The Saturn 500F: The Moon Rocket That Couldn’t Fly

While space enthusiasts tend to focus their attention on spacecraft and the rockets used to launch them, there is a lot more that is needed to fly missions to space including a launch complex and its supporting infrastructure. Without a doubt, the most famous of these has got to be Launch Complex 39 (LC-39) at NASA’s Kennedy Space Center (KSC).

The Vertical Assembly Building (VAB), shown here in an artist’s cutaway from 1964, was at the heart of Apollo’s Launch Complex 39. (NASA)

Originally built to support the Apollo program, LC-39 was designed to assemble and launch the 111-meter tall Saturn V which sent the Apollo spacecraft and its crew of three to the Moon. The three-stage Saturn V and its Apollo payload were stacked inside the Vertical Assembly Building (VAB – later known as the Vehicle Assembly Building) on top of a mobile launch platform fitted with it own launch umbilical tower. The 160-meter tall VAB was capable of handling up to four Saturn V rockets in its spacious high bay area with additional space in the low bay area for various tasks with individual stages and other mission hardware. With a total volume of 3.7 million cubic meters, the VAB is still one of the largest buildings in the world by volume. Once assembled, one of two diesel-electric crawler-transporters moved the mobile launch platform and its Apollo-Saturn V up to six kilometers to one of two launch areas designated Pad A and B (although in the original plans, up to four pads were envisioned). In addition to these notable components, LC-39 also had crawlerways, roads and canals to move equipment and crews, propellant storage facilities as well as a range of other infrastructure to support launches. And situated right next door to the VAB is the Launch Control Center.

A view of the VAB and mobile launch platforms with their umbilical towers under construction at LC-39 as they appeared in January 1965. (NASA/KSC)

With planning starting in 1961, construction of the facilities at LC-39 proceeded quickly and by 1966 they were nearing completion. In order to test and verify the launch facilities, techniques, handling procedures, and operations at the new LC-39, a Saturn V test article was required. During the development of the Saturn V by the team at NASA’s Marshall Space Flight Center (MSFC) led by Wernher von Braun, provisions were made to construct a number of non-flight Saturn V components, stages and even entire rockets to conduct various tests. For these facilities checks, the Saturn 500F (with the “F” standing for “Facilities”) was constructed. Also known as SA-500F or the Facilities Integration Vehicle, this rocket consisted of three stages which duplicated the flight configuration and umbilical connections of the Saturn V rockets which would actually fly. All the ordnance on the rocket as well as ullage and retrograde rockets were inert since live units were not required.  The stages of the SA-500F were typically not even equipped with real engines but had simulators since the genuine articles were not needed for the facilities checks. The tests using the Saturn 500F would provide not only those involved with the Apollo program but the public as well with their first real view of the complete rocket which would send American astronauts to the Moon.

Diagram showing the components of the non-flight and earliest flight models of the Saturn V including the Saturn 500F or SA-500F (second from right). Click on image to enlarge. (NASA/MSFC)

Getting Out to Pad A

The first component of the SA-500F to arrive at the VAB was the third stage designated S-IVB-F. Initially, it was built and used for checking launch facilities for the Saturn IB whose second stage, the S-IVB-200, was nearly identical to the S-IVB-500 model used as the third stage of the Saturn V. During August and September of 1965, the stage in its S-IVB-200F configuration had been used with the first flightworthy Saturn IB first stage, S-IB-1, to checkout the new facilities at LC-34 in preparation for the first Apollo-Saturn IB flight in February 1966 (see “The First Flight of the Apollo-Saturn IB”). The S-IVB-200F arrived at the VAB on September 29 and work immediately began to convert it into the S-IVB-500F configuration required for the Saturn 500F facilities check out. Since its appearance was not critical to its function, the S-IVB-F retained its Saturn IB markings instead of being repainted to match those chosen for S-IVB-500 which contributed to the distinctive look of SA-500F.

