25mm Payload Rifle [Ultratech]

[Jack Sawyer]

ETC/PET (Electrothermal chemical and pure-electrothermal) always occupied a rather broad spectrum in terms of how I've understood it.

A link here discussed 120-140mm conventional and ETC guns, and they depicted five different versions (page 7 onwards) and differing in terms of performance vs electrical requirements.

On the low end you have just 'ignition' which may provide little or no improvement but also requires little electricity. Getting up that gets you into ignition with other forms (solid, liquid and presumably even gas propellants like a Light Gas Gun.) Some articles I've read threat this as a separate category from 'true' ETC and call it 'ETI - 'eletrothermal ignition'

Midpoint is what most people think of with ETC I think.. you're not just igniting the propellant via electricity, but adding electricity to the propellant to enhance performance. Next up is ETC with low molecular weight propellants (H2 additives) bringing gun performance closer to light gas guns.

At the extreme is 'pure' electrothermal which is using electricity with an inert propellant. Potentially best 'performance' wise but also requiring the most electricity (and may not be as efficient as railguns or coilguns.)

And honestly I'm not even sure that covers the full nuance of the spectrum even then (you can do ignition and combustion with liquid propellant and gas propellant. In alot of ways short of pure ETC, the best 'performing' ETC gun is an electrothermal light gas gun potentially.

This I think also covers other variations (ignition vs other kind.

I suppose you could assume there are a few defined 'points' on the spectrum for a given term, and then allow that there might be some overlap between those depending on electrical input, kind of propellant used, etc.