The Saturn V consisted of three stages—the S-IC first stage, S-II second stage and the S-IVB third stage—and the instrument unit. All three stages used liquid oxygen (LOX) as an oxidizer. The first stage used RP-1 for fuel, while the second and third stages used liquid hydrogen (LH2). The upper stages also used small solid-fueled ullage motors that helped to separate the stages during the launch, and to ensure that the liquid propellants were in a proper position to be drawn into the pumps.
S-IC first stageEditMain article: S-IC
The first stage of Apollo 8 Saturn V being erected in the VAB on February 1, 1968The S-IC was built by The Boeing Company at the Michoud Assembly Facility, New Orleans, where Space Shuttle External Tanks would later be built by Lockheed Martin. Most of its mass of over two thousand metric tonnes at launch was propellant, in this case RP-1 rocket fuel and liquid oxygen oxidizer with a fuel efficiency of just under 5 inches per US gallon (just under 4 cm per liter) overall. It was 42 meters (138 ft) tall and 10 meters (33 ft) in diameter, and provided over 34 meganewtons (7,600,000 lbf) of thrust to get the rocket through the first 67 kilometers (220,000 ft) of ascent. The S-IC stage had a dry weight of about 131 tonnes (289,000 lb) and fully fueled at launch had a total weight of 2,300 tonnes (5,100,000 lb). The initial design included four F-1 engines, which provided just enough force to lift the spacecraft and rocket. A fifth F-1 engine was added in the center of a quincunx to provide additional thrust to accommodate the growing weight of the Apollo payload. That center engine was fixed, while the four outer engines could be hydraulically turned (gimballed) to control the rocket. In flight, the center engine was turned off about 26 seconds earlier than the outboard engines to limit acceleration. During launch, the S-IC fired its engines for 168 seconds (ignition occurred about 7 seconds before liftoff) and at engine cutoff, the vehicle was at an altitude of about 67 kilometers (42 mi), was downrange about 93 kilometers (58 mi), and was moving about 2,300 meters per second (7,500 ft/s).
S-II second stageEdit
Main article: S-IIThe S-II was built by North American Aviation at Seal Beach, California. Using liquid hydrogen and liquid oxygen, it had five J-2 engines in a similar arrangement to the S-IC, also using the outer engines for control. The S-II was 81 feet 7 inches (24.87 m) tall with a diameter of 33 feet (10 m), identical to the S-IC, and thus was the largest cryogenic stage until the launch of the STS. The S-II had a dry weight of about 80,000 pounds (36,000 kg) and fully fueled, weighed 1,060,000 pounds (480,000 kg). The second stage accelerated the Saturn V through the upper atmosphere with 5.1 meganewtons (1,100,000 lbf) of thrust (in vacuum). When loaded, significantly more than 90 percent of the mass of the stage was propellant; however, the ultra-lightweight design had led to two failures in structural testing. Instead of having an intertank structure to separate the two fuel tanks as was done in the S-IC, the S-II used a common bulkhead that was constructed from both the top of the LOX tank and bottom of the LH2 tank. It consisted of two aluminum sheets separated by a honeycomb structure made of phenolic resin. This bulkhead had to insulate against the 126 °F (70 °C) temperature gradient between the two tanks. The use of a common bulkhead saved 7,900 pounds (3.6 t). Like the S-IC, the S-II was transported by sea.
S-IVB third stageEdit
Main article: S-IVBThe S-IVB was built by the Douglas Aircraft Company at Huntington Beach, California. It had one J-2 engine and used the same fuel as the S-II. The S-IVB used a common bulkhead to insulate the two tanks. It was 58 feet 7 inches (17.86 m) tall with a diameter of 21 feet 8 inches (6.604 m) and was also designed with high mass efficiency, though not quite as aggressively as the S-II. The S-IVB had a dry weight of about 23,000 pounds (10,000 kg) and, fully fueled, weighed about 262,000 pounds (119,000 kg).
The S-IVB-500 model used on the Saturn V differed from the S-IVB-200 used as the second stage of the Saturn IB, in that the engine was restartable once per mission. This was necessary as the stage would be used twice during a lunar mission: first in a 2.5 min burn for the orbit insertion after second stage cutoff, and later for the trans-lunar injection (TLI) burn, lasting about 6 min. Two liquid-fueled Auxiliary Propulsion System (APS) units mounted at the aft end of the stage were used for attitude control during the parking orbit and the trans-lunar phases of the mission. The two APSs were also used as ullage engines to settle the propellants in the aft tank engine feed lines prior to the trans-lunar injection burn.
The S-IVB was the only rocket stage of the Saturn V small enough to be transported by plane, in this case the Pregnant Guppy.
Main article: Saturn V Instrument Unit
The Instrument Unit was built by IBM and rode atop the third stage. It was constructed at the Space Systems Center in Huntsville, Alabama. This computer controlled the operations of the rocket from just before liftoff until the S-IVB was discarded. It included guidance and telemetry systems for the rocket. By measuring the acceleration and vehicle attitude, it could calculate the position and velocity of the rocket and correct for any deviations.
In 2092, several of the stages were refurbished and combined into makeshift settler arks with Mars as a destination. While they served their purpose, it also proved that any serious attempt to settle other planets would need specifically designed ships to do so.
For more see the wikipedia article on Saturn V