ApolloHoax.net
Apollo Discussions => The Hoax Theory => Topic started by: dwight on September 17, 2013, 02:43:57 PM
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Oh my goodness. I, in a moment of weakness, watched his video about the strange TV cameras on Apollo. I can't work out if he is purposefully excluding information in his "analyses", or whether he honestly believes he is covering all the information, while in reality it is blatantly obvious he has less than a cursory idea.
Rather than go through all the points about which he is grossly in error, I'll just say everything is completely false. From his understanding of how the RCA scan converter worked, to the Rx of the TV signal at different tracking stations, through his misrepresentation that NASA controlled Parkes (instead of the reality that the CSIRO did/do), to his complete lack of understanding of sequential TV, it is painfully obvious he has little, if any, idea of what he is writing about.
I was going to respond, but I thought I'd spare myself the endless back-and-forth denial of being wrong despite being shown all the evidence, even with the assistance of finger-puppets.
My favourite moment? Where he couldn't get his head around how the scan converter at Goldstone could output crushed blacks, whereas the scan converter at Honeysuckle didn't - given that the image from the WEC camera on the lunar surface sent the same image to both tracking stations. I weep for humanity.
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"Output crushed blacks"? I assume that it means that the facility could create a true black, but I could well be wrong. Could you relate that to photographic term? Thanks.
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Yeah, some of us are not familiar with the jargon.
Little help decoding, please?
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"Output crushed blacks"? I assume that it means that the facility could create a true black, but I could well be wrong. Could you relate that to photographic term? Thanks.
I must be tired; I read photographic as pornographic on my first read ;D
That said I'm curious about the jargon as well.
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"Output crushed blacks"? I assume that it means that the facility could create a true black, but I could well be wrong. Could you relate that to photographic term? Thanks.
I must be tired; I read photographic as pornographic on my first read ;D
That said I'm curious about the jargon as well.
I work for a company that values diversity - in fact it's part of our goals as managers. Do you have any how hard it is to type the phrase "output crushed blacks?"
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I haven't read the full thing (typical me) but in imaging, 'crushed' blacks (or blocked/clipped) are similar to 'blown' whites - in other words it is a region of flat and featureless black(white) that should/could contain detail if:
- it were properly/differently exposed
- the sensor/film's dynamic range was capable of capturing the lost nuances at the extremes of its range
- if the image had not been degraded by any number of issues
or any combination thereof.
The less capture and transmission 'bandwidth' you have, and the more generations of copying/re-transmitting/conversion to different formats etc, the worse it becomes, resulting in an over-contrasty and lower-res image that is short on shadow and highlight detail.
Usually, 'crushed' stuff is a bad thing...
Here's an example - the right hand side has crushed blacks and blown whites:
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"Output crushed blacks"? I assume that it means that the facility could create a true black, but I could well be wrong. Could you relate that to photographic term? Thanks.
It is a photographic term. It's just the opposite of blown highlights, where information is lost in the dark areas of the image. The dim parts are "crushed" in amplitude...the image may have areas of true black or just not capture those areas with much precision.
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"Output crushed blacks"? I assume that it means that the facility could create a true black, but I could well be wrong. Could you relate that to photographic term? Thanks.
I must be tired; I read photographic as pornographic on my first read ;D
That said I'm curious about the jargon as well.
I work for a company that values diversity - in fact it's part of our goals as managers. Do you have any how hard it is to type the phrase "output crushed blacks?"
As long as Al Sharpton doesn't see it, I think you're okay.
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"Crushing the blacks" is standard parlance in my trade for reducing the density level in the shadow detail of a photo or video to remove or lower the level of noise in the shadows.
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Sorry about the jargon. Crushed blacks is exactly as described above. In the case of the A11 TV feed I was referencing the first moments of TV where the scan converter operator in Goldstone panicked and brought the black video levels down (crushing them) which reduced the contrast ratio significantly, hence the almost two-tone TV image. HSK on the other hand didn't have the panicked operator and had the properly exposed output. According to hunchbacked, this cannot happen as both stations got the same output from the lunar TV camera.
Speaking of Goldstone, there was another clown on the YT clip of my interview with spacevidcast who, not realizing who I was, attempted to inform me that a live broadcast of a live broadcast must be a recording. Then after pointing out the I began the word with "GF" instead of "G", insisted I learn how to spell "Foldstone" correctly. I kid you not.
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So apparently Hunchbacked never played with the settings on his TV. :P
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"Output crushed blacks"? I assume that it means that the facility could create a true black, but I could well be wrong. Could you relate that to photographic term? Thanks.
It is a photographic term. It's just the opposite of blown highlights, where information is lost in the dark areas of the image. The dim parts are "crushed" in amplitude...the image may have areas of true black or just not capture those areas with much precision.
Thanks all for the explanation. And, honestly, after being an amateur photographer for (oh my) 40+ years, I never heard the term!
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it is painfully obvious he has little, if any, idea of what he is writing about.
So what else is new?
My inability to get through to hunchbacked used to bother me a little. Most Apollo deniers are obviously quoting whatever appeals to them with no understanding or desire to even appear interested in the facts; I heard "arguments" like theirs every day in the 4th grade. But hunchbacked is much more earnest. He does his own "research". He's far more polite, though he has his moments. He rarely blocks critics. He actually has a (slight) sense of humor, occasionally depicting his (reasonably accurate) understanding of how we perceive him: a grinning idiot wearing a tinfoil hat.
I even got him to concede a few errors, and that led me to believe he might concede others if I simply explained things better, with references. (You know what they say about random reinforcement.)
But then I saw his complaint about AS17-145-22272 of the CSM from the LM during docking. His "incoherency"? We should see the side of the service module! I explained the obvious: the picture was taken through the LM's overhead rendezvous window which is closer to the overhead hatch/docking port than the CSM's radius. We are just seeing the CSM in correct perspective. He gave elaborate nonsensical "explanations" that had nothing to do with the CSM's geometry. I suggested a simpler way: just make a model of the CSM and view it with your eye close to the docking probe. He ignored it.
So I was already questioning his grip on reality when he put out his now-famous video about Buzz Aldrin's zero-G sandwich-making demonstration: "Buzz Aldrin" is an imposter wearing a Buzz Aldrin mask in a water-filled CSM, breathing through his headset wires, spinning a perfectly weighted can of paté.
I gave up. The guy is just batshit insane. His standard complaint, that honest engineers protesting against their CIA masters were encoding secret clues in diagrams of purposely unworkable devices, sounds an awful lot like Dr. John Nash's delusion that newspapers contained secret messages sent to him by the Russians.
Many of his recent videos demonstrate his remarkable inability to sense visual perspective but they're a lot less interesting than the technical ones.
So now I just have fun with him. (And yeah, I admit it. I play to the galleries.)
And he can be entertaining.His odd English vocabulary is another source of amusement. I wear the hunchbacked-awarded label of "disinformer" with considerable pride.
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Thanks all for the explanation. And, honestly, after being an amateur photographer for (oh my) 40+ years, I never heard the term!
It might be more common in video. I heard the expression in the 1970s when I did engineering at a TV station.
The complementary expression is "clip the whites". We were usually looking at a waveform monitor (a specialized video oscilloscope) where pure white is maximum voltage.
"Clip" is a very common term in electronics for what happens to a waveform when it is abruptly kept from becoming more positive (or more negative) than some specified voltage. The peaks are "clipped" off. When you turn the volume control of an amplifier so high the sound distorts, that's clipping. Sometimes clipping is intentional, mainly in speech communications where it can improve its intelligibility on a noisy channel at the expense of fidelity and increased background noise when the speaker isn't talking. The shuttle's voice system still seemed to routinely clip speech even though it was all digital and didn't need the help. I always thought it sounded terrible.
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Keep it up you guys! Most excellent work in bringing that ol' nasty reality into the HB world.
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Isn't doing much good...
It might be fun to collect a list of Hunchbacked's more amusing witticisms. Since his native language isn't English it's a bit unfair to criticize him on it, but his language is highly idiosyncratic and some of his word choices are persistently unusual. I once saw him on a different forum posting under a different name, and I asked if he was 'hunchbacked' on Youtube. He said 'Yes, how did you know??' To me, it was obvious.
Some of my favorite Hunchbacked terms
incoherence - a supposed inconsistency or contradiction in the record
disinformer - a badge I wear with pride
jeep - the LRV
tasty - frequent adjective for his 'incoherence' discoveries
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Regarding his lack of understanding of perspective - is it possible he is vision impared - perhaps blind on one eye?
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I've wondered the same thing. Or maybe "lazy eye"? I've asked him but he's always ignored the question.
Your brain maintains a model of the would around you. Two eyes certainly help, but you also do it with just one 'eye' for (non-3D) photos, TV and movies. You judge perspective with your intuitive understanding of geometry, by reference to familiar objects, and (for TV and movies) by how things change when the camera moves. This tells me that even people blind in one eye should still be able to judge visual perspective.
(The ease with which the human brain does this is really quite remarkable given how difficult the robotic vision problem has been. Otherwise autonomous cars wouldn't need radars or laser rangefinders, just a couple of cameras.)
The moon is certainly prone to optical illusions, mostly having to do with judging distances to distant objects because of the fractal nature of the lunar surface and the complete lack of familiar cues like atmospheric haze, roads, trees, houses, etc. The astronauts themselves often expressed frustration at not being able to judge distances; a rock might be small and close or huge and far away, and they wouldn't know until they tried to approach it.
Hunchbacked is prone to these same illusions, of course, but he also seems unable to interpret foreground scenes that most people find very easy to understand. It's a fascinating phenomenon, and we can't really know how much of it is just his burning desire to continually confirm his delusions. He never really explains what these perspective "incoherences" mean, only that something is wrong, ergo Apollo must have been faked.
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There's nothing wrong with not speaking English well if it isn't your first language. There is something wrong with refusing to be corrected by native speakers.
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I've wondered the same thing. Or maybe "lazy eye"? I've asked him but he's always ignored the question.
Your brain maintains a model of the would around you. Two eyes certainly help, but you also do it with just one 'eye' for (non-3D) photos, TV and movies. You judge perspective with your intuitive understanding of geometry, by reference to familiar objects, and (for TV and movies) by how things change when the camera moves. This tells me that even people blind in one eye should still be able to judge visual perspective.
We've discussed this a number of times. It seems to me that there almost has to be something defective in his visual interpretation. I (and others) had a long back-and-forth (I hate to use the term 'debate') about a shadow on one of the LM footpad joints that he insisted was a hole. Sometimes it's very difficult for me to believe he's not joking, like when he takes measurements of a (rough) schematic diagram in a NASA manual, like this one:
(http://i627.photobucket.com/albums/tt353/jarvisn/LMDescent_zps3cc3ddc8.jpg)
and, based on his measurements, insists that the position of the line does not represent a possible orbit.
He just put a video up a few hours ago in which he rehashes some of the same old stuff, along with a few things that someone who has been "studying" the Apollo missions for as long as he has should know better than.*
He claims that there were no unmanned landings before Apollo - evidently the Surveyors never flew, nor Luna 9 or 13.
