Agreed, with the caveat that you can make more reliable rocket _components_ that way, and you can use those components to assemble a more reliable system from t

Agreed, with the caveat that you can make more reliable rocket _components_ that way, and you can use those components to assemble a more reliable system from them. No matter how reliable your individual components are, the added complexity from using many of them together in an already complex system is an area of concern. As a small example: the Falcon 9 has 9 Merlin 1-D engines pulling from shared RP-1/LOx on the first stage. Combustion instability in any one of the engines can induce a 'pogo oscillation' in the fuel lines that can stress the structure of the spacecraft. More engines means a higher risk of instability inducing such an event and damaging the spacecraft. Afaik, no one really has a generalized solution for dealing with pogo oscillations but many (including SpaceX) have ad-hoc solutions for specific rocket designs. The wrinkle here is that the Falcon Heavy is going to not only have 3 Falcon 9 cores, these cores will also be cross-supplying fuel/oxidizer to each other (i.e. the left and right cores will feed the center engines before separating). Even small changes in rocket design can bring underlying issues to light [0], and ad-hoc solutions, by definition, shouldn't be expected to solve them across the board. [0] Anecdotal again, I know, but: I was speaking with a solid rocket engineer a little while back who had helped diagnose a combustion instability. The root cause ended up being that the aluminum pellets embedded into the oxidizer were shaped such that they could clump together and create small bursts of excess thrust under certain conditions. This excess thrust had happened in just such a way that it created a standing wave inside the combustion chamber which vibrated the entire structure during flight. Other designs didn't have this problem (e.g. slightly different lengths of the combustion chamber, slightly different ratios of fuel/oxidizer).