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Humans are an inherently violent species. We have had more wars, battles, and arguments over the stupidest of things than I could list if I devoted my entire life to the task. Let us assume that SpaceX succeeds. Overwhelmingly. Some sort of technological breakthrough shortens travel time between Earth and Mars to a few weeks. By 2150, 25,000 people live on Mars in 5 different colonies.

The colonies have formed their own governments, though they pay nice, lump sums to SpaceX in exchange for new technology. The colonies are each independent of each other and of Earth, though. Say colony X discovers a rich deposit Unobtanium. Colony Y has a need for this Unobtanium, but all attempts at negotiation have failed. The prices Colony X demands in exchange for its Unobtanium are too exorbitant. As a matter of fact, since Colony X is sooo unreasonable, Colony Y has decided to loot...err, liberate, the citizens of Colony X from its tyrannical despotic government.

It must be assumed that treaties are in place preventing a single colony from legally destroying another, and that to do so is considered a war crime. To bring assault rifles and grenades against a Martian colony is a good way depressurize large parts of the colony and kill most people in it. Violence in space is dangerous, so what is the best way to be violent (best being the avenue that provides the least risk of complete or near complete annihilation).


The colonies were designed to be extremely modular. Essentially, it is comprised of many small living quarters (maybe the size of a bedroom) surrounding a central habitat (where the crops are grown, the government is located, the prominent citizens live, and where supplies are distributed from)

The requirements of the war are to avoid as many unnecessary civillian casualties as possible. Anything that will wipe out an entire colony(or a majority of it) is prohibited. There are some underground complexes, but they are nowhere near large enough to shelter anymore people than 500 or so. One small addition also; humans still rely on projectile weapons, as ' "Star Wars blasters" are unrealistic for the time frame we are talking about.

I am asking in general what weapons would evolve to meet the requirements set forth by the situation posed by warfare on mars.

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I know! Post mean messages on their Facebook pages! – AndreiROM Feb 26 at 18:00
"Violence in space is dangerous" is perhaps the best truism I've heard all week. – Schwern Feb 26 at 18:00
This question is too broad. What does a Martian colony in 2150 look like? Domes? Tunnels? Bubbles? Concentrated or spread out? What would weapons in 2150 look like, Martian or otherwise? And about this treaty... are you asking "how would you subdue a pressurized habitat with minimal civilian casualties?" or are you asking "how would you attack a pressurized habitat without risking your own troops dying due to a breech?" – Schwern Feb 26 at 18:03
I think the weapons used would really depend on a lot of factors, from the desired effect of the attack to the available countermeasures. – DaaaahWhoosh Feb 26 at 18:21
If not star wars blasters, surely the industrial lasers get smaller and more efficient and powerful in a century? ...and possibly attached to sharks. – diynevala Feb 27 at 18:40

16 Answers 16

up vote 14 down vote accepted


More specifically non-lethal gas. It wouldn't even be expensive in terms of manpower and risk. Simply find a way to access the air system and introduce the knockout gas of your choice. Send your marines in with masks/filters and clean up any security forces that were prepared enough to have a mask handy when the gas hits.

For best effect you want a colorless/odorless gas, which you can search the web for or, considering it's the future, make up as some new advancement in chemistry.

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I actually never thought of this. Perhaps drugging the water supply might work better, though, I hardly call drugging an entire colony while you take the population's shiny stuff violence in space ;-) – DJMethaneMan Feb 26 at 18:28
If you're trying to be realistic based on current technology (more or less), this is not a good option. The margin of error for knockout gas makes it very impractical at current. If you want to use this, make sure you make up a new gas. – Necreaux Feb 26 at 21:59
Carbon monoxide is colorless, odorless, and will kill you dead. Though it's likely they'd have CO2 detectors... – Wayne Werner Feb 26 at 22:29
Ah yes. Right. That's what happens when you post in the middle of unit tests. – Wayne Werner Feb 27 at 4:35
The Moscow Theater Hostage Crisis was resolved by gassing everyone with a fentanyl derivative, possibly carfentanyl. In theory, this is an effective approach, nominally the therapeutic index of carfentanyl is 10,000, so it should be easy to knock everyone out without fatalities. However, it turns out that practice isn't always the same as theory, because 130 out of 850 hostages were killed by the gas. The Russian government never released any details so it has been impossible for anyone to study what went wrong. – David M. Perlman Feb 27 at 18:12

Assault Rifles and other firearms

I know it's fun to think of gas, cyber and automatic taser weapons but what about good old classic firearms?

