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Post by Kiwi on Aug 24, 2008 22:26:27 GMT -4
...I’ve modeled a sample trajectory... Thanks, Bob. That looks to me, in my ignorance of such things, more like the trajectory I'd expect with a stationary moon, but I assume that it takes the moon's motion into account. Is that so? Perhaps the scale is fooling me. It would certainly be helpful if you could continue with this and show an actual Apollo trajectory with the relative positions of the spacecraft and the moon shown at appropriate intervals, along with the equigravisphere and the 40000 statute mile circle ajv mentions. I have trouble envisioning the equigravisphere as an actual sphere, instead of a hot-air-balloon shape. A series of diagrams at different times and finished with an all-in-one-one diagram, may show the situation best. Thanks for your efforts. I have spent years wanting to see a realistic illustration of the trajectory. The illustrations in most books appear to be grossly oversimplified and Hollywood doesn't help, with translunar injection in From the Earth to the Moon occuring in daylight with the spacecraft pointing directly at the moon as it travels in the wrong direction above the wrong part of the earth and with the wrong lighting on the moon. Even if pointing at the moon was accurate, I imagine the earth would initially pull the spacecraft away from such a path, but Hollywood doesn't show that.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Aug 24, 2008 23:55:24 GMT -4
That looks to me, in my ignorance of such things, more like the trajectory I'd expect with a stationary moon, but I assume that it takes the moon's motion into account. Is that so? Perhaps the scale is fooling me. What I've illustrated is the view if you were stationary high above the plane of the orbit looking down on it, with the Earth remaining fixed at 0,0. As the spacecraft traces out the blue trajectory, you'd also see the Moon revolving counter-clockwise around Earth, though the Moon is not shown. I did attempt to show the Moon in the enlarged illustration, with the position being that at pericythion. It looks like I'm showing the trajectory in relation to a stationary Moon, but that is not the case. This is a space fixed perspective in which you'd really see the Moon moving. I ought to be able to come up with something, though I don't know when I'll have the time (things are starting to get really busy at work -- there may be some overtime upcoming).
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Post by Cavorite on Aug 25, 2008 1:23:10 GMT -4
Would a plane change still be a component? I was under the impression that one was needed to end up in the correct orbit for a given landing site.
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Post by PeterB on Aug 25, 2008 7:04:48 GMT -4
Well you have to remember that the Berlin Wall came down in Nov 1989, and that the USSR collapsed in 1991. Very few people under 23 would really remember what it was like to live in a world that was on the brink of nuclear war, some have probably never heard of the Cuban Missile Crisis or know about things like Francis Gray Powers being shot down over the USSR on a U-2 spy mission. Even KAL-902 and KAL-007 are likely to be unknown to many of them. They just don't understand how different the world was went both sides had missiles pointing at each other and ready to go on a moment's notice. They're are likely the same ones that didn't get sweaty palms over the latest US/Russia standoff over Georgia... If you want a relatively painless introduction to the Cold War, I recommend the boardgame "Twilight Struggle" by GMT Games. At its heart, the game is a struggle between the USA and USSR for influence in various parts of the world. And for those with an interest in Apollo, the Space Race plays an important part in the game. Interestingly enough, the designers assess orbiting the Moon as more valuable in terms of victory points than actually landing on the Moon. Look at the various events on the cards, and you realise just how silly the idea is that the Cold War was faked.
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Bob B.
Bob the Excel Guru?
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Post by Bob B. on Aug 25, 2008 9:02:56 GMT -4
Would a plane change still be a component? I was under the impression that one was needed to end up in the correct orbit for a given landing site. It wouldn't surprise if some plane change was needed to make sure they were in exactly the right orbit. Of course it's possible all that was corrected for during the translunar part of the mission. The CSM also made several maneuvers in lunar orbit prior to LM descent in which out-of-plane errors could have been corrected. I'm afraid I really don't know. I do know, however, that the CSM had to make a fairly large plane change prior to LM ascent. This is because LM landing site moved out of the orbital plane while on the surface. The orbital plane had to be shifted to bring it back in line with the landing site before the LM could take off.
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Post by dmundt on Aug 25, 2008 12:40:53 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. There's ignorance and then there's willful ignorance.
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Post by dwight on Aug 25, 2008 16:35:00 GMT -4
And then there's just plain willful stupidity.
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Post by JayUtah on Aug 25, 2008 17:39:40 GMT -4
And willful deception.
People who simply don't know, aren't out of the ordinary. We all "don't know" something. Thankfully enough of the world is sheepishly supplicant and much of the rest is graciously accommodating.
The willfully ignorant and the willfully stupid are out of the ordinary, and highly annoying. They sadly tend to lurk in layers of management where they can often maximize their damage.
The willfully deceptive spread the gospel of willful ignorance to others who may not otherwise be so eager to embrace it. People like John Lear who purposely misinform and miseducate their audience based on their own unwillingness to admit ignorance deserve the least quarter in my battle plan.
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Post by Ginnie on Aug 25, 2008 17:42:30 GMT -4
An animated gif would be nice Bob.
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Bob B.
Bob the Excel Guru?
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Post by Bob B. on Aug 28, 2008 21:09:52 GMT -4
A series of diagrams at different times and finished with an all-in-one-one diagram, may show the situation best. I’ve taken your suggestion and created a series of illustrations that, I think, better shows my simulated circumlunar trajectory. The multiple illustrations gives a better feel of motion and position versus time. I didn’t do the all-in-one diagram, however. I’ve split this off in separate thread in The Reality of Apollo forum: Circumlunar Free Return Trajectoryand Hollywood doesn't help, with translunar injection … with the spacecraft pointing directly at the moon That doesn’t really bother me very much. Although it is true that we aim for a point ahead of the Moon, the TLI burn actually takes place around the opposite side of the Earth. In fact, as you will see in my illustrations, when TLI begins the spacecraft is actually pointing about 40 degrees behind the Moon. Within only minutes after TLI, the spacecraft swings around Earth and the direction of travels sweeps past the Moon and moves toward a point in front of the Moon. An animated gif would be nice Bob. I don’t know how to do that, but I’m willing to have a volunteer do it for me. ;D
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Post by Ginnie on Aug 29, 2008 0:51:10 GMT -4
Here's a quick one using the illustrations you provided. Note the lack of detail. I had to scale it down to keep the file size down. I could use the complete originals if you wish for one to be made of them. The I would also put some of the data in there too, (time, speed etc).
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Bob B.
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Post by Bob B. on Aug 29, 2008 8:25:57 GMT -4
Thanks, Ginnie. That illustrates the situation nicely even though the scale is small. Why don't we move any future discussion about this to the new thread I started?
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