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Post by ka9q on Jan 28, 2012 14:01:12 GMT -4
I see one big oversight in that thread, though it was briefly mentioned: the effect of the atmospheric pressure drop. That's increasingly important with the switch in cabin atmospheres from pure O2 at 5 psi to ordinary air at 15 psi. Though of course you're more likely to actually need this propulsive capability while in an EVA suit, and they're still pure O2 at low pressure.
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Post by ka9q on Jan 28, 2012 13:49:56 GMT -4
playdor ... what exactly is your point with all these numbers? Yes, what's your point? The lunar surface is covered with very fine dust that is easily lifted and blown away to great distances by the LM descent engines below about 100 feet. But that dust layer is very thin, and below it the regolith rapidly gets harder and denser. That's why you don't see (and shouldn't expect to see) a deep crater in the ground under a landed LM. Instead you see a "scouring" effect over a fairly wide area. It's especially visible in the pictures returned by Apollo 11 since the Eagle's descent engine operated all the way to the ground.
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Post by ka9q on Jan 28, 2012 13:42:06 GMT -4
Note ->ka9q (post #364) "In a vacuum, a rocket plume expands so quickly..." ... how quickly does it expand? Watch any rocket launch: Shuttle, Delta, Atlas, Falcon, Ariane, whatever, preferably one with solid rocket boosters producing a very visible plume. The first stage typically operates from sea level to almost a pure vacuum, and you can see the plume steadily broaden as it climbs. Some of the gases even begin to wrap around the base of the launcher. Depending on the camera angle you may not be able to fully appreciate just how much the plume broadens. The effect is especially visible in downward-looking cameras mounted on the side of the rocket. Most recent Deltas have carried cameras, as have most recent Shuttle SRBs. The nozzle design also affects the size and shape of the plume. Upper stage rocket engines, like those on the LM, generally have longer nozzles designed to operate in a pure vacuum. First stage engine nozzles lit on the ground are smaller. They're always a compromise since they have to operate all the way from the surface to a vacuum. The Shuttle SRBs are lit on the ground so they have relatively short nozzles. The Delta II is especially interesting. In its 9-SRB version, 6 are ignited at launch and the other 3 are ignited at altitude a minute after launch. A close look at those SRBs before launch shows that the ground-lit solids have short nozzles while the air-lit solids have much longer nozzles optimized for vacuum operation. With so many SRBs it's especially easy to see the plume-broadening effect on the Delta II.
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Post by ka9q on Jan 28, 2012 12:56:06 GMT -4
Thanks. I was comparing your picture with a 18,000 pixel square image of M42 from the Hubble. The Hubble has a 2.4m aperture, an area of about 4.5 m^2. Ignoring obstructions, your 80mm scope has an aperture of .005 m^2, a ratio of 900:1. So if you exposed for 2 hours, then the HST would have needed 8 seconds to collect the same amount of light *if* the fields of view were the same, which they're not. Your picture has a wider field of view, which is another way of saying what you said, that the f-stop is important too. Also, the HST picture seemed to have a longer relative exposure.
The HST has a focal length of 57.6m, so it's f/24 as compared to your f/6.25.
CCDs really have revolutionized astronomy, haven't they?
(edited to add HST f-stop)
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Post by ka9q on Jan 28, 2012 12:43:20 GMT -4
One of the recurring arguments from conspiracy theorists is that the LM doesn't look like their idea of a spacecraft I've noticed this myself. Even most hoaxers accept that artificial satellites are real, as it's hard to explain GPS, Sirius/XM and DirecTV otherwise. So one of my responses is to show them pictures of just about any modern unmanned spacecraft being prepped for launch. They're always covered with large thermal blankets of aluminized Kapton just like the descent stage of the LM. And that does make them look pretty flimsy. Of course, this requires them to think and to draw logical inferences. Always a challenge with hoaxers.
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Post by ka9q on Jan 27, 2012 9:22:27 GMT -4
It was measurable; remember the misunderstanding on Apollo 13 that resulted in poor Fred Haise getting a urinary infection.
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Post by ka9q on Jan 27, 2012 9:19:51 GMT -4
Nice picture. What's your aperture?
