unable to function. The first of these missiles was known as the ASM-N-10, later designated the AGM-45 Shrike, taking its name from a predatory bird that kills its prey by impaling them on the thorns or spikes of plants or fences. Simple in concept, the Shrike took some time to perfect; the first AGM-45 Shrike missiles entered fleet service in 1963.
Along with the development of the ARM came a vital piece of equipment which was required to make it functional, the radar homing and warning receiver (RHAW), or radar warning receiver (RWR) as it is known today. Amazing as it may sound, no U.S. tactical aircraft sent to Southeast Asia in 1965 went with any sort of warning system to tell the aircrew they were being tracked by enemy. Thus, when President Lyndon Johnson began the systematic bombing of North Vietnam, with Operations Flaming Dart and Rolling Thunder, USAF, USN, and USMC aircraft began to fall in numbers that were more than just disturbing.
Interestingly, the USAF took a different approach to suppressing SAMs than the Navy or the Marine Corps. The Navy/Marine policy on SAM suppression was just that: prosecute to suppress just long enough for the strike force of attack aircraft to hit their targets, and then run for the safety of the aircraft carrier or home base. In fact, the policy of avoiding duels with air defense sites is at the foundation of USN/USMC strike warfare doctrine even today. Thus, from early 1966, USN defense suppression efforts centered around A-4 Skyhawk attack aircraft equipped with an early RWR and a pair of the new ARMs.
The USAF doctrine is completely different. For the Air Force, it was not enough to scare the operators of the SAM and AAA radars. In the view of the Air Force leadership, those individuals, and their machines of war, were there to be killed. Thus, the Air Force formed a small force of specially configured aircraft and handpicked highly trained aircrews to do the critical job of radar hunting. These were the famous 'Wild Weasels,' initially flying two- seat versions of the famous F-100 Super Sabre, configured with RWR gear, rocket pods, and napalm canisters. Although they were successful in lowering losses from SAMs to the aircraft of the strike forces going 'up north,' their own losses were prohibitively high. Thus, integrating the new AGM-45 Shrike became a 'crash' priority with the USAF. When this was done, losses among the Wild Weasel F-100Fs began to drop, and the crews began to have a future. Not much of one, though. Being on a Weasel crew was statistically suicidal in the early years of the Vietnam conflict.
However, the Shrike had significant tactical limitations and shortcomings. One big one was range. At high altitudes, the Shrike could hit radars some 21.7 nm./40.3 km. distant, while low-altitude launches could be up to 15.6 nm./ 29 km. away. But in practice, launch ranges were usually less than half of the maximum, because certain functions necessary to targeting the missile had to be performed. Most dangerous of these was a maneuver known as a 'Shrike pull-up.' The launching aircraft had to go into a 15deg climb just before launching the ARM; otherwise it would not successfully hit the target radar van. And if the enemy radar shut down while the Shrike was streaking down onto the target, the ARM was likely to miss, lacking as it did the necessary radar emissions for it to home in on. It was, as they say, a
From the very beginning of its use, the Navy and Air Force were unhappy with the Shrike's performance. In 1969, the U.S. Navy conducted a Tactical Air Armament Study which looked into shortcomings of Shrike and the whole range of USN/USMC air-launched weaponry. From this study came a whole set of requirements which led to the beginning of a development program for a new ARM program. The new missile would be small, with the same general weight and shape as the Shrike, but with greater range, speed, accuracy, and lethality. Also, it would operate from the full range of USN/USMC tactical aircraft, both planned and in service, and would both outrun and outsmart the SAMs and radar operators for every Soviet and other potentially hostile SAM system, even those still under development. It was a tall order for the program engineers at NWC China Lake, California, when they began the new program in 1972. Called the High Speed Anti-Radiation Missile, or HARM, the new missile, designated AGM-88, would take over a decade to bring into service, and would undergo many of the same trials and problems suffered by other advanced missile systems, such as the AIM-120 AMRAAM.
HARM was the first really 'smart' air-to-ground missile developed by the United States, using for the first time the new technology of microprocessors and computer software. In other words, HARM was a technical 'stretch' — betting that a number of immature technologies ranging from high-impulse rocket motors to a new generation of RWRs would come together all at once, some years in the future, within some sort of cost ceiling. Not everything went as planned. Still, by 1974 Texas Instruments was selected as the prime HARM contractor, and advanced development was under way. And by 1978 the first test firings were under way at NWC China Lake. By FY-1981, the first eighty missiles were under contract, and they headed into fleet service in 1982.
