Excerpt from Janes.com
"Iran has enhanced the range of its Shahab 3 medium-range ballistic missile (MRBM) and a recent Shahab test appears to be of an early version of the expected Shahab 4, according to Uzi Rubin, the former director of Israel's Ballistic Missile Defence Organisation (BMDO).

Following analysis of footage of an 11 August Shahab test in Iran, Rubin claims the new Shahab design bears a significant resemblance to the Soviet-era SS-9 inter-continental ballistic missile (ICBM), now withdrawn from Russian service.

According to Rubin, the Shahab re-entry vehicle of conical design has been replaced by a smaller vehicle shaped like a 'baby bottle' neck. Also, the cable raceway that ran along the propellant storage sections in previously presented Shahabs has been elongated and is now emerging from the rear 'skirt' of the front section in what could be termed an 'over-the-shoulder' layout.

"This kind of layout used to be a hallmark of Soviet ballistic missiles of the 1960s, such as the liquid fuel, silo-launched SS-9 ICBM," said Rubin. "Engineers have a tendency to copy their own previously successful designs. The resemblance between the new Shahab and old Soviet missiles seems to be more than a coincidence."

Rubin said that in previous Shahab variants the instrument section was separated from the re-entry vehicle and located in the missile's cylindrical section, whereas the new Shahab features an instrument section located in the 'skirt' of the re-entry vehicle. "If indeed these are the thumbprints of Russian designers, then the new Shahab's instrument section, like that of the SS-9, will travel with the re-entry vehicle, rather than be discarded. This is a useful arrangement for precise altitude fusing of nuclear warheads," he said.

"The new Shahab is longer by 1m than its predecessors," said Rubin. ?Combined with the space freed by relocating the instrument section, the new Shahab carries about 15% more propellant, enabling a range of 1,450km.?