Really Stupid Question

[Dfthu]

Ok, this may be a really stupid question but I was wondering. What if they put a F-1 engine on the second stage of the Saturn V? What would happen if that happened.?

[A Fuzzy Velociraptor]

The engine would break and the rocket would either fall down hit the ground and explode or have to be blown up by launch abort.

The F1 engine is a LOX/RP-1 engine. The SII (second stage of saturn V) used LOX/LH2. LH2 behaves very differently from RP1 in temperature, density, mass flow rate etc. While there are some engines that a fuel or oxidizer can be substituted RP-1 switching with LH2 is almost certainly not one of those cases.

[Bill Phil]

The Titan 1's engine was capable of propellant switching, although it might've been a certain unique variant.

Nothing would happen, really.

[DerekL1963]

15 minutes ago, Dfthu said:

Ok, this may be a really stupid question but I was wondering. What if they put a F-1 engine on the second stage of the Saturn V? What would happen if that happened.?

It wouldn't have been nearly as efficient, as the F-1 was optimized for lower altitudes while the J-2 was designed for vacuum operations.   (And the F-1 wasn't designed for in flight start.)

[Exploro]

38 minutes ago, Bill Phil said:

The Titan 1's engine was capable of propellant switching, although it might've been a certain unique variant.

Nothing would happen, really.

Not entirely accurate. True both Titan I and Titan II used the same engine family. However the LR-87 had to be modified accept the hypergolics which fueled the Titan II (The -5 model to be precise). It would be impossible to take and -3 model engine from a Titan I and mount it to a Titan II.

[Bill Phil]

7 minutes ago, Exploro said:

Not entirely accurate. True both Titan I and Titan II used the same engine family. However the LR-87 had to be modified accept the hypergolics which fueled the Titan II (The -5 model to be precise). It would be impossible to take and -3 model engine from a Titan I and mount it to a Titan II.

http://www.astronautix.com/engines/lr87lh2.htm

Could even go to hydrogen. But with modifications.

[Exploro]

2 minutes ago, Bill Phil said:

http://www.astronautix.com/engines/lr87lh2.htm

Could even go to hydrogen. But with modifications.

Now I understand.