Sci-Fi weapon that can kill people through armor, but doesn't damage starship hulls?

I have been trying to come up with some kind of small arm that could be used in a science fiction setting with the following two characteristics:

1. It is designed so that it won't put a hole in a spaceship's hull and vent all the air.

2. It is still capable of killing people wearing armor.

Unless the answer is that ships all have hulls that are an order of magnitude thicker than anything a human could actually wear, this is a tough one. Because if a weapon were designed to not damage common hull materials at all, people would just wear armor of the same materials.

So far the best I've got is some kind of 'lightning gun' which electrocutes people through their armor. Though I suspect armor might act as a Faraday cage.

Is there some kind of particle beam or spectrum of radiation that can kill someone through metal quickly to be practical without damaging the metal?

• Comments are not for extended discussion; this conversation has been moved to chat.
– L.Dutch
Jul 29 '20 at 16:04
• This question reminds me of a Judge Dredd comic in 2000ad where the "Sovs" had electromagnetic weapons which could shoot through obstacles and armour. Judge Dredd defeated them by continuing to advance more rapidly than the Sovs could adjust the range/focus of their weapons. Only reference I can find is here: judge-dredd.fandom.com/wiki/War_Games?file=Sov_wars.png Jul 29 '20 at 16:14
• @JeremyFriesner Too much work. Just transport a few fingers volume worth of their brain or heart outside of their armour. Jul 29 '20 at 22:28
• wearing armor. "Armor" is a pretty broad term. What does this armor protect against? If we don't know that, how can anyone answer? Are we talking about a bronze breastplate, or a radiation-hardened suit of sci-fi power armor made with unobtainium and magic fields? You say it's made of "metal" - that doesn't really narrow it down. What kind of metal? How thick?
– J...
Jul 30 '20 at 14:14
• "Unless the answer is that ships all have hulls that are an order of magnitude thicker than anything a human could actually wear, this is a tough one." Spaceships have to deal with radiation, space debris, they probably want to survive reentry, etc. Honestly I would be quite surprised if typical spaceship hull wasn't an order of magnitude stronger than wearable heavy body armor. Jul 30 '20 at 15:50

Kinetic impactors

Imagine a knight in armour. You have no weapon capable of penetrating the armour. What do you do instead?

You beat them to death with a big hammer.

The human body is squishy even if it’s inside an invulnerable tin can. If you accelerate it fast and hard enough all sorts of unpleasant things will happen to internal organs as they ram up against bone, the armour, and each other.

So your gun basically launches a little missile (self propelling to protect you from recoil) that carries a lot of momentum but is made of a material that will elastically deform on impact. Imagine a beanbag round, but filled with lead and with a rocket on the back.

The aim isn’t to penetrate the armour. It’s to hit the opponent so hard they fall unconscious or die even though their armour is unscratched. As cricket and baseball players can attest: getting hit in the face by a relatively lightweight object moving at subsonic speeds hurts even if you’re wearing protective gear. Now imagine it’s got a missile on it and it’s a bag of lead pellets. No matter how tough your helmet is you won’t be getting back up.

But if it impacts the hull of the ship? It might make a dent. At worst the munition explodes and fires pellets everywhere that are harmless on their own.

Oh, and if you make it right you can even recover and re-use your ammo, or make it a drone capable of incapacitating multiple opponents. Give it a mythical code-name. Shape it like a hammer. Maybe ‘throw’ it for personal propulsion in space...

Wait...

• Don't forget about spalling! If you hit the hull, a thin layer of hull flakes off the outside and flies off (relatively) harmlessly into space. If you hit someone's armour, that same layer of metal flakes acts as high-velocity shrapnel, turning their body into chunky salsa... Jul 28 '20 at 12:39
• @Chronocidal spalling is not a significant concern with any reasonably designed suit of armor since the armor is not going to be metal against skin, but rather have an inner lining of textile layers like kevlar. Jul 28 '20 at 13:16
• @Nosajimiki "Chronocidal spalling" sounds like a great story idea... yeah, I know, it was just your comment back to Chronocidal, but still :) Jul 28 '20 at 16:06
• Damn, now I need to change my answer to chronocidal spalling rifles. A weapon that splays it's target out over time relative to the environments frame. So, as long as the ship is not accelerating, it will not be affected, but a target that moves around a lot like people will find itself in a very unfortunate situation Jul 28 '20 at 16:30
• A shiver is a piece of wood knocked loose from the inside of a wooden ship when the outside is hit by a cannon ball. These shivers would fly around and kill people. It's the origin of the expression "shiver me timbers!" Jul 29 '20 at 3:31

Well there is the Neutron Bomb, which was a nuclear weapon variant designed specifically to kill tank crews while limiting the physical blast damage to the area. I suspect it would be theoretically possible to build a gun designed specifically to fire neutrons at great enough intensities to harm humans... but it would be a really awful way to kill someone, because while it will incapacitate, it won't kill the target immediately. Death will take hours or days to set in.

• Funny, in fiction neutron bombs are generally depicted as instantly killing (even vapourising to dust and ash) organic targets while leaving cities and infrastructure intact. I guess the reality is far far less clean and pleasant. In hindsight, that should have been blindingly obvious. Jul 28 '20 at 8:59
• Neutron Bombs are just small nukes air-bursted high overhead... I'm pretty sure detonating one inside of a ship would cause very significant damage... also ships tend to have much better heat and radiation shielding than tanks by necessity; so, if you are thinking of setting one off near a ship to kill the crew, the radiation is unlikely to meaningfully penetrate the outer hull. Jul 28 '20 at 13:44
• We are talking sci-fi, if there were some sort of neutron beam weapon and not a bomb that could work. Jul 28 '20 at 14:15
• Neutron beam was also my thought - if the ship is covered or made from low atomic mass materials, it could survive the beam. The main problem is induced radioactivity in e.g. steel. Compact Neutron sources can be made from an alpha emitter radiating on a Boron disk. Edit: oh, it must irradiate through the spaceship, then it again depends on the material of the hull Jul 28 '20 at 18:57
• Though they'd be very similar to neutron weapons, one might also consider weapons based on Bremsstrahlung radiation Jul 30 '20 at 4:36

microwaves

Put plastic or ceramic in a microwave and it is just fine.

