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Arabian Peninsula & Persian Gulf Database

Shahab 3: an Advanced IRBM
By Pedro B. D. & Tom Cooper
Dec 18, 2003, 12:06

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Iran gained considerable experience in the use of ballistic missiles already during the long war with Iraq, when it deployed SS-1B/C SCUD tactical ballistic missiles for striking Baghdad and several other cities in central Iraq in response to similar Iraqi strikes by FROG-7 and SS-1 Scud missiles. Original Iranian SS-1B/Cs were supplied via Libya and Syria. (Photo: ACIG archives)


The Scud Terror

The original SS-1 SCUD-A battlefield support missile was developed as a simple weapon, based on German V-2, intended for use against such large targets like marshalling areas, major storage dumps and airfields - preferrably armed with nuclear weapons, then their precision was very poor. During the Iran-Iraq war and several subsequent conflicts, however, "the SCUD" developed into a major propaganda-tool and a weapon of terror.

Especially during the IIPGW, in 1991, by repeatedly hitting Israel and Saudi Arabia with their Project 144.5 al-Hussayin "stretched"-range versions of the SS-1B, the Iraqis threatened to destroy the cohesion within the mighty Coallition put together by the USA to fight them. Had the US-administration at the time not found the way to successfully suppress the activity of two Iraqi brigades that were firing these weapons at Israel, while simultaneously keeping Israel back from attacking Iraq, that war might have easily ended in a complete chaos in which Arab countries would fight the USA and Israel - instead of Iraq.

The Iranians learned from their own experiences with Iraqis attacking their cities by FROG-7 and SS-1 Scud missiles, as well as from striking Baghdad by Scuds during the 1980s, and also from Iraqi experiences in striking Israel and Saudi Arabia. With an increasing number of neighbouring countries being equipped with similar weapons of advanced capabilities, in the early 1990s they launched their own project for development of an indigenious intermediate-range ballistic missile.

The resulting Shahab-3 is a liquid-fuelled medium range ballistic missile, and the longest-ranged of all Iranian ballistic missiles. It emerged from Iranian-sponsored cooperation in research and development about ballistic missiles with North Korea, in the 1980s, where the Project Nodong was developed on the basis of SS-1 SCUD series.
The most important part of the Nodong was its new rocket motor. The North Koreans concentrated most of their research and development work on constructing an enlargened copy of SCUD motor, then such an aggregate could supply more thrust, and with additional thrust the missile could also be significantly enlarged - which was something that could not be done with the basic SS-1 or its motor.

First tests with Nodong-1 missiles were conducted jointly by Iran and North Korea in the early 1990s, but subsequently the cooperation was cancelled and each country continued pursuing own projects, Iran starting the development of the missile that is today known as Shahab-3 on the basis of a shipment of trial Nodong-1 missiles received in 1993. According to unconfirmed reports, ever since the work on such missiles in Iran is concentrated within Shahid Hemat Industrial Group research facility, south of Tehran.

Having a good motor and a basic Shahab-3 missile well-advanced in development and expected to reach initial operational capability by 2002, the Iranians meanwhile decided to concentrate on optimizing different parts of the weapon for their purposes, foremost with the target of developing an advanced guidance system and re-entry vehicle. Contrary to the SCUD-series, namely, the Shahab-3 was to eject the booster stage with the motor and empty fuel tanks when reaching its designed apogee, and then continue towards the target only with the warhead mounted in a re-entry vehicle.

Such a manoeuvre is undertaken for several important reasons. The booster stage is becoming useless once the cruise altitude is reached, and, when empty, is increasingly instable, then its main method of steering is thrust from the main motor, most of which is spent during the early booster stage of the flight. Besides, the large booster stage makes the missile also very visible for radar systems and more susceptible to atmospheric influences and earth gravity, especially in later stages of the cruise phase and during the re-entry phase. Accuracy of the basic Shahab-3A depends on its capability to compensate course changes at the boost phase and placing the re-entry vehicle in the right trajectory: once reaching a high altitude of over 100km, where no atmospheric factors affect the missile, it travels unguided until impact.

The end of the guided flight shortly after the boost phase is the point at which the impact point is selected, after that, the re-entry vehicle/missile comes down by itself at the calculated impact point. Since most of the accuracy of such weapons depends on the relative short boost phase the Gyroscope/INS has to be extremely accurate: Iranians invested heavily in developing the capability to build such systems during the 1990s, and the Iranian defence industries eventually achieved this capability.


