In article ,
Pat Flannery wrote:
Yeah, but it was pretty large and heavy for its capabilities...

The S-IB was eight tons lighter than the S-I, due to a combination of
reduced requirements(*) and better understanding of margins. Despite
MSFC's reputation for conservative engineering, my recollection is that
the numbers actually don't come out all that badly.

(* The original S-I's design payloads included Dyna-Soar and RIFT (flight
test of a nuclear engine), and the demise of those payloads reduced both
maximum bending loads and maximum axial loads. )

...and eight
motors is about where you start to worry about the odds of a
catastrophic single engine failure occurring and destroying the stage.

Not seriously. Such things are quite rare in well-developed hardware.
One of the Saturn Is had a turbopump strip its gears, and the engine just
quietly shut down. (The gear design was already understood to be marginal
and fixes were already in the works.)

Mind you, it beats the hell out of putting thirty engines in the first
stage like the N-1 did.
That was just asking for it. :-D

What was asking for it on the N1, much more than the engine count, was the
lack of full-scale ground testing of the first stage.
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