Put metal in a microwave and it sparks but won't be to worse for wear. You can dissipate heat in the metal to reduce the chance of burning.

Put a human or an animal in a microwave and you get a dead person or dinner (or both if you are a cannibal.) The armor will be fine, but the human inside will be roasted.

• Surely the armour that the crew are wearing will just act as a faraday cage, and protect them? (Like how the radiation doesn't get out of the microwave and boil your eyeballs when you heat up your dinner) Jul 28 '20 at 12:33
• @Chronocidal Depends on the armor. Modern armor is mostly polymer textile and ceramic based containing little if any metal. Jul 28 '20 at 13:53
• @Nosajimiki True, but OP has specified that the weapon needs to operate through metal (and even mentioned the "Faraday Cage" issue as part of the reason why they wanted an alternative to their "lightning gun") If nothing else, Nasa are already looking at potentially adding radiations shielding to their Space Suits Jul 28 '20 at 14:00
• @Daron It doesn't; the metal suit forms the Faraday Shield. The rapidly oscillating electromagnetic field is just what's blocked. If you want to know exact details on why it's blocked, go ask someone on Physics - but, it does, and that's why they're built into Microwave Ovens as a safety feature. (This situation is just that, but turned inside-out) Jul 28 '20 at 16:26
• @Daron A Faraday Cage is a fully-enclosed Faraday Shield. It's the difference between a sheet of cardboard (Shield) and a sealed cardboard box (Cage) Jul 28 '20 at 19:03

"Gravy gun".

(The name gravy gun comes from the Schlock Mercenary webcomic; the description below matches the description and technical glimpses disseminated in the webcomic)

Once you have artificial gravity, weaponizing it is reasonably straightforward. Point a gravity plate against someone, and they'll immediately feel a force towards the plate (or in the opposite direction). Due to the well-known F=ma relation, they will also be accelerated in the same direction.

Invert the polarity of the plate; the acceleration will be reversed.

Nothing whatsoever happens to the target because (and only as long as) it's completely immersed in an isotropic field.

But if you can achieve spatial anisotropy (using several parallel beams of different polarity) or temporal anisotropy (using wavelengths of the same order of magnitude as the target's size), the target will experience a violent shaking, against which nothing (except an accurately countermodulated grav field of the same local intensity) will work.

"Violent shaking" can go from disturbing, to more or less permanently incapacitating, to lethal. At the same time, the effect is much less dangerous on inanimate objects.

...and, immobilizing foam.

Used as boarder-repeller, the foam gun shoots what is essentially fast-setting superglue. The foam has some additional features though: it expands very much, resists to very high temperatures, and is thermally insulating.

This means that people in power armor cannot free themselves, and remain encased in a substance that, in a comparatively short time, will cause them to pass away and even die from heatstroke (with no way of getting rid of extra heat, the enclosed volume's temperature will just go up and up). The victims' situation can be monitored from outside using microphones, and the appropriate solvent administered to capture the victims once they are well and truly incapacitated.

• I liked this answer just as much before the edit that changed it from suggesting a "gravy gun" Jul 28 '20 at 15:17
• @AndrewBrēza Well, if you've got portal technology, a gravy gun might be effective... Get a portal inside the armor and pour. I can't imagine drowning in gravy would be a pleasant way to go. Jul 28 '20 at 15:53
• A similar concept was depicted in the book Deathworlders, where the ship's gravity plating was used as a tool/weapon to stop and incapacitate the boarders. If you can turn a long corridor into an empty shaft while the boarders are in there... Jul 28 '20 at 16:34
• A weaponised gravitic weapon has several possible types of effect that I can think of. The "wibble field" where spacetime is distorted into interesting shapes, causing objects and body-parts that pass through it to distort and/or rip apart gruesomely, the "black-hole gun", where everything is drawn forcibly towards (or away) from a central point, which may crush or explode a target, or the "holepunch", which uses Shear forces to punch a small hole in the target using its own mass. These are universally lethal, gruesome and absolutely will do terrible things to starship hulls behind the target Jul 29 '20 at 10:12
• Elaborating on the holepunch, essentially it's a grav-plate about three or four inches across on a pistol or rifle arrangement. But you amp the power up to about 100gs. The result is an invisible beam that passes through every known material and applies enormous force along its length. point it at someone and watch chunks of them get physically torn away and splattered across the bulkhead behind them. If you don't have the power-supplies to make a continuous beam, a millisecond activation is still enough to punch holes in someone. It's a thoroughly violent weapon. Jul 29 '20 at 10:18

Sonic weapons

Although Infrasonic weapons seem to have been overhyped, they can still cause enough of a disturbance to incapacitate you momentarily. With enough power (>200dB from memory) a regular sound wave can also kill you, by increasing pressure in your lungs and either bursting them or causing an embolism.

