Iran’s solid-propellant SLV program is alive and kicking

If you are a friend of the blog, you might have heard of Iran’s program to develop a solid propellant space launcher, the relationship of the space launch program to Iran’s missile ambitions and the 2011 explosion that wiped out most of the personnel associated with it. To make a long story short, at some point in the mid-2000s, the founding father of Iran’s missile program, Hassan Tehrani Moghaddam —  frustrated with both the Supreme Leader’s 2,000 km range limit and the slow bureaucratic apparatus of Iran’s missile industry – decided to set up an institutionally separate development effort for a solid propellant space launch vehicle that would also serve as a hedging strategy to acquire long-range missile technology. This move was surely aided by his close ties to Khamenei. Unlike Iran’s well publicized liquid-fuel space program, Moghaddam’s project proceeded in complete secrecy until a large explosion killed Moghaddam and obliterated the Bidganeh site in 2011. Thanks to the hundreds of tiny puzzle pieces released over the years, we managed to reconstruct much of the history of this program. However, the most important question of all remained unanswered. Did the program die with Moghaddam or did it survive?

New information suggests that the program is both very much alive and that it remains under the control of the IRGC’s Jihad Self-Sufficiency Organization.  This is in an important development.  While much of the concern about Iran’s current liquid-propellant space launch program is misguided, the development of a solid-propellant space launcher by the IRGC would raise much greater concerns about the long-term sustainability of Iran’s commitment to limit the range of Iran’s ballistic missiles to less than 2,000 km.

Shahroud Missile/Rocket Development Facility

The first clue that Iran’s dreams for a solid-fuel space launch vehicle are still alive lies within the perimeters of Iran’s Shahroud facilty at which solid motor testing has steadily picked up pace over the recent years.

Originally built in 2010 and gradually expanded ever since, the site features facilities for the production and testing of solid-propellant rocket motors and what looks a lot like a launch pad. (Arguing whether it is a launch pad or a vertical engine test stand or both is one of Jeffrey and my favorite past times).  In short, everything you would expect from a site dedicated to a solid-fuel space program. The fact that buildings were painted in Moghaddam’s trademark color blue and that a photograph showed Moghaddam feasting next to a box marked ‘Shahroud’ deepened our suspicions that the facility was related to his program.

While many parts of the facility feature interesting activity observable from space, the most intriguing site is the facility’s motor testing area. Located in a scenic and slightly Blofeldian mountain crater, the installation features a total of five horizontal stands for the testing of solid propellant motors.

The basic design of Iran’s horizontal test stands is pretty straightforward. The usually rail-mounted motor sits a on top of a large L-shaped concrete block that absorbs the thrust of the motor during test firings while a load cell installed between the motor and the block measures just how much thrust it generates.

Fortunately for analysts, horizontal motor testing tends to leave behind large candle plume shaped scorch marks that are easily observable from space In combination with high-cadence satellite imagery this allows us to understand when exactly a test stand was used for the first time. Somewhat surprisingly, Shahroud’s test stands sat idle for almost five years after their construction. Then, between April and May 2016, the first motor test took place in Shahroud, followed by a larger test stand being introduced into service in June 2017. Finally, the site’s second largest test stand was used in March 2019 but left only a small mark ground, perhaps indicating a failed test. In November 2019, a new motor test happened at test stand number three, this time resulting in a substantial scorch mark.

Scorch marks appearing next to Shahroud’s test stand 3

A quick 3D reconstruction of the test stands based on satellite photo measurements indicates that over the last years has been moving towards using successively larger test stands.

Overview of Shahroud test stands with date of first use
Test stand 3, first used in November 2019

The 3D reconstruction makes clear that some of the test stands at the site are surprisingly large. It is entirely feasible that the Iranians have only tested smaller motors and did not care about test stands being oversized for the mission. However, there is also the possibility that Iran has already moved towards testing larger diameter motors.

One can roughly approximate the maximum thrust of an engine that can be tested on a particular stand based on how heavy the concrete block is. As a general rule, the block is usually 4-6 times heavier than the thrust produced by the engine. Using satellite measurements and the average weight of concrete for our calculation, one arrives at the following results:

Even though this is a very rough estimate ignoring a lot of unknowns (internal structure, thrust absorbed by the mountain slopes the test stands are attached to) it does show Shahroud’s test stands are capable of handling solid motors much more powerful than the ones currently in Iran’s arsenal.

The Salman Motor

While satellite images showed that solid motor testing was accelerating, we were still left in the dark about what exactly Iran was working on in Shahroud. That is until last Sunday. 

For almost a decade after Shahroud’s construction, Iran not only never released ground imagery of the site, but never even acknowledged its existence, save for the occasional article in Israeli style (‘Western observers have said that’). So it was quite a surprise when on February 9, Iran released footage of the country’s new Salman rocket motor undergoing testing within the crater lair.

