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Orbital Mechanics

Posted by: campbelp2002 - Thu Dec 23, 2004 7:49 pm
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Orbital Mechanics 

Could an object spiral into the Sun?
Of course! 64%  64%  [ 16 ]
No way! 28%  28%  [ 7 ]
I used to think so, but now I don't. 0%  0%  [ 0 ]
I didn't think so before, but now I do. 8%  8%  [ 2 ]
Total votes : 25

Orbital Mechanics 
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Post    Posted on: Thu Mar 10, 2005 11:10 pm
Umm..... Maybe I missed something here, but why not just chuck something in the general direction of the Sun with a really low velocity, and let dear old Mr. Newton do all the hard work?

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Post    Posted on: Thu Mar 10, 2005 11:36 pm
spacecowboy wrote:
Umm..... Maybe I missed something here, but why not just chuck something in the general direction of the Sun with a really low velocity, and let dear old Mr. Newton do all the hard work?


That works fine, as long as it is moving slowly when measured from the right viewpoint. Try tossing the guy walking along the highway a hamburger, without slowing down. We have never built a rocket capable of “slowing down” from Earth’s mad speed around the Sun to anything reasonable.


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Post    Posted on: Thu Mar 10, 2005 11:54 pm
Ah. Good point. <slaps self>

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Post    Posted on: Fri Mar 11, 2005 2:12 am
rpspeck wrote:
No, I didn't read it all. So I am responding to the question.
Yes an object can spiral into the sun UNDER THRUST.
Yes, an almost passive load of trash could use a solar sail to spiral into the sun.
(or outward, but its progress would slow down rapidly with distance).
Yes, spiraling into a star seems to be predicted when relativistic effects are included.
Well I can't change the poll wording now, but I meant, "could an object spiral into the sun due only to the Sun's gravity"


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Post    Posted on: Fri Mar 11, 2005 11:53 am
Peter,

please stop it unless you clarify all the definitions. Please remeber that there have been often differences in defintions between our thoughts and concepts of thinking.

Sigurd recommended an end of this discussion - and he is right.

I will continue my calculations, email you results and post the result here when my calculations are terminated. A lot of work kept me from continuation until today again but this is changing currently.



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Post    Posted on: Fri Mar 11, 2005 2:26 pm
That is what I just did, clarified a definition.
If someone is interested and posts here, I will reply to them. If this thread bothers you, don't read it.


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Post    Posted on: Fri Mar 11, 2005 10:19 pm
Added note, the curious scarcity of gas and dust in the solar system suggest that material is continually spiraling into the sun. If it were not, we would have a huge, Saturn like ring in the equatorial plane (accretion ring). The solar wind will add a damping, drag factor to small particles, particularly after these particles pick up a charge, which greatly increases their interaction range (and converts its profile to inverse square, rather than a very abrupt force cutoff (contact limited)).

As a rough order of magnitude I suggest orbital lifetimes of less than a year for orbiting gas molecules, a thousand years for dust, one million years for grains of sand, and a billion years for rocks. (A “rough order of magnitude” estimate can be considered to be within one thousand times to one thousandth of the true value).

I doubt that this is the time frame you were looking for. :(


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Post    Posted on: Sat Mar 12, 2005 10:12 am
Peter,

my post didn't have anything to do with "not like it". You started this thread as a reaction to my posts under the thread about the disposal of radioactive materials into th sun.

You didn't clarify a definition but your question - you added a restriction or by-condition. That's reasonable and good.

The definition we had differences in were those of orbit, spiral, special conditions and special point.

"orbit" can be defined mathematically around a then mathematical point without any extension, physically around a physical body that - an contrary to the mathematical point - has extension, physically as a path within a region with constnt conditions or - problematic - ar within a region where the conditions can be changing in. At orbits around sun without going under the surface the gravitating mass is in total in the center of the orbits - at orbits going under the surface of sun that's NOT the case.

The choice of one of these definitions unpreventably determines the choice of the definition for "spiral".

And last but not least I have clarified since long that I didn't use neither a mathematical nor a physical definition for spiral.

As far as I remeber you always have been definitions different to thos I have been using.

Please clarify what definitions for orbit or spiral you are using - you will refresh all the unsane chaos else I fear. That should be prevented.



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Post    Posted on: Sat Mar 12, 2005 5:40 pm
I am speaking of a mathematical calculation of the movement on one object under the gravity of another object. For example an asteroid orbiting the sun. And by spiral I mean any path that goes around the sun more than once and gets closer each time it goes around. In particular, if you want to dispose of waste in the sun, and you carry a package of waste in a space craft that is not on a collision course with the sun, then when you release the package it will never hit the sun. I have said all that many times before.


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Post    Posted on: Sun Mar 13, 2005 10:08 am
Alright - you clarified yor defintion of the term spiral now. You clarified it relatively exacly.

