While exploring the Thomson collection in the archives of the University of Alabama at Huntsville I happened upon a memo regarding the F-1 rocket engine display at the Alabama Space & Rocket Center (later to be renamed the U.S. Space & Rocket Center), expressing concern about the manner in which it was displayed:

                                        September 29, 1986

TO:        CR01/A. McCool

FROM:      EA01/J. Thomson

SUBJECT:   F-1 Engine on Display at ASRC

Recently, I learned through Mr. Tom Osborne that ASRC has an F-1 engine standing upright and resting on the nozzle skirt. This engine, I understand, is in an area where the general public has access. In my recent work with the F-1 engines residual from Apollo, we have been trying to assess the possible damage incurred during storage or in particular stored positions. What I have learned is that when the 18,600 lb engine is resting on the nozzle the safety factor is ≈ 1.5. During the F-1 engine program days the practice was not to store the engine in the upright position resting on the nozzle. I am calling this to your attention so that you can coordinate this matter with the appropriate people at MSFC responsible for the safety of F-1 engine displays.

[signed]
J. Thomson
Team Leader
Propulsion System Studies

cc:
EA01/Mr. Kingsbury

See download link below.

It's unclear as to what the "appropriate people" would have done to address this issue.

In recent years, Marshall Space Flight Center has started using "throat supports", columns topped by a platform on which an engine's injector sits. Thus, the weight of the engine is borne by the injector, rather than the lower portion of the engine. Marshall has even started using throat supports with J-2 engines.

However, I don't believe I was aware of throat supports prior to the installation of F-5036 in front of MSFC Building 4200, so it's possible that they are a recent development. Perhaps Thomson was advocating for the F-1 engine to be displayed horizontally, on its engine handler (i.e., on a dolly), rather than vertically.

In his memo, Thomson is presumably talking about F-1 rocket engine F-4028, currently displayed outdoors. This engine was displayed vertically indoors at the Rocket Center's opening. It was later moved outdoors, although I am uncertain when this move was made, although the 1979 film Ravagers was shot, in part, at the Alabama Space & Rocket Center and showed the engine in the Rocket Park, so it seems that the engine spent only a few years indoors.

After residing in the Rocket Park since the mid- to late 1970s, F-4028 was moved to Apollo Court, just outside the Davidson Center, as part of the Rocket Park renovation; I photographed F-4028 there in April 2024.

The USSRC curator tells me that F-4028 still resting directly on the pavement prior to the move. The Rocket Center consulted with Marshall Space Flight Center regarding the move and asked for plans for a suitable throat support, although MSFC was unable to provide such plans. An inspection of the engine showed no signs of structural issues due to it resting on the nozzle extension, and the engine is still supported by its nozzle extension in its new location (although it is resting on some metal and plastic pads, to prevent it from sitting directly on the concrete).

There are only a small number of F-1 engines which are displayed vertically:

• F-1 engine mockup FM-103 at the Kennedy Space Center Visitor Center is displayed vertically. This engine has been at the KSC Visitor Center for a very long time. A Facebook post by the Visitor Center implies that the engine has been at the VC since it opened in August 1967, although this is not certain. There is a photo from May 1969 which shows the F-1 on the Visitor Center grounds. I do not know whether this engine has a throat support or not, although since it has been at KSC for such a long time, I assume that it does not.
• Engineering Mockup 1 (EM-1) sat outside the Rocketdyne headquarters in Canoga Park since 1979 before being relocated to the Aerojet Rocketdyne headquarters on De Soto Avenue in October 2013. Although I've seen many photos of the engine on a flatbed truck during its actual transport, I haven't seen any photos of the engine being removed from its former site or emplaced at its new site. One photo of the engine on the trailer was taken in front of the old site, which showed no evidence of a throat support.
• F-1 engine F-041, now at the Air Zoo, was displayed vertically at the Michigan Space & Science Center since the museum opened in 1977. Sometime after the engine was relocated to the Air Zoo, I contacted West Shore Services, the crane company which performed the move. West Shore's project manager reported that it had no throat support.
• F-1 engine F-4023 at Marshall Space Flight Center is displayed vertically in front of Building 4205. Erected circa October 2009, it sits on a throat support. Prior to its erection at Marshall, it was stored on an engine handler.
• F-1 engine F-5036 at Marshall Space Flight Center was displayed vertically in front of Building 4200 prior to that building's demolition. Erected in May 2008, it sat on a throat support. Prior to its erection at Marshall, it was stored on an engine handler.
• F-1 engine F-5038-2 at Space Center Houston is displayed vertically. It appears to rest on a G4080 nozzle extension handling fixture, so I assume that it does not rest on a throat support.
• F-1 engine F-6049, formerly displayed at Udvar-Hazy Center on horizontal engine handler, was transferred first to Marshall Space Flight Center (still on its engine handler) where it stayed for a short time for some SLS-related tests. In February 2017 Marshall transferred it to Seattle's Museum of Flight (which I have not yet visited) and installed it vertically on March 14 and 15, 2017. While it is not on a throat support, it is not resting directly on its nozzle extension (see below).

A site contributor volunteers at the Museum of Flight, so I emailed him regarding F-6049. He was not present during the engine's installation, so he forwarded my email to the museum's Adjunct Curator for Space History. The curator replied that the engine, while not on a throat support was also not resting directly on its nozzle extension: MSFC discouraged the museum from using a throat support, as it would have put the entire weight of the engine on the copper injector plate, possibly deforming it over time. Instead, the museum devised a mount which fit between the main thrust chamber and the nozzle extension. The thrust chamber rests on the mount and the nozzle extension hangs from it, so that the weight of the engine is borne neither by the injector nor the nozzle extension. The video linked above shows this mount (the black fixture at right during the engine lift portion of the video).

So, it seems that, only a few years after the rise of the throat support, it has fallen out of favor. The Museum of Flight installed their F-1 about five years before F-5036 was removed from in front of MSFC Building 4200, but I can't help but wonder if Marshall engineers found damage to F-5036's injector when it was returned to storage.

Although Thomson was concerned about the engine being supported by its nozzle extension, time has shown that the nozzle extension is up to the task. F-041's nozzle extension underwent many freeze/thaw cycles through years of Michigan winters, F-4028's nozzle extension has withstood the searing Alabama heat since the 1970s, and EM-1 has even survived 46 years of of Los Angeles smog, so the nozzle extensions appear to be immune to even the worst weather.

A possible cause for his concern may be rooted in the evolution of the F-1's nozzle extension. Throughout the Apollo program, there was an effort to reduce weight in the launch vehicle, which would allow the Saturn V to loft a greater payload. Like many parts of the Saturn V, the F-1's nozzle extension underwent weight reduction.

Page 1-73, Storage Preparation for Thrust Chamber Nozzle Extension, of the F-1 Rocket Engine Operating Instructions notes that earlier models of the nozzle extension (209210, 209210-11, and 209210-21) could be stacked three high on pallets with support provided between pallets, but a later (presumably lighter) model (209210-31) had to be stored singly or as the top unit on a stack.

It is possible that this later model of the nozzle extension was unable (or potentially unable) to safely support the engine, and Thomson was familiar with this model. I have confirmed that F-041, F-4028, F-5038-2 have earlier nozzle extension models (209210-21, 209210, and 209210-A, respectively), which are presumably stronger than the final model. Of the vertical engines for which I've noted a nozzle extension model number, only F-5036 has the -31 variant, and it was displayed on a throat support.

Download Link

Download ASRC Nozzle Extension Memo.pdf (236k).