B-23 39-53 dropping 4000 lb bomb at Aberdeen Proving Ground 1942
In October 1941, General Henry “Hap” Arnold, the head of the U.S. Army Air Forces, initiated a groundbreaking project at the Muroc Dry Lake Bombing and Gunnery Range in California. This project involved the testing and development of unmanned controlled winged bombs and aerial torpedoes, marking the early stages of what would become the first “smart bombs.” The program aimed to create weapons that could be guided to their targets from a safe distance, minimizing the risk to the mother aircraft and its crew.
Early Testing and Development
The B-23 Dragon bomber (tail number 39-53) was designated as the “mother ship” for these experiments. The concept revolved around attaching a 2,000-pound bomb to a winged airframe equipped with flight servo equipment and radio controls. The first tests of this glide bomb (GB) occurred on November 8-9, 1941, when a B-23 dropped a GB from 7,000 feet over the Muroc lakebed. The GB, essentially a standard bomb fitted with wooden wings and a stabilizing gyro, was designed to be released at the beginning of a bombing run, allowing the B-23 to stay out of enemy anti-aircraft range while the GB glided towards the target under radio guidance.
Technological Innovations and Challenges
As the testing continued, the project led to the development of a television (TV) system known as the SCR-549-T1, later refined into the SCR-550-T1. This system aimed to provide visual guidance for the glide bombs. The TV camera and transmitting equipment were miniaturized for aerial use, with the camera-transmitter unit weighing about 60 pounds. Initial flight tests in early 1942 at Wright Field involved a Culver PQ-8 radio-controlled target drone equipped with the TV system, with the B-23 acting as the controller. However, these early tests revealed several issues, such as interference from the drone’s propeller and inadequate picture resolution, which made it difficult to identify small targets from high altitudes.
Despite these challenges, the tests demonstrated that airborne TV bomb control was feasible, prompting further refinement. By May 1943, an improved TV system, the SCR-550-T2, was tested using a “Bug” drone equipped with a ventral camera-transmitter housing. These tests showed promise, and by August 1943, a successful demonstration of the system was conducted at Muroc, where a YPG-12A drone was used to drop a 500-pound bomb on a target, guided by the TV camera.
The GB-4 and Further Developments
By June 1943, a small number of GB-4 airframes were available for testing with an improved TV system, the SCR-549-T3. This version operated at 300 megacycles and featured separate camera and transmitter units, increasing the weight to 90 pounds. Early tests in August 1943 revealed several issues, including interference and poor TV picture resolution. However, these problems were addressed through soundproofing, better bonding of the airframe, and the addition of a yellow filter and heater to the camera system to prevent fogging.
As development progressed, it became clear that the range of the system needed to be increased for effective combat use. This led to the introduction of a directional antenna on the mother aircraft and a gyrostabilized antenna mount on the GB-4, which eventually resolved many of the technical difficulties. By January 1944, the U.S. Army Air Forces had placed a procurement order for 2,000 GB-4 units equipped with the SCR-549-T3 TV guidance system.
Operational Testing and Deployment
By mid-1944, the GB-4 was ready for limited operational testing. A specialized glide bomb unit, codenamed “Batty” was sent to the 8th Air Force in England for tactical deployment using B-17 bombers. The TV guidance units were also employed in the Castor Program, where war-weary B-17 and B-24 bombers were converted into drones and guided to their targets using the GB-4 system.
These developments marked a significant step forward in the evolution of precision-guided munitions, laying the groundwork for the more advanced “smart” weapons that would become a key component of modern warfare. Despite the challenges and initial limitations, the GB-4 and its successors demonstrated the potential of guided bombs to change the dynamics of aerial warfare.