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Beyond-visual-range AAMs

The advent of extended beyond visual range (BVR) air-to-air requirements has inevitably led missile design houses to look at ramjet sustainers as a potential power plant solution, and the Royal Air Force's Future Medium Range Air-to-Air Missile (FMRAAM) is, therefore, not the first to have a design solution built around a ramjet power plant.

The US Navy's abortive Advanced AAM (AAAM) project to replace the Hughes AIM-54 Phoenix demanded both range and "end game" kinematic improvements which required a hybrid power plant solution. Both ramjet and solid-propellant designs were offered for the AAAM.

The solid-propellant design proposed by General Dynamics and Westinghouse used a booster coupled with a two-pulse sustainer - an approach which raised separation and ignition issues. Hughes and Raytheon opted for a more elegant integral rocket ramjet design, although the single chin intake would have limited terminal manoeuvring in comparison to a two- or four-intake design.

In the event, the US Navy cancelled the AAAM, although it still requires a replacement for AIM-54. This could be met by a ramjet-powered derivative of the Hughes AIM-120 Advanced Medium Range Air-to-Air Missile.

In competing for the FMRAAM, British Aerospace has already looked at a dual- thrust solid-rocket design, such as its S225X missile. The problem with a solid-propellant design, however, is partly one of simple physics - in terms of volume, solids do not provide the range capability of a ramjet sustainer.

This, coupled with the constraints imposed by the need to fit the missile into the fuselage recesses on the Eurofighter EF2000, meant that a solid-propellant design risked falling short of the desired range laid down in Staff Requirement (Air) 1239 for the FMRAAM.

Within Europe, France, Germany and Sweden have all declared an interest in an extended-range BVR weapon. Both South Africa and Israel are also exploring ramjet technology for AAM applications. South Africa's Somchem began examining ramjet technologies in late 1987, and has carried out several test firings from the Alkantpan test range of a ramjet test vehicle feeding into its proposed Long Range Tactical Missile, the primary application of which is Kentron's 100km (55nm)-plus range S-Darter AAM.

Israel's Rafael Manor propulsion division is also investigating ramjet propulsion and, given Israel's previous links with South Africa on missile development, it is probable that some of the ramjet development may have been shared.

Russian missile design bureaux are also interested in ramjet propulsion for air-to-surface and surface-to-air applications. Vympel's ramjet derivative of the R-77 (AA-12 Adder) has been tested fired from a Sukhoi Su-27 Flanker on at least five occasions, and it can only be assumed this programme is proceeding.

A Russian air force requirement for an ultra-long-range missile appears to have been won by Novator, with its KS-172 design, and not Vympel. The Novator design harks back to the General Dynamics/Westinghouse AAAM design in relying on a solid-propellant booster married to a "conventional" solid-rocket-motor missile.