F-1 Engine Revisions

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Block versions

There were multiple revisions of the F-1 engine from the R&D versions through to the final versions launched in the later Apollo missions. Some of the revisions were internal alterations while others did change some of the external characteristics. Here is a brief overview of the various versions and some of the changes that were made.

Block 0 - R&D versions
​Block 1 - F-1001 to F-1002
Block 2 - F-2003 to F-2010
Block 2 - F-3011 to F-3016 (Exhaust manifold was changed and NASA incremented the first digit but no other changes, so still considered Block 2)
​Block 3 - F-4017 to F-4028
Block 4 - F-5029 to F-5042
Block 5 - F-6043 to F-6098

High pressure ducts

The ducts were initially flexible and tied externally and then internally and used bellows to absorb vibrations from the turbo pumps. In the final version they were rigid ducts. The rigid ducts have a distinct "U" shape, whereas the flexible ducts were straight. The rigid ducts were introduced in Block 3 engines F-4017 (F-2017) and onwards (Apollo 6 and on).

Early versions of the F-1 with straight ducts.

Block 3 and on engines with "U" shaped ducts.

Turbine Exhaust Manifold

The heat exchanger and turbine exhaust manifold formed an inverted "T" shape but starting part way into Block 2, F-3011 (F-2011) onwards, it formed and inverted "Y".

The original inverted "T" shaped manifold.

The upgraded manifold with an inverted "Y" shape.

Image credit: NASA

LOX Dome inlet

Initial designs and engines had twin-elbow LOX inlets but it was later redesigned into what they termed a single "fish mouth" inlet. This change was made in Block 2 and onwards, starting on engine F-2003

Twin-elbow LOX inlets. Image credit: NASA

Fish mouth inlet from recovered Apollo 12 engine. Image credit: Cosmosphere