A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Policy
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Airspace



 
 
Thread Tools Display Modes
  #21  
Old January 15th 10, 03:27 AM posted to sci.space.policy
Alain Fournier[_2_]
external usenet poster
 
Posts: 373
Default Airspace

Jorge R. Frank wrote:

Alain Fournier wrote:


Yes such orbits do exist. They are called geosychronous* orbits. You
can't have
one that stays over some northern (or southern) region, but russia
could launch
a satellite that stays above the Pacific, and the satellite could also
go over
some parts of eastern Siberia without going over another country.


Launching *into* a geosynchronous orbit without the *transfer orbit*
overflying any country would be a trick. Russia couldn't do it unless
they put a launch site in eastern Siberia.


They did build such a launch site in the 1990s. So that isn't a show
stopper. But even without that launch site, it can be done. The transfer
*orbit* doesn't have to be an orbit, it can be a quarter orbit.

ESA couldn't do
it because the transfer orbit would overfly Africa before reaching a
high enough altitude (and low enough speed) that the Earth rotates under
it and moves the groundtrack back over the Atlantic.


ESA could do it by having the beginning of their launch trajectory
being mostly vertical.

Of course it would be a pain to use less efficient trajectories just
to avoid overflying other countries. But not to the point where one
would just abandon satellites. Even if launch cost were double what
they currently are, satellites would still be launched.


Alain Fournier
  #22  
Old January 15th 10, 04:08 AM posted to sci.space.policy
Jorge R. Frank
external usenet poster
 
Posts: 2,089
Default Airspace

Alain Fournier wrote:
Jeff Findley wrote:

"Alain Fournier" wrote in message
...

Jeff Findley wrote:


"Pat Flannery" wrote in message
dakotatelephone...


Fusion295 wrote:


I'm not an American, so please don't interpret this as a pretext
for starting a flame war. Couldn't the US have just launcehd a
satellite into an orbit with such an inclination that it's doesn't
pass over the airspace of USSR?

That would be hard to do unless you put it into a low inclination
orbit, as anything of over 35 degrees would pass over some part the
Soviet Union after a few orbits.


And even worse, if you try not to overfly *any* other country, I'm
not sure such an orbit even exists.

Yes such orbits do exist. They are called geosychronous* orbits. You
can't have
one that stays over some northern (or southern) region, but russia
could launch
a satellite that stays above the Pacific, and the satellite could
also go over
some parts of eastern Siberia without going over another country. And
the US
could do the same going over Alaska and the Pacific. I suspect it
would also be
possible to do an orbit that would go over the contiguous 48 US
states, then go
around South America and come back. That would have to be a highly
elliptic
geosynchronous orbit, if it is possible.



True, but that's *extremely* limiting, except for things like domestic
communications satellites. I said in an earlier post that the US
wanted to eventually develop spy satellites (optical and radio), which
need to overfly the country of interest. In order to do that, they
had to keep quiet about Sputnik.


We agree here. Well maybe it wasn't an absolute necessity, but keeping
quiet
about Sputnik certainly did make things easier.

Other than that, no you can't orbit Earth without flying over at
least two
countries, so you will overfly at least one foreign country.

*Not to be confused with geostationary orbits. Geosynchronous orbits
can go
north and south but come back above the same points at each orbits.
Geostationary
orbits are a special case of geosynchronous orbits where the orbit is
circular
and the inclination is zero.



I know, but a satellite trying to observe the central or eastern US
which is in such an orbit would end up over Central America or even
Cuba, not very friendly countries during the Cold War. Again, not
very useful orbits.


I haven't done the computations but I think you could have an elliptical
geosynchronous orbit with perigee over central United States. At perigee
the satellite must be moving eastward. With the right orbital elements you
might be able to have it going mostly southward over the Atlantic, have
apogee south of South America. At apogee the satellite must be moving
westward. So for the northward part of the ride you could be above the
Pacific. So maybe you could have a satellite that overflies central
United States but no other country.


The southern tip of South America extends past 50 deg S latitude. The
US-Canadian border is at 49 deg N latitude. So I don't think it's
possible to have an orbit that misses South America without hitting at
least part of Canada.
  #23  
Old January 15th 10, 06:39 AM posted to sci.space.policy
Pat Flannery
external usenet poster
 
Posts: 18,465
Default Airspace

Jeff Findley wrote:
I know, but a satellite trying to observe the central or eastern US which is
in such an orbit would end up over Central America or even Cuba, not very
friendly countries during the Cold War. Again, not very useful orbits.