He claims that NASA took a huge risk in allowing AS-11 to land after there had been a fuel cell anomaly on AS-10, because a fuel cell failure on the LM during the descent could have "tragically ended" the mission.
And, of course, it was all because JFK was a master political manipulator - just ignore the fact that he didn't even live to see the first manned Gemini flight.
I don't know just what it is, but there's just something very odd there. All just IMHO, of course.
Oh, and vocabulary? He uses "important" to mean 'more' or 'greater'; i.e. the CM had a more important velocity than the LM (was moving faster).
*I fully expect a visit from the bad grammar imps over that one.
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"On the LM? Haven't he even looked at the specs?
I'm sure there wasn't a single functioning fuel cell on any of the LM's ever flown.
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*I fully expect a visit from the bad grammar imps over that one.
Yup. Never use a preposition to end a sentence with. ;D 8)
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"On the LM? Haven't he even looked at the specs?
I'm sure there wasn't a single functioning fuel cell on any of the LM's ever flown.
Which would indicate that he doesn't actually know what a fuel cell is!
He probably thinks its part of the fuel system rather than part of the electrical power system.
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It gets better. When the LM was in its ascent and had gotten in sight of the CM, he complains that there's no lateral movement - it just stays in the same apparent place and gets closer. Evidently he doesn't realize that two objects on an intercept course hold a steady bearing from each other.
We've all heard, I guess, how Armstrong and Aldrin found it too cold in the LM to sleep comfortably. Hunchbacked, of course, finds this unbelievable (it should have been hot, he says) despite the fact that it was heavily insulated and the crew had blocked off the windows to keep the light out.
He also makes another pass by the post-flight press conference, rehashing the "no stars" b.s., then complains that it was impossible to identify an astronaut's features through the EVA visors.
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It gets better. When the LM was in its ascent and had gotten in sight of the CM, he complains that there's no lateral movement - it just stays in the same apparent place and gets closer. Evidently he doesn't realize that two objects on an intercept course hold a steady bearing from each other.
I presume he's thinking of steering a car, and how you constantly have to make corrections.
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And he can be entertaining.His odd English vocabulary is another source of amusement. I wear the hunchbacked-awarded label of "disinformer" with considerable pride.
Hunchy does have pretty decent English for a non-native speaker. But have you noticed how it breaks down when he's cornered or flustered? He starts stringing together jibberish that's even less coherent than his usual ramblings. I'm not sure if it's intentional or involuntary, but it's a good "tell" when you've struck a nerve.
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Regarding his lack of understanding of perspective - is it possible he is vision impared - perhaps blind on one eye?
Hm - I asked him outright (politely, of course), and he didn't like that at all. Blocked me, and sent me a quite unfriendly message.
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Regarding his lack of understanding of perspective - is it possible he is vision impared - perhaps blind on one eye?
Hm - I asked him outright (politely, of course), and he didn't like that at all. Blocked me, and sent me a quite unfriendly message.
I think he's been asked that a lot - I know I've asked him, and so has AWR. He's probably come to regard it as a thinly-veiled insult.
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Isn't doing much good...
It might be fun to collect a list of Hunchbacked's more amusing witticisms. Since his native language isn't English it's a bit unfair to criticize him on it, but his language is highly idiosyncratic and some of his word choices are persistently unusual. I once saw him on a different forum posting under a different name, and I asked if he was 'hunchbacked' on Youtube. He said 'Yes, how did you know??' To me, it was obvious.
Some of my favorite Hunchbacked terms
incoherence - a supposed inconsistency or contradiction in the record
disinformer - a badge I wear with pride
jeep - the LRV
tasty - frequent adjective for his 'incoherence' discoveries
What is his native language? Some of these sound familiar to me. (E.g. because Bulgarian lacks a direct equivalent to "rover", in some translations the LRV is called "lunar jeep" or "lunar buggy", because the translators decided to re-use familiar loanwords instead of introducing a new one. And "disinformer" seems to be a "translation" by back-formation : since "информатор" is "informer", "дезинформатор (http://ru.wiktionary.org/wiki/%D0%B4%D0%B5%D0%B7%D0%B8%D0%BD%D1%84%D0%BE%D1%80%D0%BC%D0%B0%D1%82%D0%BE%D1%80)" must be "disinformer". :) )
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Isn't doing much good...
It might be fun to collect a list of Hunchbacked's more amusing witticisms. Since his native language isn't English it's a bit unfair to criticize him on it, but his language is highly idiosyncratic and some of his word choices are persistently unusual. I once saw him on a different forum posting under a different name, and I asked if he was 'hunchbacked' on Youtube. He said 'Yes, how did you know??' To me, it was obvious.
Some of my favorite Hunchbacked terms
incoherence - a supposed inconsistency or contradiction in the record
disinformer - a badge I wear with pride
jeep - the LRV
tasty - frequent adjective for his 'incoherence' discoveries
What is his native language? Some of these sound familiar to me. (E.g. because Bulgarian lacks a direct equivalent to "rover", in some translations the LRV is called "lunar jeep" or "lunar buggy", because the translators decided to re-use familiar loanwords instead of introducing a new one. And "disinformer" seems to be a "translation" by back-formation : since "информатор" is "informer", "дезинформатор (http://ru.wiktionary.org/wiki/%D0%B4%D0%B5%D0%B7%D0%B8%D0%BD%D1%84%D0%BE%D1%80%D0%BC%D0%B0%D1%82%D0%BE%D1%80)" must be "disinformer". :) )
Hunchbacked is Dutch isn't he?
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Il est français, je pense.
His name is Xavier Pascal. He claims to have graduated from a French university and I've seen posts he's written in French.
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Yes, he's French.
He's angry at me again. He sends me PMs accusing me of lying and deceiving his other readers. I responded by pointing out that I've frequently recommended that readers verify my information in any of the standard textbooks. No comment, of course. He must think the conspiracy extends to Halliday & Resnick (authors of a classic high school/college physics textbook), among others.
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The mindset of a conspiracy theorist is in itself a lifelong discipline.
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Me:
I asked you a simple question about how you view things. And that was insulting? Your stance on the Apollo moon landings are insulting thousands of people, namely those who worked on the project, who work professionally in science, engineering, photography and a lot of other related fields. You call them all liars and frauds - you are clearly in the minority. Nobody who's had relevant education agrees with you.
Hunchbacked:Oh really?
It was not a simple question at all, it outright was an insult; talking about "malady" about my way of seeing things is not questioning at all, it is definitively insulting.
It has been a long time that I have understood that the Apollo shills were disgusting hypocrites.
You complain that we end up in insulting you, but it is after you on your side have repetitively insulted us under a disguised "civility".
In the intro of this video, the author uses "idiotic"; isn't this insulting?
Me: In this context, "idiotic" is not insulting, it is factual.
And blocking your critics will only cause you to stand all alone along with all the other crackpots so you can congratulate each other.
Hunchbacked: of course, it is factual because we really are idiots, but if we say the same thing to you, it will be an insult because you are intelligent people, right?
Me: correct.
Did I cross a line? My original comment was deleted - but it was pretty close to "Regarding your lack of understanding of perspective - do you have vision problems, perhaps blind on one eye or another malady?"
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This is the person who claimed I could not have polish nationality because I was Australian, or that I didn't work at the TV company I do because I'm not competent in TV operations in way form whatsoever. The guy's screws are most definitely loose.
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It's not just perspective - this is the guy, remember, who insisted that this shadow:
(http://i627.photobucket.com/albums/tt353/jarvisn/4-158-AS11-LM-footpad_zps33601054.jpg)
was a void; i.e., the ball was far too small for the socket. IMO, there's definitely something out of whack there, either with his vision or visual comprehension.
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Did I cross a line? My original comment was deleted - but it was pretty close to "Regarding your lack of understanding of perspective - do you have vision problems, perhaps blind on one eye or another malady?"
I don't think blindness in one eye would make perspective more difficult to understand...working binocular vision actually seems more likely to lead to confusion, since you've got two separate views of any given scene.
I'm pretty sure the deficit is cognitive, not physical. He's unbelievably bad at any sort of spatial or geometric reasoning, particularly with interpreting 2D representations of 3D scenes.
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I wonder whether he is just delusional? I mean seriously, what sort of bloke is going to suggest the Apollo 11 zero-g demonstration by Aldrin was underwater? That is off with the fairies and he calls himself an engineer?
[Excessive stupidity alert] [/Excessive stupidity alert]
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Did I cross a line? My original comment was deleted - but it was pretty close to "Regarding your lack of understanding of perspective - do you have vision problems, perhaps blind on one eye or another malady?"
I don't think blindness in one eye would make perspective more difficult to understand...working binocular vision actually seems more likely to lead to confusion, since you've got two separate views of any given scene.
I'm pretty sure the deficit is cognitive, not physical. He's unbelievably bad at any sort of spatial or geometric reasoning, particularly with interpreting 2D representations of 3D scenes.
I see in 2D (as does something like 6% of the population), and I still understand perspective just fine. In fact I have to understand perspective and general 3Dness as part of my job, and it was only after I'd been working for some 15 years that I discovered that I don't see in stereo.
He's definitely got something cognitive going on.
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I wonder whether he is just delusional? I mean seriously, what sort of bloke is going to suggest the Apollo 11 zero-g demonstration by Aldrin was underwater? That is off with the fairies and he calls himself an engineer?
Yes, until that video I actually held out some hope for Hunchie. But then I realized he suffers from full-blown delusions, and he could never be reached with any amount of logic or reason.
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Did I cross a line?
You let yourself get sidetracked. As long as the discussion is about manners and other subjective topics, he gets the attention he craves and can paint his opponents as whatever he needs them to be in order to support his position.
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Yes, I would have to agree with that. As much fun as a biting barb in a battle of wits can be, one should never fight an unarmed man. It's not really what the battle is about anyway. Anyone can insult, some can insult well, but only the truth is the truth.
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Il est français, je pense.
His name is Xavier Pascal.
That's an appropriate name for the secret identity of a superhero's nemesis.
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Il est français, je pense.
His name is Xavier Pascal.
That's an appropriate name for the secret identity of a superhero's nemesis.
I don't know. The only comic book character I can think off hand with the name Xavier is a good guy, though Xavier is the last name.
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I wonder whether he is just delusional? I mean seriously, what sort of bloke is going to suggest the Apollo 11 zero-g demonstration by Aldrin was underwater? That is off with the fairies and he calls himself an engineer?
Yes, until that video I actually held out some hope for Hunchie. But then I realized he suffers from full-blown delusions, and he could never be reached with any amount of logic or reason.
I noticed somebody new to his videos sticking up for him 1-2 weeks ago. That is until somebody pointed out the Nautilus video to him. I don't think he's been back since. If he really believes what he's saying in that and the follow up video, then I would agree he's beyond help.
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Even now, if you bring it up, he still insists that it is the absolute truth.
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I noticed somebody new to his videos sticking up for him 1-2 weeks ago. That is until somebody pointed out the Nautilus video to him.
Synopsis, please? I have too few IQ points left to risk them by actually watching this guy's output.
Fred
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Synopsis, please? I have too few IQ points left to risk them by actually watching this guy's output.
