RE: North Korea satellite: NOTAMs inconsistent with claimed sun-synchronous orbit

jcm@head.cfa.harvard.edu

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

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