One additional comment I have to make here: Your comment on my thinking and thoughts is idicating that your image iof that is too far from the facts and from my posts - I have been speaking of special concitions and especially I didn't use your definition which menas that your conclusions from YOUR defininitions may - or will - be right but cannot be applied to judge my thoughts and conclusions because of incompatibility. Compatibility requires the use of identical definitions.

And noone can claim authority only by having siad or post an issue repetedly. Your arguments didn't be convincing because of the difference in definitions. Our emails to each other were and still are positive but I#m sorry to have to remark that one of the emails contians signs of error about your image of what I am thinking. And you don't like my method - that'sa no argment from which it could be concluded that the method is wrong etc.

I don''t say that to discuss it here - I say it because you shouldn't argue that way with someine else here. Please don't do it with rbspeck especially and don't do it with leaders or members of any other XPRIZE- or ASP-team here because they are people of spacecraft-practice - you and me are not such people of spacecraft-practice and so between us internally it's not that problem.



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Post    Posted on: Mon Mar 14, 2005 1:24 pm
I might point out that all this could be solved if we could all find one good aerospace lexicon, and stick with it.

So why can't we all just get a long(neck)?

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Post    Posted on: Mon Mar 21, 2005 3:00 am
rpspeck wrote:
spacecowboy wrote:
Umm..... Maybe I missed something here, but why not just chuck something in the general direction of the Sun with a really low velocity, and let dear old Mr. Newton do all the hard work?


That works fine, as long as it is moving slowly when measured from the right viewpoint. Try tossing the guy walking along the highway a hamburger, without slowing down. We have never built a rocket capable of “slowing down” from Earth’s mad speed around the Sun to anything reasonable.


Most dudesome,
The speed that the Earth rotates around the Sun is irrelevent, as is the fact that the Earth is rotating aroung the sun at all. Consider the situation if the only objects in the universe were
1. The Sun, and
2. The Earth
Now let us look at this situation fromi the eath's point of view. The sun, from the earth's point of view, is spinning in place, but NOT moving relative to the earth. WHY the earth is not moving relative to the sun is irrelevant. So when my brave little piece of radioactive waste, or space junk, or whatever, starts moving towards that spinning sun,
1. The pull of the sun's gravity on the space junk increases
2. The object gets closer to the sun
3. The pull of the sun's gravity increases some more
4. The object gets even closer to the sun
5. . . . etc.
In the end, the object fries.
Sof Sof, because gravity increases as the object gets closer to the sun, one doesn't need to aim so precisely..
Of course, the larger the object, the less precisely one has to aim.
In any case, aiming shouldn't be so hard. Just aim a Sidewinder heat-seeking missile in the general direction and attach a cord and that shoud do the trick.

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Post    Posted on: Mon Mar 21, 2005 3:41 am
SuperShuki wrote:
The speed that the Earth rotates around the Sun is irrelevent, as is the fact that the Earth is rotating aroung the sun at all. .

It is totally relevent.

SuperShuki wrote:
The sun, from the earth's point of view, is spinning in place, but NOT moving relative to the earth. .

Yes it is. The Sun as seen from the Earth moves once around the sky in a year.

SuperShuki wrote:
WHY the earth is not moving relative to the sun is irrelevant.

The Earth IS moving realitive to the Sun. You even said so yourself...
SuperShuki wrote:
The speed that the Earth rotates around the Sun


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Post    Posted on: Mon Mar 21, 2005 1:17 pm
I do see what he's saying, though: all you should really have to do is fire a low-thrust rocket "backwards" (if you assume Earth to be moving "forwards"), and (if you wanna get really fancy) have the package swing once around Venus. You don't really have to slow the package down that much: Earth is in a stable orbit. Any loss of energy from that point will leave an object in a decaying orbit. All you have to do is to keep the package losing energy at the same low rate, and voila, six-month toast.

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Post    Posted on: Mon Mar 21, 2005 9:35 pm
campbelp2002 wrote:
SuperShuki wrote:
The speed that the Earth rotates around the Sun is irrelevent, as is the fact that the Earth is rotating aroung the sun at all. .

It is totally relevent.

Is not! (is too) Is not! (Is too) . . .

SuperShuki wrote:
The sun, from the earth's point of view, is spinning in place, but NOT moving relative to the earth. .

Yes it is. The Sun as seen from the Earth moves once around the sky in a year.

SuperShuki wrote:
WHY the earth is not moving relative to the sun is irrelevant.

The Earth IS moving realitive to the Sun. You even said so yourself...
SuperShuki wrote:
The speed that the Earth rotates around the Sun


Most dudesome,
from the perspective of a third object, the earth is moving around the sun. But if you only consider the sun and the earth, Neither object is moving. In order to be moving, they would have to be getting closer of farther from one another, which they are not (assuming the Earth is in a stable, completely circular orbit). Movement is relative.

[/i]

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