During Apollo 11, Buzz Aldrin demonstrated, on TV, making a sandwich in weightlessness. He spread pate from a can on a piece of bread.
Hunchbacked insists the whole thing was staged on earth in a water-filled CM mockup. "Buzz Aldrin" was actually an imposter wearing a Buzz Aldrin mask and breathing through tiny tubes camoflaged as the wires in his headset.
I kid you not.
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The difficulties with perspective and inability to admit his faults reminds me of Jack White. At least he's stuck on youtube and doesn't have the cult following that thinks just because he once testified in front of Congress (even though it was a disaster) that he is now God's gift to photography.
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Synopsis, please? I have too few IQ points left to risk them by actually watching this guy's output.
During Apollo 11, Buzz Aldrin demonstrated, on TV, making a sandwich in weightlessness. He spread pate from a can on a piece of bread.
Hunchbacked insists the whole thing was staged on earth in a water-filled CM mockup. "Buzz Aldrin" was actually an imposter wearing a Buzz Aldrin mask and breathing through tiny tubes camoflaged as the wires in his headset.
I kid you not.
I wonder if he has ever tried to spread anything on a waterlogged slice of bread?
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I wonder if he has ever tried to spread anything on a waterlogged slice of bread?
Well, obviously it wasn't actual bread but actually a NASA actor in disguise. ::)
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Synopsis, please? I have too few IQ points left to risk them by actually watching this guy's output.
During Apollo 11, Buzz Aldrin demonstrated, on TV, making a sandwich in weightlessness. He spread pate from a can on a piece of bread.
Hunchbacked insists the whole thing was staged on earth in a water-filled CM mockup. "Buzz Aldrin" was actually an imposter wearing a Buzz Aldrin mask and breathing through tiny tubes camoflaged as the wires in his headset.
I kid you not.
The contortions some people will go through to cling onto their world view.
Hoax belief isn't a misguided conclusion, it's a compulsion.
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Synopsis, please? I have too few IQ points left to risk them by actually watching this guy's output.
During Apollo 11, Buzz Aldrin demonstrated, on TV, making a sandwich in weightlessness. He spread pate from a can on a piece of bread.
Hunchbacked insists the whole thing was staged on earth in a water-filled CM mockup. "Buzz Aldrin" was actually an imposter wearing a Buzz Aldrin mask and breathing through tiny tubes camoflaged as the wires in his headset.
I kid you not.
The contortions some people will go through to cling onto their world view.
And the appeal to such people is that their world view can never be faulted because they can always claim (with absolutely no basis in fact) fakery or collusion.
Apollo HBs are no different. If you took someone like Jarrah White or Hunchbacked to the moon and showed them the Apollo landing sites, they would just say that all the equipment has only just been put there. Quite simply, there is nothing you can do or say to these kinds of idiots, because they don't accept that Apollo is established fact with mountains of photographic, video and documentary evidence to support it, and they don't understand that the burden of disproof is upon them.
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I kid you not.
Ouch. There goes a point!
Fred
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Il est français, je pense.
His name is Xavier Pascal. He claims to have graduated from a French university and I've seen posts he's written in French.
I guess it's him, then, who has a page at the Aulis web site with a lengthy exposition claiming the AGC wouldn't work. He started off by claiming that it couldn't control the spacecraft because it would take too long to get updates from the ground computers if anything went astray - apparently spacecraft on translunar trajectories are prone to suddenly lunging off course if not constantly corrected, which would be news to controllers watching, say, Pluto-New Horizons. (The AGC's inability to provide realtime flight control would also be news to the pilots who flew the F-8 Crusader using an AGC for the first fly-by-wire aircraft tests.)
I had a headache and not enough time to pursue the rest, but at a glance he also appears to claim that neither the core memory nor the RAM of the AGC would work at all; apparently he is the first fellow with enough genius to look at the material that's been available for decades and figure it out. Naturally the Aulis web site lapped it up.
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I see in 2D (as does something like 6% of the population), and I still understand perspective just fine. In fact I have to understand perspective and general 3Dness as part of my job, and it was only after I'd been working for some 15 years that I discovered that I don't see in stereo.
Out of interest, do you mind expanding on this, please. I don't mean to be rude, but I'm more than a little curious. Do you have normal vision in both eyes? How did you discover you don't see in stereo? Do you know why you don't see in stereo?
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I see in 2D (as does something like 6% of the population), and I still understand perspective just fine. In fact I have to understand perspective and general 3Dness as part of my job, and it was only after I'd been working for some 15 years that I discovered that I don't see in stereo.
Out of interest, do you mind expanding on this, please. I don't mean to be rude, but I'm more than a little curious. Do you have normal vision in both eyes? How did you discover you don't see in stereo? Do you know why you don't see in stereo?
I have normal (ish) vision in both eyes, I wear glasses to correct distance issues.
I found out in my early/mid 30's. I had a company eye test and the optometrist did a test whereby I looked into an instrument that showed a different image to each eye, in this case a bird and a cage. It should have shown as a bird superimposed in the cage, and I just couldn't do it. He did a couple more simple tests to determine which was my master eye, and he discovered that I can swap master eye at will. I'd known that for years but didn't know the reason for it. That was it, he announced my vision was 2D.
I was born with what used to be called a "lazy eye" and had corrective surgery as an infant, but sometimes in these cases the brain never quite manages to do the stereo thing afterwards.
I've since realised a couple of things.
1) If I'd known before I took my driving test it may have disqualified me. I've since met someone with a similar problem who isn't allowed to drive. However I have a good driving record with many years no claims bonus.
2) I'd subconciously developed some small coping strategies for instances where depth perception was missing. For example when pouring from a bottle into a glass I always make sure to touch the rim of the glass with the bottle neck to ensure they're lined up, I've always done it but had never twigged as to why.
3D cinema just doesn't work at all for me, the glasses make everything darker but otherwise it's the same experience as 2D cinema, just more expensive.
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I have read (http://www.geeksaresexy.net/2012/07/24/3d-film-cures-a-man-of-stereo-blindness/) of a queer case of a man who, though stereoblind up to that point, went to see a 3D movie, and, somehow, something clicked in his brain and he suddenly could see in 3D.
As an aspiring artist, I find actually seeing in 3D can be a pain as it hinders my ability to replicate the true shape of the lines of things skewed by perspective. My brain insists a square in perspective is square, even though the 2D projected shape on my retina is tetrahedral. However, I can close one eye and that helps.
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Il est français, je pense.
His name is Xavier Pascal. He claims to have graduated from a French university and I've seen posts he's written in French.
I guess it's him, then, who has a page at the Aulis web site with a lengthy exposition claiming the AGC wouldn't work. He started off by claiming that it couldn't control the spacecraft because it would take too long to get updates from the ground computers if anything went astray - apparently spacecraft on translunar trajectories are prone to suddenly lunging off course if not constantly corrected, which would be news to controllers watching, say, Pluto-New Horizons. (The AGC's inability to provide realtime flight control would also be news to the pilots who flew the F-8 Crusader using an AGC for the first fly-by-wire aircraft tests.)
I had a headache and not enough time to pursue the rest, but at a glance he also appears to claim that neither the core memory nor the RAM of the AGC would work at all; apparently he is the first fellow with enough genius to look at the material that's been available for decades and figure it out. Naturally the Aulis web site lapped it up.
That's gotta be him - he has kind of a fetish about the AGC. In fact, I think some of his latest round of videos has been on that subject. He really doesn't know much about... well, anything. He's such a prolific producer of videos that it's hard to believe that he has time to do much of anything else.
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Besides, people have made working replicas of the AGC. (http://agcreplica.outel.org/)
I guess they are part of the conspiracy too. ::)
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The contortions some people will go through to cling onto their world view.
What really puzzles me about that particular video is that it wasn't a contortion necessary to cling to what I believe is his world view.
Like many Apollo deniers, hunchbacked accepts the reality of human space flight in low earth orbit. He could have claimed that the Aldrin sandwich-making video was taped in low earth orbit rather than in cislunar space and he'd be in good company with hoaxers like Bart Sibrel. His bizarre underwater-wearing-a-mask claim just makes him look like a lunatic.
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The contortions some people will go through to cling onto their world view.
What really puzzles me about that particular video is that it wasn't a contortion necessary to cling to that I believe is his world view.
Like many Apollo deniers, hunchbacked accepts the reality of human space flight in low earth orbit. He could have claimed that the Aldrin sandwich-making video was taped in low earth orbit rather than in cislunar space and he's be in good company with hoaxers like Bart Sibrel. His bizarre underwater-wearing-a-mask claim just makes him look like a lunatic.
Well, remember that Turbonium on UM claimed that the Chinese space walk from a couple of years ago was faked in a vat of liquid helium...http://www.unexplained-mysteries.com/forum/index.php?s=3fa952346808c09c4a8728c2bde5b58d&showtopic=136948&st=255#entry2770424
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Liquid helium?!
Its density ranges from 0.125 to 0.145 so people would have a very hard time floating in it. Even if they weren't frozen solid.
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Makes me think of New Agers, who use technical jargon to make it sound like their rubbish isn't just made up nonsense.
He probably used liquid helium because he thought it sounded more technically advanced.
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Makes me think of New Agers, who use technical jargon to make it sound like their rubbish isn't just made up nonsense.
He probably used liquid helium because he thought it sounded more technically advanced.
IIRC he used liquid helium because of the lack of friction.
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Well, remember that Turbonium on UM claimed that the Chinese space walk from a couple of years ago was faked in a vat of liquid helium...http://www.unexplained-mysteries.com/forum/index.php?s=3fa952346808c09c4a8728c2bde5b58d&showtopic=136948&st=255#entry2770424
I think I must be confused, because I remembered that my revulsion and disgust for that <unprintable> prevented me from signing up at this site when I first found it a long time ago. But he is not in the member list, so maybe he is at some similar site?
Anyway, his rank title at the board linked above is "government agent" and the person who is arguing with him has the title "conspiracy theorist" - I guess they just assign them based on post count, not on any assessment of their posts.
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Liquid helium?!
Its density ranges from 0.125 to 0.145 so people would have a very hard time floating in it. Even if they weren't frozen solid.
Not just liquid helium, superfluid helium. I can't remember why he though superfluid would work, but being a gnats whisker above absolute zero is going to get a bit nippy for sure.
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I have read (http://www.geeksaresexy.net/2012/07/24/3d-film-cures-a-man-of-stereo-blindness/) of a queer case of a man who, though stereoblind up to that point, went to see a 3D movie, and, somehow, something clicked in his brain and he suddenly could see in 3D.
As an aspiring artist, I find actually seeing in 3D can be a pain as it hinders my ability to replicate the true shape of the lines of things skewed by perspective. My brain insists a square in perspective is square, even though the 2D projected shape on my retina is tetrahedral. However, I can close one eye and that helps.
Wowser, I must try a few more trips to the pictures.
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I have read (http://www.geeksaresexy.net/2012/07/24/3d-film-cures-a-man-of-stereo-blindness/) of a queer case of a man who, though stereoblind up to that point, went to see a 3D movie, and, somehow, something clicked in his brain and he suddenly could see in 3D.
