Hoax? - Lunar Launches - Too Fast

[najak]

@TimberWolfAu:

How long before you are ready to continue with your analysis of my 2nd round of Apollo 16 work.  I presented "best attempted image analysis motion" and also the "worst case, assuming some error" - and the worst case still shows 2.36x the rated thrust.  (vs. 2.57x)

I'm interested to know your feedback and thoughts on this.  And thank you again for your involvement and work here.

[JayUtah]

Your answer is "it's too complex to explain" with no specifics other than "transients can produce some variance".   Yes, there is variance.

The phenomena at work are more complex than you care to consider. I asked you some questions to start a discussion regarding the complexities, and you said you didn't care—"basic physics" should always apply.

Is there a uniform, one-size-fits-all model for startup transients? The source you got some of your graphs from gave you the answer. What was it?

But we're talking about CONSISTENT STEADY PROLONGED VARIANCE for ALL 3 Launches.     One Second is a LONG time, for the types of variance discussed with "transient performance at launch".

How do you know that?

Please attempt to describe (and source) where there is ANY claim in rocket science that this transient behavior can produce a prolonged 2.5x output, while spitting out unburnt fuel right after ignition.

Straw man. Ignition transience is one factor. Local conditions at the nozzle exit plane is another.

It seems you can't...

Straw man. You want there to be a simple answer.

No amount of "Rocket Science complexity/variance" can Break Newton's 2nd Law in the context of a closed-system (at least not measurably at these speeds).

No, Newton's second law is not expected to explain everything you see in any system.

Are you really suggesting that the average Thrust for 1st second was NOT ~1200 kN average, while the motion curve indicates clearly ~1200 kN of near steady force?

Which "motion curve" are you referring to?

If there were a reliable way to obtain 2.5X thrust output at launch - this would be astonishing, big news - clearly stated.   But we have nothing of the sort, do we?

Speculation.

Ignition instability in all cases, including ignition transients, is generally something desirable to avoid. Apollo did not require or rely upon any momentary thrust excitations (with the notable exceptionof the Marquardt 100-lbf jets). There is a lengthy history of Bell's initial attempts to reduce the transient for the APS, leading to NASA selecting Rocketdyne as a backup engineering contractor for the thrust chamber and the injector plate. Your ongoing desire to downplay, sidestep, or reimagine the actual behavior of rocket engines doesn't change reality.

Momentary additional thrust produced by confining the exhaust to develop a higher proportion of pressure thrust has historically been something we have gone to great lengths to avoid or minimize, since it poses a back-pressure hazard to the engine itself. Thus the "fire in the hole" configuration for the APS was a matter of some concern in the design. Demonstrating that ignition was safe under those circumstance was a major mission goal of Apollo 5. Any momentary performance improvement or degradation is irrelevant in the overall operation of the system.

[najak]

1. Apollo did not require or rely upon any momentary thrust excitations.

2. Your ongoing desire to downplay, sidestep, or reimagine the actual behavior of rocket engines doesn't change reality.

3. Momentary additional thrust produced by confining the exhaust to develop a higher proportion of pressure thrust has historically been something we have gone to great lengths to avoid or minimize, since it poses a back-pressure hazard to the engine itself. Thus the "fire in the hole" configuration for the APS was a matter of some concern in the design. Demonstrating that ignition was safe under those circumstance was a major mission goal of Apollo 5. Any momentary performance improvement or degradation is irrelevant in the overall operation of the system.

Great, thanks for adding some specifics.  I am gleaning the following:

#1: There was no intention of making use of start-up transients for Apollo AM.  As usual, they were trying to minimize the amount of impact.

#2: I'm not trying to reimagine anything here.  I'm not saying "the motion is explained by Newton's 2nd law"; I'm saying it's CONSTRAINED to obey this law... the explanation of the acting forces is the Rocket Science. 

So far, there have been zero indications given that Rocket Science is even TRYING to explain at sustained 1 second steady 2.5X thrust output with the inefficiency unburned fuel for the first 0.8 seconds.

#3: Again, Apollo, the same as most of similar contexts, is trying to minimize these less predictable transients.  So surely they weren't planning on a setup that produces 2.5X the rated thrust resulting from transients.

===
This leaves the primary issue fully unresolved, which is that this AM demonstrated a near-steady acceleration for 1 second that was 2.5X the Rocket's max thrust rating.

Are you really suggesting that these "transients" which Apollo did it's best to minimize would reasonably be able to provide a steady 1 second for 2.5X the thrust, with the inefficiency of unburned fuel?

If so, please explain why Apollo was not ABLE to avoid it so badly.

