Apollo 11 Lunar Lander Pre-Launch

[JayUtah]

...with the earlier (unmanned) missions.

The word you're hunting for is "flight test."  The RCS system was extensively flight-tested prior to attempting a landing mission.  Problems were discovered and fixed, and the whole system was validated as fault-tolerant.  In the history of the Apollo spacecraft, no mission of any kind was aborted or scrubbed due to RCS failure.

It should be noted A11 was the only mission to that time to employ deflectors. It would interesting to know how some of these prior (less significant) anomalies would have had on a ship with deflectors.

And we've been through that at length.  The only reason you give for the plume deflectors being some sort of problem is your willfully uninformed fearmongering.  Your own sources contradict your claim that jets always had to be fired in pairs, and that to do otherwise would create a positive feedback loop and vehicle instability.  After realizing your source covered only one tiny corner case, you tried to argue it somehow had to be a universal problem.  But the mathematics in your own source entirely preclude that.

Why do we have to keep returning to this?  Because you refuse to admit your error.  Despite your critics having shown a deep understanding of the problem and its solution, and despite their having proved the correctness of their position -- from your sources -- to a mathematical degree of certainty, the best you can manage is that your critics have only "reasonable" points, and that they must somehow still be laboring under misplaced faith.  Your program of overt, ignorant denial is not going to impress this audience.  If you can't forthrightly admit you got something plainly wrong, then others have very little incentive to engage you in any sort of discussion.  They will have correctly realized that you are more interested in pretending to be right than in actually knowing what's true.

[bknight]

Happy Holidays Everyone,

I checked and I believe I was thinking about Apollo 5 and 9 having significant issues with the RCS's. But looking at the Experience Report it appears the most significant issues/anomalies were with the earlier (unmanned) missions. This report goes through many of the RCS mission anomalies right up to Apollo 11 (which btw had an 18 minute partial failure)  It should be noted A11 was the only mission to that time to employ deflectors. It would interesting to know how some of these prior (less significant) anomalies would have had on a ship with deflectors. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730017174.pdf

Merry Christmas

Define 'significant'.

Can you please explain how post-mission reports that identify issues  that were corrected during the missions somehow means that the missions didn't happen?

Have you realised that that the RCS issues identified in the report you linked to were not on the LM?

Only if he read it.

[jr Knowing]

Hi Guys,

Not quite sure what you guys are reading. The question that was asked by a poster was "did any RCS fail on any mission"? (Not on an LM.) The link I referenced is the Apollo Experience report for the RCS's. It lists the Apollo missions in which the RCS's were used/and or tested.

And to answer some posters, just because something exists or stated doesn't mean it is true, right, or correct. If, for instance, you believe, according to the government, the inflation rate in the US has been 1.5 percent annually for the last ten years carry on. But if you understand how things can be manipulated ie you are being lied to, you will know the government has changed the methodology numerous times over the years to ensure an appearance of a low number. Believe it or not, the real inflation rate, according to 1980 methodology, over the last 10 years has averaged 10 percent annually. Got to go now. Big dinner date. Two can dine for $4.99. I mean $8.99. I mean $12.99. I mean, well you know what I mean. (the second chart on the page)  http://www.shadowstats.com/alternate_data/inflation-charts

[JayUtah]

The question that was asked by a poster was "did any RCS fail on any mission"? (Not on an LM.)

And your answer was that RCS jets had failed twice prior to Apollo 11.  Do you concede that your answer was wrong?

Your special concern has been the LM RCS, specifically the claim that the plume deflectors made it an unstable craft in the face of diminished RCS capability.  It is not therefore inappropriate for your critics to apply your answers to that special concern.  Do you agree that testing shows the LM RCS to have been suitably reliable?  Do you agree that this makes any adverse effect from the plume deflectors less a danger?

...you believe, according to the government, the inflation rate...

And if econometrics had anything to do with this discussion your post would merit an answer.  Once again you're deflecting calls for intellectual responsibility by bringing up irrelevant new subjects.  Your critics are not simply relying on the government to assure them Apollo worked as functioned.  They are relying on their demonstrated expertise in the well-established sciences that apply to the problem.  If you're quite finished trying to change the subject (again!), will you admit that you are wrong regarding the RCS and the plume deflectors?

