Saturn IB


The Saturn IB[a](also known as the uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (90,000-pound-force (400,000 N), 43,380,000 lb-sec total impulse), with the S-IVB (200,000-pound-force (890,000 N), 96,000,000 lb-sec total impulse). The S-IB first stage also increased the S-I baseline's thrust from 1,500,000 pounds-force (6,700,000 N) to 1,600,000 pounds-force (7,100,000 N) and propellant load by 3.1%. This increased the Saturn I's low Earth orbit payload capability from 20,000 pounds (9,100 kg) to 46,000 pounds (21,000 kg), enough for early flight tests of a half-fueled Apollo command and service module (CSM) or a fully fueled Apollo Lunar Module (LM), before the larger Saturn V needed for lunar flight was ready.

Saturn IB
Three launch configurations of the Apollo Saturn IB rocket: no spacecraft (AS-203), command and service module (AS-202); and Lunar Module (Apollo 5)
FunctionApollo spacecraft development;
S-IVB stage development in support of Saturn V;
Skylab crew launcher
ManufacturerChrysler (S-IB)
Douglas (S-IVB)
Country of originUnited States
Height141.6 ft (43.2 m)
without payload[1]
Diameter21.67 ft (6.61 m)[1]
Mass1,300,220 lb (589,770 kg)
without payload[2]
Payload to LEO
Altitude87.5 nmi (162.1 km; 100.7 mi)
Mass21,000 kg (46,000 lb)[3]
Launch history
Launch sitesCape Canaveral, LC-34 and LC-37
Kennedy Space Center, LC-39B
Total launches9
First flightFebruary 26, 1966 (1966-02-26)
Last flightJuly 15, 1975 (1975-07-15)
Type of passengers/cargoApollo CSM,
Uncrewed Apollo LM
First stage – S-IB
Height24.44 m (80.17 ft)
Diameter6.53 m (21.42 ft)
Empty mass42,000 kg (92,500 lb)
Gross mass441,000 kg (973,000 lb)
Propellant mass399,400 kg (880,500 lb)
Powered by8 × H-1
Maximum thrust7,100 kN (1,600,000 lbf)
Specific impulse272 s (2.67 km/s)
Burn time150 seconds
PropellantLOX / RP-1
Second stage – S-IVB
Height17.81 m (58.42 ft)
Diameter6.53 m (21.42 ft)
Empty mass10,600 kg (23,400 lb)
Gross mass114,300 kg (251,900 lb)
Propellant mass103,600 kg (228,500 lb)
Powered by1 × J-2
Maximum thrust890 kN (200,000 lbf)
Specific impulse420 s (4.1 km/s)
Burn time480 seconds
PropellantLOX / LH2

By sharing the S-IVB upper stage, the Saturn IB and Saturn V provided a common interface to the Apollo spacecraft. The only major difference was that the S-IVB on the Saturn V burned only part of its propellant to achieve Earth orbit, so it could be restarted for trans-lunar injection. The S-IVB on the Saturn IB needed all of its propellant to achieve Earth orbit.

The Saturn IB launched two uncrewed CSM suborbital flights to a height of 162 km, one uncrewed LM orbital flight, and the first crewed CSM orbital mission (first planned as Apollo 1, later flown as Apollo 7). It also launched one orbital mission, AS-203, without a payload so the S-IVB would have residual liquid hydrogen fuel. This mission supported the design of the restartable version of the S-IVB used in the Saturn V, by observing the behavior of the liquid hydrogen in weightlessness.

In 1973, the year after the Apollo lunar program ended, three Apollo CSM/Saturn IBs ferried crews to the Skylab space station. In 1975, one last Apollo/Saturn IB launched the Apollo portion of the joint US-USSR Apollo–Soyuz Test Project (ASTP). A backup Apollo CSM/Saturn IB was assembled and made ready for a Skylab rescue mission, but never flown.

The remaining Saturn IBs in NASA's inventory were scrapped after the ASTP mission, as no use could be found for them and all heavy lift needs of the US space program could be serviced by the cheaper and more versatile Titan III family and also the Space Shuttle.



