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12/11/18 at 11:17:13
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1  General / Discussion / Re: Moon orbit - max distance
 on: 10/28/18 at 11:21:35 
Started by wil | Post by frankuitaalst
The sim above gives us additional info about the stability of the Earth - Moon system in what concerns the Hill sphere .  
I gathered the output of the above sim ( Sma and eccentricity of all of the 100 minor bodies ) in a data file and represented the data  in a chart .  
The chart represents :  
 
X-axis : the Sma of each body ( 0 to 0.01 AU = 0 to 1.500.000 km )  
Y-axis : the eccentricity of each body ( 0 to 1 ) .  
 
The sim was ran untill no more  bodies escaped . This period covers 196 frames in the animation.  
 
One can (briefly ) see the sim starts with all bodies lined up at Ecc=0 and Sma = 1/300 AU and 1/200 AU ) = (1/3 and 1/2 Hill) .  
 
The eccentricies soon rise , also some Sma get bigger .  
After some time some bodies escape at Ecc around 0.8-0.6) while puping up their Sma , and escape to the right of the chart , escaping Earth's gravity field.  
This happens several times .  
 
After some time the system seems to "stabilize" , resulting in  dynamical behaviour , but without escaping bodies .  
At the end it seems bodies even at 1/2 Hill ( = 0.005 Sma) , but at appropriate eccentricities , do not have the "intention " to escape .  
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2  General / Discussion / Re: Moon orbit - max distance
 on: 10/28/18 at 05:32:37 
Started by wil | Post by frankuitaalst
I've made a little sim :  
in the sun -earth system : created 100 massless bodies , between 500.000 and 750.000 km , thus between 1/3 and 1/2 Hill . I gave them 0 eccentricity .
See Sim in annex.  
 
It is worthwile to see :  
* eccentricity of all the bodies rises ,  
* some bodies (about 10% ) escape the system . It is interesting to notice the escape goes over the L1 OR the L2 point  ( the line L2 L1 is directed towards the sun . So 1/2 Hill is partially stable .  
* and further :  when we zoom out in the sim one can observe the escaped bodies will occupy the L4 and L5 clouds .
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3  General / Discussion / Re: Moon orbit - max distance
 on: 10/18/18 at 16:14:01 
Started by wil | Post by wil
Ok.
Thus what is the real maximum distance in the case of the Moon, or in general: in any three-body scenario?
 
Hill by 2, 3, maybe e?
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4  General / Discussion / Re: Moon orbit - max distance
 on: 10/18/18 at 15:29:55 
Started by wil | Post by Tony
Hill Sphere is sometimes mistakenly interpreted as the volume with which an object can orbit. It is not.
In prograde orbits, objects can orbit out to about 1/3 of a Hill Sphere. In retrograde orbits, they can exceed 1/2 Hill Sphere. Anything past this and the Sun will strip them away.
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5  General / Discussion / Moon orbit - max distance
 on: 10/18/18 at 13:32:04 
Started by wil | Post by wil
The Hill sphere for the Earth is about 1.5 mln km.
 
But when I try to set only two times bigger distance to the Moon: 2x400 = 800 only, then the Moon escapes from the Earth immediately.
 
This is something wrong in the GS, or the Hill sphere is a nonsense?
 
This is about 1/3 of the Hill's distance possible for stable lunar orbit, thus about: 500 = 0.5 mln km only, maybe 550 !
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6  General / Discussion / Re: 300 Error when trying to access old threads...
 on: 08/12/18 at 03:26:49 
Started by stargate38 | Post by frankuitaalst
Hi Stargate,  
 
I checekd :  
Funny result : the posts "gravity assist " cannot be openend indeed .  
However if I perform a search for "assist " I get the posts listed in the search output and can see them in prview  .  
The posts themselves however cannot be openend . This means the posts aren't really lost I guess ....
 
Frank
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7  General / Discussion / Re: 300 Error when trying to access old threads...
 on: 08/02/18 at 10:01:19 
Started by stargate38 | Post by stargate38
I know you don't know how to recover them, but the text above the forum says "New Members need to post in the welcome thread within 24 hours from account activation to complete confirmation", which is impossible because the thread is inaccessible. Why are whole threads suddenly deleting themselves? Huh It shouldn't be happening. Maybe you should create a whole site backup, or something similar, just in case the whole forum goes down. Your server might have a failing hard drive, or some other form of corruption. You don't want the whole forum suddenly vanishing with no backups.
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8  General / Discussion / Re: 300 Error when trying to access old threads...
 on: 07/29/18 at 12:19:51 
Started by stargate38 | Post by Tony
Same answer as last time. I didn't write the forum software. I don't have a clue as to how to recover deleted messages. New users have to email me for an account because too many robots were making accounts.
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9  General / Discussion / Re: Autopilot in the browser version
 on: 07/29/18 at 12:17:38 
Started by Tony | Post by Tony
The Quick Help dialog box is for giving simple instructions to the user. You can change the color and size in Autopilot Now.
Code:
txtAreaQuickHelp.style.backgroundColor = '#440000';
txtAreaQuickHelp.style.color = '#FF00FF';

txtAreaQuickHelp.style.height = '150px';
divQuickHelp.style.height = '150px'; 

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10  General / Discussion / Re: 300 Error when trying to access old threads...
 on: 07/25/18 at 14:52:58 
Started by stargate38 | Post by stargate38
Sorry for bumping up an old thread, the Welcome (Terms of Use) thread is giving me the same error as the others. Please fix it. If you don't, new users won't be able to activate their accounts, which is a major problem for this forum, as it blocks legit users as well. Also, the "Insert Flash" button isn't coming up for me.
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