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Antimatter annihilation is the best source of energy per weight. However, antimatter is not readily available anywhere within reachable distance, it's insanely difficult to produce and contain.

However, if a society with our current level of technology (or just slightly more advanced) discovered a source of antimatter, how could they use it?

  1. Just having a big chunk of antimatter floating in space. I doubt that we could harvest it. Maybe we could bombard it with particles to make it glow, and then harvest that energy, but I guess it wouldn't be much different than harvesting solar energy directly.

  2. If the first version cannot be used at all, let's make it much easier. We get the antimatter in nice self-contained packages (recovered from an alien shipwreck, or trading for it with a different civilization, it doesn't matter). In such a container, the size of a car battery, there are a few grams of antimatter, electromagnetically kept away from annihilating the walls of the container. There is a valve which can be opened to release a thin stream of antimatter, but once out, it is of course free to annihilate itself with any matter, including the container itself, as it is only protected from the inside. So it should either be opened in vacuum or the antimatter otherwise used up or guided by various means to its intended place to be annihilated.

How can such a source of antimatter provide useful work? Would it just be used to heat water which will drive steam turbines, like in a nuclear power plant? Or are there much more effective ways to extract useful work out of it? How could it be used to propel spacecraft?

How could we with our level of technology utilize such a source of antimatter? Besides threatening to use it as a weapon by breaking open the container.

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  • $\begingroup$ With our current technology, antimatter isn't feasible to acquire or use. NASA has some info on the topic. $\endgroup$
    – Frostfyre
    Commented May 9, 2015 at 21:56
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    $\begingroup$ @Frostfyre : the problem with antimatter is that it's very expensive to create, it takes orders of magnitude more energy to create it than what it could release. This is why the question assumes that we get easy access to it and don't have to produce it by ourselves. $\endgroup$
    – vsz
    Commented May 9, 2015 at 22:09
  • $\begingroup$ Our current technology is too prone to failure to want to use antimatter. If we had more access to it, you might see antimatter reactors, but I doubt you would ever see personal antimatter-based applications. $\endgroup$
    – Frostfyre
    Commented May 9, 2015 at 22:29
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    $\begingroup$ Positron Emission Tomography to scan and destroy our brain at the same time... $\endgroup$
    – user6760
    Commented May 10, 2015 at 0:13
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    $\begingroup$ Looking at history, I predict the first thing we'll do if we ever get easy access to significant quantities of antimatter is to build a bomb from it. $\endgroup$
    – celtschk
    Commented Aug 29, 2015 at 17:53

4 Answers 4

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As has been mentioned, a chunk of anti-matter in space would end up annihilating off of something, probably interstellar hydrogen. This would likely make it a bit too risky to try to harvest or use. Or it would have completely annihilated by now. Discovery of a pre-existing supply of advanced technology stored Antimatter, or discovery of a hyper efficient means of producing it would be a more likely scenario.

As for uses, here are a few.

  1. Heat water, spin turbines, produce electricity. This isn't terribly efficient, because a lot of the energy from Antimatter annihilation isn't easy to capture.
  2. Annihilate small (read: miniscule) quantities at a time to produce controlled explosions that can be used as propulsion. This would be a Bad Ideatm in atmosphere, as we'd be spewing Gamma Radiation all over the place. However, there's already plenty of radiation in outer space, so it could safely be used there. Refer to articles on 'nuclear propulsion' to get the idea of a design for this (ref, ref, and ref).
  3. Use a smaller quantity of anti-matter to rapidly heat a propellent and expel it from the ship, producing a more controlled, less explosive propulsion system.
  4. SCIENCE: Annihilating anti-matter in a controlled environment can show us a lot about the function of the universe (most energetic reaction possible). Having easy access to this would allow for a lot more experiments, that could ultimately result in some very useful knowledge
  5. Anti-matter explosives: For when you don't mind making an enemy of the entire world. Or to crack asteroids apart for mining purposes (or to prevent a terrestrial impact)
  6. Medical uses: Matter-Antimatter reactions have shown experimental usefulness in both medical imaging (ref), and a potential ability to treat certain cancers (ref). Free access to Antimatter may expand this field.

Please note, this last bit is PURELY theoretical.

It has been theorized that Antimatter does NOT react to gravity the same way that normal matter does. While many scientists assume that gravity will effect matter and anti-matter in the same way, there are theories out there that suggest that matter and anti-matter will gravitationally repel each other. (ref) We've never had our hands on a big enough chunk of antimatter, or even a small one for long enough to make any sort of experiment. If their theories are correct, Antimatter may be the gateway to anti-gravity systems...which could utterly revolutionize space exploration by reducing the energy required to break Earth's gravity well. Naturally, this would be extremely dangerous if the anti-matter containment were breached.

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Blocks of antimatter in space would go poorly. They would be lit up with annihilation events from interstellar hydrogen. You probably need something to keep the normal matter away from the anti-matter, so alien capsules are a good bet.

The annihilation of positrons with electrons (the most benign of the antimatter collisions) kick off a pair of gamma rays with an energy of 511 keV, which is quite a lot. Using a water bath to turn them to heat is not an unreasonable approach, though trying to find ways to convert them to lower energy photons for absorption via photovoltaic would be interesting.