[bknight]

My question should have addressed just the LM, but I can't take that back.  However all the CSM/LM issues were not SIGNIFICANT, but did warrant some reconfiguring or redoing the electronics.  If one reads the document that jr provided, one notices that the RCS system worked nominally but did have some minor issues that DID NOT AFFECT the missions.  That should be sufficient for you jr.

[nomuse]

Bah again. All this "we can't really know"/"We're all being lied to" stuff -- both in context with the claims he's trying to make about the RCS with or without plume deflectors and this latest off-topic bit about inflation -- only support what I said earlier.

Scientific facts are testable. That's what makes them science.

Word pictures, on the other hand, are fuzzy. "Inflation" has a wealth (sorry...that was totally unintentional) of meanings. If you haven't rigorously defined the statistical models in question you can't claim they conflict. You can only agree that different sortings of the data can give different interpretations.

All of this nib-nobbing about the RCS is the same; instead of going to the math, Knowing is latching on to every adjective, qualification, and outright weasel word in order to try to make it look like someone, somewhere, is lying.

[Jason Thompson]

And to answer some posters, just because something exists or stated doesn't mean it is true, right, or correct.

There it is, the single statement that essentially puts the goalposts of your discussion on wheels. Now you can use this statement to decide, entirely arbitrarily, which sources you accept and which you don't.

However, the fact remains that you brought up a document as evidence for your assertion that the plume deflectors rendered the LM unstable which in fact mathematcially proves exactly the opposite. Again I ak you to apply that simple equation and prove your assertion using it. If you cannot, admit it and withdraw the argument.

[JayUtah]

Now you can use this statement to decide, entirely arbitrarily, which sources you accept and which you don't.

Again why I limited my use of materials to those he had presented himself.  I can certainly bring to bear many resources, but if one says "Here are my authoritative documents," and I can show him where in those documents his claims are contradicted, then it makes it harder for him to say, "Yeah, I don't accept that as authoritative, and that doesn't mean it's true."

However, the fact remains that you brought up a document as evidence for your assertion that the plume deflectors rendered the LM unstable which in fact mathematcially proves exactly the opposite.

And it looks like he's trying hard to make the math go away.  Because Newtonian physics is so much like modern econometrics!  Indeed, the equation that's proving to be his Waterloo is nothing more than the literally centuries-old definition of torque.  It's not going to change tomorrow.  It's not something the government can lie about.  It's not something that's made up.  It was, in fact, discovered.  It's an inherent property of our physical universe.  Subsequently he thinks he can gaslight away others' knowledge of how the universe is observed to work.  He's seems so desperate to avoid having to admit he was wrong that he's trying to make the whole concept of wrong go away altogether.

[jr Knowing]

Man, you guys are a tough bunch. 

It wasn't even my intention to argue more about the RCS's. Just trying to help out another poster with some info. Yes the CSM RCS's cones were not ripped off on liftoff according to Apollo documentation. My point was why would NASA risk this even if there was a slight chance of problems? It would not be the first time a rocket hasn't remained intact through launch. And yes, according to Apollo documentation, there was not a complete absolute failure of an RCS engine. However, according to Apollo documentation, there were partial failures and a myriad of problems during the RCS development. Even Apollo 11 had an 18 minute partial failure. Again, using Jay's analogy, I for sure would not want to lose my steering for 18 minutes down a desolate, dark road.

And as for the deflectors, if you examine some of the early anomalies (such as certain engines running at sub par performance), it would raise certain concerns of the ability of the ship remaining stable through its mission with the addition of these (untested A11) deflectors.  (and before anyone questions whether they were tested for A11, documentation (what little there is) states NASA decided to go with the deflectors untested because testing would have meant postponing the launch for 6 weeks and bringing LM back to Production and Assembly. Seems unbelievable to me but it is the only answer to how those deflectors showed up after Saturn mating. And to be clear, documentation states the deflectors were somehow securely attached on the launchpad and not during Assembly/mating process. Added weight and changing the steering dynamics all literally last second, not to mention re-wrapping the ship in new insulation. I guess it is plausible.)

Again, I am not looking to argue. I have agreed that, according to NASA, no RCS cones were ripped off on liftoff, and there were no complete RCS failures. And it is plausible, albeit questionable (in my mind), that LM's (untested) makeover could have occurred on the launchpad.