Shahab-3A: No Super-Scud

Combined with a heavy warhead, the basic Shahab-3A should be considered an effective conventional ballistic missile against anything but targets heavily protected by anti-ballistic missile defences, even if the usual reports about the precision of its guidance system cite a CEP between 100 and 200m.

Being developed and built by the Iranian Aerospace Industries Organization (IAIO) on a direct order from the Islamic Revolution Guards Corps (IRGC), the missile was successfully tested since 1998, when the basic guidance system was not only confirmed to be precise, but even further optimised. Simultaneously, the manufacturing infrastructure was developed and improved to enable mass production, then – other than in most other countries that attempt to develop similar weapons – the IRGC wanted the Shahab to be cheap, to be built in large numbers and be used for conventional purposes, but still so accurate that it could also be used effectively against military targets.
Essentially, the IAIO achieved this target by using only one motor/noozle on Shahab-3, powered by liquid fuels such as Kerosene, filled in a single stage, and without using an active terminal guidance system. The Shahab-3A can also be fuelled and stored for a relatively long time during war, so that prepared missiles are ready for use over stretched periods of time but on a very short notice.

The new missile is carrying the warhead mounted in a re-entry vehicle that is separating from the booster stage during the cruise phase. Subsequently, the vehicle is put into a spin – apparently with help of simple boosters at its rear. Such capability is of significant advantage also because during the re-entry all objects can easily become instable, begin to tumble and have little or not capability of course corrections, which decreases their precision dramatically.

The Shahab-3 eventually entered service in summer of 2003, and is now in use by two of ten Surface-to-Surface Missile Squadrons of the Islamic Republic of Iran Air Force (IRIAF). While manned and maintained by the IRIAF, these units, however, are effectively under IRGC-control.

Each squadron has at least six transport&erector launchers (TELs), towed by Mercedes trucks. At least four different TEL variants were meanwhile observed in service in Iran, some of which can also drive on dirt, and all of which have not only a wide range, but are also easy to be camouflaged as standard commercial 40t tilt-trailers that are in widespread use not only in Iran, but in whole Middle East and Europe. An already fuelled missile can be erected and launched within a very short period of time, with support solely from GPS-data, or by the crew comparing markings in the local terrain.

In the public there is still quite some confusion regarding the range and payload of the Shahab-3A. Credible sources put the range at 1.300km, with a warhead weighting around 1.200kg, or 1.500km with a 1.000kg warhead, and 1.700km with a warhead of 800kg.

Being interested foremost in use of such missiles for military purposes, the Iranians knew very well that large warheads are more effective, especially given the Shahab-3A’s terminal warhead velocity of between mach 6 and 7.

The accuracy of the missile, combined with its warhead, gives it the capability to destroy non-hardened or even hardened targets with single hit: already in its 1.300km-range configuration the warhead of Shahab-3 is nearly four times as heavy as that of Iraqi Project 144.5 al-Hussayin SCUD-variants used against Iran, Israel, and Saudi Arabia. For striking hardened military targets, on the other side, Shahab-3As would be launched in salvos. The Iranian strikes against MKO-terrorist bases in Iraq, in 2001, for example, clearly demonstrated the will and capability for simultaneous deployment of between 50 and 60 missiles against a single target - to increase the effects of attack.

The total war-fighting effectiveness of the basic Shahab-3A against anti-ballistic missile (ABM) defence systems remains questionable, nevertheless. It is a very fast missile and because of its separating re-entry vehicle system, its radar cross section in the terminal flight phase is very small. Compared with the SS-1 SCUD or – especially – the Project 144.5, it travels at a much higher altitude, entering the range of anti-ballistic missile defences at a much later stage and a higher speed. Its fixed trajectory, however, makes it also much more predictable, and once detected it is much easier to track.

Nevertheless, on its way towards the target the re-entry vehicle of Shahab-3A passes through a kind of a “stealth phase”: this is an effect based on the fact that the plasma at the heat shield makes it very hard to detect and track with radar when entering the Earth atmosphere.

Above and bellow: The Shahab-3A was presented in the public for the first time during the military parade in Tehran, on 22 September 2003. The original form of the re-entry vehicle with conventional, unguided, warhead can clearly be seen on these photographs.




Shahab-3B: a JDAM with Ballistic Trajectory?

However, faced with the fact that their likely opponents have a well-developed anti-ballistic missile system in service, and having experienced the imprecision of Iraqi Project 144.5 al-Hussayin missiles first-hand, the Iranians wanted to develop a missile that would not only be precise by itself, but also deploy a steerable re-entry vehicle during the terminal dive phase. Shahab-3B is a result of this effort.

