Observations of a Missile Launch – I

Much discussion and analysis (or what some try to pass off as analysis) in the ‘verse.  Many, most in fact, are focused on the specifics of the failure and potential threat to the US.  But there is more to this than meets the (media) eye, so let’s break it down here.  We’ll break this into several parts – the missile, launch and implications thereof, responses from the US and regional allies/partners and what are the future implications.  These will be spread over the next few posts.

The Taepo dong -2 (TD-2, alternately labeled the Unha-2 SLV) that was the object of concern is a three stage, indigenously developed, long-range missile purported to be a Space Launch Vehicle (SLV) but which also, by default, bears much resemblance to early ICBMs.  There isn’t much publically, or open-sourced available on the specifics of the vehicle, but there has been some fairly sophisticated supposition and conjecture based on known factors of indigenous North Korean capabilities and assistance or cooperative development with other countries like Iran, Syria, China and Russia, officially and not.
So – what do we know?  We know that it was a three-stage vehicle, with the first stage consisting of a cluster of four engines – most likely derived from the No Dong which itself is evolved from the SCUD B.  Clustering is an economically and effective means of gaining greater power for a booster stage with a wealth of experience available from around the world (a good example is found in the early days of the US space program with the use of eight Redstone tanks for LOX and RP-1 storage teamed with eight H-1 engines drawn from the Thor-Delta rockets of the period in building the first stage of the Saturn I).     It was probably fueled with a combination of nitric acid (RFNA) as the oxidizer and kerosene as the fuel, again similar to the SCUD.

There are certain advantages in this combination, not the least of which is long/close familiarity with handling it from similarly long association with the SCUD.  Disadvantages though, include the fact it is less energy dense than, say, a nitrogen tetroxide/UDMH  (unsymmetrical dimethylhydrazine) combo that is less corrosive on the equipment, more energy dense (providing greater initial impulse and thus able to generate more thrust to lift more payload).  Comparing imagery released today from North Korea TV (illustration 1 – TD-2 images from NHK), it appears the flame characteristic tends towards RFNA/kero – old tech.

Implications that carries for the booster design point to a less advanced base model for use as an ICBM than if a hypergolic mix of N2O4/UDMH had been used.  To be sure, the early US ICBMs used non-storable liquid fuels (LOX/Kerosene or RP-1 typically), which impacted their availability/readiness.  Additionally, it could force design compromises in the airframe in an attempt to lighten and/or force more propellant volume to offset the lesser potential energy of this combination.  Likewise, the second stage, presumed to be a No dong would similarly be RFNA/Kero while the third stage, one of the new items in this iteration may well have been derived from the Iranian Safir and used UDMH as that is the preferred propellant for exoatmospheric stages.  By appearance, beginning with the payload shroud and presumed length it appears to be a match with the Safir upper stage.

Finally, the other major thing that is apparent about this design is the lack of aerodynamic control fins, indicating directional control is likely provided by thrust vanes, gimbaled engines or vernier jets. The first and last are the more likely as gimbaled engines imply a great(er) degree of complexity and design sophistication than is supported by observations of the rest of the missile.

So – all of this together seems to indicate a missile of rather basic design with some interesting tweaks along the way (vernier jet or exhaust vane control, for example) in a package that in and of itself would not be a weapon, but one that could serve as a prototype to develop the necessary key elements – staging, guidance, throw weight, warhead, should it prove successful in a demonstration space launch.

Was it sucessful?  It depends…we’ll look at the flight in the next post and some interesting nuances that stem from the larger result.