Merged Apollo "hoax" discussion - continuation thread

[cjameshuff]

So it uses a combination of assumed accelerations and velocities and actual measurements of same?

IIRC, it was one of the first major applications of Kalman filters.

It maintains an internal estimate of the system state which it uses as a basis for predicting the future state based on known dynamics of the system. It compares those predictions to actual measurements, correcting the estimate to be consistent with the actual state of the vehicle without relying entirely on either. If the dynamics model remains accurate, the result is a highly robust control system that converges to a good estimate of the system's state, but filters out spurious sensor inputs which are physically unlikely given recent history.

Reliability of different input sources can be taken into account, some sensor inputs having more importance relative to each other and to the internal estimate generated by all the previous sensor inputs. At the extreme, you might occasionally have a source trustworthy enough that you just overwrite the internal estimate with direct measurements.

 

[thedopefishlives]

So it uses a combination of assumed accelerations and velocities and actual measurements of same?

It sounds like the old "suck it and see" approach; you put the spacecraft into what you think is a particular orbit, then observe it to see how far away from the intended orbit it actually is, then adjust the orbit to make up the difference.

It reminds me of a funny story I once read on an ASW course back in the 1980's


"The missile knows where it is because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (depending on which is the greater) it obtains a difference, or deviation.

The guidance system then uses this deviation to generate corrective commands to drive the missile from a position where it is, to a position where it isn't. Consequently, the position where it is now is the position where it wasn't, and it follows that the position where it was, is now the position where it isn't.

In the event that the position where it is now is not the position that it previously wasn't, the system will have acquired a variation, being the difference between where the missile is and where it wasn't.

If the variation is considered to be significant, it may be corrected, however, the missile must also know where it was. The missile guidance sequence can be summarised as follows;

Because a variation has modified some of the information the missile has obtained, it is not sure where it is, however, it is sure where it isn't and it knows where it was. It now subtracts where it should be from where it wasn't, or vice-versa, and by differentiating this from the algebraic sum of where it shouldn't be, and where it was, it is able to obtain both the deviation and its variation."

This is the essence behind closed-loop control systems: Don't trust the inputs blindly, measure whatever measurable outputs you can and compare them to what you expected given the inputs. The error tells you how far your internal state was off, and then you can update that and compare to the expected state to adjust the inputs. There are control algorithms that deal with exactly how much adjustment to make and when, depending on the system being controlled. The next time you set the cruise control on your car, you can observe this; it uses a closed-loop control algorithm based on the accelerator and the speedometer. Far, far simpler system than the Apollo guidance system, obviously, but the basic underlying principle is the same.

 

[Willy Ekerslike]

Yesterday evening I was introduced to two people, one early 40s, one mid 60s who, for one reason or another got to talking about Apollo. I joined in and they looked at me incredulously, the younger one saying "You're the first person I've ever met who believes Apollo actually went to the moon!" The older then said "What about the shadows? The Flag? The stars?" To which I replied "Well, some people believe anything, don't they?" They seemed happy with that 'apology', not realizing what I meant! I gently related a couple of points about Jodrell Bank (which is nearby) and, to their demand "if it happened, why did they never go back?" reminded them about 12, 14, 15, 16 and 17. Nonplussed. So now, I feel kind of sad and a bit depressed.

 

[kookbreaker]

My good friend found out his boss thinks Apollo was a hoax.

Keep in mind this guy is an engineer (so is my friend).

One thing about my friend's job is that he doesn't really need to watch his mouth much. After hearing this about his boss he went from belligerent to outright insulting towards his boss.

The joy is: despite the fact that he is the boss he really can't do much to my friend.

 

[abaddon]

My good friend found out his boss thinks Apollo was a hoax.

Keep in mind this guy is an engineer (so is my friend).

One thing about my friend's job is that he doesn't really need to watch his mouth much. After hearing this about his boss he went from belligerent to outright insulting towards his boss.

The joy is: despite the fact that he is the boss he really can't do much to my friend.

Yep, it's always quite a mental gearshift to find out that anyone you heretofore thought as rational is in fact a HB.

 

[John Jones]

Yesterday evening I was introduced to two people, one early 40s, one mid 60s who, for one reason or another got to talking about Apollo. I joined in and they looked at me incredulously, the younger one saying "You're the first person I've ever met who believes Apollo actually went to the moon!" The older then said "What about the shadows? The Flag? The stars?" To which I replied "Well, some people believe anything, don't they?" They seemed happy with that 'apology', not realizing what I meant! I gently related a couple of points about Jodrell Bank (which is nearby) and, to their demand "if it happened, why did they never go back?" reminded them about 12, 14, 15, 16 and 17. Nonplussed. So now, I feel kind of sad and a bit depressed.

