S-IV
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![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/08/S-IV_rocket_stage.jpg/220px-S-IV_rocket_stage.jpg)
The S-IV was the second stage of the Saturn I, a rocket-powered launch vehicle used by NASA for early flights in the Apollo program.
The S-IV is similar to, but distinct from, the S-IVB stage used on the Saturn IB and Saturn V rockets.
See also
References
NASA (April 1975). "Apollo Program Summary Report, Part 1" (PDF).