My understanding is that it’s just the large nozzle extension that’s made of niobium as it’s radiatively cooled - the upper part of the bell and the combustion chamber is cooled by pumping propellant between the walls, so it can just be made of steel.

This is what the Merlin Vacuum engine looks like without the nozzle extension (though this is 1C): Image

It’s possible that the ‘stubby’ engine is just this.

You’re right, this is some homebrew I wrote for my DS when I was in highschool.

But it was nothing as clever or logical as that! I think I had read somewhere that floats were really expensive on the DS ARM9 CPU, as was division (?). So to allow fractional values for object positions, etc, you would store them in an integer at 256x their true value, then shift it by 8 to the right to ‘divide’ by 256 and get the proper value back.

Not sure whether this was actually true, but either way this would’ve been completely cancelled out by calling that ‘lowestXInObj’ function 20 times per frame - it loops through every object in the scene!