Suppose that, sometime in the future, terrorists and conspicuously-evil nations and politicians are tired of using regular old nuclear bombs to destroy their rivals' cities - cities on the ground are well-protected by orbital railguns that can almost-instantly destroy missiles before their payload detonates, asteroid and moon cities in space all have kilometers - if not hundreds or thousands of kilometers - of ground under which to bury a super-secure bunker, and space stations are well-defended anyways. Besides, what with everyone (or at least many people) living in space in the future, radiation meds are a common sight, and simply spraying neutron radiation at one's rival isn't enough to finish the job.

So, the next best thing is an antimatter bomb: converting a kilogram of matter and a kilogram of antimatter into 40 megatons-of-TNT of flesh-searing, metal-melting, electronics-frying, DNA-unraveling gamma radiation.

Specifics aside, let's say that the Unspecified Terrorist Organization (UTO) wants an antimatter bomb to blow up an asteroid-based teddy bear factory in order to prove a point about evil butterfly colonies on Mars. They can acquire high-grade missiles, detonators, avionics controls, and antennae for the suicidal AI who will drive the missile to its destination, but there's one thing they don't have, and that's the payload: antimatter.

The problem

The issue with antimatter is that it's notoriously hard to produce and even harder to contain. Particle accelerators can produce and decelerate it to useful energies, but particle accelerators are very large and only produce a small amount of antimatter per unit energy used to drive them. Positrons (which are produced by cosmic rays interacting with the atmosphere) have been investigated, but they're too high-energy to efficiently contain without an equally-massive apparatus to decelerate them into a Penning trap. Positrons are also produced naturally in beta-+ decay, but another massive system of constantly-replaced radioisotopes would be able to produce a meaningful amount, and acquiring such radioisotopes would be difficult to say the least.

Large apparatuses would work, but they would be easily detected and shut down. The UTO needs the antimatter, but the teddy bear factory needs desperately for the UTO not to have antimatter, and huge orbital particle accelerators constantly spewing antiprotons into Penning traps which are shipped off to undisclosed locations is not exactly discreet.

Actual question

So, here's the question: What's the most efficient way to obtain 1 kilogram of antimatter without getting caught by the authorities?


  • The interplanetary police are aware of any object city block-sized or larger, so huge LHC-like accelerators orbiting some obscure moon of Jupiter are not allowed if their only purpose is to produce antimatter. Objects or structures smaller than that can be hidden indefinitely from the police.
  • Antimatter can be efficiently transported between bodies in the Solar System (assume 3-5 business day situation as far as timing goes), so antimatter produced anywhere in the system counts towards the total.
  • Radioisotopes (like potassium that emits positrons) are monitored and can't be used unless there's some extremely convincing story to tell the authorities what the UTO is doing with 3,000 tons of plutonium.
  • Timeframe doesn't matter; so long as one kilogram of antimatter gets made, the mission is accomplished.
  • Anywhere in the Solar System is fair game for setting up an antimatter farm of whatever variety is most efficient and meets the secrecy requirements.
  • The UTO has as much money as it needs for anything.

TL;DR the goal is efficiency in a small package: I'm looking for the fastest way (in time, not necessarily money) to produce antimatter that fits these secrecy requirements.

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    $\begingroup$ Minor point - no asteroid base can possibly have "thousands of kilometres of ground". On the biggest asteroid in the solar system, you can only go 470km down before you're going back up again. Space is very big, but asteroids are not. $\endgroup$
    – jdunlop
    Feb 7 at 2:54
  • $\begingroup$ Good point - by asteroid I meant asteroid or small moon. Error on my part, thank you for that. $\endgroup$ Feb 7 at 3:14
  • $\begingroup$ intern: "sir, antiproton is still very hot!" scientist: "Then blow on it, what you expect" $\endgroup$
    – user6760
    Feb 7 at 4:19
  • $\begingroup$ The issue with accelerator-driven antiproton production is that when you get them they're traveling near the speed of light and can't be studied usefully; the experiments you see about anti hydrogen and whatnot involve decelerating the antiprotons from near c so that they can be made useful. Although, yes, it will sound silly to the interns carrying the antimatter around. $\endgroup$ Feb 7 at 13:26
  • $\begingroup$ Just as a note, I'd recommend that you'd remove the part about communism, since it's a bit political and shouldn't be included on this website. I'll do this for you, this is just a heads up. $\endgroup$
    – Daemons
    Feb 7 at 23:33

10 Answers 10


Almost Anything Else Would Be Easier

With the science-based tag in place, you're pretty much scuppered. Making antimatter is hard. When we're assembling anti-hydrogen, we make an anti-proton and attach a positron to it.

