Wisconsin Project Interview with Uzi Rubin on Iran's Missile Program

Interview Series
September 17, 2009

Publication Type: 

  • Interviews and Podcasts

Weapon Program: 

  • Missile

Mr. Uzi Rubin, an Israeli engineer who formerly ran Israel's "Arrow" program for missile defense, gives high marks to Iran's recent success in making long-range missiles, and predicts that Iran would use these missiles in saturation attacks with high explosives in time of war.


In a recent interview with Iran Watch, Mr. Rubin emphasized that Iran successfully developed the design for both its solid-fuel ballistic missile and its liquid-fuel space launcher after only a few test flights, showing that the Iran's missile industry is capable of recovering from test failures in relatively short time.

Mr. Rubin believes Iran largely has the capability to build longer range missiles. He predicts that Iran will focus increasingly on solid fuel technology, which is easier to scale up in order to reach longer ranges. However, for political reasons, Iran is playing down this capability for fear of alienating Europe and Russia. With a range of 2,000 km, Iran's two-stage, solid fuel Sejil [and variants] can already reach all Mid-Eastern targets from eastern Iran.

The following is an edited transcript of our conversation.

Iran Watch (IW): What do you think about Iran's space program, and the recent rocket tests?

Uzi Rubin (UR): I was impressed by the space launcher, especially its design. The first stage is a souped-up Shahab 3. The second stage is liquid fuel, but it's storable liquid fuel. This is one step beyond basic, non-storable liquid fuel like what's used in Scuds. And it's not only storable, it's also hypergolic. That means you don't have to light the propellant, you just pump it into the motor and it spontaneously ignites. Iran managed to design a very elegant second stage - and also very light. The overwhelming majority of countries starting out with space launch technology started with three stages. Why? Because it's easier to reach orbital velocity with three stages than with two stages. Doing it with only two stages places very stringent requirements on the second stage. But Iran did it. Everyone was surprised. This is something we didn't expect. I'd say it was an audacious achievement for a starting country.

IW: Were you surprised that Iran had mastered staging? Staging is not easy.

UR: Well, staging is challenging, but I'm not surprised. When Iran announced its space program back in 1998, this obviously meant they were going to rely on staging. So I wasn't surprised that they did it. Staging is key to a space program. I was surprised that it worked so well the first time.

I was also surprised that Iran progressed so quickly. In February 2008, Iran fired a missile it called Kavoshgar, which was a Shahab-3, probably with a slightly stronger motor and painted in blue and white because it was flown by the space agency, not by the military. It had a typical triconic front end - what's called the baby bottle front end - but with some changes. This test flight showed all the signs of failure. I tracked the video frame by frame. You could see pieces falling off while it was taking off, and then the whole thing exploded violently. That was the first launch. Iran claimed the test was successful, but we saw it as a dismal failure. Six months later, in August, Iran fired its first space launcher [Safir]. No pieces fell off. That indicates ample telemetry data from the failed test, which allowed Iranian engineers to figure out what went wrong in February. They than displayed good engineering: they fixed the problem. Finally, the short recovery time - only six months - indicates vigorous program management. While Iran's regime is radical and belligerent, and the success of its endeavors is bad news for the Middle East and the international community - as an engineer, I take my hat off.

But the August test was still a failure. Six months after that, in February 2009, the rocket worked. Within one year Iran had moved from a failed design to a successful one and launched a satellite into good, stable orbit. Again, this progress is a sign of good system engineering and good program management. Both are crucial. Not the technology. You can acquire technology. The Missile Technology Control Regime (MTRC) appears to be dysfunctional as far as Iran is concerned. They seem be able to buy anything from anywhere. Perhaps not from the United States, and there may be some difficulties in Europe. But they apparently have other venues for acquisition of missile related materials and components. .

IW: Is this space launcher an indigenous design?

UR: I am not sure. But look, even if somebody designed it for Iran, if Iran had access to this design, then it's like having the design capability at home. The legacy for the overall design is Soviet. But when I say Soviet, it doesn't mean Russian.

I think the Iranians have taken off. They have learned what they were taught and are proceeding.

IW: Could Iran's success depend on technical assistance received remotely, from experts who are not physically present in Iran?

