The original question was: Is it possible to breach the center of a nebula? If you were in a nebula, you probably wouldn’t notice the gas at all. The difference between deep space and the inside of a nebula is pretty small. So getting to the middle of one in any reasonable amount of time would involve moving at relativistic velocities (near light speed). To get from the edge to the center in less than several years would require moving at around 95% of light speed or faster.