Some readers have asked why we have yet to comment on the very interesting November 12 explosion at an Iranian missile facility (35°37’26.69″N, 50°52’23.88″E), as well as reports of another explosion near Isfahan. The short answer is that, despite a lot of research, I just don’t have anything interesting to add yet.
Sometimes, when that happens, it helps to simply ask questions. Robert Schmucker and Markus Schiller have been up to the same thing, and send along their list of preliminary thoughts and remaining questions:
On November 12, 2011, an explosion rocked an Iranian military facility just southwest of Tehran. Up to 20 military personnel are reported to have died in the blast, including a General who was regarded as a leading figure in the Iranian missile program.
A few days ago, Paul Brannan of ISIS published a short piece on the incident that also included satellite imagery of the site 10 days after the blast. Michael Elleman of IISS pointed us to this report and asked some very good questions, triggering our interest in the event.
Here are some of our findings so far. They are, of course, only preliminary and might still change with new information in the future.
– Compared to other solid-propulsion related facilities all over the world, this site is small.
– The satellite image was taken 10 days after the incident. The extent of any cleanup efforts during these 10 days is unknown, but it seems that much of the debris was already moved.
– The damage that is visible on the satellite image is massive. Even buildings 150 m away from the supposed center of the blast show severe damage.
– The damage pattern of an exploding solid rocket motor is known (for example the Pershing accident at Waldheide, Germany, 1985).
– This damage pattern looks more like a detonation than a solid propellant burn-off or explosion.
– The ground is charred at 3 different places.
– One of these places is right in the middle of a former building (in the very southwest of the image).
– The other two charred marks are located outside of former buildings, but close to them (slightly north of the first mark, and again north of that, on the northeastern corner of the former blue-roofed building in the northwest).
– The charred marks are large, at least 15 m in diameter.
– Composite propellants generally do not detonate – they are Class 1.3 explosives. Pure ammonium perchlorate might detonate under certain conditions.
– With a detonation of this size, one should expect crater(s), especially if the detonation(s) took place right on the ground (as with barrels filled with ammonium perchlorate, for example).
– No craters are visible on the available satellite image (only some debris that creates the impression of one or two craters).
– The roofs of high buildings in the distance are heavily damaged.
– Tall trees that were visible on the earlier image were affected, small trees and bushes seemingly not.
– When an important leader visits a facility like this, it is standard procedure not to do any dangerous activities that may potentially harm the visitor.The question now is: What really happened at this site on November 12?
Let me only add a list of possible reference incidents relating to solid-propellant rockets — the 1985 Pershing accident at Waldheide (US accounts use Heilbronn as a place name), the 1988 PEPCON disaster, and the 2003 VLS explosion in Brazil.
hass | December 6, 2011
Was this even a high-explosives facility, let alone a rocket testing facility? Where are the berms one would expect to have been built, to deflect potential explosions? No guard towers? No wall protection? No perimeter wall?
Allen Thomson | December 6, 2011
Well, it seems to have been associated with some fairly explosive material at least transiently. :-)
I’m as uncertain about this as anyone, but would point out that there’s a nearby facility at 35.628 N, 50.907 E that seems to have one of those tunnel-under-a-mountain features that’s accessed by roads with wide turns.
Also, I made an amateurish attempt to estimate the explosive power from the damage to the steel-frame buildings on the east side of the destroyed facility (looks like 2-4 PSI overpressure), assuming that the explosions took place on the west side. Numbers like 20 tons TNT equivalent came out, probably meaning 5-50 tons. It would be good if someone who actually has some expertise in forensic explosion reconstruction, such as the authors of the PEPCON report Jeffery references, were to weigh in.
George William Herbert | December 6, 2011
I also independently modeled the blast damage, as Allen did. There have been some private email threads on the incident.
My initial estimate gave something in the range of 5-25 tons of TNT equivalent energy. Location of the blast or blasts was not entirely clear.
To me – this sounds like the bulk detonation of the whole motor or first stage of a Sejil-sized IRBM. The explosive energy is about right, and while rare, solid motors can bulk detonate.
What might have caused such a detonation? Range of things… if it was an assembled missile, accidental detonation of the warhead might bulk detonate the upper stage which might bulk detonate the first stage. That could be as simple as a fire + non-insensitive warhead filler, or fuze failure, or some horrible industrial accident.
