Bat (guided bomb)

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The SWOD MK 9 "Bat" was a radar-guided glide bomb that was built by the United States during World War II. It lacked any form of propulsion, but is still often, incorrectly, referred to as a missile.

In January 1941 RCA proposed a new TV-guided anti-shipping weapon they called Dragon. An operator would use the TV image sent from the nose of the weapon to guide it via radio control, which would operate aerodynamic controls attached to a standard US bomb. The National Bureau of Standards (NBS) would provide the airframe. Work on the system progressed, but by the time it was ready for testing the threat was now seen to be the German U-boat fleet, so the design was changed in June 1942 to drop depth charges instead, and became known as the Pelican, this time guided by a semi-active radar homing system so it could be used at night by following the launch aircraft's own sea-search radar signals that were used to fine the U-boat.

By mid-1943 the U-boat threat was dwindling, so the plans were changed again to use a new active radar homing guidance system from Western Electric with a standard 2,000 lb GP bomb. This form of the Pelican entered testing in 1944, and in tests at the Naval Air Station, New York, it hit its target ship two our of four drops in July 1944.

Meanwhile plans were made to introduce a production version of the system, combining the original NBS aircraft with a 1,000 lb GP bomb and the new radar system from the Pelican. The guidance system was gyro-stabilized with an auto-pilot supplied by Bendix Aviation, and the steerable tail elevator was powered by small wind-driven generators. In total the airframe weighted 600 lb, and was 11 ft. 11 in. long with a wing span of 10 ft. Development of this version was supervised by the Navy's Bureau of Ordnance in partnership with the Massachusetts Institute of Technology (MIT), with the NBS in charge of the overall development. Flight tests were conducted at the Naval Air Ordnance Test Station at Chincoteague Island, VA. MIT's Hugh Latimer Dryden later won the Presidential Certificate of Merit for the development of the Bat.

The Bat eventually saw combat service from May, 1945 off Borneo, where it destroyed several Japanese ships including a destroyer sunk at a 20 mile range. Several Bat missiles were also fitted with modified radar systems and destroyed Japanese-held bridges in Burma and other areas. It was carried primarily by the PB4Y-2 Privateer patrol bomber and dropped from an altitude of 15-25,000 feet at 140-210 knots. Two versions were used during the war, the naval version officially known as the Swod Mark 9 Model 0, and the land-attack version as the Swod Mark 9 Model 1. After the war they were retroactively named the ASM-N-2 (air-to-surface missile, naval, model 2) when the Navy and Army adopted a single naming system for all of their rocket and missile projects.

When used during World War II, the Bat proved somewhat disappointing. A total of 3,000 Bats were manufactured, but most were never used. It was taken out of deployment following the war after tests revealed the radar could be relatively easily foiled by simple countermeasures.