S-V
Convair Astronautics received a contract to build the S-V stage for the Saturn I rocket. Engineers designed this third stage to use liquid hydrogen and liquid oxygen as propellants. Two RL-10A-1 engines powered the vehicle during flight. A common bulkhead separated the fuel tanks from the oxidizer tanks inside the structure. This engineering choice reduced weight while maintaining structural integrity for the mission profile. The design aimed to boost lift capacity for U.S. military operations in the early 1960s.
The initial intent behind the S-V was to support U.S. military launches throughout the decade. Convair delivered two stages by February 1961 to meet these demands. One unit flew on SA-1 attached to an inert S-IV section. The second unit served for dynamic testing of the complete Saturn I before its eventual flight. NASA eliminated the requirement for all Saturn I launches to carry the S-V stage in May 1961. They switched to a two-stage version instead, leaving the military needs to other launch vehicles.
Four specific flight missions occurred between 1961 and 1964 using water ballast. Each test flight reached suborbital altitudes rather than entering orbit. The first flight took place on the 27th of October 1961 at 15:06:04 UTC with an apogee of 136.5 km. A second flight followed on the 25th of April 1962 reaching 145 km altitude. The third mission launched the 16th of November 1962 achieving 167 km height. The final flight occurred the 28th of March 1963 peaking at 129 km above Earth.
Scientists released water into space during apogee on select test flights for Project Highwater. This experiment aimed to study the behavior of liquid clouds in the vacuum of space. The SA-2 mission released 86,000 kg of water at its peak altitude. The SA-3 mission also released 86,000 kg of water at a higher point. These releases created artificial clouds that scientists tracked from ground stations. The inert nature of the stage allowed safe disposal of the propellant mass without risk.
NASA eliminated the S-V requirement following the introduction of the Saturn IB rocket. Military needs were fulfilled by other launches using different configurations. All further launches utilized either the Saturn IB or the Saturn V instead. Neither of these newer rockets used the S-V stage as part of their architecture. The four flights between 1961 and 1964 marked the end of active service for this specific configuration. The technology found new life elsewhere rather than continuing within the Saturn program itself.
Modern derivatives of the stage are still flown today on the Atlas V and Vulcan Centaur launch vehicles. A version of this stage was used on the Atlas-LV3C as the Centaur upper stage. This makes it the only Saturn rocket stage currently operating in spaceflight history. The RL-10 engine design continues to power missions decades after the original contract. Engineers have refined the common bulkhead concept for modern heavy lift requirements. The legacy of Convair's work persists through these contemporary launch systems.
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Common questions
What was the purpose of the S-V stage for the Saturn I rocket?
The initial intent behind the S-V was to support U.S. military launches throughout the decade. Engineers designed this third stage to use liquid hydrogen and liquid oxygen as propellants. The design aimed to boost lift capacity for U.S. military operations in the early 1960s.
When did NASA eliminate the requirement for all Saturn I launches to carry the S-V stage?
NASA eliminated the requirement for all Saturn I launches to carry the S-V stage in May 1961. They switched to a two-stage version instead, leaving the military needs to other launch vehicles. Convair delivered two stages by February 1961 to meet these demands before the change.
How many specific flight missions occurred between 1961 and 1964 using water ballast with the S-V stage?
Four specific flight missions occurred between 1961 and 1964 using water ballast. Each test flight reached suborbital altitudes rather than entering orbit. The first flight took place on the 27th of October 1961 at 15:06:04 UTC with an apogee of 136.5 km.
What experiment involved releasing water into space during apogee on select test flights of the S-V stage?
Scientists released water into space during apogee on select test flights for Project Highwater. This experiment aimed to study the behavior of liquid clouds in the vacuum of space. The SA-2 mission released 86,000 kg of water at its peak altitude.
Which modern derivatives of the S-V stage are still flown today on Atlas V and Vulcan Centaur launch vehicles?
Modern derivatives of the stage are still flown today on the Atlas V and Vulcan Centaur launch vehicles. A version of this stage was used on the Atlas-LV3C as the Centaur upper stage. This makes it the only Saturn rocket stage currently operating in spaceflight history.