[JayUtah]

Man, you guys are a tough bunch.

Yes.  Can you rise to the standard?

It wasn't even my intention to argue more about the RCS's.

No, it was your intention to bury your ignorant mistakes regarding spacecraft guidance and control by bringing up space suits as a distraction.  We are not finished discussing the lunar module RCS.

My point was why would NASA risk this even if there was a slight chance of problems?

And your point was addressed.  Admit your fears were naive and uninformed.  Or conversely, address the explanation you were given.

And yes, according to Apollo documentation, there was not a complete absolute failure of an RCS engine.

A carefully reworded straw man that avoids you having to walk back your claims.  You seem unwilling to admit error, no matter how slight.

However, according to Apollo documentation, there were partial failures and a myriad of problems during the RCS development.

That's what development means.

Even Apollo 11 had an 18 minute partial failure. Again, using Jay's analogy, I for sure would not want to lose my steering for 18 minutes down a desolate, dark road.

Not my analogy.  How often do you reckon the RCS is used in any particular Apollo mission?  Given what you have been shown regarding the degraded operation modes in the RCS, how did you reckon that a "partial" failure is a critical problem?  You've shown no talent at engineering risk assessment so far.

And as for the deflectors, if you examine some of the early anomalies (such as certain engines running at sub par performance), it would raise certain concerns of the ability of the ship remaining stable...

No.  You're simply repeating your ignorant suppositions.  You were shown -- again, in your own source -- the mathematics that governs the stability of the lunar module with the plume deflectors in place.  You are patently unable to reconcile your claims with those mathematics.

On this point you are plainly and provably wrong.  Your unwillingness to admit that error makes it unlikely anyone will take you seriously on any further topic you raise.  Simply admit you're wrong.

And to be clear, documentation states the deflectors were somehow securely attached on the launchpad and not during Assembly/mating process. Added weight and changing the steering dynamics all literally last second, not to mention re-wrapping the ship in new insulation. I guess it is plausible.)

You've provided no evidence for its implausibility or supposed dangers except for ignorant supposition.  You have thoroughly ignored the experience and explanation of people who do this for a living in favor of your uninformed speculation.  The question is not merely whether your critics have made a "plausible" point.  Your critics have explained to you how spacecraft are actually built and deployed, things you didn't previously know.  You want us to respect your ignorance as equally valuable and valid as knowledge.  Simply admit you were unaware of how spacecraft are actually designed, built, and flown.

Again, I am not looking to argue.

Then simply admit you made a mistake.  Stop trying to argue passive-aggressively.  You clearly do want to argue, but you don't want to be responsible for arguing from a position of fact and knowledge.  This audience will not validate your ignorance.  Acknowledge that.

And it is plausible, albeit questionable (in my mind), that LM's (untested) makeover could have occurred on the launchpad.

Since your mind is uninformed and unwilling to admit any error it makes, what does it matter what it questions?  Simply concede your errors in plain language and all this unpleasantness will go away.

You simply can't do it, can you?  You can't take the intellectually mature step of saying "I was wrong about the lunar module's RCS issues."

[apollo16uvc]

You are the participant who keeps changing the subject. It would be better if we began and finished one subject at a time, preferable in their own thread. Several of the topics discussed here deserve their own thread.

[jr Knowing]

Hi apollo16uvc,

I agree that some of these topics deserve their own thread. I was just tempted to post something in response to Jay which would have convoluted things even more.

Jay, I will leave it at this. You seem to question the importance of RCS’s during the mission by suggesting they are not used that often in that, for instance, an 18 minute failure isn’t critical. By your comments, I don’t think you know how many times the RCS’s are used. During the A11 mission, the RCS’s were used over 5000 times in bursts up to 40 seconds. Virtually every thing the LM did after separation required the RCS’s.

[nomuse]

Man, you guys are a tough bunch. 

It wasn't even my intention to argue more about the RCS's. Just trying to help out another poster with some info. Yes the CSM RCS's cones were not ripped off on liftoff according to Apollo documentation. My point was why would NASA risk this even if there was a slight chance of problems? It would not be the first time a rocket hasn't remained intact through launch. And yes, according to Apollo documentation, there was not a complete absolute failure of an RCS engine. However, according to Apollo documentation, there were partial failures and a myriad of problems during the RCS development. Even Apollo 11 had an 18 minute partial failure. Again, using Jay's analogy, I for sure would not want to lose my steering for 18 minutes down a desolate, dark road.

