I was doing some back of the envelope calculations to see improvements SpaceX would have to make to reach a cost target of $100/kg into orbit. After doing some basic calculations, it seems that SpaceX would need to increase the cycle life (number of ignitions or stress cycles) that the engines go through. I tried back calculating what the current cycle life of the SpaceX Merlin 1D engine is, but couldn't find the relevant data (a weight breakdown of the engine components) to calculate it. Does anybody know what it is or where to find it?