• Bonus if the 200db sound you play is actually Killing Me Softly With His Song. Jul 28 '20 at 16:03
• This weapon was used in The Dark Forest to perform exactly the function described by OP, kill the crew, save the ship. It was called an "Infrasonic H Bomb". Armor would not stop it, though it would be countered if there were a vacuum inside the ship. Jul 28 '20 at 17:26
• OPs question mentions ships, so presumably this is in space (i.e. vacuum), making sound wave transmission impractical. But an electro-magnetic weapon that causes all of the metal in a ship to resonate at infrasonic frequencies might be plausible enough for OP's purposes. (Bonus: Vibrating everything in the ship at low-but powerful frequences (< 20hz) would wreak havoc on the structural integrity of everything. Shelves falling off walls, data/plumbing/electrical connections failing, optical systems losing alignment... you name it!) Jul 28 '20 at 17:31
• I assumed it was in the context of a firefight inside the ship. Jul 29 '20 at 16:04

It won't work but - Gamma Rays: will penetrate several centimeters of metal will relative ease. So a gamma ray laser (if one could be built it would be enormous) firing from one ship at another would have that effect i.e being lethal to humans but leaving amour intact. But;

1. In the process atoms in the targeted amour will undergo transmutation into highly radioactive elements. So while you could kill the crew and capture the ship you would have the long term effects of radiation poisoning to deal with - at least in those parts of the ship directly impacted by the beam.

2. Did I say they were huge? there won't be anything such as a hand held gamma ray gun you can use. Not realistically anyway. See the excellent 'Tough SF' and 'Atomic Rocket' web sites for some of the complexities.

If you want to incapacitate but not kill armored enemies then-

a weapon for boarding actions in a direct firefight could be a combination of lasers (to ionize the air between you and the target) or particle beam weaponry to fire a 'pulse of electrical energy. The key I 'think' would be to penetrate at least the outer surface of the armored suit so that current and EMP effects can fry internal circuitry and doesn't discharge harmlessly outwards.

Alternatively just go with something like a high tech smart projectile or grenade designed to deal with the kinds of armor you know the enemy wears i.e. a relatively large but low impact weapon that sticks or attaches to the target, drills in and discharges.

• In the process atoms in the targeted amour will undergo transmutation into highly radioactive elements. This sounds wrong to me. What is your reason for thinking this? I'm a gamma-ray spectroscopist by training, and as far as I know it's quite difficult to get transmutation induced by gamma rays in the 100 keV-1 MeV range. For one thing, nuclear transmutation will occur only at specific energies corresponding to the difference between nuclear energy levels. A bigger issue for the OP is that death would probably take a matter of minutes, but I think they want a gun that goes zap, you're dead.
– user77458
Jul 28 '20 at 18:39
• I agree with @BenCrowell, but another matter is that intense radiation will damage the structure of the ship's materials, mainly by ionising atoms and damaging molecular bonds. The damage is dependent on dose and materials, but you would need a high dose to deliver a fatal amount of radiation to the people inside a large volume. If the attackers need to use the ship after the attack, it will be a problem that all electronics will probably be dead too. Jul 28 '20 at 19:22
• Maybe use some sort of remote detection of the people inside (radio waves maybe), so radiation could be targeted, rather than evenly distributed Jul 28 '20 at 19:25
• @Stefan Gamma rays generally do little damage to bulk materials. Electronics are also much hardier against gamma rays than living tissue. A kilorad, lethal to humans, might disable a few unusually susceptible circuits in the short term, but much of gamma ray damage to electronics anneals away over days. Jul 29 '20 at 16:24
• P.S. Ben the the process I was thinking of is called photo-disintegration which I believe can result in the transmutation of some elements into radioactive counterparts.
– Mon
Jul 30 '20 at 8:57

Because if a weapon were designed to not damage common hull materials at all, people would just wear armor of the same materials.

There is a bit of a logical fallacy here since a hull is designed to protect against the hazards of space whereas armor is designed to protect against the hazards of weapons. This means that your body armor is likely much better at stopping the weapons it will encounter from a boarding party than the ship's hull, not just using the same materials. So, creating a situation where they both have good reason to be made out of the same thing actually gives your hull the best chance of holding up. IE: if a soldier's armor can't be thicker than 1" but the ship's armor is 3" thick, then the ship can take hits that the soldier can not.

A good guideline when it comes to worldbuilding is to assume that if you are going to give one side a ubiquitous weapon system that the other side will adapt to defend against that type of weapon. So, considering many of the weapons proposed so far, many of them either have simple countermeasures, or the counter measures would make you have to scale the weapon up until it becomes a threat to the hull itself:

• Kinetic Impactors can be countered by Reactive Armor meaning any slug strong enough to beat reactive armor will be devastating to a non-reactive inner hull surface.
• Cyber attacking can be made impossible by using closed systems and single purpose chip sets; so, would not make for a reliable primary offense
• Chemical Weapons can be countered by MOPP gear which as it turns out, your standard space suit already functions as pretty darn well.
• Gravity/Sonic resonance weapons could be countered by armor that can create an inverted resonance much like noise cancelling headphones. So, the power sources between weapons and armor would escalate until you have a ship breaching weapon.
• Electrolasers can be countered by a well insulated and grounded suit of armor or by purposefully venting the room; so, they would not make for a reliable primary offense.
• By the time you are looking at nanoswarm technology, the idea of infantry will be completely obsolete which I think defeats the OP's intentions. So, while nanobot bullets have some cool factor, why not just flood the ship with grey goo and leave your people at home?

The list really goes on and on, so for brevity sake I will move on to what I think the most reliable class of infantry weapons will be here: Thermal Weapons

The biggest advantage of thermal weaponry is that a ship's hull already considers thermal survival a primary objective. A general purpose starship must insulate itself from solar radiation, the cold of space, and atmospheric re-entry, meaning that the hull should already be well designed to survive your stray fire. As your armor and weapon tech escalates, so too will your ship's hull.

But more important than this is the relationship between how hot you need to make the hull to melt it, and how hot you need to make someone's armor to kill the person on the inside. People die from heat at much lower temperatures than most metals melt; so, your hull and outer layers of body armor may have a melting points in excess of 3400°C, but if you heat up a suit of armor to just a fraction of that, then the person/electronics inside of the suit will be very quickly killed/destroyed. So following this logic, your ship's hull can even be a bit even thinner than personal body armor and still resist a stray shot.

