A dog leg is a quite ambitious in the face of having no experience of controlling something in orbit. If we take Iran's efforts as an example, don't be surprised if "500 km, sun-synchronous" turns out to be 200 x 500 km, 90°. I vote with Jonathan's hypothesis 3. Bob Christy On 08/04/2012 14:44, Jonathan McDowell wrote: > > I am wondering if "Unha-3" means "3-stage Unha", not "3rd Unha". > Consider a scenario in which stage 2 is injected over North Korea at 150 > km with an inertial velocity of 7.0 km/s and an inertial azimuth of 178 > deg (rotating frame azimuth of 181 deg as required by the NOTAMs). It > then reaches a -2350 x 500 km x 88 deg orbit, with apogee over the > equator at 123E > > Then suppose the payload and a third stage are yawed by 50 degrees and > make a 1.6 km/s burn. For a third stage empty mass of 50 kg (say) > and a satellite of 100 kg, and a solid motor of Isp = 250 s, > this would require 150 kg of prop for a total upper composite mass > of 300 kg. Is that outside the 2-stage Unha's performance? > If I were NK, this is absolutely how I would attempt to launch > a sun-sync satellite - it's very similar to the strategy used > by some early US Delta launches. A lower stage dogleg is not required. > > So Ted, I think you are premature in your conclusions. I see four scenarios: > > 1. - Ted's scenario in which the NK are flat out lying. Certainly possible > but I don't think this is the most likely explanation. > 2. - My scenario in which a third stage equatorial dogleg achieves sun-sync. > 3. - Translation confusion somewhere along the chain where "polar orbit" > and "sun-sync" orbit have been conflated because some poor translator thought > that "sun-sync" sounded more technical and impressive - the two concepts > almost always go together these days since ninety-something percent of > modern polar orbit satellites are sun-synch. > 4. - Lying somewhere else along the chain. For example, > the vice director of the Space Development Department is a non-technical > party appointee who has ordered his engineers to launch a sun sync satellite, > and his scared engineers are lying to him and hoping that he won't notice > the difference, or will forgive them if they at least get a satellite up.... > > > > - Jonathan > > _______________________________________________ > Seesat-l mailing list > http://mailman.satobs.org/mailman/listinfo/seesat-l > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2012.0.1913 / Virus Database: 2411/4922 - Release Date: 04/08/12 > > _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
This archive was generated by hypermail 2b29 : Sun Apr 08 2012 - 14:31:05 UTC