UR: No, to support a program you have to be there physically to communicate face to face with the technical teams. It's my guess that what we are seeing is already largely indigenous Iranian capability. They're developing a technological culture, which is unique in the Middle East. They're adapting science as part of their national policy. Iran hosts aerospace conferences, once or twice a year, and Iranian engineers contribute papers to American conferences. So, Iran is developing a strong scientific base.

Iran's missile program is now 20 years old. There has been enough time to graduate a number of engineers from Iranian universities. Those who graduated 15-20 years ago are now program leaders.

IW: Is Iran ahead of North Korea?

UR: So it would seem. In addition to the space launcher's liquid fuel technology, Iran also has a solid propellant missile: the Sejil, or Ashura or Sejil 2. Iran changes the names, but that's just psychology. It's the same missile. In 2005, Iran's defense minister made a statement claiming to have made a solid propellant rocket motor for the Shahab missile. Obviously what he meant was that Iran was working on solid propellant rockets with the diameter of the Shahab. Thirty months later, the first Iranian solid propellant, two-stage ballistic missile made its first flight.

The solid fuel missile is a breakthrough, because it gives Iran a growth potential that it didn't have with liquid fuel rockets. In liquid rockets, there are difficulties in making rocket motors that are large enough but still stable. When you increase the combustion chamber of a liquid fuel motor, you can get severe combustion instability problems. With solid fuel, once you have a breakthrough and you can make rocket motors, increasing their size is pretty straightforward.

IW: What is the diameter of the current solid fuel missile?

UR: The same as the diameter as the liquid fuel missile: 1.25 meters.

The most important dimension of a missile is its diameter. The production line is geared to this diameter. If you change the diameter of a missile by even by a couple of inches, you have to redo much of your infrastructure. So, once you have a diameter you stick to it. This is especially true for missiles on mobile launchers, because if you change the diameter, you have to make significant changes to the launcher as well. So, the diameter of Iran's solid fuel missile is 1.25 meters, which is the same as the space launcher and the same as the Shahab-3 missile. This diameter was inherited from North Korea. The North Koreans did the trick of enlarging, or scaling up the Scud. So it makes sense that the solid fuel missile has the diameter of the Shahab, which came from North Korea, and of the launcher of the Shahab, slightly adapted, and that it has two stages with the same diameter.

IW: How would you rate the solid fuel missile?

UR: I compare Iran's solid fuel missile to the U.S. Minuteman-1, of 1961. I claim these missiles are comparable. Americans are shocked when I say this, but remember that Minuteman-1 was a first generation solid propellant missile, first flown half a century ago and therefore primitive compared to what the United States can do today. In fact, in some sense the Sejil is more advanced, not because the Iranians are so smart, but because of the march of technological innovations between than and now. Previously, achieving accuracy was a daunting challenge that required the top technological brains in the United States and the Soviet Union. Today, you can buy GPS accuracy in any consumer electronics shop for less than $200. You still have to design a GPS system that will withstand acceleration and work in a vacuum, but that's a project for graduate students in aeronautical engineering at Tehran University. It doesn't require any great ingenuity. So, Iran can make the missiles as accurate as they wish. An off-the-shelf GPS is accurate to the width of a street - 20 meters.

IW: Is there anything unique about Iran's design for the solid fuel missile?

UR: The jet vanes are an interesting design feature. In solid fuel missiles, jet vanes are usually used for the initial phase of the flight. But the Iranians managed to make jet vanes that survived the full 50 or 60 seconds of the first-stage flight. Solid propellant exhaust contains aluminum oxide; it's very abrasive. If the jet vanes don't survive during the entire burn, missile control is lost. That's why in some solid propellant rockets, like in Russia, jet vanes are discarded after a few seconds and control is done either by air vanes or by some other means, for instance by secondary injection.

IW: What about the missile casing? What is it made of?

UR: Probably maraging steel. Iran is on record trying to buy it. Some attempts were foiled. But again, the Indians bought maraging steel for their missiles. The only problem with maraging steel is that Iran would need to get maraging steel forgings as well. This may be difficult. But the fact that the Indians got them means that somebody is offering them on the market.

IW: Is there any other specialized equipment or material that Iran needs to buy in order to improve or scale-up the missile?

UR: Sure, you need some blenders, big mixers. You also need casting pits, test stands, and big x-ray machines for inspections. To develop these things on your own is difficult - they are very specialized. So, you need to buy them. By the way, all of this equipment is strictly controlled by the MTRC. But the fact that the Sejil took off successfully and completed its mission means that the Iranians have this infrastructure. They bought it. It shouldn't be in Iran but it is.

