One of the best things about this damned blog is that really great people will send me little bits of analysis — short pieces that could never make the Washington Post but are totally awesome nonetheless.
Case-in-point: Friend of Wonk and former UNMOVIC inspector Geoff Forden. Forden observed a little bit of debris popping off a Shahab-3 during a February 4 test and concludes that Iran might be having a hard time producing graphite jet vanes:
Iran’s February 4th launch of a Shahab-3 just keeps on getting more and more interesting; that is if you are interested in just how good of a missile the Shahab/No’dong is. Video from Iran’s television show that there is a failure of the missile’s thrust vector control system nineteen seconds into its powered flight. At that point, there is a brief flaring at the very end of the missile and an object is seen flying off for several seconds, until it leaves the video’s frame as the camera continues to follow the missile. Tellingly, it doesn’t just drop off the missile but is given quite a transverse boost.
What is happening? The most likely explanation is that a part of one of the graphite jet vanes, little fins that are stuck into the exhaust just outside the nozzle and are used to steer the missile both in its pitch program and to correct for unwanted deviations in its trajectory. Jet vanes must be manufactured from very hard and pure graphite otherwise it is subject to being “eaten” away by the corrosive effects of the exhaust. Nineteen seconds is also about the time that a No’dong missile might be just starting its pitch program. (As I watch the video, it appears to me that the Shahab-3 has just started its pitch-over program, though why a sounding rocket needs to pitch over is beyond me. But then again, I don’t understand why Iran would use a nosecone for scientific purposes that looks exactly like the combat warhead.)
Clearly, the failure was not enough to cause a fatal instability, such as a veering off course that might trigger an automatic self-destruct charge. SCUDs are known to have just such charges on them for range-safety purposes even during combat operations so that there is reason to suspect that a Shahab-3 being used as a sounding rocket would too. Presumably, just a piece of a jet vane flaked off but still left enough to help steer the missile and, perhaps more importantly, enough “drag” in the exhaust stream to balance its opposite number. In fact, this is where the story gets interesting: it is very reminiscent of a Syrian test of a so-called SCUD-D variant that crashed in Turkey when it was aimed almost ninety degrees away, to a point in the Mediterranean just to the east of Cyprus.
In that test, in May 2005, pieces from a Syrian SCUD-D rained down on the Turkish towns of Golbasi and Mahmutlu. The most likely explanation for that failure has always seemed to me to be associated with a failure of the jet vanes but one so catastrophic that it veered off course, triggering the self-destruct mechanism as it picked up an unwanted lateral acceleration. After all, the drag from the jet vanes in a SCUD waste about 5% of the missile’s thrust. If you eliminate one of them, it could create quite a torque that might very well force the missile to veer off in the direction opposite the missile vane.
So what does this mean for missile proliferators in general and Syria and Iran (and North Korea since they are all involved in the development of these missiles) in particular? It means that they are still having a hard time producing graphite tough and pure enough to be used in large missiles. It also indicates that a top priority for their missile engineers will be to develop other thrust vector control mechanisms.
You earned yourself a brewski with this one, buddy.