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In the new Thrawn books by Timothy Zhan, he describes a weapon called a 'breacher missile'. In simple terms it is a missile that sprays a corrosive chemical onto an enemy ship or structure, damaging external equipment like sensors and weapons and creating weak areas for laser weapons to target. The advantage (as described) over more traditional explosive based weapons is that they are hard to defend against. Even if the opponent manages to destroy the missile, the corrosive liquid inside is going to continue in whatever direction it was traveling.

While Star Wars is pretty loose with science, it got me thinking. Could a weapon like this actually work in a more realistic setting? Are there any known chemicals that are sufficiently corrosive to rapidly damage or destroy a target? How would you make those chemicals remain effective in the low temperature, low pressure, high radiation environment of outer space?

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  • $\begingroup$ Where does the oxygen for the acid reaction come from? $\endgroup$ Jan 17 at 19:43
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    $\begingroup$ Fair question, but not impossible to deal with. There are plenty of chemical reactions that produce oxygen. Look at anything used as a rocket fuel. $\endgroup$
    – pbuchheit
    Jan 17 at 19:52
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    $\begingroup$ The oxidant would have to be packed with the corrosive substance. How do you keep them apart until contact? $\endgroup$ Jan 17 at 19:57
  • $\begingroup$ @JustinThymetheSecond Piranha solution could be mixed shortly before launching a missile, mixed in flight by an automatic system, or just dump both tanks onto the target. Oxoacids such as H2SO5 are single compounds that are both oxidising and corrosive. Some targets would be affected more than othersof course $\endgroup$
    – Chris H
    Jan 18 at 11:54
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    $\begingroup$ If you just want to disable sensors, you don't need any corrosive effect, just something that coats the sensors with a material that prevents them from getting a good signal - e.g.: black paint, or dare I say, raspberry jam. Sure they could just clean it off, but that requires a risky and time-consuming space-walk, during which time they'll be sitting ducks. $\endgroup$ Jan 18 at 18:41

14 Answers 14

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Are there any known chemicals that... rapidly damage or destroy a target?

In space? Yep! You can rapidly damage or destroy a target by the simple act of accelerating any chemical to high enough velocities and crashing it into an opponent. Start at a few kilometres per second relative to the target, and go up from there as necessary.

...are sufficiently corrosive to...

Oh. Corrosion is generally slow, and even if it were a particularly rapid process, it is limited by the amount of corrosive material which gets used up in the process). A kinetic weapon is instead limited by both the amount of material and the velocity it is travelling when it hits you.

I also rather suspect that you get a lot more literal bang-for-your-buck by using chemistry to generate kinetic energy (eg. fragmentation warheads) than you do by trying to nibble away your opponent, but I don't think I can easily prove that.

If nothing else, it is always potentially possible to fire a bullet a bit faster, but you'll have a hard job making your super-acid correspondingly more corrosive because there's only so much energy you can pack into merely chemical bonds.

The advantage (as described) over more traditional explosive based weapons is that they are hard to defend against.

Its a setting where normal rules of physics don't apply, so its hard to translate its stuff into the real world. If you wanted it to work in your setting, then you can wave your hands as you see fit.

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  • $\begingroup$ The only reason I CAN see is if anti-projectile systems are sufficiently advanced and there is some relatively unshielded equipment on the outside of ships. Here a warhead that if destroyed remains a lightly damaging cloud could still work well enough, to disable e.g. a sensor suite that needs to be unarmored or so $\endgroup$
    – Hobbamok
    Jan 18 at 8:24
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    $\begingroup$ @Hobbamok even then it doesn't compare favorably with a cloud of hypervelocity dust (see L.Dutch's answer, for example). $\endgroup$ Jan 18 at 9:31
  • $\begingroup$ One important issue with corrosion is that it is slow. Maybe your hits will destroy the enemy ship, but that is a small consolation if that enemy ship remains operative long enough to destroy your own ship. $\endgroup$
    – SJuan76
    Jan 18 at 15:13
  • $\begingroup$ Just to clarify, the primary purpose of these weapons is to disable rather than destroy. They are a tactical option to disable a ship you want to capture or to soften up a dangerous opponent whose armor/weapons make them superior in a direct confrontation. $\endgroup$
    – pbuchheit
    Jan 18 at 15:44
  • $\begingroup$ @pbuchheit your clarification has come a little late, but they're just not very good at doing the former, and even if the latter made any sense (which it doesn't), if you can hit your opponent with weapons then you should use ones which work well, rather than ones which don't. $\endgroup$ Jan 18 at 16:50
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I'll suggest using FOOF and then back away very quickly. That stuff is so dangerous I don't even like to read about it for fear of getting burned.

