The S-IB stage

The Saturn I S-I stages for the SA-8 and SA-10 mission in final assembly phase. The Saturn I was the predecessor of the Saturn IB. Altough the Saturn IB was an improved version, the assembly sequence was much the same. First a central tank section was mounted between the tail section and and a socalled spiderbeam assembly. Next eight other tanks were mounted around the central tank. The tail section contained the thrust structure against which eight H-1 thrust engines were mounted.

credit to NASA

General information

The S-IB stage was developed to improve rocket technology with the primary aim to build moon-bound launch vehicles and to increase the launch capacity for heavy payloads. Clustering of thrust engines was one of the most important research issues. For it was clear that the necessary thrust at the first stage of a moon-bound launch vehicle (which would undoubtedly be a very heavy vehicle) could only be obtained by a cluster of thrust engines. The designers choose to use components with a proven record of reliability as much as possible to qualify that concept. The already available H-1 engine was chosen to be used in a cluster of eight engines which would deliver a total thrust of about 700 Tons. Instead of designing new propellant tank structures for the S-IB, it was decided to use a cluster of eight Redstone rocket bodies and one Jupiter rocket body: the somewhat larger Jupiter in the centre enclosed by a chain of eight Redstones.

S-IB stage main parts

From bottom up:
  1. The eight H-1 engines
  2. The aft skirt
  3. The thrust structure (which forms the tail unit together with the aft skirt)
  4. The four fuel tanks
  5. The five liquid oxygen tanks
  6. The forward skirt


  1. Height      : 27.8 meter
    Diameter  : 6.59 meter (excluding fins)
    Mass empty stage           : 38.4 Ton
    Mass of propellants        : 412 Ton
    Mass of loaded stage      : 452.8 Ton
    Amount of fuel:
    Liquid Oxygen : 286 Ton, 251 500 litre (Mass dens. LOx: 1.137 kg/ltr)
    Kerosene RP1 : 126 Ton, 157 700 litre (Mass dens. RP1: 0.799 kg/ltr).
  2. Typical flight profile
    Typical flight parameters at the moment of S-IB stage burn-out:
    • Altitude : 61 km
    • Downrange distance : 59.5 km
    • Velocity : 2 320 m/sec (8 350 km/hr; 7.8 Mach)
    • Time of operation : 150 sec.
  3. H-1 engines:
    H-1 engine thrust : 91 Ton
    It took the eight H-1 engines xx seconds to build up 800 Tons of thrust from the moment of ignition.
    Height of H-1 engine      : 2.68 meter
    Diameter of H-1 engine  : 1.49 meter
    Mass of H-1 engine        : 0.95 Ton
    (Combustion pressure inside an H-1 chamber : 40 bar
    Combustion chamber diameter probably around 0.57 meter.)
    Fuel consumption rate per H-1 engine : 0.38 Ton/sec.
    Specific Impulse at ground level : 261 sec.
  4. Manufacturer of the H-1 engines: North American Aviation, Rocketdyne division
    Manufacturer of the S-IB stage: Chrysler Corporation

This picture shows the flight path of the SA-205 (Apollo 7) during ascent. The S-IB performed its task in only the first 2½ minutes of the flight and was then disposed of. After a nearly 7 minutes ballistic flight, the S-IB stage plunged into the Atlantic Ocean about 490 km off the east coast of Florida.

Skylab 2 ground track during ascent

This picture shows the ground track of the SA-206 (Skylab 2) during ascent. The S-IB performed its task in only the first 2½ minutes of the flight and was then disposed of. The S-IB stage plunged into the Atlantic Ocean about 500 km off the east coast of Florida.

Plan View S-IB stage Forward section, Looking down

Plan View S-IB stage Forward section, Looking down
The Spiderbeam assembly is shown separately

The S-IB stage

The five oxygen tanks, four fuel tanks, the forward skirt and the antenna panels

Plan View S-IB stage Aft section, Looking up

Fins, thrust structure and the eight H-1 eingines

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Copyright 2005 by   Sander Panhuyzen
Comments and questions are welcome. All pictures and drawings contained on and through these pages are the author's, unless otherwise noted. No unauthorized reproduction without permission.