A Forgotten Rocket: The Saturn IB

Image credit: NASA.
The Saturn V Moon rocket, the largest, most powerful launcher ever built, commands much attention, but not everyone knows that the giant had smaller, lesser-known relatives, including one that launched men into space. Had the Apollo Applications Program (AAP) gone ahead as planned in mid-1966, that other piloted Saturn rocket, the Saturn IB, might have become more familiar than the Saturn V. It would have become the AAP workhorse rocket, with more than two dozen flights to its credit. Of all the human spaceflight systems that the U.S. has produced, only the Space Shuttle has flown more missions than that.

The detailed 1971 NASA Marshall Space Flight Center graphic at the top of this post is a good point of departure for describing the Saturn IB. As the graphic indicates, the Saturn IB was a two-stage rocket. The eight H-1 engines in its Chrysler-built S-IB first stage burned liquid oxygen (LOX) and RP-1, a kind of kerosene used as aviation fuel. The single J-2 engine in the S-IVB second stage burned LOX and liquid hydrogen (LH2). Both stages were expended in launching their payload. The S-IVB stage also served (in slightly modified form) as the Saturn V Moon rocket third stage.

The ring above the second stage, the Instrument Unit (IU), was the Saturn IB's IBM-built electronic brain. It controlled the rocket's flight path and various in-flight events, such as first-stage separation and second-stage ignition. The outwardly similar Apollo Saturn V IU was located in the same position on the Saturn V S-IVB stage.

The tapering part above the IU, labeled "Apollo spacecraft," was in fact composed of several major systems. The skinny Launch Escape System (LES) tower on top contained a solid-propellant rocket motor designed to pull the conical Apollo Command Module (CM) to which it was attached to safety in the event that the Saturn IB malfunctioned.

The three-man CM was one part of the two-part Apollo Command and Service Module (CSM) spacecraft. The CSM also included the drum-shaped Service Module (SM), which housed propulsion and attitude-control systems, life-support consumables, and electricity-generating fuel cells.

Finally, the Spacecraft Lunar Module Adapter (SLA) was a segmented, streamlined shroud that linked the bottom of the CSM to the top of the IU. Though shown empty in the graphic, it could serve as a cargo volume. The SLA housed a Lunar Module (LM) Moon lander when it formed part of an Apollo Saturn V stack.

The first piloted Apollo mission: Apollo 7 liftoff from Launch Complex 34 on 11 October 1968. Image credit: NASA.
The first four Saturn IB rockets were test vehicles without crews. SA-201 (26 February 1966), the rocket's maiden flight, launched a Block I Apollo CSM on a suborbital path. The second, SA-203 (5 July 1966), was the first Earth-orbital Apollo flight. Its objective was to enable study of the behavior of liquid hydrogen in weightlessness. This was important for the development of an S-IVB stage that could restart in Earth orbit, as it would be called upon to do when it served as the Saturn V third stage during Apollo lunar missions. Next came SA-202 (25 August 1966), another suborbital Block I CSM test.

Finally, there was SA-204, which launched a test version of the LM into Earth orbit. SA-204 had originally been intended to launch the Apollo 1 crew of Gus Grissom, Ed White, and Roger Chaffee into Earth orbit in early 1967. Sadly, they perished on 27 January 1967, when fire broke out in their CSM during a countdown test at Launch Complex 34, located at Cape Canaveral Air Force Station, just south of NASA's Kennedy Space Center. The SA-204 Saturn IB did not contribute to the disaster.

Saturn IB rockets boosted Apollo CSM spacecraft bearing astronauts into low-Earth orbit just five times. The first piloted Saturn IB, designated SA-205, launched the Apollo 7 crew of Wally Schirra, Donn Eisele, and Walter Cunningham from Launch Complex 34 on 11 October 1968. The astronauts tested their CSM in orbit for 11 days — long enough to reach and return from the Moon — and splashed down in the North Atlantic Ocean on 22 October 1968.

The next Saturn IB rocket to fly, SA-206, did not launch until 25 May 1973, nearly five years after Apollo 7. By then, Apollo lunar landings were already a thing of the past and the Space Shuttle was at an early stage in its development. SA-206 launched the Skylab 2 CSM to the Skylab Orbital Workshop. Skylab, a converted S-IVB stage taken from the SA-212 Saturn IB rocket, reached orbit without a crew on 14 May 1973 atop the last Saturn V to fly. Though officially designated Skylab 2, crew atop SA-206 was the first to visit Skylab. Similarly, Skylab 3 was the second mission to visit the temporary space station and Skylab 4 was the third. The Skylab Program was the shrunken remnant of AAP.

