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Post by gillianren on Nov 14, 2011 1:34:56 GMT -4
if you can give me the science Can you show that you are able to understand it? Don't get me wrong-- I don't understand a lot of it. But I know that people who do understand it don't question the reality of the Apollo record. This tops any feelings I have or don't have about it, because I am not qualified to gainsay them.
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Post by Jason Thompson on Nov 14, 2011 2:44:10 GMT -4
To imply these issues influenced Armstrong's answer belittles Armstrong and his crew. How so? You have yet to show that there was ever any intent to look at the stars with anything other than the optics in the spacecraft. He did not say that they did either. That is your assumption that they would have spent a significant amount of time looking to see if stars were visible. The answers you have been given here are an attempt to explain why that is unlikely, especially on that particular mission. We can be reasonably sure that he meant that they did not see stars, and that is all. It is YOU who are assuming additional meaning. It is YOU who are assuming the crew would have been devoting time to trying to see stars, as if they could have anticipated being questioned about it later. It is YOU who will not accept that there are many reason why they were unlikely to have seen stars without especially looking for them. You have been given the science. You simply will not accept it because it is not the science you want to hear.
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Post by dwight on Nov 14, 2011 3:57:44 GMT -4
Why would you want to look at stars that would appear no different (ie configuration-wise) than if you looked at them on earth? What is the actual benefit?
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raven
Jupiter
That ain't Earth, kiddies.
Posts: 509
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Post by raven on Nov 14, 2011 4:07:57 GMT -4
Not to mention that Collins, Armstrong and Aldrin were all Gemini veterans. If stars were visible in space under the conditions playdor assumes, they would have been able to make an accurate lie from their personal experiences alone. So, if they should have been, why not mention them?
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Post by Jason Thompson on Nov 14, 2011 4:14:30 GMT -4
And by the way, playdor, your failure to acknowledge that you were provided with the reference to the LM engines using the same propellants exactly as you requested has not gone unnoticed. Nor has your inability or refusal to point out exactly where in Moon Machines they said the APS and DPS engines used different propellants.
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Post by ka9q on Nov 14, 2011 7:28:01 GMT -4
in watching it Armstrong stated, from cislunar space they could only see the blackness of space, the earth, sun and moon, and other crews may have reported some planets. I asked the question here what Armstrong meant Why are you asking us? Armstrong spoke American English. Since you're speaking English with us and you even retyped his words, you obviously understood the specific words he used. Other than cislunar, which we defined for you, the rest are all common everyday words. Surely you don't need our help in understanding them? Or are you hoping for several slightly different interpretations from the people here so you can manufacture some sort of controversy where none exists?
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Post by ka9q on Nov 14, 2011 7:55:47 GMT -4
Don't get me wrong-- I don't understand a lot of it. But I know that people who do understand it don't question the reality of the Apollo record. This tops any feelings I have or don't have about it, because I am not qualified to gainsay them. I think you're selling yourself short. Even if you understand none of the technical aspects of Apollo, and I rather doubt that, you'd hear and see inconsistencies and problems discussed openly and repeatedly by those whom you do regard as experts. If there were any, you'd know it. I think about this problem a lot because the world is far too complex for anybody to be an expert in everything. I might personally know enough about Apollo and how it actually worked to conclude on my own that it was real, but that's not true for nearly every other field because I lack the expertise. Global warming, for example. I know the most basic principles of a planetary radiation balance but I am by no means qualified to understand the subtleties of the various models and their application to our own planet. I have to rely on others who are experts -- but I still don't blindly believe whatever they say. I can see if the experts seem to be following the scientific method. Do they collect and share data and models? Do they peer review each others' work? Do they openly publish and discuss their work at conferences and in publications? Are their theories modified or discarded when the evidence seems to call for it? Do they seem to give a fair hearing to dissenting minorities? And so on. Even if I don't have the personal expertise to contribute to a given field, I can at least look to see if the proper processes are being followed by those who do claim that expertise.
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Post by gwiz on Nov 14, 2011 7:55:56 GMT -4
Can you cite your references? NACA TN 1592 These tables are for air, which is why Bob, using the actual value of gamma for the exhaust, got a different answer. The equations are in the reference and also on Bob's page. Certainly a valid topic. The efficiency of a rocket is a combination of a number of factors such as how thoroughly the propellants react, how the exhaust velocity compares with the vehicle velocity and how the pressure at the nozzle exit compares with the external air pressure, which means it can vary enormously. In general, the nozzle itself is usually not a great source of losses.
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Post by ka9q on Nov 14, 2011 8:06:07 GMT -4
Thanks much, I have some reading to do.
Regarding efficiency, I wouldn't expect the nozzle itself to introduce many losses. I'm thinking of losses that are inherent in that nozzle not being infinitely long. When the exhaust comes out, it still has some heat energy that wasn't converted to linear motion. Just like the rejected heat from any other heat engine, that's lost energy.
