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Post by Jason Thompson on Nov 13, 2011 6:46:05 GMT -4
Incidentally, Moon Machines is a good example of how much care needs to be taken with primary and secondary source material. It is generally excellent, but in one episode the narrator says that the SPS engine on the CSM was a liquid hydrogen/LOX engine, which it most certainly is not. Note that that was an error from the secondary source: the narration of the documentary, not the primary source (an interviewee who worked on it). An interesting object lesson.
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Post by PhantomWolf on Nov 13, 2011 7:06:39 GMT -4
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Post by trebor on Nov 13, 2011 7:17:31 GMT -4
Armstrong said the stars can't be seen from cislunar space, period Nope. They were perfectly able to see stars through the optical telescope and when in the shadow of the moon.. And this is even mentioned quite a few times in the mission transcript. so while the space craft was in cis-lunar inter-space, the port hole always faced the sun? It had several windows. If Armstrong had looked out the port hole when it was faced away from the sun, would he have seen stars or not? Not if there was sunlight brightly illuminating the CM interior from the other window, or if the internal lights were on. But when they passed into the shadow of the moon they were able to.... because it was much darker. From the Apollo 11 transcript:
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Post by abaddon on Nov 13, 2011 10:17:45 GMT -4
so while the space craft was in cis-lunar inter-space, the port hole always faced the sun? If Armstrong had looked out the port hole when it was faced away from the sun, would he have seen stars or not? The CM had 5. You knew this? Apparently not. Here you go: www.lpi.usra.edu/lunar/documents/apolloSpacecraftWindows.pdfNot to mention, the CM had lights inside.
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Post by gwiz on Nov 13, 2011 11:21:45 GMT -4
A one meter long conical descent engine skirt protruded from the bottom of the stage. Are you aware of the function of the nozzle on a rocket engine? I ask you this because you've quoted a temperature of 5000 deg F several times. That temperature is the value inside the combustion chamber. The function of the nozzle is to convert the internal energy of the gas, as indicated by high temperature and pressure, into velocity. That means that at the nozzle exit the velocity is high and the temperature and pressure are low. As others have told you, once out of the nozzle exit the exhaust expands even more so gets even cooler.
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Post by Jason Thompson on Nov 13, 2011 11:50:59 GMT -4
problem is no one is willing to venture a guess as to what the temperature might have been near the lm's component You're the one claiming it was too hot, so you're the one with the burden of prof. If you don't actually know what the situation is why are you pursuing the argument? Nor have you, and you're the one claiming the film couldn't do the job.
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Post by Jason Thompson on Nov 13, 2011 11:53:21 GMT -4
Apollo astronauts seeing stars. so the answer is yes they saw stars, but only thru the optics. Or when they were in the shadow of either the Earth or the Moon, and if they had time to find a moment when they could actually get away from brightly lit things and dark adapt.
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Post by JayUtah on Nov 13, 2011 11:56:05 GMT -4
problem is no one is willing to venture a guess as to what the temperature might have been near the lm's component Are you? You seem to think the design was inadequate. On what do you base that, other than your incredulity? The thermal design of the LM near the DPS nozzle skirt is a matter of record. Have you studied it? No, but I work in part designing spacecraft. Are you a professional conspiracy theorist?
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Post by JayUtah on Nov 13, 2011 11:57:43 GMT -4
please show me the reference that states the ascent engine used nitrogen tetroxide oxidizer? Why is this necessary? What other oxidizer would you use with methylated hydrazine in a hypergolic engine?
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Post by gwiz on Nov 13, 2011 12:15:39 GMT -4
problem is no one is willing to venture a guess as to what the temperature might have been near the lm's component? Here's a good reference for you to start on: ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720018272_1972018272.pdfYou were the one who claimed the temperature was 5000 deg F. Now you say you realise that the temperature must have been lower since the gas had expanded. I suggest it is up to you to admit your initial claim was incorrect and it is also up to you to come up with the temperature. Edit to add: No use waiting for playdor. Here's the result using my air flow tables: Nozzle expansion ratio is 43, so exit Mach number is 5.70. At this Mach no. the absolute temperature ratio is 0.133, giving the exit temperature as 266 deg F. I'm aware that the exhaust gas isn't air, but I wouldn't expect a greatly different answer for another gas.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Nov 13, 2011 12:16:04 GMT -4
Armstrong said the stars can't be seen from cislunar space, period No, he said that he couldn't see them. Big distinction.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Nov 13, 2011 13:14:22 GMT -4
problem is no one is willing to venture a guess as to what the temperature might have been near the lm's component No one needs to guess, it's not hard to figure out. Since I haven't been following this thread, I don't know what you means by "near the lm's component", but I get the impression you have some issue with gas temperature near the exit of the APS. Is that correct? The APS burned Aerozine 50 and nitrogen tetroxide at a mixture ratio of 1.60 and a chamber pressure of 120 PSI. This results in an adiabatic flame temperature of 3072 K (5070 o F). It is also important that we know the specific heat ratio γ, which in this case is 1.23. As the gas passes through the nozzle throat, it's pressure and temperature decreases. At this point the pressure is 67 PSI and temperature 2755 K. The gas continues to expand isentropically as it moves toward the nozzle exit. The APS had an expansion ratio of 45.6, so it's possible to calculate the gas pressure at the nozzle exit. In this case the exit pressure is 0.187 PSI. (Such a low pressure is normal for a high expansion ratio engine designed to operate in a vacuum.) The isentropic relationship between temperature and pressure is (T2 / T1) = (P2 / P1) (1 - 1/γ)Taking T 1 and P 1 as the temperature and pressure at the throat, we can easily calculate the temperature at any other pressure. At the nozzle exit, the temperature is 917 K (1191 o F). (edit) Please note that temperature in the above equation must be expressed in one of the absolute temperature scales, i.e. Kelvin or Rankine. Do not use oF or oC because you'll get a bogus answer. Pressure must also be absolute, i.e. not gauge pressure.
