The only one of the SWOD series to reach production was the “SWOD Mark 9”, the Bat. It was built around a 450 kilogram (1,000 pound) bomb and had a fully active radar seeker. Its NBS-designed airframe had a high wing and twin tailfins. The Bat was 3.63 meters (11 feet 11 inches) long, had a span of 3.05 meters (10 feet), and weighed 853 kilograms (1,880 pounds). Incidentally, some Pelicans were converted to a “Poor Man’s Bat” configuration by the simple measure of adding a radar transmitter to complement the Pelican’s SARH seeker. These weapons may have been used for trials, though some sources say there was a push to introduce them to combat on a fast-track basis; in any case, the Navy preferred to go on to the definitive Bat.
The Bat’s guidance system was particularly sophisticated for the time. After being dropped, it glided toward the target on a preset course using a gyrostabilizer system to keep it on track. As it neared the target, the bomb locked on with its own radar system that guided it into the target. Since the radar seeker was conceptually similar to the “sonar” system used by a bat to prey on flying insects, the weapon was named after the bat. The Bat also included a self-destruct mechanism to keep it from falling into enemy hands, and obtained its electrical power from four small windmill generators.
The Bat was put into operation in May 1945, on Navy PB4Y-2 Privateer patrol bombers, maritime derivatives of the Consolidated B-24 Liberator. One Bat was carried under each wing. Privateers crews claimed many successes against Japanese shipping in the seas around Borneo, though some sources suggest they may have exaggerated the weapon’s effectiveness. Bats with modified guidance systems were also used against ground targets in Burma and other Japanese-held areas; they simply homed in on the biggest target in their radar seeker.
The Navy tinkered with the Bat for a time after the war, successively renaming it “ASM-2” and then “ASM-N-2”. However, its radar seeker was too easily spoofed and the weapon quickly faded into obscurity.