The End of the Space Age

[Seggybop]

Clustering is nothing new. Indeed, its the principle that got and gets most rockets (above a payload of a couple of tons to LEO) of the ground. The F1 rocket engine just barely managed stable combustion due to it's size and they still had to cluster five of them to get a Saturn V going.

I've read that the combustion instability problems with the F1 engine were more the result of strict efficiency requirements rather than a global problem with using large combustion chambers, and if some (unknown) level of efficiency was acceptable to sacrifice, large combustion chambers were fine. I think this may have been part of the rationale for the single huge engine of the Sea Dragon rocket, which would have had no pretense of efficiency but would still lift huge amounts of cargo through brute force.

[Skgoa]

Well... the problem is that its all an interlocking system of interdependent and sometimes mutually exclusive goals and parameters. Amongst other things, higher efficiency means you have to carry less fuel (i.e. weight) and is thus just as important as raw thrust. Actually, its even more important, thats why nowadays we go with hydrogen and not RP-1 as the fuel of choice. But even if we are only looking at getting the most thrust out of the fuel, its pretty darn obvious that the biggest factor is the internal efficiency of the engine. I.e. how much higher you can get temperature (and thus pressure) of the fuel/oxydizer mix between the points where it enters the combustion chamber and where it exits. The more you scale the system up, the harder this gets to engineer and at some point the square-cube-law just smacks you in the face.