At least for a first launch, it would have been possible for the US to
put one into a orbit that didn't pass over the USSR, as Cape Canaveral
is at around 28.5 degrees north, and the southernmost point of the USSR
was at around 36 degrees north.
The USSR on the other hand couldn't launch one that didn't pass over the
continental US, as Baikonur is at around 48 degrees north*, and the tip
of Florida at around 25 degrees north.

* So is Kapustin Yar.

Pat
  #24  
Old January 15th 10, 01:24 PM posted to sci.space.policy
Alain Fournier[_2_]
external usenet poster
 
Posts: 373
Default Airspace

Jorge R. Frank wrote:

Alain Fournier wrote:

Jeff Findley wrote:

"Alain Fournier" wrote in message
...

Jeff Findley wrote:


"Pat Flannery" wrote in message
dakotatelephone...


Fusion295 wrote:


I'm not an American, so please don't interpret this as a pretext
for starting a flame war. Couldn't the US have just launcehd a
satellite into an orbit with such an inclination that it's
doesn't pass over the airspace of USSR?


That would be hard to do unless you put it into a low inclination
orbit, as anything of over 35 degrees would pass over some part
the Soviet Union after a few orbits.



And even worse, if you try not to overfly *any* other country, I'm
not sure such an orbit even exists.


Yes such orbits do exist. They are called geosychronous* orbits. You
can't have
one that stays over some northern (or southern) region, but russia
could launch
a satellite that stays above the Pacific, and the satellite could
also go over
some parts of eastern Siberia without going over another country.
And the US
could do the same going over Alaska and the Pacific. I suspect it
would also be
possible to do an orbit that would go over the contiguous 48 US
states, then go
around South America and come back. That would have to be a highly
elliptic
geosynchronous orbit, if it is possible.



True, but that's *extremely* limiting, except for things like
domestic communications satellites. I said in an earlier post that
the US wanted to eventually develop spy satellites (optical and
radio), which need to overfly the country of interest. In order to
do that, they had to keep quiet about Sputnik.



We agree here. Well maybe it wasn't an absolute necessity, but keeping
quiet
about Sputnik certainly did make things easier.

Other than that, no you can't orbit Earth without flying over at
least two
countries, so you will overfly at least one foreign country.

*Not to be confused with geostationary orbits. Geosynchronous orbits
can go
north and south but come back above the same points at each orbits.
Geostationary
orbits are a special case of geosynchronous orbits where the orbit
is circular
and the inclination is zero.



I know, but a satellite trying to observe the central or eastern US
which is in such an orbit would end up over Central America or even
Cuba, not very friendly countries during the Cold War. Again, not
very useful orbits.



I haven't done the computations but I think you could have an elliptical
geosynchronous orbit with perigee over central United States. At perigee
the satellite must be moving eastward. With the right orbital elements
you
might be able to have it going mostly southward over the Atlantic, have
apogee south of South America. At apogee the satellite must be moving
westward. So for the northward part of the ride you could be above the
Pacific. So maybe you could have a satellite that overflies central
United States but no other country.



The southern tip of South America extends past 50 deg S latitude. The
US-Canadian border is at 49 deg N latitude. So I don't think it's
possible to have an orbit that misses South America without hitting at
least part of Canada.


Remember we are talking about an elliptical orbit here. I'm not sure
myself that such an orbit could avoid entirely South America and
Africa, but I think it can be done.


Alain Fournier
  #25  
Old January 15th 10, 03:53 PM posted to sci.space.policy
Jeff Findley
external usenet poster
 
Posts: 5,012
Default Airspace


"Alain Fournier" wrote in message
...
Jorge R. Frank wrote:
The southern tip of South America extends past 50 deg S latitude. The
US-Canadian border is at 49 deg N latitude. So I don't think it's
possible to have an orbit that misses South America without hitting at
least part of Canada.


Remember we are talking about an elliptical orbit here. I'm not sure
myself that such an orbit could avoid entirely South America and
Africa, but I think it can be done.


Since you're asserting that it is possible, please prove it. I don't think
it is possible because an elliptical orbit still has to exist in one orbital
plane, which is what determines the north and south latitudes of the orbit.
Altitude (i.e. circular versus elliptical) has nothing to do with the
orbital plane of an orbit.