FOOF is horribly unstable but can be weaponised by using relatively stable precursors and mixing them on contact or on a proximity fuse to dust an oncoming space craft with particles before they spontaneously decompose. In the case of the breacher either it detonates a cloud of FOOF in close proximity and the ship gets randomly hit by active molecules as it flies through or the breacher latches on and sprays concentrated FOOF onto a given area of the hull.

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  • $\begingroup$ Or ClF3 which is slightly more storable (Wikipedia has an instructive quote from someone who's worked with the stuff) $\endgroup$
    – Chris H
    Jan 18 at 11:56
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    $\begingroup$ Mentioning FOOF and not using the Things I Won't Work With link? Heresy! $\endgroup$
    – Separatrix
    Jan 18 at 12:13
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    $\begingroup$ @Separatrix: science.org/content/blog-post/… $\endgroup$ Jan 18 at 13:52
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    $\begingroup$ It also works great at REALLY low temperatures. $\endgroup$ Jan 18 at 23:46
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    $\begingroup$ @Separatrix Heresy of heresies I didn't even know that existed until right now, I will be sure to include it if I ever decide a question needs such an extreme answer in future. $\endgroup$
    – Ash
    Jan 19 at 3:28
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More than corrosion you can try with ablation: basically you can try to sandblast the surface of the target spaceship with a constant flow of abrasive particles at high velocity.

If you send it against the ship velocity you can use the addition velocity principle at your advantage.

Additionally, if you can reach relativistic velocities, the particles will produce gamma rays, which are pretty effective at eating matters away.

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What is the spaceship made out of?

If your space ship is a flying steel battleship, the prospect of corrosives eating the hull is slim. But you could definitely have carbon fiber spaceships, or plastic space ships, or styrofoam space ships or ice hull spaceships that would be very much affected by corrosives. Your corrosive of choice would depend on the material you were attacking. Solvents could work for plastic. Oxidizers for carbon fiber (hydrofluoric acid! there is your corrosive). Maybe sodium metal powder in hexane for ice hull. Hot mercury vs an aluminum hull - that would be a fun scene to write as the fingers of amalgam start sticking into the interior of the ship.

A universal "corrosive" would be antimatter. You could "spray" charged antiprotons in a beam, confine them in a missile or what have you. The energy released by the matter-antimatter reaction depends on the relative velocity of the reacting particles so you could dial it up or down depending on your needs, which is cool for a fiction. This might be a more effective weaponization of antimatter in space - if you blow it up like a bomb antimatter offers no advantage over a fission bomb. But using antimatter to react away a piece of the hull is less destructive and offers the possibility of capturing the ship and crew intact.

OK, relatively intact.

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  • $\begingroup$ The idea of spraying a ship with antimatter is intriguing. Each antimatter particle would annihilate a particle of the ship. Enough particles and they would eat through the hull. $\endgroup$ Jan 17 at 19:49
  • $\begingroup$ @JustinThymetheSecond - and also the particles would flash when they hit and probably leave a small, spreading puff of vaporized hull material. $\endgroup$
    – Willk
    Jan 17 at 20:39
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    $\begingroup$ And if you could give these particles an electrostatic/magnetic charge, such that they were attracted to the hull ... $\endgroup$ Jan 17 at 21:13
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Here are a few candidate compounds we have available today (rounding up a few of my comments.

