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STAND-OFF MISSILES IN DEVELOPMENT

These days, flying non-stealthy aircraft over heavily defended enemy territory is viewed by the military as far too risky - at least in the early stages of a conflict. For this reason calls for high-precision stand-off weapons have been getting louder in recent years. The idea is that such weapons will enable strategically important facilities such as hardened command headquarters, communications centres, air defence positions, bridges or supply points to be taken out at distances of over 250 kilometres. In other words, a guided missile released from an airborne platform, for example, over Hamburg, should be able to find its way to Berlin and independently locate its target there to within one or two metres.

Employment of stand-off weapons in such a scenario reduces the risk to one's own aircraft, which after all can cost over $45 million (DM 100 million) each. But above all it eliminates a lot of the danger to which aircrew are exposed. In an age in which the USA has become accustomed to waging wars without sustaining any fatalities of its own, this is an important psychological consideration. At the same time it is clear that modern stand-off weapons do not come cheap due to the sophisticated technology required, so that the European air forces, at least, can only afford a few hundred of them.

But it is early days yet, as the three main new stand-off weapon programmes - Taurus from LFK/Saab Bofors Dynamics, Storm Shadow/Scalp EG from Matra BAE Dynamics and JASSM (Joint Air-to-Surface Standoff Missile) from Lockheed Martin - are currently still only in the development phase. Given the similarity of the requirements each of the weapon systems is to satisfy, it is hardly surprising to find a lot of commonality in their designs. However, there are a few clear distinctions at the detailed level.

As far as the aerodynamics is concerned, for example, Taurus has small, sharply swept back wings and a wide body which contributes to the lift. High agility is needed in order in particular to be able to make rapid corrections of course and position during the terminal phase, which in turn is necessary for accurate alignment of the warhead. Storm Shadow/Scalp EG, by contrast, has narrow wings which extend out a long way. JASSM is a low-wing aircraft which also has high aspect ratio wings.

When it comes to the airframe, Lockheed Martin has chosen to use composites, but availing itself relatively simple technology that originates in boat building. Use of composites permits complex shaping of the missile that is optimised to produce a low radar cross-section and for which a patent has been applied by the manufacturer. Taurus on the other hand, which has large surface precision-cast parts from Thyssen (approx. 60 x 80 x 120 cm maximum), is pursuing a quite different approach. The uppermost objective here is to keep down the manufacturing costs.

The stand-off weapons are powered with small jet engines, in more than one case with a low bypass ratio. As the units only fly for 20 to 30 minutes, they can be built with cheap parts. However, it is important that they deliver enough thrust to permit speeds of over Mach 0.8 at extreme low-level flight, using as little fuel as possible to do so.

The warhead is designed so that it is effective against different types of target. It must therefore be capable both of achieving a splitter effect and of penetrating thick bunker walls. A hollow charge that is connected in series assists with this latter task. It is important that the weapons should have an "intelligent" ignition system which, for example, does not trigger the primary explosive device until several walls have been penetrated.

At the heart of the stand-off weapons is a high-precision navigation system. In the case of Taurus, GPS, inertial navigation and a terrain reference system, whereby radar altimeter data is compared with stored terrain profiles, are combined into a "tri-tech" system. In addition, an imaging infra-red sensor is carried in the nose and this also targets predefined reference points en route. During the terminal phase the IR becomes the critical sensor, scanning the terrain for the target, which it compares with digitally stored templates.

Storm Shadow/Scalp EG also works with GPS, INS and terrain profile matching, but only uses the IR sensor during the terminal phase. JASSM on the other hand makes do with only INS and GPS: evidently the Americans are assuming here that their GPS systems will be jam-resistant. In the final phase of flight an infra-red camera is used as with all the other systems.

All in all, a stand-off weapon is thus an extremely complex system. This makes it all the more astonishing that Taurus has been developed over such a short period. Between award of contract on 31 March 1998 and the first free flight over the North Swedish Vidsel firing range on 4 October 1999 only 18 months had elapsed.

The second free flight, this time with more sophisticated navigation system components, took place on 30 September 2000. A third test flight is scheduled for the autumn of 2001, this time with all systems. The number of expensive free flights can be strictly limited in this way, according to the manufacturer, because of the extensive modelling and aerodynamic testing of the individual components and ground testing of the warhead.

Negotiations for industrialisation and series production of the Taurus for the Luftwaffe have already begun. The development programme having cost $230 million (DM 493 million), 600 Taurus, worth $434 million (DM 933 million) (i.e. approx. $723,000 or DM 1.5 million per unit) are to be procured for the Tornado and Eurofighter. Eurofighter integration costs will add another $128 million (DM 275 million, at December 1999 prices). But just how quickly the German Ministry of Defence can come to a purchase decision and whether the numbers will stay unchanged remains to be seen. "Decisions on procurement of the Taurus will have to wait until the new materiel and equipment concept for the Bundeswehr has been approved," is the cautious view in Berlin.

Once the Taurus has entered service with the Luftwaffe there will be the prospects of export sales. The manufacturers currently have their sights set above all on Spain and Australia. In the United Kingdom and Italy Taurus has had to concede defeat to competitor Matra BAE Dynamics. No doubt political considerations played a paramount role here, for technically Storm Shadow/Scalp EG is inferior to the Taurus; nor have the English and French gained any advantage as regards in-service date either. Contracts were awarded by London (#700 million for development and procurement) in February 1977 and Paris (500 guided missiles) in December 1997, yet the first free flight only finally took place at the end of December 2000. Admittedly, this was a complete success and the weapon used was complete apart from the warhead, flying a 250 km distance.

Meanwhile Matra BAE Dynamics has notched up Euro 1.5 billion worth of orders for the Storm Shadow/Scalp EG. In October 1999 Italy joined the United Kingdom and France on the programme, and in August 2000 Greece also ordered the cruise missile for its Mirage 2000-5 Mk2. Other platforms are the Tornado, Harrier and Rafale. First delivery is scheduled for 2002/2003.

While the European programmes are steaming ahead without any problems to speak of, the US Air Force has had to stretch out its JASSM project by around a year due to initial technical difficulties with the engine and aerodynamics in August 1999. A decision on the start of production is now expected in the early autumn. All the same, the USAF is planning to purchase at least 2,400 JASSMs to equip its F-16, B-1B, B-2 and B-52 aircraft. The US Navy may also order some. The success of JASSM will be partly down to its price, which is expected to be less than $400,000 (DM 850,000) per unit. If the manufacturers succeed in keeping it down to this level, the Air Force would be interested in buying more of the missile.

From page 64 of FLUG REVUE 4/2001