maybe it's a smoke canister, like the ones on the Blue Angels and Thunderbirds planes they use to look all cool during shows
it's a "pretty" thing
But really, I believe it's simply so you know when you are turning normal versus strafing versus turning around with engine kill on. But at the same time, it just LOOKS cool, so why not
And someone somewhere here was mentioning there may be a reason for sound in space
And if you really think about it, space isn't empty. There are gases, atoms, molecules etc. in space. The difference is there is much much much more distance between each particle of whatever, so you can't tell their there without instrumentation
Figure, all that crap the Sun spews out with a solar flare has to "travel" thru space to arrive in our atmosphere, so there is "stuff" in space just like there is "stuff" in the air we breath, even if we can't "see" it
So, maybe there is some sound in space. But a lot of what you really hear is sound transferred thru the ship's hull. Vibration that is transferred to audible sound inside the cabin. But either way, would you rather have a game with NO sound? How boring would that be? ugh!
regards,
RogueOne