Is there some kind of particle beam or spectrum of radiation that can kill someone through metal quickly to be practical without damaging the metal?

High Energy Lasers (HELs)

There are many ways to make things hot at a distance, but High Energy Lasers are perhaps the most controllable. Recent advances in solid state laser technology are proving that kilo-watt ranged hand-portable lasers will soon be a thing; so, the tech to weaponize HELs at infantry scale should be reasonable for any space-aged civilization.

Much like Joe Blogg's answer, the key here is to spread out the area of effect, but lasers can do so in a much more controlled manner. A highly focused laser will cut right through metal killing someone very quickly, but in a ship boarding operation, your lassers could have a setting that increases the spread of your beam; so, instead of heating a single point to thousands of degrees; you could heat a large portion of your target to hundreds of degrees. This will not damage the metal but it will result in an instantly debilitating and relatively quick death for the person on the inside.

HELs are also a really good foundation for future ubiquitous weapon systems because the same weapon can be adapted to many situations, not just the one you are asking about. A wide beam gives you a safe boarding weapon and a more forgiving target area (like how a shotgun can still hit a target even if your aim is a bit off). A narrower beam can give you better range and accuracy more like a riffle. It's power level can be scaled up or down without swapping ammunition/gun barrels. It can be used to cut through or weld shut metal doors. You can even rig one to second as an electro-laser giving you a stun setting.

It's versatility outside of just being able to be used in a boarding situation will probably make it the main weapon for most space infantry forces.

• End User Warning: Will not function in vacuum. Jul 28 '20 at 8:33
• @JoeBloggs That is a good point. I assumed since the OP is worried about hull breaches that he was planning on fighting in atmosphere, but since no plan survives contact with the enemy, that could be a problem. Expanded my answer to include a solution to this. Jul 28 '20 at 13:36
• @Nosajimiki The whole reason why you have to worry about hull breaches is because it's in the vacuum of space - a hull breach in atmosphere wouldn't be too much of a problem. Jul 28 '20 at 14:05
• @TheDaleks I think what he is hinting at is that a room could be vented without a hull breach. For example, if you force your way into a shuttle bay, the defenders might suck the air out of it rendering electro lasers useless. This is not the same as a hull breach where you lose your air supply and there is no getting it back so everyone dies. Jul 28 '20 at 15:14
• @JonTheMon Most bullets don't hit a flat surface, they hit at an angle; so, instead of blocking the weapon's full force, it just pushes it aside making it effectively glance off of you. Also dissipating the impact over a larger area does make you harder to kill. It's like the difference between getting hit by the flat or the edge of a cricket bat. Both are blunt force trauma, but one will break bones whereas the other will mostly just cause some minor bruising. Since the armor will spread the force more than the hull, the hull is still taking a more concentrated force. Jul 29 '20 at 6:01

Depending how "hard" your SF setting is, consider a weapon that remotely "scrambles" matter. It produces a fairly narrow beam (a few millieters diameter ought to be enough) within which matter is randomly redistributed, like scrambling an egg. Since this happens on an atomic scale, it will have little effect on a metal hull -- the metal will simply reweld when the beam shuts off. A composite material will be weakened, because the fiber strength will be compromised, but this would only cause leaks in things like fuel tanks and pressure vessels, not (usually) catastrophic failures.

But in a living body, the scrambler beam will kill and homogenize the cells in the beam. This isn't just a hole, like a through-and-through bullet wound, though; since the beam and body can't be kept perfectly still with relation to each other, the result will be a slash of dead tissue. with all its structural integrity destroyed -- so if it passes through any blood vessel, the blood pressure will force its way out along the scramble channel. A shot to the head will be like a stroke. A heart or arterial hit will be near-instantly fatal, a spinal shot -- well, you get the idea. It's like a bullet without the ability to be blocked by material shielding.

Now, enough matter will absorb the beam's energy, so a ship hull will generally protect those inside from a hand-held scrambler, but one of these is deadly through any armor that will fit through normal corridors and doorways, at least until its power cell gives out.

• So, a Dalek extermination beam? Jul 28 '20 at 17:00
• Too long since I saw a Dalek exterminate a human. Nor was their mechanism and effect explained, anywhere I recall -- just "zap, you're dead.." Jul 28 '20 at 17:04
• Word of God is that it works by randomly re-arranging the matter in its target. Jul 28 '20 at 17:24
• Well, then Great Minds Think Alike. ;) Jul 28 '20 at 17:39
• Davros would be proud. Jul 28 '20 at 18:48

The hull of the ship is made of material that quickly self-heals any small holes punched in it, preventing full de-pressurization events. Humans could wear this material as armor, but it wouldn't help, because while the armor will heal, the human inside would also have a hole in them that is much more difficult to heal, if they're not already dead.

The explanation for the self-healing property could be many things. Or you could just not explain and let the reader wonder. It could be nanobots, or it could be material that swells/expands when distressed, so the material around a newly-torn hole will swell up and pinch the hole shut. This would be a very useful property for spaceships to have in general. It also explains why ships aren't being destroyed by high-speed collisions with micro-meteorite debris from previous battles.

• The hull could also be filled with a pressure differential activated polymer similar to what they use to repair buried industrial pipelines. youtu.be/uYeI_QZ1s3A Jul 28 '20 at 16:39

More generally, anything that would warm the surface of the armor anywhere between 300°C and 1000°C would kill the person inside, but leave the armor (and the hull) mostly undamaged.