The first Skylab crew, made up of moonwalker Pete Conrad and rookies Paul Weitz and Joseph Kerwin, had to fix Skylab before they could begin their program of scientific research; it had become damaged during launch. They worked in space for 28 days and returned to Earth on 22 June 1973.

The second crew to visit Skylab lifted off atop Saturn IB SA-207 on 28 July 1973. Moonwalker Alan Bean and rookies Jack Lousma and Owen Garriott lived on board for 59 days and splashed down on 29 September 1973. The all-rookie third crew, made up of Gerald Carr, William Pogue, and Edward Gibson, launched on SA-208 on 16 November 1973 and splashed down on 8 February 1974.

The last piloted Apollo mission: Apollo-Soyuz Test Project Apollo on Pad 39B, July 1975. Image credit: NASA.
The last Saturn IB to fly, SA-210, lifted off on 15 July 1975, bearing Gemini and Apollo veteran Thomas Stafford and rookies Vance Brand and Donald Slayton. Their mission, called the Apollo-Soyuz Test Project, was ostensibly an international space rescue test, but was in fact the poster child for President Richard Nixon's policy of detente with the Soviet Union. (By the time SA-210 lifted off, however, Nixon had been out of office for nearly a year.) On 17 July, the three astronauts docked their Apollo CSM, designated simply "Apollo," with the Soviet Soyuz 19 spacecraft.

The Apollo 7 and Skylab 2, 3, and 4 Saturn IBs had carried no spacecraft or cargo in their SLAs; SA-210, on the other hand, carried a Docking Module designed to circumvent incompatible docking units and an airlock that permitted the U.S. and Soviet spacefarers to move safely between the two spacecraft, which had different air mixes. Apollo astronauts breathed pure oxygen at low pressure; Soyuz designers opted for a more Earth-like, higher-pressure oxygen-nitrogen mix. Handshakes, ceremonies, and science experiments with Soyuz 19 cosmonauts Alexei Leonov and Valeri Kubasov followed the docking. Stafford, Brand, and Slayton splashed down in the Pacific Ocean on 24 July 1975, six years to the day after Apollo 11 returned from the Moon.

SA-206, -207, -208, and -210 all launched from the Launch Complex 39B Saturn V pad at NASA’s Kennedy Space Center. NASA planning contractor Bellcomm realized in late 1968 that launching AAP missions from Launch Complex 39 would allow Launch Complex 34 and its twin, Launch Complex 37, to be abandoned, thus saving NASA a considerable sum of money.

The decision to launch Saturn IB rockets from a Saturn V pad led to what was probably the most unusual launch pad arrangement of the Space Age. Called the "milk stool," it was a platform that raised the Saturn IB so that its S-IVB stage and CSM were at the same height as their Saturn V counterparts. This enabled the Skylab and Apollo-Soyuz Saturn IBs to use the existing Launch Complex 39B S-IVB and CSM umbilicals and crew access arm.

A total of 14 Saturn IB rockets were at least partly constructed. Besides four unmanned Saturn IB test missions that flew before Apollo 7 and the five Saturn IB-launched missions described above, there were SA-209, SA-211, SA-212, SA-213, and SA-214. SA-209 was actually prepared for a possible launch – for a short time in July 1973, it appeared that it would launch a two-man rescue CSM to recover the Skylab 3 crew, whose CSM had developed attitude-control system leaks soon after launch. It also stood by to launch the Apollo-Soyuz backup CSM. SA-209 is now on display at the Kennedy Space Center visitor center. As mentioned above, the SA-212 S-IVB stage became Skylab. The other Saturn IB rockets were turned into displays of various kinds or scrapped.


Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles, SP-4206, Roger Bilstein, NASA, 1980.

More Information

"Assuming that Everything Goes Well in the Apollo Program. . ." (1967)

Dreaming a Different Apollo, Part One


  1. "The S-IVB stage as the Saturn V moon rocket's third stage."

    Am I correct in assuming you intended something like "..was also used as..." to be in there?

  2. Indeed you are. Thanks for catching that typo.


  3. The Saturn IB could have accommodated not only heavier but wider payloads than the USAF's Titan III; yet the Titan III became the USA's workhorse launcher for medium-heavy payloads like the Keyhole series reconnaissance satellites and the Voyager and Viking probes. Had the USAF adopted the Saturn IB, we would have been able to keep a man-rated launcher available through the 1970s.

    Even more forgotten than the IB was the Saturn IA. It used the S-IVA second stage which was smaller and used six Centaur LH2/LOX engines instead of a single J-2 engine. It launched the Pegasus series of satellites used to quantify the micrometeoroid risk. The S-IVA would have made a good apogee kick stage for a Saturn V optimized for earth-orbit payloads.