  • Cheap
  • Likely on-hand
  • Easy to train/use
  • Won't likely cause any explosive depressurisation (this isn't Hollywood), rather small leaks if hitting weak outer walls... which would plausibly be self-healing or otherwise easy to repair.
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Cute, so use of an assault rifle in space is not a war crime if you were also issued bicycle tire repair kits. – CandiedOrange Feb 28 at 9:40
@CandiedOrange exactly ;) Seriously though, if you look at the kind of damage the ISS can take (far worse than bullets) or consider Air Marshal's use firearms you realize that the issue is largely imaginary. – NPSF3000 Feb 28 at 10:47
Basic physics means we'll be using good old-fashioned firearms for a long time yet to come. As of yet, there's no other way to store highly concentrated energy compactly and then convert it into a weapon-useful form in a fraction of a second, and there's nothing even on the horizon. The energy density of the best battery technology on the horizon, not even proven to work yet, is favorably comparable to gunpowder, but the power density is thousands of times smaller; you can't get all that electricity out all at once. No one is even talking about thinking about a way around that... – David M. Perlman Feb 29 at 5:53
@DavidM.Perlman the people trying to sellrail guns to the US Navy would appreciate it if you would stop pointing that out. : ) – CandiedOrange Feb 29 at 10:43
Rail Guns are great at large scale! I think the advantages as ship borne weapons are clear. And at large scale, power density isn't an issue... Just power. I just don't see them replacing handheld firearms any time soon. – David M. Perlman Mar 1 at 14:30

Note: I had the same thought as Alex S, and so this would have been a comment on his answer, but I don't have that right yet.

CYBERWARFARE. Alex has already talked about installing some sort of virus to cripple colony X's infrastructure or something else of the sort.

I also thought about another type of cyber warfare- emotional warfare. 25,000 people is a super tiny population group. Assuming that Mars culture is anything like current culture today, they will want to be connected to the internet. Most of the internet (I am assuming) will involve some sort of communication with earth. Which allows colony Y many forms of attack they can make on colony X.

Ransom DOS attack - If colony Y has some pretty good hackers, they could find some way for colony X to be completely cut off from earth (and the entire internet resources) or anybody else unless they do what colony Y wants.

Man in the middle (MITM) attack- This one is probably orders of magnitude harder than the DOS attack, colony Y might be able to get in between colony X and earth and do changes/blocks/insert messages into their communications.

Propaganda attack- This is the attack which I would see working the best. If colony X is open and free with what media its citizens are allowed to consume, this gets much easier. But unless colony X is, in fact, completely tyrannical and all-encompassing, there will be ways to hack/subvert the system to get the message to all of its people. Propaganda is what we are talking about- convince the people of colony X that colony Y is in very dire need and that they can help, but whoever governs them is wanting them to die. Or frame the leaders in such a way to stage a revolution. Get the people of colony X to do the work for you.

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By far the easiest method of cyber attack is social hacking. Get a man inside working for your colony by using confusion, greed, love or fear, and pretty much any security can be worked around. – diynevala Feb 27 at 18:29
Good answer, welcome to the site. – James Feb 29 at 14:39

I have a few concerns with the premise

My first concern is if Colony X has found unobtanium (I presume a very valuable resource), and enough time has passed that they are using it as a monopoly resource, they would have some form of militarization to protect it. If they believed colony Y would be able to just take them over, they probably wouldn't be attempting a monopoly.

Colony X would probably have assault rifles to defend their economic boon (unless they were incredibly naive or stupid). I imagine space at this time much like the wild west, where you need to defend what you have. I also don't see how colony Y would have the economic power to overcome that advantage through militaristic means.

