The AGM-45
Shrike was a
U.S. Navy* and
U.S. Air Force air-to-ground missile. It was the the first
ARM, or
Anti-Radiation Missile the USAF fielded. This was a new class of weapons intended to cope with a new emerging threat - that of the ground-to-air missile, or
SAM. Although ground emplacements had always been a problem for aircraft in combat, up until the introduction of the SAM it had always been feasible to avoid
flak or
machine gun AAA sites by changing
altitude. Both were short ranged and only effective in large numbers, which meant that the only time aircraft typically had to worry about them were when the aircraft was forced to go to where the gun emplacements were - when bombing high-value targets, in other words. Suppressing this ground fire was usually not worth the effort - there were too many guns, and they were too difficult to locate without going down and looking for them - in other words, sticking the pilot's head into the lion's mouth. In addition, the only realistic way to attack them was with guns, which meant it was easy for a AAA emplacement to determine if it was under attack, and to continue firing if not.
The SAM changed the equation. Suddenly, single sites could pose a real danger to even high-flying aircraft from long ranges (up to 15 or 30 miles in extreme cases, early on). Radar guidance meant that these sites could 'see' and hit their targets from much farther, with higher accuracy. Some form of countermeasure was needed.
The Shrike was built to counter the Fan Song radars of Soviet-built SAM sites, with design beginning in 1958 based on the AIM-7C Sparrow. It reached IOC in 1965. It was a fast, heavy missile intended to be passively guided. It would be targeted not using radar from the launching fighter, but rather would be able to 'listen' to the electromagnetic radiation put out by the radars used by SAM sites, and could follow those emissions in order to detonate on or near the radars. Since the SAMs were useless without the radars to guide them, destroying the radar would result in a mission kill. In order to utilize the Shrike properly, dedicated aircraft using new tactics were required. Originally, volunteer crews flew F-100 Super Sabre aircraft on the SEAD mission, but the task was quickly transitioned to the faster and more powerful F-105 Thunderchief. After the Thud inventories began to fall, dedicated F-4 Phantom II models (EF-4G) were used.
The Shrike was not a magic bullet, and it was not an easy weapon to use. In order to get a lock onto a radar signal, the operator usually had to wait until the SAM radar had switched to tracking (targeting) mode, as opposed to search mode. In other words, the airplane had to wait until the SAM was trying to shoot it down before engaging. Also, the sensor window was fairly narrow, meaning the launching airplane had to be flying towards the radar in question within a relatively narrow flight profile. Thus, the SEAD pilots (known as Wild Weasel for their flying techniques) had to be adept at actually evading launched SAMs, rather than just avoiding their launch sites.
The Shrike was continually improved over its lifespan, with different sensor modes and incremental improvements to its guidance systems added and removed as the opposing SAM systems evolved to meet the threat. It was finally retired in favor of the AGM-88 HARM in 1992, having served 34 years with over 20,000 copies produced. Although a more capable missile (the AGM-78 ARM) was deployed in Vietnam alongside the Shrike, its much higher cost meant that expenditure of an AGM-78 in combat resulted in lengthy debriefings and paperwork - so pilots were always much quicker to use a Shrike.
locke baron points me to a relevant bit of trivia. The current U.S. doctrine of using ARMs during anti-shipping strikes dates to an incident involving the Shrike. In 1972, the USS Worden (CG-18) was serving as support in the Gulf of Tonkin during a large U.S. airstrike on Haiphong. Two AGM-45s, launched from an unidentified U.S. support plane (likely a Wild Weasel performing SEAD on SAM sites) acquired lock-on on the Worden's own SAM radar. They completed their attack, killing one crewman and disabling the Worden's radar systems. Because of this, it became doctrinal to include ARMs in attacks on ships, since nearly all of the electronic countermeasures a ship can muster up against air threats involve EM radiation.
AGM-45 Shrike
- Contractor: Texas Instruments
- Length: 10 ft (3.05 m)
- Diameter: 8 inches (~0.2 m)
- Range: max 28 miles (45 km)
- Speed: max ~ Mach 2
- Propulsion: Solid-fuel rocket, either Aerojet or Rocketdyne depending on version
- Warhead: Blast/Fragmentation, 147-149 lbs.
- Unit cost: $130,000 (Flyaway cost, 1961 dollars)
* davisonhg is quite correct in the below writeup. I neglected to mention that the original developer of the missile was the Naval Weapons Center at China Lake. It was originally deployed on both F-105s of the PACAF and aboard ship on A-4 Skyhawks, A-6 Intruder and F-4 Phantom II aircraft in addition to dedicated Wild Weasel airplanes.