Doubting the power of the F-1

[Peter B]

Another Scott Manley video (starting up the F-1 engine) has brought out another conspiracy theorist. This one is expressing doubt that the thrust of the F-1 engines could be transmitted to the structure of the rocket through the engine gimbals. His view is that the 700+ tons of thrust pushing upwards from each engine on the gimbal structure would crush it. When asked what sort of engine thrust he could believe in, his reply was:

I don't believe it can be as much as claimed in the case of the F1 engine.  I don't attest to know the design or characteristics of the other engines that you've mentioned, the only research I've done is specific to the Saturn V and F1 engine.

There are other design features of the Saturn V that lead me to believe it was not as powerful as is claimed.  Firstly if you look at some of the more detailed pictures of the construction of the Saturn V, in particular of the thrust structure at the base of the first stage, you will notice it is constructed of relativity thin unbraced aluminium sections.  This structure is responsible for carrying the entire weight of the complete craft both on the pad and during its violent initial lift off phase.  Now bear in mind the total weight of the Saturn V in launch configuration is around some 2,900 tons!

Also bear in mind at full throttle the combined thrust from the five F1 engines is about 3,750 tons!  In essence the thrust structure is bearing more force than would be exerted if holding the weigh of a fully loaded  Gearing class destroyer!  As mentioned the thrust structure is made of an aluminium alloy and weighs about twenty tons IIRC.  It would be some mean feat of engineering if such weight could be supported by such a lightweight fabrication don't you think?

Also should be mentioned, that load would not be distributed evenly across the entire base of the structure, but rather it would be focused to the five points where the engines attach via the gimbals.

I don't understand the engineering well enough, so I can't debunk his comments. Would anyone like to have a go? Thanks!

[BertieSlack]

I don't understand the engineering well enough, so I can't debunk his comments. Would anyone like to have a go? Thanks!

I don't know about structural engineering either, but it's worth making the point (already made by Jay on an earlier thread I think) that if the F-1 engines weren't as powerful as advertised then the rocket would've just sat on the pad going nowhere since the thrust-to-weight ratio of the rocket was barely bigger than 1:1 even with the advertised spec.
Also worth remembering (hoaxnuts seldom do) that the Saturn V put 80 tons of Skylab into an orbit twice as high as the Apollo parking orbit and it achieved this without a 3rd stage burn.

[Zakalwe]

There is no case to debunk as the conspiracy nutjob is basing his case on what he thinks a structure should look like. It's classic Dunning Kruger and based on personal belief.
The proof that it worked is there in front of his eyes- the big-ass rocket lifted off (multiple times) and flew. These things are not in doubt, there are ample first-hand witness accounts as well as thousands of pieces of evidence from independent sources that verify that the rockets flew as designed. 

In basic terms, this individual does not believe his own eyes. Further, he clearly does not have the technical background to asses the strength of the, for example, thrust structure. His position is based on personal incredulity, nothing more. As he said "it would be some mean feat of engineering if such weight could be supported by such a lightweight fabrication- well, it was just that- a mean feat of engineering and one that he is clearly ill equipped to understand.

Finally, the sparse "research" that he has done is very self evident. He says "five points where the engines attach via the gimbals." The four outer engines were gimballed but the centre engine was fixed. it's a small point, but to anyone that knows the basics of the mighty Saturn V such a mistake shows how little the individual actually knows.

[smartcooky]

This is a completely nonsense claim.

Even with relatively thin lightweight materials, an extremely strong structure can be custom built where the stress points and thrust vectors are known quantities. Even Mother Nature - Engineer can make things that are much stronger than they seem.

[onebigmonkey]

"I don't believe..." is about it.

[Jason Thompson]

I don't understand the engineering well enough, so I can't debunk his comments. Would anyone like to have a go? Thanks!

I'm no expert but I will have a go!

Firstly if you look at some of the more detailed pictures of the construction of the Saturn V, in particular of the thrust structure at the base of the first stage, you will notice it is constructed of relativity thin unbraced aluminium sections.

And the whole argument fails there. Why look at some pictures? The construction of the Saturn V is very well documented. It is possible to find out precisely what alloy was used, what thickness was used, its stress and load-bearing characteristics, and so on. You simply cannot do a sensible analysis of the engineering of any device by just looking at pictures and drawings.

How is he concluding they are 'unbraced' for instance? For one thing those vertical strips on the thrust structure are there to add strength to the structure much as corrugations in card make it stronger. They are very conspicuous on every section of the Saturn V that is not a fuel tank wall. And that's just the outer skin of the structure. The internal construction is pretty darn complex.