Weird - it must have been like looking at one of those stereo puzzle pictures, only to have things finally come together.
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Ever see "Chasing Amy"?
edit: Oops, make that "Mallrats". I knew it was one of the Kevin Smith movies.
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Weird - it must have been like looking at one of those stereo puzzle pictures, only to have things finally come together.
That actually happened to me just a couple months ago. I had been trying to see those darn things for years, decades, even and . . . suddenly, I got it. By Jove I think I got it!
I think it was because it was late at night, so late it was early, and my eyes were feeling glazed and fixed, staring straight ahead, but, whatever the reason, I finally 'got' an autostereogram.
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Yes, it's a strange "why couldn't I have seen that before?" sort of feeling once your eyes focus in that certain way.
Then I get the optical illusion ones that start flipping between "box is facing outwards" and "box is facing inwards". To tie that to the Moon Hoax Theory, it's a common phenomenon when looking at photos of craters. I wonder if monovisioned people understand why it confuses others?
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The inside-out crater illusion is common when the sun is coming from the bottom of the photograph. Try rotating the photograph upside down so the illumination is from the top and the crater should look normal. Then try to maintain that view when you rotate the photograph back to its original orientation.
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Try this one. Its a stereo-pair image of Comet Wild2 taken in 2004 by the Stardust mission
(https://dl.dropboxusercontent.com/u/98915197/ApolloHoax/stereo_pair_03_12_04.jpg)
If you have never done one of these before, the trick is to get your face about an arms-length away from the screen, and look at the image cross-eyed, allowing the images to overlap the right end of the double image in one eye with the left end of the other image through the other eye. If you relax your eye-relief, the images will "lock-in" and you'll see three images; the centre one will be in 3D.
When I do this one, initially it works fine, then all of a sudden, it goes inverted, and rather than seeing a solid shape, I see a bowl with terrain inside. The shadow in the double crater just right of centre, rather than appearing to be cast by the left rim of the crater appears to be cast by the bright area to its right, which becomes like a plateau.
I'd be interested to know if anyone else has the same experience with this that I do.
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I tink whoever created that image screwed up..
Try this one, where I've swapped the two images over, L-R.
Added - BTW, I suspect they still got the angles a bit wrong - there seems to be over-exaggerated depth - hurts my eyes! (I do these sort of stereograms myself (on normal terrestrial topics), and if you get the angle/spacing wrong with your originals, they can look quite weird and just not work..
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And just for a bit of offtopicness, here's a terrestrial example to practice the cross-eyed technique on... no, the SUV isn't mine, I was just looking for 3D candidate scenes to refine the concept.
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I tink whoever created that image screwed up..
Try this one, where I've swapped the two images over, L-R.
Added - BTW, I suspect they still got the angles a bit wrong - there seems to be over-exaggerated depth - hurts my eyes! (I do these sort of stereograms myself (on normal terrestrial topics), and if you get the angle/spacing wrong with your originals, they can look quite weird and just not work..
Your one works perfectly
I got mine from here
http://stardust.jpl.nasa.gov/news/news97.html
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And just for a bit of offtopicness, here's a terrestrial example to practice the cross-eyed technique on... no, the SUV isn't mine, I was just looking for 3D candidate scenes to refine the concept.
Wow! That was incredible. Thank you.
In looking at the Wild2 pictures I could only maintain the illusion by looking at a fixed point on the comet. As soon as I tried to look around I lost the effect.
By contrast the car picture worked brilliantly - I was able to look at all parts of the picture without losing the effect. I wonder if it's something to do with familiarity with the object being looked at.
ETA: Many years ago when I was studying geology at uni we used stereoscopes to look at stereo images. I'd been introduced to them before by an older brother, and in his case the pictures were on separate pieces of paper, so we could move them apart or together to help with "getting" the image. The images in the geology class were on a single piece of paper and the only way I could create a stereo image was to get seriously cross-eyed. The experience was so unpleasant I actually stayed cross-eyed for the rest of the day.
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Wow! Smartcooky's image and the car worked perfectly for me, but I struggled with ChrLz's asteroid one, I don't know why.
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Besides, people have made working replicas of the AGC. (http://agcreplica.outel.org/)
I guess they are part of the conspiracy too. ::)
That's been pointed out. His argument is that unless they use completely authentic hardware, i.e., iron core rope memory and vintage ICs, it's not a valid comparison. Which, actually, might be a valid point.
What he carefully ignores is that the programs that he says are "jibberish" and can't possibly run, DO run on these replicas. The hardware is irrelevant - his claim was that the software itself couldn't function. Which pretty well establishes his level of expertise when it comes to computers.
What I find interesting is that he always ignores questions that he doesn't have a ready answer for. While he has very occasionally accepted correction on one point or another, he usually retreats to:
(a) he's an Engineer Aerospatiale and you don't know what you're talking about;
(b) the Apollo engineers deliberately put errors in the plans as a "joke" because they wanted to plant clues that it was a hoax; or
(c) all the project personnel were sworn to secrecy, enforced by death threats from the Evile CIA.
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What he carefully ignores is that the programs that he says are "jibberish" and can't possibly run, DO run on these replicas.
Including through pure software emulation, which was how the code at one point was developed and debugged back in the 1960s. General purpose minicomputers were powerful enough to emulate the AGC hardware.
Indeed the program code represented as Colossus and Luminary, respectively, actually does run correctly. In fact, I believe some Apollo add-ons to Orbiter actually embed an AGC emulator and actually run the original firmware/software load.
The hardware is irrelevant - his claim was that the software itself couldn't function. Which pretty well establishes his level of expertise when it comes to computers.
A couple years ago I looked at his first claims regarding the AGC and concluded that he knew very little about computers outside the Intel and Motorola modern personal computer. His expertise, little as it was, was very narrowly focused and did not accommodate even a cursory understanding of other kinds of architectures and techniques.
What I find interesting is that he always ignores questions that he doesn't have a ready answer for.
This is what makes me believe he's simply bluffing his way through all of it, and that all or most of his claims to qualified expertise are a pretense.
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What I find interesting is that he always ignores questions that he doesn't have a ready answer for.
This is what makes me believe he's simply bluffing his way through all of it, and that all or most of his claims to qualified expertise are a pretense.
If what we've seen is his level of bluffing skill, I'd love to sit him down for a few hands of Texas Hold 'Em.
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Yeah. Witness the battle I'm currently having with him on Youtube. He keeps claiming the obvious asymmetry of the LM ascent stage was a "joke" by the engineers to show that it couldn't possibly fly; the RCS thrusters would quickly run out of propellant and crash.
It's difficult to count the major misconceptions he manages to embed in just that succinct position. The major one is that the asymmetrical locations of the ascent propulsion tanks are precisely what's needed to balance the stage given the different weights of the propellants. I gave all the supporting measurements and calculations, which he has of course completely ignored.
A lesser one is that the RCS could draw propellants from the ascent engine tanks so they couldn't run dry as long as the ascent engine was still firing.
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A couple years ago I looked at his first claims regarding the AGC and concluded that he knew very little about computers outside the Intel and Motorola modern personal computer. His expertise, little as it was, was very narrowly focused and did not accommodate even a cursory understanding of other kinds of architectures and techniques.
Yes. I laughed out loud when he claimed that the Apollo 11 LM guidance computer couldn't possibly have "restarted" each time an alarm came up because it takes minutes for his PC to reboot, and everybody knows computers are much faster now than during Apollo!
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Oy, that's as bad as the old 'Well, it takes a computer with <semi modern computer specs> to run a simulator of the LM in flight, so it must take at least that much to actually run the LM.'
It should be interesting to note that Bill Kaysing's 'Bible' of Apollo conspiracy theory makes no mention I have being able to find of computer deficiencies. This tells me it is a fairly recent complaint, born of a generation who have supercomputers in their homes and, now, their pockets.
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Yeah. Witness the battle I'm currently having with him on Youtube. He keeps claiming the obvious asymmetry of the LM ascent stage was a "joke" by the engineers to show that it couldn't possibly fly; the RCS thrusters would quickly run out of propellant and crash.
The LM isn't the only asymmetric rocket. Transtage was an upper stage for the Titan 3 launch vehicle that flew successfully despite one tank being short, fat and inboard and the other long, thin and outboard.
http://www.planet4589.org/space/misc/geo/transt.gif
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Yeah. Witness the battle I'm currently having with him on Youtube. He keeps claiming the obvious asymmetry of the LM ascent stage was a "joke" by the engineers to show that it couldn't possibly fly; the RCS thrusters would quickly run out of propellant and crash.
The LM isn't the only asymmetric rocket. Transtage was an upper stage for the Titan 3 launch vehicle that flew successfully despite one tank being short, fat and inboard and the other long, thin and outboard.
http://www.planet4589.org/space/misc/geo/transt.gif
Hell, if you want asymmetric, you can't get much more asymmetric than this...
(http://hifispy.files.wordpress.com/2012/06/cd_spaceshuttle123_500x500.jpg)
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And since only NASA has ever flown a manned space shuttle. . .
My god, the Shuttle must be fake too!
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The Atlas V has asymmetrical booster configurations: http://space.skyrocket.de/img_lau/atlas-5_config.png
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The LM isn't the only asymmetric rocket. Transtage was an upper stage for the Titan 3 launch vehicle that flew successfully despite one tank being short, fat and inboard and the other long, thin and outboard.
http://www.planet4589.org/space/misc/geo/transt.gif
Thanks. I'd heard of the Transtage but never seen one. Makes sense since it probably used the same hypergolic fuels.
Hell, if you want asymmetric, you can't get much more asymmetric than this... (picture of space shuttle)
The shuttle still had bilateral symmetry. The LM didn't even have that.
When it was new, some of my friends refered to it as the "<often-picked-on eastern European country> Bomber", because it had its bomb-bay doors on the top.
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This tells me it is a fairly recent complaint, born of a generation who have supercomputers in their homes and, now, their pockets.
It's amazing what you can do with a limited computer when you know what you're doing. And if you don't, having a supercomputer won't help.
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Hunchbacked's amusingly naive belief that computers always boot slowly actually reveals an interesting qualitative difference between the AGC (and other dedicated computers of that era) and modern computers: their speed/memory ratios. Because they were so small, old computers could read their entire memories much more quickly.
Last Monday I toured Johnson Space Flight Center. The highlight was a visit to the Apollo MOCR in building 30. We got to sit at the consoles, so naturally we all had our pictures taken in Gene Kranz's chair. (I added Sy Liebergot's for good measure.) It was surreal to be so intimately familiar with a place I'd never been before, but as a kid I spent many, many hours watching that room (and its twin) on TV.
I chuckled when one of our guides said that modern laptop computers were "five times more powerful" than the Apollo onboard computer. I worked up some newer numbers. Modern computers are roughly 1,000 times faster than the AGC but have a million times as much RAM and ten million times as much permanent data storage (though it's a little dodgy to compare a core rope with a hard drive).
The interesting thing is how the ratio of speed to memory has changed. A modern computer is a thousand times faster than the AGC but it takes far longer to process all of its memory. It took the AGC only 0.4 seconds to read all of its core rope; it takes my computer well over 7 hours to read one of its 4 TB hard drives at full disk speed.