It would also probably fry the electronics of a robotic soldier

• In Aliens, the marines switched to flamethrowers specifically to try to prevent damage to nuclear reactor equipment from bullets, so anything from Molotov cocktail to napalm should be effective without dangerous to the hull. Larry Niven's first contact with the Kzinti resulted in them using an inductive heating weapon to cook them alive and protect the tech of the ship so they could assess it. Jul 31 '20 at 2:26

You are thinking in entirely the wrong sort of categories if you're thinking of rays and projectiles.

Best approach would be a cyberattack hacking into your opponents control systems and causing them to suffocate/freeze/boil/over-oxygenate etc. This will work through armor- in fact, the more sophisticated power armor they have the better - or spaceship hulls without necessarily damaging them.

• For this very reason no sane designer will put a wireless transceiver which connects to the control systems if battlefield hacking could be a thing. Jul 28 '20 at 16:32
• @Jan Dorniak I bet this could still be useful for civilian ships, as any pirate would be delighted to use this. And since when are designers sane? :) Jul 29 '20 at 3:38
• The space pirate held a gun to the defenseless freighter captain's head as he whispered the last words he'd ever hear... "Let me guess, you let your nephew set-up your router." BANG! Jul 30 '20 at 18:12

For every physical mechanism you can imagine, some sort of countermeasure can be created. We see this already in armoured warfare, tanks are encased in heavy layers of composite armour, often have reactive armour over top and more recently have active defence systems to attempt to spoof or shoot down enemy weapons inbound. To overmatch these systems anti tank weapons are now some of the most powerful systems on the battlefield, APDS-FS rounds travel at velocities of 1200m/sec or more, and HEAT warheads are so powerful that the secondary effects of the explosion are considered useful ways to eliminate enemy infantry or even light armour and improvised fortifications (HEAT-MP rounds).

Whatever gets through the protection surrounding the tank will destroy the tank itself and have an almost 100% chance of killing the crew as well. Spacecraft will have similar issues at much greater scales: kinetic energy impactors can be moving at tens to hundreds of kilometres/sec, and in space, laser weapons could be powered by immense systems (imagine a Free Electron Laser with an accelerator a kilometre in diameter, powering an X ray laser capable of vapourizing metal, ceramic or carbon fibre in milliseconds at a range of one light second. If I have to defeat layers of armour and protection, I'll eventually be carving up your spacecraft like a turkey, regardless of the advantages of taking it whole.

Cyber warfare and ECM are possibilities, but any halfway competent force will already have taken this into account, and will have strong countermeasures in place. So we have to look at a different avenue of approach.

Why are we fighting a war? Von Clausewitz tells us "War is the continuation of politics by other means". Military writing, philosophy and even fiction as far back as the Iliad tell us the ultimate goal of warfare is to impose your will on the adversary. But do we need to use kinetic means to do so?

Consider the idea of "4GW"

"Fourth-generation warfare (4GW) uses all available networks -- political, economic, social, and military -- to convince the enemy’s political decision makers that their strategic goals are either unachievable or too costly for the perceived benefit. It is an evolved form of insurgency. Still rooted in the fundamental precept that superior political will, when properly employed, can defeat greater economic and military power, 4GW makes use of society’s networks to carry on its fight. Unlike previous generations of warfare, it does not attempt to win by defeating the enemy’s military forces. Instead, via the networks, it directly attacks the minds of enemy decision makers to destroy the enemy’s political will. Fourth-generation wars are lengthy -- measured in decades rather than months or years".

"The Sling and the Stone" Col. Thomas Xavier Hammes USMC (Ret)

Modern day Russia and China have spent a considerable amount of time looking for ways to disrupt or defeat adversaries without the use of large scale armed conflict. The Russians have developed what is known as Hybrid War, while the Chinese have a somewhat related concept called "Unrestricted Warfare"

Consider Hybrid Warfare

The Russian commander can pick one, several or all of these actions as he sees fit. Unlike Western concepts of warfare, there is no need to "stage" or synchronize effects, there is no expectation the economic actions are followed by anything in particular, the commander may choose whatever effect he wants.

Chinese unrestricted warfare goes even farther, essentially weaponizing everything possible. Stock market trades and currency manipulation can be equally valid as assassination or engaging in "lawfare". Current events where Chinese nationals attempt to influence people in education through "Confucius institutes", or the 2015 Chinese "hack" of the OPM Database which identified every American with a security clearance or Australia's passing of laws to restrict the influence fo Chinese companies on Australian politics suggest a very insidious, long term process indeed. You might not even realize your nation is under attack, and one of the principles of "unrestricted warfare" is to ensure any individual action falls well below the threshold of triggering adversary actions, especially military action. It is death by a thousand paper cuts.

So if I want to take your spaceship without damaging it, I should be preparing the ground well in advance. The crew should be confused or demoralized about the mission, and unable or unwilling to take effective steps to prosecute their mission. Going even farther, the ship might never set out, as the dockside is paralyzed by lawsuits preventing it from being outfitted, or political scandals overthrow the "hawk" faction of the ruling political party.

Victory is mine, and the amount of shooting I had to do was minimal (there will be a few hold outs here and there).

So I got the spacecraft and neutralized the crew - by attacking their will to fight.

Chemical weapons.

Your ship won't care about mustard gas. Your enemies will be long dead by the time you finish betting on how many live in there.

You don't need to kill all of them. Mow down enough of the enemy crew and you can seize the ship with ease. The survivors, who managed to get the suits and gas masks in time, will surrender....or get into the reactor and try to blow it up and take REVENGE!

