page_title: Saturn V
section_title: S-II second stage
hierarchical_section_title: Saturn V / Technology / Stages / S-II second stage
caption_attribution_description: English: The S-II stage of the Saturn V rocket is hoisted onto the A-2 test stand in 1967 at the Mississippi Test Facility, now the Stennis Space Center. This was the second stage of the 364-foot tall Moon rocket. The second stage was powered by five J-2 engines.
context_page_description: Saturn V was an American super heavy-lift launch vehicle certified for human-rating used by NASA between 1967 and 1973. It consisted of three stages, each fueled by liquid propellants. It was developed to support the Apollo program for human exploration of the Moon and was later used to launch Skylab, the first American space station.
  The Saturn V was launched 13 times from Kennedy Space Center with no loss of crew or payload. As of 2020, the Saturn V remains the tallest, heaviest, and most powerful rocket ever brought to operational status, and holds records for the heaviest payload launched and largest payload capacity to low Earth orbit of 310,000 lb, which included the third stage and unburned propellant needed to send the Apollo command and service module and Lunar Module to the Moon.
  As the largest production model of the Saturn family of rockets, the Saturn V was designed under the direction of Wernher von Braun at the Marshall Space Flight Center in Huntsville, Alabama, with Boeing, North American Aviation, Douglas Aircraft Company, and IBM as the lead contractors.
  To date, the Saturn V remains the only launch vehicle to carry humans beyond low Earth orbit.
context_section_description: The S-II was built by North American Aviation at Seal Beach, California. Using liquid hydrogen and liquid oxygen, it had five Rocketdyne J-2 engines in a similar arrangement to the S-IC, also using the outer engines for control. The S-II was 81.6 feet (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 Space Shuttle in 1981. The S-II had a dry weight of about 80,000 pounds (36,000 kg); when fully fueled, it weighed 1,060,000 pounds (480,000 kg). The second stage accelerated the Saturn V through the upper atmosphere with 1,100,000 pounds-force (4,900 kN) of thrust in a 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 (52 °C) temperature difference between the two tanks. The use of a common bulkhead saved 7,900 pounds (3.6 t) by both eliminating one bulkhead and reducing the stage's length. Like the S-IC, the S-II was transported from its manufacturing plant to the Cape by sea.
caption: An S-II stage hoisted onto the A-2 test stand at the Mississippi Test Facility
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