The S-I-F first stage of the AS-500F being lifted into position in the VAB. Note that this stage has only one F-1 engine with inert masses replacing the other four. (NASA)

As work continued to complete the final preparations of the facilitates at LC-39, the first stage of the AS-500F, designated S-IC-F, arrived at KSC on January 19, 1966. It was equipped with a just single F-1 engine with weights to simulate the mass of the other four. By February, crane operators in the VAB began practice runs with a 9.5-meter spherical container filled with various amounts of water to simulate the masses of Saturn’s stages. On February 20 the second stage, S-II-F which was fitted with five simulated J-2 engines, was shipped to KSC via barge. Finally, the S-IC-F was lifted from the VAB transfer aisle and onto the Mobile Launch Platform 1 on March 15 to begin the first stacking of a Saturn V at the VAB.

The S-II-F stage being lifted off of its carrier in preparation for stacking. Note that this stage sported five engine simulators instead of the J-2 engines the flight-ready version of this stage would carry. (NASA)

On  March 25, 1966, the S-II-F stage was lifted into place on top of the S-IC-F. With the conversion of the S-IVB-500F officially completed on that same day, it was finally added to the stack on March 28 and 29. On March 30, the S-IU-500F Instrument Unit, which would control the Saturn V in an actual flight, was added to complete the Saturn 500F. For this “mission”, a model of the Block I Apollo spacecraft known as M-11 fitted with a mock Launch Escape System (LES) served as the payload of the SA-500F. On May 2, M-11 was added to the SA-500F completing the stacking operations. After some additional checks, the first Saturn V was ready to be moved out of the VAB and towards Pad A.

The Apollo M-11 model shown being lifted from its transporter for stacking on the Saturn 500F. (NASA)

With much fanfare, SA-500F was moved out of the VAB on May 25, 1966 – five years to the day after President John F. Kennedy had committed the nation to sending men to the Moon. While there were many VIPs present at the rollout ceremony including von Braun, the real star of the day was the huge Saturn 500F. During the trip out to Pad A, the transporter at times attained its top speed of 1.6 kilometers per hour finally reaching its destination as dusk settled over the Cape. Two hours later, the mobile launch platform with the Saturn 500F was secured for the beginning of a long series of tests.

Wernher von Braun and KSC Director, Kurt Debus, in the VAB during the rollout of Saturn 500F. (NASA)

After just two weeks out at Pad A, however, the decision was made on June 8 to move SA-500F back to the VAB as Hurricane Alma approached. Although the storm was not expected to be powerful enough to cause problems, it was felt that this would be a good exercise for the future when more powerful storms threatened the Cape during Apollo launch preparations. Within three hours of the 1:00 PM decision to move Saturn 500F, the mobile launch platform had been disconnected from the pad and made ready for transport as winds gusted to 80 kilometers per hour. At 5:33 PM, the crawler started making its way down from Pad A with its 5,700 metric ton load. Saturn 500F finally reached the VAB at 11:43 PM in the pouring rain after experiencing peak wind gusts of 96 kilometers per hour. One hour later, the mobile launch platform was secured to its mountings in the VAB.

Saturn 500F shown during its rollout from the VAB to Pad A. (NASA/KSC)

After two days inside the VAB, Saturn 500F made the eight-hour journey back out to Pad A for a second time. By July, the Mobile Service Structure which provided ground crew access to the Saturn V was moved to Pad A to check its fit with Saturn 500F. Next were the “wet tests” where the tanks of the SA-500F stages were loaded with propellants. The launch complex’s RP-1 fueling system was tested in mid-July with 760,000 liters of kerosene pumped into the S-IC-F. Ongoing problems with contamination in the LOX lines in the LC-39 facilities delayed loading tests until August 15 when the failure of a pair of recirculation pumps forced a stop to the exercise. During the test rescheduled for August 19, a sequence of unforeseen events lead to the failure of a 46-centimeter flexible line beneath the ground system’s LOX storage sphere leading to 2.7 million liters of LOX being dumped onto the ground. If this were not bad enough, the sudden drop in pressure caused by the rapid loss of all that LOX buckled some of the 9.5-millimeter steel plates that made up the tank’s inner liner.

The Mobile Service Structure during its fit checks with the Saturn 500F at Pad A. (NASA)

It took until September 14 to repair the damage to the LOX facilities caused by the incident and make modifications to prevent a recurrence. The LOX tanking tests with the S-IC-F finally went off without a hitch on September 20.  Three days later, the S-II-F successfully completed its manual tanking test with LOX and liquid hydrogen. On September 28, the LOX and liquid hydrogen manual tanking test with the S-IVB-F was stopped at the 52% mark because a leak in a swing arm umbilical connection. Although the test was stopped, it had met its objectives and there was no need to rerun it. The other issue of note, however, was a leak in a hydrogen gas vent on the mobile launch platform which caused a small fire which was extinguished by purging the line with gaseous nitrogen. While some prelaunch procedures with the S-IVB-500F could not be practiced as a result, in the end the launch vehicle satisfactorily met its wet test objectives by October 12. With all the pad tests completed, SA-500F was rolled back to the VAB on October 14.

