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Post by jaydeehess on Aug 5, 2005 13:45:48 GMT -4
Concerning the dust kicked up by the Lunar Rover I am told:
This refers to a caption for a picture taken from behind the rover so an arc will not be seen(would have to be in profile). Also I cannot find anywhere in the book that Bennet and Percy have made this an 'official' question for NASA.
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Post by sts60 on Aug 5, 2005 14:00:52 GMT -4
Told by who...?
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Post by margamatix on Aug 5, 2005 16:16:41 GMT -4
What moon dust does depends on whom you talk to.
Gene Cernan said it was a very fine, all pervasive dust that got into the spacesuits "and all moving parts"
I don't see how any could have got into any moving part of the lunar rover if it simply flew up and back in a cock's tail trajectory.
Can I ask an unrelated question about the differences in our common tongue, raised by this?
I was always told that the word "cock", was taboo in American English, even when unrelated to its slang meaning, or used as part of a longer word. So where we say cockroach, they say roach, to quote just one example.
Is this not true? I thought "rooster" would be the word an American English speaker would use?
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Post by JayUtah on Aug 5, 2005 16:51:43 GMT -4
Gene Cernan said it was a very fine, all pervasive dust that got into the spacesuits "and all moving parts"
How much longer, and in how many irrelevant contexts, are you going to keep milking that quote?
I don't see how any could have got into any moving part of the lunar rover if it simply flew up and back in a cock's tail trajectory.
There are other ways besides the lunar rover tires in which dust can be disturbed and deposited.
I was always told that the word "cock", was taboo in American English, even when unrelated to its slang meaning, or used as part of a longer word.
As with all things linguistic, it's all about nuance.
"Cockpit" and "cockroach" are still commonly used in American English and quite appropriate for polite company, although "flight deck" and "roach" are used in formal settings like written communication. "Cockfight" is still used, although the preferred term for the male chicken is "rooster". The "shuttlecock" in badminton is better called a "birdie" in American English. We still "cock" a pistol, and to "cold-cock" someone means to hit him on the head from behind and render him unconscious.
Any time you use the syllable in America you risk a puerile response, but rarely will you be considered vulgar except by the overly politically correct.
I remember being taken to task for using the phrase "balls to the wall", which -- to the well-informed -- has nothing to do with male anatomy. The "balls" in this case refer to a standardized grip shape for an airplane's throttles in the middle 20th century. Each lever in the cockpit had a distinctly shaped grip so that it could be located by feel. Putting them "to the wall" meant pushing them as far forward as they would go toward the airplane's firewall.
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Post by margamatix on Aug 5, 2005 17:14:40 GMT -4
How much longer, and in how many irrelevant contexts, are you going to keep milking that quote? Only until monday, when I have to go back to work.
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Post by DaveC on Aug 5, 2005 17:43:26 GMT -4
What moon dust does depends on whom you talk to. What Moon dust does depends on the laws of physics. The question is whether what is observed in the lunar film and video is consistent with what one would expect based on an understanding of those laws. I suggest that it is totally consistent. Well, maybe you need to think a bit more about what the rover looked like and how it operated. It had front and rear drive wheels - the wheels were able to turn for steering. How could dust not be directed towards the rover itself at times? In Canada we speak Americanized British English, but the word "cock" is quite commonly used as part of words or expressions - cocksure, cockamamie, cock of the walk, cock fight, etc. We do call the "cock's tail" a rooster tail though. [/quote]
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Post by margamatix on Aug 5, 2005 17:52:06 GMT -4
Well, maybe you need to think a bit more about what the rover looked like and how it operated. It had front and rear drive wheels - the wheels were able to turn for steering. How could dust not be directed towards the rover itself at times? I see what you are saying, but surely, if we accept that explanation, there would have been some dust on the feet of the lunar module itself?
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Post by JayUtah on Aug 5, 2005 18:05:46 GMT -4
I see what you are saying, but surely, if we accept that explanation, there would have been some dust on the feet of the lunar module itself?
No, for the reasons already discussed.
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Post by Jason Thompson on Aug 5, 2005 18:12:26 GMT -4
I see what you are saying, but surely, if we accept that explanation, there would have been some dust on the feet of the lunar module itself?
But why?
There are three main 'objects' that might get dust on them: the LM, the rover and the astronauts themselves.
The astronauts are obviously going to get covered in dust as they walk around in it, fall over in it, kneel down to pick things up, and handle objects and rocks that are coated in it.
