Reading through several old reports, I have come across studies conducted by MSFC on improved Saturn V designs with greater payload capacity, and with uprated engines. As a result of increasing launch vehicle propellant masses, the first stage 'MS-IC' engines had to produce more thrust to lift the upper stages efficiently. Rocketdyne's F-1 would have continued on as UF-1 and F-1A variants.
Marshall reports from 1965 make reference to the F-1 qualification engine, which was rate down at a peak sea level thrust of 1,522,000 pounds force. The UF-1 ('Uprated F-1') was intended to serve as an interim model that would generate higher thrust levels but not require intensive redevelopment required for substantial boosting. As such, the UF-1 would settle at a thrust of 1,650,000 pounds force. The F-1A would make further improvements not including completely new component design to achieve 1,800,000 pounds force.
The UF-1 is the model that interests me, because there isn't much writing on it elsewhere. MSFC researchers intended to increase its thrust, but also stated that the standard 1,522k F-1 thrust was limited by the horsepower of its '35 inch turbopump.' To update to 1,650k the UF-1 would feature a new 30 inch turbine and improved pump inducers to support it, and also a strengthened gas generator operating at a lower lox/fuel ratio. The 30 inch turbine would then limit the thrust because of its critical turbine speed. However, the F-1A would surpass this with the same 30 inch model by adding new, increased diameter impellers (as well as larger gas generators and exhaust manifolds).
But here's where it gets interesting: I have also been reading 'Stages to Saturn' by Roger E. Bilstein, in which the author writes of a test run of an early completed thrust chamber at Edwards AFB. On April 6th 1961, 'the thrust of the prototype chamber peaked at 7,295,000 newtons (1,640,000 pounds).' If originally developed to be limited to 1,522k pounds force by turbine horsepower constraints, how could this engine generate so much more thrust without the 1965-listed improvements to the turbine and GG?
This reminds me of various other articles listing F-1 thrusts beyond 1,522k pounds throughout Saturn V operation: from 1,530k on Apollo 11 to 1,565k on Apollo 15 and 1,580k on Skylab. But 1640k?
So here are the questions: - How did the old turbine allow for 1,640klbf thrust? - Would chamber pressure or specific impulse be increased? - Could Saturn V have been propelled with this thrust level?
I want to know if 1,640k could be sustained...