The F-1 was the most powerful single-nozzle engine ever flown and the RD-170 the most powerful multiple-nozzle engine ever flown. Both engines use kerosin and LOX. The NK-33 was a smaller engine using kerosin and LOX too.

                            F-1        RD-170    NK-33
sea level thrust            6.77       7.25      1.51   MN
vacuum thrust               7.77       7.90      1.68   MN
chamber pressure            7          24.5      14.83  MPa
expansion ratio             16:1       36.87:1
turbine power               41         192              MW
specific impulse sea level  263        309       297    s
specific impulse vacuum     304        337       331    s
exhaust speed sea level     2.58       3.03      2.91   km/s
exhaust speed vacuum        2.98       3.30      3.25   km/s
thrust to weight ratio      94:1       82:1      137:1  (vacuum)
mixture ratio               2.27       2.63             O2/RP-1

The sea level performance of the RD-170 and the NK-33 looks much better than the F-1.

Is the much higher chamber pressure responsible for the better sea level performance?

  • 1
    $\begingroup$ Relevant: space.stackexchange.com/q/41337/6944 space.stackexchange.com/q/33953/6944 From the first one "all else being equal, raising p will indeed increase your exhaust velocity and hence your Isp. " $\endgroup$ Feb 21, 2022 at 23:07
  • $\begingroup$ Specific impulse is 1.17x higher hence 1.17 less fuel. Chamber pressure 3.5x, so in theory RD170's only need 3.5/1.77~3x as big of a turbine, but they went with 5x instead. Interesting. $\endgroup$ Feb 22, 2022 at 2:29
  • $\begingroup$ The expansion ratio of the F1 was 16:1 while the one of the RD-170 is 36.9. This means, the F1 was underexpanding 4.37 times at sea level while the RD-170 underexpanding 6.6 times at sea level. Can someone check those numbers for me because they seem odd to me (for optimal performance you don't want to be underexpanding at sea level I guess)... But it could explain why the F1 "gains" more towards vacuum. $\endgroup$
    – TrySCE2AUX
    Feb 22, 2022 at 6:41
  • $\begingroup$ What about thrust to weight and RP-1/LOX ratio? $\endgroup$ Feb 22, 2022 at 11:18
  • $\begingroup$ I know, I meant between engines, but I see you already added to question. $\endgroup$ Feb 22, 2022 at 13:10


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