And as for the deflectors, if you examine some of the early anomalies (such as certain engines running at sub par performance), it would raise certain concerns of the ability of the ship remaining stable through its mission with the addition of these (untested A11) deflectors.  (and before anyone questions whether they were tested for A11, documentation (what little there is) states NASA decided to go with the deflectors untested because testing would have meant postponing the launch for 6 weeks and bringing LM back to Production and Assembly. Seems unbelievable to me but it is the only answer to how those deflectors showed up after Saturn mating. And to be clear, documentation states the deflectors were somehow securely attached on the launchpad and not during Assembly/mating process. Added weight and changing the steering dynamics all literally last second, not to mention re-wrapping the ship in new insulation. I guess it is plausible.)

Again, I am not looking to argue. I have agreed that, according to NASA, no RCS cones were ripped off on liftoff, and there were no complete RCS failures. And it is plausible, albeit questionable (in my mind), that LM's (untested) makeover could have occurred on the launchpad.

You have no idea what point you are trying to make, do you? You are just throwing paint at a wall and hoping you'll get a Jackson Pollock out of it.

Did NASA test or didn't they? Heck, do you even understand what "test" means? Do you understand the principle of iterative design?

No, honestly...I can't tell if you have a point to make. If there is one, it is well hidden.

[JayUtah]

I was just tempted to post something in response to Jay...

No, it's not my fault you can't stick to the subject.

Jay, I will leave it at this.

No, you don't get to "leave it at that" and move on.  It's clear you don't want attention focused on your errors, which means that's where I'm going to focus my attention until you give satisfactory answers.  You have made several plain errors regarding the lunar module and its RCS that you simply refuse to acknowledge.  Why are you so deathly afraid to admit even the slightest error on your part?  The math in the document you insisted we examine is unmistakable and unforgiving.  Why are you so afraid of it?

You seem to question the importance of RCS’s...

Not a claim I made.

...suggesting they are not used that often in that, for instance, an 18 minute failure isn’t critical.

No, I have made no such claim.  I'm questioning your claim that an 18-minute partial failure should have been more a concern than it was.  My question was for you to lay out your rationale.  Instead you have tried to shift the burden of proof.

Here is the discussion of this "critical" failure in the LM.

16.2.12 Thrust Chamber Pressure Switches

The switch used to monitor the quad 2 aft-firing engine (A2A) exhibited a low response to jet driver commands during most of the mission.  During an 18-minute period just prior to terminal phase initiation, the switch failed to respond to seven consecutive minimum impulse commands.  This resulted in a master alarm and a thruster warning flag, which were reset by the crew. The engine operated normally, and the switch failure had no effect on the mission. The crew did not attempt any investigative procedures to determine whether the engine had actually failed. A section drawing of the switch is shown in figure 16-18.

This failure was the first of its type to be observed in flight or in ground testing. The switch closing response (time of jet driver "on" command to switch closure) appeared to increase from an average of about 15 to 20 milliseconds during station-keeping to 25 to 30 milliseconds at the time of failure. Normal switch closing response is 10 to 12 milliseconds based on ground test results . The closing response remained at the 25- to 3o-millisecond level following the failure, and the switch continued to fail to respond to some minimum impulse commands. The switch opening time (time from jet driver "off" command to switch opening) appeared to be normal throughout the mission. In view of these results, it appears that the most probable cause of the switch failure was particulate contamination in the inlet passage of the switch. Contamination in this area would reduce the flow rate of chamber gases into the diaphragm cavity, thereby reducing the switch closing response. However, the contamination would not necessarily affect switch opening response since normal chamber pressure tailoff requires about 30 to 40 milliseconds to decrease from about 30 psia to the normal switch opening pressure of about 4 psia.  The 30- to 40-millisecond time would probably be sufficient to allow the gases in the diaphragm cavity to vent such that the switch would open normally.

The crews for future missions will be briefed to recognize and handle similar situations.

Now I'm going to explain to you everything that's wrong with your analysis of the problem.

1. Jet A2A is for yaw control only.  It could fail permanently and entirely, and the ability of the LM to maintain yaw control would not be affected.  Its pitch and roll control would be unaffected, and were unaffected by this anomaly.  (Note that the report specifically says this failure had no effect on the mission.)

