Apollo 11 Lunar Lander Pre-Launch

[Zakalwe]

Just because its an "MIT paper" doesn't imply that it's correct.

Since it was MIT who designed the system, I'd stipulate that the paper -- taken as a whole -- is almost certainly correct.  The Charles Stark Draper lab produced a host of written materials discussing the theory and practice of three-axis control as it related to Apollo spacecraft.  And why shouldn't they?  They're academics, the premier academic institution for this sort of thing.

Agreed, but jr Knowing's claim appeared to be little more than a claim from authority. Until we know what the "MIT paper" actually was then I'd just dismiss it, especially in light of the individuals inability to grasp simple concepts.

[JayUtah]

Agreed, but jr Knowing's claim appeared to be little more than a claim from authority. Until we know what the "MIT paper" actually was then I'd just dismiss it, especially in light of the individuals inability to grasp simple concepts.

No argument here.  I want merely to finely slice between two ideas.  I'm happy to accept MIT as an authority on the Apollo guidance system.  That's not the objection.  But without more information, I'm not willing to accept vague references to that authority as proof that plume deflectors would have presented a stability problem.  I know they won't.  Nor do other vague references establish the claim that the guidance problem is precarious.  I know it isn't.  If Jr is getting that from any paper he reads from MIT on the Apollo guidance system, then he isn't understanding it.  We have to see the actual paper in order to determine how he misconceived it.

[bknight]

Agreed, but jr Knowing's claim appeared to be little more than a claim from authority. Until we know what the "MIT paper" actually was then I'd just dismiss it, especially in light of the individuals inability to grasp simple concepts.

No argument here.  I want merely to finely slice between two ideas.  I'm happy to accept MIT as an authority on the Apollo guidance system.  That's not the objection.  But without more information, I'm not willing to accept vague references to that authority as proof that plume deflectors would have presented a stability problem.  I know they won't.  Nor do other vague references establish the claim that the guidance problem is precarious.  I know it isn't.  If Jr is getting that from any paper he reads from MIT on the Apollo guidance system, then he isn't understanding it.  We have to see the actual paper in order to determine how he misconceived it.

Very likely judging from current arguments.  And I don't believe he will be able to dig up the document.  It seems like he read a reference to that document but not the actual document. I could be and have been wrong in the past, but the repeated request have brought forth nothing.

[onebigmonkey]

Would the OP care to explain what is remotely similar about the object on the left and the object in the other two photographs?

[jr Knowing]

Hi Everyone,

Here is one of the MIT documents. I will try to dig up the much more in depth paper. To be clear it states

"Due to the presence of jet plume deflectors on the LM descent
stage, the use of +X thrusting LM jets for pitch or roll attitude control
of the CSM-docked configuration will"  "cause a
serious control instability"

Further it goes onto state that less than ideal conditions will lead to a positive feedback loop that will cause

"the vehicle will spin uncontrollably
in the counter clockwise direction."

Everything I have said is here. I guess all you guys need to argue with MIT and not me. Further one of the more in depth papers I read (I will try to dig up) lays it out even more explicitly stating ideal conditions consisting of weight balance, thrust balance and proper timing are requirements to ensure the craft doesn't become unstable.

Now can we move on and maybe give me a little respect. Thanks

https://www.ibiblio.org/apollo/Documents/LUM117_text.pdf

[Jason Thompson]

Hi Everyone,

Here is one of the MIT documents. I will try to dig up the much more in depth paper.

This is a memo, not a paper. World of difference between the two things.

It was also written after Apollo 11 landed.

To be clear it states

"Due to the presence of jet plume deflectors on the LM descent
stage, the use of +X thrusting LM jets for pitch or roll attitude control
of the CSM-docked configuration will"  "cause a
serious control instability"

Yes, it does indeed state that. However, here is where you lose marks for a) intepretation and b) honest representation of the statements.

Point a): the memo is referring to the use of the LM RCS to control attitude in the CSM/LM docked configuration. During normal flight the LM RCS is not used for this, the RCS on the SM is. Only one flight used the LM RCS for any purpose in the docked configuration, and that was Apollo 13.

Point b): it refers to causing a control instability "for some mass loadings" and "if any -X thrusting jets have failed off or have been disabled". Please explain your failure to include those caveats.

Furthermore, having pointed out this specific set of circumstances that will result in automatic control instability, it then goes on to detail exactly how this problem can be overcome by manual crew intervention.

So, in summary, you have taken a memo (not a paper) that outlines a specific problem that may occur in some very specific (and unlikely) circumstances, and explains how to avoid the problem and correct any issues by using manual control, and suggested it somehow proves that the plume deflectors on the LM were a huge problem for successful control of the LM alone.

Further it goes onto state that less than ideal conditions will lead to a positive feedback loop that will cause

"the vehicle will spin uncontrollably
in the counter clockwise direction."

Yes, in the event that the automatic control is used in a very specific set of circumstances which are very unliley to arise in flight, which have nothing to do with independent LM flight or landing, and assuming the crew takes no manual control of the situation.

Everything I have said is here.

Yes, but you left out a lot of very important details to make your argument. Why?

I guess all you guys need to argue with MIT and not me.

No, we will argue with you, because it is your failure to correctly understand and apply this memo (again, not a paper: this is an important distinction) that is under discussion here. This memo in no way applies to control of the LM itself or to its ability to land.

Further one of the more in depth papers I read (I will try to dig up) lays it out even more explicitly stating ideal conditions consisting of weight balance, thrust balance and proper timing are requirements to ensure the craft doesn't become unstable.

Under what specific conditions?