• Wouldn't airtight suits with respirators be a must for any boarding party in space ? Jul 28 '20 at 14:19
• And the defending party may not have suits for all, may not be trained to do so, may not expect to even have to deal with that situation. Real scenarios of bio attack trainings proved disastrous. The soldiers messed their masks and lost vital parts of gear. Combine it with a short time frame to prepare and you got CHAOS. Capitalize on it and your boarding party will have a cake walk mowing down the panicked opposition. Jul 28 '20 at 15:33
• I think chemical weapons are a good opening maneuver, but very rarely result in killing everyone so you still need some primary weapon solution for putting down those last few guys who got to thier masks in time. If you have nothing but mustard gas, but they have specialized firearms they can use inside of a ship, then those last couple of holdouts could still wipe out your entire boarding team. Jul 30 '20 at 18:07
• This answer also doesn't address how you get the chemical weapons into an enemy starship without damaging the hull. The question also said "people wearing armor". An armor which is designed to be used in space warfare would very likely be air-tight in order to protect against rapid decompression. Jul 31 '20 at 10:13

Neutron gun. The Neutrons can pass right through metal, but totally destroy living tissue. They are absorbed heavily by water, which human bodies are mostly made of.

Neutrons readily pass through most material, and hence the absorbed dose (measured in Grays) from a given amount of radiation is low, but interact enough to cause biological damage.

...

Consequently, in living tissue, neutrons have a relatively high relative biological effectiveness, and are roughly ten times more effective at causing biological damage compared to gamma or beta radiation of equivalent energy exposure.

In the Empire of Man series by John Ringo there is one weapon specifically designed to kill people in powered armour:

Powered Armor - ChromSten made armor that offers even better ballistic protection and camouflage capabilities that chameleon suits and are susceptible to damage only from heavy energy weapons such as plasma rifles and cannons or the last-ditch, contact-range weapon called a "one-shot", which delivers a shock wave through the armor to the plasteel matrix supporting it, causing a scab to break free and ricochette inside the armor, killing the person inside.

However, it will not work on starships. There are few things to consider:

1. Main problem for a starship is spontaneous explosion - that is, since inside it there is an atmosphere and outside there is not, then atmospheric pressure constantly threatens to break out. So there is from the start the need for significant hull structural integrity. This will render any weapons like one-shot almost useless.
2. Warships are expected to be damaged, that is why they're armored. Of course this causes significant increase in mass (depending on your FTL method it may be a factor), but increases surivability. Space warships would be armored with multiple layers, to boot.
3. In addition, while interplanetary space is mostly vacuum, even 99.99999% of non-vacuum is a serious problem with high enough speed. Also. it is filled with all kinds of radiation, most of it lethal. So right off the bat you have hit a snag if you want to use, for example, neutron-based weapons (ray weapons, as bombs are of limited use: you have to be pinpoint precise and best in contact with starship hull for it to have good effect; which is very, very hard to do). This difficulty stems from the fact that you want to shield crew from that interplanetary radiation soup...
4. What's more: different materials work well for different types of attack: kinetic projectile will punch through - for example - ceramic composite designed to stop coherent radiation beam, as well as through EM shield, but will be stopped dead by composite layered matrix like good-old Chobham armor (US and UK MBTs), if not big/fast enough.

Too many variables depend on tech you want to be available in your world you're building. However, the one thing that comes to mind that will have highest probability of success is still the same: boarding.

• Good points about the hull already having to be pretty rugged, but "Warships are expected to be damaged, that is why they're armored" is setting dependant. When you consider the limits of physical materials in conjunction with the Kzinti Lesson: "a reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive.", many questions on here have come to the conclusion that space-aged combat will probably be one-shot one-kill making either light weight evasive ships or some manner of non-material shielding far more realistic. Jul 29 '20 at 13:47
• @Nosajimiki - 1/2 - That's why I love Master of Orion II... this rule is well implemented there ;-) But still other rules apply: small ship - small weapons - fast and hard to hit. But internal space in small ship is... well... small. "some manner of non-material shielding" has it's own dimensions... making the ship a bit bigger, thus slightly slower... I believe people underestimate the concept of trade-off when formulating theories based on unverifiable assumptions. Not criticizing, just pointing out the obvious. That is why I put the caveat at the end of my answer. Jul 29 '20 at 15:09
• @Nosajimiki 2/2 - Another example: we can now build a shield that will protect against plasma (rudimentary, of course, and inefficient). But that shield will not protect against laser nor a bullet. Laser can be diffused by thick enough gas, but dust works much better. But that works in atmosphere, while there's no diffusion in space. But now range comes into effect so after say 1k kilometres laser ray is not focused enough to do significant damage. Ages old saying about competition between shield (defense) and sword (offense) will always apply. Jul 29 '20 at 15:15

Nanomachines

It is an answer too easily given. These machines however aren't the replicate forever kind. They are made to maximise the energy they have into the armour.

Where normally you would hope a bullet would use all it's kinetic energy to pierce the armour, it can be stopped, deflected by said armour as well. Even if the bullet is piercing the whole body, you lose energy, as evidently the bullet is still flying after it exited the bullet. Now imagine that you have slower moving pellets. The pellets hold nanomachines with huge amounts of stored energy. The machines start digging on contact, expending the energy as efficiently as possible into a target.

Starship hulls and armour are likely to have different properties, even if it's made from the same metal. One is created in such a way it can support the stress of moving through space and possibly atmospheres. The other to withstand a direct or indirect attack. The machines can be intelligent, only activating if the armour kind of material structure (or flesh) is found.

• It is actually very unlikely you'd use the same materials in body armor as a ship's hull. The material properties you want for stopping a bullet and what you want to protecting you from the hazards of space are very different; so, each will be optimised to its main function. Jul 28 '20 at 13:49
• @Nosajimiki exactly my point. So easy to recognise. Jul 28 '20 at 16:13

Energy weapons such as those featured in Star Wars suit this criteria very well, more blaster fire hits the walls and inanimate objects than any characters and very rarely decompressive events occured.