[JayUtah]

There was no intention of making use of start-up transients for Apollo AM.  As usual, they were trying to minimize the amount of impact.

No, just the unpleasant side-effects of ignition transients, which can sometimes result in longer-term instability or, in the worst case, damage to the engine. That the thrust itself momentarily varies doesn't matter. Thrust fluctuation at startup is inevitable. What matters is that the transient is qualitatively harmless, not that it is quantitatively mitigated. Bob Braeunig understood this, so maybe you owe him an apology.

Guidance and control systems literally don't care about the magnitude of applied thrust, since they integrate acceleration measured directly to update the state vector. Out-of-tolerance thrust over a prolonged period may indicate engine failure, and so chamber pressure is measured in order to detect that. But the thrust is expected to vary over the short term, and so no part of the system requires it to stay steady. There is no inherent need to eliminate the thrust effect from otherwise unremarkable unstable combustion.

I'm not trying to reimagine anything here.

You're trying to imagine that the outlying effects of rocket engines—if they really existed—should be harnessed to improve performance. Since you find no evidence that this occurs, you imagine that the effects must be fictional. Because you're only comfortable with simple explanations, you need a way to make the real-world complexity go away.

I'm not saying "the motion is explained by Newton's 2nd law"; I'm saying it's CONSTRAINED to obey this law... the explanation of the acting forces is the Rocket Science.

No, that's a complete departure from real physics. No one law constrains a system so as to preclude the parallel effects of other laws.

So far, there have been zero indications given that Rocket Science is even TRYING to explain at sustained 1 second steady 2.5X thrust output with the inefficiency unburned fuel for the first 0.8 seconds.

Except, of course, for the indications you're frantically trying to handwave away.

Again, Apollo, the same as most of similar contexts, is trying to minimize these less predictable transients.  So surely they weren't planning on a setup that produces 2.5X the rated thrust resulting from transients.

No, that does not follow. Back pressure is a putatively dangerous condition because it may damage the engine. Ignition transience is a putatively dangerous condition because it may damage the engine or result in long-term unstable thrust, which then risks damaging the engine. If the putative dangers of these phenomena are shown through testing not to be a factor, then the benign effects upon thrust are irrelevant. The dangers of ignition transients and other combustion instability can be investigated through static firings. The dangers of back pressure in this one case can only be tested in flight test, which occurred on Apollo 5. There was little need to investigate it further, since we simply avoid the "fire in the hole" scenario altogether—or did, until SpaceX attempted hot-staging. It took them a couple of tries to get it right too.

Alleging NASA to have "failed" by not having reduced the one effect of engine operation that defeats your naive expectation is silly. Your argument now has the tail wagging the dog.

[najak]

Yes, and Jarrah showed me his side of the story with screenshots.

I'm sure he's quite anxious to present a rosy picture of what happened there. What happened is that while trying to show that Apollo's radiation protection was inadequate, he argued himself into a corner from which he could not extract himself. At the time, he did not know calculus and it became obvious that he could not work through the space weather data properly. That ended with one of the long, profanity-laden rants for which he used to be so justly infamous. Then Jarrah deleted all his posts there, so that no one else could follow the real argument. Since then he has routinely lied about it.

FYI.  Jarrah is watching this forum, and posted a heated response to you in the MLH Facebook group.

https://www.facebook.com/share/p/19Sd536QAs/

[JayUtah]

FYI.  Jarrah is watching this forum, and posted a heated response to you in the MLH Facebook group.

Good for him.

[najak]

No, that's a complete departure from real physics. No one law constrains a system so as to preclude the parallel effects of other laws.

Are you suggesting that this AM is launching with an apparent 2.5X acceleration without actually having a 2.5X Net Force acting on it?
(i.e. that other "laws" are achieving this acceleration without apply a Net Force).

So please tell us about the "other laws" that are acting in Parallel -- and that you are implying will actually OVERRIDE/BREAK Newton's 2nd Law within this context?

[JayUtah]

Are you suggesting that this AM is launching with an apparent 2.5X acceleration without actually having a 2.5X Net Force acting on it?

Actually no, I'm saying that plugging simplistic numbers into Newton's second law to produce your expectations is naive. The separate notion that some "basic physics" law must always fully govern or constrain observable behavior is an academic disagreement.

[najak]

Actually no, I'm saying that plugging simplistic numbers into Newton's second law to produce your expectations is naive. The separate notion that some "basic physics" law must always fully govern or constrain observable behavior is an academic disagreement.

Newton's 2nd Law IS SIMPLISTIC.  You have to plug in a NET FORCE.

