S-IV
The S-IV stage carried six RL-10A-3 engines into the sky. Each engine provided 150,000 pounds of thrust. Together they generated a total force of about 900,000 pounds. This cluster powered the second stage of the Saturn I rocket. Douglas Aircraft Company built the structure to hold these engines and fuel tanks. Engineers designed a common bulkhead between the liquid oxygen tank and the liquid hydrogen tank. The forward wall of the LOX tank became the rear wall of the LH2 tank. This shared boundary saved up to 20 percent of structural weight compared to separate tanks. The design reduced mass while maintaining pressure integrity for cryogenic fluids.
Douglas Aircraft Company manufactured the original S-IV stage in California. The company later modified this unit into the distinct S-IVB variant. These modifications created a new stage used on the Saturn IB and Saturn V rockets. Douglas engineers adapted the existing framework to meet changing mission requirements. They retained core propulsion systems but altered structural dimensions. The transition from S-IV to S-IVB marked a significant shift in production focus. This evolution allowed NASA to reuse proven technology for lunar missions. The same factory floor that built early test stages also prepared hardware for Apollo landings.
Liquid hydrogen and liquid oxygen formed the heart of the S-IV engine system. Tanks held these fuels at extremely low temperatures during flight. A single shared bulkhead separated the two substances inside the rocket body. Liquid oxygen filled the upper section while liquid hydrogen occupied the lower section. Engineers needed to prevent heat transfer between the opposing fluids. The common bulkhead acted as an insulating barrier against thermal exchange. This arrangement optimized fuel storage efficiency within limited volume constraints. Cryogenic handling required specialized materials to withstand extreme cold without cracking or leaking. The design ensured stable combustion when engines ignited above Earth's atmosphere.
Mission records from SA-1 through SA-10 document operational history of the upper stage. Launch dates spanned from the 27th of October 1961 to the 30th of July 1965. Each mission tested different aspects of Saturn I performance under real conditions. SA-1 lifted off on the 27th of October 1961 at 15:06:04 UTC. SA-2 followed on the 25th of April 1962 at 14:00:34 UTC. SA-3 launched the 16th of November 1962 at 17:45:02 UTC. SA-4 flew the 28th of March 1963 at 20:11:55 UTC. SA-5 took flight the 29th of January 1964 at 16:25:01 UTC. SA-6 launched the 28th of May 1964 at 17:07:00 UTC. SA-7 departed the 18th of September 1964 at 16:22:43 UTC. SA-9 lifted off the 16th of February 1965 at 14:37:03 UTC. SA-8 flew the 25th of May 1965 at 07:35:01 UTC. SA-10 concluded the series the 30th of July 1965 at 13:00:00 UTC. These ten flights provided critical data for future Apollo program development.
Technical modifications transformed the S-IV into the S-IVB stage. This new variant served as the second stage for both Saturn IB and Saturn V rockets. Engineers expanded tank capacity while retaining core engine architecture. The S-IVB supported heavier payloads destined for lunar orbits. NASA relied on this upgraded system to reach deeper space targets. Douglas Aircraft Company executed these changes during the early 1960s. The transition enabled more ambitious missions beyond Earth orbit. Modifications included structural reinforcement and fuel system adjustments. The resulting design became foundational for human lunar exploration efforts. Without these upgrades, the Apollo program could not have achieved its goals.
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Common questions
What engines did the S-IV stage carry into the sky?
The S-IV stage carried six RL-10A-3 engines. Each engine provided 150,000 pounds of thrust for a total force of about 900,000 pounds.
Who built the structure for the S-IV upper stage?
Douglas Aircraft Company built the structure to hold these engines and fuel tanks. The company manufactured the original S-IV stage in California before modifying it into the S-IVB variant.
When did the first S-IV mission launch take place?
SA-1 lifted off on the 27th of October 1961 at 15:06:04 UTC. This launch marked the beginning of operational history that spanned through the 30th of July 1965.
How many liquid oxygen and liquid hydrogen tanks were in the S-IV design?
Engineers designed a common bulkhead between the liquid oxygen tank and the liquid hydrogen tank. Liquid oxygen filled the upper section while liquid hydrogen occupied the lower section within this shared boundary.
Why was the S-IV modified into the S-IVB variant?
These modifications created a new stage used on the Saturn IB and Saturn V rockets. The transition allowed NASA to reuse proven technology for lunar missions and support heavier payloads destined for lunar orbits.