It’s a lot harder to bulk detonate motors by burning them. But not impossible. They’re designed not to do that…
I’m very slowly working up a statistical model, considering a grid of explosion hypocenter locations and explosion energy levels, and doing a statistical errors measurement for likely ranges of blast energy at the given building locations, to try and focus location and energy better.
I have the Cooper “Explosives Engineering” and various large blast modeling data from other sources, and have done large air blast work before. But it’s not my professional focus by any means.
Allen Thomson | December 6, 2011
To adduce a little more of the off-line conversation, the estimated size of the explosion is so large as to rule out drones, unless it was a lucky shot that set off something that already was at the facility. If one insists on an air-delivered weapon doing the damage all by itself, it would have to be something huge, like a BLU-82B “Daisy Cutter” or GBU-43/B MOAB. I think that’s pretty unlikely.
Galen Wright | December 6, 2011
Hass:
The small facility featured in the ISIS imagery is not the only ‘missile-related’ facility in the area. Most of the missing features you mention can be found spread out across the greater-area is some form or another; the rocket testing sites I mention below do have the protective berms and observation buildings and there are also a good number of security perimeters and entry-control-points elsewhere (and, to be sure, there is one in the compound in question that was built sometime between 2007 and 2009).
About 2.5 km north of the above-mentioned compound is some sort of industrial facility with hardened shelters and earthen revetments. Then there’s the area which Allen mentions and does indeed appear to have an extensive underground facility. Notably, if you go back in time in Google Earth, it shows that one of the “sheds” on the southern side of the mountain is actually a second entrance.
About 13-15 km to the south-east are two garrisons, that as-far-as-I-can-tell, are “artillery groups”, which is the Iranian equivalent to an artillery support brigade. I cant say for sure but I’d bet this includes the IRGCs missile units, whether they are the larger ballistic missiles like the Shahab-3, or the smaller artillery rockets like the Zelzal.
Right about the time that the facility in question was entering a surge in construction (2007+), a static rocket testing site was built about 1.7 km south of it, with a road connecting them. There’s also a second test site about 6 km south of this, with more industrial buildings. It’s also worth noting that in the latter compound there are redundant security perimeters around specific clusters of buildings which points to a high level of security.
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Allen:
Like you, I only have an amateurs perspective, but I concur with your analysis. Judging from what we know about IRGC “industrial buildings” used to produce military goods (knowledge gleaned from photo ops in arms factories) I think that the buildings in question are probably comparable to ‘brick housing’ or ‘commercial buildings’ which I’ve seen rated at 10 psi. Construction is usually something like brick and mortar walls, with a frame of steel girders. For an example of this type, check out this piece from ‘Uskowi on Iran’ on the production of IRGC speed-boats in Bandar Abbas: http://tinyurl.com/IRGCBaAb
The two buildings closest to the blast but which still managed to survive it don’t appear to have sustained overly significant structural damage from the pressure wave (falling debris is another matter). The shadows cast by the metal girders which comprised the buildings frame indicate that they’re still standing; only the thin skin covering the roof and top portion of the walls was destroyed.
Interestingly, the two low, white buildings that were situated in-between the soccer pitch and the now-demolished blue-roofed building. Neither of these two buildings had the look of a factory (for instance, they’re both bordered by rows of trees, and adjacent to a grassy field). The southern-most building has been completely demolished which indicates that it sustained at least enough damage in the initial explosion to require razing the subsequent cleanup effort. The northern building has at least one portion still standing but has still suffered significant damage considering its relative distance from the blast
George William Herbert | December 6, 2011
Galen writes:
The northern metal-roofed building in the central column (west, central, east) does in fact show significant distortion of the side and roof girders on the side facing what I presume is the blast area, north and west of it. You can see it a bit on the ISIS report image and better on the source satellite image, which I was provided offline.
The metal-roof industrial buildings are, I think, metal sheet walls not brick or concrete, but I don’t know for sure. Most of those types of buildings tend to use the concrete or brick walls for column strength; you can see shadows of steel columns under damaged roof areas, as well as roof girders. One does sometimes see steel columns inside brick or concrete walls, but it’s unusual in my experience (which, to be clear, has no particular insight into Iranian construction trends…).
