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Post by echnaton on Oct 26, 2010 9:18:16 GMT -4
I said "aeronautician because I'm french, not because I don't have competences in aeronics. Come on guys, let's focus on his hoax claims, not his misuse of English. Being a hoax advocate already put him at a disadvantage he can never over come. If he claims to be an engineer, let's question his claims based on that. After all we are here to document and rebut hoax claims and we can't do that without hoax believers.
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Post by AtomicDog on Oct 26, 2010 9:26:24 GMT -4
Man, oh man... that's probably the funniest thing I've read in a while. Thanks very much for the good laugh this morning. If you really were an "aeronautical engineer", you would have called yourself an "aeronautical engineer" and not made up the word "aeronautician". Epic fail... Next time at least have the brains to use a spell check. Cz I said "aeronautician because I'm french, not because I don't have competences in aeronics. Really? I've looked up the words "aeronautician" and "aeronics" in French dictionaries and get nothing. Om the other hand, "aeronautics" translates to "aéronautique" in French. You're full of it.
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Post by inquisitivemind on Oct 26, 2010 9:48:46 GMT -4
No, it doesn't require a constant adjustment, this adjustment is automatic. Take an object, tie it to a string and make it turn: Its orientation will automatically follow the rotation. Remind: The CMS was an altitude which was low enough to need a centrigugal force to counter the lunar attraction.
I have heard of pitchover, but making a slow rotation is easier to control than a fast rotation, especially considering that the lem must control both the horizontal and vertical deceleration, and for doing that a slow rotation along the parabolic trajectory is what is best. If the LEM was not controlling the attitude during the trajectory, it could not distribute the thrust on the horizontal axes and vertical axes to control the horizontal and vertical decelerations. Controlling the LEM is more difficult than controlling a plane: The Lem only had the vertical lateral reactors to control it. Descending vertically would be very bad, because the LEM would arrive with a high horizontal velocity near the moon, and would burn much fuel to counter the centigugal force it has because of its horizontal velocity.
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Post by inquisitivemind on Oct 26, 2010 9:49:51 GMT -4
I said "aeronautician because I'm french, not because I don't have competences in aeronics. Really? I've looked up the words "aeronautician" and "aeronics" in French dictionaries and get nothing. Om the other hand, "aeronautics" translates to "aéronautique" in French. You're full of it. In french, we say "aéronauticien".
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Post by inquisitivemind on Oct 26, 2010 9:57:47 GMT -4
I have made an animation with consecutive photos in Apollo 15: Could you explain me why the LEM is flying over the LCM? It has nothing to do over the LCM, it should be between the LCM and the moon. Explain me also why the LCM is making these incohrent rotations relatively to the moon. I have also made this animation with consecutive photos in Apollo 14: Could you explain me why the LEM is going to outer space instead of going to the moon (we see only back behind it), and why it is making these brutal rotations which are totally useless and have no other purpose than uselessly burning fuel?
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Post by JayUtah on Oct 26, 2010 10:07:50 GMT -4
Could you explain me why the LEM is flying over the LCM?Because the descent orbit and rendezvous orbit are so arranged. The CSM and LM alternatively fly above each other. It has nothing to do over the LCM, it should be between the LCM and the moon.No, your expectation is wrong. Explain me also why the LCM is making these incohrent rotations relatively to the moon.It isn't rotating; it's maintaining the same orientation in space throughout the orbit. Could you explain me why the LEM is going to outer space instead of going to the moonWhy do you assume the LM is "going" in the direction in which it's pointing at any given moment? why it is making these brutal rotations which are totally useless and have no other purpose than uselessly burning fuel?
To start or stop a rotation burns fuel. To continue in a rotation does not. The purpose is to allow the CSM to inspect the LM for visual damage. Not sure why you characterize the rotations as "brutal" other than to exaggerate.
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Post by JayUtah on Oct 26, 2010 10:13:18 GMT -4
I'm an aeronautician engineer, and I perfectly know how the LCM and the LEM must behave.You clearly are not an aeronautical engineer. The questions I just answered show a substantial ignorance of spacecraft flight dynamics. it is always parallel to the moon surface, and has no reason to get oerpendicular to it.Very false. An orbiting object maintains the same space-fixed orientation. You see, I know a bit on the subject.No, you appear to know very little.
