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During 1988-90, the Iraqis made strides in their indigenous rocket program, which was centered on upgrading the performance of the Scud. Tehran, some 300 miles from the Iran-Iraq border, was outside the range of the unmodified Scud-B, which can travel a maximum distance of 300 km. To overcome this deficiency, Iraq extended the range of the Scud twice, apparently relying heavily on foreign technical assistance and equipment.

The second Scud modification, designated the al-Abbas, was tested in April 1988. It had an enhanced range of 900 km, putting all of Iran, as well as the Strait of Hormuz, within reach. With a diameter of 0.88 meters the al-Abbas was some 14.50 meters in length -- some three meters longer than the SCUD-B (length: 11.50 meters; diameter: 0.88 meters). However, it was not clear that the al-Abbas was stockpiled in any large numbers or even achieved operational status. Apparently, this missile had been test-fired only once. According to one a detailed report, these modifications were achieved by cannibalizing propellant and oxidizer tanks from other Scuds, lengthening the size of the tanks, and increasing the amount of fuel. Additionally, the Iraqis reduced the regular Scud payload from 1,000 kg to 140-180 kg.

Developing Nations and Warhead Dynamic Performance

Recently, it was suggested that the developing nations missile program warheads would be tumbling about their center of gravity during re-entry, which would then make it difficult to identify. This was because they were not being spun-up along their longitudinal axis prior to re-entry through the atmosphere.

A warhead is much like a bullet fired from a rifle barrel. If the barrel is grooved to spin up the bullet along its longitudinal axis it tends to fly through the atmosphere to its target more smoothly and accurately. If the barrel is not built with this capability, the bullet tumbles uncontrollably about its center of gravity throughout its flight in the atmosphere to its target. This tumbling reduces the accuracy of the projectile.

This kind of missile warhead tumbling was noted in the ballistic flights of Iraqi's Scud-B, Scud-C/Al-Hussein, Scud-D/Al-Abbas ballistic missiles during the Gulf war. In this particular case all of the warheads remained attached to the Scud derived rocket bodies. The length of the Scud-C and D missile bodies and the failure to spin up either the missile with its warhead or separate the warhead after missile spin up made them extremely unstable and in accurate during re-entry to their target.

Today this is not the case with North Korean derived warhead technology. North Korea successfully demonstrated payload spin up with the satellite launch attempt of the Taep'o-dong-1 or PAEUTUSAN-1 booster. The Paeutusan-1 solid propellant third stage both demonstrated a near full duration burn and the spin up of the stage and satellite along its longitudinal axis. However, the third stage solid motor ruptured, de-orbiting the satellite, almost immediately after orbital insertion while achieving orbital velocity.

Therefore, it would be correct to assume that besides North Korea's, No-dong (first stage of Taep'o-dong-1), both Pakistan's Ghauri-II and Iran's Shahab-3 all benefit from this spin-up technology. The Shahab-3/Ghauri-II both apparently spin up the single booster stage and warhead combination starting at about 10 seconds before the termination of the powered flight at 110 seconds. At this point after 110 seconds of powered flight the warhead is then separated from the booster stage to fly on a re-entry trajectory that remains stable to its target. With the addition of GPS targeting the warhead accuracy is greatly enhanced. There are still many in the analytical community that question, perhaps correctly, this suggested accuracy of 190 meters to over one kilometer. There can be no doubt that this spin-up technology does improve the accuracy of these warheads over the previously demonstrated poor capability. Since the warheads are not tumbling it in fact enhances the interceptor sensor signature identification capability verses that of a tumbling warheads signature.

Equally revealing is the fact that this is the area where the Iranian Shahab-3 has repeatedly failed in flight test. If the steering vains are not equally positioned correctly or are defective in any way the missile and warhead combination would tumble about its center of gravity out of control destroying the missile. The resulting tumbling warhead whether attached to the remaining missile body or not would in all probability be destroyed during its re-entry. It is known that Iran has and continues to suffer from a steering vain quality control problem for its Shahab-3 ballistic missile that the Germans during WW-II solved and that the United States and former Soviet Union were able to easily resolve with out using specialized coating.

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