The first four Saturn I missions were known as block 1. Several of the block-2 missions orbited boilerplate Apollo spacecraft and Pegasus satellites. As it happened, even after the Apollo 1 fire, block one craft were used on the first two Saturn Vs to test out Block 2 hardware (essentially making them block 1.5s). Block 2 missions included an uprated S-I stage and an S-IV second stage. To save money in its development, the Saturn 1 used existing hardware. From NASA's standpoint though, they probably felt that enough stuff could be tested with the block 1 craft to get the early missions out of the way before the block 2 craft were ready. The Saturn Block is a direct field replacement for other connect under pressure systems. Saturn 1 Block 2 SA-5 100.00 Originally designed for the military to launch the Dyna-Soar in 1957, the Saturn program was taken over by NASA in 1960 to test Apollo.

The Saturn Block allows for easy connection/disconnection with residual pressure, with a user-friendly relief system that drains the residual pressure before connection and disconnection, for connection without pressure or effort to reduce injury risk. SA-5 was the first launch of the Block II Saturn I rocket and was part of the Apollo program.In 1963, president John Kennedy identified this launch as the one which would place US lift capability ahead of the Soviets, after being behind for more than six years since Sputnik. Stage 1 Stage 2 Stage 3; Saturn-1 / Block-1 (Saturn-C1) * Saturn-1 / 8 × H-1 (Saturn-4 Dummy) (Centaur Dummy) Performance (kg) LEO LPEO SSO GTO GEO MolO IP; Saturn-1 (Bl. The Block 2 differed in having a live upper stage and fins on its first stage. Block 1 missions flew with an S-I first stage, and dummy upper stages. Saturn-1 / Block-2: Saturn-1 / 8 × H-1: Saturn-4 / 6 × LR-115 (RL10-3S) Performance (kg) LEO LPEO SSO GTO GEO MolO IP; Saturn-1 (Bl. The Block 1 second and third stages had dummy stages. The Saturn 1 was the basic test vehicle that led to the development of the Saturn V that carried men to the Moon for Project Apollo.

The last six Saturn I missions were known as block 2.