tag:blogger.com,1999:blog-22973357.post2529036122934437119..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Sputnik, fifty years laterSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger19125tag:blogger.com,1999:blog-22973357.post-30484828154501326742007-10-21T16:54:00.000-04:002007-10-21T16:54:00.000-04:00Dear Amara,thank you very much for getting back to...Dear Amara,<BR/><BR/><BR/>thank you very much for getting back to my questions, and for the detailed answers and links. That "Life of the rocket booster" video is really great!<BR/><BR/>Concerning the aluminium oxide spheres, I've searched around a bit and found a page on <A HREF="http://www.sis.lr.tudelft.nl/Propulsion_details/Data/Propellant_properties_files/Solid_props.htm" REL="nofollow">stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25723955457240902102007-10-18T18:45:00.000-04:002007-10-18T18:45:00.000-04:00These aluminium oxide nanospheres, that's funny. H...<I>These aluminium oxide nanospheres, that's funny. How comes that they are so round? And are these exhaust fume particles from the fuel? Aluminium in solid fuel? Or does the aluminium come form parts of the rocket engine?</I><BR/><BR/>Sorry for the long delay in answering this. I should know by heart the answers, especially since I was preparing for, and I made early this week, a short UK trip amaragrapshttps://www.blogger.com/profile/15769062084934190681noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8443136232582490822007-10-10T18:03:00.000-04:002007-10-10T18:03:00.000-04:00Hi changcho,thank you for the link - that's exctly...Hi changcho,<BR/><BR/><BR/>thank you for the link - that's exctly what I had been looking for :-)<BR/><BR/>In the meantime, I've located the confirmation of my registration to space-track in my junkmail folder and can accesse all the fancy TLEs - not that they are useful to me, but it's cool ;-). <BR/><BR/>But they don't have such a nice list of the "claims" along the equator, organized along stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-14680235674911691532007-10-10T17:45:00.000-04:002007-10-10T17:45:00.000-04:00"What I actually wanted to find out is, how many (..."What I actually wanted to find out is, how many (active and defunct) satellites are there in geostationary orbits?<BR/><BR/>Sorry, I forgot about this. The current number I have of operational GEO satellites is 350, exactly the number you estimated! The density of geo satellites is not uniform; as expected there are more over populated areas (i.e. over Asia, Europe and CONUS) and fewer over, Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-28104761355517947812007-10-06T03:02:00.000-04:002007-10-06T03:02:00.000-04:00Hi - Amara, thanks for the extra info. I haven't ...Hi - <BR/><BR/>Amara, thanks for the extra info. I haven't gotten to reading your paper yet but I'll do so when I have a bit of time.<BR/><BR/>Stefan - As far as the total number of geostationary satellites is concerned, I don't know off the top of my head but I'm sure there's a catalogue somewhere; I'll try to find out. Also, thanks for the link to the original A Clarke paper; I've never read Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33592079121820912182007-10-05T18:50:00.000-04:002007-10-05T18:50:00.000-04:00Hi changcho,I watched the Aurigids in 1-Sept of th...Hi changcho,<BR/><BR/><BR/><I>I watched the Aurigids in 1-Sept of this year for an hour and saw four satellites pass by (this is early a couple of hours before sunrise)!</I><BR/><BR/>Yeah, that was then similar to my experience, which was in the evening. I was really surprised that there were so many artifical lights up there ;-)<BR/><BR/><I>I helped to put Galaxy 16 in its proper geostationary stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86988997098274471562007-10-05T18:25:00.000-04:002007-10-05T18:25:00.000-04:00Dear Amara,thank you for the many informative deta...Dear Amara,<BR/><BR/><BR/>thank you for the many informative details about space debris and dust, and for the links to the ESA site! <BR/><BR/>These aluminium oxide nanospheres, that's funny. How comes that they are so round? And are these exhaust fume particles from the fuel? Aluminium in solid fuel? Or does the aluminium come form parts of the rocket engine? <BR/><BR/>And this dusty debris you stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66488325920818250792007-10-05T18:01:00.000-04:002007-10-05T18:01:00.000-04:00Dear all,coming back to Clarke and the geostationa...Dear all,<BR/><BR/><BR/>coming back to Clarke and the geostationary orbit - here is a <A HREF="http://www.lsi.usp.br/~rbianchi/clarke/ACC.ETRelays.html" REL="nofollow">link</A> to Arthur C. Clarke's paper "Extra Terrestrial Relays" in <I>Wireless World</I>, October 1945, pages 305-308... I came across it by chance on this page about <A HREF="http://www.satobs.org/geosats.html" REL="nofollow">stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69810354011813699092007-10-05T10:29:00.000-04:002007-10-05T10:29:00.000-04:00I was skygazing the other night and saw a couple o...I was skygazing the other night and saw a couple of bright flashes, like flashbulbs, and thought "what the Hell?" They were probably those iridium flares or something similar. Glad to know it wasn't aliens taking pictures. ;-)Rae Annhttps://www.blogger.com/profile/10239791074376508016noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86829604036480420562007-10-05T01:23:00.000-04:002007-10-05T01:23:00.000-04:00(K.D. Bunte conclusions)The orbital lifetimes of t...