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Post by Moon Man on Nov 15, 2005 19:27:45 GMT -4
You guys know your stuff. I don't know zippo about space. You don't have to answer this if you don't want to but I'm wondering what you peeps do for a living..? Are you working in air or space industry..?
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Post by scooter on Nov 15, 2005 19:28:23 GMT -4
Hbers cry about the shadows on the moon going this way and that way. My thoughts on the shadows were they shouldn't even exist at all, or at least during the summer moon missions, which is why I was asking. Therefore, since we agree that a shadow on earth would be very short, if at all, in the summer, and since we agree that the sun on the moon and earth shine equally as bright, for the most part, then why are there major shadows on the moon during the summer missions..? I edited and added to this message after you guys had already quoted and provided a response. Can anyone answer it please..? The question being...whose summer? As we in the northern hemisphere bask in summer's high and hot (atmospheric temp) sun angle, those in South America and Austraila are in the dead of winter with low sun angles. When we went to the Moon, we went to basically near equator sites. The sun angle wasn't terribly significant whether we went in July or January. The significant (solar heating.shadow speaking) was that we went near lunar sunrise. Now remember, it takes about 28 days to go from sunrise to sunrise at any spot on the Moon, or around 14 days from sunrise to sunset. Therefore, If we landed early in the "morning" on the Moon, when the surface was still cool (cold) from the 14 day "night", and stayed for a few Earth days, the sun would not be much higher in the sky, basically 3/14ths further alond toward sunset on the Moon. So the SURFACE temperature there,due to solar radiation (sunlight) heating would not be terrible greater when we got there 3 days earlier. There would be no great temperatuer swings. Just a slow gentle bit of a rise. Now, when they go back, and stay for much longer (earth months?)....that will be a challenge to deal with. Dave (edit for technical correction)
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Post by scooter on Nov 15, 2005 19:33:31 GMT -4
Currently a school bus driver, having a ball! USAF retired, have a couple of space science courses under my belt (masters level). Mainly, just really get a kick out of space travel and flight. It's an awsome undertaking, whoever does it. Good to see you asking questions here Moon Man, I'm enjoying, and appreciating, your candor. And I'm learning from the guys here too, just like you...
dave
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JMV
Venus
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Post by JMV on Nov 15, 2005 19:44:17 GMT -4
Okay, thanks for the answers to the atmosphere question. Where is the ozone layer located..? Right outside our atmosphere or further out..? If it is further out is it beyond the height of the space station..? If it is below the space station our we not creating holes in it by flying through it over and over again..? even if we're only penetrating it for a few seconds each time given the speed the shuttle is doing..? Also, the ozone layer protects us from harmful rays from the sun, so what protects the spacestation and the astronauts (yeah I know they are inside it and not outside) if there is no ozone layer inbetween the earth and the moon..? Somewhere between 20 and 50 kilometers I believe, in stratosphere anyways. We're not creating holes in it by flying through it, though I'm not sure what kind of chemical effects some of the rocket exhaust gases have on the ozone layer. Ozone layer protects us from sun's UV radiation and we know how poorly UV rays penetrate anything. There really isn't any need for astronauts on the moon to have ozone layer. Their spacesuits block all of the UV rays totally.
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Post by nomuse on Nov 15, 2005 19:48:19 GMT -4
There's a thread on this board, Moon Man, in which we give our experience. I'd say, off hand, a few dozen of us are professionals in the field (satellite wranglers et al). The majority are amatuer enthusiasts.
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Post by Moon Man on Nov 15, 2005 20:03:46 GMT -4
Cool, and thanks for the answers once again. I've learned alot from all of you and I hope to learn more. I'm going to check out the debate thread for 5 minutes and them I'm out for the evening. But I'll be back!
Enjoy your evening!
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Post by scooter on Nov 15, 2005 20:28:31 GMT -4
going back to water freezing in space...
Some years back, during the "routine" days of shuttle flights, there was an episode where the wastewater discharge outlet heater acted up and a large chunk of ice formed on the outlet outside the shuttle. They studied it, pondered it, tried turning that side to the sun for some periods, etc. It actually got new coverage! Finally, thay got creative and knocked the silly thing off with the robot arm IIRC. I would suppose that with enough direct sun exposure it would have sublimated (solid to gas, like the snow/ice on my driveway does in the freezing cold, tho sunny days), but the intermittent night "interfered" every 45 minutes. Is this a fair interpertatation? Would such a situation been easier fixed on a trans lunar (potential full sunlight) trip? Boiling...freezing...I can see some confusion using earth atmosphere paradigms.
