, a mine would have to operate at temperatures dozens to hundreds of times hotter than the background, and that energy has to go somewhere, leaving a telltale signature that can be spotted from approximately all the way away.
Depends on what you mean by mine, and how willing you are to play with orbits
If you mean "Conventional explosive that someone runs into" then no, for the reasons you laid out in the question.
However, if you mean "Autonomous weapon system that sits in a region until activated" then you're in luck.
Imagine a bunch of tiny Cubesats placed in varying orbits around a planet - Retrograde, polar, 60 degree incline, the only important thing is that they're all in different orbits. They sit and look pretty until they're activated by a ship nearing the planet they're guarding. As it approaches they examine the ship to see if it's going to enter into their orbital region, and if yes the mine with the highest intercept velocity is told to alter its course to intercept.
As an example, if I had a swarm like this around earth and I wanted to get rid of the ISS, I'd pick a 'mine' orbiting retrograde to the station at a roughly 60 degree inclination. The sat would then line up its trajectory, and smash into the ISS at a blistering 34,000 Miles per hour. Bonus points for packing the sat with a self-destruct charge to turn it into a shrapnel shotgun.
Best part is you could cheaply place these 'minefields' around any planet your foe wants to use as a gravitational slingshot, and use their own speed against them. The high approach velocity means that they'll have less time to detect a soccer-ball sized mine, and better yet that the impact velocity is going to be obscene.
So, space mines aren't primarily meant to knock out invaders. They are meant to funnel invaders into the safe zones where they can be shot by active systems. If your defense makes the bad guys go away without attacking, you win. If it makes them come at your strong points head-on, probably you win.
I probably got most or all of this from David Weber's Honorverse books, so go read.
Yes, but..
So mines don't even work that well at sea unless you have a way to constrict them to a specific area. Meaning you can't mine the entire Atlantic ocean, or even the Gulf of Mexico, but you could mine the port of Tampa, as part of a blockade.
The same is true in space, but with a added "dimension". You could mine an orbit, or exit from a "gate". Maybe a known path or trajectory. For example, if every ship going to Alpha Centuri had to slingshot withing 1 mile of Jupiter's atmosphere, Hey you could mine that.
Or perhaps the asteroid belt has 1 asteroid that is awesoium on it. You could mine that asteroid's area, but you could have a hard time mining the entire belt.
This is true for naval warfare too. Mines are not effective in the open. There better in tight controlled spaces.
Mines work on the concept of denial. They make it dangerous to your opponent to enter a certain area and significantly increase their risk if they do not alter their behaviour. Mines in space could work where you have a clearly defined chokepoint.
If you can't find a chokepoint then it's unlikely you'll have enough mines in the vastness of space to saturate an area large enough to matter.
If you're using sub-light, takes a lot of emery to change direction speed up/slow down then yes, but only because there is a pre-determined place that you are going to and you are going to and i have plenty of time to calculate where you are going, how soon you'll get there. and lay them all down. Even if it doesn't hit the intended target, the targets will waste valuable energy slowing down.
Mines also provide a shell that means that a ship has to keep a more distant orbit, but that is more of just a small nuisance than an actual issue.
I'd refer you the Deep Space 9 Episode "Call to Arms", in which such mines are being laid.
In the episode, the mines are shown as being roughly a metre across, and being laid perhaps 100 metres apart in a grid pattern. (They were to cover the entrance to a wormhole, preventing an enemy fleet travelling through it.)
These aspects of the mines is what allowed them to work:
Each mine could cloak.
Each mine could self-replicate (so that the enemy couldn't "punch a hole" by sacrificing ships)
Each mine used sensors to detect a nearby ship, and had propulsion so it could attach itself to the ship. This is similar to some sea mines in WWII which used magnets to attract themselves to passing ships.
A ship would only attract 20-30 mines (since each mine was so small), so that there were enough to destroy it, but not enough to deplete the field.
Apart from dealing with explosive yield and ship speed, this is plausible.
Don't take a classical sea mine and deploy it in space.
This would be like trying to use a land mine at sea. As pointed out by various responses, explosions would consist of accelerated debris and gas only.
It would be logical to implement homing mines, that work with a proximity detector of some kind. This kind of homing space mines are seen in the anime Legend of the Galactic heroes. There they are deployed in huge fields across anticipated enemy routes.
Because of the fact, that you won't move slow in space (it is really really really big), anchored mines would pose an even greater thread. It would be possible to deploy massive but small spheres of a high density material and link them with chains to create a net. Because the objects that can be detected by any electro-magnetic scanner-devices is limited my resolution, it would be difficult to spot this nets, before they rip your ship apart with your own kinetic energy.
BUT even if the chances to hit a ship with this kind of "kinetic mine" are low, the mere existence of such a thing would cause demoralization when flying across a probably mined sector. Imagine a post war solar system, where you could die every second because of a (too small to be detected) stray "mine-bullet".