Having 3000 tonnes of plutonium doesn't make your job any easier, because of the inescapable laws of conservation of energy and entropy: energy in > energy out.

So if you want to create a kg of antimatter, with the potential to release 90 petajoules of energy, you need to contribute at least 90 petajoules of energy, and, anytime in our immediate future, many multiples of that. Assuming perfect efficiency, you'd need the entire electrical output of the entire Earth (circa 2021) for four years.

The reason nukes are useful is because the energetic component is already there. With antimatter, you're starting from scratch.

If you have a suicidal delivery drone for your antimatter warhead, why wouldn't this work for a conventional thermonuclear weapon? Presumably the orbital railguns are as effective - or ineffective - against a missile regardless of what it's got in its nosecone.

So, What Do We Do?

If we're going to go with soft sci-fi, let's borrow from one of the top contenders in the field: Star Trek!

In the Star Trek TNG Technical Manual, they mention "charge reversal devices", which, like the inertial dampers or Heisenberg Compensators, do not have their operation elaborated upon because they are valuable but entirely scientifically inexplicable devices.

These turn ordinary matter into antimatter at a 24% energy loss relative to the annihilation energy of the resultant antimatter. So your 90 petajoule bomb would only require 21.6 petajoules to make. Just one year of every power plant on Earth!

You'd inescapably require an absolutely enormous powerplant or power gathering facility, but you could potentially disguise your antimatter plant as an experimental solar power harvesting satellite or something similar. You'd definitely need ablative paperwork.

Boldly Go Elsewhere

The other option (ruled out by your text making it pretty clear that you're confined to the solar system) is finding the stuff. It's possible that there are antistars out there, with associated antimatter solar systems.

You can't get to them without faster-than-light travel (and if you have that, your energy problems are probably solved anyway), but maybe, maybe your terrorists get lucky and an antimatter-asteroid got flung out of another galaxy aeons ago and through the most fortunate circumstances ever happens to be passing very near to our solar system.

Such an item would be glowing very brightly as it annihilates interstellar dust and gas on impact, but we're already deep into contrivances, so perhaps it follows an eddy in interstellar material that minimizes its contact with matter so that your terrorists are the only ones lucky enough to recognize what it is. They head out past the Kuiper Belt and very, very carefully with lasers and magnets excise enough antimatter to blow up whatever they want.

  • 1
    $\begingroup$ " So your 90 petajoule bomb would only require 21.6 petajoules to make." - I read that 24% loss as a CFD of 76%, so a 90PJ bomb would ask for 90/0.76=118.42 PJ instead. Five years instead of one, five times less covert but still doable. $\endgroup$
    – Vesper
    Feb 7 at 7:09
  • 1
    $\begingroup$ I read that as it taking 21.6 pJ plus 1 kg of normal matter, but it's sci-fi, so do what you want. $\endgroup$ Feb 7 at 16:03
  • 1
    $\begingroup$ @RobertRapplean - that was my take on it too. That it was effectively priming normal matter for annihilation, so your energy cost was 24% of the annihilation energy of the "charge-reversed" matter. But it could also mean that you need to contribute 124% of the annihilation energy and it's worthwhile to Starfleet because of the energy density of the resultant antimatter. $\endgroup$
    – jdunlop
    Feb 7 at 18:45
  • $\begingroup$ @jdunlop The latter is the intended reading, yeah. Another part of the TNG TM says that Galaxy-class ships have charge reversal devices for emergency warp drive fueling only, because it requires more energy than you'd get back but the warp drive requires specifically M/AM reactions to function for Reasons. $\endgroup$
    – Idran
    Feb 7 at 20:35
  • 1
    $\begingroup$ @Idran - well, we also have dlithium, which somehow mediates M/AM reactions despite pretty clearly being made of matter itself. You don't really want to start tugging at Reasons. $\endgroup$
    – jdunlop
    Feb 7 at 21:19

Have scientists on the inside

The largest difficulty is to find a way to stockpile a kg of antimatter. This can be made easy by science! Antimatter can be an interesting part of research. Antimatter produced can be shipped to a single location, or one particle accelerator has been at it for a long time. This way there's no difficulties of costs or production. That is done by large governmental or company entities. All you now have to do is receive it from them.

