At the core of the powerpacks of the upcoming generation of powered exoskeletons are dusty plasma fission fragment reactors, in which nanoparticles of nuclear fuel inside a vacuum undergo a fission reaction, are ionized in the process of doing so, and are then "squeezed" from the reactor, like Satan's own, highly radioactive toothpaste, by a magnetic field. Although the resultant plasma jet was originally intended to be shot out as propellant to enable our deep-space missions, it turned out that aiming it into a magnetohydrodynamic generator lets its great heat and directional velocity be converted into enormous amounts of electricity for its size — a high specific power, that is.

Thanks to this high specific power, we project that it will be possible to mount true armor on this generation of exoskeletons, rendering their wearers resistant to all handheld weapons our adversaries are currently expected to field. As this system generates power via roughly the same principle as a conventional gas turbine — that is, a high-velocity gas stream whose kinetic energy is converted into mechanical or electrical power — it has been dubbed a "nuclear gas turbine".

However, some things must be known before we receive the mid-stage research grants required to produce a prototype. One such concern is sound. We are concerned about the auditory environment such a novel source of power may generate, both in terms of stealth and operator safety (for instance, do we need to include intercom-equipped earmuffs inside the helmet?)

What would such an energy source sound like? Would it hum? Would it scream? Would it rumble? Would it hiss? Would it pop its operator's eardrums like jujubes? Could it perhaps be a distinctive noise along the lines of a Katyusha rocket launcher or an MG42, something soldiers would recognize and fear by sound alone? For maximum "the VA has concluded your deafness is not service-related" vibes, could it potentially even be all of the above?

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    $\begingroup$ @JBH There's no rotation here, as MHDs lack moving parts, which, incidentally, is why they're so efficient: no icky mechanical bits to leak energy as heat. Regarding opinion-based questions, I believe TheDemonLord has provided a good example of a non-opinion-based answer by naming various non-subjective characteristics of a fast-moving plasma jet that would produce a certain, distinctive sound. $\endgroup$
    Jan 21 at 2:58
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    $\begingroup$ when 2 nuclear armors meet, do they go "choo choo" $\endgroup$
    – user6760
    Jan 21 at 4:05
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    $\begingroup$ @JBH It's a turbine in the same sense that a modern smartphone is a phone or a Ford F-150 Lightning is like a Model T: a skeuomorph, i.e. the same thing in a very abstract sense but so different the only thing in common is the name and original concept. It still converts hot gas into usable work, it's just that the gas is now ionized, ultra-hot fission fuel, the spark plug has been replaced with a neutron generator, the mileage is now expressed as a fission burnup fraction instead of liters per kilometer, and the gas is directly used as a conductor rather than spinning a rotor within a stator. $\endgroup$
    Jan 21 at 4:14
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    $\begingroup$ @JBH The OP has been exceedingly clear in their description of the function of their device, even going so far as to include handy wiki links. You could ask them to revert their title change if you consider the misnomer confusing, but there's certainly nothing here that warrants closing the question. $\endgroup$
    – M S
    Jan 22 at 0:33
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    $\begingroup$ This Q is closed over semantics? There seems to be sufficient details. Clarity is there. OP has dubbed it a "turbine", so what? It's a turbine that uses different means to propel fluids. Magnetohydrodynamics isn't made up, it's a real field of science & engineering. If someone asks about a "hover car", are we going to close the Q because it doesn't drive on wheels? $\endgroup$
    – BMF
    Jan 23 at 14:35

1 Answer 1


Musical answer here:

Sound is a function of many things - but let's go through them:


The pitch of a note (high or low) is related to the number of vibrations per second. These vibrations could be explosions, could be caused by plasma jets rushing past a point, etc. To give an idea - think of a car engine, and compare a really low idle (that doesn't have much of a note at all) to the sound of a glorious F1 V10 screaming at full chat.

Since your power source has a jet of material, they generally have much higher pitches for various reasons.

If stealth is a consideration for your suits and humans - then my suggestion would be to 'tune' the engines to operate in the ultrasonic region (above 20,000 Hz or the human hearing threshold) - just hope they don't have any dogs.


Compare a flute to a bugle - both can have the same note pitch (vibrations per second) but the sound (or timbre) is very different - a bugle works by blowing a raspberry (oversimplified) which is a number of unique pops or 'kisses' that create the sound Visual here of a slow-mo trumpet, whereas a flute's sound is created by the air turbulence in a continuous breath, the turbulent air creating the vibration - that's why a flute's sound for a given note sounds more continuous than a trumpet's.

Interaction with the Air

You mentioned a vacuum, but you also mentioned that the exhaust is routed through a thingy that creates lot of energy - which presumably eventually vents to the outside world.

Is so - then when the super-hot gas hits the air, it's going to expand - that's going to cause vibrations and a change in sounds: ignoring the Super Mario brothers theme, listen to the underlying sound of the plasma being generated - that hissy continuous sound: here Add a lot more overtones and bass notes (bigger exhaust, more air etc.) and I think you've got something, perhaps some intermittent crackling from either static charge build up or from a general 'Sci-fi backfires are cool' perspective.

In terms of military - if you are wearing powered exo-skeleton armour, you're going to wear a helmet. This would dampen any overpressure noises. The noise would probably be very distinctive insofar as 'that's an exosuit engine' - but not distinctive enough to say 'That's Private Bob'. Would the soldiers fear it? Only if they have no means to defend against it, otherwise it's a handy-dandy early warning that someone is coming.

Oh, and your hearing loss is definitely not service related.

  • $\begingroup$ So a relatively high-pitched, continuous hiss/scream with an occasional snap/crackle/pop thrown in. Basically a gas-turbined MBT which caught a cold, then? Like a higher-pitched version of this (youtube.com/watch?v=sXE4tMEYCoI)? Sweet. $\endgroup$
    Jan 20 at 23:53
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    $\begingroup$ @KEY_ABRADE - pretty much, perhaps a touch more electric-y sounding (think the sound that Arcing electricity makes) - but other than that - sounds pretty badass. $\endgroup$ Jan 20 at 23:58
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    $\begingroup$ No problem hearing or seeing them coming though. Each soldier will have the thermal and noise profile of a small jet engine. $\endgroup$
    – Mon
    Jan 21 at 0:45
  • $\begingroup$ @Mon Oh, certainly, but that ultra-high specific power means they can mount defenses capable of resisting many types of weapons, and they're still as hard to hit as a human. It's like being attacked by a horde of mini-IFVs: if going up against them, it's good to have air power, proper armor, pre-set mines/IEDs, laser-guided artillery, or a whole lot of crew-served weapons up one's sleeve. $\endgroup$
    Jan 21 at 0:55

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