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Post by Jason Thompson on Oct 26, 2010 10:26:14 GMT -4
No, it doesn't require a constant adjustment, this adjustment is automatic. Take an object, tie it to a string and make it turn: Its orientation will automatically follow the rotation. Because the string is pulling preferentially on the side it is attached to. The gravitational force which keeps the CSM in orbit is acting on the centre of mass, with no physical attachment points. Nothing will cause the CSM to rotate as it orbits the Moon. Any orbit requires something to counter the gravitational attraction or else it does not orbit but crash. That something is the momentum of the object caused by its speed. I'd say it was easier, since there are no aerodynamic forces to contend with. The LM had a set of thruisters called the reaction control system that operated in all three axes. It could pitch, yaw and roll in any direction by using these in a controlled manner. Why would a 90 degree pitch be so complicated? The LM carries a fixed gyroscopic navigation platform that tells it at any given instant which way it is pointed. Most of the calculations required for man oeuvring are done on the ground, so the computer does not need to do much. It has a preset sequence of commands. A 90 degree pitch requires buring a particular set of thrusters to begin the pitch, and another burn of another set to stop the pitch. It also will be preprogrammed to a large degree to know how long that manoeuvre will take, so it doesn't have to sit watching the platform to say 'oh, I've done it, I need to stop now'. It already knows that a particular set of commands will result in a 90 degree pitch. The first step is the big one, where it does a coarse manoeuvre. The rest are trims to correct slight errors. And it has a limit to its precision. It had a pretty damn good computer. It certainly did not take on the order of seconds to complete simple calculations of the kind involving comaprison of where it thought it should be with where it was.
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Post by Jason Thompson on Oct 26, 2010 10:30:57 GMT -4
Could you explain me why the LEM is flying over the LCM? It has nothing to do over the LCM, it should be between the LCM and the moon. Only due to your oversimplified expectation that because it is going to be descending it must only ever be below the CSM. One thing the crews might have done when they separated was take the opportunity they had not had until that point to perform a visual inspection of each other. Why do you assume it is not going to the Moon, when the Moon is nowhere to be seen in those images? Do you assume the Moon is at the bottom because the LM should be descending? If I was taking out a spacecraft that had not been flown until that point, one thing I might do is test the RCS system and make sure it worked to move the LM as it should. I wouldn't call that a waste. I'm not saying thse things are the explanation, I'm simply pointing out some rather obvious possibilities that you seem unable to think of.
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Post by inquisitivemind on Oct 26, 2010 10:34:16 GMT -4
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Post by Jason Thompson on Oct 26, 2010 10:35:25 GMT -4
And just in case anyone missed it, this might be about as close as we get to an admission of error, hidden away in the middle of a post and immediately followed by something else that 'doesn't make sense'... OK, with your photo, I understand much better; You should have told me around which axis you were making your rotation, I would have understood faster. Now, what you have shown makes sense. OK, what you show is a possibility...but (emphasis mine)
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Post by Jason Thompson on Oct 26, 2010 10:38:07 GMT -4
But why would it be pointing toward outer space, it's not logical at all, it makes a great useless complication of its trajectory. Its trajectory is not affected by the way it is pointing unless it happens to be firing its engine at the time. A question for you: which way do you think the CSM was pointing when it first entered lunar orbit? Read again: the purpose was to perform a visual inspection of the craft, and that requires that it rotates so you can inspect it all. They do help, as they verify the condition of the spacecraft, something that the astronauts cannot do until they are separated. Oh, I love the assurance that Jay of all people is full of misconceptions about space flight. Haha! Do you have any idea who some of the people here are and what they do?