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Post by ka9q on Jan 25, 2012 15:45:51 GMT -4
1:34:07 Charlie Duke: We've been to the moon nine times. I mean, why did we fake it nine times, if we faked it? This should be an effective response to those hoaxers who ask why we've never been back. We did go back; we landed another 5 times after the first, and as Duke said we actually had a total of 9 flights to the vicinity of the moon. We may have not done it since 1972, but if the implication is that we did it only once out of concern that a faked achievement would be too risky to repeat, well that's just wrong -- we did repeat it.
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Post by ka9q on Jan 23, 2012 19:18:57 GMT -4
It does in pure, high pressure oxygen. See the Apollo 13 investigation report.
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Post by ka9q on Jan 22, 2012 9:56:29 GMT -4
These tests were simply outstanding. They completely obliterate every one of the conspiracists' alternate hypotheses:
Hollow-point hunting bullet from the sole "workable" grassy knoll location: would have released all its energy quickly on hitting thin skull bone and obliterated JFK's head. Ruled out.
Oswald's metal jacketed military-style bullet from same location: would have passed through JFK's head, killing him and continued on through Jackie, killing her too. Also ruled out.
*Any* gun fired from that grassy knoll location: also ruled out from the simple fact that no nearby witness saw or heard such a nearby shot.
Metal jacketed bullet from Oswald's 6th floor TSBD window: exact same results as actual assassination.
Hard to beat that! But something tells me the conspiracy fans just won't give up.
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Post by ka9q on Jan 21, 2012 12:57:42 GMT -4
Someone who is not a scientist cries foul if anything is different. Something playdor has done on multiple occasions now. Only if the result of the experiment contradicts what they'd like to believe, as is the case here. Playdor's rejection of the melon-shooting experiments is a perfect example of the nasty streak of populist anti-intellectualism that seems all too common these days, especially in the US. His refrain is "we don't need no stinkin' science, I've got my intuition", even going so far as to suggest that when a majority of the population ("60% in 1963") believes (or is claimed to believe) something, that automatically makes it right -- even when it contradicts the results of a carefully designed and reproducible scientific experiment.
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Post by ka9q on Jan 20, 2012 14:39:06 GMT -4
I thought you were smarter than this, it means i am pointing out that youngblood lied or at best did not recall the events truthfully, specter failed to uncover the facts and the WC accepted and entered the faulty evidence as FACT. Give me a break! Witnesses are human beings. They have fuzzy memories. They're often honestly uncertain about the facts. Taking pains to say what you know, what you don't know and what you're only partly certain of is being a good witness. It's hardly "lying" and it's rude and just plain dishonest to claim that it is. Witnesses are often in conflict with each other or with physical evidence. That's why you talk to as many as you can. When conflicts happened in the JFK assassination investigation, the Commission painstakingly pointed them out. Sometimes they had to apply their own or the investigators' professional judgment to explain and resolve conflicts. They'd say why they found a certain witness credible or not credible. Qualifying phrases like "the weight of the evidence indicates" appear in the report so often that they seem like cliches. Sometimes they'd avoid a finding altogether when in my admittedly nonprofessional opinion it was obvious and well supported. If only you could come even close to this level of care! The question of exactly when Youngblood vaulted over the seat to protect LBJ is a perfect example. The Commission simply could not be sure whether it was before or after Oswald's second shot because the witnesses themselves were not sure. Youngblood said no, LBJ said yes. It's entirely possible that it happened after the second shot because many witnesses simply did not recognize Oswald's first shot (the one that missed) as such. They mistook his second shot (the one that hit both JFK and JBC) as his first. Yet this is a minor detail with simply no bearing whatsoever on the important findings that Oswald fired all the shots himself with a Carcano 6.5 mm rifle from the 6th floor corner window of the Texas School Book Depository. How can we possibly discuss the WC findings, including Oswald's guilt, if you can't recognize the fundamental limitations of each kind of evidence, especially eyewitness recollections, and make informed judgments in reconciling their inevitable conflicts? You can't demand the absence of even the tiniest discrepancy in a case this huge. That simply does not happen in the real world. You base your findings on the evidence as a whole. You issue findings that best fit it all because there are, and will never be, findings that perfectly fit it all. Jumping rapidly and randomly from one piece of evidence to another, modifying it arbitrarily to suit your purposes while insisting it's the only one that matters in the entire case (until your next one) is the mark of a crank. Impugning motives and insisting that they constitute conclusive evidence -- even when unsupported or directly contradicted by all actual evidence -- is the mark of a crank. Insisting that even the most ordinary and inconsequential discrepancies must be explained by massive yet otherwise undetectable conspiracies to alter or falsify huge amounts of evidence -- by technical means you won't even begin to describe -- is the mark of a crank. (I suspect it's also the mark of a paranoid schizophrenic, but I'm not a psychiatrist.) Dismissing your opponents as being unable to think "outside the box" or for themselves simply because they disagree with you, not for any articulable reason, is the mark of a crank. Arbitrarily rejecting even the strongest and most compelling evidence for the conclusion you personally dislike while taking even outright guesswork as gospel whenever it supports the conclusion you like is the mark of a crank. You, sir, are a crank.