One of the most obvious is Chlorine Trifluoride (ClF3)](https://en.wikipedia.org/wiki/Chlorine_trifluoride). It has niche uses in semiconductor manufacturing and was proposed as a rocket oxidiser. One of the researchers working with it, John D. Clark describes ClF3 as follows:

It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water—with which it reacts explosively. It can be kept in some of the ordinary structural metals... because of the formation of a thin film of insoluble metal fluoride that protects the bulk of the metal... If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes. [emphasis mine]

in his book Ignition! An Informal History of Liquid Rocket Propellants (which is worth a read)*

So ClF3, in contact with almost any material, will start a fire; it's the oxidiser so there's no need for air. Even glass spontaneously combusts in contact with it. The exceptions are metal fluorides, which make it possible to contain by using them as tank liners. It has a boiling point below room temperature and a fairly high vapour pressure, so would be expected to be gaseous by the time it made contact. This is ideal if you want it to degrade the hull rather than anything more dramatic (though in sufficient quantities dramatic is possible, as described here and especially in the link about a spillage. Note that a major reaction product in many cases is HF, which is nasty enough by itself (corrosive and poisonous).

As I commented, we also have Oxyacids such as Chloric acid (HClO3) and Peroxymonosulfuric acid (H2SO5) which would be useful against organic materials such as composite hulls as well as some metals. Even Piranha solution (sulphuric acid and hydrogen peroxide, mixed just before use) would attack composites.

I suggest though that with laser weapons commonplace, mirrored hulls would be used to provide some limited last-ditch protection. Rather than metal these could be dielectric mirrors (usually oxide material) so ClF3 would be ideal. Burning off the mirror coating would be just what was needed to make the hull more vulnerable.


* John D Clarke was also a published SF author and Isaac Asimov's boss for a while; Asimov wrote the foreword to Ignition!

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    $\begingroup$ Interestingly enough, that usage of improving the effectiveness of laser weapons shows up in the books that got this idea started. While they never explicitly mention mirror coatings, there are frequent descriptions of using the corrosion to create dark patches to increase energy absorbtion. I mentioned it in my original post, but my wording was too vague to make clear what was going on. $\endgroup$
    – pbuchheit
    Jan 19 at 13:25
  • $\begingroup$ @pbuchheit I guessed. I work with high-power lasers and know the effect of a scratch or speck of dust on a mirror $\endgroup$
    – Chris H
    Jan 19 at 13:39
  • $\begingroup$ I can't get past the bit where it's hypergolic in contact with asbestos and sand, silica is so aggressively chemically inert in almost every context. "the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes." is just brilliant and, especially when you apply it a space ship or station context, terrifying. $\endgroup$
    – Ash
    Jan 20 at 1:01
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    $\begingroup$ @Ash Clark's book is a bit heavy on the chemistry but full of stuff like that. PDFs are available online $\endgroup$
    – Chris H
    Jan 20 at 9:10
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Chaff

When you start talking about civilizations with propulsion capable of interstellar flight, you are also talking about people with incredibly powerful weapons thanks to the Kzinti Lesson principle. So, it is unreasonable to think that any ship would survive and attack from any weapon based on the chemical bonds of solid matter alone.

Instead you are not attacking the ships armor, but its active defense systems which constitute 99.999% of the ship's ability to survive a weapon hit. So, a damage-over-time weapon would not be something designed to corrode the hull, but something that can trick the ship into wasting power/ammunition defending against feigned attacks.

This is where chaff comes in. Chaff are cheap little pieces of radar reflective tape designed to fool sensors. So you fire a missile at the enemy and before it gets into range of the active defenses it starts scattering a large cloud of chaff. As the chaff tumbles its cross section is constantly changing making it very hard to tell where any one strip is or even what they are; so, the defending ship has to activate its shields to cover a large time period and area of uncertainty until it is sure that there are no more possible inbound impactors, or that it is clear of the chaff field. You can mix a few small impactors into the cloud of chaff just to make sure they can not afford to ignore it. This will in effect cause the shield's capacitors to drain over time limiting its ability to resist a full strength attack from your High Energy Laser weapons.

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Fluids are not usable in space

The Zhan method won't work. Any fluid, like most acids, will immediately evaporate when it is released from your ship. You'd have to pack the fluid in a projectile and penetrate the hull, to create havoc inside.

Atomic oxygen is to be considered.. it is rare in space, but highly corrosive

The absence of molecular oxygen will rule out a lot of corrosive agents. However, spacecraft are vulnerable for atomic oxygen in space. Normally there isn't much of it, but when present, it will even corrode polymers and carbon fiber. If you devise a weapon based on atomic oxygen, investigate what protective coatings are used by the enemy. A gold or platinum coating will protect a ship against it.

https://en.wikipedia.org/wiki/Corrosion_in_space

To prepare a laser target, you could also use black adhesive particles

One of the purposes of using corrosive weapons is weakening the target for a laser attack. In space, a corrosive weapon is far more difficult. If you'd like to prepare for a laser attack, consider projectiles containing carbon powder (graphite) with some adhesive. It will provide you with a black, non-reflecting laser target.

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    $\begingroup$ "will immediately evaporate when it is released from your ship". Lovely theory, false facts. Evaporation rate is dependent on the vapor pressure of the liquid. For some materials the rate of evaporation is so slow that they do not even "fall apart" from the boiling action. Example: If you chuck a liquid blob NaK (sodium-potassium) metal coolant from a soviet BUK reactor into space, it will not only not immediately evaporate, but will still be a debris hazard 45 years later!!! conference.sdo.esoc.esa.int/proceedings/sdc7/paper/367/… $\endgroup$
    – PcMan
    Jan 17 at 18:39
  • $\begingroup$ @PcMan interesting information... I always assumed fluids would cook at 1K in a void and evaporate. But before I'm going to change my answer text, could you please find out if it works for usual fluids, like corrosive substances ? How special is this NaK coolant's vapor pressure ? Is it corrosive ? Meanwhile googling around I found this one astronomy.stackexchange.com/questions/28531/… there's mension of superionic water, but I don't know how corrosive that is. $\endgroup$
    – Goodies
    Jan 17 at 18:55
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    $\begingroup$ There's a whole load of spacecraft research around liquid droplet radiators, for example. $\endgroup$ Jan 17 at 19:10
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What you want is a space equivalent of Greek Fire.

As others have stated, it can't be a liquid, but an adhesive gel that is sprayed or projected by a missile or sticks on contact may work.

As for oxygen that may be required, that others have mentioned, the gel can contain cells/beads of oxygen whose walls dissolve in the gel. So the gel would be effect for a given time period. The oxygen beads can be inserted into the gel at the last moment possible if required.

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Kinetic Energy

Along with all the other problems you have the issue of kinetic energy. Unless the two objects are traveling on more or less parallel courses at similar velocities the relative differences in velocity are going to be quite large.

For example two space craft in orbit above the Earth in the same or very similar orbits will have similar orbital velocities. In fact their relative velocities are so similar that with minor adjustments the two craft can reach zero relative velocities and perform a docking mission. (As you know this is more or less a routine operation today).

The problem in virtually any other situation but the one I just mentioned however the relative velocities of two objects traveling through space (compared to each other) will be almost always be so high that even minor impacts can be devastating e.g. witness the way the ISS has procedures for adjusting its orbit to avoid pieces of orbiting debris that are thousands of times less massive that it is.

So in any type of 'normal' space battle the combatants are going to have huge relative velocities as will anything they fire at one another. This makes anything they do fire incredibly dangerous. In the case of your chemical missile its the missile itself that's the threat not the payload. If you fire say a 200 kilo missile with a 10 kilo load of corrosive chemical and it hits the target at say 20 kps the amount of energy released by the impact will be orders of magnitudes more damaging than any chemical corrosion & also, unlike the corrosion effectively instantaneous.

And if the enemy intercepts the missile the fragments are potentially more of a problem than the original missile (think being hit point blank by shotgun pellets vs a rifle bullet - not really a lot to choose between them in terms of fates is there?

Finally all this is before you even consider how a chemical weapon would operate in a zero atmosphere, zero g environment. Under normal circumstances its entirely likely the vast majority of the payload would disburse into space without striking the target.

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Maybe enough to scratch the paint

Even if the corrosive material worked in a vacuum in any way it would spread out as soon as it is not contained. The forward momentum would not be enough to contain the expansion towards the vacuum. Eventually only a thin widespread cloud would attack the target, not even enough to damage the sensors. Probably for the sensors a sticky material would be more effective.

