Britain's Staff Requirement (Air) 1236 for a Conventionally-Armed Stand-Off Missile (CASOM) emerged after the 1991 Gulf War revealed an urgent need for an air-launched night/all-weather high-precision attack weapon, for use against hardened and high-value targets without overflying heavy enemy air-defense concentrations. Its original guidelines specified ranges of 100 nmi or more, a target accuracy of some 10 feet, and a 2000-pound HE warhead able to penetrate five-to-six feet of concrete, but also called for procurement of a basically off-the-shelf design, needing relatively minor development.

Prospects of a $1.1 billion contract, with further production options, brought bids from seven international contending teams, including three from the U.S. involved in parallel JASSM submissions. After delays because of successive UK defense cuts, MoD selection of the joint low-observable 2,866-pound Storm Shadow development of MATRA's smaller 80-nm range APACHE winged dispenser weapon proposed by BAe Dynamics, was announced in July 1996.

Its choice, said the MoD, "would cement the recently-announced missile merger of British Aerospace and MATRA, and strengthen BAe's ability to play a leading role in a restructured European industry".

While sharing a similar airframe and Microturbo jet-propulsion system with the 190 nmi range French APACHE EG, now known as SCALP, MATRA BAe Dynamics Storm Shadow's 1,080-pound Royal Ordnance BROACH unitary penetrator warhead, extra fuel cell for a range increase to at least 215 nmi, and terrain-reference (TERPROM) navigation/targeting system are all of UK origin. BROACH uses tandem explosive charges to penetrate several meters of reinforced concrete or other hardened targets. The first charge is shaped to focus a gas jet and create a large funnel-shaped hole, allowing access by a second conventional HE charge to detonate within the target, and doubling the warhead's destructive efficiency. Initial BROACH ALCM sled tests in May against concrete targets 20% thicker than those capable of penetration by normal 1,000-pound warheads were claimed to show similar capabilities to the 5,000-pound GBU-28.

Pre-planned mission software can be integrated with the launch aircraft's mission planning system or as a standalone system for complete autonomy. Low-level predictive terrain-following capability maximizes missile survivability through avoidance of air defense systems. The on-board Sextant Avionique laser-gyro INS/GPS is also continually updated by terrain reference navigation. Automatic target recognition algorithms match the target scene, and with a high-resolution GEC-Marconi Avionics imaging infra-red seeker, refine the aiming point in the terminal engagement phase for optimum accuracy.

In its final Storm Shadow proposals, BAeD was reportedly able to offer the RAF significantly more missiles, believed to be approaching 1,000, within its earlier program costs, from collaborative French air force procurement. In France, multi-year orders were placed in late 1997 with MATRA BAeD for 500 essentially-similar SCALP-EGs from a FFr4.5 billion ($750 million) contract, representing a $1.5 million program unit cost. As attack weapons for Dassault Mirage 2000Ds and Rafales, these will be delivered to the French air force from 2003. Initial RAF Storm Shadow deliveries are planned in 2001, to arm Harrier GR.7s, Tornado GR.4s, and Eurofighter EF 2000s when they enter service in about 2004.

All Storm Shadow milestones have been met to date, and SCALP EG is ahead of schedule. The missile computer and IIR seeker are now available for air carry trials, in which a fully functional missile is planned to start environmental, navigation and guidance tests next year. First air firings will follow in late 2000.

By John Fricker