The semi-active radar homing conventional warhead Standard family of naval SAMs started development in the early 1960s as the replacement for the Terrier and Tartar systems. The latter's replacement was the Standard SM-1MR (RIM-66A), and was designed with an engagement range of 46.35 km (28.8 miles) and an altitude of 4515240m (150-5O,OOOft). The Terriers replacement, designated Standard SM-1ER (RIM-67A) had a range of 74 km (46 miles) and altitude limits of 45-24385 m (150-80,000 ft). After entering service from 1968 onwards in ships undergoing refits and on new-build warships, both missiles have undergone several reliability improvement and performance update programmes. A new dual-thrust motor for the Standard SM-1MR produced the RIM66B missile with a 45 per cent increase in maximum range and a 25 per cent increase in the upper altitude engagement limit. ln most cases the changes that have been made have been incorporated as production 'Block' changes which have not given rise to any new designations. The most recent version of the SM-1MR, however, has been given the designation RIM66C or Standard SM-2MR as it is the missile designed to operate with the AEGIS air-defence system. The AEGIS system allows for mid-course missile guidance which extends the range of the Tartar-sized missile by 60 per cent to around 74 km (46 miles). A corresponding Standard SM-2ER variant or RIM-67B is not designed to be fired by AEGIS-equipped ships, although improvements in its booster technology adds. a complete Mach number to its velocity to give a kinetic range far outside the current limits of an AEGIS type fire-control system. However, the improvements considerably enhance the weapons' capabilities against high performance aircraft and missiles. Those ships equipped with Terriers and its Standard SM-1ER replacement have suitable fire-control systems and are getting the Standard SM-2ER.

A low-yield nuclear fission warhead, the W81, is under development for deployment with some 500 or so Standard SM-2MR and SM-2ER missiles from the mid-1980s onwards to replace the Terrier RIM-2D(N). Designated Standard SM-2(N), the missile will become part of the ship's normal missile outfit. Further improvements are underway to both missile types to counter high level diving missile targets. The Standard SM-1MR is used by Australia, France, Italy, Japan, the Netherlands and USA, while the SM-1ER, SM-2MR and SM-2ER variants are reserved to the US Navy.

Specification RIM-66A Standard SM-1MR

Type: medium-range area-defence missile

Dimensions: length 4.47 m ( 14 ft 8 in) diameter 0.343 m ( 1 ft 1.5 in); span 0.914 m (3 ft 0 in)

Weights: total round 578.8 kg ( 1, 276 lb); warhead ? HE Performance: maximum speed Mach 2+; range 46.25 km (28.75 miles); maximum altitude 15240 m (50,000 ft)

Specification RIM-66B Standard SM-1MR

Type: medium-range area-defence missile

Dimensions: length 4.724 m ( 15 ft 6 in); diameter 0.343 m ( 1 ft 1.5 in); span 0.914 m (3 ft 0 in)

Weights: total round 608.7 kg (1,342 lb); warhead? HE Performance: maximum speed Mach 2+; range 67 km (41.6 miles); maximum altitude 19050 m (62, 500 ft)

Specification RIM-66C Standard SM-2MR

Type: medium-range area-defence missile

Dimensions: length 4.724 m ( 15 ft 6 in); diameter 0.343 m ( 1 ft 1.5 in); span

0.914m(3ft0in) Weights: total round 608.7 kg (1,342 Ib); warhead? HE Performance: maximum speed: Mach 2+; range 74 km (46 miles); maximum altitude 24385 m (80, 000 ft)

Specification RIM-67A Standard SM-1ER

Type: medium-range area-defence missile

Dimensions: length 7. 976 m (26 ft 2 in); diameter 0.343 m ( 1 ft 1.5 in); span 0.914 m (3 ft 0 in)

Weights: total round 616.9 kg ( 1, 360 lb); warhead ? HE Performance: maximum speed Mach 2.5+; range 74 km (46 miles); maximum altitude 24385 m (80, 000 ft)

Specification RIM-67B Standard SM-2ER

Type: long-range area-defence missile

Dimensions: length 8.23 m (27 ft 0 in); diameter 0.343 m ( 1 ft 1.5 in); span 0.914 m (3 ft 0 in)

Weights: total round 1387. 1 kg (3,058 lb); warhead? HE Performance: maximum speed Mach 2.5+; range 148 km (92 miles); maximum altitude 30480 m ( 100,000 ft)