So, the proficiency is there and it can be scaled up. Based on an analysis of the Sejil's first flight, I estimate ten tons for the first stage and a five ton second stage. This is the optimum proportion. Now, to make a 20 ton first stage, if you have the infrastructure, it's straightforward. Any well run program could have the first motor on the test stand in two years from green light.

IW: Is there anything stopping Iran from scaling up this missile, from a technical perspective?

UR: Iran has everything it would need for such a program except perhaps external thermal protection for the re-entry vehicle. They have a triconic shaped re-entry vehicle that works for 2,000 km but not for intercontinental ranges. It may still be dependant on internal insulation like the old Soviet-era Scud design. Images of the Sejjil show it with a black nose tip, probably made of some ablative graphite material, but with no external insulation. Right now, I would estimate that this missile could carry a 1,000 kg payload to a range between 2,200 and 2,450 km. But, if Iran decides to go for ranges beyond 2,000 km, it will need an external heat shield. This is a challenge, but the Iranians already have the key to overcome it. Their capability to make a 50 - 60 second, 10 ton rocket motor which survives the full burn time means they can do internal heat shielding. From this, the leap to external heat shielding is not too great. Eventually they'll be able to do an external heat shield for longer ranges. I'd say that Iran has either fully formed technology or embryonic technology for every aspect of a very long range missile.

IW: You said that Iran has managed to circumvent control regimes like the MTRC to buy what it needs; who is selling to Iran? What are they selling?

UR: The open record shows that they managed to buy bars of tungsten copper alloy from China - exactly the MTCR controlled material used for solid propellant missile jet vanes. Iran may have imported tungsten copper plates and cut them into jet vanes. The Iranians might also try to get tungsten copper powder and sinter the material themselves. This is another hallmark for Iran: self reliance.

IW: How far has the solid fuel missile been tested?

UR: A few hundred kilometers. But that's not important. Iran is testing the technology. The range potential is probably at least 2,000 km.

IW: Does Iran have space inside its country to test a missile to 2,000 km?

UR: I'm not sure but I don't think so. I believe that to fire to 2,000 km or more from its Semnan test site, outside of Tehran, Iran would have to go into splash down - the missile would come down in the ocean. Bur Iran has a free ocean all the way to the South Pole. And no part of the missile would fall in any other country. So, Iran has no issue in terms of testing an intercontinental-range missile.

IW: Do you think Iran will test to 2,000 km?

UR: If they do so it will not serve their interests at present, because firing to this range may be politically sensitive. Yet Iran might eventually find some excuse to test to longer ranges, by citing changed circumstances. The range within Iran is about 1,800 km. That's the longest range point to point. There is no need at present for Iran to test further than that. If the missile flies successfully to 1,800 km it stands to reason that it will be able to fly to 2,000 km too.

IW: So 1,800 km is sufficient to test the re-entry vehicle and the guidance system for longer ranges?

UR: Up to a point. You don't need to test to the full range to see if it will fly to the full range, provided that the shorter range is stressing enough. Of course, you couldn't rely on a 300 km test flight to know how the missile would perform at a range of 2,000 km, but if you cover 80% of the range, then you are in the right ballpark.

IW: Could the current missile carry a nuclear warhead?

UR: If you are talking about the weight requirements - that is, if your question is whether the current missile has the lifting capability to sufficient to carry a first generation nuclear warhead, I think that the answer is positive. The question whether the current missile has the special adaptation to interface and successfully activate a nuclear warhead is another matter, and I'm not sure that they are there yet. But I must be clear on one important point here. The new triconic warhead is not a move toward accommodating a nuclear warhead. This warhead has less volume than the conical warhead Iran was using before. And the diameter of the central section is about 60 cm, which is very constrained for a nuclear bomb. It could be a gun type, but that would be heavy. I'm guessing that the conical nosecone had a stability problem that was stressing the missile and harming its accuracy. The triconic shape is naturally stable if designed correctly, which would improve accuracy. I'd say the new shape is designed for simplicity and accuracy, not necessarily for nuclear capability.

IW: But why else would Iran need such a missile if not to carry a nuclear weapon?