Dave
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Nov 15, 2005 22:10:31 GMT -4
You guys know your stuff. I don't know zippo about space. You don't have to answer this if you don't want to but I'm wondering what you peeps do for a living..? Are you working in air or space industry..? This thread gives the background of many of us.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Nov 15, 2005 22:23:40 GMT -4
These tables may help with the atmosphere question. As you can see, the Earth's atmosphere extends thousands of kilometers into space, however it becomes extremely thin. The International Space Station orbits at about 400 km at which the air is only 1/468,000,000,000 as thick as at sea level. Even at this low density the atmosphere stills causes the ISS orbit to slowly decay, requiring occasional propulsive boosts to keep it in orbit.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Nov 15, 2005 22:55:01 GMT -4
We're not creating holes in it by flying through it, though I'm not sure what kind of chemical effects some of the rocket exhaust gases have on the ozone layer. Solid rocket propellants use ammonium perchlorate as the oxidizer, thus the rocket exhaust includes chlorine-containing molecules. Chlorine is a catalyst in ozone destruction. I don't know if the exhaust products pose a threat to ozone layer of not. I guess it depends on whether or not the chlorine containing compounds are stable and benign. I imagine at least some of the chlorine is released into the atmosphere as free chlorine atoms. Does anyone know any more about this? Regarding the height of the ozone layer, I know it is in the stratosphere but I don't know where it is most greatly concentrated. The stratosphere extends from about 10 to 50 kilometers.
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Post by Jason Thompson on Nov 16, 2005 4:26:37 GMT -4
Hbers cry about the shadows on the moon going this way and that way. My thoughts on the shadows were they shouldn't even exist at all, or at least during the summer moon missions, which is why I was asking. Therefore, since we agree that a shadow on earth would be very short, if at all, in the summer, and since we agree that the sun on the moon and earth shine equally as bright, for the most part, then why are there major shadows on the moon during the summer missions..?
The length of shadows is determined by the angle the sun makes with the horizon. If you go out early on a summer morning (just after sunrise) you will cast a long shadow. As the sun moves higher in the sky your shadow will shorten. You can try this yourself. Get a long tall object like a bottle, a candlestick or somesuch and use a torch to illuminate it at different angles to see how the shadow behaves.
During all the Apollo missions the sun was low in the sky because they were timed to arrive during the lunar morning. With the sun so low it cast long shadows. Even the longer missions only went from early lunar morning to late lunar morning. In terms of the sun's movement across the sky this is the equivalent of a couple of hours on Earth. However, it is long enough for the shadows to change noticeably, and the TV footage shows the changing shadows as the EVAs progress.
Where is the ozone layer located..? Right outside our atmosphere or further out..? If it is further out is it beyond the height of the space station..?
If it is below the space station our we not creating holes in it by flying through it over and over again..? even if we're only penetrating it for a few seconds each time given the speed the shuttle is doing..?
For the same reason you don't leave holes in your bathwater when you run a hand through it. The atmosphere, including the ozone layer, is fluid and will easily fill the small hole left by a passing object.
Also, the ozone layer protects us from harmful rays from the sun, so what protects the spacestation and the astronauts (yeah I know they are inside it and not outside) if there is no ozone layer inbetween the earth and the moon..?
Well, you just answered your own question. They're inside. Even when they venture outside they are encased in a spacesuit designed to reflect and/or absorb the UV rays.
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Post by Jason Thompson on Nov 16, 2005 4:28:58 GMT -4
As to what I do, I am a biochemist. I took A-levels in the sciences at college and a degree in biochemistry at university. I have been a space buff for several years. There is some degree of irony in the fact that it was the Moon hoax theory that really got me more heavily interested in space and space travel.
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Post by gregtj on Nov 16, 2005 6:23:43 GMT -4
Good morning. As far as MM's trouble getting a handle on the fact that there is no temperature in a vacuum, I would like to offer an analogy that may help. I should make clear though, that I have trouble spelling thermodynamics let alone properly understanding it. Fact is Im learning disabled and follow the space program and astronomy because I love the subjects even if I cant get deep into it. So I would appreciate more knowledgable folks here giving me the thumbs up or down on this idea. I will edit or delete as appropriate. I, frankly, initially balked at the idea of no temp in vacuum when I first heard of it. I like to try and visualize things to better understand, so this is what I thought of: MM- Imagine you are in an EVA suit doing a space walk in high orbit. You have two old mercury thermometers. Hold one thermometer so that only the top is directly facing the sun. Turn the other one sideways with respect to the sun so that the entire side is exposed. They are right beside each other, but will show different temps because one is receiving more sunlight/energy. They are showing temperatures, but it is thier own temperature based on exposure to the sunlight, as opposed to the (non-existing) temp of the vacuum environment. As a contrast, if you put a thermometer in a pot of boiling water on earth, it won't matter which way you turn it, it will show 100 deg. C, because it IS measuring it's direct environment. Does that make sense?
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Post by laguna on Nov 16, 2005 6:44:05 GMT -4
To me it does. But does it to MM?
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Post by gwiz on Nov 16, 2005 6:56:49 GMT -4
To me it does. But does it to MM? It didn't have any effect the last time we tried that argument, he just ignored it and kept on pushing the same old line.
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