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Post by LunarOrbit on May 30, 2005 16:26:43 GMT -4
There shouldn't be any stars in the pictures. The cameras were setup to photograph the bright objects in the foreground (the lunar surface, the LM, the astronauts, etc.), not faint stars in the sky. You can't photograph both at the same time. The hills/mountains in the background are far away, if that's what you mean. Take a look at this panoramic image from Apollo 17 to get a better idea of the scale of things. If that was filmed on Earth then it must be one helluva big sound stage.
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Post by unknown on May 30, 2005 16:29:33 GMT -4
Unknown: please stick to one subject at a time. We are discussing Apollo not the Mars rovers. So, if I understand you correctly, you're saying that the reason the Apollo LM wouldn't work is because the rocket engine is on the bottom instead of the top of the vehicle. Is that what you mean? If that is really what you mean then that's your problem right there... you simply don't understand how rockets work. To put it as simply as possible, rockets create thrust that pushes the spacecraft in the opposite direction. If you throttle back the engines to just the right amount the thrust and the mass of the vehicle balance perfectly and you are able to hover. It's not that complicated. It's terribly complicated to hover a heavy piece of metal with the rocket engine on the bottom because it becomes frightfully instable and is inclined to fall off on all sides and you are not able to react in time to keep it vertical, like a coke bottle on your forefinger.
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Post by unknown on May 30, 2005 16:31:19 GMT -4
There shouldn't be any stars in the pictures. The cameras were setup to photograph the bright objects in the foreground (the lunar surface, the LM, the astronauts, etc.), not faint stars in the sky. You can't photograph both at the same time. The hills/mountains in the background are far away, if that's what you mean. Take a look at this panoramic image from Apollo 17 to get a better idea of the scale of things. If that was filmed on Earth then it must be one helluva big sound stage. But, don't you see it is a model made with plastics?
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Post by LunarOrbit on May 30, 2005 16:46:17 GMT -4
That is a problem that Robert Goddard solved decades before NASA was even formed. All rockets (not just the Apollo LM) use gyroscopic devices called inertial sensors to detect imbalances. If the vehicle shifts to one side it automatically compensates, the pilot doesn't have to do anything. It's a mechanical system so no computing power is necessary.
Inertial sensors were also used by the German V2 rockets to guide them to their targets... before computers.
Many RC planes now also have gyroscopic sensors to help the pilot maintain level flight.
Like I said, you just don't understand how rockets work... the fact that you can't conceive of how the LM could remain balanced doesn't mean it's impossible.
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Post by LunarOrbit on May 30, 2005 16:48:42 GMT -4
So you believe it was all done using miniature models? Go watch some of the Apollo film footage and explain to me how they incorporated the real (moving) astronauts with tiny little miniatures.
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Post by unknown on May 30, 2005 16:51:17 GMT -4
"The cameras were setup to photograph the bright objects in the foreground (the lunar surface, the LM, the astronauts, etc.), not faint stars in the sky. You can't photograph both at the same time".
The true reason is that it would have been very difficult (and impossible) to simulate star lights.
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Post by LunarOrbit on May 30, 2005 16:54:21 GMT -4
Have you ever been outside at night before? Try looking at the stars while standing beneath a street light. Let me know if you can see them.
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Post by unknown on May 30, 2005 17:07:17 GMT -4
"That is a problem that Robert Goddard solved decades before NASA was even formed. All rockets (not just the Apollo LM) use gyroscopic devices called inertial sensors to detect imbalances. If the vehicle shifts to one side it automatically compensates, the pilot doesn't have to do anything. It's a mechanical system so no computing power is necessary.
Inertial sensors were also used by the German V2 rockets to guide them to their targets... before computers".
There was no mechanical system, no gyroscope that could keep fixed in hovering a rocket (and perhaps not even today). Imagine: you are close to the ground inside your rocket and you must hold it fixed 10 feet above the ground while it whiffs, snorts and wants to roll, but for you it's child's play. With compliments.
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Post by JayUtah on May 30, 2005 17:09:55 GMT -4
On the moon there is no air. They could see many more stars than on the earth.
No. Atmosphere absorbs only about 5% of the visible spectrum. Stars are not significantly brighter in space than from Earth's surface.
NO STAR, INCREDIBLE.
Not to photographers. It's only "incredible" to people who don't know how cameras and film work. Stars are too dim to be photographed at the same time as objects lit by the sun.
[b[AND, SORRY, BUT THE BACKGROUND IS TOO SMALL TO BE REAL[/b]
Huh?
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Post by unknown on May 30, 2005 17:13:49 GMT -4
Have you ever been outside at night before? Try looking at the stars while standing beneath a street light. Let me know if you can see them. Hey, do you see street lights in this picture?
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Post by JayUtah on May 30, 2005 17:14:56 GMT -4
There was no mechanical system, no gyroscope that could keep fixed in hovering a rocket (and perhaps not even today).
It's the same problem. Hovering is no different than ascending or descending. The goal in all cases is to attenuate roll and and pitch excursions. If you understood inertial reference (which obviously you don't) then you would see why you haven't postulated a different situation than has already been discussed. Guidance is guidance, regardless of the direction one is moving.
Further, I already mentioned that the key factor the LM added to this equation was the variable-thrust rocket motor. That's the only thing that makes the LM any different from a German V-2.
Imagine: you are close to the ground inside your rocket and you must hold it fixed 10 feet above the ground while it whiffs, snorts and wants to roll, but for you it's child's play.
That's where your knowledge of physics falls short. Because it's the same inertial frame, it doesn't matter whether the rocket is ascending, descending, or hovering. Attitudinal stability is exactly the same problem in each of these cases, and is solved by exactly the same techniques.
It is not our argument that hovering a lunar module is "child's play". It is merely our argument that it is not impossible. You are the one trying to tell us it is impossible. The opposite of "impossible" is not "easy".
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Post by JayUtah on May 30, 2005 17:21:34 GMT -4
It's terribly complicated to hover a heavy piece of metal with the rocket engine on the bottom...
No. That is the layman's understanding of rocketry and it's as wrong as it can possibly be.
...because it becomes frightfully instable and is inclined to fall off on all sides...
No. The rocket does not "sit on top" of the thrust. The thrust and the rocket are in the same inertial reference frame. Off-axis thrust causes a roll or pitch excursion which must be corrected by inducing an opposite rate.
...and you are not able to react in time to keep it vertical, like a coke bottle on your forefinger.
Irrelevant. As I explained, while it may be impossible to balance a bottle on your finger for any length of time, that doesn't mean it's impossible to balance all shapes on your finger. I explained why the geometry of the object matters, but you have ignored the explanation.
Further, a large object has more moment of inertia and therefore slower attitude error rates. Those fall within the human response time.
And finally, you have again completely ignored the issue of acquired expertise and training. One can be trained to do things that are initially difficult or seemingly impossible.
You're simply regurgitating your previous argument that has already been refuted. Please think before you post.
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Post by unknown on May 30, 2005 17:21:51 GMT -4
See you again soon
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Post by JayUtah on May 30, 2005 17:23:02 GMT -4
The true reason is that it would have been very difficult (and impossible) to simulate star lights.
No, the true reason is that this is how cameras and film work, and any qualified photographer can explain this to you.
Planetariums simulate star lights accurately every day. That is not at all difficult.
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Post by JayUtah on May 30, 2005 17:24:47 GMT -4
But, don't you see it is a model made with plastics?
No, I don't. Please show me your evidence that it is a photo of a plastic model and not an actual spacecraft.
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