Saturn V SA-510 (Apollo 15)
Launched 26 July 1971 (NASA)
One Second in the Life of the Rocketdyne F-1 Rocket Engine
by Tom Fey
Published 23 Jun 2021; Revised 3 Feb 2024
Saturn V SA-510 (Apollo 15) Launched 26 July 1971 (NASA) |
 Rocketdyne F-1 Engines Saturn V S-IC NASA Johnson Space Center Houston, Texas, USA (Leijurv via Wikicommons) |
The liquid fueled Rocketdyne F-1 engine, installed in quintiplicate for the mighty Saturn V rocket's S-IC first stage, powered mankind to the Moon in the late 1960s. Generating 1.522 million pounds of thrust, the F-1 remains the most powerful single-chamber engine ever made. Each engine stood 18.5 feet tall and weighed 18,500 lb, as much as a loaded school bus. The F-1 was designed to run for only 163 seconds. If you could slow time and examine what happened during one of those magnificent operational seconds, what would you find?
For this one second, assume it occurs 80 seconds into flight, roughly half way through the S-IC working life, when the Saturn V launch vehicle is traveling at 1,340 mph, 1,970 feet per second, at an altitude of 20 miles, enduring “max Q” or the highest aerodynamic airframe loading of the flight sequence.
In this one second, each of the five individual F-1 engines is generating maximum power of 1.522 million pounds of thrust, 761 tons, sufficient to lift 6.5 fully-loaded Space Shuttle orbiter vehicles, and the equivalent of 5.44 million horsepower. In this one second, the rotor of the dual-function MK-10 centrifugal turbopump, the size of a commercial refrigerator, weighing 2,500 lb, and powered by an impulse gas turbine generating 55,000 horsepower, has spun 91.5 times. In this one second, 413.5 gallons of liquid oxygen at -297 °F, equivalent in volume to a six-horse pole barn filled with pure oxygen at 14.7 psi, and 258 gallons of RP-1 rocket grade kerosene fuel, roughly equivalent to a long-haul semi-trailer tractor's fuel capacity, have been supplied to the injector plate at the top of the engine. Seventy percent, or 181 gallons, of the RP-1 supply traveled through 178 upper primary and 356 lower secondary Inconel steel tubes to cool the rocket nozzle exposed to combustion gasses at 5,800 °F and 1,125 psig pressure. The fuel is also used to lubricate by splash and spray the three main bearings of the turbopump at 200 to 540 psig before entering the injector plate at 1,375 psig. In this one second, from this single engine, 34 million BTUs of energy have been released, enough to raise the temperature of an Olympic sized swimming pool 6.2 °F.
In this one second, the gas generator that supplies the turbopump has consumed 17.5 gallons of RP-1 fuel through a 2 ¼ inch diameter pipe, and 5.1 gallons of oxidizer through a 1 ½ inch diameter pipe to combust and drive the two-stage impulse turbine containing 109 blades in the 33-inch diameter first stage and 119 blades in the 35-inch diameter second stage rotor. It takes 3.2 million BTU per second to generate the 55,000 horsepower, enough power to lift a diesel locomotive 70 feet into the air in one second. The turbine drives the turbopump while exhaust from the turbine passes through a dual-coil heat exchanger to heat helium that pressurizes the headspace of RP-1 fuel tank to 25 psig, and vaporize liquid oxygen to pressurize the LOX tank to 20 psig before the cooled exhaust is further ducted to provide film cooling to the walls of the nozzle extension.
The S-IC stage gas mileage is about 4.5 feet per gallon, accelerating 6.5 million pounds of rocket at liftoff, and losing 29,250 pounds every second.
In this one second, flight control computers referencing 15 gyroscopes have sent signals to the two, 300-pound hydraulic actuators; one for the x-axis, one for-y axis, that move this gimbal-mounted F-1 engine two degrees outboard of center. In concert with three other of the five total F-1 engines, the thrust-absorbing gimbal pivot allows up to five degrees of thrust vector change from center, at a maximum rate of five degrees per second, to make corrections to pitch, roll, and yaw of the rocket.
Once an additional 83 seconds have expired, at an altitude of 42 miles, traveling at 6,160 mph, the S-IC component containing the fuel tanks and five F-1 engines will be shed from the rest of the Saturn V, momentum carrying the booster a further 31 miles in altitude. After apex, the S-IC begins a tail-first descent, followed by disintegration in the thickening atmosphere, impact with the Atlantic Ocean, fragmentation, and submersion to a depth of 14,000 feet roughly 400 miles east of Cape Canaveral. The heaviest lifting is complete; the mission now depends on thrust from the upper stages to succeed.
A simple concept with an incredibly complicated execution that lasted only 2.7 minutes, the Rocketdyne F-1 engine has performed an epic, Herculean feat rewarded with a successful Apollo exit from Mother Earth and a glorious Viking death.
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| Rocketdyne F-1 Engine (Kim McCutcheon) | Rocketdyne F-1 Engine Diagram (NASA) | Sectioned Rocketdyne F-1 Engine MK-10 Turbopump (Tom Fey) |
Selected References
https://www.enginehistory.org/Rockets/RPE08.11/RPE08.11.shtml
https://history.nasa.gov/SP-4206/ch4.htm
https://home.kpn.nl/panhu001/Saturn_V/Saturn_V_info/SatV-Apollo_perform_char.html
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