The Saturn 500F shown being rolled back to the VAB for the last time on October 14, 1966. (NASA/KSC)

Destacking and Afterwards

After the Saturn 500F had been returned to the VAB, it was subjected to one last impromptu test before destacking. Engineers wanted to perform a “shake test” to get more information about the rocket’s structural mechanics by making it sway while it sat on the mobile launch platform. Initially, a group of engineers wearing tennis shoes laid on their backs on the floor of one of the VAB’s upper platforms and pushed against the rocket with their feet. When that did not produce the desired result, a rope was slung around the Command Module of the M-11 Apollo model at the top of the stack and engineers pulled on it to set the rocket swaying at its natural frequency. While this produced a much more noticeable pendulum motion, the LES on top of M-11 eventually broke loose with a loud bang when the truss that connected it to the top of the Command Module failed. Thankfully, the LES fell just a short distance before it became lodged against the Command Module and some of the VAB’s work platforms. As a result, damage from this incident was minimal although it was not widely reported leading to claims of a cover up in subsequent years.

The LES is shown being lowered to the floor of the VAB after it had broken loose during an impromptu “shake test” using SA-500F. (NASA)

A week after returning to the VAB, destacking of the Saturn 500F began. Although there had been plans to restack SA-500F to test Pad B during the summer of 1967, in the end the plans were shelved since it was determined to be unnecessary. The S-IC-F was subsequently returned to MFSC and was eventually scrapped. Likewise the S-II-F was shipped back to MFSC but had a very different fate. The original S-II-D stage of the SA-500D to be used for dynamic testing of the Saturn V had been destroyed during structural stress tests. The S-II-F was modified to serve as the second stage of the SA-500D and was eventually incorporated into the Saturn V on display at the US Space & Rocket Center in Huntsville, Alabama. The S-IVB-F also found a new life after the Saturn 500F tests. In 1970 it was modified to become the Skylab Workshop Dynamic Test Stage which was used for dynamic testing at NASA’s Johnson Space Center starting in December 1970. It was then shipped to MSFC in June 1971 for static testing there and finally returned to KSC in June 1974. The ultimate fate of this test article is not known but it is generally believed to have been scrapped. The M-11 Apollo model was eventually reused to top off the surplus Saturn IB SA-209 on display at the KSC Visitor Center’s Rocket Garden.

The M-11 Apollo model, shown here in 1984, was eventually placed on display in the Rocket Garden at KSC’s Visitor Center with a surplus Saturn IB. (A.J. LePage)

And so ends the story of the first Saturn V. Although the Saturn 500F was never meant to fly, it helped pave the way to the successes of its later siblings which sent astronauts to the Moon. On October 27, just days after destacking of AS-500F was completed, workers lifted S-IC-1 – the first stage of AS-501 – into place on the mobile launch platform. And with this, over a year of preparations began for the first test flight of the Saturn V which would be known as Apollo 4 (see “Apollo 4: The First Fight of the Saturn V“).

The first stage of the AS-501, designated S-IC-1, is shown being lowered into place on Mobile Launch Platform 1 on October 27, 1966 as preparations begin for the first Saturn V test flight. (NASA)

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Related Video

Here is a collection of footage of the Saturn 500F at LC-39.

Related Reading

“The First Flight of the Apollo-Saturn IB”, Drew Ex Machina, February 26, 2016 [Post]

“Apollo 4: The First Flight of the Saturn V”, Drew Ex Machina, November 11, 2017 [Post]

General References

Charles D. Benson and William B. Faherty, Moon Launch! A History of the Saturn-Apollo Launch Operations, University Press of Florida, 2001

Roger E. Bilstein, Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles, University Press of Florida, 2003

Alan Lawrie with Robert Goodwin, Saturn V – The Complete Manufacturing and Test Records, Apogee Books, 2005