TheSaturn IB^[a] (also known as theuprated Saturn I) was an Americanlaunch vehicle commissioned by theNational Aeronautics and Space Administration (NASA) for theApollo program. It uprated theSaturn I by replacing theS-IV second stage (90,000-pound-force (400,000 N), 43,380,000 lb-sec total impulse), with theS-IVB (200,000-pound-force (890,000 N), 96,000,000 lb-sec total impulse). TheS-IB first stage also increased theS-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'slow 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-fueledApollo command and service module (CSM) or a fully fueledApollo Lunar Module (LM), before the largerSaturn 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), andLunar Module (Apollo 5)
Function	Apollo spacecraft development; S-IVB stage development in support ofSaturn V; Skylab crew launcher
Manufacturer	Chrysler (S-IB) Douglas (S-IVB)
Country of origin	United States
Size
Height	141.6 ft (43.2 m) without payload[1]
Diameter	21.67 ft (6.61 m)[1]
Mass	1,300,220 lb (589,770 kg) without payload[2]
Stages	2
Capacity
Payload toLEO
Altitude	87.5 nmi (162.1 km; 100.7 mi)
Mass	21,000 kg (46,000 lb)[3]
Launch history
Status	Retired
Launch sites	Cape Canaveral,LC-34 andLC-37 Kennedy,LC-39B
Total launches	9
Success(es)	9
First flight	February 26, 1966 (1966-02-26)
Last flight	July 15, 1975 (1975-07-15)
Carries passengers or cargo	Apollo CSM, UncrewedApollo LM
First stage –S-IB
Height	24.44 m (80.17 ft)
Diameter	6.53 m (21.42 ft)
Empty mass	42,000 kg (92,500 lb)
Gross mass	441,000 kg (973,000 lb)
Propellant mass	399,400 kg (880,500 lb)
Powered by	8 ×H-1
Maximum thrust	7,100 kN (1,600,000 lbf)
Specific impulse	272 s (2.67 km/s)
Burn time	150 seconds
Propellant	LOX /RP-1
Second stage –S-IVB
Height	17.81 m (58.42 ft)
Diameter	6.53 m (21.42 ft)
Empty mass	10,600 kg (23,400 lb)
Gross mass	114,300 kg (251,900 lb)
Propellant mass	103,600 kg (228,500 lb)
Powered by	1 ×J-2
Maximum thrust	890 kN (200,000 lbf)
Specific impulse	420 s (4.1 km/s)
Burn time	480 seconds
Propellant	LOX /LH2
[edit on Wikidata]

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 fortrans-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 asApollo 1, later flown asApollo 7). It also launched one orbital mission,AS-203, without a payload so the S-IVB would have residualliquid 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 inweightlessness.

In 1973, the year after the Apollo lunar program ended, three Apollo CSM/Saturn IBs ferried crews to theSkylab space station. In 1975, one last Apollo/Saturn IB launched the Apollo portion of the joint US-USSRApollo–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 versatileTitan III family and also theSpace Shuttle.

In 1959, NASA'sSilverstein Committee issued recommendations to develop theSaturn class launch vehicles, growing from theC-1. When theApollo 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 thecommand module with a smaller propulsion module attached, as thecommand 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 theC-5 for the lunar landing mission, and decided to develop another launch vehicle by upgrading the Saturn I, replacing itsS-IV second stage with theS-IVB, which would also be modified for use as the Saturn V third stage. TheS-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 thelunar 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 threeSkylab missions, the first-stage engine had been upgraded further, raising the payload capability to 46,000 pounds (21,000 kg).

The S-IB stage was built by theChrysler corporation at theMichoud Assembly Facility,New Orleans.^[5] It was powered by eightRocketdyne H-1 rocket engines burningRP-1 fuel withliquid oxygen (LOX). EightRedstone tanks (four holding fuel and four holding LOX) were clustered around aJupiter rocket LOX tank, which earned the rocket the nickname "Cluster's Last Stand".^[6] The four outboard engines were mounted ongimbals, 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)

Engine

• 8 ×Rocketdyne H-1
  • Thrust: 7,100 kilonewtons (1,600,000 lbf)
  • Burn time: 150 seconds
  • Fuel:LOX /RP-1

The S-IVB was built by theDouglas Aircraft Company atHuntington Beach, California. The S-IVB-200 model was similar to the S-IVB-500 third stage used on theSaturn 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 singleRocketdyne 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)

Engine

• 1 ×Rocketdyne J-2
  • Thrust: 890 kilonewtons (200,000 lbf)
  • Burn time: ~420 seconds
  • Fuel:LOX /LH₂

IBM built the instrument unit at the Space Systems Center inHuntsville, 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 itsstate 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 redundantrange 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.

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 theCommand and Service Module in a 150-by-222-kilometer (81-by-120-nautical-mile)elliptical orbit which was co-planar with theSkylab one. The SPS engine of the Command and Service Module was used at orbit apogee to achieve aHohmann transfer to theSkylab orbit at 431 kilometers (233 nautical miles).^[8]

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

The Saturn IB was used between 1973 and 1975 for three crewedSkylab flights, and oneApollo-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 utilizedKennedy 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]

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

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

• SA-209 is on display at theKennedy 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.
• TheSA-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 theU.S. Space & Rocket Center in Huntsville, Alabama. TheSA-211 first stage was on display with a mockupS-IVB stage stacked in a launch-ready condition at the Alabama Welcome Center onInterstate 65 inArdmore, Alabama, since July 1979.34°57′16″N86°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 wasUS$55,000,000 (equivalent to $413,000,000 in 2024).^[13]

• Comparison of orbital launchers families
• Comparison of orbital launch systems

• http://www.apollosaturn.com/
• http://www.spaceline.org/rocketsum/saturn-Ib.html
• NASA Marshall Spaceflight Center,"Skylab Saturn IB Flight Manual"(PDF). (19.8 MB), 30 September 1972
• "Saturn launch vehicles"(PDF). Archived fromthe original(PDF) on 2005-04-16. (61.2 MB)