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  Saturn V: Why no S-III (S-3) stage?

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Author Topic:   Saturn V: Why no S-III (S-3) stage?

Posts: 2118
From: Belfast, United Kingdom
Registered: Feb 2002

posted 09-14-2008 02:27 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
Is there any obvious reason why there was no S-III (S-3) stage on the Saturn V? The first stage was the S-IC, the second stage was the S-II. I know the S-IVB was an improved version of the S-IV which had been flown on the Saturn 1, but that doesn't really explain why they didn't call the third stage of the new Saturn V rocket the S-III.


Posts: 388
From: Germantown, WI USA
Registered: Jan 2004

posted 09-14-2008 03:16 PM     Click Here to See the Profile for mikej   Click Here to Email mikej     Edit/Delete Message   Reply w/Quote
You have to go back to the very early design variations of the Saturn series.

The Saturn was initially (or at very early on) envisioned as a five-stage vehicle. Using a "build block" approach, some of the upper stages would be test-flown before the intermediate stages.

So, the very first Saturn (SA-1) consisted of an S-I stage and dummy S-IV and S-V stages. Before a live S-IV was ever flown (as the second stage of SA-5, the first of the Block II series), the idea of an S-V stage was dropped.

The Saturn I series gave way to the Saturn IB. The first stage of this rocket was modified and renamed to the S-IB (although it seems to me that there were more differences between the Block I and Block II S-I stages than between the Block II S-I and the S-IB). The second stage of this rocket was an uprated version of the S-IV, the S-IVB; this stage was considered sufficiently similar to the S-IV stage that it was sole-sourced to Douglas without the usual bidding process.

Of course, the S-IVB would also be used as the third stage of the Saturn V. Its first stage was the S-IC. Since no stage initially designed to be a second stage had ever been manufactured (remember, the second stage of the Saturn IB was still an evolved version of the initially-envisioned fourth stage), it received the S-II designation.

With the S-IC, S-II, and S-IVB, there was no need for another stage to be designed as a third stage.

More information about the evolution of the Saturn concept can be found in Stages to Saturn, especially Chapter 3.

Lou Chinal

Posts: 983
From: Staten Island, NY
Registered: Jun 2007

posted 09-14-2008 06:21 PM     Click Here to See the Profile for Lou Chinal   Click Here to Email Lou Chinal     Edit/Delete Message   Reply w/Quote
So true! The entire Apollo system was a series of compromises.

If you look at the service module it is far too big. It's powerful enough to lift the command module off the SURFACE of the moon. That was the orginal design. Another thing is that it's to thin. The command module is 160 inches in diameter, while the service module is 154 inches in diameter. The CM hangs out 3in. on each side. Max Faget told me about 'making' it fit. That's what happens when one team is on the east coast (SM) and the other team is on the west coast (CM).


Posts: 2118
From: Belfast, United Kingdom
Registered: Feb 2002

posted 09-16-2008 06:00 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
Thanks for the information. As a well-known sci-fi character might have said: it's not entirely logical, but it is interesting.

E2M Lem Man

Posts: 793
From: Los Angeles CA. USA
Registered: Jan 2005

posted 09-17-2008 08:14 PM     Click Here to See the Profile for E2M Lem Man     Edit/Delete Message   Reply w/Quote
I have found some documentation that says that for the Saturn C1, 2, 3 that an upper stage (S-III) would have been an adaption of the Centaur stage that was used on Titan-3 and Atlas vehicles.


Posts: 59
From: London
Registered: Oct 2008

posted 10-31-2008 03:29 AM     Click Here to See the Profile for Proponent     Edit/Delete Message   Reply w/Quote
Just to amplify on others' replies, I'll summarize what I've learned about this topic from reading "Stages to Saturn," available on-line from the NASA history website.

Quite a number of Saturn stage configurations were considered between 1958 and 1960. One early version was the Saturn A-1, which had the familiar S-I stage plus a Titan I 1st stage as a 2nd stage and a Centaur as a 3rd stage. The Saturn A-2 was the same except that the 2nd stage consisted of a cluster of 4 Jupiters rather than a Titan 1st stage.

In the Saturn B-1, the 2nd stage was a custom-developed lox/RP-1 stage powered by 4 H-1 engines. Again, the Centaur was to be the 3rd stage.

Then there was the C-1: S-I plus S-IV plus Centaur, known in this application as the S-V. This is the Saturn I which actually flew, except that the S-V stage was never live.

The original C-2 design would have been S-I plus S-III plus S-IV plus, for some missions, S-V. The S-III was to have been a lox-hydrogen stage powered by two J-2 engines.

The original C-3 configuration was S-I plus S-II plus S-III plus, for some missions, the S-IV and even S-V. The S-II was to have had four J-2 engines and the S-I would have been upgraded either by increasing the thrust of its eight H-1 engines to 250,000 lb or by replacing the center four H-1 engines with a single F-1.

In December 1959, the Silverstein committee (formally known as the "Saturn Vehicle Evaluation Committee" or something like that) decided to skip development of the Saturn A and B configurations and go straight to the C configurations, which gave the most lifting power.

NASA HQ accepted the recommendations of the Committee and forwarded them to Hunstville. Huntsville concurred, but dropped the S-III stage. In the C-2 it was replaced by the S-II stage, with 4 J-2 engines. The upgraded S-I in the C-3 was replaced by a new stage powered by two F-1s. Eventually, as we all know, the C-2 and C-3 were dropped entirely. The C-4 was briefly considered (4xF-1 plus 4xJ-2 plus 1xJ-2) before being replaced by the C-5. The S-II designation was now applied to the 2nd stage of the C-5, of course.

Last night on YouTube, I found a NASA film about Saturn from the early 60s. I think it's a great shame that in the rush to get to the moon the C-2 was never developed. A manned lunar voyage using five or six C-2 launches would have been possible (see the extensive documentation available on the Army's Project Horizon that is available from, and the C-2 was small enough so that, unlike the Saturn V, it might have been feasible to keep it in production after the moon race had been won.

All times are CT (US)

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