In 1959, NASA's Silverstein Committee issued recommendations to develop the Saturn class launch vehicles, growing from the C-1. When the Apollo program was started in 1961 with the goal of landing men on the Moon, NASA chose the Saturn I for Earth orbital test missions. However, the Saturn I's payload limit of 20,000 pounds (9,100 kg) to 162 km would allow testing of only the command module with a smaller propulsion module attached, as the command and service module would have a dry weight of at least 26,300 pounds (11,900 kg), in addition to service propulsion and reaction control fuel. In July 1962, NASA announced selection of the C-5 for the lunar landing mission, and decided to develop another launch vehicle by upgrading the Saturn I, replacing its S-IV second stage with the S-IVB, which would also be modified for use as the Saturn V third stage. The S-I first stage would also be upgraded to the S-IB by improving the thrust of its engines and removing some weight. The new Saturn IB, with a payload capability of at least 35,000 pounds (16,000 kg),[4] would replace the Saturn I for Earth orbit testing, allowing the command and service module to be flown with a partial fuel load. It would also allow launching the 32,000-pound (15,000 kg) lunar excursion module separately for uncrewed and crewed Earth orbital testing, before the Saturn V was ready to be flown. It would also give early development to the third stage.[2]

On May 12, 1966, NASA announced the vehicle would be called the "uprated Saturn I", at the same time the "lunar excursion module" was renamed the lunar module. However, the "uprated Saturn I" terminology was reverted to Saturn IB on December 2, 1967.[2]

By the time it was developed, the Saturn IB payload capability had increased to 41,000 pounds (19,000 kg).[2] By 1973, when it was used to launch three Skylab missions, the first-stage engine had been upgraded further, raising the payload capability to 46,000 pounds (21,000 kg).



Launch vehicle

Parameter[1] S-IB (1st stage) S-IVB (2nd stage) Instrument unit
Height 24.44 m (80.17 ft) 17.81 m (58.42 ft) 0.91 m (3 ft)
Diameter 6.53 m (21.42 ft) 6.61 m (21.67 ft) 6.61 m (21.67 ft)
Structural mass 42,000 kg (92,500 lb) 10,600 kg (23,400 lb) 2,000 kg (4,400 lb)
Propellant LOX / RP-1 LOX / LH2
Propellant mass 399,400 kg (880,500 lb) 103,600 kg (228,500 lb)
Engines 8 × H-1 1 × J-2
Thrust 7,100 kN (1,600,000 lbf) sea level 890 kN (200,000 lbf) vacuum
Burn duration 150 seconds 480 seconds
Specific impulse 272 s (2.67 km/s) sea level 420 s (4.1 km/s) vacuum
Contractor Chrysler Douglas IBM

Payload configurations

Parameter Command and service module Apollo 5 AS-203
Launch Escape System mass 4,200 kg (9,200 lb)
Apollo command and service module mass 16,500 to 20,900 kg (36,400 to 46,000 lb)
Apollo Lunar Module mass 14,360 kg (31,650 lb)
Spacecraft–LM adapter mass 1,840 kg (4,050 lb) 1,840 kg (4,050 lb)
Nose cone height 2.5 m (8.3 ft) 8.4 m (27.7 ft)
Payload height 24.9 m (81.8 ft) 11.1 m (36.3 ft)
Total space vehicle height 68.1 m (223.4 ft) 54.2 m (177.9 ft) 51.6 m (169.4 ft)

S-IB first stage

Diagram of the S-IB first stage of the Saturn IB rocket

The S-IB stage was built by the Chrysler corporation at the Michoud Assembly Facility, New Orleans.[5] It was powered by eight Rocketdyne H-1 rocket engines burning RP-1 fuel with liquid oxygen (LOX). Eight Redstone tanks (four holding fuel and four holding LOX) were clustered around a Jupiter rocket LOX tank, which earned the rocket the nickname "Cluster's Last Stand".[6] The four outboard engines were mounted on gimbals, allowing them to be steered to control the rocket. Eight fins surrounding the base thrust structure provided aerodynamic stability and control.

Data from:[7]

General characteristics

  • Length: 24.44 metres (80.17 ft)
  • Diameter: 6.53 metres (21.42 ft)
  • Wingspan: 12.02 metres (39.42 ft)


S-IVB second stage

Diagram of the S-IVB second stage of the Saturn IB

The S-IVB was built by the Douglas Aircraft Company at Huntington Beach, California. The S-IVB-200 model was similar to the S-IVB-500 third stage used on the Saturn V, with the exception of the interstage adapter, smaller auxiliary propulsion control modules, and lack of on-orbit engine restart capability. It was powered by a single Rocketdyne J-2 engine. The fuel and oxidizer tanks shared a common bulkhead, which saved about ten tons of weight and reduced vehicle length over ten feet.

General characteristics

  • Length: 17.81 metres (58.42 ft)
  • Diameter: 6.61 metres (21.67 ft)


Instrument unit

The instrument unit, which controlled the Saturn IB and Saturn V

IBM built the instrument unit at the Space Systems Center in Huntsville, Alabama. Located at the top of the S-IVB stage, it consisted of a Launch Vehicle Digital Computer (LVDC), an inertial platform, accelerometers, a tracking, telemetry and command system and associated environmental controls. It controlled the entire rocket from just before liftoff until battery depletion. Like other rocket guidance systems, it maintained its state vector (position and velocity estimates) by integrating accelerometer measurements, sent firing and steering commands to the main engines and auxiliary thrusters, and fired the appropriate ordnance and solid rocket motors during staging and payload separation events.