I'm wondering how these efficiency figures compare to rockets that aren't heat engines, such as ion thrusters and electromagnetic accelerators, which I see as analogues to electric motors.
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Post by chrlz on Nov 14, 2011 8:44:45 GMT -4
This may be out of line (but.. too bad!). Before responding further, I would most respectfully suggest that readers take a look at a certain poster's first few .. er .. contributions. I quoth, emphasis mine.. Very first post: Right-oh... Second post(sound familiar, at all?) Third postEr, right.. 'anyone' who 'does not know anything about ..apollo'? Oh, wait.. Yes, took him just 3 days to learn how to 'analyse' ascent and descent sequences, and just 3 posts to start attacking the 'debunkers'.. And then just two hours later, he is 'analysing' (term used *VERY* loosely!) apollo mpg files, and confidently reposting getting it completely wrong. Oh, and a quick question for playdor.. why do you keep *changing* your spellings? My belief in you as a genuine enquirer has disipated dissapated... Seriously, folks, read all his posts. And then decide how much time you should spend 'helping' him. But he did make the following statements I don't take issue with: Indeed.
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Post by randombloke on Nov 14, 2011 8:51:40 GMT -4
playdor, a question for you, on combustion temperatures and engine exhausts:
I have a gas oven. It burns 'natural gas' which is basically methane with a couple of additives for smell. Methane has an adiabatic flame temperature of 1950 degrees Celsius. That same gas oven is primarily constructed of steel. Steel is a common structural alloy which you may have heard of. It also has a melting point, depending on exact composition, of between 1100 and 1550 degrees Celsius. I'm sure I don't have to tell you that all of the values in that range are less than 1950 degrees Celsius.
So, my question to you is, how come I can leave my oven on at maximum for hours without it melting? Or even starting to deform significantly (it is very thin steel)? Or is my oven a fake?
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Post by gwiz on Nov 14, 2011 10:14:39 GMT -4
Regarding efficiency, I wouldn't expect the nozzle itself to introduce many losses. I'm thinking of losses that are inherent in that nozzle not being infinitely long. When the exhaust comes out, it still has some heat energy that wasn't converted to linear motion. Just like the rejected heat from any other heat engine, that's lost energy. True. The drop in temperature compared with the drop to absolute zero gives an idea of how much thermal rather than kinetic energy is left in the exhaust. On the other hand, the longer the nozzle, the greater the mass of the vehicle and the lower the velocity for a given kinetic energy. There is obviously going to be an optimum nozzle length. You can still compare energy input to the motor to the energy gain of the vehicle, and once again that gives very low efficiency at low vehicle speeds (energy going into exhaust speed rather than vehicle speed) and a much better result at high speed.
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Bob B.
Bob the Excel Guru?
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Post by Bob B. on Nov 14, 2011 11:09:27 GMT -4
Not to mention that Collins, Armstrong and Aldrin were all Gemini veterans. This is a point I was about to make. For these men the "wow" factor of being in space for the first time was over. During their Apollo flight they likely weren't clinging to the windows trying to get a look outside. They had already experience being in space knew what stars, if any, they could see by looking out the window. They probably just went about their busy schedule without giving the idea of looking for stars a second thought. Let me also point out that one of the tasks performed during the Gemini EVAs was to photograph stars. Both Collins and Aldrin performed EVAs, though I don't recall specifically if star photography was part of their assigned duties (I think it was). So my point is to the HBs who argue that the Apollo astronauts should have taken advantage of their time in space to photograph stars -- it had already been done. Apollo was about landing on the Moon, so they didn't waste time performing non-pertinent tasks that had already been accomplished on previous missions.
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Post by Jason Thompson on Nov 14, 2011 11:21:41 GMT -4
For these men the "wow" factor of being in space for the first time was over. Indeed. Many HBs express incredulity that these men weren't just looking around going 'wow, isn't this great' all the time, and then completely fail to appreciate what they might find amazing and worth looking at at any given stage of the mission. We had someone here who couldn't believe they didn't all gawp at the Earth hanging in the sky over the Moon while completely failing to appreciate that something even more amazing (the untouched lunar land on which no human had ever set foot) was at their feet. Anecdotes abound regadring the flights when rookies were on the crew, with the experienced crewmen allowing them their time to appreciate the spectacle but equally keeping them on task with critical things like making sure their spacecraft worked properly so they didn't, you know, die a hideous death by accidentally venting the oxygen or smacking into the Moon! What also amazes me is that most HBs who think the astronauts should have been gawping at the stars themselves evidently spend their lives not giving the amazing spectacle of a clear night sky a second thought....
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Post by laurel on Nov 14, 2011 12:16:00 GMT -4
60 minutes said that Armstrong had historically avoided interviews, so i went to the net to see any interviews posted. the only one that came up on youtube was the 1970 BBC interview. Why not read his NASA Oral History Project interview or his interview in the ALSJ instead of limiting your research to just YouTube? Both are linked on this page. history.nasa.gov/alsj/a11/
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