AGM-28 Hound Dog

From Wikipedia, the free encyclopedia

The North American AGM-28 Hound Dog was the first air-launched nuclear stand-off missile deployed by the United States.

1 Development
2 Service history
3 Specifications
4 Related content

[edit] Development

The development of the nuclear stand-off missile was initiated by the USAF in 1956. Initially known as Weapon System 131B, it was intended to give Strategic Air Command heavy bombers the ability to attack the Soviet Union targets from outside Red airspace. The first powered flight of the prototype missile, designated XGAM-77, was made in April 1959. The missile's engine, airframe, and warhead were straightforward adaptations of existing technology, so the weapon's development period was quite short, and the production GAM-77 entered operational service in December 1959. It received the popular name Hound Dog, apparently inspired by the contemporary hit song by Elvis Presley.

Hound Dog was essentially an unpiloted jet airplane with small delta wings and forward canards . It was powered by a single Pratt & Whitney J-52-P-3 turbojet in a ventral pod beneath the rear fuselage, with 7,500 lb. (33 kN) thrust. It used inertial navigation for guidance, with heading updates provided by astro-trackers mounted in the launch pylon. The W28 warhead (the same as the B28 nuclear bomb) had an explosive yield of 1.1 megatons. The missile's maximum range was about 700 miles (1,100 km).

The Hound Dog was the first aircraft or missile in the Air Force inventory to have a totally "solid state" guidance & flight control system; no vacuum tubes of any kind were used in the GAM-77 guidance and flight control system. The GAM-77A had a two radar tubes for transmission and receiption of the ground avoidance system radar signal. The terrain avoidance system was a forward facing microwave.

The Hound Dog was carried by B-52 Stratofortress bombers; the B-52D, B-52 E, B-52F, B-52G and B-52H were fitted with provision for the large under wing pylons to launch the weapons, each bomber normally carrying one under each wing. The Hound Dog's fuel tanks, interestingly, could be topped up from the B-52's own fuel supply, and during takeoff its engines could be used as auxiliary booster engines for the bomber. The missile's inertial navigation system (INS) could be used as a backup system for determining the aircraft's position after the initial calibration and "leveling" which took a minimum of 90 minutes.

The original GAM-77 had three flight profiles available:

a. High Altitude Attack, where it flew at high altitude (up to 55,000 feet depending on amount of fuel on board) all the way to the target, then dived down to detonation altitude for the weapon,

b. Low Altitude Attack, where it flew at a low barometric pressure altitude of up to 5,000 feet to the target, then detonated the weapon, which had the problem that the missile had to be launched over terrain that never exceeded the flight altitude (or you blew up a hill/mountain instead of the target), or

c. Dog Leg Attack, where it flew a designated heading (high or low) to a specific location, then turned to a new heading to the target and detonated the weapon over the target either by diving (if it was a High Altitude Flight) or simply detonation if low altitude.

The original GAM-77 could be launched from the B-52 mother ship at high altitude or low altitude (not below 5,000 feet). This made several "attack profiles" for flights available: High launch/High flight, High launch/Low flight, Low launch/High flight, and Low launch/Low flight. As well as adding a "Dog Leg" in any of these launch/flight combinations.

The GAM-77 was subsequently upgraded to GAM-77A standard, with improved astro-trackers mounted in launch pylon (to better update the INS navigation system before launch), and the major improvement, which was a radar altimeter which allowed terrain following, as low as 100 feet altitude above the ground. This made the missile virtually impossible to stop or find on radar. The upgrade made possible several different altitude profiles, such as high altitude launch/high altitude cruise (high/high) or high altitude launch/high altitude cruise followed by a descent to terrain following cruise (high/high/low). Other options were high/low, low/high, low/low and low/high.

The Hound Dog was, in a head on aspect, almost "stealthy" as there were no flat surfaces that reflected radar "back" to the seeking aircraft or ground radar site. In fact, the Hound Dog is sometimes referred to as the first "stealth" missile.

In June 1963 the GAM-77 and GAM-77A were redesignated AGM-28A and AGM-28B, respectively. An updated AGM-28C, with improved guidance, was proposed in the early 1970s, but never built. It would have had improved navigation (with an on board astro-tracker), weighed less, and had additional radar absorbent material included.

A total of about 700 Hound Dogs were produced. They were intended to be replaced by the AGM-48 Skybolt, which did not enter service. The last Hound Dogs were retired in 1976.

They were replaced on SAC's B-52s by the AGM-69 SRAM missile, twelve SRAMS, six under each wing on pylons, rather than two Hound Dogs (one under each wing on pylons). Additional SRAM missiles could be carried in the bomb bay as well.