Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Aug 23, 2008 22:38:02 GMT -4
One of my long-term projects with the Apollo Lunar Flight Journal folks is an accurate 3D model of the Apollo spacecraft trajectories: the translunar and trans-Earth paths. But that seems to have lost momentum (no pun intended). That would be an interesting thing to model. I’ve simulated the LM descent and ascent accurately enough to satisfy me, but I haven’t tried the translunar and transearth trajectories. This reminds me, however, that several months ago I modeled a translunar trajectory for another project I was working on. I was contact by a fellow contemplating putting together a lunar X-prize team. Nothing became of it, but I did work out a couple sample trajectories for him just to see if his plan was feasible. The plan was for direct descent, i.e. no lunar orbit, so I simulated a lunar impact trajectory. It worked out pretty good, though I did make a few simplifications. I used a TLI delta-V of 3,150 m/s, which is comparable to the Apollo missions. In one of my simulations, for example, the impact velocity was 2,623 m/s. Escape velocity at the lunar surface is 2,375 m/s, so this indicates a considerable excess hyperbolic velocity. It’s looking more and more to me that the moon-centered inbound trajectory was likely hyperbolic. If so, I’m somewhat befuddled as to how a hyperbolic trajectory could result in a free return. In order to whip the spacecraft around the Moon and send it back in the general direction of Earth, it seems to me that the trajectory would have to be elliptical. Am I making any sense to you, Jay?
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Post by zorgon on Aug 24, 2008 0:04:16 GMT -4
L.O, do you think you could start just a temporary banning, since this would only be a first offense? Wow I finally get in here and John is being banned already? Dang! Same thing happened at Reality Uncovered. Never understood a forum that only wanted to hear one side... doesn't it get boring to alway agree with each other? How about the dust storms that NASA lists? How about the Sodium Atmosphere on the moon recorded by Boston University? How about the Lunar Fact Sheet from NASA that lists the components of that atmosphere (albeit the figures show less) but to say there is no atmosphere is kinda ridiculous What about the Sunset and sunrise rays on the moon? Supposedly from dust in the 'air' Do any of those count? because I would hate to dig them all up if no one will listen anyway.. Hmmm well Von Braun new it that they were one of America's 'manufactured' enemies... Also try reading Two Sides of the Moon: Our Story of the Cold War Space Race (Hardcover) by David Scott (Author), Alexei Leonov (Author) an astronaut and a cosmonaut Besides I thought everyone knew this? Heck its even shown in the old James Bond films .... So that both sides could have a reason to arm themselves... Why do YOU think there was a red phone on each leaders desk? Can anyone tell me what an atmosphere would look like that has no water vapor, has no dust or pollution in it (despite NASA's dust storms) and is only very low to the ground... what would an atmosphere like this look like? Seems no one is willing to answer this.. And just how much occultation would such an atmosphere show? As to the telescope slur... yes we are aware of telescopes... we have one of the best photos of the moon ever taken and it was done with a 10 inch scope just outside of London under poor conditions... I have even had someone from NASA compliment us on that one... Of course I am assuming with that comment that you are a professional astronomer? Nothing personal you were the first post I felt like responding to... just luck of the draw... I tell ya though my FBI security check went trough a lot faster than getting on here
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Post by ajv on Aug 24, 2008 0:11:05 GMT -4
It appears that Apollo 8 was hyperbolic. In Apollo 8 mission report. Supplement 1: Trajectory reconstruction and postflight analysis ( PDF) page 37 they list the position & velocity vectors and for good measure the classical orbital elements for the CSM after MCC-4. (They actually list two sets of vectors in order to compare the RTCC and HOPE (tracking) solutions.) Here are the HOPE/TRW values: Coordinate System | MCI (Moon-centered! :-)) | TIME | GET 061:06:36.000 | X | -20404652.9 ft | Y | 105320326.2 ft | Z | 77026255.9 ft | XDOT | 1029.5138 ft/s | YDOT | -3193.5495 ft/s | ZDOT | -2366.2278 ft/s | SMA | -12162039.3 ft | ECC | 1.533236 | INC | 165.847 deg | NODE | 50.507 deg | ARG PERIAPSIS | 229.258 deg | TRUE ANOMALY | -124.826 deg | PERIOD | --- | APOASIS | --- | PERIAPSIS | 128.84 nautical miles above reference sphere |
Note the eccentricity: 1.533236. And the lack of an orbital period. Note also that at 25012 statue miles we're inside the moon-centric sphere. However, presumably the periapsis from these values doesn't take into account Earth perturbations or something because the predicted pericynthion reported at 061:29 was 62.3 nautical miles rather than the 128.84 above. Bob, perhaps you could push these figures into your orbital simulator and see what happens. I think the coordinate definition is on page 5.1-31 of the Guidance System Operations Plan but just planting the capsule at r travelling at v might be quite instructive.