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I tink whoever created that image screwed up..
Try this one, where I've swapped the two images over, L-R.
Added - BTW, I suspect they still got the angles a bit wrong - there seems to be over-exaggerated depth - hurts my eyes! (I do these sort of stereograms myself (on normal terrestrial topics), and if you get the angle/spacing wrong with your originals, they can look quite weird and just not work..
Personally, I learned the technique looking at stereopair X-rays - not that I ever got very good at it. Like someone upthread, it seems to work best for me if I'm kinda tired. It's as if my eye muscles are fatigued and unfocus more easily.
Yeah. Witness the battle I'm currently having with him on Youtube. He keeps claiming the obvious asymmetry of the LM ascent stage was a "joke" by the engineers to show that it couldn't possibly fly; the RCS thrusters would quickly run out of propellant and crash.
It may be that that touches on the visual comprehension thing again. He doesn't seem to grasp the difference between the centroid of a shape and the center of mass. In his animations, he also misses a technical detail - during ascent, all forward-firing RCS thrusters were disabled because they didn't want any impulse, however slight, reducing the net thrust.
It's amazing what you can do with a limited computer when you know what you're doing. And if you don't, having a supercomputer won't help.
Yes, it's amazing how well the simple processors that control traffic lights work, even though they can't do anything else.
On a side note, he also scoffs at the notion that "little old ladies" could accurately thread the rope memory modules. I worked in a textile plant in my younger days and some of the highest paid workers in my department were the "hookers"; women who threaded ends through a thing called a heddle, which controlled the pattern woven into the cloth.
Something like this:
(http://i627.photobucket.com/albums/tt353/jarvisn/thrdloom_zps6e901033.jpg)
A thousand or more ends and they all had to be right or when the loom started up the resulting product would be unusable. You can believe that the ones who kept their jobs got it right first time, every time.
So this...
(http://i627.photobucket.com/albums/tt353/jarvisn/rope_Plate_18-520x379_zps7c3460d8.jpg)
...was just another day at the office - probably actually easier than their usual job.
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The interesting thing is how the ratio of speed to memory has changed. A modern computer is a thousand times faster than the AGC but it takes far longer to process all of its memory. It took the AGC only 0.4 seconds to read all of its core rope; it takes my computer well over 7 hours to read one of its 4 TB hard drives at full disk speed.
Another factor is that embedded systems often execute directly from storage. Some don't even have the ability to execute from RAM. On startup, they don't need to read or write their memories, they just need to run some code to initialize their working memory. In some cases, the most time consuming task is waiting for the power supply to stabilize.
In the case of the AGC, there was read-only core rope memory and and the writable but still non-volatile core memory. There was no executable code that needed to be loaded into memory on startup, as everything was already there ready to be executed.
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Another factor is that embedded systems often execute directly from storage. Some don't even have the ability to execute from RAM.
Right, that's why I said it was a little dodgy to compare core rope with a hard drive, as the AGC could directly execute out of the former. They also differ in other ways besides size.
Even flash memory is more like a hard drive than core rope, as you can't execute directly out of it either (not the NAND type, anyway). You have to copy it into RAM and execute it from there, and to do that you need some true ROM that you can execute from directly. General purpose computers don't use it for much more than the initial bootstrap, but as you say embedded systems use it much more.
It's fun to think that the first microcomputer I built circa 1976 with the Intel 8080 was very roughly comparable to the AGC in speed and memory, but the cost was already many orders of magnitude lower. Of course it didn't meet the same reliability specs...
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In his animations, he also misses a technical detail - during ascent, all forward-firing RCS thrusters were disabled because they didn't want any impulse, however slight, reducing the net thrust.
Did you mean disabling the upward firing RCS thrusters from operating directly against the main engine? Still, I suppose that to most efficiently maintain attitude during both ascent and descent it would be even better to use only the four downward firing thrusters, one or two at a time, to provide roll and pitch corrections. The net effect would be to move the main engine laterally a little depending on the duty cycles of the four thrusters. You might still have to fire a lateral thruster or two if you needed to make a yaw correction, but you wouldn't have to fire any upward thrusters.
On a side note, he also scoffs at the notion that "little old ladies" could accurately thread the rope memory modules.
Yup. It's a good example of his many arguments from incredulity. This is a very popular denier tactic that I think derives from simple hubris, as well as a lack of imagination. He's the smartest person on the planet (why, he has a degree in aeronautics!) so if even he can't figure out how to do it, why, no one else possibly could either!
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Even flash memory is more like a hard drive than core rope, as you can't execute directly out of it either (not the NAND type, anyway). You have to copy it into RAM and execute it from there, and to do that you need some true ROM that you can execute from directly. General purpose computers don't use it for much more than the initial bootstrap, but as you say embedded systems use it much more.
The smaller embedded processors do execute directly from NAND flash. Some of the fancier ones have controllers that read and buffer multiple instructions at once, but this is still all in the flash controller hardware, not in RAM. On many of these, instructions are read via a physically separate bus that's dedicated to the flash, and it's actually impossible to execute code from RAM...Harvard architecture as opposed to von Neumann architecture.
It's only when you get to relatively large and fast systems that you need to load code into RAM before execution.
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Ah, I see. I know NAND can't be randomly accessed a word at a time, so you need something between it and a CPU.
Modern CPUs heavily decouple their RAM operations through their caches, with I/O being done a line at a time, so it makes sense that something similar would be used with flash.
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In his animations, he also misses a technical detail - during ascent, all forward-firing RCS thrusters were disabled because they didn't want any impulse, however slight, reducing the net thrust.
Did you mean disabling the upward firing RCS thrusters from operating directly against the main engine?
I should know better than to speak English around engineers. Yes, it was the +X thrusters that were disabled. I don't remember at this moment where I read that, but I'm sure it was either a NASA document or an account by one of the astronauts.
Hunchy also gets hung up on the two-second guidance cycle which was designed to (as I understand it) allow any errors to get large enough to be correctable; he uses that number to claim that the AGC's memory cycle time was two seconds (it was actually 11.7 milliseconds), which would have been hopelessly slow. I still can't decide whether he's a <insert mentally-challenged epithet of your choice> or deliberately deceptive. It's just hard for me to accept that someone who seems to spend as much time as he does poring over NASA documents in search of "jokes" has no comprehension of what he's reading.
Side Comment: BTW, Hal Laning really should have been given a Nobel Prize in Engineering (if there were such a thing) for the software he basically made up from scratch to largely error-proof the AGC.
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Ah, I see. I know NAND can't be randomly accessed a word at a time, so you need something between it and a CPU.
You can read as little as you like, there's nothing stopping you from taking just a subset of the bits available. This doesn't work for erase and write operations, though. (But those are relatively rare and unusual operations for these chips.)
The chip on this board is the smallest I've encountered with something resembling an actual cache:
http://www.st.com/web/en/catalog/tools/FM116/SC959/SS1532/PF252419
A full 1 MB of flash, and even has a FPU. 168 MHz, much too fast to read each instruction individually, so it's got a fancy "ART Accelerator", an instruction prefetch queue and branch cache.
Modern CPUs heavily decouple their RAM operations through their caches, with I/O being done a line at a time, so it makes sense that something similar would be used with flash.
Interestingly, that chip does the opposite. The RAM is divided into two contiguous but independent 112 KB and 16 KB blocks on the system bus and a separate 64 KB block coupled directly to the core. Peripherals can't access the last one for DMA, but the core doesn't have to compete with peripherals for access...you could have DMA transfers going on with both main blocks while the core's working on something else. (there's also a 4 KB battery-backed RAM block tucked away with the RTC registers)
For comparison: http://www.ti.com/ww/en/launchpad/tiva_c_head.html
At 40 MHz or below, it just reads each instruction from flash as needed, and uses a simple prefetch queue at higher speeds.
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I should know better than to speak English around engineers. Yes, it was the +X thrusters that were disabled.
Those would have been the -X thrusters, then. The nozzles pointed up along the +X axis, but the thrust they produced was in the -X direction.
Hunchy also gets hung up on the two-second guidance cycle which was designed to (as I understand it) allow any errors to get large enough to be correctable; he uses that number to claim that the AGC's memory cycle time was two seconds (it was actually 11.7 milliseconds), which would have been hopelessly slow.
I've noticed that too. I think the 2 second SERVICER cycle had to do only with numerical integrator that updated the state vector (estimated position and velocity). The accelerometers themselves had built-in integration so on each 2 second cycle you'd accurately account for the total impulse experienced over the previous two seconds even if it fluctuated during that time. But I'll have to check this.
The response time of the RCS to attitude errors was clearly faster than 2 sec because we can see it in the 16mm movies of the ascents.
I think the memory cycle time was 11.7 microseconds, not milliseconds.
I still can't decide whether he's a <insert mentally-challenged epithet of your choice> or deliberately deceptive. It's just hard for me to accept that someone who seems to spend as much time as he does poring over NASA documents in search of "jokes" has no comprehension of what he's reading.
Me too. Most of the time I think he's sincere, but occasionally he really stretches my willingness to follow Hanlon's Razor (never attribute to malice that which can be attributed to stupidity). Like right now, in his claims about the asymmetry of the ascent stage being a deliberate joke by the engineers. He seems to be going well out of his way to misunderstand my very simple explanation: that the ascent fuel and oxidizer had very different weights, forcing the tanks to be mounted asymmetrically to bring the stage back into balance.
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I should know better than to speak English around engineers. Yes, it was the +X thrusters that were disabled.
Those would have been the -X thrusters, then. The nozzles pointed up along the +X axis, but the thrust they produced was in the -X direction.
Picky, picky, picky. I meant the thrusters whose nozzles pointed in the +X direction witch would, yes, have produced thrust in the -X direction.
I think the memory cycle time was 11.7 microseconds, not milliseconds.
Right, microseconds. My fingers stuttered.
Me too. Most of the time I think he's sincere, but occasionally he really stretches my willingness to follow Hanlon's Razor (never attribute to malice that which can be attributed to stupidity). Like right now, in his claims about the asymmetry of the ascent stage being a deliberate joke by the engineers. He seems to be going well out of his way to misunderstand my very simple explanation: that the ascent fuel and oxidizer had very different weights, forcing the tanks to be mounted asymmetrically to bring the stage back into balance.
Hunchy reminds me of those religious fanatics who take a single line of scripture and build up a complex theological principle from it. (My father used to call it "Making a lot of stew from one oyster".) He has fixated on the phrase from David Hoag's GNC Progress Report (E-2411):
"...the system estimates the torque arising from the offset of the main engine thrust from the center of gravity."
along with the visual asymmetry of the ascent stage and decided that the CoG and thrust axis were deliberately misaligned. He totally disregards the fact that the CoG is a bit of a moving target, being affected by equipment stowage, crew movement, propellant usage, etc.
His whole argument seems to be that the design (that he imagines) would have been wasteful of RCS fuel and would have carried the risk of running out of propellant, leaving none for maneuvering for rendezvous. Even IF it were designed that way, don't you think they would have allowed for that in their fuel calculations?
