It's a fissile element in Nuclear Reactors, not anything that you can physically burn. The Lore indicates it is used as such, and the reactors power some sort of plasma thrusters or nuclear rocket. Presumably an MOX based reactor system would simply be the power plant for a similar technology (or extrapolation thereof).
As a fuel or fissile element, MOX is highly impure though. It's cheap for electricity generation, but for anything really cool or explosive you'd need highly enriched, weapons grade uranium or plutonium, and that is presumably tightly regulated. Don't ask me how I know this.
Presumably, H-fuel is used for smaller craft, and MOX in the reactors for larger ones. Nuclear fission is a well understood process, but fusion is a bit trickier, since we've yet to get out more energy from a fusion reaction then we put in as of the 21st century. We could extrapolate it that fusion engines are somehow haxy or impractical for spacecraft propulsion technologies in the FL verse.
For Vanilla FL's developers to understand that something as obscure as MOX would be used in a way sort of hints at that.
Then again, Freelancer tends not to stick too tightly to real world physics.
No matter how we put it, energy output of fission is nowhere near that of fusion. And ships in FL require excessive amounts of energy for magnetic confinement of plasma, resonance heating and not to mention all sorts of exotic weaponry. Indeed any possible losses of energy would be minimal due to the widespread use of superconductors, however the consumption would still be substantial.
Hence a fusion reactor (be it a tokamak, stellarator or something completely different 1k years in the future) to power all those systems seems practical. Not to mention the relative ease of obtaining fuel resources from planets. In twenty years (to be a bit more pessimistic than the officials) ITER will have an excess of power. The humanity's development must have stalled considerably in FL universe to account for the unreliability of such systems.
Although, when we think about it, the fact that something as squishy as a human, and not one hundred g withstanding AI, is still conducting combat operations in FL does indeed make a point.
Yes. It's entirely your fault, Kikatsu. Have at you! *stab*
Anyhow, there's no reason Fission and Fusion can't exist separately for different applications and cost ranges. Taking into account the thriving plutonium industry and nuclear devices commodity, higher-efficiency fission type reactors might have applications that fusion powerplants would be too expensive, dangerous, or maintenance intensive for.
Considering that a fusion plant means having a self-contained miniature multi-million degree sun on your ship, any breach of containment would cause very bad things to happen, plus, it requires humongous magnets to keep the reactor from becoming screwy, which could interfere with computers or sensors or something. A fission type fuel pile could theoretically be more controllable, cheaper, or simpler to operate. The only real moving parts it would have, at it's barest, are control rods and coolant pumps. It can still melt down if coolant isn't applied or spew radiation, but that's a bit better than 'spinning exploding ball of plasma in the middle of ship'.
Yes, I feel like nitpicking today, hehe. Burn me with a plasma torch if you want to.
*The not so famous or renowned Spaaaace.Archaeologist, aka. Sokol, aka. Stricev (Stričev) threw a shovel as hard as he could at the nearby tree. For the good part of the day he had been excavating a pit on the graveyard of Disco; a grim and desolate place of gloomy shadows cast by dilapidated tombstones, which were illuminated by the ghostly light of a poorly textured Moon. Above, in the night sky dotted with millions of cold stars, ships could be seen - nothing more than brief scintillations giving rise to the idea that space was not as empty as it seemed.
Finally! He uncovered the long lost corpse! Let its rotten stench spread in the night air, let it...breathe again!*
Rheinlanders continue to use MOX on their fighters and freighters. That is wrong.
Please just consider it a name for your own sanity.
The lore is quite explicit that Rheinland still uses fusion power on it's vessels and still needs the H-Fuel it was willing to start a war over in the first place.