In my world, alien 'reactors' are discovered that are very efficient at creating power (around 1000x better than fission), as well as requiring little fuel, making them the perfect power source.

However, these reactors are not simple, no, they are advanced. Take nuclear fission for example. Nuclear fission can be defined by a set of equations, primarily $\ E = mc^2$ , such that with sufficient information (temperature, fuel quality, void coefficient, temperature coefficient, etc.), you can model how the reactor will behave for the next 100 years, to a high degree of accuracy. You can, for example, hook a simple computer up to a nuclear reactor, and have it set the control rods based on how hot the reactor is, and with enough conditions, luck and failsafes, it will never explode or stall*. The same is true for burning a fuel, nuclear fission, and most other types of power generation.

*Something might break within the reactor, or a meteor might hit the plant, but that doesn't count. I am not liable for any damages caused by trying to fully automate a nuclear reactor.

However, these alien reactors are different, they use some underlying mechanism that cannot be predicted at all, past a few milliseconds. The reactors, if simply started, will explode in less than a second, as they quickly destabilise. In normal operation, seen in the one functioning reactor, the power output oscillates seemingly randomly, never becoming dangerously high. Even in destabilisation, the power doesn't simply shoot up, it oscillates within the safe range, until it simply shoots up, destroying everything in a large radius.

To make sure that the output doesn't destabilise there are a few variables that are controlled, similar to the control rods in a nuclear reactor. For the purpose of the question, these variables can be anything controllable about the reaction, but they have to be given the correct values based on the current output in order to keep the reactor stable. The aliens used highly advanced computers to predict the correct values, but they won't turn on.

Its like if each of the control rods in a nuclear reactor were constantly, randomly, changing from high neutron absorption (good) to high reflectivity (bad), and you need to tell, based on whether the power is rising, if you want them in or out, and react to that before the thing explodes. Also, any two reactors will have behave completely differently, even when close to each other and physically identical.

My question is, what mechanism could they be using to generate power? What is making it so unstable?

To summarise/TLDR:

  • Power fluctuates based on control variables
  • Control variables affect the power level randomly, but this changes with a gradient so that they can be predicted a few milliseconds in advance
  • If the power level is not regulated, it will explode
  • Control variables can be anything, temperature, shielding, how much fuel you give it, etc.
  • 3
    $\begingroup$ I object to the "science-based" tag; anything fitting your specifications is going to be so wildly speculative as to be equivalent to magic. $\endgroup$
    – jdunlop
    Commented Oct 24, 2019 at 17:35

3 Answers 3


I actually agree with N. White's topographical answer but if you want to stay in the known dimensions, not going too far off into science fantasy here's an idea:

To be honest self-sustaining fusion reactors fit this description perfectly. It can be literally the world's most powerful bomb controlled by nothing but magnets, if designed for maximum power output.

Very cheap and common fuel:
The fuel is Deuterium. It can be distilled from all forms of water. It is a widely available, harmless, and virtually inexhaustible resource. In every cubic metre of seawater, for example, there are 33 grams of deuterium.

You need to get your alien core to 100,000,000 degrees and keep it there perfectly, or BOOM (yeah, that's reality)! So here on little earth, well, there is no material that can contain things that hot. Our reactors melt instantly.

Power fluctuations:
The temperature is focussed with enormous magnets. Solar activity, earth's field, and many other things can cause fluctuations. Change the magnetic field = change the temperature = either shutdown or BOOM! (I will explain). It requires very precise controls to accurately control the temperature inside a fusion reactor. Our fusion reactors today can only run for 4 seconds tops - usually less than that. Magnetic containment fields are so intense that superconductors don't even work near them, our fusion reactors have to use old-fashioned copper wiring to even function (this is reality). Your aliens have found some superconductor which can compensate for the huge magnetic fields - but only with the help of a very powerful computer making nanosecond adjustments.

Very explosive - MUCH more powerful than an atom bomb:
Now if you google "can fusion reactors explode" the answer will be "no" because they are talking about the research reactors we have today which can only run for 4 seconds. Existing fusion reactors do not have a breeder fuel source, they need a constant fuel intake like your engine, and MASSIVE energy input. Fusion reactors on earth are NOT power generating reactors. However, you are looking for a power generator. This means a self-sustaining fusion reaction. In that kind of reactor, which is only theoretical today, it will have a lithium deuteride breeder blanket for sustained fuel (just like the bomb), which will produce tritium just like the thermonuclear bomb does. Fusion of deuterium with tritium creates helium-4, freeing a very fast neutron, and releasing 17.59 MeV. The neutrons sustain the chain reaction. The only difference between an uncontrolled thermonuclear bomb and a controlled fusion reactor is the containment.