Humans can be a weak link. There's many ways to exploit this. The scientist(s) themselves might be part of the UTO. Their understanding of the world has made them want to target this teddybear factory. They could also want to prove a point of the dangers, secretly helping this organisation for a large bad event to show that security needs improving or the research needs to stop. Finally it can be greed or the like. You can pay them a whole deal secretly for them to accidentally leave their security card somewhere or accidentally mess up the shipping address of a boatload of Antimatter (hyperbole).

Regardless of the reasoning, the scientists can have large stockpiles of the stuff. They can use it themselves or find clever ways for Antimatter to arrive at the UTO.

  • 4
    $\begingroup$ Yea, artificially induced accounting errors are much easier than building particle accelerators. $\endgroup$ Feb 7 at 16:06

A 100g banana has about 0.358g worth of Potassium in it.

From Wikipedia, 0.0117% of that Potassium is unstable. Round it up to 0.00004 grams of decaying Potassium per banana.

Also from the Wiki, in 1g of K, you get 31 atoms breaking up per second. But only about one in every 100,000 generate a positron, so you need 100 kg of K - that's about 280,000 bananas - to make a positron per second.

That rounds up to about 10-30 kg per second. So if you want to gather 1kg in one second, you need a little over:

$ 2.8 \times 10^5 \times 10^{30}$

= round it up to 300,000,000,000,000,000,000,000,000,000,000,000 bananas. I call that three metric [censored]loads.

But if you can wait, you need fewer bananas. Divide that number by 86,400 if you can wait a day, or by 31,536,000 if you can afford to wait a whole year. The latter would still be like 3 x 1027 bananas, or 3 x 1025 tons. For comparison, the Earth's own mass is about 6 x 1021 tons.

You might need to wait a few millennia to make that bomb viable.

  • 12
    $\begingroup$ This is so xkcd. Unfortunately, with only 10^8 tons of bananas produced each year and less than 10^10 years left before the sun's warranty runs out (just looking at orders of magnitude here), that means that the terrorists are shy of their target by a factor of 10^7 before the end times for this solar system. Upvoted for humour anyway, though @jdunlop has already got my serious upvote. $\endgroup$ Feb 7 at 5:52
  • 4
    $\begingroup$ An alleged dinosaur scientist, waiting for his "antimatter" to cook since before the meteor caused his species' extinction: "First time?" $\endgroup$ Feb 7 at 17:30
  • 3
    $\begingroup$ Thats public randallism, that is.. $\endgroup$
    – Pica
    Feb 8 at 8:26

(Comment, but too long) You are falling for an error that shows up in an awful lot of science fiction--that antimatter is somehow a superweapon.

An antimatter boom is slightly more destructive than a fusion boom of the same size because it comes from a smaller area and thus has a higher peak intensity. While this is important in chemically powered explosives (it's why nobody uses fuel-air explosives against hard targets despite their big boom to weight ratio) it's hard to picture a situation where the higher possible energy flux of an antimatter bomb could matter. (Now, if you have some deflector shield that can stop up to a given flux then you might have a reason for antimatter--but fusion charges can also be shaped. You didn't specify a deflector, though.)

The actual boom part of an antimatter bomb is smaller than an equivalent fusion bomb but boom is usually a small part of the total missile weight anyway. Why are you willing to put up with the horrendous problems of antimatter (can you say "sympathetic detonation"? An antimatter bomb inherently goes off if too damaged) to get a slightly lighter missile?

Now, if you can come up with some small containment system antimatter could be your weapon of choice for a smuggled bomb. I can't picture it ever being put on a missile, though. And you are specifying missile delivery, not smuggling.

And if this wasn't enough, there's no such thing as a perfect vacuum. Nor is there such a thing as a material that is truly solid--that hunk of iron has a very low vapor pressure, it's not zero. How are you planning to keep your antimatter charge perfectly isolated from it's environment for long enough? And remember, any reactions emit gamma rays on one of three frequencies. If antimatter weapons are a threat do you not think the cops will have set up detectors for those energy levels?