  4. Michael:

    Everything I read says the Saturn IB was more costly than the various iterations of Titan III; when I compare available cost numbers, however, it appears that Saturn IB costed out about the same as the Titan III. I expect the story is more complicated than mere cost-savings, but I haven't had time to delve into it.

    Saturn IA seems to have been called Saturn I, though in retrospect Saturn IA is a reasonable designation (there being a Saturn IB). For a time Saturn IB was called Advanced Saturn I. (See the graphic in my previous post.)

    How would maintaining the Saturn IB as a piloted launcher have impacted Space Shuttle? If one assumes that the Complex 34 and 37 pads were abandoned and Shuttle needed Complex 39 modifications, then might Saturn IB have lost its launch pad shortly after ASTP? There exist, of course, two Complex 39 pads, so perhaps this would not have been an issue.


    1. There had been many more Titans flown than Saturn IBs, so I'm thinking that the Titans were more of a known quantity in terms of performance, reliability, etc. The unit cost was probably lower or would be lowered in the nearer future than for the Saturn IB.

      The hypergolics probably made certain things easier, you could fuel the Titan up and let it sit there until you needed to launch without worrying about boiloff, etc. Although the fuels were more difficult to handle the equipment needed didn't involve cryogenic cooling and handling. I'm thinking that there may have been some operational advantage to the Titan that made it cheaper to operate and more flexible for what the Air Force desired to do.

  5. You make good points - if you don't mind, though, might you clarify something for me? What you seem to be saying is that Titan was a USAF vehicle, and NASA tailored its planetary missions (Viking 1 & 2, Voyager 1 & 2) to the vehicle the USAF wanted. Would you say that is correct?

    On the other hand, the big Titans were not man-rated. Saturn IB was. So, a political decision was made not to fly it that precluded piloted spaceflight in the US between 1975 (ASTP) and Space Shuttle. Some have said Nixon didn't want the JFK/LBJ Apollo Program around any more because it was the JFK/LBJ Apollo Program. Just as likely, cuts in NASA funding begun after the Apollo 1 fire that cranked up under Nixon, combined with runaway inflation, made parallel programs of Shuttle development and Saturn IB-based missions impossible.

    Shuttle was supposed to take over as NASA's piloted spacecraft, and all Apollo and Apollo-derived missions beyond a certain minimum number were forfeit. So, we saw three Skylab visits - perhaps in answer to Soviet space station plans - but NASA hatched plans for as many as five, and the second Skylab workshop and the Saturn IBs that would have staffed it were not launched. ASTP flew, but a proposal to carry out a second ASTP flight in 1977 (and other "gap-filler" flights using Apollo hardware) got nowhere.


    1. If I remember my history correctly the original Voyager did use a Saturn IB and I seem to recall that the original Grand Tour design(s) used a Saturn V. I think by the time they cut metal for Viking and Voyager it had become apparent that Saturn rockets were not going to be available whereas the USAF was still using Titans, and those Titans were still rolling off of the production line. So yeah, NASA wound up tailoring their missions to use the USAF-chosen launch vehicle.

      There was barely enough money for shuttle development which meant that there was NO money for continued Saturn IB manned ops (although I think the money for a second Skylab series could have been found; after all, the hardware was already manufactured).

      And there was a hidden cost to continuing manned Saturn IB flights: they needed a purpose, like a space station or a series of science missions. The cost of the purpose plus the Saturn IB flights and hardware probably costed out as *higher* on a yearly basis than shuttle development...and there was the initial belief that the shuttle might even turn a profit by hauling cargo cheaply, so from a monetary standpoint the shuttle made more sense at the time.

  6. (I do not know if you bother to reply to new comemnts published on old articles, but in case you do:)
    I read once that the 8 H-1 engines of the first stage are actually far descendants of the engine of the A-4 (or V-2) rocket, i.e. an engine developed by Walter Thiel for the nazis and brought to the US by Wernher von Braun and his team. Do you tink that this could be true?

  7. Would the original Saturn I (or IA) have made a good manned launcher or unmanned satellite booster had Saturn IB not been developed? It did launch boilerplate versions of the Apollo CSM and the Pegasus satellites into orbit. Both Saturn I and IB were originally designed for this with the possible addition of the Centaur as a third stage in place of Apollo. I have also read that the S-IV stage would not have had enough power to place a live CSM into orbit and the SPS would have been needed as a kick stage to place it into orbit.

    1. Hi. Old question, but probably not. The IB was developed because of the commonality with the Saturn V and the fact the S-I could not launch a full CSM (even unfueled) to LEO.

      It also wouldn't have made much sense, the J-2 would have been a good engine (much better than the RS-25) to rebuild a super-heavy rocket around- it was high thrust without being too expensive/high performance.


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