(K.D. Bunte conclusions)<BR/>The orbital lifetimes of the larger cloud particles (SRM slag, fragments) is greater than the orbital lifetimes of small particles (SRM dust). <BR/><BR/>SRM firing clouds of semi-synchronous orbit insertion burns do not survive the first orbit. <BR/><BR/>SRM firing clouds on GTO or GEO insertion burns generate long living large debris clouds. <BR/><BR/>LEO cloudsamaragrapshttps://www.blogger.com/profile/15769062084934190681noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59531916925746821282007-10-05T01:21:00.000-04:002007-10-05T01:21:00.000-04:00changcho: That paper is on the short side (it was ...changcho: That paper is on the short side (it was written to conform to this <A HREF="http://www.mpi-hd.mpg.de/dustgroup/~graps/dips2005/dipschapters.html" REL="nofollow"> Conference proceedings</A>. We are in the beginning of preparing a much longer paper of results. That work is one of the many output from one ESA contract: 16272/02/NL/EC, "Processing, Analysis and Interpretation of Data from amaragrapshttps://www.blogger.com/profile/15769062084934190681noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91935191721178549872007-10-04T20:39:00.000-04:002007-10-04T20:39:00.000-04:00Lastly, I wanted to emphasize: the launch of Sputn...Lastly, I wanted to emphasize: the launch of Sputnik was truly a revolutionary event in the history of humanity: slowly but surely we're starting to leave the cradle.<BR/><BR/>changchoAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-26768470167145496282007-10-04T20:30:00.000-04:002007-10-04T20:30:00.000-04:00Stefan - thanks for the interesting post. I watch...Stefan - thanks for the interesting post. I watched the Aurigids in 1-Sept of this year for an hour and saw four satellites pass by (this is early a couple of hours before sunrise)! <BR/><BR/>I have a subscription to Physics Today, but I have not yet read the mentioned article.<BR/><BR/>With respect to the interesting picture you posted. Sigh - I helped to put Galaxy 16 in its proper Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-23913593654101575952007-10-04T18:28:00.000-04:002007-10-04T18:28:00.000-04:00for 5 years until 2002. Scusi', I meant 7 years (i...<I>for 5 years until 2002.</I> <BR/><BR/>Scusi', I meant <I>7</I> years (it's a fantastic dataset).amaragrapshttps://www.blogger.com/profile/15769062084934190681noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2599531186350544222007-10-04T18:20:00.000-04:002007-10-04T18:20:00.000-04:00Dear Stefan, That Physics Today article was nice, ...Dear Stefan, That Physics Today article was nice, but I wished it would have mentioned <A HREF="http://www.esa.int/esaCP/SEMHDJXJD1E_FeatureWeek_0.html" REL="nofollow">ESA's historically long involvement in monitoring space debris</A>. One of the difficulties of the NASA studies is that their databases are classified (ESA's are not), so that poses an extra difficulty for people (my colleagues andamaragrapshttps://www.blogger.com/profile/15769062084934190681noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-14403881825329049012007-10-04T15:46:00.000-04:002007-10-04T15:46:00.000-04:00Hi Jonathan,thanks for reminding me of the Iridium...Hi Jonathan,<BR/><BR/>thanks for reminding me of the Iridium flares! <BR/><BR/>I've checked out flare events already several times at <A HREF="http://www.heavens-above.com/iridium.asp?Dur=7&lat=50.117&lng=8.683&loc=Frankfurt&alt=113&tz=CET" REL="nofollow">heavens above</A> (you have to make sure that your location is correct, since this is crucial to get correct direction and brightness etimates)stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-39599414084095377392007-10-04T15:10:00.000-04:002007-10-04T15:10:00.000-04:00It's interesting to read Sir Arthur C. Clark's rea...It's interesting to read Sir Arthur C. Clark's reactions to the fifty years of space exploration. He remains optimistic of space exploration's future despite some of the disappointments of the last half century.<BR/>Read the Q&A at<BR/><A HREF="http://spectrum.ieee.org/oct07/5584" REL="nofollow">http://spectrum.ieee.org/oct07/5584</A>Unknownhttps://www.blogger.com/profile/11781401986904200279noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-68826959326891722522007-10-04T12:18:00.000-04:002007-10-04T12:18:00.000-04:00If mankind were to abruptly end itself the most pe...If mankind were to abruptly end itself the most persistent markers of its past existence would be landfills and orbital debris - garbage. It's not much of an epitaph.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81929476181562037142007-10-04T05:03:00.000-04:002007-10-04T05:03:00.000-04:00Thanks to the Badastronomy blog I learned today ab...Thanks to the Badastronomy blog I learned today about Iridium flares (search for 'Satellite flare' at Wikipedia), coming from a set of satellites which can have up to -8 magnitude and be seen in the day. If you go to Heavens-above.com you can find out when these will be visible from where you are positioned.Anonymoushttps://www.blogger.com/profile/11667852535983804885noreply@blogger.com