Now can we move on and maybe give me a little respect. Thanks

If you want respect then represent the arguments you are using honestly and try to put some thought into how they might actually apply. A memo or paper that points to a possible control instability is not only nothing remarkable, it is to be expected. Any system will have potential scenarios in which control instability arises. The question is not if it happens but if it can be dealt with. This memo covers just that.

[Mag40]

Jr - I have read this thread from start to finish. You have failed to earn any respect because of your appalling evasion to answers that not only address your questions and claims, but actually tear apart your naive and not slight ignorance.

The fact it has taken you 15 pages and numerous requests is not impressive.

[Jason Thompson]

Another point on that graph: the shaded grey section is labelled as a region in which deflected jets lead to increased instability, but the lower two-thirds of the graph is described as a region in which the deflected jets actually lead to increased stability of the configuration.

So you have a memo that you think supports your arguments that in actual fact has myriad ways in which it not only does not support them it does not even apply to them. And you want respect for that?

[JayUtah]

"Due to the presence of jet plume deflectors on the LM descent stage, the use of +X thrusting LM jets for pitch or roll attitude control of the CSM-docked configuration will" [important detail omitted] "cause aserious control instability"

Why did you leave out all the important parts?

Further it goes onto state that less than ideal conditions will lead to a positive feedback loop that will cause

"the vehicle will spin uncontrollably in the counter clockwise direction."

...hence, according to the instructions given in the memo, if the astronauts need to operate the spacecraft under the conditions you leave out (which is rare, if ever), they should disable certain jets to avoid the dangerous condition -- something I told you several days ago was possible to do.  Also, the conditions described in the memo are not merely "less than ideal."  They indicate a disabled spacecraft further operating in a docked contingency mode -- two independent failure modes.

Everything I have said is here.

All nicely cherry-picked.

I guess all you guys need to argue with MIT and not me.

I have no argument with MIT because they don't say anything I disagree with.  But I'm definitely going to continue argue with you because your dishonesty is even more apparent in your choices of what to leave out and your indifference to the applicability of the memo.

Now can we move on and maybe give me a little respect. Thanks

No.  You grossly and deliberately misrepresented your source.  My respect for you is even less than it was this morning.

[Zakalwe]

Hi Everyone,

Here is one of the MIT documents. I will try to dig up the much more in depth paper. To be clear it states

"Due to the presence of jet plume deflectors on the LM descent
stage, the use of +X thrusting LM jets for pitch or roll attitude control
of the CSM-docked configuration will"  "cause a
serious control instability"

Further it goes onto state that less than ideal conditions will lead to a positive feedback loop that will cause

"the vehicle will spin uncontrollably
in the counter clockwise direction."

Everything I have said is here. I guess all you guys need to argue with MIT and not me. Further one of the more in depth papers I read (I will try to dig up) lays it out even more explicitly stating ideal conditions consisting of weight balance, thrust balance and proper timing are requirements to ensure the craft doesn't become unstable.

Now can we move on and maybe give me a little respect. Thanks

https://www.ibiblio.org/apollo/Documents/LUM117_text.pdf

Perfect, thank you.

From this I can tell you that you cannot tell the difference between a published paper and a memo. I can also tell that you that your attempt to cherry-pick from this document has further evidenced your incompetence in this subject. I presume that you don't know what a Tindallgram is either?

I'll strike this down to the Dunning Kruger effect. Again.

[JayUtah]

It was also written after Apollo 11 landed.

And before Apollo 13 flew.

The question is not if it happens but if it can be dealt with. This memo covers just that.

This is a testament to how thoroughness of the Draper lab.  For this memo even to become applicable to flight, all of the following would need to happen:

(a) The primary CSM guidance system fails.
(b) The secondary CSM guidance system fails.
(c) One specific RCS jet (out of 16) on the LM fails.
(d) Manual control of the CSM-docked LM is impossible or inadvisable.
(e) A certain specific maneuver is required.

That didn't even happen on Apollo 13.  Only two out of the five necessary conditions for instability arose on the most disastrous of the Apollo flights.  This is the degree to which MIT had to go to find a scenario in which the plume deflectors altered the guidance problem.

[onebigmonkey]

As a complete non-rocket scientist, can I take a wild stab in the dark that important bit that was deliberately omitted was

if any -X thrusting jets have failed off or have been disabled.

So, if something breaks, it might cause a problem, here's how you can fix it.

How does the presented document square with the claim that no-one did any research into this stuff, because it  looks like someone kind of did some research into it.

[molesworth]

Here is one of the MIT documents. I will try to dig up the much more in depth paper. To be clear it states

"Due to the presence of jet plume deflectors on the LM descent
stage, the use of +X thrusting LM jets for pitch or roll attitude control
of the CSM-docked configuration will"  "cause a
serious control instability"

Seriously?  You've cherry-picked selectively to try to make it sound like this supports your conjecture.  Either you don't understand what it really says, or you do, and are being very dishonest, perhaps hoping nobody would bother to examine it in detail.

...

Now can we move on and maybe give me a little respect.

Sorry - I didn't have much respect for your approach to "questioning the record" up to now.  With this display I have even less for you going forward...

[bknight]

<snip>
Now can we move on and maybe give me a little respect. Thanks

https://www.ibiblio.org/apollo/Documents/LUM117_text.pdf

You get a vote of "no confidence"  from me. 

[JayUtah]

As a complete non-rocket scientist, can I take a wild stab in the dark that important bit that was deliberately omitted was

That, or you could just look at the subject of the memo where the author specifies this to apply only to the CSM-docked flight using the LM autopilot.  And it's only unstable if you also lose a LM thruster.  And the danger is, "It might be unstable, so here's how you fix that."  I mean, it's overkill.  It's like British Motor Corporation writing up a service memo for how to take home one's newly-purchased armchair in a Mini.