To my answer:

There was a patent that was recently accepted for a self-destructing bullet (when it goes beyond a certain range). In 100 years, something like this could develop for use in the application you describe for an actual assault on the colony.

If somehow they were absolutely not allowed assault weapons there would probably be non-lethal weapons like beanbag guns, rubber bullets, taser guns, nausea inducing strobe lights, and various gasses. I know you requested projectile weapons, but I honestly think a weaponized handheld laser will be possible within that time frame. I suppose SpaceX could control what resources were available, but with 3d printing technology going the way it is I really doubt they would have too much control over established colonies.

We also need to assume that a militarization of colony Y would be fairly evident through espionage, and would give colony X a chance to prepare. In fact, given the scenario you have laid out, colony X may even find allies in the unrelated colonies (as there are treaties in place). This may not be the case if every other colony needs unobtanium too, and colony X has alienated all allies.

I think the best route of attack for an economically weaker foe is guerrilla tactics. Colony Y could work to subvert the economic power of colony X by attacking shipping routes, ruining mining infrastructure, hacking of computer systems, generally being a nuisance, and working to destroy any strategic relationships that colony X has (colony X probably needs mining equipment from colony Z, so if colony Y ruins that relationship, colony X loses its ability to mine long term).

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In the arena of projectile weapons, there are many options which do not risk penetrating a wall, yet have enough stopping power to incapacitate a soldier. These are generally lower power rounds with less effective range than a normal round, but ranges should be very limited in a small Martian habitat.

For example, the Glaser Safety Slug is a pistol or rifle bullet which fragments into birdshot at very high velocity. It will penetrate clothing and flesh, but not material much thicker than drywall or sheet metal. It was used by US Air Marshals on airplanes to avoid decompressing the aircraft.

Similarly one can use shotguns firing shot and hollow point bullets. Any projectile which spreads the impact over a wider area will have less penetrating power while still be an effective short range combat round.

The downside is the reduced penetration capabilities of these rounds mean they would be ineffective against body armor.

In the explosives department, traditional fragmentation grenades and anti-tank weapons would be avoided. Concussion grenades, which kill by explosive power alone, could be used though may result in small penetrations. Stun grenades and all sorts of gas, smoke and chemical grenades would also be safe.

Small penetrations of the pressure seal would be used to the attacker's advantage. Safety would require that small punctures in the walls would not grow or result in explosive decompression (sorry Hollywood, Mythbusters did a whole show on this). This could be used to the attacker's advantage.

If the defenders lack breathing gear, an assault team could be equipped with breathing apparatus, doesn't even have to be a full space suit. They'd deliberately make small penetrations in the outer wall to cause the pressure to drop. The defenders now must withdraw, surrender, or pass out. Once the oxygen pressure has dropped to a level sufficient to incapacitate, but not kill, the inhabitants, engineers would go in to make quick patches and repressurize the area. Medics would see to the civilians.

Even if the defenders have breathing gear and large numbers of civilians, siege tactics can be applied. Surround their habitat, cut off their air and water supply, puncture their outer wall to reduce the pressure (again, low enough to make people pass out, high enough to keep them alive), and wait. Depending on how good their emergency supplies are it could be a matter of hours or days before they're forced to surrender or pass out.

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A targeted strike by a small team of pressure suited marines armed with low-velocity projectile weapons.

You want to take out the government, while leaving the colony intact. You need precise, extreme violence, close range, perfectly targeted. This means you need humans. Humans with guns.

Send in a small team undercover. Perhaps they are disguised as visiting diplomats. Once inside, they give their minders the slip, and take out the supreme council.

Low velocity rounds, and accurate headshots would prevent random depressurisation, but just in case, the team would be equipped with pressure suits.

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After reading half-way through your question, I though, "This will be easy, just one tiny hole in the wall and ...." Then I read that you specifically exclude this. Drat.

Instead we have to go for the generators (or solar panels or wind turbines or whatever they use). Leave them just enough energy for life support; not enough for lights, computers, and other amenities. Make sure they understand you won't turn the power back on until you get your unobtanium.

