Rocket exhaust plume expansion with altitude.

[Galane]

Something most space games don't show correctly is how rocket exhaust plumes spread out sideways as atmospheric pressure drops during ascent. In the vacuum of space, the exhaust spreads very wide, nearly at a right angle to the edge of the nozzle.

That's why it's so difficult to design a rocket nozzle that works well over a broad range of altitude. One made to work best in space is 'choked down' near the ground and one made to work well near the ground loses a lot of efficiency at high altitude or in space.

[Sean Mirrsen]

Except the Aerospike nozzle, which uses exhaust constrained by some hydrodynamic principle or other (or something to that effect) to maintain efficiency across all altitudes at the cost of mass.

But yes, something to that effect would be neat to see.

[Whirligig Girl]

I pointed out to C7 on the KSP stream about the age of the Engine FX, and he said he'd like to re-do them.