It makes me a bit sad and depressed too. It seems that engineers fall for the Apollo Hoax woo-woo more often than scientists, though more engineers worked on the Saturn V rockets.

 

[Neutiquam Erro]

What about the argument that Neil took pictures before the contingency? That one worked for me. Don't you think it is suspicious because they would have drilled that so many times. Isn't that correct?

I'd say that one exceedingly trivial anomaly (if it is even that) in the behavior of one single individual is pretty weak sauce, if one intends to use it to discredit the entire massive Apollo program.

 

[LSSBB]

I wonder why you never hear about the astronauts socks. I think they were just puppets. Puppets don't have socks.

 

[tsig]

I wonder why you never hear about the astronauts socks. I think they were just puppets. Puppets don't have socks.

Clearly if one of the astronauts once wore mismatched socks then it's all fake.

 

[Neutiquam Erro]

Clearly if one of the astronauts once wore mismatched socks then it's all fake.

In all seriousness [gulp], haven't we already heard that about the silver-painted boots in some of the Mercury and/or Gemini publicity photos?

 

[JayUtah]

Another idea for you. Integrate the accelerations twice. X one give the velocity, X 2 gives the position. The computer did just that, integrated the accelerations X 2 to give the position.

Not exactly. The accelerometers were integrating accelerometers so while it's true that you double-integrate accelerometers, the Apollo computer simply accumulated the delta-v reported by the accelerometer via the counter interrupt mechanism. Classic state-vector formulation uses velocity rather than acceleration because you sometimes have to obtain the state vector via methods that provide only velocity (e.g., orbital models).

 

[JayUtah]

Navigation is about "where you are", guidance is about "where you are going". You are sort of addressing guidance.

Well I do both for a living, so pick your topic.

 

[JayUtah]

What about the argument that Neil took pictures before the contingency? That one worked for me.

Really? One trivial departure from the flight plan throws your whole knowledge and understanding off kilter? This will probably be a fun conversation.

Don't you think it is suspicious because they would have drilled that so many times. Isn't that correct?

No, I don't think it's suspicious since Armstrong explained in his debriefing why he did what he did, and it was for what he decided was a good reason. He was not a trained monkey. "He went off script," is not a sufficient reason to accept your judgment. Go find Armstrong's explanation for why he went off script and tell us why we should consider his rationale poor judgment.

 

[trebor]

What about the argument that Neil took pictures before the contingency? That one worked for me. Don't you think it is suspicious because they would have drilled that so many times. Isn't that correct?

Why would it be suspicious?

 

[Erock]

I wonder why you never hear about the astronauts socks. I think they were just puppets. Puppets don't have socks.

I think you will find they didn't drill putting their socks on into the training regime. One black sock and one blue sock is no more suspicious than for example a newbie arriving, bumping two Apollo threads and talking about the guidance system. It's not as though they mentioned poop is it

 

[LaurelHS]

No, I don't think it's suspicious since Armstrong explained in his debriefing why he did what he did, and it was for what he decided was a good reason.

He went "off-script" at least one other time when he walked over to Little West Crater for photographs. He thought geologists would be interested and it was a very short trip.

 

[Peter May]

You're not in a position to prove anything. What you are doing there is telling people what their argument is and telling that they're wrong, without having any kind of basis for either side of it.

Your so called issue is a fictitious one entirely of your own making. Run along now.

'


This is very true.
The truth has no political affiliations or aspirations, it cannot be bent by belief, it has no masters, nor is it open to debate. It remains simply the truth.

It is very important to understand the nature of what we see, and not what we want to see.

 

[Peter May]

You talk as if your word were proof. It's not proof as you might be lying.

I maintain that this is such a basic, self-evident issue that nobody has to ask an expert to confirm it. If anyone wants to, I guarantee the objective expert will find the pro-Apollo camp's position laughable.

Here's an example of billowing dust in atmosphere.
http://www.youtube.com/watch?v=E6FH7x0wB_I
(4:30 time mark)

Your position is that, if some dust-free sand is transported and placed, the erosion caused by transporting and placing it will be enough to create enough dust to cause dust clouds when it's driven over. The fact that this is wrong is very self-evident. The sand would have to be beaten with sledge hammers for hours and hours to create that much dust. Any twelve-year-old could explain this.

You people aren't fooling anybody. This issue is simply too basic.

Wrong


The truth has no political affiliations or aspirations, it cannot be bent by belief, it has no masters, nor is it open to debate. It remains simply the truth.
You seek to find a master for the truth where there is none.

 

[LaurelHS]

Why are you responding to posts from January?

 

[Erock]

Why are you responding to posts from January?

Hell, why is he responding to FF88 AND from January