On a tangential note, research for the previous paragraph lead me across Positron Emission Tomography (PET) scans. Seriously, how insane is it that we have medical uses for antimatter annihilation! Why are we bothering to write fiction anymore? The real world has us beat these days

I do see an interesting question of why the aliens are sending us antimatter. So far we don't really know how to make new matter, so whenever we annihilate matter and anti-matter to power our steam turbines, we're losing matter that we just can't get back. Sure, it's only a few grams... but could they be playing a long game? We'll run out of planet eventually.

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    $\begingroup$ "We'll run out of planet eventually" : We are running out of things many orders of magnitude faster than how we would run out of matter if we used antimatter to cover all our energy needs. If sacrificing a small mountain's worth of matter would cover our energy needs for the next few million years, that would be a much more sensible "sacrifice" to make than what we are doing with other non-renewable resources right now. Nevertheless, your points are very interesting, but my main question was whether we could find a more efficient or more direct use of antimatter besides steam turbines. $\endgroup$
    – vsz
    Commented May 10, 2015 at 7:49
  • $\begingroup$ @vsz That's why the first part mentioned the actual physics behind antimatter annihilation: the products are remarkably hard to capture and use more efficiently than the basic steam turbine. However, I find a staple for intriguing storylines is a person or culture who trades away something they think is of low value, only to find its value was higher than they ever knew. A few million years is one thing, but the long run is a different story all together. Stephen Baxter has a beautiful book, Manifold Time, that covers what happens when we try to think pas the millions of years. $\endgroup$
    – Cort Ammon
    Commented May 10, 2015 at 15:22
  • $\begingroup$ We might be swapping with a mirror universe, so each gets its anti with an equal exchange of mass. $\endgroup$
    – JDługosz
    Commented May 11, 2015 at 9:09
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With option 2, assuming that the alien anti-matter containers are crash-proof, I'd use the anti-matter to make rockets with. Space flight is an area where a comoact, low-mass source of energy is practically paramount.

Not rockets that mix the matter and anti-matter at a 1:1 ratio, but rather using a very little bit of anti-matter to heat a lot of propellant. This could have twice the performance of the space shuttle's main engines.

Beyond earth orbit, using an anti-matter box to provide electrical power to a spacecraft and to ignite fusion fuel pellets could be leaps and bounds beyond any near-term interplanetary propulsion system.

It could certainly be used for ground-based power generation, by using it to to turn water into steam directly. Or by igniting fusion fuel pellets, though I imagine that'd be more complicated.

I'll leave it as an exercise for the reader how exactly we'd figure out how turning on dial lets out a little bit of anti-matter. Or how many researchers we'd need to go through to find out...

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  • $\begingroup$ It is very depressing that ISP using antimatter is only twice that of a chemical rocket. NASA claims a design with an ISP of 5000 at least. nasa.gov/exploration/home/antimatter_spaceship.html and they at least hint that they consider this to be practical even considering the high cost of antimatter. $\endgroup$
    – Gary Walker
    Commented May 13, 2015 at 20:26
  • $\begingroup$ @GaryWalker The figure "only twice that of a chemical rocket" is for a high-thrust engine for surface-to-orbit transport. I am not positive, but it looks like the "ablative engine" referenced in the article you linked is meant for use when already in space. I'm not positive, though. And it's a really cool article, regardless. Thanks! $\endgroup$
    – Darth Wedgius
    Commented May 13, 2015 at 21:00
  • $\begingroup$ I agree with your statements. Should have noted that the ablative design depends upon positrons, not anti-hydrogen. Part of the reason this is very important is that we can make positrons much more easily than we can make anti-hydrogen, thus potentially economical according to NASA. Maybe we are stuck with VASIMIR, etc. for quite a while. $\endgroup$
    – Gary Walker
    Commented May 13, 2015 at 21:10
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Antimatter is insanely dangerous. A large chunk of antimatter in space would rapidly annihilate, due to asteroids, tiny chunks of debris, interstellar hydrogen, and pretty much anything else. Even large amounts of charged particles will set it off, not to mention that no mechanical device can touch antimatter without catastrophic explosion. (this assumes the antimatter chunk is solid antimatter)

Stored in an electromagnetic container makes it far safer, but still not very safe. With sophisticated enough transport devices (like CERN's supermagnets capable of holding charged antiparticles) we could try and siphon it off to a reaction chamber where it is annihilated with air or any other matter. This, however, releases a lot of high-energy EM radiation (gamma rays) which could either be harvested by very high threshold photoelectric materials (not a bad idea) or by deflecting it at a large mass of water to heat it, vaporizing it. Or we could direct antimatter at the water itself, causing some to be destroyed while superheating the rest; but, since a large body of water's surface area to volume ratio isn't too good, it may not be the most efficient way to harvest it.

On a more mathematical note, let's find an actual energy amount of a single antimatter package. Assuming there are 3 grams of antimatter per package (bottom line) then using E=mc^2 (antimatter has 100% mass-energy conversion) yields around 2.6962655e+17 joules, compared to the Hiroshima explosion, where 700 milligrams of uranium was converted (6.2913e+13 joules). This amount of energy suddenly being released is a VERY bad idea, so a more gradual approach is a better way to harvest. Considering the amount of energy here, we can acheive power greater than a nuclear reactor.

TL;DR - antimatter explodes when it touches anything so we gradually siphon it into water and boil it to power a turbine.

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