This structure is responsible for carrying the entire weight of the complete craft both on the pad and during its violent initial lift off phase.  Now bear in mind the total weight of the Saturn V in launch configuration is around some 2,900 tons!

And since the rocket sits happily on the pad one can conclude it is more than capable of doing just that!

Also bear in mind at full throttle the combined thrust from the five F1 engines is about 3,750 tons!  In essence the thrust structure is bearing more force than would be exerted if holding the weigh of a fully loaded  Gearing class destroyer!  As mentioned the thrust structure is made of an aluminium alloy and weighs about twenty tons IIRC.  It would be some mean feat of engineering if such weight could be supported by such a lightweight fabrication don't you think?

And that's exactly what it is. His personal incredulity that it could do those things is not evidence of foul play. As with so many conspiracy theorists, his reaction to finding a gap in his understanding is not 'maybe I should expand my knowledge' but 'something fishy is going on'. Dunning Kruger effect in full swing.

Also should be mentioned, that load would not be distributed evenly across the entire base of the structure, but rather it would be focused to the five points where the engines attach via the gimbals.

And the construction of the thrust structure distributes that load so it is not focused on small points. That kind of engineering has been around for a very long time. His failure to understand it is not evidence of foul play.

If the F-1 engines were not as powerful as stated, the rocket could not get off the ground! The appropriate question to ask him would be how he thinks it got off the pad with less powerful engines.

[Von_Smith]

Another Scott Manley video (starting up the F-1 engine) has brought out another conspiracy theorist. This one is expressing doubt that the thrust of the F-1 engines could be transmitted to the structure of the rocket through the engine gimbals. His view is that the 700+ tons of thrust pushing upwards from each engine on the gimbal structure would crush it. When asked what sort of engine thrust he could believe in, his reply was:

I don't believe it can be as much as claimed in the case of the F1 engine.  I don't attest to know the design or characteristics of the other engines that you've mentioned, the only research I've done is specific to the Saturn V and F1 engine.

There are other design features of the Saturn V that lead me to believe it was not as powerful as is claimed.  Firstly if you look at some of the more detailed pictures of the construction of the Saturn V, in particular of the thrust structure at the base of the first stage, you will notice it is constructed of relativity thin unbraced aluminium sections.  This structure is responsible for carrying the entire weight of the complete craft both on the pad and during its violent initial lift off phase.  Now bear in mind the total weight of the Saturn V in launch configuration is around some 2,900 tons!

Also bear in mind at full throttle the combined thrust from the five F1 engines is about 3,750 tons!  In essence the thrust structure is bearing more force than would be exerted if holding the weigh of a fully loaded  Gearing class destroyer!  As mentioned the thrust structure is made of an aluminium alloy and weighs about twenty tons IIRC.  It would be some mean feat of engineering if such weight could be supported by such a lightweight fabrication don't you think?

Also should be mentioned, that load would not be distributed evenly across the entire base of the structure, but rather it would be focused to the five points where the engines attach via the gimbals.

I don't understand the engineering well enough, so I can't debunk his comments. Would anyone like to have a go? Thanks!

Literally thousands of people showed up to watch the launches live (and by "live" I mean *live*, in person, not just on live TV).  I think the only way you cast doubt on the F-1 is to suggest that "that big rocket you all saw" wasn't actually that heavy.

[Count Zero]

Literally thousands of people showed up to watch the launches live (and by "live" I mean *live*, in person, not just on live TV).  I think the only way you cast doubt on the F-1 is to suggest that "that big rocket you all saw" wasn't actually that heavy.

<-------------------------------------
I was one of them.  My profile picture to the left is me (middle) and my sisters visiting the pad two days before the launch.

[PDI-11]

<-------------------------------------
I was one of them.  My profile picture to the left is me (middle) and my sisters visiting the pad two days before the launch.

At 65 pixels, it is hard to tell anything. Except I can see the shadows are not parallel and therefore must be a studio fake. 

[raven]

It's like the claims the onboard computer was not enough. They never say what would be in any qualitative fashion, just that Apollo's wasn't.
But, seriously, if it wasn't and they, say, lightened the load to compensate,  wouldn't they'd need to have to secretly develop entirely new engines for the first stage? As the acceleration of the Saturn V would be all wrong if the F-1 engines were lifting a lighter rocket.