Galen Wright | December 6, 2011
Re: George
The ISIS image quality does leave something to be desired; I’ve been using this image from the BBC which has a higher resolution and a nifty timeline feature. I don’t know if it’s as good as what you have but it’s the best I could find.
http://www.bbc.co.uk/news/world-middle-east-15960456
Looking again, I can see what you mean when you talk about the distortion of the steel girders. In a similar vein, the same structure also has noticeably more damage to its northern wall then the southern-most building in the central column, or either of the two buildings in the eastern column. What’s noteworthy about this IMO is that the other two buildings appeared to suffer damage to the top levels of the wall, but not the lower half. I’m making this judgment based off of the sunlight you can see coming in through the top of the shadows in-between the ‘fingers’ of the vertical girders that held up the roof
I’ve been looking through my collection of photos of military-industrial buildings in Iran that might be comparable and with a handful of exceptions the majority are constructed with a frame of steel I-beams (or, in some cases, reinforced concrete columns), walls composed in part, or entirely of brick (though I couldn’t say if these would qualify as “reinforced” or not), the roof and remaining portions of the wall is usually a light covering of sheet metal and/or glass and/or plastic over ribs of girders. Here are two of the better examples I’ve been able to glean from my collection that should illustrate what I mean:
1) This shows one variation of composite wall construction with both brick and glass/metal.
http://tinyurl.com/SPA-Factory
2)This time, with the full-brick.
http://tinyurl.com/ASCM-Factory
Beyond being a purely pedantic distinction, I think that if these buildings were indeed constructed this way then these differences could function as ad-hoc rupture disks in helping to narrow down the range of PSIs involved. Namely, since the pressure wave at the northern building in the middle column was high enough to warp steel I-beams and knock down brick walls – maybe 7-10 psi at this location? In contrast, the buildings to the south and east only suffered damage to their roofs and areas where lighter materials would be used while the lower portion of the wall (presumably, brick) remained intact – perhaps <5 psi?
I have to qualify this by saying that this is based on a number of assumptions which may or may not be true. For instance, the fact that only the top portion of the wall appears to be undamaged may be due to the fact that other, unseen obstructions are blocking the path of the sun, creation this illusion. Alternately, the unique damage pattern may have been created by falling debris, not overpressure. In other words, feel free to tear this hypothesis apart.
:)
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On an unrelated note, can anyone identify the "tall trees" that Schumacker and Schiller are referencing? This may be another case of only being able to tell with a certain image quality. The ones to the south-west of the soccer pitch look like they might be on their side but I can't say it with any degree of certainty.
P | December 7, 2011
To get a better idea of what the satellite pictures can tell us about what blew up it might be useful to compare the images with those of other cases of large explosions at military or industrial sites, not just with other cases of exploding missiles.
For example, earlier this year in Cyprus a warehouse with confiscated Iranian ammunition blew up. A very useful before and after image of this event is provided at http://robotpig.net/extras/cyprus_zygi/
George William Herbert | December 7, 2011
Zygi was reportedly up to 2,000 tons of explosive materials, vs something like 20 in this case (I estimate). The 98 “metal cannisters” I think were 98 standard international shipping containers full. It’s not clear how much of that weight was actual explosive vs shipping material, casing, etc.
That said, it was 300 meters from the explosion point at Zygi to the main power station building, which shows similar damage to the south-central building at Bid Kaneh. That was about 97 meters from the corner of the northwest metal roof building at Bid Kaneh to the south-central one.
X | December 7, 2011
Metal buildings are commonly used when testing propellant mixtures because there is less chance of stray static electrical sparking. I remember when United Technologies was testing rocket motors for the Shuttle Boosters, they were mixing nitroglycerin with aluminum powder plus a plasticizer. Some of the early tests were deadly to the technicians but little by little they lowered the explosive power until they achieved a perfect mix that had the highest potential energy and the best relative safety. I suspect this was a propellant mixing area rather than a rocket manufacturing facility but this would not account for a blast that seems to be above ground level rather than at ground level. Therefore I tend to believe that the blast was initiated above ground level by some unknown entity to destroy a propellant mixing facility while a General was visiting.
Andy | December 10, 2011
ISIS has imagery and analysis of the apparent blast near Isfahan.
DJH | December 14, 2011
Article from Jordanian press concerning assassination attempt on Khanenei might be tied in:
http://www.albawaba.com/news/sources-plan-kill-iran-supreme-leader-thwarted-405257