• Energy based weapons as a trope allows us to stretch physics in an acceptable way for the audience, it doesn't have to make a great deal of sense in reality because its tech that is operating in a way that is too high tech for the audience to comprehend, we just accept that it is.
• Energy force could be dialed up on down on the weapon, in pressure sealed environments the wielder could adjust their weapon for personal safety reasons.
• Energy Shielding could be used on hulls or objects making them impervious to or able to dissipate smaller levels of energy blasts. Yes it would be possible for a person to obtain energy shielded armor, but they should need a significant power source to maintain this constantly or for long.

As a general premise, the hull of the ship will be significantly thicker/denser than personal body armor, so even if both were made out of the same materials the body armor should be significantly more vulnerable, meaning that small arms weapons could easily be designed to deal enough force/impact to overcome some body armor without negatively affecting the hull.

Even in Star Wars, with the use of energy weapons, the same weaponry was used to engage other vessels, it was just on a larger scale. So it doesn't matter that the same tech could theoretically affect the hull of the ship, just that at the scale required to package it into a small arm we can deal enough damage to get through some common armors but not rupturing the hull.

Designing and wearing armor is always a trade off between availability/cost/weight/agility. So we don't have to consider that no armor could be made that is impervious to your weapon, only that it would take a lot of money and access to rare resources to do so. Bilbo's Mithril chain armor in LOTR is a good example (even if magic plays a part there) where it absorbed or reflected extreme force while leaving the wearer generally intact. Just as there is always going to be better an more improved armor, so to it can be possible to create a greater weapon.

You should also consider that most personal body armors are a collection of panels or layers that are held together so as to allow movement, where as the hull of a ship is generally a solid material. you can exploit this in a number of ways, there will be weak points, the armor could be commonly worn inadequately or the force of the impact only needs to be enough to overcome the force holding the armor in place...

If your energy weapon is able to excite the panels in the body armor, causing them to move apart or vibrate violently without deteriorating this could internally pulverize the wearer...

If you don't need a hard-SF, plausible-in-detail method, just appeal to some unspecified ultrasonic vibration that affects nerves to, e.g., paralyze muscles or induce sleep/coma. Like, e.g., telepathy, it's a common enough SF trope, even if there's no real-world explanation for how this could actually occur.

A more unconventional method is using a superfluid: https://en.m.wikipedia.org/wiki/Superfluidity#:~:text=Superfluidity%20is%20the%20characteristic%20property,that%20continue%20to%20rotate%20indefinitely.

You fire weapons with high-temperature superfluids at your enemy. Once it hits the target it will seep into the fabric of the ship, there's only theoretical materials that might be able to stop this but any opening at all will allow the fluid to get inside, even an airtight bulkhead wont stop this. Large enough quantities would probably start clinging to occupants and suffocate them, seep through the suits they wear and into their body where they'll poison the occupant, and that is assuming the liquid doesnt seep into any airlock and cause it to malfunction and open.

You basically want radiation weapons, specifically many kinds of radiation weapons in conjunction.

X-rays and gamma rays are shielded against by having lots of heavy elements in the path of your rays.

Neutron radiation is shielded against by having lots of light elements in the path of the radiation.

Highly charged particles (like electron beam) causes emission of x-ray bremsstrahlung ("braking radiaion") when it passes through matter of any kind, ie. the hull of the ship itself becomes the radiation source even if it stops the particle beam.

You may notice that these are highly conflicting requirements, so to defend against all three kinds at the same is extremely expensive, and probably mass prohibitive, because what works well against one, works much less well against the other. So basically you have to double your shielding, and then take into account that your shielding itself becomes a radiation source (neutron activation and bremsstrahlung) which you have to shield against even further.

How you generate this radiation is up to you. They could be beam weapons (x-ray, gamma, particle beams), plasma weapons (charged particles), or even nukes detonated near the hull (neutron and gamma and some charged particles).

Plain nukes themselves don't have much of a blastwave when detonated in empty space, so the main effect would be the radiation effects without some other secondary augmentation of the warhead. So you get that by default with nukes without massive structural damage. But you can augment nukes (such as adding a heavy matter jacket around the nuke that becomes plasma that is blasts into the hull) to also get massive structural damage when you need them to have such effects.

If you don't need to kill the enemy, but just making them unable to fight I would suggest a relatively low power laser. It works by blinding the enemy, making them unable to see and fight. Better than that, another enemy need to take care of the blinded enemy, basically disabling 2 enemies at once.

Exactly how the laser will hit the eye could be done in multiple ways. It could have a targeting system that automatically aim at the eyes, it could have an unstable system making it change direction to hit a bigger target area. Or the use of it may be to move it manually to hit a larger area.

This will not damage neither space suits or space ships. And it won't effect the people handling the space ship, since all they can see is based on cameras. It may be dangerous for people looking out through windows, but all spaceships have detectors in the windows that makes all windows on the ship black if hit by a very bright light. Before that system kicks in a person might be hit, but it will save the ship and majority of the people. Unfortunately this system is to big and heavy for space suits. Even if it wasn't it would make it impossible to see while using the suits, making the people getting into a serious disadvantage.

Lightning

That's it just use lightning. Ship hulls are usually metal which distribute electrons (as present day planes do), but even a small current across the body can cause defibrillation of the heart. You could explain that to allow people to move quickly they use kevlar / ceramic / non-conductive armor.

Regarding your particle ask. It turns out different wavelengths of light are absorbed or reflected differently. Light is transparent through glass, but it absorbs infrared wavelengths. You could establish a new wavelength which is reflected by the metal on your ship, but is far too heavy to wear (think wearing uranium / lead blocking X-Rays works, but is not practical). You could have some "tank" troopers which do wear such metal, but they are easily killed by lightning grenades which is why armies no longer use them.

Iron Extraction a harvesting tool that works as a weapon.