How? You want an EMP weapon. Not the nuclear variety, but rather something like the jamming pods on military Electronic Warfare aircraft. The weapons can be tuned/ focused to affect your adversary's ability to produce and transmit electricity. With only a little target practice, you can get it just enough to make life miserable for them, but not outright kill them.

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Destroy their computers (and other electronics) with EMP and trade replacements for Unobtainium? (Building the EMP generator must be "top secret" since building shielding is so much easier.)

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Sabotage. Find some way to turn members of the other colony in to your secret agent. Destroy or otherwise contaminate a large portion of their spare, air supply or water supply or fuel. Try to make it as untraceable as possible so there's no actual evidence incriminating your colony. Then offer the colony your spare supplies to help them survive until the next shipment from earth. In exchange they'll give you whatever resources you want.

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Since we have 5000 years of recorded history to draw from, you can expect all kinds of strange ideas being floated prior to the commencement of hostilities. However, most of the good ideas were discovered quite early, so we will see adaptations of these to reflect the Martian environment.

First of all, attacking enemy logistics is going to be key. An unsupported enemy will be unable to threaten you, and have difficulty defending their own territory. Many posters have mentioned attacking enemy systems through cyberwar and disabling generators/solar farms etc. This can be extended to attacking their means of communication, both electronic (disabling or destroying comms towers, antenna farms, satellite uplinks as well as roads, rails or vehicle launch pads).

The next phase will be to establish physical control over areas. Soldiers on the Martian surface will be much like modern soldiers working in the high arctic, or Finnish soldiers during the Winter War: the environment will be far more dangerous than the enemy. Anything to make it harder to operate on the surface will work to your advantage, including obstacles like minefields or wire, and covering approaches with snipers or marksmen.

Finally, when it comes to entering protected areas (like the enemy colony site), engineering support will be needed. Breaching charges to get through walls, portable airlocks and air systems to fix and secure areas you now control, technical experts to secure the cybernetic systems and extend the control of the invading forces.

For actual combat within the colony domes, the both sets of forces will most likely use weapons and systems which cause the minimum amount of collateral damage to the area the fighting is taking place. Soldiers will use weapons similar to 12 gauge shotguns (militarized weapons like the AA-12) and concussion grenades rather than fragmentation weapons. Going through walls will be more a case of engineers hand placing breaching charges than firing RPG like weapons to blast holes. A lot of combat will probably take place using robotic devices to scout ahead, map out weak points to be breached or even do low level tasks like sever electrical power lines and IT cables to prevent enemy forces from having any means to mount a cybernetic counter attack.

(edited since the last half of the answer seems to have not uploaded).

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Are you ruling out civilian casualties, or just ruling out annihilating a colony?

Obvious possibilities:

Tasers. Not going to destroy the city walls or cause casualties, but will disable opponents. Drawback: Only disables people for very short periods.

Phasers set on stun. Okay, probably not going to happen in this time frame.

Rubber bullets. Like tasers, probably not effective enough.

Weapons that fire poison darts. Such weapons aren't in general use because if you want to kill somebody, a conventional gun is cheaper and more effective. But they're around. Spies use them occasionally, etc.

Poison gas. Oh, like poison darts, the nature of the gas is debatable. Does it kill, incapacitate, render unconscious, etc? Any of those would work. Something that makes people too sick to fight for a few days is probably enough to let you take over the city and throw the die-hards into prison camps.

But it seems to me there's a big problem with the premise: If the Rules of War in this culture rule out blowing holes in a city's pressure wall, how do the attackers get inside to use their less-destructive weapons? Couldn't the defenders of a city just close all the airlocks? Or even if the attackers can break open the airlocks, so they come through these narrow openings where the defenders can be waiting for them and pick them off one by one.

