The thing about that particular model is it looks like it would be able to do some sort of thrust vectoring by changing the shape of the throat and divergent section, but since KSP doesn\'t model gas flow (thank god, i like realism but that is wayyy too much lol) it just looks cool. And as Nova said, the spikes are usually flat or slightly concave at the end to conserve mass, and at the speed the combusting gas flows out of the engine, it forms a vortex area that mimics the shape of the end of the spike anyway. I think the amazing part of all this is that this technology has been around since the 60\'s.