As with other rockets, a completely independent and redundant range safety system could be invoked by ground radio command to terminate thrust and to destroy the vehicle should it malfunction and threaten people or property on the ground. In the Saturn IB and V, the range safety system was permanently disabled by ground command after safely reaching orbit. This was done to ensure that the S-IVB stage would not inadvertently rupture and create a cloud of debris in orbit that could endanger the crew of the Apollo CSM.

Launch sequence events

Launch event[8] Time (s) Altitude (km) Speed (m/s)
Guidance ref release -5.0 0.09 0
First motion 0.0 0.09 0
Mach 1 58.9 7.4 183
Max dynamic pressure 73.6 12.4 328
Freeze tilt 130.5 48.2 1587
Inboard engine cutoff 137.6 54.8 1845
Outboard engine cutoff 140.6 57.6 1903
S-IB / S-IVB separation 142.0 59.0 1905
S-IVB ignition 143.4 59.9 1900
Ullage case jettison 154.0 69.7 1914
Launch escape tower jettison 165.6 79.5 1960
Iterative guidance mode initiation 171.0 83.7 1984
Engine mixture ratio shift 469.5 164.8 5064
Guidance C/O signal 581.9 158.4 7419
Orbit insertion 591.9 158.5 7426

Acceleration of the Saturn IB increased from 1.24 G at liftoff to a maximum of 4.35 G at the end of the S-IB stage burn, and increased again from 0 G to 2.85 G from stage separation to the end of the S-IVB burn.[8]

AS-206, 207, and 208 inserted the Command and Service Module in a 150-by-222-kilometer (81-by-120-nautical-mile) elliptical orbit which was co-planar with the Skylab one. The SPS engine of the Command and Service Module was used at orbit apogee to achieve a Hohmann transfer to the Skylab orbit at 431 kilometers (233 nautical miles).[8]

Saturn IB vehicles and launches

Saturn IB mounted on the "milkstool" platform

The first five Saturn IB launches for the Apollo program were made from LC-34 and LC-37, Cape Kennedy Air Force Station.

The Saturn IB was used between 1973 and 1975 for three crewed Skylab flights, and one Apollo-Soyuz Test Project flight. This final production run did not have alternating black and white S-IB stage tanks, or vertical stripes on the S-IVB aft tank skirt, which were present on the earlier vehicles. Since LC-34 and 37 were inactive by then, these launches utilized Kennedy Space Center's LC-39B.[9] Mobile Launcher Platform No. 1 was modified, adding an elevated platform known as the "milkstool" to accommodate the height differential between the Saturn IB and the much larger Saturn V.[9] This enabled alignment of the Launch Umbilical Tower's access arms to accommodate crew access, fueling, and ground electrical connections for the Apollo spacecraft and S-IVB upper stage. The tower's second stage access arms were modified to service the S-IB first stage.[9]

Various mission configurations for the Saturn IB launch vehicle
All Saturn IB launches from AS-201 through ASTP
Mission Spacecraft
mass (kg)
SA-201 AS-201 20,820 February 26, 1966
Uncrewed suborbital test of Block I CSM
(command and service module)
SA-203 AS-203 None July 5, 1966
Uncrewed test of unburned LH2 behavior in orbit
to support S-IVB-500 restart design
SA-202 AS-202 25,810 August 25, 1966
Uncrewed suborbital test of Block I CSM
SA-204 Apollo 1 20,412 Was to be first crewed orbital test of Block I CSM.
Cabin fire on January 27, 1967, killed astronauts and damaged CM during dress rehearsal for planned February 21, 1967 launch
Apollo 5 14,360 January 22, 1968
Uncrewed orbital test of lunar module, used Apollo 1 launch vehicle
SA-205 Apollo 7 16,520 October 11, 1968
Crewed orbital test of Block II CSM
SA-206 Skylab 2 19,979 May 25, 1973
Block II CSM ferried first crew to Skylab orbital workshop
SA-207 Skylab 3 20,121 July 28, 1973
Block II CSM ferried second crew to Skylab orbital workshop
SA-208 AS-208 Standby Skylab 3 rescue CSM-119; not needed
Skylab 4 20,847 November 16, 1973
Block II CSM ferried third crew to Skylab orbital workshop
SA-209 AS-209 Standby Skylab 4 and later Apollo-Soyuz rescue CSM-119.
Not needed, currently on display in the KSC rocket garden
Skylab 5 Planned CSM mission to lift Skylab workshop's orbit
to endure until Space Shuttle ready to fly; cancelled.
SA-210 ASTP 16,780 July 15, 1975
Apollo CSM with special docking adapter module,
rendezvoused with Soyuz 19. Last Saturn IB flight.
SA-211 Unused. First stage was on display at the Alabama Welcome Center on I-65 in Ardmore, Alabama from 1979 to 2023: Now dismantled for disposal.[10]
S-IVB stage rests with Skylab underwater training simulator hardware and is on display outdoors at the U.S. Space and Rocket Center in Huntsville, Alabama.
SA-212 Unused. First stage scrapped.[5]
S-IVB stage converted to Skylab space station.
SA-213 Only first stage built. Unused and scrapped.[5]
SA-214 Only first stage built. Unused and scrapped.[5]