As you say, he does seem sincere. But knowledgeable he ain't.
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I've noticed that too. I think the 2 second SERVICER cycle had to do only with numerical integrator that updated the state vector (estimated position and velocity). The accelerometers themselves had built-in integration so on each 2 second cycle you'd accurately account for the total impulse experienced over the previous two seconds even if it fluctuated during that time. But I'll have to check this.
Correct; SERVICER performed dead reckoning at 0.5 Hz. In accelerated flight the guidance loop operated at 10 Hz.
Me too.
And me. It's still difficult for me, after more than a decade of this debate, to see how anyone who professes to be a qualified professional can be so devastatedly obtuse and not have that be a deliberate behavior. Yes, I'm ignoring the possibility of mental illness, but that's deliberate. I don't know of any specific illness with these symptoms, and I have no evidence for that cause.
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along with the visual asymmetry of the ascent stage and decided that the CoG and thrust axis were deliberately misaligned. He totally disregards the fact that the CoG is a bit of a moving target, being affected by equipment stowage, crew movement, propellant usage, etc.
Yes, he totally disregards the entire science of spacecraft dynamic control. Where to begin...
First of all, the conceptual control axes for the LM were not orthogonal, as was the case in the other spacecraft. This bias was intended to correct for the fact that the LM flew "forward" for a great deal of the landing. And nowadays we are perfectly happy with non-orthogonal control axes; we deliberately do not align reaction wheels along cardinal axes or in orthogonal planes precisely so that we can use a subset of them to maintain control after the failure of a wheel.
Second, no RCS design or control law, or indeed any accelerated-flight control law, requires the spacecraft to have "aligned" mass properties. Such a thing is impossible to achieve in practical design, and further impossible (if that concept means anything) to maintain in normal operation or powered flight. No method of flying a spacecraft has ever relied on delicately balancing the mass properties so as to require no imposed pointing control. Even the basic skyrockets from thousands of years ago required arranging the center of (aerodynamic) pressure to provide a corrective moment.
Third, the RCS system provides control moments. The jets do not fire continuously during powered flight. The spacecraft, as all spacecraft do, wanders around its deadband until a control moment is required.
Fourth, on the ascent the RCS was operated in pulse mode because it was too powerful for the largely empty spacecraft. It was sized to provide adequate control moments for the docked and fully-fueled spacecraft.
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How does Hunchy, with all his claimed brilliance, miss these small basic things?
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How does Hunchy, with all his claimed brilliance, miss these small basic things?
Deliberatly, I think.
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How does Hunchy, with all his claimed brilliance, miss these small basic things?
Hence why I can't accept that he's an engineer of any kind.
And in one sense these are small basic things. But in another sense they're the whole enchilada. They express a fundamentally different way of conceptualizing the spacecraft dynamic control problem than what a layman would probably envision intuitively, even a smart one.
After building a few actual spacecraft, you learn there is no optimal RCS placement. Further, other design constraints may disallow placing RCS jets where even a marginally optimal solution suggests. You quickly learn that a completely generalized vector solution (i.e., a linear algebra system) is the only way to keep from having to solve this problem minute-by-minute, spacecraft-by-spacecraft. Once you invoke this mathemagical world, you realize that you pretty much just solved every spacecraft dynamics problem, because they just become parameterized versions of the general solution. Yet the result and method are often inscrutable to the layman. The layman is still stuck on getting everything lined up perfectly to simplify the piecewise solution. Without that alignment, the piecewise solution grows into unmanageable complexity.
Most people intuitively understand inertia and momentum. That is, they know that the product of mass and velocity results in a quantity that has a real-world measurable value. An unladen shopping cart (trolley) hitting your ankles at high speed causes pain of the same approximate magnitude as a heavy-laden one hitting at slow speeds.
From this we can introduce the moment of inertia, which is its rotational equivalent. The product of mass and velocity is still salient, but velocity in this case is how fast it's spinning. But then we realize that it depends which way we rotate. Things that are long and thin rotate more easily about one axis than the other. It complicates the reckoning of dynamic stability and control, so when playing Quidditch, the broom perhaps rolls more easily than it pitches or yaws.
The mathematically disinclined reader starts to get a headache at this point. But we again invoke linear algebra. This misnamed branch of math, among its many uses, has the practical use here summed up by: "It's a way to reason in general about several directions at once." In this world, instead of thinking about the three cardinal directions (roll, pitch, and yaw), we think about all conceivable directions simultaneously by expressing them as rotations relative to roll, pitch, and yaw. You don't have to understand this. But what comes out of this is that moment of inertia, in real-life spacecraft control, is a matrix, not a formula. Nine numbers, properly specified, give the moment of inertia of any body, in any axis. Or in more direct terms -- of every spacecraft that could ever be built, anywhere, by anyone.
Once you start expressing the problems and solutions in linear algebra terms, basic concepts like moment of inertia and RCS control inputs share the same visual appearance: that 3x3 matrix. And so do complex topics, like damping the effect of fuel slosh in the tanks. It's all the same stuff. Relatively advanced mathematics, but a very elegant solution.
Then when you realize that linear algebra doesn't require your reference axes and control axes to be strictly orthogonal (i.e., all at right angles to each other), you achieve another step in the generality of the solution.
And this straightforward (while admittedly math-heavy) progression from basic concepts to a fully generalized solution is what gives us the lunar module. The LM had non-orthogonal control axes, and shared a property with the CSM that it could operate with various individual RCS jets disabled. The layman, who is thinking of firing certain specific control jets to, for example, correct a roll error, shudders in horror at what he'd do if those individual jets weren't available. The engineer, with the generalized solution painstakingly achieved through analysis and theory, sits back and says smugly, "Hey, no problem." To the layman it looks like magic. It isn't; it's just math. But the ability to comprehend this kind of physics solution (or, at the limit, that such a solution is theoretically possible) is the kind of thing that separates engineers from non-engineers. Not as a value judgment, but as a qualitative difference in the mode of thought.
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First of all, the conceptual control axes for the LM were not orthogonal, as was the case in the other spacecraft.
How so? The thrusters certainly appear to be orthogonal to each other, although yesterday I noticed in a drawing (you know, the ones that don't exist) that the ascent engine appears to be rotated slightly forward (i.e., producing a component of thrust in the +Z direction). I also noticed that the c.g. of the Apollo 11 LM at lunar liftoff was at Z=+2.9 inches and moved forward to Z=+5.3 inches at insertion. These two facts are probably not unrelated.
I did read that the computer used control axes rotated 45 degrees around the X axis. But this was just to simplify the software by aligning them with the RCS thruster quads on the corners of the ascent stage. The axes were still orthogonal with each other.
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Third, the RCS system provides control moments. The jets do not fire continuously during powered flight. The spacecraft, as all spacecraft do, wanders around its deadband until a control moment is required.
I know what deadbands are, but let me make sure I understand why they're used.
If the RCS thrusters could be throttled, or if they could be efficiently fired for arbitrarily short intervals so they could be pulse modulated as if throttled, then the guidance system could fire them continuously at whatever thrust is needed to keep the stage dynamically balanced. You wouldn't need an attitude deadband.
But real thrusters take time to open the valves and further time for fuel and oxidizer to flow, contact and ignite. Before ignition, some unreacted propellant is expelled. The shorter the burn, the more of the total propellant is wasted. So you want to fire the thrusters for longer periods, which means firing them less often. And that means having to tolerate some attitude error.
A secondary reason for a deadband is that the c.g. may dynamically move during flight, e.g., as propellants slosh in their tanks. (Crew movement is another possibility but they're strapped in place.) Trying to hold attitude tightly against these small movements means firing opposing engines and wasting propellant. It's better to just relax and tolerate the error.
I presume the optimum deadband can be computed from the loss in effective thrust that comes from a particular attitude error. This varies as the cosine of the error, which for small angles is approximately 1 -- i.e., small errors are inconsequential. So the optimum deadband would be the one that equates the RCS propellant needed to maintain it with the wasted propellant by the main engine due to those cosine errors.
Am I right?
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In connection with Hunchbacked's refusal to accept that the LM design engineers actually knew what they were doing, he continues to insist that the zig-zag motion of the LM as seen from the LRV camera on Apollo 17 was caused by the LM correcting for its seriously off-balance design!
I keep trying to explain, to no avail, how the camera had two drive motors that ran at a constant speed that did not match the apparent speed of the LM. The operator had to repeatedly start and stop them to keep the LM within the field of view, and this resulted in the apparent triangular motion of the LM on the screen (he calls it "sinusoidal"). He even notes that the apparent oscillations of the LM are vertical rather than horizontal as he'd expect from attitude oscillations, but even this doesn't tell him that he needs to reconsider his basic premise.
Amazing.
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I guess when on old Star Trek they do a lean and camera tilt, he thinks they tilt the whole set.
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Even though the chairs never move. That's the part I like.
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I believe they did, by TNG, because they could by then afford a tilting set.
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I believe they did, by TNG, because they could by then afford a tilting set.
I think even then. Galaxy Quest *did* use gimbals when on the 'real' Protector though.
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I believe they did, by TNG, because they could by then afford a tilting set.
The only ST productions of any kind, movie or TV, that used a physically tilting bridge set were The Undiscovered Country and Nemesis. In all the others, camera tilt was used, and the lurching movements were made by the actors.
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In all the others, camera tilt was used, and the lurching movements were made by the actors.
Right. That's what made it so great. While the actors are trying to lurch and roll in unison, the chairs just stand there even though they're unattached to the floor, unless one of the actors knocks it over.
And then we have Dr. McCoy's extensive glass display cases in sick bay featuring skulls, liquor bottles and such. And none ever budge, even when the ship is under heavy attack by phasers and photon torpedoes.
Obviously whatever machine they use to cancel the subjective effects of accelerating to several times the speed of light in a few seconds also cancels brief accelerations due to nearby explosions -- but only for inanimate objects, not people. Unless it's necessary for the plot of course.
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And then we have Dr. McCoy's extensive glass display cases in sick bay featuring skulls, liquor bottles and such. And none ever budge, even when the ship is under heavy attack by phasers and photon torpedoes.
Whaddya mean glass!!!? They were made of transparent aluminium!!!
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How does Hunchy, with all his claimed brilliance, miss these small basic things?
In his first video he put up he presented the Apollo 8 'earthrise' photos and proudly proclaimed that they could not have been taken from the surface of the Moon.
I wish I had saved that one.... he took it down fairly quickly.
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In his first video he put up he presented the Apollo 8 'earthrise' photos and proudly proclaimed that they could not have been taken from the surface of the Moon.
I wish I had saved that one.... he took it down fairly quickly.
Apparently he does have a sense of shame then.
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It's maybe worthwhile asking him about that video, as he'll loose credibility real fast with the fence sitters. Similar to the Aldrin/underwater video (of which a reference copy still exists) he quickly removes things that raise the ire of his teammates.
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I did read that the computer used control axes rotated 45 degrees around the X axis. But this was just to simplify the software by aligning them with the RCS thruster quads on the corners of the ascent stage. The axes were still orthogonal with each other.