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Post by laurel on Aug 24, 2008 0:16:40 GMT -4
Zorgon, John Lear hasn't been banned. He left voluntarily, whether he means to come back or not I have no idea, but he hasn't been banned.
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Post by Cavorite on Aug 24, 2008 0:52:23 GMT -4
How about the dust storms that NASA lists? How about the Sodium Atmosphere on the moon recorded by Boston University? How about the Lunar Fact Sheet from NASA that lists the components of that atmosphere (albeit the figures show less) but to say there is no atmosphere is kinda ridiculous What about the Sunset and sunrise rays on the moon? Supposedly from dust in the 'air' Do any of those count? because I would hate to dig them all up if no one will listen anyway.. What does any of that have to do with the claim that there is a breathable atmosphere on the Moon? Who says there is no atmosphere as opposed to the claim made in this thread that there is an atmosphere thick enough to support life? It's a bit rude to accuse board members of ignoring evidence in your first post. Can anyone tell me what an atmosphere would look like that has no water vapor, has no dust or pollution in it (despite NASA's dust storms) and is only very low to the ground... what would an atmosphere like this look like? Seems no one is willing to answer this.. Who had asked it before now? What rationale is there for all of these artificial constraints on the attributes of this putative atmosphere? If there is water on the surface (implied by the presence of "vegetation"), how come there is none in the atmosphere? What do you know about the refractive index of air? What keeps the atmosphere "low"? How low is low? Why isn't this artificial height constraint seen anywhere else in the solar system? And just how much occultation would such an atmosphere show? I assume you mean refraction. You don't know? Do you think astronomers might?
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Post by LunarOrbit on Aug 24, 2008 0:57:18 GMT -4
Wow I finally get in here Sorry about the delay. The forum doesn't notify me when there are new members and I didn't notice you had joined until this evening. He won't be banned if he starts defending his claims and answering questions. Some of the other members of this forum have put a lot of time into their responses and he isn't treating them respectfully by ignoring them. We welcome hoax believers, all we ask is that they act with a level of maturity and defend their claims. People shouldn't make claims if they aren't willing to support them. Yes, it does, but I think we would be wasting our time discussing anything with people like John who are not willing to put any effort into the discussions. Anyone can say "there are millions of people living on the moon", defending that claim is another matter. John is apparently unable to tell the difference between "opinion" and "fact". You mean these storms? The ones discovered by an experiment left on the Moon by Apollo astronauts? They aren't the kinds of storms you find on Earth, they aren't caused by winds. I don't think anyone who knows better would say the Moon has no atmosphere at all, but it is so thin an atmosphere that it is essentially a vacuum. The "millions of people who live on the Moon" (according to John) could not breath such a thin atmosphere. If you have information to support your claims that is great. That is all we want from John. Well then, if it's in a Hollywood movie then it must be true. To facilitate last minute diplomacy to avoid a catastrophe. Just like in the movies "Fail Safe", "Dr. Strangelove", and "Sum of All Fears". Hey, if you can use Hollywood as a source then so can I. It depends on how thick the atmosphere is. John is claiming it is much thicker than it really is (thick enough to support people without spacesuits). If that was true than even a clean atmosphere would cause distortions. Like I said, the forum software doesn't notify me when new members join. If I don't notice an new name beside "Newest member: " at the bottom of the forum I won't be activating it right away. And believe it or not, I do have a day job and a life away from this forum.