Your unpredictable chaos element is in the advanced containment field, which relies on quantum decoherence to prevent high-energy particles from hitting the walls of the containment chamber, melting it. If this happens, it will heat the breeder blanket until it achieves a runaway Deuterium-Tritium Fusion reaction making the breeder blanket into one of the largest thermonuclear bombs ever.

Lithium-deuteride breeder blanket ( A true 6lithium deuteride breeder blanket concept)

Alien control:
Your alien technology controls the quantum decoherence matrix keeping the super-energetic particles contained. In the one reactor, this is working fine. In the others, the plasma melts the chamber within seconds and quickly bombards the lithium deuteride fuel with fast neutrons leaving a 3-mile-wide crater and fallout around the globe.


A properly designed fusion reactor is very safe from exploding, if you want to have limited power and a constant power output. But in reality, our current fission reactors are also inherently safe from melt-down when built properly. But as we all know, the Russians did a very stupid thing and built a fission reactor using a graphite moderator. This was a very DUMB design, and they could not control it when it went prompt-critical.

Just like earth reactors can be built badly, fusion reactors can be built badly by making them nothing more than a controlled thermonuclear explosion. Your aliens did this on purpose - not because they were stupid - they were very advanced and had the technology to control quantum decoherence and make the process stable. We have no idea how to do this, so the alien computer and systems is the only thing preventing these generators from becoming a bomb.

  • 1
    $\begingroup$ The thing about fusion reactors is they're actually pretty fail-safe, because it's difficult to keep the reaction going. And while the reacting materials themselves are hot, there isn't that much of them. $\endgroup$
    – ltmauve
    Commented Oct 25, 2019 at 0:36
  • $\begingroup$ That's true of the ones which do not sustain a reaction like we have today, not the ones he wants - which actually generate more energy than they consume. $\endgroup$
    – Vogon Poet
    Commented Oct 25, 2019 at 0:38
  • $\begingroup$ Yes, because that's how fusion works. The conditions for fusion are only stable at stellar scales. Outside of that, conditions must be enforced by machinery. If the containment fails, there's not enough heat energy in the reactor to actually cause it to explode. $\endgroup$
    – ltmauve
    Commented Oct 25, 2019 at 0:42
  • $\begingroup$ You know in a stable self-sustaining fusion reactor all the same components of the H-bomb are there except the neutron generator. A stable reactor will have a lithium deuturide breeder blanket for sustained fuel, which will produce tritium with enough heat. Fusion of deuterium with tritium creates helium-4, freeing a neutron, and releasing 17.59 MeV. The only difference between an uncontrolled fusion bomb and a controlled fusion reactor is the containment. Today’s reactors don’t have breeder blankets - for safety. $\endgroup$
    – Vogon Poet
    Commented Oct 25, 2019 at 3:11

Multi-dimensional potential energy.

Basically, the multiverse is layered, both in time and space. Essentially the reality layers slide over each other. The layers are not smooth, but vary topologically. The further the distance between our layer and the next is basically where the energy comes from. The technology can view only a small radius of the other layer, so it has only a limited amount of time to respond to the upcoming changes in potential energy. What you are controlling is how much energy you shunt to a third layer. Shunt too little and you explode, shunt too much and you implode.

  • $\begingroup$ I like it. I sometimes substitute multiple dimensions for a dark matter universe existing right on top of ours. Its virtually undetectable as it doesnt react with normal matter (hence dark matter) and is just as good an excuse as tapping another dimension. $\endgroup$
    – Demigan
    Commented Oct 24, 2019 at 17:13
  • $\begingroup$ I think that actually explains it perfectly, thanks $\endgroup$ Commented Oct 24, 2019 at 17:58

I think the base answer would be "the energy of the vacuum, somehow". Its one of those things that has power but we cant get at it because you have to exchange energy with it but it is virtually impossible. But if anything should work as randomly as your reactors than the quantum fluctuations of the vacuum energy should be a prime suspect.

  • 1
    $\begingroup$ Pretty sure Rodney McKay blew up a solar system with this one. $\endgroup$
    – Joe Bloggs
    Commented Oct 25, 2019 at 15:19

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .