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Timeline for an Iranian Solid-fuel ICBM?

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In assessing the ballistic missile threat, a key issue is estimating how long it might take countries like North Korea and Iran to build missiles that could carry a nuclear-warhead-sized payload to the United States. Both countries use liquid fuel in their satellite launchers and have developed that technology further than solid fuel. As a result both countries could develop a liquid intercontinental ballistic missile (ICBM) before a solid ICBM.

However, solid missiles are seen has having several advantages over liquid missiles. They can be smaller and therefore more easily transportable, and can be carried fueled and ready to launch on a transporter/launcher. More generally, the launch preparation time is shorter than for a liquid missile, which makes them less vulnerable to attack. Modern U.S., Russian, and Chinese ICBMs use solid fuel.

So I recently looked at the state of Iran’s solid missile development program to get a rough sense of how long it might take Iran to develop an ICBM, based on the historical development programs of other countries.

First, it’s worth noting that reaching targets in the U.S. from Iran requires a very long-range missile. Distances from Iran to various sites in the United States are:

  • New York:                    9,700 km
  • Washington DC:         10,050
  • Chicago:                      10,300
  • Florida:                        11,100
  • Texas:                          11,500

Launching a missile from Iran toward the United States would require firing against the rotation of the Earth, so a missile reaching these targets would need to have a range longer than 11,000 km with a roughly one-ton payload (so that it could carry a nuclear warhead).

Schematic of Sajjil missile. (Source: http://www.turbosquid.com/3d-models/3dsmax-iranian-missile-sejil-2/464997)

Building a long-range solid-fuel missile is more difficult than a liquid-fuel missile because of the technical difficulties of manufacturing large solid motors. The longest range solid-fuel missile Iran has tested is the Sajjil. It is a two-stage missile with a diameter of 1.25 m and a length of 18 m. The total mass is about 20 tons, with a first stage mass of about 14 tons.

The Sajjil is estimated to have a range of roughly 2,000 km with a payload of one ton. The first ground test of the solid motor was in 2005, and the first flight test was in November 2008.

While the recent National Research Council (NRC) report on ballistic missile defense says that Iran might be able to use the Sajjil engines to develop a missile with a range greater than 5,000 km, it does not specify a payload mass or a configuration for the missile. However, the technical study Iran’s Ballistic Missile Capabilities: A Net Assessment by Mike Elleman at IISS looks at two options for building a three-stage missile using three Sajjil solid motors and finds a range of 2,700 to 3,300 km with a one-ton payload, depending on assumptions about the level of technology (p. 110).

In 2009, Ted Postol published a detailed technical analysis of the Sajjil. Assuming the same level of technology as Sajjil, he finds that reaching 5,000 km with a one-ton warhead would require developing a first stage with a larger diameter than Sajjil and a mass of about 45 tons. The overall missile mass would be 65 tons or more. This is significantly more massive than even U.S., Russian, or Chinese long-range solid-fuel missiles, indicating that the technology demonstrated in the Sajjil is not appropriate for scaling up to very long ranges.

Developing a solid-fuel missile with 11,000-km range would therefore require a number of advances. For example, it would require a three-stage missile, lighter weight materials, more energetic propellant, and the ability to build large solid motors. Building large solid rocket motors requires specialized equipment and tacit knowledge about the manufacturing process. How difficult is this?

The IISS report argues that the best analogous case to Iran for the development of large solid missiles is France, so looking at the French experience is instructive.

France first tested its solid-fuel M1 missile in 1967, and it became operational in 1971. It was a two-stage missile with a 20-ton mass, and a diameter of 1.5 m. It reportedly had a range of 2,500 km with a 700-kg warhead, and was therefore somewhat bigger and more capable than Sajjil (IISS report, p. 79).

France’s M4 missile, with a diameter of 1.9 m and a mass of 36 tons, had its first flight in 1980 and did not become operational until 1986—15 years after the M1. It reportedly had a range of 4-5,000 km with a payload of 1.2 tons (IISS report, p. 79).

It was not until 2010 that France deployed the M51 missile with a range greater than 10,000 km. It has a diameter of 2.3 m and a mass of more than 50 tons.

It therefore took France more than 40 years to progress from testing a solid-fuel missile that was more capable than the Sajjil to deploying a solid-fuel missile having the range Iran would need to reach targets in the U.S.

Elleman also shows that Iran’s rate of development of increasingly large solid motors has lagged the similar development in France, the U.S., China, and India (IISS report, p. 86).

This comparison does not, of course, give a definitive timeline for Iran. But it’s useful nonetheless to give a sense of how difficult a development process this is, and to show that such a missile is almost certainly at least a couple decades away. As noted above, it is likely to be able to develop a liquid-fuel ICBM well before that.

By the way, the longest range solid missile that North Korea has is much shorter range, estimated to be about 100 km with a 500 kg warhead. Called the KN-02, it is a version of the Soviet Toska missile, or SS-21.

 

Posted in: Missiles and Missile Defense Tags: , ,

About the author: Dr. Wright received his PhD in physics from Cornell University in 1983, and worked for five years as a research physicist. He was an SSRC-MacArthur Foundation Fellow in International Peace and Security in the Center for Science and International Affairs in the Kennedy School of Government at Harvard, and a Senior Analyst at the Federation of American Scientists. He is a Fellow of the American Physics Society (APS) and a recipient of APS Joseph A. Burton Forum Award in 2001. He has been at UCS since 1992. Areas of expertise: Space weapons and security, ballistic missile proliferation, ballistic missile defense, U.S. nuclear weapons and nuclear weapons policy

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  • Brian Gaulke

    You state that, “Launching a missile from Iran toward the United States would require firing against the rotation of the Earth, so a missile reaching these targets would need to have a range longer than 11,000 km.” This is incorrect. A launch against the earth’s direction of rotation means that with the missile in flight, the target is rotating toward the missile, shortening the needed range. Otherwise, nice piece.

    • David Wright

      There are two effects to take into account. The first is the rotation of the earth while the missile is in flight, as you note. The other is that the rotation of the earth reduces the speed of the missile on launch. This is more important for satellite launches and is why it helps to launch toward the east and from a launch site near the equator where the earth’s rotation speed is maximum. For short-range missiles, these two effects essentially cancel out (they would exactly cancel on a flat earth whose surface was moving in some direction), but for long-range missiles they don’t in general.

  • Martin Butcher

    You say that France, starting from a better technological base, took 40 years to develop and deploy an ICBM capable of travelling 10,000km. Yet, Iran, starting from a lower technological standard, and under sanctions could be expected to develop a similar ICBM in not less than two decades. Isn’t this inconsistent?

    • David Wright

      I think my wording wasn’t clear on this. What I meant was that based on France’s experience, a similar Iranian missile is at least a couple decades away. I’ve reworded that sentence to make that more clear.

  • Krepon

    David:
    Many thanks.
    What pattern of missile tech transfer do you 4see between NK & Iran?
    Michael

    • David Wright

      I wish we knew more in detail. The Shahab-3 is basically a Nodong and the cluster of 4 engines Iran displayed two years ago is basically the cluster from the Unha. That technology was first seen in NK. Iran’s second stage on the Safir appears to be very similar to the Unha third stage. We don’t know much specifically about the flow of technology and ideas, unfortunately.

  • http://ultimaratio-blog.org Corentin Brustlein

    Interesting piece, thanks.
    You do not mention the fact that the French M-51, as the whole French M-series, is submarine-launched. Developing ballistic missiles to be launched from subs poses additional physical constraints. Wouldn’t it be reasonable to assume that the Iranian timeline could be shortened in some way since it is less demanding for Tehran to build an ICBM than a SLBM with a similar range?

    For instance, it took 8 years for France (1963-1971) to develop and field its S-2 SSBS, a 3,000 km-range, solid-fueled MRBM.

    • David Wright

      I don’t think the fact that one is designed for a submarine and the other for land would make a significant difference, but will go back to see if there are any specific issues that arise. Differences like that are the reason I did not try to say that it would take Iran 40 years–I was mainly trying to make the case that very short timelines for developing such a missile are not realistic.

  • Twilight

    well , the problem is that Iran never saying his missile real range …. simply , Iran didn’t wanted to provoke Europe and Russia ….

    so if they test ICBM , they will come and say “It has only 2000 KM range “

    • David Wright

      Fortunately, you can’t hide missile flight tests. US early warning satellites can track missile tests and can easily distinguish an ICBM from a shorter range missile.

      • Mikah

        As a matter of fact you can! You can easily launch a 11000km range missile to hit targets that are 2000km away!
        You give the US military too much credit! For years they have ruled by fear more than anything else but in the last 10 years we have come to realize that the US military is not as good as we think they are.
        The most advanced drone in the US arsenal was guided down by the RCG. How embarassing! The iron dome in Israel could not stop zilzal one type missiles! I can go on and on about this but hope you get my point.

  • M. K. Brussel

    This analysis may be useful technically and interesting, but somewhat obscures the fact that Iranian missiles would only serve in a deterrent capacity, unless Iran’s leaders had a suicide complex. However, to confront the issue of so-called U.S. anti-ballistic missile bases (in Europe, Turkey, etc.), it does serve to illustrate the fatuousness of the recent U.S. government alarmist warnings about Iran attacking the U.S.