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Post by JayUtah on Oct 26, 2010 10:42:13 GMT -4
No, it doesn't require a constant adjustment, this adjustment is automatic.No it is not. Take an object, tie it to a string and make it turn: Its orientation will automatically follow the rotation.And if an object twirled on a string were just like an orbit in every respect, that would mean something. An object maintains a space-fixed orientation while in orbit. Remind: The CMS was an altitude which was low enough to need a centrigugal force to counter the lunar attraction.No, lunar orbit tides are a third-order force in CSM dynamics. I have heard of pitchover, but making a slow rotation is easier to control than a fast rotationFirst, there is no requirement that pitchover be a "fast" rotation. Second, pitchover as P64 initiates is not a 90-degree pitch. It's about 30 degrees. Third, the easiest rotation to control is that which is built into the DAP as the nominal gross rotation speed. Fourth, overshoot in a control system is no big deal. ...for doing that a slow rotation along the parabolic trajectory is what is best.And that is essentially what was done. However it was done by discrete steps, each employing a different underlying physical model that minimized the guidance computations at that phase of flight. Controlling the LEM is more difficult than controlling a plane:No. An airplane has a similar three-axis control problem, but also has to do with imposed error in the form of aerodynamic instability, not just induced error. You are right, it's mpre complicated than one migh think, and that's why you are oversimplifying it.No. You're not fooling anyone into believing you are an aeronautical engineer. I am, and my company makes flight-control software, among other things. But it can't do it precisely if the rotation is too fast, and it had a very slow computer.Please show your computations here that support your claim.
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Post by JayUtah on Oct 26, 2010 10:46:52 GMT -4
My expectation is right, it's your conception which is wrong.Please cite the references you're using for the descent orbit. We can see that it is not the case, its behavior is erratic.It appears "erratic" because it's being photographed from the LM that is moving relative to it. But why would it be pointing toward outer space, it's not logical at all, it makes a great useless complication of its trajectory.It's in a simple orbit at this point. It is not maneuvering. Right, but it didn't have to start these rotations, they don't help to the flight.They help the CSM pilot see all sides of the LM. I can assure you taht you are full of misconceptions about space flight.That's a pretty strong assertion, considering that it's what I do for a living. You're simply making naive assumptions and assertions that a layman would make.
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Post by inquisitivemind on Oct 26, 2010 11:01:16 GMT -4
Even if there was no physical string the LCM was attached to, the lunar attractions plays the function of this string. Normally, the satellites are far enough from the planet (earth or moon) so that it can turn the same as this planet (be stationary), and the created centifugal force is enough to counter the attraction from the planet. the LCM had got closer for the LEM not to have a too long journey to do; that was forcing the LCM to have a hortizontal velocity relatively to the moon, that the LEM had to null when it was leaving the LCM before reaching the moon; that's why it was starting horizontal to start decreasing this speed and thus the centifugal force. No, it's not easier, because these aerodynamic forces help to control the plane; the plane has several parameters it can play with. The lem only had the vertical lateral reactors; once it was giving a push on a vertical reactor, it was starting to turn, and it had to give an opposite push to counter the rotation and stop it; it was not so easy, and was requiring a constant control. Only the vertical reactors were used to control the attitude. The horizontal reactors were only used to move the LEM horizontally; it was practical when the LEM had to look for an area to land on the moon. The horizontal reactors were also necessary on the return to control the altitude of the lem while it was trying to join the LCM so it would remain on the same orbit as the LCM. [/quote] Why would a 90 degree pitch be so complicated? The LM carries a fixed gyroscopic navigation platform that tells it at any given instant which way it is pointed. Most of the calculations required for man oeuvring are done on the ground, so the computer does not need to do much. It has a preset sequence of commands. A 90 degree pitch requires buring a particular set of thrusters to begin the pitch, and another burn of another set to stop the pitch. It also will be preprogrammed to a large degree to know how long that manoeuvre will take, so it doesn't have to sit watching the platform to say 'oh, I've done it, I need to stop now'. It already knows that a particular set of commands will result in a 90 degree pitch. [/quote] On a plane, you can program an angle of rotation. But what happens when you do that: The computer records the order from the pilot, sends a command to start the maneuver, reads the result on a sensor, computes a new command from this reading and so on till the requited rotation is obtained. With a computational period of 2 seconds, the LEM had better not make too brutal rotations. It could still rotate at a reasonable rate. But making a series of rotations all along the journey to the moon would have made no sense, because it would have much complicated the computation of the trajectory; the way the trajectory was (relatively easiest) to compute, was to make this slow rotation from horizontal to vertical all along the journey. Besides that's even what they describe in the "TALES FROM THE LUNAR MODULE GUIDANCE COMPUTER":
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