If there had been a SERIES of tests (with a perhaps a few failing shortly after launch, hence a video clip of the successful launch only) then in my opinion that would support the idea that the Iranians have developed, and tested, a substantial improvement in their rocketry.

http://www.b14643.de/Spacerockets_1/Diverse/Dong-Feng/DF-15C_3.jpg

Clearly, they’re not identical, but some similarities are apparent.

(Besides, at the moment i’m rather occupied with debunking this ‘Liliput-Scud’-rumor…)

You’re right that for short-range missiles the fins can be useful to orient the missile during reentry. I was thinking here of a missile of range 500 km or longer and assuming the aerodynamic forces are high enough at that range to break off the body even if oriented–so I was assuming a separating warhead. It’s possible that an oriented body at 500 km range might not be torn off, but it would above something like this range. It would be interesting to look at this in more detail.

Nonetheless i also agree with Geoff: In case of the Scud (and other single-staged missiles without warhead-separation), the fins are ALSO vital for reentry (of course, they don’t work without an atmosphere – that’s why they’re not used on upper stages that won’t see any air during operation, like in case of the DF-4).
The need for non-active directional alignment (aka aerodynamic stability) also typically dictates the form/mass distribution of separated reentry-vehicles – thus they often have small fins or a mostly empty (or at least lightweight) conical section at the rear (like in case of the “triconic” RV – or even the Minuteman’s Mk.11).

Also, don’t forget that there are missiles WITH a separating warhead AND fins out there, too (like the DF-3, or the DF-2/R-5M, or the DF-1/R-2, or the R-12, or the R-13, or the R-14, or the Nodong-A etc. etc. etc.)…

I can only ask myself how somebody can interpret an unarticulated spot in a blurry video stillframe as a “steering nozzle” (wishful thinking?). There are MUCH better images of the “triconic” RV available by now (e.g. from the september-parades of Ghadr-1 or Sejil) – and it is clear that there is no such steering nozzle (it’s most likely an explosive bolt for warhead separation – which tells us something about the anchorage of that warhead, as well as that the ‘end conus’ of the RV is hollow on the inside, which also corresponds well to aerodynamic requirements)!

Whether you can use a guidance system without fins to stabilize a missile early in flight depends on how good the guidance system is – how good it is at sensing changes in the orientation of the missile and how quickly it can respond. The extra stability added by the fins significantly reduces the speed at which the guidance system needs to be able to react.

Clearly unguided missiles (even model rockets) need fins for stabilization during launch. Missiles with advanced guidance systems, like U.S. ICBMs, clearly don’t. Someplace between those two is a point at which the guidance system is good enough to get rid of the fins. The fact that the Chinese DF-4 still has fins suggests to me that Scud needs them for stabilization during boost, and this agrees with this excerpt from the Pentagon’s MTCL below.

I agree with Schmucker and Schiller’s idea that Iran is testing a better guidance system, but still with jet-vanes. As I said in my post, they may be doing this guidance outside the missile.

David

Militarily Critical Technologies List (MCTL) (September 1998), Part II: Weapons of Mass Destruction Technologies
(http://www.fas.org/irp/threat/mctl98-2/index.html), pg. II-1-7:

“The aerodynamic and inertial properties of the missile and the nature of the atmospheric conditions through which it flies determine the speed with which guidance commands need to be sent to the control system. First generation TBMs, such as the SCUD and the Redstone, have fins to damp out in-flight perturbations. The rudimentary guidance systems used in these missiles do not support rapid calculations of position changes. When a missile’s thrust vector control system becomes responsive enough to overcome these perturbations without aerodynamic control surfaces, these fins are usually removed from the design because their added weight and aerodynamic drag diminish the missile’s range.

“Most TBM designs have a resonance around 10 Hz (cycle time of 100 milliseconds. Calculations to correct disturbances must occur within this cycle time. Guidance and control engineers generally add a factor of safety of two to their cycle time or, in other words, half the cycle time. When thrust vectoring is the exclusive control standard of a missile, the system must respond or have a major cycle time of 50 milliseconds or less. When fins are used, the control cycle time for a missile may be much longer than a second.”

http://a.imageshack.us/img833/8306/shahabnoz.jpg