# For F1 rocket engine, why propellant holes were not in proportion to the fuel to oxidizer ratio?

I understand that the F1 rocket engine had (approximately) 1428 Oxidizer holes and (approximately) 1404 Fuel (RP1) holes in the injector plate. Since the Oxidizer to fuel ratio was 2.27:1 for the F1 engine, why the propellant holes were not in similar proportion?

• The ratio is a mass ratio, not a volume ratio, so you'll need to adjust based on the relative densities of the two. Are the holes the same size? May 14, 2020 at 17:51
• I found different information about hole numbers: " verfügte das F-1 über einen Kopf mit 3.700 Öffnungen für das Kerosin und weitere 2.000 bei dem Sauerstof" In English: 3700 holes for RP-1 and 2000 for LOX.
– Uwe
May 14, 2020 at 18:22
• This document yang.gatech.edu/publications/Journal/… says that the total area of the holes was 548 cm^2 for the RP-1 and 397 for the LOX. May 14, 2020 at 19:40
• @ Russell, Uwe and Organic Marble. Thanks a lot. I do agree that the numbers I wrote may not be the correct numbers (I have taken them from Heroi... site) and also that many other factors might have been considered while designing the injector plate. I was & interested even now, whether the Mass ratio (2.27:1) was maintained or not !!. It could have been in many different ways such as different number of holes &/or different hole diameters &/or different flow rates (by varying pressure) etc. I am curious to know if the ratio was maintained or not. If yes, how exactly. Hope to hear from you. May 15, 2020 at 14:40

There are different numbers on this NASA page about Saturn V:

Finally, the fuel squirted through 3 700 orifices into the combustion chamber to mix with the oxidizer, which entered through 2 600 other orifices in the injector face

If the hole numbers of the question are correct, (1428 Oxidizer holes and (approximately) 1404 Fuel (RP1) holes) the explanation from the heroicrelics page may be true.

The "self-impinging stream pattern" was chosen, see right image, not the "doublet impinging stream pattern", see left image.

The like-on-unlike pattern was rejected and the like-on-like pattern was used.

So a pair of fuel orifices were alternated with a pair of oxidizer orifices. To allow good mixing the numbers of each kind of pairs should be equal or at least very close.

The different numbers may be from different injector design versions. We need to know the numbers for the flight ready injector.