Potential Delivery Systems for Iran's Nuclear Program
Nuclear warheads reach a target using a delivery system or vehicle. Following the production of weapons grade fissile material, and subsequent weaponization of the material, a delivery vehicle would need to incorporate a nuclear warhead device to constitute a nuclear weapon. A viable delivery vehicle program encompasses a range of activities covering design, testing, development and production. Countries most commonly designate ballistic missiles as preferred delivery vehicles. Ballistic missiles deploy in the following manner:
"After an initial powered phase of flight, a ballistic missile leaves the atmosphere (about 100 kilometers) and follows an unpowered trajectory or flight path before reentering the atmosphere toward a predetermined target. Ballistic missile ranges can vary from a hundred or so kilometers to more than 10,000 kilometers."
Since its war with Iraq in the 1980s, Iran began to build a ballistic missile arsenal and develop the technology to attain an indigenous missile production capability. Currently, Iran possesses the largest arsenal of ballistic missiles in the Middle East.
During the 1980s, Iran financed North Korea’s modified ballistic missile programs in exchange for completed missiles and assistance in developing the Iranian capacity to assemble and produce missile components. For example, North Korea provided Iran with missile engines and helped troubleshoot technical challenges faced by Iran in building its current line of missiles. As a result, Iran designed its primary line of ballistic missiles, the Shahab series, from the base model of the North Korean Nodong missile program. The Iranian military now develops and builds modified, longer-range versions of the Shahab domestically.
According to U.S. Director of National Intelligence Dennis Blair, “Iran continues to deploy and improve ballistic missiles inherently capable of delivering nuclear weapons.” Official Iranian media reports, publicizing ballistic missile tests and military parades showcasing Iran’s hardware, have provided outsiders with the primary source of information on Iran’s missile capabilities – despite the fact that the reports often produce conflicting information and lack independent verification.
Iran’s Shahab-3 ballistic missiles, with an estimated range between 800 and 1,300 miles, possess a nuclear weapons capability. Iran could use the Shahab-3, for example, to deploy a nuclear warhead with only slight modifications. Given its technical specifications, including a payload capacity of nearly one ton, Iran would consider the Shahab-3 as the “preferred delivery vehicle” for a potential nuclear weapon. After initial tests in 1998, Iran more recently tested the Shahab-3 in the summer of 2008 during a naval war games exercise. Although the exact size of the Shahab-3 missile arsenal remains opaque, an estimate from Janes Defence Weekly contends that after tripling its stock of intermediate range ballistic missiles (IRBMs) during the course of 2008, Iran’s Islamic Revolutionary Guard Corps (IRGC) possesses 100 Shahab-3 missiles.
Beyond the basic Shahab-3 medium-range ballistic missile (MRBM), Iran possesses extended range variants of the MRBM. As noted in 2008 by U.S. Missile Defense Agency (MDA) director Henry Obering, Iran currently pursues “newer and longer-range missile systems and advanced warhead designs.” Iran’s pursuit of missile systems could involve developing indigenous production capabilities – or more simply, importing complete missile systems. In 2005, for example, officials from Ukraine conceded that six “medium-range, air-launched cruise missiles capable of carrying nuclear warheads” were sent from Ukraine to Iran in 2001.
Long-range ballistic missiles, or intercontinental ballistic missiles (ICBMs), possess a range of at least 3,400 miles. Defense Intelligence Agency (DIA) director Lowell Jacoby assessed in 2005 that “Iran will have the technical capability to develop an ICBM by 2015.” If it chooses to develop an ICBM missile capability, Iran would need to overcome various technical limitations. In particular, Iran needs to develop or acquire: multi-stage missile technology, a more powerful propulsion system, a re-entry vehicle able to withstand higher velocities and temperatures, and advanced missile guidance systems. Iran could expedite the development of an ICBM if it chose to acquire technologies—such as a multi-stage capability—from foreign suppliers like Russia, China, or a network similar to A.Q. Khan’s.
In a February 2009 report, the International Institute for Strategic Studies (IISS) illustrated Iran’s capability to do just that – speed up the development of increasingly sophisticated missile technology. IISS explains that between May 2005 and November 2007, Iran appeared to make the transition from producing a two-ton missile motor to a ten-ton missile motor. Iran’s relatively quick upgrade from a small motor to a larger one is significant because the process typically has a steep learning curve and requires hardware on export-control lists. Therefore, IISS argues that the upgrade suggests that Iran received technical assistance and export-controlled hardware from foreign sources.
Speculative reports regarding Iran’s pursuit of longer range IRBMs and ICBMs have drawn attention in recent years. In 2008, U.S. deputy national intelligence director Thomas Fingar noted Iran’s display of a 1100 mile range missile (Ghadr-1) during a military parade and Iranian claims of a new 1250 mile range missile (Ashura). In November of 2008, the Iranian defense minister declared that Iran tested a new 1,200 mile-range missile – the Sejjil. Weapons expert Duncan Lennox questioned the claim that the missile was new, pointing out the Sejjil’s likeness to the Ashura. Supposedly, the dual-engine, multi-stage Sejjil missile uses solid fuel, unlike the liquid-fueled Shahab. The significance of that distinction lies in that solid fuel missiles launch quicker than liquid fuel missiles and, therefore, are less susceptible to missile defense intercept.
Speculation periodically surfaces regarding an Iranian ICBM, commonly referring to a Shahab-6. Recent reports claim that the 3500 mile range Shahab-6, based on North Korea’s Taepodong, is under development. Iran denies it has plans to pursue an ICBM capability, however, it is unclear if Iran actively pursues, previously abandoned or even created the design for a Shahab-6 ICBM. As Stephen Hildreth of the Congressional Research Service (CRS) notes, “non-official public sources reflect little technical or program consensus regarding an Iranian ICBM program.”
Iran could also use the cover of its space program to develop parallel capabilities for a long range ballistic missile, emulating North Korea’s development of the Taepodong ICBM. Concerns over such dual-application technology heightened in February 2009 following Iran’s launch of a satellite into orbit using an-Iranian developed rocket. The technical capabilities utilized in that satellite launch, including placement accuracy and mid-flight separation, can be applied to an ICBM delivery system.
Alternative Delivery Vehicles
As an alternative to the use of the most likely delivery vehicles, ballistic missiles, Iran could deliver a nuclear weapon through nonconventional means exploiting the IRGC’s doctrine of asymmetric warfare. General asymmetric warfare theory refers to scenarios in which one state, or group, seeks to leverage its strengths or manipulate an adversary’s weakness to its advantage. In Iran’s case, for example, the IRGC could transfer a nuclear weapon device to a proxy terrorist organization. Kenneth Pollack asserts that this scenario remains unlikely because Iran “has never believed that these groups required such weapons [WMD] and because it feared that if their use were ever traced back to Tehran, the retaliation it would suffer would outweigh any gains from the attack [resulting from a weapons transfer] itself.” Additionally, Iran could launch nuclear weapons mated with short-range cruise missiles, which would be ferried to a designated target, or launch a ship carrying a nuclear weapon explosive as the delivery vehicle itself.