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 _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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