The new missile was called the AGM-88A. And the AGM-88C1 (Texas Instruments) variant is the most common version produced today. The basic — C model missile weighs in at 798 lb./362.7 kg., is 164.2 in./417 cm. long, and is based on a 10.5 in./26.7 cm. diameter airframe with a forward (guidance) fin wingspan of 44 in./112 cm. At the front of the missile is the radome for the Texas Instruments Block IV seeker, which has vastly more capability than even the — B model birds of just a few years ago. Behind the bullet-shaped seeker dome are a series of broadband antennas, which are designed to provide all the functions of an aircraft RWR system, as well as providing passive targeting for the missile guidance system. When we use the term 'broadband,' we're talking about everything from.5 to 20 GHz; this covers everything from UHF radio transmissions to short-wavelength fire control and ground-mapping radars. These antennas feed into a microprocessor-controlled digital signal processor, which is capable of breaking down all the incoming signals and translating them into a prioritized target list. This is accomplished via the reprogrammable onboard threat library, which can be used 'as is' by an aircrew or customized for a specific threat or situation. With the new seeker, even rotating air traffic control and phased array radars (like those used on the Aegis and Patriot SAM systems) can be effectively targeted and attacked.
Just aft of the seeker section is the warhead section. This is a 145 lb./65.9 kg. blast fragmentation-type unit, with a laser ranging proximity fuze, similar to that of the Sidewinder and the AMRAAM, which spews its twelve thousand tungsten cubes into the heart of the target radar. Behind the warhead section is the guidance/control section, which flies the missile during flight. This is accomplished by a digital autopilot equipped with a strapdown inertial guidance system, driving a series of electro-mechanical actuators which control the large guidance fins mounted along the mid-body of the AGM-88 airframe. Like the Paveway III, the autopilot allows the missile to fly the most energy efficient flight profile and make the most of the 'smash' provided by the HARM's rocket motor. Located just aft of the guidance section is a TX- 481 dual-grain (two-stage), low smoke (to prevent observation), solid fuel motor supplied by either Thiokol or Hercules. It is this motor that generates the incredible speed that gives the missile the first letter in its designation. The top speed, while classified, is probably greater than Mach 3, possibly as high as Mach 4 or 5. This allows it to outrun almost any SAM system in a 'quick draw' contest, should that occur. It also provides for a vast increase in range over the Shrike, probably up to a maximum of perhaps 80nm./ 146.3 km. from high altitudes (say 30,000 feet/9,144 meters), and 40 nm./ 73.2 km. when launched as low as 500 feet/152.4 meters. Normally, these ranges would probably be halved, to maintain a performance advantage over any SAMs that might be counterfired against the launching aircraft. The AGM-88 is normally carried on an LAU-118 standard launcher.
From the very beginnings of the HARM program, the Air Force maintained an interest in the new ARM. They too wanted the benefits of such a weapon, and joined in the program at their first opportunity. Initially, their participation included the development and integration of the APR- 38 (later upgraded to the APR-47 standard) RWR suite on the F-4G Wild Weasel variant of the Phantom, which was the primary USAF aircraft assigned to the suppression of enemy air defenses (SEAD) mission at the time. The APR-38/47 is a group of RWR systems, tied together to allow the F-4G WSO (technically called an Electronic Warfare Officer or EWO, but known traditionally as the 'bear') to accurately plot the positions and characteristics of hundreds of enemy threat emitters. By integrating HARM with this system, the F-4G became a radar hunter of amazing lethality, taking only one loss during Operation Desert Storm — and that happened because an Iraqi AAA round punched a hole in the aircraft's fuel tank; it wasn't able to land before running out of fuel. The crew survived the mishap without injury.
In addition to the dedicated Wild Weasel aircraft, the Air Force made several of their other new aircraft designs capable of carrying and firing the new ARM. Both new variants of the F-15 and F-16 can do so, given the right RWR systems, launch hardware, and software. And the F-16C has been extensively used to augment, and now replace, the aging F-4Gs that are on their last legs of service. As the last of the precious F-4Gs are going to the