If you don't want to do the math, there are orbit simulators out there.
Determine the orbital parameters which solve the problem, then post them
here so everyone can double check the result.

Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon


  #26  
Old January 16th 10, 01:54 AM posted to sci.space.policy
Alain Fournier[_2_]
external usenet poster
 
Posts: 373
Default Airspace

Jeff Findley wrote:

"Alain Fournier" wrote in message
...

Jorge R. Frank wrote:

The southern tip of South America extends past 50 deg S latitude. The
US-Canadian border is at 49 deg N latitude. So I don't think it's
possible to have an orbit that misses South America without hitting at
least part of Canada.


Remember we are talking about an elliptical orbit here. I'm not sure
myself that such an orbit could avoid entirely South America and
Africa, but I think it can be done.


Since you're asserting that it is possible, please prove it.


No I am not asserting that it is possible. I said so above. I just
don't know that it can't be done.

I don't think
it is possible because an elliptical orbit still has to exist in one orbital
plane, which is what determines the north and south latitudes of the orbit.
Altitude (i.e. circular versus elliptical) has nothing to do with the
orbital plane of an orbit.


You are right about the orbit having to go as far north as it goes far south.
So if it goes to 50 degrees south it must go to at least 50 degrees north.
But the most northern point of the orbit doesn't have to be directly north
of the most southern point. So if the most southern point is just south
of South America, the most northern point can be in the northern
Atlantic or northern Pacific.

Imagine an elliptical orbit with its major axis on the equatorial plane
and such that the satellite is going northward at perigee.
The southern most part of the orbit is not the middle of the ellipse, it
will be directly below the centre of Earth and the northern most part
directly above the centre of Earth. So in the northward leg of the
ellipse, the satellite will travel 180 degrees east in less than half
the orbital period (less than 12 hours that is). So when it reaches
its northern most point, Earth won't have had enough time to make
half a rotation and the northern most part of the orbit will be east
of the southern most part, potentially in the Northern-Atlantic.
Conversely if the satellite is going southward at perigee, then the
northern most part of the orbit will be west of Cap Horn, potentially
in the Pacific.

I don't think it would be possible to completely avoid over flying
all other countries than the US with an orbit having its major axis
in the equatorial plane. But the above shows that you can have
the southern most part of the orbit south of Cape Horn and the
northern most part not in Canada. And this will hold true for some
range of angle of the major axis of the ellipse.

If you don't want to do the math, there are orbit simulators out there.
Determine the orbital parameters which solve the problem, then post them
here so everyone can double check the result.


Is it possible to find a trajectory that will not pass over any other
country than the US, I really don't know, I don't know that it can
be done and I don't know that it can't, but anyway I don't care. If
someone wants to do the math to figure it out and doesn't know
how to do it, I can explain how, but I doubt anyone really wants
to do that. But I certainly will not go on the web to find an orbital
calculator to do it. I can see why someone would want to do it with
pen and paper, it can be a fun challenge, but making a computer
do it is pointless, the computer won't think of it as a fun challenge.
And nobody needs to know the answer.


Alain Fournier
  #28  
Old January 18th 10, 03:23 AM posted to sci.space.policy
Pat Flannery
external usenet poster
 
Posts: 18,465
Default Airspace

Dr J R Stockton wrote:

ISTM that Vanguard I did not need to, and probably did not, pass over
any part of the Soviet Bloc, but could not have avoided crossing China.


Orbital inclination was 34.25 degrees, which would have put it very near
the southern border of the Turkmenistan SSR.

Pat
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
AIRSPACE, BRIDGES AND WATERWAY RESTRICTIONS IN EFFECT FOR STS-115 Jacques van Oene Space Shuttle 0 August 22nd 06 11:39 PM
Light plane airspace Carol Singer Space Shuttle 20 August 29th 05 02:00 AM
Lasers To Signal Airspace Breaches David Amateur Astronomy 2 April 17th 05 12:03 PM
Where does "airspace" begin or end [email protected] Policy 6 April 13th 05 07:44 PM
[CNN] Gov to use green/red lasers as airspace warning signals Claude Ortega Amateur Astronomy 9 February 15th 05 04:15 AM


All times are GMT +1. The time now is 12:47 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.