For earlier launches of vehicles in the Saturn I series, see the list in the Saturn I article.

Saturn IB rockets on display

SA-209 on display at KSC

As of 2023 there are two locations where Saturn IB vehicles (or parts thereof) are on display:

  • SA-209 is on display at the Kennedy Space Center Visitor Complex, with the Apollo Facilities Verification Vehicle. Due to severe corrosion, the first stage engines and service module were replaced with fabricated duplicates in 1993–1994.
  • The SA-211 S-IVB stage was mated with the Skylab underwater training docking adapter and Apollo Telescope Mount and is on display in the Rocket Garden of the U.S. Space & Rocket Center in Huntsville, Alabama. The SA-211 first stage was on display with a mockup S-IVB stage stacked in a launch-ready condition at the Alabama Welcome Center on Interstate 65 in Ardmore, Alabama, since July 1979.34°57′16″N 86°53′31″W / 34.954548°N 86.89193°W / 34.954548; -86.89193[11][12] The structural integrity of the display, after four decades of weathering, could not be repaired. Dismantling of the vehicle for disposal began by September 14, 2023.[10]



In 1972, the cost of a Saturn IB including launch was US$55,000,000 (equivalent to $401,000,000 in 2023).[13]

See also



  1. ^ Pronounced "saturn one bee"


  1. ^ a b c Postlaunch report for mission AS-201 (Apollo spacecraft 009) - (PDF), NASA, May 1966, retrieved March 18, 2011
  2. ^ a b c d Wade, Mark. "Saturn IB". Encyclopedia Astronautica. Archived from the original on May 14, 2011. Retrieved March 17, 2011.
  3. ^ Hornung, John (2013). Entering the Race to the Moon: Autobiography of an Apollo Rocket Scientist. Williamsburg, Virginia: Jack Be Nimble Publishing. ISBN 9780983044178.
  4. ^ Benson, Charles D.; Faherty, William Barnaby (1978). "The Apollo-Saturn IB Space Vehicle". Moonport: A History of Apollo Launch Facilities and Operations. NASA. Archived from the original on 24 March 2016. Retrieved 3 February 2016.
  5. ^ a b c d "Saturn IB History". Archived from the original on January 4, 2013. Retrieved 2009-11-01.{{cite web}}: CS1 maint: unfit URL (link)
  6. ^ "Saturn I".
  7. ^ NASA Marshall Spaceflight Center, Skylab Saturn IB Flight Manual (MSFC-MAN-206), 30 September 1972
  8. ^ a b c Skylab Saturn 1B Flight Manual - (PDF), NASA, September 30, 1972, retrieved July 8, 2020
  9. ^ a b c Reynolds, David West (2006). Kennedy Space Center: Gateway to Space. Richmond Hill, Ontario: Firefly Books Ltd. pp. 154–157. ISBN 978-1-55407-039-8.
  10. ^ a b "Historic Alabama welcome center rocket dismantling begins". 14 September 2023. Retrieved 2023-09-20.
  11. ^ Dooling, Dave (May 6, 1979). "Space and Rocket Plans Summer Celebration". The Huntsville Times.
  12. ^ Hughes, Bayne (April 6, 2014). "Iconic rocket due for repair". The Decatur Daily. Retrieved April 8, 2014.
  13. ^ "SP-4221 The Space Shuttle Decision- Chapter 6: Economics and the Shuttle". NASA. Retrieved 2011-01-15.
  • NASA Marshall Spaceflight Center, "Skylab Saturn IB Flight Manual" (PDF). (19.8 MB), 30 September 1972
  • "Saturn launch vehicles" (PDF). Archived from the original (PDF) on 2005-04-16. (61.2 MB)