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S-II LH2 Tank Construction

Mike Jetzer

© 2010 Michael L Jetzer. All rights reserved.

The Description of S-II Stage Structures describes LH2 tank of the S-II, the Saturn V's second stage, as follows:

The LH2 tank is made up of six cylindrical sections, an ellipsoidal forward bulk[sic] and the common bulkhead. The volume of the LH2 tank is 36,883 cu. ft. The forward bulkhead and the cylindrical sections are of 2014 aluminum covered with external insulation.

The cylindrical sections are made up of quarter panels welded together. The quarter panels have integral longitudinal and circumferential stiffeners. Riveted to the circumferential stiffeners are 7 inch wide rings of 2024 aluminum for additional support. ... The aft cylindrical section has external tapered longitudinal stiffeners 25 inches long to assist in transferring loads from the bolting ring to which it is fastened. The bolting ring is 15 inches long and has provision for attachment of the LOX tank, the aft skirt and the LH2 cylinder.


Insulation on the cylindrical section and the forward bulkhead is external to the tank. It consists of glass-phenolic honeycomb core filled with isocyanate foam covered with a nylon phenolic skin and sealed with a plastic film. Provision is made in the insulation for purging and a leak detection system. Insulation on the bolting ring is machined blocks of plastic.

Note that the external insulation as described above was used on the various testing S-II stages and the first seven flight stages (the unmanned Apollos 4 and 6, plus Apollos 8 through 12). Starting with S-II-8 (used on Apollo 13), an external spray-on foam, not unlike the foam used on the Space Shuttle External Tank, was used instead.

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Taken from page 9 in the PDF of the Description of S-II Stage Structures

Last updated 2016-06-20

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