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Can anyone tell me the difference between staged combustion and full flow staged combustion?

Does full flow mean there are 2 preburners (fuel- and oxidiser-rich respectively) or does it mean that all of the propellant goes through the preburner before entering the combustion chamber?

I've drawn picture for reference.

(that red line drawn to FR (fuel rich) on the left is meant to be a label line, not plumbing)

The far right is definitely full flow staged combustion but what are the other two?

Also, I've noticed that the SSME is almost the same as the rightmost but it has some oxidizer go straight to the combustion chamber. It is classified as staged combustion. This suggests full flow means both propellants are flowing through a preburner before getting to the combustion chamber.

But what then are the 2 diagrams on the left?

Nathan Tuggy
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user2471379
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  • The SSME is closer in operation to the leftmost illustration, not the rightmost illustration. – Tristan Apr 05 '17 at 16:55
  • All 3 are closed cycle as opposed to an open cycle like a gas generator cycle (F-1, Merlin) or combustion tap-off cycle (BE-3). –  Apr 05 '18 at 18:23

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Yes. Full Flow Staged Combustion is both a Fuel Rich and Oxidizer Rich Staged Combustion combined together so both parts all go through partial combustion first and then a final combustion later. Your left drawing would be Fuel Rich staged combustion where all of the fuel goes through partial combustion but the Oxidizer is just pumped in.

Your middle one would be something in-between a Gas Generator Cycle where the part of the fuel that is burned to power the pumps is just dumped overboard and a Staged Combustion Cycle where all the fuel flows through that before being burned. I don't know if there is a name for that or if it is actually used anywhere.

Evan Steinbrenner
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