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stationary object just above earth

 
 
Reply Wed 10 Dec, 2008 10:34 pm
what would happen if you had a craft that could maintain its position,just above the earth,while the earth is spinning on its axis.would this craft survive would it be in the same location it went up in 24 hours
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Type: Question • Score: 9 • Views: 1,583 • Replies: 10
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Diest TKO
 
  1  
Reply Thu 11 Dec, 2008 12:31 am
@friedhoff1,
No stationary object would be able to say "up." An object may appear to be stationary in the sky, that is called a GEO orbit and it's at about 23,000 miles above earth moving incredibly fast.

T
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BillRM
 
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Reply Thu 11 Dec, 2008 06:09 am
@Diest TKO,
Not only do you need to be in a GEO distance orbit but to remain unmoving in the sky you also need to be in the plane of the equator.

If you are not in that plane you will be moving north and south during every 24 hours in the sky with the amount of movement depending on how many degrees you are from the equator.
0 Replies
 
Setanta
 
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Reply Thu 11 Dec, 2008 06:32 am
Alternatively, a craft could be launched, and then brought to a stationary position, although it's "stationary" nature would be more apparent than real--the object could not escape the effect of the earth's gravitational well, and the gravitational well of the moon. However close to "stationary" the object might be brought, it would not appear stationary from the earth. If it were in the plane of the ecliptic, it would appear to "rise" and "set."
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rosborne979
 
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Reply Thu 11 Dec, 2008 06:40 am
@friedhoff1,
Quote:
what would happen if you had a craft that could maintain its position,just above the earth,while the earth is spinning on its axis.would this craft survive would it be in the same location it went up in 24 hours

A geosynchronous orbit is an orbit around the Earth with an orbital period matching the Earth's sidereal rotation period.

A Geostationary orbit is a special case of the geosynchronous orbit which is circular (or nearly circular) and at zero (or nearly zero) inclination, that is, directly above the equator.

But both of these conditions assume that the object is in orbit.

The condition you seem to be describing sounds like any object which is not orbiting. Any object which is not in orbit would require continuous trust to counteract gravity.

The only other way to do it would be to insert the object into a Lagrange Point, of which there are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects.

parados
 
  1  
Reply Thu 11 Dec, 2008 07:15 am
@friedhoff1,
The answer would be yes, but it all depends on the neighborhood and whether someone steals the concrete blocks its sitting on.



This is assuming that 8" is just above earth.
Diest TKO
 
  1  
Reply Thu 11 Dec, 2008 11:49 am
@rosborne979,
rosborne979 wrote:

The only other way to do it would be to insert the object into a Lagrange Point, of which there are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects.


I thought about this too, but in any of the Lagrange points the object would appear to be moving. I'm assuming the question is using the word stationary in terms of the ground track.

BillRM - Yes, you are correct, any inclination would make a object in a GEO orbit appear to do a figure8 type motion in the sky and thus not stationary.

T
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BillRM
 
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Reply Thu 11 Dec, 2008 12:10 pm
@Diest TKO,
I am old enough to remember when the Mercury Capsules ground tracks was being display on TV and the very odd sin wave shapes on a flat map that was produce.

I can still remember getting my hand on the family globe in order to figure out how this odd ground track was being created as the TV people never bother to address the issue.
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roger
 
  1  
Reply Thu 11 Dec, 2008 12:17 pm
@parados,
parados wrote:

The answer would be yes, but it all depends on the neighborhood and whether someone steals the concrete blocks its sitting on.



This is assuming that 8" is just above earth.


That sounds like something I should have thought of.
0 Replies
 
Cycloptichorn
 
  1  
Reply Thu 11 Dec, 2008 12:22 pm
@friedhoff1,
friedhoff1 wrote:

what would happen if you had a craft that could maintain its position,just above the earth,while the earth is spinning on its axis.would this craft survive would it be in the same location it went up in 24 hours


You originally stipulated that the craft was 'capable' of maintaining it's position, so your question seems a little odd to begin with.

Would the craft survive? If it could maintain it's position, as you said, sure. It would probably take constant thrust though.

Would it be in the same location? Depends on your frame of reference. The earth travels around the sun and the sun travels through our galaxy which is itself traveling; from that perspective, the answer is clearly no.

Cycloptichorn
0 Replies
 
Butrflynet
 
  1  
Reply Thu 11 Dec, 2008 12:45 pm
From the wording of the question it sounds as if he is referring to the craft maintaining the altitude above the earth against the force of gravity.
0 Replies
 
 

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