That's what I was referring to. The control axes for the LM form an orthogonal basis, but are not coincident with the spacecraft body-axis basis as is usually the case. I went back to check, using the same drawing you saw (but which I haven't looked at for, oh, about three years). I conflated that with the reaction-wheel technique, which can have a non-orthogonal control basis.
For those who are lost, "orthogonal" has a geometric meaning that indicates something at right angles to a reference. It has a theoretical meaning suggesting independence of control action. Ideally we want roll control to result only in a roll moment, and not cause unwanted pitch or yaw. In practice, because no statically ideal RCS solution exists and no spacecraft has invariable mass properties, you can't have one control action without residual, collateral response in some other axis. If your pitch thrusters are slightly off-center, trying to pitch up may also roll you slightly. Hence an automatic control system will also apply compensatory roll moments with the roll thrusters to result in a "pure" pitch maneuver.
Abstractly considered then, this "messy" property actually simplifies things by requiring control laws not to assume orthogonality. And then, for other reasons, it can be made deliberately orthogonal. Which is to say, in thruster terms, they don't always have to be aligned with the body axes, or even at right angles to each other. Commanded moments are then achieved by firing the combination of thrusters that produce an appropriate vector in the navigation basis. And this is why, when you watch the actual Apollo spacecraft or the space shuttle closely, maneuvers employ a symphony of thruster firings that are more involved than just the simple, canonical moments. Mathematically, a straightforward relationship exists between the body axes (relative to which attitude and rates are reckoned) and any control basis.
Reaction wheels on modern spacecraft are not aligned with the body axis and often are not installed at right angles to each other. This requires any body-axis maneuver to require actuating at least two reaction wheels. But this apparent loss is actually a win, because the wheels are arranged such that any given moment may be produced by more than one combination of wheel actuations. And this compensates for degradation or malfunction of any one reaction wheel.
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He doesn't seem to grasp the difference between the centroid of a shape and the center of mass.
That's just not something a real aerospace engineer would do. It's like someone claiming to be an expert baker getting confused between flour and paprika. Yes, they're both powders, but...
...all forward-firing RCS thrusters were disabled because they didn't want any impulse, however slight, reducing the net thrust.
Well, "however slight" isn't exactly the case. Four of the Marquardt thrusters firing in the same direction is 400 lbf of thrust. That's more than ten percent of the APS 3,500 lbf thrust -- not that they would actually be fired like that during APS-accelerated flight, but you get the idea. Those 100-lbf Marquardt motors, which fit in shoe box, were used well into the 1990s as apogee motors on geostationary satellites.
Yes, it's amazing how well the simple processors that control traffic lights work, even though they can't do anything else.
Simple is better. Well, more reliable anyway. The critical functions of both the LM and CSM were not controlled by the programmable GP computer, but rather by traditional sequential and combinatorial logic implemented largely with diodes and electromechanical relays.
On a side note, he also scoffs at the notion that "little old ladies" could accurately thread the rope memory modules.
Again, more proof that he's never actually worked in an aerospace context. Similar to your "highly-paid 'hookers'" (snicker), some of the highest-paid workers at Boeing's plant are the adhesive layup ladies who have decades of experience, a keen eye, and a steady hand. There are many skills involved in building a spacecraft, and not all of them are cerebral. ATK near me has an army of Kevlar threaders who wrap their SRM casings using machines many of them helped design and build. They're coming up on retirement, and ATK is in a bit of panic to get new ones trained and experienced.
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I know what deadbands are, but let me make sure I understand why they're used.
Well, take a couple steps back and enjoy the notion that everything you mentioned is, in one way or another, a valid argument for the use of deadbands in any control system -- especially an attitude-hold autopilot that uses rocket thrusters for control moments.
From the steps-back perspective, consider that you nailed the notion of discrete control variables. Often a control system must provide inputs that are discretes (i.e., on-off values; e.g., opening the water inlet to the washing machine), or stepwise-variable (e.g., firing up the second-stage burner in an HVAC system), or continuously variable only within a narrow band (e.g., car engine speed cannot drop below about 700 RPM, and cannot exceed red-line speed). RCS thrusters are not continuously variable. They provide either a fixed thrust, or stepwise variable thrust in pulse mode.
And in the case of the LM ascent, the thrust is vastly oversized for the need. Consider a home heater whose heating element (whether electrical resistance heater or combustion burner) has prodigious heat injection capacity. If your thermometer drops only a degree below the set-point, firing up that huge beast of a heater -- even for a very short amount of time -- may rocket your temperature several degrees above the set-point.
Before we get into the mechanics of thruster ignition transience, which is correct (but a second-order consideration), let's examine the other effect you nailed head-on, because it follows directly from what we observe above and from what you noted about the mass properties of the spacecraft. The spacecraft's center of mass changes, as you note, from fuel depletion and from other payload shifting such as fuel slosh and crew movement. The IMU on a manned spacecraft is incredibly sensitive. For example, the IMU on board Apollo 1 registered the motion of the entire launch vehicle due to the movement of the crew attempting to extinguish the fire and escape. If even the slightest measurable error produced a corrective moment, there would be constant correction, overcorrection (due to non-discrete controls), and a non-stop fight between opposing controls. Deadbands provide vital slack to prevent this. Other techniques include more sophisticated control laws that incorporate integrated and differential process variables. The Apollo digital autopilot implemented differential control (i.e., error rates) plus a pilot-selectable deadband.
And yes, the goal is simply "good enough" guidance, not error-free guidance.
The other concern is the classic hysteresis effect. Between the time an error is first measured to the time the system returns to acceptable is an interval during which the system is reacting. It may take only a few milliseconds for the error to generate a control input, but it may take considerable time -- perhaps several cycles of the control system -- for the control input to be reflected in the process variable. When your thermostat notes that the measured temperature in the room matches the set point, it stops adding heat to the room by turning off the heating element. But because of latency in the distribution system and latency in the thermometer, heat may continue to enter the system and cause the measured temperature to rise. Thus, aiming instead at a deadband rather than at a precise value allows for overshoot and latency in the control loop.
Spacecraft sometimes have this constraint. There are missions that require attitude errors to be corrected within a certain time proportional to the error magnitude. That is, you can accept a certain magnitude of error, but you cannot accept an out-of-tolerance condition for very long. So sometimes time-optimal control is required, not fuel-optimal control. Different control laws, and different deadband requirements.
I presume the optimum deadband can be computed from the loss in effective thrust that comes from a particular attitude error. This varies as the cosine of the error, which for small angles is approximately 1 -- i.e., small errors are inconsequential. So the optimum deadband would be the one that equates the RCS propellant needed to maintain it with the wasted propellant by the main engine due to those cosine errors.
Am I right?
Well that's one way to formulate it, yes. The science of spacecraft guidance is a tool kit of all such kinds of models that match various mission constraints. Many modern missions are orbital only, and rely chiefly upon attitude control -- pointing constraints. Planetary missions have constraints more in line with Apollo ascent guidance, and are reckoned in terms of allowable dispersion. Dispersion on orbital approach is expressed as an allowable window in the state vector -- a literal geometric window in planet-fixed space through which the spacecraft must fly, and a conical distribution of acceptable velocity vectors. Dispersion for landing is the landing-site ellipse. Dispersion for rendezvous can be expressed as tolerances on the sacred 6-tuple of orbital elements.
Abstractly considered, dispersion simply accepts that no matter how adept a guidance system may be, identical starting conditions will not result in arbitrarily repeatable end conditions, due to the accumulation of low order effects that do not repeat. Guidance dispersion is therefore simply the error analysis for guidance. And each mission (e.g., LM ascent and rendezvous) contains an acceptable dispersion. For most LM ascents, the acceptable dispersion was vast. In contrast, for LM landing on Apollo 12, acceptable dispersion was considerably narrow.
So the more accurate expression of your sentiment above is how much known guidance error can I accept, integrated (and hopefully averaged) over ascent time, and still "land" in orbit with only nominal dispersion. It's not so much the loss of thrust because the motor is slightly off-axis, but rather the naked fact that you're going the wrong direction. So you can write the optimization problem several ways now. You can optimize the deadband, for example, to balance between fuel for control during the ascent against fuel to correct the orbit.
In practice the Apollo deadband was simply switched between two fixed values, depending on the pointing constraint for the specific mission phase. The deadbands were 1 degree and 0.1 degree, respectively, if I recall correctly.
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Even though all this is well understood now (at least by you engineering types), a lot of it is counter-intuitive.
Remember back in the day when even intelligent, well educated aeronautical engineers were surprised by the "inertial coupling" phenomenon - also known as "the damn thing just came uncorked" - in supersonic flight which killed at least one test pilot and tried very hard to kill a few others, including Chuck Yeager.
Which seems to me just another argument that Hunchbacked has no significant engineering knowledge, whatever his claims may be.
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Apparently he does have a sense of shame then.
That's very hard to believe.
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For example, the IMU on board Apollo 1 registered the motion of the entire launch vehicle due to the movement of the crew attempting to extinguish the fire and escape.
IIRC, it sensed vehicle motion even from minor crew movements before the fire, such as somebody shifting in his couch. There's also a belief that Grissom may have been out of his couch trying to fix a balky headset connector (they were having comm problems at the time).
The other concern is the classic hysteresis effect. Between the time an error is first measured to the time the system returns to acceptable is an interval during which the system is reacting.
Right, and here there is unavoidable lag in the control loops -- the sensors and the computers -- as well as in the actuators (the thrusters). Not only did it take time to open the propellant valves and build up chamber pressure, but the thrusters didn't stop producing thrust the instant the valve-close command was given. There was a tail-off period.
Dispersion on orbital approach is expressed as an allowable window in the state vector -- a literal geometric window in planet-fixed space through which the spacecraft must fly
I know what dispersion is, but I'm asking about something different. The issue is not accuracy but efficiency. Like most spacecraft the LM uses a closed-loop guidance system. It knew where it was (to some accuracy) and where it wanted to be, and it computed and executed what it had to do to get there. How it gets there isn't as important; many paths led to the same end point but not all of them were equally efficient.
In a random walk, your final distance from the starting point increases only as the square root of the number of steps. So it can be more efficient to let small random deviations from the path build up and fix their sum later than to spend more fuel to fly a much tighter path all the way, even though that eliminates the later correction.
Up to a point, of course. So there must have been an optimum deadband that minimized the total propellant (main engine + RCS) required to reach a given target state vector with the same given accuracy.
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Well, "however slight" isn't exactly the case. Four of the Marquardt thrusters firing in the same direction is 400 lbf of thrust. That's more than ten percent of the APS 3,500 lbf thrust -- not that they would actually be fired like that during APS-accelerated flight, but you get the idea.
With that we should be able to easily compute how far off the c.g. could be for the thrusters to still correct for it.
Let's assume the c.g. is somewhere along a diagonal line between the 3,500 lbf APS and the left front thruster. Each thruster is 100 lbf, so if the distance of the c.g. from the X axis (and APS thrust vector) was 1/(35+1) = 1/36th of the distance between the APS and the thruster, they would have produced equal and opposite torques with a 100% duty cycle on the thruster.