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Post by ka9q on Jan 20, 2012 8:09:26 GMT -4
so let's actually discuss rationally some of the evidence together "Rationally discussing the evidence together" does not mean "let's just for the hell of it tear up and discard all the overwhelming evidence for Oswald's guilt and see what's left that still proves him guilty." Rationally discussing the evidence can include playing devil's advocate, but that means giving reasons to consider tainted each of the many core pieces of evidence you'd like to discard, including, among other things, plauslble mechanisms by which things like pictures and movie films could have been undetectably altered with the technologies and under the conditions we know have existed over the past 50 years. And "rationally discussing the evidence" also means presenting incriminating evidence for alternate perpetrators that goes well beyond wildly subjective impugned motives based solely on theoretical personal gains someone might get from the assassination regardless of cost, technical difficulty or likelihood of detection. And "rationally discussing the evidence" goes beyond treating perfectly normal human behavior under extreme circumstances (like turning or ducking when somebody starts shooting) as somehow suspicious without a damn good reason. This is a stupid game, playdor. We've seen how you do it with Apollo, and now that we see you doing it with JFK it's obvious you're not at all serious about anything but an ego trip from pretending to be smarter than everyone else in the world.
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Post by ka9q on Jan 20, 2012 7:48:35 GMT -4
Norman Mailer went to write a book about how the whole thing was a conspiracy, did the research, and realized that he no longer believed that it was a conspiracy and instead believed that Oswald acted alone. He did have preconceptions-- and decided they were wrong and that Oswald did it. He looked at the evidence, not the theories, and simply couldn't make the evidence fit what he wanted to believe. That is intellectual honesty. And he's not the only one. Dale Myers used to think the JFK assassination was a conspiracy. Then he appeared in "Beyond Conspiracy" with that amazingly elaborate 3D (actually 4D, 3 spatial dimensions over time) computer model matched to every film record he could find of the actual assassination and the events before and after. Basically, he did what playdor only claims to be doing -- cross-checking every picture against every other picture. He concluded that the "single bullet FACT" is absolutely confirmed and there's no credible alternative. Gary Mack, curator of the Sixth Floor Museum, was reportedly also a conspiracy fan. But he certainly doesn't come across that way in productions such as "Inside the Target Car". They commission a Australian company that specializes in ballistics research for the Australian military to produce realisic mock-ups of human heads and torsos. They have an expert marksman shoot them on a range with the same type of weapon, the same type of ammo, with the same relative wind and in the same spots that Oswald hit. They get the very same results -- "brain" splatter and "head" motions and "wounds" -- that Oswald did. Mack comments "Many of the people writing all these conspiracy tales just don't know very much about the subject." Amen. And then "Unsolved History", with Dave Perry, another (former?) conspiracy fan, and Gary Mack again, commission (the same?) marksman to check the claimed alternate shooting spots in Dealy Plaza. None of them work; either the shots aren't there, or they'd certainly have been noticed by multiple known witnesses, or they'd produce totally different wounds on JFK (like blowing his head completely apart) and/or even killing Jackie. They test a few of the WC scenarios that the conspiracy fans often attack, like whether Oswald could have walked down the stairs quickly enough, or whether he could get from his boarding house to the Tippit murder scene, and found that he could do both easily. Basically, every one of the more honest investigators, even those who start off suspecting a theory, move far away from it the more they learn and test it. It's been almost 50 years. This thing has been investigated and reinvestigated to death, and every single time somebody does it honestly they come to the same conclusion: Oswald did it. Alone. Robert Oswald is right; it's time to just let this one go.
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Post by ka9q on Jan 19, 2012 14:48:05 GMT -4
as citizens WE should never just take for granted the conclusions of a government controlled commission. There's a difference between healthy skepticism of the government and wild-eyed, irrational, breathless paranoia.
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