General information
The S-IC stage had a relatively conservative design: separate LOx and fuel tanks connected with an intertank and a solid crossbeamlike thrust structure at the base. A cluster of five gigantic F-1 engines were used for thrust. The concept of clustering engines to obtain higher thrust had been proven by the Saturn IB with its 8 thrust engines in the first stage. The development of the Saturn V could be built on that experience.
The construction of the S-IC stage however was a real challenge because of its sheer size like welding of large tank structures with very tight tolerances.
The F-1 engine
The gigantic F-1 engine used a conventional mixture of RP-1 (kerosene) and liquid oxygen. During the development of this engine designers initially assumed that they basically had to scale up already proven designs. But the development appeared to be not that straightforward. Early firing tests on the F-1 engine revealed harmful combustion instabilities inside the combustion chamber, which turned out to be a major problem, difficult to tackle and threatened to jeopardize the Apollo Program. Lot of research went into the redesign of the F-1 engine propellant injector. The new designed injector plate with its around 5000 orifices through which the RP-1 and the liquid oxygen was pumped into the combustion chamber with a high pressure turbo pump, resulted in an improved spray pattern of the propellants and gave the F-1 engine excellent damping qualities with respect to combustion instabilities.
Skylab
This 13th S-IC stage was the last one which had been comissioned, the remaining two stages (S-IC-14 and S-IC-15) were stocked and ended up as musuem curiosities eventually. The S-IC-13 was used to bring the 75 metric Tons heavy Skylab, America's first space station, into a 443 high nearly circulair orbit. The flight azimuth was 47 degrees to obtain an orbital inclination of 50 degrees. With such an inclination an 80% global coverage of Skylab could be achieved. During the Apollo missions, the flight azimuth was always kept at about 72 degrees which resulted in an orbital inlination of 29 degrees. The objective was to bring the Apollo spacecraft in the lunar orbital plane, which almost coïncides with the Earth's ecliptic plane (Earth's solar orbital plane).
S-IC stage main parts
From bottom up:
- The five F-1 engines
- The thrust structure
- The fuel tank
- The intertank
- The liquid oxygen tank
- The forward skirt
Characteristics
- Height : 41.40 meter
Diameter : 9.90 meter (excluding fins)
Mass empty stage : 130.64 Ton
Mass of propellants : 2151.03 Ton
Mass of loaded stage : 2281.67 Ton
Amount of fuel:
Liquid Oxygen : 1499.82 Ton, 1 318 583 liter (Mass dens. LOx: 1.137 kg/ltr)
Kerosene RP1 : 651.21 Ton, 815 089 liter (Mass dens. RP1: 0.799 kg/ltr).
- Typical flight profile
Typical flight parameters at the moment of S-IC stage burn-out:
- Altitude : 87 km
- Downrange distance : 89 km
- Velocity : 2 543 m/sec (9 153 km/hr; 7.8 Mach)
- Time of operation : 160 sec.
- F-1 engines:
F-1 engine thrust : 690 Tons (metric)
It took the five F-1 engines 8 seconds to build up 3450 Tons (metric) of thrust from the moment of ignition.
Height of F-1 engine : 5.64 meter
Diameter of F-1 engine : 3.72 meter
Mass of F-1 engine : 8.4 Ton
Combustion pressure inside an F-1 chamber : 77 bar
Combustion chamber diameter probably around 1 meter.
Fuel consumption rate per F-1 engine : 2.671 Ton/sec.
Specific Impulse at ground level : 280 sec.
- Manufacturer of the F-1 engines: North American Aviation, Rocketdyne division
Manufacturer of the S-IC stage: Boeing Aircraft Company
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