I'd say the more likely scenario is: We don't try to restrict the types of weapons. Rather, we agree that all colonies are "open cities". That is, all combat is conducted out in the "wilds". If you break through the enemy armies and reach their city, the city opens its door and surrenders without a fight. The alternative is that you blow a whole in their pressure wall and they all die. Many places in history have adopted this policy to minimize civilian casualties. It works as long as both sides respect it. Which, admittedly, is an iffy thing.

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Cyber warfare

All of the colonies undoubtedly rely on computers for pretty much everything. Colony Y merely needs to find a way to cripple Colony X's infrastructure so that they are forced to agree to Colony Y's terms for survival. The best part is that this can be done in a way that hides Colony Y's guilt, making the problems seem like mere accidents. Indeed, Colony Y is the white knight. Offering a discount on Unobtanium is a small price for Colony X to pay in exchange for survival.

This has actually already been done. In 2010, a computer program now known a Stuxnet was discovered to have infected computers around the world, but particularly in Iran. Stuxnet did nothing to normal computers, but for computers connected to devices which direct the processing of nuclear material, it caused these devices to break down, halting the enrichment of Uranium. To people in these nuclear facilities, it seemed that this was an accident. But it was Stuxnet. It is suspected that Stuxnet was developed by the American and Israeli governments.

This leaves the problem of how to install malware onto Colony X's computers. Surely the colony has a good firewall. Just how Stuxnet came to be installed on Iranian nuclear facility computers is unknown. But there are some ideas. In a study I saw recently (and I wish I could remember where for a reference), experimenters left a CD labeled "2013 payroll" in public locations of large companies, as though an employee from the accounting department had misplaced it. An astounding 100% of the CD's were discovered and loaded into company computers, probably by nosy employees hoping to see their coworkers' salaries. The CD could well have contained malicious software which, having been loaded directly onto a company computer by an employee, bypasses most of the company's security. Thus we see that the most vulnerable part of a computer network are the humans who use it. Through a similar nefarious scheme, I believe Colony X would beg Colony Y to buy their Unobtanium just to stay alive when their computers go nuts.

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Surround the city at a suitable distance, killing anyone attempting to arrive or leave the city, also preventing supplies from arriving. Depending on how unwilling the surrounded city is to surrender, this might turn out pretty violent.

Because the fighting happens a good distance from the city, there is no risk of damaging the city's life support. Also if a notice is given, most civilians will stay in the city and only military will fight.

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Except, any long term Martian colony will likely be self-sufficient. – DJMethaneMan Feb 29 at 13:59
@DJMethaneMan Even if they are self-sufficient for food, they will eventually be bothered by not being able to trade anything or go anywhere. It would be a like a prison, and prisoners tend to try to break out. – jpa Feb 29 at 17:53

A non-lethal but highly contagious biological agent would serve you well in crippling a population. Enclosed colonies are highly susceptible to disease; if you can find a way to slip a modified flu virus past the sterilization barrier you'll be able to strike while the whole colony is too sick to resist.

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The unobtanium mine is only accessible from Colony X via a tunnel network, though it is actually located a fair distance away from the colony - DJMethaneMan

Claim jumping.

Here's an old weapon that you can give a sci fi twist. You have these established colonies duking it out letting you depict the story of developed colonies. How would you like a chance to tell the story of forming a new colony?

Colony X has carefully made sure to access the mine only through the exploratory underground tunnels that originally leveraged off of Colony X's life support. Who needs to live in a bubble when you can tunnel? By keeping all signs of mining off the surface not even most Colony X workers know where the mine is really located.

Colony Y uses the oldest weapon, information. They develop a spy in Colony X who has some close personal tie to someone from Colony Y. The spy works to learn the location of the mine and, once that has leaked, Colony Y uses another weapon you've already mentioned, colonies. They start colony Z, right on top of the mine.

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If you're interested in this, read this free online novella by James S. A. Corey, a prequel to The Expanse novel series that's now a TV series:

One good insight here is that distance is measured in time. If one side of the conflict has much faster ships, that overwhelms almost all other advantages.

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Welcome to the site, David. Could you expand on this answer some? Link-only answers can become invalid if the linked source goes away. We ask answers include the relevant material here. – Frostfyre Feb 27 at 18:12

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