[Von_Smith]

Another Scott Manley video (starting up the F-1 engine) has brought out another conspiracy theorist. This one is expressing doubt that the thrust of the F-1 engines could be transmitted to the structure of the rocket through the engine gimbals. His view is that the 700+ tons of thrust pushing upwards from each engine on the gimbal structure would crush it. When asked what sort of engine thrust he could believe in, his reply was:

I don't believe it can be as much as claimed in the case of the F1 engine.  I don't attest to know the design or characteristics of the other engines that you've mentioned, the only research I've done is specific to the Saturn V and F1 engine.

There are other design features of the Saturn V that lead me to believe it was not as powerful as is claimed.  Firstly if you look at some of the more detailed pictures of the construction of the Saturn V, in particular of the thrust structure at the base of the first stage, you will notice it is constructed of relativity thin unbraced aluminium sections.  This structure is responsible for carrying the entire weight of the complete craft both on the pad and during its violent initial lift off phase.  Now bear in mind the total weight of the Saturn V in launch configuration is around some 2,900 tons!

Also bear in mind at full throttle the combined thrust from the five F1 engines is about 3,750 tons!  In essence the thrust structure is bearing more force than would be exerted if holding the weigh of a fully loaded  Gearing class destroyer!  As mentioned the thrust structure is made of an aluminium alloy and weighs about twenty tons IIRC.  It would be some mean feat of engineering if such weight could be supported by such a lightweight fabrication don't you think?

Also should be mentioned, that load would not be distributed evenly across the entire base of the structure, but rather it would be focused to the five points where the engines attach via the gimbals.

I don't understand the engineering well enough, so I can't debunk his comments. Would anyone like to have a go? Thanks!

Also he questions how much load an aluminum structure can support relative to its own mass.  For reference, a typical empty beer can weighs about 15 grams, yet it takes a surprising amount of force to crush it vertically without compromising the structure (by compressing the sides, for example).  An average-weight man (ca. 70ish kg) can stand on two structurally-intact empty beer cans without them buckling. 

Structure and scale matter.

[JayUtah]

I can't figure out where this guy gets the impression that the S-IC thrust structure is "unbraced." The cruciform structure whose intersection accepts the thrust of the inboard F-1 has both flanges and stringers on its web. It's the same structural principle by which a regular "schedule steel" I-beam works in building construction, only made stronger by stringers. The outboard F-1s are axially coupled more-or-less directly to the cylindrical fuselage.

The hold down anchors, which attach to the same structure, are some of the largest aluminum forgings ever made. Keep in mind this isn't just drink-can aluminum. This is aerospace-grade aluminum alloy. These alloys are, in some cases, stronger than steel. (U.K. readers please mentally adjust the spelling of "aluminum" as needed.)

I love the structural "analysis" of people who just look at something and decide it can't be strong enough for the designated purpose. The field of indeterminate statics is daunting, but mastery of it allows us to build things like rockets. It's often non-intuitive.

[Jason Thompson]

I can't figure out where this guy gets the impression that the S-IC thrust structure is "unbraced."

A combination of thinking 'looking at some pictures' constitutes serious engineering analysis, and a lack of understanding of what 'braced' actually entails would be my guess. It seems a similar phenomenon to those who insist the LM is structurally unsound when all they're looking at is the outer thermal/micrometeoroid protection layer rather than the complex structure underlying it.

The hold down anchors, which attach to the same structure, are some of the largest aluminum forgings ever made.

It always surprises me that of all the things to point out the 'obvious' weakness of, in no hoax argument I have ever come across has anyone said how 'obviously' absurd it is that the entire upward thrust of the rocket is held back by those four (comparatively) tiny clamps at the base of the rocket. Even knowing what I do and what I have learned from researching it and reading this site over the years, those little hold-down arms still look way too small to do what they do. The difference, of course, is that I understand that this is a complex system designed by specialists and my layman's skills are not enough to decide something can't work because it looks like it can't to me!

I love the structural "analysis" of people who just look at something and decide it can't be strong enough for the designated purpose. The field of indeterminate statics is daunting, but mastery of it allows us to build things like rockets. It's often non-intuitive.

That's one of the most fascinating things about they physical world to me. There's enough stuff in it that does work exactly how we would expect it to to give a decent foundation to 'intuitive' understanding of things, but there is so much that just doesn't work as we would expect it to at first glance. It's those things I fid the most interesting and the most rewarding to look into. Unfortunately s few seem unwilling to extend their awareness to the notion that their understanding may be incomplete.