AGM-28 Hound Dog - Design

Design

The Hound Dog missile's engine, airframe, and warhead were all adaptations of technology developed in the Navajo missile, adapted for launching from the B-52. The Hound Dog's design was based on that of the Navajo G-38 missile, which featured small delta wings and forward canards.

A Pratt & Whitney J52-P-3 turbojet propelled the Hound Dog, replacing the Navajo's ramjet engine. The J52 engine was located in a pod located beneath the rear fuselage, giving it an appearance similar to the Lockheed X-7 high-speed experimental drone. The J52-P-3 used in the Hound Dog, unlike J52's installed in aircraft like the A-4 Skyhawk or the A-6 Intruder, was optimized to run at maximum power during the missile's flight. As a result, the Hound Dog's version of the J52 had a short operating lifetime of only six hours. However, in combat, the Hound Dog was expected to self-destruct in less than six hours.

A derivative of the Navajo's NAA Autonetics Division N-6 inertial navigation system (INS), the N5G, was used in the Hound Dog. A Kollsman Instruments Company star-tracker located in the B-52's pylon was used to correct inertial orientation errors with celestial observations while the Hound Dog was being carried by the B-52. The INS could also be used to determine the bomber's position after the initial calibration and "leveling" process, which took about 90 minutes. The Hound Dog had a circular error probable (CEP) of 2.2 miles (3.7 km), which was acceptable for a weapon equipped with a nuclear warhead.

The thermonuclear warhead carried by the Hound Dog was the W28 Class D bomb. The W28 warhead could be preset to yield an explosive power of between 70 kilotons and 1.45 megatons. Detonation of the Hound Dog's W28 warhead could be programmed to occur on impact or air burst at a preset altitude. An air burst would have been used against a large area, soft target. A surface impact would have been used against a hard target such as a missile site or command and control center.

The Hound Dog could be launched from the B-52 Stratofortress at high altitudes or low altitudes, but not below 5,000 feet in altitude. Initially, three different flight profiles for the Hound Dog were available for selection by the commander and the bombardier of the bomber (though other options were added later):

• High Altitude Attack: The Hound Dog would have flown at a high altitude (up to 56,000 ft (17070 meters) depending on the amount of jet fuel on-board the missile) all the way to the immediate area of its target, then diving to its nuclear warhead's preset detonation altitude.

• Low Altitude Attack: The Hound Dog would have flown at a low altitude - below 5,000 feet (1525 meters) (air-pressure altitude) to its target where its nuclear warhead would have detonated. In this mode of operation, the Hound Dog had a shortened range of about 400 miles (645 km) when this flight profile was used. The missile would not carry out terrain following in this flight profile. No major terrain obstructions could exist at the preset altitude along the missile's flight path.

• Low Altitude Attack: The GAM-77B (later AGM-28B) could fly a low RADAR altitude, from 3,000 feet down to 100 feet from the ground. As mentioned above in the GAM-77A model description, this shortened range. However, the improvement of 'flying in the weeds,' was such that the missile could be flown down in ground clutter thus nearly invisible to radar detection. Eventually, all A model GAM-77s were given this modification as well.

• A Dogleg Attack: The Hound Dog would have flown along a designated heading (at either high or low altitudes) to a preset location. At that location the missile would have turned left or right and then proceeded to its target. The intention of this maneuver was to attempt to draw defensive fighter planes away from the missile's target.

The first air-drop test of a dummy Hound Dog was carried out in November 1958. 52 GAM-77A missiles were launched for testing and training purposes between 23 April 1959 and 30 August 1965. Hound Dog launches occurred at Cape Canaveral Air Force Station, at Eglin Air Force Base, Florida, and at the White Sands Missile Range, New Mexico.

The Hound Dog missile's development was completed in only 30 months. North American received a production contract to build Hound Dogs on 16 October 1958. The first production Hound Dog missile was then delivered to the Air Force on 21 December 1959. 722 Hound Dog missiles were produced by North American Aviation before its production of them ended in March 1963.

In May 1961, an improved Hound Dog missile was test-flown for the first time. This upgrade incorporated improvements to reduce its radar cross-section. The Hound Dog already had a low head-on radar cross-section because of its highly swept delta wings and canards. This low radar cross-section was lowered further by replacing its nose cap, its engine intake spike, its engine duct with new components that scattered or absorbed radar energy. It has been reported that these radar cross-section improvements were removed as Hound Dogs were withdrawn from service.

The GAM-77A version of the GAM-77 also included a new Kollsman Instruments KS-140 star-tracker that was integrated with the N-6 inertial navigation system. This unit replaced the celestial navigation star-tracker that had been located in the B-52's wing pylon. The fuel capacity of the GAM-77A was increased during this upgrade. A radar altimeter was added to the missile to provide (vertical) terrain-following capability to the Hound Dog. 428 Hound Dog missiles were upgraded to the GAM-77A configuration by North American.

66 GAM-77A Hound Dog missiles were launched for testing and training up through April 1973.

In June 1963 the GAM-77 and GAM-77A were re-designated AGM-28A and AGM-28B, respectively.

In 1971, a Hound Dog missile was test-flown with a newly-developed Terrain Contour Matching (TERCOM) navigation system. Reportedly, the designation AGM-28C was reserved for this version of the Hound Dog if development had been continued. While a Hound Dog with TERCOM was never deployed, this technology, with much better electronics and digital computers, was later used in both the Air Force's Air Launched Cruise Missile and the Navy's Tomahawk missile.

In 1972, the Bendix Corporation was awarded a contract to develop a passive anti-radiation missile radio seeker to guide the Hound Dog missile to antennas transmitting radar signals. A Hound Dog with this radar seeker was test-flown in 1973, but never mass-produced.