Development of the Sparrow missile began in the late 1950s. Over 34,000 AIM-7C, D and E models have been produced, with the 7E seeing extensive combat use in Vietnam. The AIM-7F and the AIM-7M are the only programmes still active.
Introduced in 1977, the AIM-7F has solid-state guidance, a heavier warhead and a more powerful rocket motor. By switching to the use of solid-state electronics, the Raytheon designers were able to miniaturise the seeker and guidance electronics. The space saved was shared between a new and heavier warhead and a longer rocket motor. What the designers failed to do was to eliminate the mechanical scanning motion of the seeker antenna, thus leaving the weapon vulnerable to deceptive jamming. The AIM-7F therefore had procurement limited to 5,000 rounds.
Key feature of the current AIM-7M is an advanced monopulse seeker providing improved resistance to ECM plus better look-down shoot-down capability. As its name suggests, a monopulse seeker can derive the position of the target with respect to the sightline of its non-rotating antenna by receiving a single return signal. The monopulse seeker stares directly at the target and uses a number of beams (normally four) to monitor instantaneously the region of the target and its surroundings, instead of sampling them during a rotating scan. By comparing the strength of the return signal in all antenna beams, the aiming error may be deduced directly. This technique is difficult to counter, requiring jamming systems of complex design.
AIM-7M has the same outside dimensions and general performance as the AIM-7F. The weapon entered production in FY81, and unit cost is $203,000.
Similar upgrading programmes are being applied to other air-to-air weapons produced by the West. Having taken orders for more than 6,000 rounds of its R.550 Magic IR-homing "dogfight" missile, Matra is now working on an improved Magic 2 intended to arm the Mirage 2000. Flight trials have already begun. The seeker of the current model carries out an autonomous search procedure before launch, but the seeker of the Magic 2 may be slaved to the parent aircraft's air-interception radar.
A new active proximity fuze will be fitted to cope with the triggering problems inherent in head-on interceptions. Attacks from the front hemisphere involve very high closing rates, so the warhead must be detonated without delay in order to ensure that the explosion takes place close to the target.
Technology from existing weapons is being applied to several designs which have just entered service and which may be considered "half-generation" improvements over established types such as the AIM-9L and Magic. First revealed at the 1981 Paris Air Show, and taken into combat over the Bekaa Valley, the Rafael Python 3 is a development of the earlier Shafrir 2. intended for both close-in air-combat and long-range interception duties, this new weapon has highly-swept tail surfaces, and incorporates passive infra-red homing using a single element infra-red detector. Performance is claimed to be superior to that of the AIM-9L.
The Armscor Kukri is a heat-seeking weapon of South African design. Although based on Magic technology, it incorporates several advanced features. Slightly larger than Magic, it uses a novel control system with Magic-style control surfaces (a moving surface mounted directly behind a fixed canard) in one plane, and simple Sidewinder-style delta surfaces in the other.
A helmet-mounted sight is used for target designation. The pilot aligns a sighting reticle projected onto the helmet visor with his target, and the aircraft fire-control system then slews the missile seeker head into alignment. Should the target lie outside the missile's performance envelope, the reticle will disappear. An audible tone signals that the seeker has detected the target. After lock-on, the seeker will follow the target until a fire command is given. The pilot thus has time to assess the tactical situation before launching his missile.