What are the actor applying forces on this AM?
1. Gravity, 1.62 down
2. Rocket Thrust, up
3. Undesirable "Fire in the Hole" exhaust compression?  (which Apollo apparently has minimized, so should be nominal),  Up.
4. {Got any other ideas?}

What other Force Actors am I missing?  Please enumerate and provide a force amplitude range that you are proposing.

In the end, you sum the contributing forces to arrive at a Net Force, which then feeds into Newton's 2nd Law, to produce an estimated Acceleration/motion.

Do you agree?  If not please, be specific with corrections.

===
#2 and #3  (and #4?) - can have complex behavior to explain how these forces were generated... but in the end, Newton's Unbreakable (in this context) Law mandates that the resulting acceleration will directly correlate to the summed up Net Force.

================================
=== SELF-CORRECTION ================

And I just realized one mistake I've been stating regarding the thrust ratios...   it's 2.5X NET FORCE difference (which includes Gravity) --   The actual Rocket Thrust ratio required would be less than 2.5X, as follows:

Predicted Rocket Thrust = 3.01 m/s^2
Gravity counters this with 1.62 m/s^2
Resulting in predicted Accel = 1.39 m/s^2

Thus for it to instead go 3.57 m/s^2
The Rocket Thrust must then provide 2.18 m/s^2 more thrust than the engine rating at steady state.
Thus the Rocket Thrust required to achieve the Observed motion is 1.724 X the rated engine thrust... not 2.57x.

So the issue to be solved here isn't as bad as I had been stating (which seems to have escaped everyone's notice here as well).
This is why I like "protagonists" in my research -- the scrutiny helps me to weed out my mistakes.  (in this case, I had to find my own)

Revised statements are:
15.6kN Rocket thrust rating, must produce 26.9kN instead, to achieve the observed Acceleration/Motion.
(Or, this force needs to come from some other acting force.)

The excess thrust being witnessed is 11.3 kN, or about 72% above the rated Rocket thrust.

I will correct my source KB doc, ASAP.

[JayUtah]

What other Force Actors am I missing?

All those that aren't the rated thrust of the engine. Additional pressure thrust produced by containing the exhaust is one of those. Fluctuations in thrust that arise from combustion instability is another.

This is why I like "protagonists" in my research -- the scrutiny helps me to weed out my mistakes.

Agreed. Whether discussion provides a correction directly or leads you to correct yourself, good faith debate is profitable.

[najak]

FYI.  Jarrah is watching this forum, and posted a heated response to you in the MLH Facebook group.

Good for him.

Jarrah posted a link to the IMDB forum you mentioned, his threads are still visible. The only messages of his deleted were deleted by the administrator.  His screenshots show this, but you continue to claim otherwise.  On what evidence do you present your assumptions as fact?

[najak]

All those that aren't the rated thrust of the engine. Additional pressure thrust produced by containing the exhaust is one of those. Fluctuations in thrust that arise from combustion instability is another.

Great those are the only two I've ever heard proposed.  Got any other ideas?

For these two, can you estimate what you think the maximum "added upwards thrust" could safely be? 

And for how long would this upward thrust persist? (a full second?) 

And for this 1 second, should we expect it to be steady (near constant) for the first 1 second, then cut out immediately after that?

Agreed. Whether discussion provides a correction directly or leads you to correct yourself, good faith debate is profitable.

This is the first statement you've made where I felt some warmth, rather than your disdain.  Thank you for this.

I'm liking the course this debate is taking now; it's seeming to be productive, maybe fruitful.

[JayUtah]

Jarrah posted a link to the IMDB forum you mentioned, his threads are still visible.

The IMDb forums were discontinued and removed in 2017. Here is our contemporaneous discussion of the last time this issue was raised.
https://apollohoax.net/forum/index.php?topic=759.0

[JayUtah]

Great those are the only two I've ever heard proposed.  Got any other ideas?

What's wrong with those?

For these two, can you estimate...

Not without work that I won't be disposed to do until after the holiday. Pressure thrust is surprisingly large, in general. And that's with no fluid containment.

This is the first statement you've made where I felt some warmth, rather than your disdain.  Thank you for this.

You're welcome.

[najak]

For these two, can you estimate...

Not without work that I won't be disposed to do until after the holiday. Pressure thrust is surprisingly large, in general. And that's with no fluid containment.

No rush.  I hope you enjoy your holiday.

To what extent was the AM's thrust nozzle was sealed?

Do we have any design documents from NASA that show how this came together?  I'm finding very limited blueprints.  Where is the rest?

What do you mean by "with no fluid containment"?  (looked up the phrase with relation to rockets, and no hits)