S-IV
The S-IV was the second stage of the Saturn I rocket used by NASA for early flights in the Apollo program.
The S-IV was manufactured by the Douglas Aircraft Company and later modified by them to the S-IVB, a similar but distinct stage used on the Saturn IB and Saturn V rockets.
The S-IV stage was a large LOX/LH2-fueled rocket stage used for the early test flights of the Saturn I rocket. It formed the second stage of the Saturn I and was powered by a cluster of six RL-10A-3 engines. Each one of the engines supplied of thrust for a total of about. The cryogenic LH2 and LOX tanks were separated by a common bulkhead. The forward bulkhead of the LOX tank formed the aft bulkhead of the LH2 tank. This saved up to 20% of structural weight.
Flight history
| Mission serial number | Launch date | Image | Launch notes |
| SA-1 | October 27, 1961 15:06:04 | ||
| SA-2 | April 25, 1962 14:00:34 | ||
| SA-3 | November 16, 1962 17:45:02 | ||
| SA-4 | March 28, 1963 20:11:55 | ||
| SA-5 | January 29, 1964 16:25:01 | ||
| SA-6 | May 28, 1964 17:07:00 | ||
| SA-7 | September 18, 1964 16:22:43 | ||
| SA-9 | February 16, 1965 14:37:03 | ||
| SA-8 | May 25, 1965 07:35:01 | ||
| SA-10 | July 30, 1965 13:00:00 |