F-1 Restart?

[AS_501]

As we know, no Saturn V F-1 flight engine was ever shut down prior to Launch Commit.  But what if this had happened?  Would it have been a simple matter of recycling the launch 24 hours, replacing the expended propellants and restarting the engines?  For the purposes of discussion, suppose the center F-1 engine was inadvertently shut down by the Sequencer several seconds after ignition sequence start (not triggered by an engine fault).  During the recycle, maybe all that would have been required is purging of some residual RP-1 from the engines.  Or would some expendable materials or components have to be replaced inside the engine?

PS:  It just occurred to me that the Apollo-era engineers did not have the flexible borescopes of today to inspect F-1 and other engines of the day.
Thanks!

[russianhalo117]

As we know, no Saturn V F-1 flight engine was ever shut down prior to Launch Commit.  But what if this had happened?  Would it have been a simple matter of recycling the launch 24 hours, replacing the expended propellants and restarting the engines?  For the purposes of discussion, suppose the center F-1 engine was inadvertently shut down by the Sequencer several seconds after ignition sequence start (not triggered by an engine fault).  During the recycle, maybe all that would have been required is purging of some residual RP-1 from the engines.  Or would some expendable materials or components have to be replaced inside the engine?

PS:  It just occurred to me that the Apollo-era engineers did not have the flexible borescopes of today to inspect F-1 and other engines of the day.
Thanks!

A simplified answer: replace single use hypergolic start cartridge with single use membranes and replenish (holds TEA-TEB or equivalent) for fuel side, replacement of the 4 pyrotechnic igniters (for MCC and GG start cartridge (one primary and one backup)).

https://home.kpn.nl/panhu001/Saturn_V/Saturn_V_info/F-1_engine/F-1_engine_ignition_sequence.html

Later F-1 upgrade version would have replaced this method with newer technology but was cancelled and never flew.

[edzieba]

PS:  It just occurred to me that the Apollo-era engineers did not have the flexible borescopes of today to inspect F-1 and other engines of the day.

Saturn V literally flew fibre-optic camera systems, so it's not unreasonable that some bright spark would have the ides to go and borrow a fibre bundle to poke into dark recesses if required.

[laszlo]

Sorry for the lack of references, but I don't remember where I read this and I don't have time right now to chase it down. But...

If the engines had actually ignited before the shutdown, they would have needed the soot cleaned out.

Also, the engines and plumbing were packed with a chemical (ethylene glycol?) to dilute the fuel at startup. Otherwise, the ignition pressure ramp-up rate would have been more than the engine could have handled. As the dilutant was consumed, the pressure increased smoothly until it reached steady-state.

As far as lack of flexible borescopes, the engineers of the day simply designed hardware to be inspected by a non-flexible one.

The Saturn's engines all had significant firing times on them before they launched their Apollo flights. The manufacturing and integration processes required this, so the recycle after firing process is documented somewhere out there.

[alain1951]

"If the engines had actually ignited before the shutdown, they would have needed the soot cleaned out."

Didn't they burn Hydrolox? Not much soot in those.

[laszlo]

F1's were kerolox. The soot was removed with TCE (trichloroethylene).

More info here https://www.enginehistory.org/Rockets/RPE08.11/RPE08.13.shtml

Attached image shows pipes packed with ethylene glycol.

So it wasn't that hard to find

[Hog]

F1's were kerolox. The soot was removed with TCE (trichloroethylene).

More info here

Attached image shows pipes packed with ethylene glycol.

So it wasn't that hard to find

What "wasn't so hard to find"?

[laszlo]

F1's were kerolox. The soot was removed with TCE (trichloroethylene).

More info here

Attached image shows pipes packed with ethylene glycol.

So it wasn't that hard to find

What "wasn't so hard to find"?

The references for the assertions I made. I said in my first response that I didn't have time to look them up, but couldn't let it go and managed to find and post them as a second message in under 15 minutes after that. I overestimated the amount of work and was remarking on that.

[Hog]

F1's were kerolox. The soot was removed with TCE (trichloroethylene).

More info here

Attached image shows pipes packed with ethylene glycol.

So it wasn't that hard to find

What "wasn't so hard to find"?

The references for the assertions I made. I said in my first response that I didn't have time to look them up, but couldn't let it go and managed to find and post them as a second message in under 15 minutes after that. I overestimated the amount of work and was remarking on that.

Thank you, I appreciate you taking the time to a) do your research and for b) explaining what you meant to an occasional thick-head like myself.
xxxxxxx

Restarting the FRSC hydrolox RS25 required very strict "dry out" protocols.  Was moisture a concern for F-1 kerolox restartability?

[laszlo]

Restarting the FRSC hydrolox RS25 required very strict "dry out" protocols.  Was moisture a concern for F-1 kerolox restartability?

I don't know, I haven't seen anything suggesting that. Hydrolox is much colder and has only water as its combustion product. Kerolox has its fuel at ambient temperature and includes large amounts of CO₂ in its combustion products. Maybe the differences meant that water was not such a problem in the F1s.

Or, it could be that the TCE flush to remove the soot dried out the engine, TCE being a drying agent in some cases. The fact that they flushed the LOX dome with TCE before each firing indicates to me that this might be the case.

[Proponent]

Restarting the FRSC hydrolox RS25 required very strict "dry out" protocols.  Was moisture a concern for F-1 kerolox restartability?

I don't know, I haven't seen anything suggesting that. Hydrolox is much colder and has only water as its combustion product.

Hydrolox engines burn a rich mixture, i.e., they run with a considerable excess of hydrogen.  In the combustion chamber, there will be OH radicals and other species besides H₂O present.