In Triplanetary by E. E. Doc Smith, there's a highly developed aquatic race called the Nevians. They have managed to harness the atomic power of iron and have an enormous desire for the metal to generate energy, but their planet has virtually no iron reserves.

So they scrounge up enough Iron for a single space expedition ( 9 kilograms total from memory, more riches than the entire planet yearly output ) and launch toward Earth because it had indications of Iron in spectroscopy. Captain is told "return with iron, or don't return"

On arrival they find iron in abundance, and deploy their iron-extraction systems to pull every atom. Any spaceship caught is de-ironed but since the hulls are made from (something exotic without iron) the only indication of the cause is anaemic dead bodies because their haemoglobin had been stripped of all its iron. Later the Nevians attack Pittsburgh, because, why not?

Upshot - a vessel made from composite materials, with copper/aluminium wiring and silicon computers, ceramic rocket nozzles, and titanium frame would have minimal iron in it.

Could you imagine space ships completely devoid of iron, steel, or stainless steel, in your world ? If other elements suit your plot, perhaps Calcium, or something more biological like Vitamin-C.

An Age Old Problem: I Want to Kill the People in That Spacecraft, But Only a Little Bit

My preliminary (a month late?) analysis indicates that smart projectiles may be what you're looking for.

I'll start off by grounding us in an existing example: the Oerlikon Skyshield measures the muzzle velocity of its projectiles as they exit the barrel and programs them to detonate immediately prior to an intercept point relative to their target. This is done for the purposes of maximizing hit probability with sub-projectiles, a secondary consideration in this case.

For your purposes the same technology could be combined with a range finder in the targeting optics/visor of your hypothetical space commandos, and the weapon could program (near-field or physical contact, so no hacking) each projectile with an acceptable "detonation envelope" based on the distance to the target; projectiles would be fitted with an electronic impact fuze that runs the following (haphazardly pseudo) code:

time_start_det_check = 5
time_end_det_check = 10        //NOTE: don't shoot anything until we implement these

flight_time.update             //update flight time from the internal ticker

//timer goes live, let's get some
while (flight_time > time_start_det_check and flight_time < time_end_det_check){

if (impact = true){       //check for space pirates
fuze = boom           //send 'em down the river
}

flight_time.update        //update from ticker while we're in the loop
}

if (flight_time > time_end_det_check){    //check for end of envelope
fuze = never                          //we missed :(, render inert so you don't kill us all
}


Calculation distance could be as straightforward as using cameras internal to the visor to detect eye position and triangulate distance to the target; jamming such a system would entail rendering the shooter sightless/unable to focus on their target, in which case they're not going to be doing much shooting anyway.

You'll want the projectile to be relatively low velocity to avoid any kinetic damage from misses. Your warhead can be a shaped charge (pencil-thin jet of molten copper) or HESH (explosive modeling clay). If I were you I'd go with the shaped charge; though a lump of plastique going off next to your chest would really ring your bell, armor or not, it would also tear a much larger hole in a spacecraft hull should an accident/edge case occur. A nice small shaped-charge shaped hole can be patched easily/will leak less atmosphere in the meantime.

I'll assume weight is at a premium/gas propelled is a no-go. That leaves electrical (coilgun plays nice with low velocities) or chemical. The undeniable allure of rocket-propelled projectiles notwithstanding, acceleration of the projectile during flight would throw a spanner into our flight time/distance calculations, so rocket-propelled is out. Standard firearms will generate/retain quite a bit of heat in vacuum (among other issues), but since this weapon is designed explicitly for atmospheric environments we can dodge that concern.*

*The dual use cases open potentially interesting possibilities for switching between ammo that's rocket-propelled (when you need to gunfight outside the spaceship in the morning) and hull-safe (when you need to move the party inside for the afternoon).

1. You don't need exotic technology, and there are no shortcuts for your enemy to protect themselves from bullets filled with explosives (reactive armor works, once--keep shooting).
2. It's effective at point blank range (self-propelled projectiles are not), so you won't be up a creek in narrow passageways.
3. You don't need to alter reality so fighting is unnecessary.
4. To finish by grounding us in another example, the weapon you're looking for (minus the on-the-fly range calculations) more or less already exists. It's called the XM-25, and it gets brownie points for already looking like it belongs on a spacecraft:

Inertia

We are talking about a spaceship (a tin can) full of enemy in armor (smaller tin cans), and presumably the "space" in spaceship implies that it has the ability to travel at extremely high speeds. If that is true then your enemy has already provided you with a method of annihilating them which will simultaneously leave the ship whole and mostly functional.

All you have to do is wait for a moment when the ship is going really, really fast... then stop it. The result will be that all of the smaller tin cans will rush ballistic-ly towards the front of the ship (which having been designed to impact micro-meteorites at high speed, is tough enough to take the resulting collisions). Inside each of those smaller tin cans, each enemy will experience potentially fatal g-forces during the moving part of their ballistic journey, followed by jellifying impact with the inside of their armor upon impact.

The best part of this method of mass homicide is that each of the jellified corpses comes wrapped in an easy to clean up tin can. So you are saved the gross job of getting all the enemy goo out of the nosecone.

So your handheld weapon simple needs to create a short-lived microscopic black hole directly behind the advancing ship. The hole's mass and resulting gravity should be carefully calculated based on ship mass and momentum so that the ship stops. Too little hole mass and the now-unmanned ship will continue on its current vector forever. Too much hole mass and the ship will slide backwards into the hole and be spaghettified. The hole's decay rate also has to be carefully calculated because if it lasts too long, again it will eat the stopped ship.

So, as tasty as a serving of jellified-enemy with a side of spaghettified spaceship sounds, the poster requested an undamaged hull. You will need to get the black hole mass calculation and decay rate perfect. As with all military maneuvers which involve black holes... Be careful!