My best drawings of the LM don't include dimensions, but I can scale it from another drawing that gives the distance between opposite faces of the descent stage as 13 feet 10 inches (4.216 m). From that I estimate that the left front thruster is 2.33 m diagonally from the X axis. 1/36 of that is 6.5 cm. At this point, the thruster would have to fire 100% of the time to keep the LM on course. If the c.g. were even farther off center the guidance system would have to begin firing the -X (upward firing, downward thrusting) thruster on the right rear, and that would work against the thrust of the main engine.
What were the actual numbers? At ascent, the Apollo 11 LM c.g. was at (+243.5, +0.2, +2.9) inches. That's only slightly to the right of the thrust vector but actually rather significantly (7.4 cm) forward. This may explain why my same drawing appears to show the ascent engine canted slightly forward. If accurate, it indicates that the designers knew where the c.g. would be and mounted the engine accordingly. If I were them, I would have made it manually adjustable before flight.
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...And yes, the goal is simply "good enough" guidance, not error-free guidance.
...So the more accurate expression of your sentiment above is how much known guidance error can I accept, integrated (and hopefully averaged) over ascent time, and still "land" in orbit with only nominal dispersion.
Even though it's something I sort-of knew, it's still interesting to read here the idea that you don't have to guide a spacecraft perfectly, you merely have to guide it well enough (to get the job done). I assume therefore that the reason various mid-course corrections on Apollo missions weren't used was because the trajectory errors at the time weren't large enough to warrant correcting.
On top of this, I'm reminded of a poster called Donde at the late lamented Self Service Science Forum. Apart from his...unique...idea that pi had multiple possible values, he was convinced it would be impossible for humans to ever send spacecraft to the stars: because we wouldn't be able to aim them accurately enough. No matter how we tried to explain it, he simply wouldn't accept the idea that a hypothetical interstellar spacecraft would be able to determine how much its trajectory was deviating from the required course, and would also be able to make corresponding course corrections. In contrast he seemed to think that spacecraft were like bullets, that once fired couldn't be redirected.
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If I were them, I would have made it manually adjustable before flight.
Do you mind me asking why?
For one thing, any sort of adjustment mechanism would add weight on a spacecraft where gaining weight was looked on as worse than it is for Miss Universe.
And for another, what's wrong with calculating where the CoG will be beforehand, setting the aim of the APS during construction of the LM on the basis of those calculations, and leaving any fine management of the ascent trajectory to the RCS?
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Do you mind me asking why?
Sure. It gives you operational flexibility. Each mission carried a different crew, whose body weights varied at least a little, visited a different area of the moon and stayed for varying amounts of time, carrying different equipment and amounts of consumables down to the surface and samples back from the surface. The change was the largest between Apollos 14 and 15, the last H-mission and first J-mission.
I'm not talking about anything fancy, just an adjustable mounting bracket that would allow the engine mount to be swiveled a little before being torqued down. The bolt holes would actually lower the weight a little. :)
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Not only did it take time to open the propellant valves and build up chamber pressure, but the thrusters didn't stop producing thrust the instant the valve-close command was given. There was a tail-off period.
The Marquardt 100-lbf jets have a transient measured in a small number of milliseconds, not really something you really worry about in a 10 Hz control loop. Does it contribute to latency? Yes, a bit. But ordinary process latency (e.g., moment divided by moment of inertia, integrated over time) is the cardinal limit.
Like most spacecraft the LM uses a closed-loop guidance system.
Well, yes and no on the LM ascent. The DAP was then, and always was, closed loop at the perspective of attitude errors and error rates. But the attitudes that the ascent guidance system fed into the DAP were static, stepwise values. At the high level, LM ascent guidance was open-loop.
In a random walk, your final distance from the starting point increases only as the square root of the number of steps. So it can be more efficient to let small random deviations from the path build up and fix their sum later than to spend more fuel to fly a much tighter path all the way, even though that eliminates the later correction.
I see now where you wanted to go with that, and I agree. Indeed, the overall goal of the deadband is to allow errors to accumulate to the point where it's efficient to correct them. I never really misunderstood that or quibbled with it, but I was thinking about different ways of reckoning efficiency. A small-tolerance ascent path leads to minimal errors in the final orbit, but necessarily consumes more fuel to keep the tolerance tight. A large-tolerance ascent path opens the door (pun intended) to requiring a large correction after insertion, because the accumulated errors resulted in too great an error in the orbit. And that too requires fuel. On the LM those fuels come from the same source and can be globally optimized. On the CSM, for example, the RCS and SPS had different fuel sources, so it might be better in that case to decide which fuel source is more important to conserve. But the great thing about sloppy tolerances is that they're often sloppy in both directions such that they average out, and you end up adequately "bouncing between the guardrails" to get to your destination.
Up to a point, of course. So there must have been an optimum deadband that minimized the total propellant (main engine + RCS) required to reach a given target state vector with the same given accuracy.
Undoubtedly. Any solution can be optimized, and I see what you're doing to dig away at the theory of it. I think you're onto something.
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Well, yes and no on the LM ascent. The DAP was then, and always was, closed loop at the perspective of attitude errors and error rates. But the attitudes that the ascent guidance system fed into the DAP were static, stepwise values. At the high level, LM ascent guidance was open-loop.
Right, my apologies for being imprecise. By "closed loop" I meant that you command the DAP to a given attitude, and it would then continuously read the gyros and fire the thrusters as needed to get there and hold that attitude, within a specified deadband.
A question on terminology: what is the specific job of a spacecraft "autopilot"? Does the autopilot only seek and maintain an externally specified attitude, or does the term include determining what that attitude needs to be, either open or closed loop?
On the LM those fuels come from the same source and can be globally optimized. On the CSM, for example, the RCS and SPS had different fuel sources, so it might be better in that case to decide which fuel source is more important to conserve.
Right, and I've wondered why it was done that way. Was there a lot of uncertainty in how much fuel the LM RCS would need? I can see that there might be. You don't know how much the CDR will need during his manual approach and landing on an unknown terrain, and you can't always control the c.g. position on ascent as tightly as you'd like.
The Marquardt thrusters were designed to burn MMH, and they had to be requalified for Aerozine-50. It's tempting to think that they're almost the same thing as each hydrazine molecule in Aerozine-50 has, on average, one methyl group just like MMH. But chemistry doesn't always work that way...
But the great thing about sloppy tolerances is that they're often sloppy in both directions such that they average out, and you end up adequately "bouncing between the guardrails" to get to your destination.
Exactly why, in a random walk, the expected distance from the start increases as only the square root of the number of steps; some of each error cancels out some of the previous errors, so there's no point in correcting individual errors too soon. Wait to see what the vector total will be, and then correct it in one step.
Undoubtedly. Any solution can be optimized, and I see what you're doing to dig away at the theory of it. I think you're onto something.
Given how much analysis went into propellant optimization all over Apollo, I'm sure someone must have looked at this very closely.
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On a side note, he also scoffs at the notion that "little old ladies" could accurately thread the rope memory modules.
Perhaps he should be directed to the Spacecraft Films 2-DVD set "Mission to the Moon" where he can view some early NASA documentaries in black-and-white and, in the programme about the AGC, see with his own eyes the "little old ladies" doing the threading.
http://02e5a89.netsolstores.com/missiontothemoon.aspx
The presentation of some of the programmes is quaint and amusing, but nevertheless they are very informative. Occasionally the interviewees are stiff as a board and look a bit like possums caught in the headlights -- terrified of the camera and dearly wishing they could get back to the job they know best.
Mission to the Moon
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Man's first steps on the moon took an incredible effort by thousands of dedicated workers. In this 2-DVD set you'll see how the Apollo program took men to the moon through in-depth programs created for NASA in conjunction with M.I.T. Each of them focuses on a specific topic presenting in-depth information and hands on demonstrations of how hardware was built and operated. Most of the programs are in black and white but are some of the most informative pieces on Apollo hardware and procedures we've ever seen. Over 5 hours of material on 2 DVDs.
Contents:
THE FLIGHT OF APOLLO 4 - NASA program on the development of the Saturn V launch vehicle and the successful first flight of the vehicle in November of 1967. Color. (14:30)
FIRST SOFT STEPS- Program takes an in-depth look at the lunar pathfinders, including Ranger, the Lunar Orbiter, and Surveyor missions. These pathfinders built confidence in Apollo design and procedures prior to the first manned visits to an unknown environment. Black and White. (28:30)
FOOD FOR SPACE TRAVELERS - Development of food for space travelers, particularly during the Gemini missons and in preparation for Apollo. Filmed at the U.S. Army labs. Black and White. (28:30)
ROOM AT THE TOP - Program on the Apollo command and service modules, their development, operation and roll in the Apollo moon landings. Filmed at the North American plant at Downey, CA. Includes looks at the the internal configuration and the construction of the hardware. Black and White. (28:30)
COMPUTER FOR APOLLO - Examines the Apollo guidance computer as well as the operation of the computer in conjunction with the navigation scopes in the command module. Shows operation of the DSKY as well as the computer hardware used in Apollo. Filmed in the lab at M.I.T. Black and White. (28:30)
POWER FOR THE MOONSHIP - In-depth look at the fuel cells developed for the Apollo CSM, including a demonstration on how the fuel cell stack is built up, showing the chemical process of power generation and the waste products, including drinking water for the spacecraft. Filmed at Pratt and Whitney. Black and White. (28:30)
LANDING ON THE MOON - Tom Kelly leads a tour of the development of the Grumman lunar module, including an exterior and interior visit, and a comprehensive view of how the lunar lander is built. Filmed at Grumman at Bethpage. Black and White. (28:30)
SUITED FOR SPACE - Covers the development of the suit required to keep the astronauts alive as they explored the moon. Black and White. (28:30)
SPACE MEDICINE - Filmed at Johnson Space Center, Houston, this program deals with the physiological concerns of human space travel, especially as it relates to the lunar missions. Includes demonstration of a variety of results from previous flights as well as studies being conducted on space medicine. Black and White. (28:30)
RETURNING FROM THE MOON - Speeds returning from a lunar mission required massive protection of the command module from the heat of entering the Earth's atmosphere. Filmed at Langley and at AVCO, the contractor for the Apollo heatshield, the construction of the heatshield is demonstrated, including subjecting a sample to a hot jet, demonstration of the honeycomb bonding to the spacecraft as well as the shooting of the resin ablator into the honeycomb with a "gun." Also examined is the testing of splashdown and possible land impact. Black and White. (28:30)
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Il est français, je pense.
His name is Xavier Pascal. He claims to have graduated from a French university and I've seen posts he's written in French.
I guess it's him, then, who has a page at the Aulis web site with a lengthy exposition claiming the AGC wouldn't work. He started off by claiming that it couldn't control the spacecraft because it would take too long to get updates from the ground computers if anything went astray - apparently spacecraft on translunar trajectories are prone to suddenly lunging off course if not constantly corrected, which would be news to controllers watching, say, Pluto-New Horizons. (The AGC's inability to provide realtime flight control would also be news to the pilots who flew the F-8 Crusader using an AGC for the first fly-by-wire aircraft tests.)...
I mentioned the Apollo conspiracy claims to a guy I work with. Turns out his first co-op job with NASA was working on precisely that project.