North American Aviation, the contractor the the Saturn V's second stage, the S-II, built a number of test stages in addition to the fifteen flight stages. One of the more unusual stages was the Common Bulkhead Test Tank, or the CBTT.

The CBTT's purpose was to test the stage's common bulkhead design under liquid hydrogen temperatures. Although the S-IV and S-IVB stages already employed common bulkheads with liquid hydrogen, the sheer size of the S-II's common bulkhead was unprecedented—33 feet for the S-II, versus 18 feet for the S-IV and 21' 8" for the S-IVB.

The CBTT test article consisted of a production common bulkhead, a production forward bulkhead, two production LH₂ cylinders, a special forward skirt, a simulated aft bulkhead, and an aft skirt. These components were joined to form a large tank divided by the common bulkhead into two smaller tanks.

After completion of assembly at its Seal Beach facility, NAA then transferred the test tank to the Santa Susana Field Laboratory, where the tests would actually be performed. The first 60 miles of the journey, between Seal Beach and the U.S. Navy docking facility at Port Hueneme (in the vicinity of Oxnard), was performed via the barge Orion (also known as "YFNB-29") on June 1 and 2, 1965. A truck took over from there, moving it over 50 miles of Ventura County roads and California freeways to the SSFL between June 2 and 3. Before the stage hit the road, however, an advance team surveyed the route, coordinating with the necessary utilities and highway departments to prepare the roads and temporarily remove overhead lines.

This voyage was the subject of an article, "The Tortoise Steps of Saturn S-II", which appeared in NAA's in-house magazine, Skyline, which I present here.

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Here are a few of the highlights from the booklet:

Photos from Skyline, Vol. 23 No. 3., which was published quarterly by North American Aviation, Inc. for employees. Contents copyrighted 1965 but may be reprinted with credit.

Interestingly enough, the second last photo (the CBTT making its way through a mountain pass) appears from time to time on the Internet, always mis-captioned (e.g., in "largest things ever moved" type slideshows). I blame Getty Images, which incorrectly labels it as "A section of the giant Saturn V-Apollo rocket being transported from its building site to the launch pad in Cape Kennedy where it will be properly assembled and then launched (January 16, 1967);" this (very wrong) caption is invariably and faithfully reproduced by these other Internet outlets.

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