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Post by Count Zero on Aug 24, 2008 1:18:46 GMT -4
You mean these storms? The ones discovered by an experiment left on the Moon by Apollo astronauts? They aren't the kinds of storms you find on Earth, they aren't caused by winds.. That is SO cool! I don't suppose we know enough about the phenomenon to know if it erodes and/or obscures footprints?
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Post by lennison on Aug 24, 2008 1:23:49 GMT -4
It�s looking more and more to me that the moon-centered inbound trajectory was likely hyperbolic. If so, I�m somewhat befuddled as to how a hyperbolic trajectory could result in a free return. In order to whip the spacecraft around the Moon and send it back in the general direction of Earth, it seems to me that the trajectory would have to be elliptical. Am I making any sense to you, Jay? If we ignore the earth, then a parabolic orbit around the moon causes the craft to return to the same point in the sky that it came from. A slightly hyperbolic orbit would leave a bit of a gap, tracing a less than complete trajectory across the sky when viewed from the moon. But if the earth is there, wouldn't that tend to close the gap? I whipped up a quick C program to do some simulations, but I think I need a bit of help with it. I am using these numbers from Wikipedia. EARTH_MASS 5.9736E+24 kg MOON_MASS 7.3477E+22 kg EARTH_MOON_DIST 3.84399E+08 m GRAV 6.67428E-11 Assuming a circular orbit of the earth and moon around each other, I get an orbital period of 27.28 days, which is pretty close. Then with an initial position and velocity of a spacecraft, I use a simple quadrature algorithm to track its progress. It sounds to me like more sophisticated algorithms get used, calculating the two-body position/velocity with respect to the near body, then adding the influence of the far body as a perturbation. But I figure computers are a lot faster now than in the 1960s, so I can make up for a lack of sophistication in the algorithm with some brute force. But, what I need to know is, does the craft travel in the earth-moon plane? Or does it leave that plane? And does it go in "front" of the moon (that is, does it fly to a position where the moon will be soon, due to its orbital motion), or does it go in "back" of the moon? If I know these answers, then I can run a few simulations and see. I should probably also use a more realistic model of the movement of the earth and moon around each other, but one thing at a time. Thanks!
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Post by Czero 101 on Aug 24, 2008 1:33:24 GMT -4
( Edit to add: Looks like L.O. and a few others beat me (I'm a slow typist sometimes ) to a few points, but I'll leave my message here anyway) How about the dust storms that NASA lists? How about the Sodium Atmosphere on the moon recorded by Boston University? How about the Lunar Fact Sheet from NASA that lists the components of that atmosphere (albeit the figures show less) but to say there is no atmosphere is kinda ridiculous No one here (as far as I know) actually said that the Moon has no atmosphere whatsoever. Perhaps you should read the original claims by John lear about a Lunar atmosphere and also some of the replies - which he pointedly ignored. For example: No more proof than I have that the moon has a breathable atmosphere. Ok... so you're saying you have no proof whatsoever of either of those fallacies. As long as we are clear on that. Here's a bit more information you did not know: The Moon has a breathable atmosphere equal to about 18,000 feet here on earth. It is not and does not have a vacuum. Uhm... since when...? From Wikipedia - Moon - AtmosphereThat's 10,000 Kg... over the entire surface of the Moon. So while not a true and complete vacuum, it's pretty darn close and it is certainly NOT breathable in any sense of the word. Continuing from Wikipedia - Atmosphere of the MoonI realize that at 18,000 feet (~3 miles), the Earth's atmosphere is pretty thin, but it still has about another 59 miles of gradually thinning atmosphere until the "edge of space" (the Kármán Line) is reached. But that does not make either statement less true. Actually, what it does do is make your statements nothing more than idle speculation, based upon no evidence, and apparently, no knowledge of the subject you are attempting to debate. Thanks for the info on Neils jet engine. No problem... and seeing as you did learn something here today that you had not known previously, perhaps you'll try to look at the information provided by myself and others in a less skeptical eye and hopefully learn where and why your assumptions and speculations are incorrect. As to the "Dust Storms" on the Moon, I found this article: Exerpt from NASA - Moon StormsWith regards to the "Sodium Atmosphere", it was actually discovered by NASA's Johnson Space Center about a decade before Boston U's Mendillo and Baumgardner reported it. From Science Magazine - Discovery of Sodium and Potassium Vapor in the Atmosphere of the MoonAlthough, Mendillo and Baumgardner do go into more detail as to how it is formed: Exerpt from BNET.com - The moon's atmosphere: space - sodium particles discovered 10,000 miles from surface, generated by sunlight - Brief Article (article originally published in Discover Magazine, February 1996): With regards to NASA's Moon Fact Sheet: You claim that the figures above are less than they should be. What is your evidence that those figures are incorrect? Cz