2. The failure was not of the RCS system as a whole, but was isolated to a single jet that was fully redundant.

3. The failure did not last 18 minutes in the sense that the ship was out of control for 18 minutes.  The data say that a failure was indicated seven discrete times within a given 18-minute period defined by mission phases.

4. The failure was not with the jet, but with the chamber pressure sensor monitoring the operation of the jet.  Its only job is to provide a signal to the computer that the jet has responded as commanded.  The jet was, in fact, firing.  The worst-case outcome if this failure had become permanent would have been a false-positive signal to the RCS logic of a jet failure.  The A2A jet can be lost without any effect on the mission, and actual jet failure can be diagnosed by other means, providing for the crew to override the false indication.

5. The failure was simply a sluggishness in the response of the sensor.  This matters only in minimum-impulse mode, also called pulse-mode.  In this mode the jets are pulsed for only a few milliseconds as a means of fine-grained attitude control.  This is consistent with observations from earlier in the mission where the indicator had been sluggish.  In longer RCS burns the sensor functioned adequately.

Now go back and re-examine your fretful, panicky analogy to losing steering on a dark, desolate road.  Isn't it about time you just admit you really don't understand the engineering behind these spacecraft, and that you're just plain wrong?

[Peter B]

Man, you guys are a tough bunch. 

And what adjective would you apply to yourself?

It wasn't even my intention to argue more about the RCS's. Just trying to help out another poster with some info. Yes the CSM RCS's cones were not ripped off on liftoff according to Apollo documentation.

"According to Apollo documentation"? What's that supposed to mean? That if they had been ripped off then we wouldn't know any better because NASA could just fib about it in the paperwork? If not, what exactly do you mean?

My point was why would NASA risk this even if there was a slight chance of problems? It would not be the first time a rocket hasn't remained intact through launch.

Just look at the whole of the Saturn V and get a clue (which has already been given to you by JayUtah): the RCS engines on the Service Module weren't covered; but the equivalent system on the Saturn V third stage was covered by a streamlined fairing.

Why do you think NASA would adopt two different approaches for similar devices in two different locations?

I for sure would not want to lose my steering for 18 minutes down a desolate, dark road.

Maybe not, but let's make the analogy relevant. What would you do if a warning light came on each time you used an electrical system in your car when you were only a few miles from your Winnebago, and if your car failed totally you could still phone your friend in the Winnebago to drive to you?

And as for the deflectors, if you examine some of the early anomalies (such as certain engines running at sub par performance), it would raise certain concerns of the ability of the ship remaining stable through its mission with the addition of these (untested A11) deflectors.

Why? Engine performance and vehicle stability are two separate (if related) issues. To play a bit further with your analogy, it's like being worried about the tread on the car's tyres because of issues with the diesel fuel.

In any case, do the maths: the thrust of the LM's RCS engines is 100 lb, and only a portion of the exhaust gases impinge on the plume deflectors. The mass of the fully loaded LM is over 30,000 lb. How much acceleration is going to be imparted by the impingement of part of a single RCS engine's exhaust on a deflector?

And to be clear, documentation states the deflectors were somehow securely attached on the launchpad and not during Assembly/mating process.

Why add the word "somehow"? You've already been shown the work platforms which could be placed inside the Spacecraft LM Adaptor to allow access to the LM after stacking.

Added weight...

Of less than 9 pounds on a spacecraft with a loaded mass of >30,000 pounds. That's equivalent to adding half a pound to that hypothetical desert-driving car.

...and changing the steering dynamics all literally last second, not to mention re-wrapping the ship in new insulation. I guess it is plausible.

Do you worry about the effect on the steering when deciding where to place a one-pint carton of milk in your car?

Again, I am not looking to argue. I have agreed that, according to NASA, no RCS cones were ripped off on liftoff, and there were no complete RCS failures. And it is plausible, albeit questionable (in my mind), that LM's (untested) makeover could have occurred on the launchpad.

Yeah, but do you accept that the reason no RCS cones were ripped off on liftoff is our understanding of a concept which also applies to ships and aircraft, and other rockets apart from the Saturn V? In other words, do you accept that this is a concept with general application in science and technology, rather than some obscure bit of engineering tricked up just for Apollo?