Re: Long term viability of geosynchronous orbits

From: Jonathan W (tlj1899@gmail.com)
Date: Fri Dec 07 2012 - 23:25:06 UTC

  • Next message: Peter Wakelin: "SATOBS 2012 December 07"

    Andrew,
    
    I'm not an expert on this, but I believe that quantum physics has very,
    very little - if anything - to do with orbital mechanics.  Newtonian
    physics works great for almost everything.  It breaks down when you go
    extremely fast (relativistic physics), or get extremely tiny (quantum
    physics).  Possibly, it also breaks down when you get extremely large (dark
    matter?), as in the size of something like a galaxy.
    
    Jonathan
    
    On Fri, Dec 7, 2012 at 5:09 PM, Andrew Coyle <andrewgcoyle@yahoo.com> wrote:
    
    > Interesting.  Very interesting that all measurements are done in the
    > classical geocentric math - we measure bodies in space from the non mobile
    > perspective.  Is quantum theory useful?
    >
    > Andrew
    >
    >
    > On Dec 7, 2012, at 6:00 PM, Jonathan W <tlj1899@gmail.com> wrote:
    >
    > > George (and everyone else),
    > >
    > > Thank you for your very through responses.  I knew that the atmospheric
    > > drag at 22,300 miles is very low, but I didn't realize that it is
    > > practically zero.  I also appreciated the comments on why we don't have
    > any
    > > tiny moons at this moment in time.
    > >
    > > Jonathan
    > >
    > > On Fri, Dec 7, 2012 at 1:52 PM, George Roberts <gr@gr5.org> wrote:
    > >
    > >> I thought that by now Ted would say something but I guess he hasn't been
    > >> reading this thread.
    > >>
    > >> GEOSYNCHRONOUS VERSUS GEOSTATIONARY
    > >>
    > >> First of all, the orbits are called geosynchronous, not geostationary.
    > >> Geostationary refers to a particular geosynchronous orbit that doesn't
    > >> deviate north or south from the equator.
    > >>
    > >> Geostationary is unstable even over one year due to the moon and
    > requires
    > >> fuel to maintain.  Pretty quickly dead satellites start to drift north
    > and
    > >> south by up to some amount (23 degrees maybe?) then drift back into
    > >> geostationary again, then back to non stationary.
    > >>
    > >> The orbit form earth looks like the satellite moves north and south
    > along a
    > >> line perpendicular to the equator.
    > >>
    > >> This doesn't answer the question about viability as geosynchronous can
    > be
    > >> stable for I'm sure thousands of years.
    > >>
    > >> DRAG
    > >> Another issue discussed was drag at that altitude.  Yes, there's drag
    > but
    > >> it's probably too small to worry about.  Someone correct me.
    > >>
    > >> TIDES
    > >> I've read that ignoring drag, anything orbiting completely inside
    > >> geostationary distance will have it's orbit decay due to tides.
    >  Anything
    > >> outside that distance will increase it's orbit due to tides.  The moon
    > is a
    > >> good example.  It is outside that distance (by a factor of about 10) and
    > >> has
    > >> been moving farther and farther away from the earth despite drag.  The
    > >> energy to move the moon to a higher orbit came from the earth's
    > rotation -
    > >> the earth is rotating slower and slower as the moon's orbit is lifted
    > >> higher
    > >> and higher.  But the closer you are to geosync, the smaller the effect.
    > >> Which leads us to graveyard orbits.
    > >>
    > >> GRAVEYARD ORBITS
    > >> http://en.wikipedia.org/wiki/Graveyard_orbit
    > >> When a geosynch sat gets down to 3 months left of fuel they usually
    > send it
    > >> into a Graveyard orbit which is *higher* than geosynch.  The goal is for
    > >> all
    > >> dead geosynch satellites to go there but only 1/3 or so make it.  The
    > >> reason
    > >> for moving it higher versus lower is so that it is out of the way of new
    > >> geostationary sats on their way to their new orbit.
    > >>
    > >> HOW LONG?
    > >> But none of this answers the question, how long would a geosynch sat
    > last?
    > >> I don't know the answer.  I suspect it's much less than 100 million
    > years.
    > >> If it was that long then I would expect us to have lots of other small
    > >> moons
    > >> up there.  I suspect it's more like thousands of years but I really
    > don't
    > >> know.   Maybe 100,000 years.
    > >>
    > >> A two body orbit is amazingly stable.  Add a third body (like the moon)
    > and
    > >> things are very unstable.  There aren't very many (any?) stable orbits
    > left
    > >> inside the orbit of our moon.  Otherwise we would have more moons.
    > >> Including only Earth, Moon, Sun, Jupiter and trying to find a stable
    > orbit
    > >> inside the moon's orbit that lasts more than a million years is probably
    > >> impossible.
    > >>
    > >> So I don't think this photo-disc-message will last long enough for
    > aliens
    > >> to
    > >> find it.  It would have been better to put it on the moon.
    > >>
    > >> - George Roberts
    > >> http://gr5.org
    > >>
    > >> _______________________________________________
    > >> Seesat-l mailing list
    > >> http://mailman.satobs.org/mailman/listinfo/seesat-l
    > > -------------- next part --------------
    > > An HTML attachment was scrubbed...
    > > URL:
    > http://mailman.satobs.org/mailman/private/seesat-l/attachments/20121207/5791f265/attachment.html
    > > _______________________________________________
    > > Seesat-l mailing list
    > > http://mailman.satobs.org/mailman/listinfo/seesat-l
    >
    -------------- next part --------------
    An HTML attachment was scrubbed...
    URL: http://mailman.satobs.org/mailman/private/seesat-l/attachments/20121207/1d96bf9c/attachment.html 
    _______________________________________________
    Seesat-l mailing list
    http://mailman.satobs.org/mailman/listinfo/seesat-l
    



    This archive was generated by hypermail 2b29 : Fri Dec 07 2012 - 23:25:46 UTC