Arie Egozi/TEL AVIV Douglas Barrie/LONDON

RAFAEL'S DEBUT in the air-to-air missile (AAM) arena was hardly auspicious. The Shafrir 1 was in service from 1964 to 1969, including the six-day war in 1967, but the AAM was not credited with a single kill.

One of the problems was that when Israeli Dassault Mirage III pilots dumped their drop tanks to enter combat, the Shafrir 1 had a habit of falling off as well.

The Israeli defence ministry's missile design and manufacturing house has come a long way since its faltering start. The latest missile to be declassified is its Python-4, generally regarded as the most capable infra-red within-visual-range missile now in frontline service.

Development of the missile began in the late 1970s/early 1980s - a timeframe similar to that for the development of Russia's Vympel R-73 (AA-11 Archer) - with test firings believed to have been carried out no later than 1989.

Python-4s are now fielded on Israeli air force McDonnell Douglas F-15s and Lockheed Martin F-16s, and is thought to have entered operational service three or four years ago. The missile can be carried on the wingtip launch rail of the F-16C/D. It weighs 105kg, however, and is not suited for carriage on this station on the F-16A/B because it is to heavy.

Unlike the R-73, which has thrust-vector paddles to enable the agility required for high off-boresight manoeuvres, the Python-4 has only aerodynamic control.

One of the main drivers behind the Python-4 was to radically expand the "no escape zone" of the missile in comparison to third-generation AAMs such as the Python-3 and late-model Raytheon AIM-9 Sidewinders.

In providing the missile with the necessary agility to exploit a 60í-plus off-bore sight capability (compared to Python-3's 15í), the missile's manoeuvrability had to be considerably improved.

Rafael says that it opted for pure aerodynamic control, rather than a mix of aerodynamic control and thrust vectoring, because it offered advantages in both the boost and the terminal phase of the engagement. Using thrust vectoring is "wasteful" of motor energy.

The missile's novel aerodynamic configuration has two sets of cruciform surfaces immediately behind the infra-red seeker. The first are fixed canards, while the second set, are used for pitch and yaw control. A pair of ailerons is mounted directly behind the pitch and yaw surfaces providing roll stabilisation, in combination with a free rolling tail.

The missile rear body also has four fuselage strakes, which fair into the cruciform rear fins. These provide strengthening for the rear fuselage section during high-G manoeuvres. Towards the end of an engagement, with the solid motor approaching burn-out, the rear section is effectively a hollow shell. Without the strakes, high G manoeuvres at this stage would probably have meant the missile breaking up under the stress.

Rafael has not released figures for the maximum acceleration which the missile can sustain, but this is thought to be in the region of 70G. By comparison, the maximum acceleration an AIM-9M can sustain is 35G.

The missile configuration is complemented by a dual-profile solid-rocket motor providing the pilot with a weapon with a "no-escape-zone" volume with a frontal arc of 120í in the horizontal plane. The missile can also be used to engage closing targets, which are "high above" the launch aircraft in conditions under which the AIM-9 or Python-3 would lose lock on the target and go ballistic.

The missile is designed to be cued in conjunction with a helmet-mounted sight. One Israeli source with experience of the Python-4 missile suggests that, if he could see a threat in his frontal hemisphere and the target was within a 5.5km (3nm) range, no amount of manoeuvring would take it out of the missile's kill envelope.

The Python-4 differs from missiles such as the British Aerospace Advanced Short Range (ASRAAM) in that it is not optimised for an extended within-visual-range envelope, intended to maximise the F-Pole (or closest distance) between the launch aircraft and the target. The ASRAAM's engagement envelope in some areas is more akin to that of what was traditionally regraded as the domain of the beyond-visual-range missile.

The Python-4 entered service with an infra-red seeker, although Rafael has an imaging infra-red (IIR) seeker in development. The latter seeker is infra-red counter-measures resistant and is thought to operate in at least two, and probably three, spectral bands.

An IIR variant of the Python-4 may also eventually be used by the Israeli air force. The IR seeker is nitrogen, or argon, cooled.

Rafael says that the missile is 3m long and has a diameter of around 160mm. It is unwilling to discuss the solid-propellant power plant for the Python-4, developed by its Manor propulsion and explosives unit.

The missile, however, is believed to be powered by the ND-10 motor developed by Manor, which has an outer diameter of 162mm. This is a dual-thrust motor offering a profiled burn suited to initial high-G turning manoeuvres followed by a sustained lower-thrust level.

This motor is now being evaluated by Raytheon for inclusion in a larger-diameter missile it may offer for the US Air Force/Navy AIM-9X programme. Raytheon's initial bid is based around a 127mm-diameter airframe.

The missile has a "high-penetration" fragmentation warhead, but no further details have yet to be released. The weapon is fitted with a laser proximity-fuze with five windows, giving a high probability of detonation, even in "complex" engagements.

As deployed, the missile is locked on before launch by the pilot, although Rafael says that "-lock-on after launch can easily be applied".

Ran Galli, Rafael's vice-president marketing, says that the Python-4 was developed with no US assistance, allowing the missile to be exported without the need for any US authorisation.

Several countries are believed to be interested in the Python-4, including Australia, Romania and South Korea.

Rafael has achieved considerable export success with the Python-3, and the Israeli company will undoubtedly emulate this achievement with its Python-4.

Source: Flight International