And what sort of thermal load will that decay dump into the equipment? And the warmer it gets the worse your vacuum gets.

  • 1
    $\begingroup$ This. Antimatter is basically the next level of challenge after a thermonuclear device. It might become a useful weapon, but not a simple one. $\endgroup$
    – Therac
    Feb 9 at 9:49

The problems with antimatter:

  1. It is expensive to produce, and when it is produced in particle accelerators it is very high energy. Any terrestrial production facility would very likely be discovered from either the electricity bill or radiation from any other power source of choice.

  2. It is difficult to store and may have an ongoing cost to store. It clearly cannot be stored in a regular matter contained - and at present it seems that electromagnetic storage is the most sensible approach but as we have yet to preserve a single gram we don't know what the setup for a kilogram would even look like.

  3. 1 kilogram of antimatter (2kg total mass) is equivalent to about 50megatons of TnT - nuclear and atomic weapons should be a lot more readily available.

That being said, I'm going to once again take inspiration from scifi to come up with a part solution; in the Night's Dawn trilogy, illegal antimatter production facilities exist in orbit around stars and this does make at least some sense:

  1. You have a high amount of solar energy & radiation to power an ultimately inefficient process.
  2. Any interdiction of the station is inherently dangerous due to the contents
  3. Close proximity to a star will likely make observation difficult without knowing where to look
  • $\begingroup$ Point #3 is exactly what the OP wants. They're after a 40MT bomb without all of the nuclear paraphernalia. The problem with the Night's Dawn trilogy is that they're confined to this solar system, rather than interstellar stuff. $\endgroup$
    – jdunlop
    Feb 7 at 18:52
  • 2
    $\begingroup$ @jdunlop "without all the nuclear paraphenalia" -- the antimatter paraphernalia will be 1000s of times more burdensome. Making an antimatter bomb as small as 40MT is like using a nuclear bomb to replace a 20 kg building demolitions charge because you don't want to bother finding some TNT. $\endgroup$
    – Yakk
    Feb 9 at 14:42
  • $\begingroup$ @Yakk - I am aware of that, but that is the motivation. If you want to say "use a nuke instead", it's still a frame challenge. $\endgroup$
    – jdunlop
    Feb 9 at 17:40


Disclaimer: All this is purely science fiction speculation.

All things get cheaper, smaller and thus accelerators get smaller too. https://www.nature.com/articles/s41586-023-06602-7 Lets assume that even small accelerators can produce on a large scale collission chances. You would need to stack up against the rare odds of collissions by having lots of them so to speak, then traps to cool down the positrons into anti-hydrogen. (The wiki explains it nicely).

Then you need to scale up- first accelerating, then production and then capture. For production and capture you need the equivalent of a clean room, but in an absolute vacum sense.

For what good is it to produce it and annhilate with a stray atmospheric molecule right away. This part of the endavour is comparable to clean room chip production in many ways. Especially as the annhilation can destroy the equipment to cage and capture, leading to unpleasant chain reactions. First its just air-remnants annhilating, the rays producing ionized particles, evaporating matter, then the coils of the electromagnetic cage gives up and the whole assembly goes.

The problem is not only atmospheric particles though, but also the expelled aromatics of rubber sleeves or lubricants boiling out in vacum. Various solutions to that can be tried: Electrostatic charges, Plasma cleaning - but the final stage will always pushing atoms to the floor with light pressure and then dragging them out via stable but binding happy high surface substances.

In storage the material would be seperated into smaller units, unable to affect neighbouring storage should one cook off. Assembly of a pinhead nuke would happen, similar to liquid stages of rocket, short before launch and deployment.

There could be made a case for "self-containment" - aka the anti-matter-matter reactions energy is used to contain the rest of the anti-matter, but this is a) wastefull, difficult to control and can not be minituarized with the technology available at this point in time.


This is a frame challenge.

Science as we know it would make creating such amount of anti-matter effectively impossible sans everyone noticing or being incredibly impractical, but it can be done so by changing things just a little: your universe is a simulation.

By hacking the simulation and directly editing matter so it becomes anti-matter.

Your rebels found out that the world is a simulation, and found the proper rituals to influence it in such a way that the "cheating console" was opened to them - they can now create small miracles, weaved directly from the framework of the Universal Simulation.