Shahab-3B with its guided re-entry vehicle was presented on the most recent military parade in Tehran, held on 22 September 2004. (Photo: ACIG.org above, Yahoo.com bellow)






During the recent testing the Shahab-3B proved several significant differences over the basic production variant, with the most important changes being done on its guidance system and the warhead, but few small also on the missile body.

The most significant change is a new re-entry vehicle, with terminal guidance system and a new steering method, completely different from the normal re-entry vehicle with spin stabilization of the Shahab-3A.

The new re-entry vehicle has now place for a rocket-nozzle control system so that no spin stabilization is needed anymore - at least not during all of the flight after the boost phase. Nevertheless, this new nozzle-control system enables the Shahab-3B guidance and steering in all phases of the flight, so that course corrections can be done at any time.

The new Shahab-3B was for the first time officially tested only a very short time after the Israeli Arrow ABM system scored a first hit against a SS-1 SCUD ballistic missile. The Iranian defence minister said that the missile would be Iran’s answer to the Arrow and behind this statement are credible reasons.

The new shape of the re-entry vehicle atop the Shahab-3B is most obvious from this photograph. It is very likely that the warhead of this weapon is now not only being guided during most of its flight, but that it can also fly evasive manoeuvres, making it immensely problematic to intercept by any existing anti-ballistic missile defence systems. (Photo: SSN)


Position of the steering nozzle on the RV of Shahab-3B. (Still from IRINN video)


Around one year ago Iran claimed for the first time to have developed and produced a laser gyroscope INS system coupled with GPS as backup. For full-guided flight with trajectory of the Shahab-3B, an accurate INS and/or GPS is needed: laser gyroscope and GPS are two of the most accurate technologies, used for course calculations.

It is not yet known if this technology is also used in the Shahab-3B, but the coincidence is striking, especially as with such an accurate navigation system the Shahab-3 could archive several objectives. The missile could change its trajectory several times during re-entry and even terminal phase, effectively preventing pre-calculated intercept points of radar systems - which is a method nearly all ABM systems using these days. As a high-speed ballistic missile and pre-mission fuelling capability, the Shahab-3 has an extremely short launch/impact time ratio. This means that the INS/gyroscope guidance would also remain relatively accurate until impact (important, given the fact that the gyrosopes tend to become inaccurate the longer the flight lasts). With that guidance system, the Shahab-3B could archive an accuracy of around 30-50m CEP or even less. The Iranians have already proved of developing even more precise systems, then their Fateh-110 missiles have an electro-optical terminal guidance system: Shahab-3B is not known of having anything similar, but should be fully dependent on INS and – likely – GPS.

This new improved accuracy was apparently the reason why the warhead weight has been significantly decreased - to suggested 500kg. This, namely, is sufficient for pin-point target attack capability. Another reason for the 500kg warhead would be the improved range, which is reported to be meanwhile between 1.700 and 2.500km.

Above and bellow: Launch of a Shahab-3B as shown on the Iranian TV. (Photo: IRIB)




Conclusions

The Shahab-3 programme is extremely important for the Iranian defence capability. This weapon is now apparently the main deep-strike weapon system of Iranian armed services, deployed even ahead of fighter-bombers of the IRIAF.

This step-by-step project was provided with relatively large funding and the mass-production of the Shahab-3 is running already since two years. The Shahab-3B has apparently reached an initial operational capability phase, but it remains unclear if the version is already in production or not.

It is, nevertheless, certain that the new variant should be more expensive than the Basic Shahab-3A, which is why it is believed that the Shahab-3A will remain in production, while the Shahab-3B will only be used against high priority and/or heavily defended targets – perhaps after a salvo of Shahab-3As has forced the opponent to spend his ABMs. Equally, a Shahab-3B might be used to destroy the crucial part of the missile defence area, and the Shahab-3As could then saturate the actual target.

Meanwhile, while a number of sources was announcing a fast development of Shahab-4, Shahab-5 and even Shahab-6 – with some of the variants supposedly becoming capable of carrying satellites into the orbit – there are no traces of anything in this form. Currently, the Iranians first have to build a large number of Shahab-3As and -3Bs. Subsequently they might develop another version, with even more advanced terminal homing. Meanwhile, however, not even such changes like an (expensive) introduction of solid-fuel motor should be expected.

Two out of ten IRIAF Ballistic-missile Squadrons are now known to have Shahab-3A in service. Currently it remains unclear if a separate unit will be equipped with Shahab-3Bs, or if the new version is to enter service with the two existing units, but it is likely that one of the units equipped with older SS-1B Scuds could now be re-equipped with Shahab-3s. (ACIG.org archives)






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