IRIB footage of the Salman solid motor undergoing testing at test stand 2
The same spot in a reconstruction of the crater using David LaBoon’s elevation map

In a press conference, IRGC commander Hossein Salami and IRGC Aerospace Force commander Amir Ali Hajizadeh revealed that the motor tested in the footage was a smaller solid upper stage motor for space applications called Salman.

While the Salman’s unveiling was somewhat overshadowed by the failed launch of Iran’s Zafar satellite, the motor is worth paying attention to for a number of reasons.

First, the Salman uses carbon fiber composite casing that is much lighter than a traditional steel motor casing. Iranian TV also published a short glimpse into their production facility for carbon fiber motor casings.  (The casings in the image are for the smaller Raad 500 short-range ballistic missile that was also revealed at the press conference.)

Second, the motor has a flexible nozzle for thrust vectoring.  Guiding a rocket using thrust vector control (TVC) is a first for Iran, as all previously observed Iranian solid propellant missiles had used either aerodynamic control surfaces or jet vanes for flight control. To preempt observers from reverting to the ‘it’s only a model’ line, the county also released close-up footage of the mechanism in action.

While the Salman is a dedicated motor for space applications, Hajizadeh also briefly elaborated the military applications of this technology.

Yet, Hajizadeh left out the most interesting military application of tilting nozzles – long-range missile development. TVC is an important technology for large solid propellant motors as jet vanes become infeasible for larger motor diameters, higher thrusts and longer burn-times.

Solid is back

Hajizadeh’s claim that the Salman represented Iran’s entry into the solid-fuel SLV field is not the only indication that Iran’s solid SLV dreams are still going strong. The same day Salman was unveiled, Mehr News reported that the design of the solid-propellant Zuljanah SLV had been completed and that it would be used to launch the Nahid 1 satellite as early as June 2020.

Both the unveiling of the Salman and Mehr’s announcement leave little doubt that Moghaddam’s solid fuel space ambitions survived the death of its charismatic, yet somewhat eccentric leader. But how about its institutional structure?

Still a parallel program?

Frustrated by the slow development policy and bureaucratic hurdles, Moghaddam had set up his own development effort run by a murky organization called the IRGC Self-Sufficiency Jihad organizations.  IRGC-ASF deputy Musavi confirmed in 2014 that the program was running in parallel to the liquid-fuel space launch vehicle development controlled by Iran’s Aerospace Industry Organization (AIO). The IRGC-SSJO ran the Bidganeh solid-propellant motor development site and save a few external contractors, the majority of the team members killed in 2011 were IRGC members. Thus while it might be unlikely that every single component of the Ghaem project would be developed by the parallel institutional structure, at least motor development seems to have been firmly in the hands of the IRGC.

The first clue that what happens at Shahroud is different from Iran’s other development efforts is offered by the veil of secrecy that surrounds the site or at least did so until a few days ago. While the AIO’s flurry of sub-companies regularly shows up on the project lists of contractors installing everything from electrical equipment to ventilation systems, Shahroud remains a black hole. A group of environmentalists working on the preservation of the Asiatic Cheetah in Khar Turan National Park where the Shahroud site is located was arrested and sentenced to draconian prison sentences for allegedly spying on the country’s missile program.

Then there is the Salman motor itself proudly displaying an IRGC logo on both the version tested as well as the one exhibited. While it is well known that the IRGC operates Iran’s ballistic missile fleet, seeing a prominent IRGC logo on anything related to Iran’s space program is highly unusual. And think about it, if you were an IRGC guy working on amazing solid space motors for years in total secrecy while your mediocre liquid fuel colleagues couldn’t stop bragging about the Simorgh at the bar Friday prayers, wouldn’t you think it’s about time you get a little credit?

IRGC logos seen on the Salman and at the carbon fiber motor casing production site

Nomenclature is another interesting indication that Iran’s space program is not as homogeneous as one might think. Take a quick look at the names of various items associated with the liquid and the solid propellant space program and see whether you can spot the difference.

In the liquid fuel program and items associated with it (such as the small upper stage solid motor Arash) neutral names and names derived from Persian mythology dominate, while all known designations of solid-propellant space systems are associated with Shia Islam.


More than eight years after the death of Hassan Tehrani Moghaddam, Iran’s solid-propellant SLV program is still going strong and it looks a lot like its motor development it’s still run by the guys with the green baseball caps. Moreover, by demonstrating the production of carbon fiber motor casings and tilting nozzles for thrust vector controls, Iran has demonstrated that, at least on a smaller scale, it now masters two sophisticated core technologies highly useful for both solid SLVs and longer range missile development. Whether Iranian engineers have already managed to scale up both technologies for use in larger motors is anyone’s guess.

Analysts like Mike Elleman have rightly pointed out that US concerns that Iran’s liquid fuel space program might be mere cover for ICBM development are exaggerated. Even if Iran would go ahead and reconfigure the Simorgh with new upper stages to serve as a potential ICBM, the result would be a large, clumsy, and immobile system that would be a sitting duck for American air power in any potential conflict.

A revitalized IRGC-run solid fuel space program though, would be different kettle of fish.