The F1 engine required baffles on the injector plate to control combustion instabilities so that it wouldn't blow itself up. Was that unique? Or do other engines also have baffles for the same reason? I know that the Russians like to use multiple smaller engines for that reason, but I'm really wondering about other engines with an F1-style solution.

This question by Rajath Pai triggered my question.


2 Answers 2


In early versions of the Space Shuttle Main Engine (SSME), the main injector was baffled. The baffles were formed by extra-long liquid oxygen posts protruding from the injector face.

Block IA engines and later removed the baffles. (See "Taxonomy of the SSME" in this answer.)

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The injectors on the preburners were also baffled in a similar manner. As far as I know, these baffles were not removed. (This presentation used in a 2011 class but dated 1998 shows the preburner baffles present.)

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Reference: SSME Pocket Data Book.

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    $\begingroup$ RD170 baffles look similar but with 6 radial baffles b14643.de/Spacerockets/Specials/Energomash_RD-170/combustor.jpg Using nozzles to make baffles is a win-win. You dont lose any area and the propellant keeps them cool. But it seems the idea didn't occur to them for the F1 . With 6 baffles I suppose you could have a three lobed oscillation with alternating pressures high-low-high-low-high-low. SSME uses 5 baffles, an odd number. I wonder if that is superior (only allowing for a 10 lobed oscillation) and if not, why it was rarely done. $\endgroup$ Sep 3, 2019 at 18:33

As noted in my comment on Organic Marble's answer, the RD170 baffles look very similar to the SSME, but with 6 radial baffles instead of 5.

Using nozzles to make baffles is a win-win. You don't lose any area and the propellant keeps them cool.

According to this the baffles on the Saturn V's F-1 engines were cooled by fuel. At first glance there don't seem to be any nozzles to release the fuel directly into the combustion chamber, but there are in fact tiny holes on the tips of the baffles.

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    $\begingroup$ The RD-170, that's four combustion chambers, isn't it? And each of them aren't that big. I thought the Russians did that as an alternate way to deal with instabilities, and there they are using the nozzles to make baffles in each of the combustion chambers. Well, it obviously works. $\endgroup$
    – Greg
    Sep 4, 2019 at 21:21
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    $\begingroup$ @Greg It depends what you mean by big. The RD191 uses just one of these combustion chambers and at 2 meganewton is still quite high up on the table at en.wikipedia.org/wiki/Comparison_of_orbital_rocket_engines . The only bigger chambers (not counting solid fuel, or other members of the RD170 family) are on the RS25 (space shuttle) RS68 (delta), F-1 (saturn V) and the complete but as yet unflown Blue Origin BE4. The field gets pretty crowded between 1 and 2 meganewtons though. $\endgroup$ Sep 4, 2019 at 21:59

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