This cheating console isn't perfect and has several limitations, but with what they had in hand they managed to create a bit of impossible science - such as a lob of antimatter and the appropriate containing device, which they then use to do their thing.

  • 2
    $\begingroup$ Imagine a gandalf like wizard chanting :" sudo admin password swordfish call alchemist atmyLocation "Fingerpoint" squarecube atomic sign flip" $\endgroup$
    – Pica
    Feb 9 at 8:03
  • 2
    $\begingroup$ @Pica Absolutely! Why not? If they figure our the language of the Makers, and it is sufficiently different from the inhabitants language, you have very fancy magical words! $\endgroup$
    – Mermaker
    Feb 9 at 19:24
  • $\begingroup$ @Mermaker now im looking for scifi magic stories about simulations :P $\endgroup$
    – Seggan
    Feb 10 at 2:55

Today, antimatter is counted in atoms and not in grams. There is no way to produce any viable quantity. It is not something, for which could develop the technology but do not have the money. It is something for which we have no idea, how the technology could work to produce it.

The main problem is not the positrons, but the antiprotons. Positrons are relatively easy to create as they are small, and investing 2 electron-mass of energy can produce an electron-positron pair with a high probability.

Problem is the proton-antiproton pairs. They are 2000 times bigger as the electrons. A particle collision with this energy can result a thousand different outcomes, and the production of a proton-antiproton pair is a very improbable event in a particle accelerator. There is no way to increase the probability. Well, things are more hard: the known laws of the quantum mechanics say, it is impossible to predict the outcome of such a collision. I do not know the exact numbers, but possibly we would need to invest maybe 1000 or million times more energy to create matter as antiprotons.

However, the Russians already could create a Tsar bomb in the 50es, which produced roughly 1 kg of energy equivalent. It is not a very high tech, of course the exact details of the 3-stage nuclear bombs are not things what you could google out on the internet, but it is at least possible.


Don't make and ship; produce on site

Intense laser beams incident on matter can produce a lot of positrons-more than the sources you mention.

The baddies just need to identify a suitable target and blast hundreds of laser beams at it. This could be done from a distance, given the properties of laser. A large number of positrons would be emitted, which would spontaneously combine with electrons and release energy. If the lasers are shot continuously, this would lead to a gradual heating up of the factors till it chars- pretty villainous. It may not even get detected until its too late.

If instead the sudden impact is needed, like a conventional weapon, a ridiculous number of conventional laser beams would be needed to create the impact you intend. However, producing very high power laser beams may be possible in the world you're building.


Small digression: Antimatter bombs are such a waste... You could get destructive results by much simpler and cheaper (and easier to hide) ways, like accelerating smallish asteroid to near-relativistic speeds and then altering its orbit until it precisely hits where you want it. They wouldn't even see it coming, and by the time they did their railgun wouldn't even be able to aim it. Not that it mattered if it did -- 100s of small relativistic-speed rocks are as bad as one larger one.

But back to antimatter, if you're so fixed on it. It is too expensive and complex to produce. But, it should be already available somewhere, just like radioactive elements are (you wouldn't want to actually have to produce radioactive isotopes by fusion - it would be hellishly expensive. But finding them around is much cheaper and easier job, which makes it economically possible at all - same applies to antimatter, only it is usually much harder to find. But you still would hugely prefer to find it around to having to produce it).

In fact, it has been buffling scientists why we see so little of antimatter in space compared to regular matter (if Big-Bang symmetry were to hold, there should be about the same amount of matter and antimatter in the universe, and we do not observe that). Your JRAOT ("Justified Rebels Against Oppresive Teddybears" movement; unfairly called "Unspecified Terrorist Organisation" by propaganda-churning department of that evil Teddybear megacoorp) have stumbled upon the more abundant source of antimatter. So they've built a magnetic nets from unconspicuous off-the-shelf components, and put them to work at that specific corridor where those influx of antimatter particles did not get annihilated by regular matter dusts clouds on the way, and have been collecting that antimatter for months/years by now, little by little.

(ok, perhaps they didn't actually stumbled upon it themselves, but that astronomer who found that antimatter supernova was little too loose-lipped in a bar for his own good. Or might've been an sympathizer. Or had a gambling problem and generous JRAOT branch kindly offered to clean those debts, just for some delay in publishing the results - great deal actually)


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