Quick question about rocket engines

[Luke Pemberton]

My thoughts too. One of the reasons I like this forum is that I get to read about real engineering from real engineers. I often have questions but never ask as I feel slightly dumb, so just pick up snippets here and there. The utter scale of Apollo, not just the Saturn V, is mind blowing.

[mako88sb]

Just seen your second edit. I wish I had Kelly's book handy because he explained it better if I recall right. It's been awhile since I read it though so maybe I'm off about that to.

I bought Tom Kelly's book but I still haven't had the chance to read it.  I certainly plan to get to it.

I was only familiar with how the design of the LEM evolved from watching the Spider episode of FTETTM which I found fascinating. Some of the problems that came up are of course shown in that episode but reading the "Problems, Problems" chapter of Tom Kelly's book really showed the caliber of the people involved with the project. For example, one of the titanium tanks failed during testing and trying to determine why it happened proved to be very difficult and concerning. They were able to figure out eventually that the pads used to  prep the titanium surface prior to welding were pretty costly so they decided to re-use them after a thorough washing. However, there was enough residual detergent left from washing that it actually had an adverse affect on the surface being prepped which led to the failure. Just one example of the challenges they had to overcome.

[Luke Pemberton]

They were able to figure out eventually that the pads used to  prep the titanium surface prior to welding were pretty costly so they decided to re-use them after a thorough washing. However, there was enough residual detergent left from washing that it actually had an adverse affect on the surface being prepped which led to the failure. Just one example of the challenges they had to overcome.

These are the snippets of information that make Apollo so enjoyable to read about, and they make me think how can anyone believe there was a hoax? You can't make this stuff up.

[smartcooky]

Just seen your second edit. I wish I had Kelly's book handy because he explained it better if I recall right. It's been awhile since I read it though so maybe I'm off about that to.

I bought Tom Kelly's book but I still haven't had the chance to read it.  I certainly plan to get to it.

I was only familiar with how the design of the LEM evolved from watching the Spider episode of FTETTM which I found fascinating. Some of the problems that came up are of course shown in that episode but reading the "Problems, Problems" chapter of Tom Kelly's book really showed the caliber of the people involved with the project. For example, one of the titanium tanks failed during testing and trying to determine why it happened proved to be very difficult and concerning. They were able to figure out eventually that the pads used to  prep the titanium surface prior to welding were pretty costly so they decided to re-use them after a thorough washing. However, there was enough residual detergent left from washing that it actually had an adverse affect on the surface being prepped which led to the failure. Just one example of the challenges they had to overcome.

And that brings up an interesting issue.

Titanium manufacture in the 1960's was nowhere near as good as it is today. There was potential for defects in titanium that could, and in fact did lead to structural failure in high stress components. In the famous "Sioux City Fireball", a DC10 crashed after it lost all three hydraulic systems when the No 2 (tail) engine exploded. This was caused when the titanium fan-disk in the No 2 (tail) engine flew apart, severing all three hydraulic lines at a point where they came close together near the horizontal stabiliser.

The root cause of the fan-disk failure was almost undetectable micro-fractures caused by microscopic oxygen and nitrogen bubbles which were left in the titanium when it was manufactured. Admittedly, the DC10 scenario was also caused by many years of fatigue, but I image the stresses and strains on the components in a Saturn V are far greater then those normally encountered on a passenger aircraft.

AIUI this accident led to a change in the titanium manufacturing process for aerospace applications. It is now remelted several times in a vacuum to draw out any gasses within.   

[Allan F]

Reading about the injector for the F1-engine - it was apparently made from copper. Was that to utilize the heat conductive properties in order to avoid uneven heating and possibly warping of the injector? A higher-melting metal would be the layman's choice, but then there's the liquid oxygen cooling it . . .

[Bob B.]

I often have questions but never ask as I feel slightly dumb

I don't believe anyone here would make the mistake of thinking you dumb, Luke.

[Luke Pemberton]

I don't believe anyone here would make the mistake of thinking you dumb, Luke.

Thanks, although I was not fishing for compliments. There are people here who are far more versed in Apollo and their understanding leaves me in awe (no connection to that awe ).

[Allan F]

I don't believe anyone here would make the mistake of thinking you dumb, Luke.

Thanks, although I was not fishing for compliments. There are people here who are far more versed in Apollo and their understanding leaves me in awe (no connection to that awe ).

The difference is that most people here know what they DON'T know - meaning they understand the limitations of their own specialty.

[Bob B.]

One of the great things about this forum is that we've got people knowledgeable in so many disciplines.  If I encountered an HB away from this forum, I'm confident that I could hold my own in a debate on almost any topic.  But when I'm here I know when to shut up and let the real experts handle things.  When it comes to things like photography, optics, video, and communications, I know that I'm way outclassed by people like Jay, Dwight and ka9q.  Over the years I've learned to be more patient and to wait for my opportunities to contribute something of value to the discussion.