UR: From a western point of view, long range ballistic missiles make sense only when they carry a nuclear weapon. This is a legacy of Cold War thinking. The Iranians don't see it that way. Missiles are for them what both tactical and strategic air power are for the West. You can see this from what Iran displays in military parades: old hardware, old tanks, some of them from the 1950s, and half of the aircraft were bought before the Islamic revolution. Iran is building long range strike power through missiles. And not only Iran is doing this, so is Syria, Hezbollah, Hamas…for them, the rocket is king, not the combat aircraft.

IW: So the money is not there for the aircraft?

UR: No. The money is in missiles and in nuclear technology. In the missile program, you see the effect of this huge investment. Today, Iran has made a great leap forward in technical proficiency and in its capability to design and integrate ballistic missiles. The key ingredient here is not just the building of a rocket motor or a re-entry vehicle, the key is system engineering, along with system integration, and program management - all three are important and tied together.

IW: Would Iran use its missiles, armed with conventional warheads, in some sort of saturation strategy?

UR: Saturation in war time, yes. Iran will use its missiles if it is attacked. And they've developed bomblet warheads. Iran claims the results would be very destructive.

IW: So, Iran would arm its missiles with such warheads and use them as a sort of long range air power, an alternative to aircraft?

UR: Yes, why not? Iran is making a lot of missiles. The Iranians believe in conventional missiles. Not just for saturation but also to take out specific targets. They believe that their cluster warheads can take out airfields. Remember, they have practically no air force to do it. Their main striking power is based on missiles.

IW: So Iran would have to manufacture a lot of missiles and arm them with these warheads. And with the 2,000 km range, Iran would be able to base the missiles further east.

UR: Yes, giving them survivability. And the Iranians are not hiding it - on the contrary, they are bragging about it openly. . They are transparent; they want to deter any U.S. or Israeli attack. Iranian leaders openly wish for U.S. satellites to take pictures of their weapon sites and to see their capability. Mark this: for Iran, ballistic missiles are not weapons of last resort. They see them as legitimate weapons of war to be used in any conflict.

IW: What's next for Iran in terms of missile development?

UR: Watch for Iranian long range cruise missiles. I think that air breathing cruise missiles will be the next long range missile to appear. The Iranians will probably reverse engineer the KH-55s they got a few years ago via Ukraine. The main problem here is the jet engines. Making small fan jet engines is an expertise. Iran will need to buy it. The United States and France won't sell, so Iran will have to find other sources. The initial design for these missiles will not be nuclear-capable because their carrying capacity would likely be small. So they would be armed with conventional warheads as well. Later generation could become nuclear-capable.

Otherwise, expect Iran to pursue solid propellant. We'll probably see the liquid propellant program dying out. There won't be a long-range, liquid fuel missile. The Iranians will keep liquid fuel for the space program for now, but for ballistic missiles they'll be drawn to solid propellant. And if they want to put larger, heavier satellites into orbit, they may use a modified Sejil.

We'll see more and more variations of the Sejil, just as we saw with Iran's Shahab-3, which has three sub-variations that we can identify. The original Shahab-3 missile could hit Israel from western Iran. The more advanced variations can strike from further east. Sejil is the first generation and we'll see a second and third generation.

IW: Do you have an idea of production volume for the Sejil?

UR: No. But I predict that the next step on this missile will be a move to better solid propellant rocket motors, and to filament winding in order to take advantage of composite materials. Whoever sold Iran the infrastructure to make metal casings will sell them the infrastructure to make composite materials. Also, better metals will be used for thrust vectoring.

IW: Will Iran seek to add a third stage to the solid fuel missile?

UR: This is not a technical question, it's political. Iran has the infrastructure, it has the proficiency, and it has the design know-how. So, it is a question of intention. Will Iran add a third stage? Or make a bigger first stage motor? Iran is probably not eager to do this overtly because it is aware of the political implications. The Iranians are very aware of the meaning, for Europe, of longer range missiles. So, right now I don't think it's in their interest to do it openly. Actively running a full scale long range missile program may not be on the agenda, for now. But the Iranians may have a paper program for longer range missiles.

IW: There is a parallel here with the nuclear program. In both cases, Iran is seeking to build up its capability without causing alarm.

UR: Yes, the Iranians are careful to remain within the limits of legitimacy. They push the outer limit, but they are careful not to go beyond it, at least openly. This is the case in their nuclear program and - for the time being - in their missile program. You can expect this policy to continue as long as it serves Iran's interest. What they are planning behind closed doors is another question - and a very troubling one.