In the mid-1960s the Navy began to draft characteristics for a Sea Sparrow successor, designated the Advanced Point Defense Missile System. About $1 million was spent on a 14-month Concept Formulation study in 1966-67, looking at various alternative concepts, including guns and unguided rockets. However it soon became clear that a guided missile would be needed. The major changes, compared to BPDMS, would have been automation and a much hotter missile; Sea Sparrow was considered too slow, and too small a missile to destroy a missile far enough from the target ship. This study reported about 1 May 1967.
Meanwhile a NATO Naval Armaments Group had revised inter-Allied R&D procedures, sand needed a test case; Admiral Michaelis, OP-72, thought that Sea Sparrow would be a good example, and NATO Sea Sparrow was the result. It was a natural competitor to the emerging Advanced Point Defense Missile System (APDMS), and incorporated as many APDMS features as possible; in effect the founding members of the NATO Sea Sparrow group bought the APDMS package except for the missile itself and the Target Acquisition Set (which became the Hughes Mk 23). The US system, IPDMS, incorporated the TAS and thus could be considered APDMS except for the missile.
Only a conceptual design for the APDMS missile was ever formulated, but it suggests what would have been required. As sketched by Naval Ordnance Systems Command, it looked like a short Standard Missile, and at Mach 2.5 was very fast, with a 150lb double-rod warhead, a 10-in diameter, and a weight of about 825lb. It required a dual-mode seeker since radar could not be depended upon to burn through jamming at close range. The second seeker mode, infrared, would not be available under some conditions, but it was the best the developers could do. Since the big mosaic IR seekers would fill most of the nose of the missile, semi-active homing had to be done by means of a four-prong interferometer (reminiscent of the Talos configuration, adopted in that missile to permit an uncluttered air intake). The seeker was to stare rather than scan (as in more conventional types) so to engage cruise missiles head-on, acquiring them at 7-8nm and intercepting them at 5nm. Semi-active radar homing would overcome dependence on detailed threat characteristics. Within the program office, there was considerable unhappiness as to the sheer size of what was, after all, a very short-range weapon. There was also a bureaucratic problem, in that a large Sea Sparrow community naturally resented the development of an alternative weapon. The APDMS group went so far as to design a Sea Sparrow launcher large enough to accommodate it's conceptual missile, weighing about 38,000lb rather than the 23,000lb ultimately accepted. When the APDMS project was terminated in the fall of 1968, one of the first effects was the shrinkage of the launcher, which effectively killed any option other than Sea Sparrow.
The TAS concept was a major product of the APDMS exercise. IR was wanted to permit operation under electronic silence and ECM conditions, and the unit proposed was that which had originally been developed as a search/tracking for the F-14. Hughes later expanded the radar envelope (which had been envisaged as up to 20nm) towards conventional search performance, and the IR feature was ultimately abandoned.
The General Dynamics RAM was also a by-products of the APDMS exercise. Although no contractors were ever solicited, the contractors did demand a briefing, and they made proposals of their own. General Dynamics still had 25 Mauler airframes left over from that program, and offered them with Block 4 Redeye IR seekers and interferometers; but they had too small of a warhead for the APDMS mission. The same concepts have reemerged with RAM, but with an ARM radar seeker rather than a semi-active system, because the small interferometer in the RAM missile has insufficient gain for semi-active homing.
Sparrow-X: Nuclear Sparrow
NATO point defence ship systems