The rover will also get covered in dust, since the wheels will kick dust up. The front wheels in particular will throw dust under the rover and into various moving parts. If I recall correctly, one of the front mudguards (fenders to people from the US) broke on one of the rovers, and after a short drive in which the astronauts and the rover got thoroughly sprayed with the dust that was kicked up by the front wheel, they devoted a significant portion of their EVA time to rigging a makeshift mudguard for future traverses. On top of the dust from the wheels, the astronauts themselves will kick dust onto the rover, and since they are handling dusty samples over it there will also be dust from them.
The LM footpads are a different kettle of fish. None of the dust picked up by the descent engine will have ended up anywhere near them, for reasons already explained in another thread. The only way dust can get onto the LM footpads is from the astronauts kicking it over them. Indeed, they may have done so, and it is more than likely that there is a coating of dust on the footpads. All you can tell from the photos is that there is not a huge mass of dust present. But the astronauts didn't spend all that long miling around by the footpads (except the one under the ladder as the loaded samples and entered the LM), whereas the astronauts were always surrounded by dust wherever they went, and the rover did an awful lot of traversing through it.
Given that, the dust is obviously going to be all over the astronauts and the rover, but not so much on the LM.
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Post by JayUtah on Aug 5, 2005 18:17:02 GMT -4
The dust entrained in the DPS plume is moving three orders of magnitude faster than dust ejected from LRV tires, and thus possess six orders of magnitude more kinetic energy. DPS-entrained dust is moving mostly horizontally, while LRV ejecta has a classic ballstic trajectory. These are simply not comparable dynamic states.
The difference in velocity is that between a housefly and a bullet. Do houseflies and bullets behave the same in a collision?
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Post by jaydeehess on Aug 5, 2005 20:46:51 GMT -4
An HB on another forum I suppose I should thank margamatix for hijacking this thread in order to pursue a line of questioning that he already has had answered in other threads. Lord knows if maybe getting the same answer several times might cause it to sink in. Now, as I said I can find at least one thing wrong with Bennett and Percy's photo caption. The photo is taken with the right rear quarter of the rover facing the camera, thus making any rooster-tail less obvious than a profile shot. Now that I have the page (page 328, Dark Moon) in better light as well I can see that the rover is moving in a straight line, the front wheels are pointed straight ahead, and the rover has wheel fenders. With fenders the dust would be shot out from the wheels against the fenders and would exit the rear of the fender at random angles due to collisions between particles. It would not be a rooster-tail unless the rover was turning which would cause dust to be churned up in a trajectory that would exit the side of the fenders. Any comment anyone?(except margamatix)
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Post by jaydeehess on Aug 5, 2005 20:50:36 GMT -4
The photo caption reads
That last sentence refering to the section in the book in which the photo appears in which the lunar reflector is discussed.
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Post by sts60 on Aug 5, 2005 20:53:44 GMT -4
Well, I really think margamatix should be allowed to comment too. Hopefully, by now he is willing to acknowledge that different means of moving dust (engine plume, rover wheels, feet, falling in it, picking up dusty tools, etc.) and different places and times when these occur mean that a lot of dust will get on some things, and little dust will get on other things. But certainly we shouldn't expect dust to be stirred up onto the foot pads from the descent engine.
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Post by jaydeehess on Aug 5, 2005 22:26:43 GMT -4
I know that margamatix is interested in dust and it's behaviour. I am too. I am particularily interested in the dust thrown by the rover at the present time. He has posted concerning several other methods by which dust can be caused to move. If he wishes to comment on the rover's dust I would be interested. Almost as interested as I would be in your or Jay's comments on it. ;D
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Al Johnston
"Cheer up!" they said, "It could be worse!" So I did, and it was.
Posts: 1,453
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Post by Al Johnston on Aug 6, 2005 2:57:02 GMT -4
Lord knows if maybe getting the same answer several times might cause it to sink in. I wouldn't bet on it: stubbornness is frequently mistaken for tenacity by the intransigent. Now, as I said I can find at least one thing wrong with Bennett and Percy's photo caption. The photo is taken with the right rear quarter of the rover facing the camera, thus making any rooster-tail less obvious than a profile shot. Now that I have the page (page 328, Dark Moon) in better light as well I can see that the rover is moving in a straight line, the front wheels are pointed straight ahead, and the rover has wheel fenders. With fenders the dust would be shot out from the wheels against the fenders and would exit the rear of the fender at random angles due to collisions between particles. It would not be a rooster-tail unless the rover was turning which would cause dust to be churned up in a trajectory that would exit the side of the fenders. Any comment anyone?(except margamatix) Weren't the fenders mounted so that they pivoted with the wheels as they steered?
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