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Post by JayUtah on Nov 13, 2011 13:15:30 GMT -4
I can't begin to prove any point i am trying to make. Clearly. That's because you start with the proposition that Apollo was faked, and assume that all the sciency stuff will work itself out to support your claim that it's fake, if only to be "questionable." No, after looking at the Apollo landings it's clear there are many things that you personally don't understand about the Apollo technology in particular and about the underlying sciences in general. And that's understandable, because aerospace engineering is a demanding profession with much to learn in it. Don't be disappointed that you can't Google up the equivalent of a college degree in it. But don't make the mistake of thinking that because you personally can't figure it out, then it must be equally murky to everyone else. Think carefully about why it only seems "impossible" to people who don't have the relevant training and experience, and why everyone who is suitably educated and experienced has no problem believing that Apollo was real. No. The problem is that you're doing your best to try to stir up the appearance of inconsistenty, impropriety, and error whether the facts show it or not. You're not listening to the answers, and you're doing your best to keep from having to prove anything yourself. To the people who aren't so contentious, there are plenty of satisfactory answers. Indeed there is. It's right here where you say That's where your bias is having a huge influence over your thought process. When you are mature enough to realize that this line of reasoning does not and cannot support any particular hoax theory, or any specific accusation of fraud, then you'll understand why conspiracy theories tend to be relegated to the fringe. if you answer yes that it does, then all we have to do is negotiate as to how big a lie they would tell and could get away with it. For an instant... if they lied about the moon landings, how easy do you think it would be to prove it a lie. What makes you say the technology was unproven? Are you an expert in aerospace engineering? Nope. That's the conspiracy-theory version of the history of Apollo. In reality, NASA had to vigorously prove to the Kennedy administration that they could do it before Kennedy would agree to ask Congress fund it. The conspiracy authors never study history and so make up this story that Kennedy just up and decided to go to the Moon and NASA had a sort of "deer in the headlights" response. Exactly the opposite, in fact. Your problem is that you believe in the hoax for social and political reasons, but you're trying to argue it on technical grounds. And because you're unskilled in that area, you can't make any decent headway because there is no valid technical argument for the hoax. And you're here arguing with a bunch of technologists who, in the first place know this stuff very well, and in the second place are used to people making bad arguments and therefore all the tricks. We care about getting the technical history right. We don't care about your political beliefs. But please don't think that we argue the technical points because that's our way of opposing you politically, and that we "really" are here because we're in political opposition to you. In other words, don't make the mistake of projecting the converse of your political beliefs onto us as a motive. I'm an engineer. I dislike politics and I don't care to discuss them. But if you tell me that my industry committed wholesale fraud, then those are fighting words and you had better come prepared either to make a sound technical argument or apologize profusely and walk away.
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Post by ka9q on Nov 13, 2011 14:09:39 GMT -4
At the base of the assembly was the ascent engine. The stage also contained an aerozine 50 fuel and an oxidizer tank, and helium, liquid oxygen, gaseous oxygen, and reaction control fuel tanks. To be fair, while this says the ascent and descent engines used the same propellants, it doesn't say what the reaction control (RCS) propellants were. But the more detailed LM references explain that the ascent engine propellant supply could be crossfed with the RCS supplies. This obviously implies that the RCS engines burned the same propellants as the ascent engine. Normally this type of engine would burn MMH (monomethyl hydrazine) rather than Aerozine-50, but the RCS engines on the LM were requalified to use the latter.
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Post by Jason Thompson on Nov 13, 2011 14:09:58 GMT -4
So how does it affect your statement about the thermal protection on the LM?
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