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If 'corrosive weapons' includes the possibility of delivery by nanites, there might be something to this concept.

Electrostatically charged nanites, that would stick to the hull. They would both release the corrosive fluid, AND chew away at the hull. A gazillion of them, all operating under a primitive collective hive mind AI, all concentrated on a particular spot on the hull, could do some serious damage. Think of iron fillings around a magnet.

If the corrosive substance inside these nanites is, perhaps, Chlorine Trifluoride as Chris H proposes, and these nanites deliver it to a specific spot before rupturing the containment vessel holding it, I can foresee one very big-badda-bang. That 'titanium' thing ("...but molybdenum, tungsten, and titanium form volatile fluorides and are consequently unsuitable.")is really interesting, since spaceship hulls could be envisioned to be made of titanium.

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Corrosion is a problem that NASA has been wrestling with since they started putting things in space. While they are not dealing with weaponized corrosion, they do have problems with off-gassing from things that are normally "just fine" in an atmosphere (some integrated circuits can rupture because they contain just enough gas to be a problem), to metals that will cause galvanic reactions. I was looking to work on a cube sat project and low earth orbit satellites also have to concern themselves with ionized oxygen.

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Nothing happens

Phase: Chemical reaction will happen only if corrosive material is in liquid or gaseous phase. In space, liquid will evaporate instantly.

Time: Corrosion occurs when corrosive material remains on the target material for a sufficient time. In space corrosive material will be only in gaseous form which will not remain on the surface of the target because the target is moving with a high speed.

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  • $\begingroup$ Unless it has an electrostatic charge. $\endgroup$ Jan 18 at 23:57
  • $\begingroup$ "sufficient" time can vary greatly from one corrosive substance to another. There are some where that time is so short it couldn't be measured experimentally. $\endgroup$
    – Harthag
    Jan 19 at 16:03
  • $\begingroup$ True, but this very short time is under certain conditions. At 0 pressure and 0 temperature, it may not be that fast. $\endgroup$
    – imtaar
    Jan 20 at 12:52
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It would not work as proposed, because space is cold.

Corrosive reactions are chemical processes, and the speed of such reactions is heavily dependent on temperature. See the Arrhenius law for example, which decribes many chemical processes accurately, and contains an exponential influence of temperature on the reaction speed.

The outside of a spaceship would presumably be pretty much space cold. Therefore, chemical reactions on the outside would be reaaaaally slow. Also note that all known corrosives are not as fast as usually depicted in fiction (but this can be handwaved with unobtainium). You can look up some videos of various substances dipped into different acids to get a feel for that.

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  • $\begingroup$ The vacuum of space is actually a very good insulator. Which is why a problem for spacecraft is usually not freezing but overheating. The international space station, for example, got a pretty sophisticated cooling system. You might have heard that water freezes rather quickly in the vacuum of space, but that's not because of temperature exchange but because of low pressure. $\endgroup$
    – Philipp
    Jan 18 at 10:54
  • $\begingroup$ @Philipp It is not so much that a vacuum is a good insulator, it is that conduction heat transfer is pretty much eliminated. But it begs the question be asked. "what part, specifically, does 'heat' play in chemical reactions?" Heat is just a measure of the rate of vibration of the molecules. Saying that the vacuum of space is a good insulator says nothing about the rate of a chemical reaction in a vacuum. $\endgroup$ Jan 18 at 23:56
  • $\begingroup$ @JustinThymetheSecond You don't want the chemical reaction to occur in the vacuum. You want it to occur when the munition hits the target. $\endgroup$
    – Philipp
    Jan 19 at 8:56
  • $\begingroup$ @Philipp So you want the chemical reaction to occur INSIDE the ship? $\endgroup$ Jan 19 at 13:49
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    $\begingroup$ @Philipp This is some really, really 'cool' reading about space temperature chemical reactions. Quantum tunneling at these 'temperatures', which are almost perfect for quantum-type stuff. . scitechdaily.com/… $\endgroup$ Jan 19 at 14:18

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