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Post by George Tirebiter on Aug 24, 2008 3:30:07 GMT -4
It’s looking more and more to me that the moon-centered inbound trajectory was likely hyperbolic. If so, I’m somewhat befuddled as to how a hyperbolic trajectory could result in a free return. In order to whip the spacecraft around the Moon and send it back in the general direction of Earth, it seems to me that the trajectory would have to be elliptical. I'm sure that Jay's answer will be much better than mine, but I'll take a stab at it anyway. I think this is just a frame-of-reference problem. If you were to stay in an Earth-centered reference frame, the trajectory would always be elliptical, but the orbital parameters would be increasingly perturbed as the craft flew past the Moon. The flyby trajectory is only hyperbolic if you look at it in a Moon-centered reference frame. Or, to put it another way, the outbound and inbound legs are both elliptical, but they're not the *same* ellipse. Another thing to consider is that the delta-V for a free-return trajectory is much more than is necessary for a Hohmann transfer. The lunar flyby is then a gravity-assist maneuver that decreases the spacecraft's velocity just enough to put it in the required Earth-return orbit.
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Post by Kiwi on Aug 24, 2008 3:44:50 GMT -4
I try to be patient with HBs, but there is a limit. Nothing is so indicative of deepest culture as a tender consideration of the ignorant. -- Ralph Waldo EmersonWorth remembering when the frustration levels rise.
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Post by tedward on Aug 24, 2008 4:52:07 GMT -4
Not sure how to reply to zorgon post with quote so a few bolds if I may.
Do any of those count? because I would hate to dig them all up if no one will listen anyway..
Always learning, what are the reference that you have to dig up?
Hmmm well Von Braun new it that they were one of America's 'manufactured' enemies....
Are you saying the cold war was a setup by the two powers?
As to the telescope slur... yes we are aware of telescopes... we have one of the best photos of the moon ever taken and it was done with a 10 inch scope just outside of London under poor conditions... I have even had someone from NASA compliment us on that one...
Always one to better my process where I can, interested in seeing this and how it was achieved. No web cam yet just the 350D. And a 8 inch.
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Post by chrissyo on Aug 24, 2008 6:01:42 GMT -4
we have one of the best photos of the moon ever taken and it was done with a 10 inch scope just outside of London under poor conditions...
... Huh? A 10" telescope under poor conditions at a heavily light polluted location is able to produce "one of the best photos of the moon ever taken"? Please excuse my skepticism of this statement. Would you be willing to show us said image, or give us some more information about it?
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Post by gwiz on Aug 24, 2008 6:14:54 GMT -4
I think this is just a frame-of-reference problem. If you were to stay in an Earth-centered reference frame, the trajectory would always be elliptical, but the orbital parameters would be increasingly perturbed as the craft flew past the Moon. The flyby trajectory is only hyperbolic if you look at it in a Moon-centered reference frame. Or, to put it another way, the outbound and inbound legs are both elliptical, but they're not the *same* ellipse. Another thing to consider is that the delta-V for a free-return trajectory is much more than is necessary for a Hohmann transfer. The lunar flyby is then a gravity-assist maneuver that decreases the spacecraft's velocity just enough to put it in the required Earth-return orbit. There are plenty of similar examples. When an asteroid, or a spacecraft on a gravity-assist trajectory, flies past the earth, its trajectory is hyperbolic relative to the earth and elliptic relative to the sun.
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Post by echnaton on Aug 24, 2008 7:25:48 GMT -4
we have one of the best photos of the moon ever taken and it was done with a 10 inch scope just outside of London under poor conditions... I have even had someone from NASA compliment us on that one...
The best in what way? Scientifically, artistically or....?
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