[Al Johnston]

The root cause of the fan-disk failure was almost undetectable micro-fractures caused by microscopic oxygen and nitrogen bubbles which were left in the titanium when it was manufactured. Admittedly, the DC10 scenario was also caused by many years of fatigue, but I image the stresses and strains on the components in a Saturn V are far greater then those normally encountered on a passenger aircraft.

AIUI this accident led to a change in the titanium manufacturing process for aerospace applications. It is now remelted several times in a vacuum to draw out any gasses within.   

This brings back memories.

For turbine discs the critical size of HID (High Interstitial Dislocation) was undetectable during the manufacturing process, so only metal that passed through the procedures faultlessly wound up in them. Any deviations in melting or handling meant it was downgraded to less demanding final uses.

[Luke Pemberton]

When it comes to things like photography, optics, video, and communications, I know that I'm way outclassed by people like Jay, Dwight and ka9q.

That's how I feel. When I first joined the hoax debate I made a conscious decision not to try and become a jack of all trades, but chose areas where I knew I could develop my understanding based on my experience and own credentials. That decision was largely based on reading these boards and seeing the writing of others. I would never try to emulate Jay, sts60, ka9q, Dwight and many others. They've been there, done it  and worn the T-shirt and have years of experience that I could never gain.

Over the years I've learned to be more patient and to wait for my opportunities to contribute something of value to the discussion.

With fattydash and the lost Eagle I knew I could only play an extra, but with Adrian and Romulus I piped in more as (a) I spotted contradictions in their argument (b)I knew what I was talking about.

[Bob B.]

(b) I knew what I was talking about.

That much is obvious, Luke.

I've always had to struggle with the confidence thing.  It's true that I have an engineering degree, but that was in civil engineering.  There is nothing in my formal education or work experience that qualifies me as a expert astronautics or rocket dynamics.  Everything I've learned about those subjects has been self taught.  I've got no one testing or grading me to provide the confirmation that I know what I'm doing.  As such, I've always looked for ways to test myself.  The best way I've found to do this is to take a real life example and see if my computations replicate the result.  I've tested my techniques using a wide range of data, both American and Soviet, and have gotten excellent results.  As my confidence grew, I started to test different aspects of Apollo.  I've since computed the trajectories, simulated the launches/landings, and verified just about everything I could.  All of my computations and simulations are spot on with the Apollo data.  This leaves me with no reason to doubt my methods or Apollo's authenticity.

It is the self-test part that the conspiracists leave out.  When they apply their rudimentary understanding of physics to Apollo and come up with contradictory results, they immediately claim that there's something wrong with Apollo.  They never seem to consider that it's their computations and, more likely, their understanding that are wrong.  When I get different results, the first thing I think is "what did I do wrong" and I set out to find my mistake.  Real learning occurs when a person can recognize their mistakes, correct them, and not repeat them.  Most conspiracists refuse to acknowledge their mistakes and refuse to accept correction.  That is willful ignorance, and is the thing I find most frustrating when dealing with them.

[Luke Pemberton]

That is willful ignorance, and is the thing I find most frustrating when dealing with them.

Absolutely, and that is why I prefer to be patient when dealing with them. It would be hypocritical of me to take a position from which I know little about in an attempt to boost my own standing.

I did comment on a photo thread the other day, but I was shown to be wrong. I accepted my 'wrong' graciously. That's an important aspect of this small community, being prepared to be wrong and moving on, unlike them who will never back down.

[Bob B.]

I accepted my 'wrong' graciously. That's an important aspect of this small community, being prepared to be wrong and moving on, unlike them who will never back down.

We're all fallible.  Although making a mistake may sometimes make us feel dumb, it's just part of the learning process.  When I struggle through a problem and have to resolve mistakes, I often feel I learned more than when I do everything right the first time.  For instance, I can pull an equation out of a book, apply it to a problem, get the right answer, and I move on.  However, if the equation doesn't give the answer I expected, then I have to start digging deeper.  I might have to re-derive the equation to figure out how I misapplied it.  I emerge with greater understanding than had the mistake not occurred.

A conspiracist's refusal to acknowledge and correct mistakes is one of the most telling signs of just how insincere they are.  They portray themselves as truth seekers, but their actions show that they seek only one outcome.

[mako88sb]

They were able to figure out eventually that the pads used to  prep the titanium surface prior to welding were pretty costly so they decided to re-use them after a thorough washing. However, there was enough residual detergent left from washing that it actually had an adverse affect on the surface being prepped which led to the failure. Just one example of the challenges they had to overcome.

These are the snippets of information that make Apollo so enjoyable to read about, and they make me think how can anyone believe there was a hoax? You can't make this stuff up.

Yeah, I know what you mean. Every book I've read by/about the astronauts involved has some fascinating details that as you say, can't be made up. I've tried to encourage hoax believers to read some of these accounts but always get the "if I want to read science fiction I'll....yada yada yada". Oh well, their loss.