The JB-4, also known as MX-607, was an early American air-to-surface missile developed by the United States Army Air Forces during World War II. Using television/radio-command guidance, the JB-4 reached the flight-testing stage before being cancelled at the end of the war.
Design and development Developed under the project code MX-607 at Wright Field in Ohio,Ross 1951, p.115. the JB-4 was a modification of the GB-4 glide bomb,Parsch 2024. which had entered service with the U.S. Army Air Forces in 1944.Parsch 2003. Powered by a Ford PJ31 pulsejet engine, the JB-4 was intended to give an improved standoff range as opposed to its unpowered predecessor. In addition, the addition of an engine made the missile capable of being ground-launched as well. However the requirement to carry fuel for the engine meant that the size of the JB-4's warhead was limited to , compared to the bomb that formed the core of the GB-4.Hanle 2007, p.114.
Utilising primarily plywood construction,Hanle 2007, p.268. the JB-4 utilised television/radio-command guidance, with an AN/AXT-2 transmitter broadcasting a television signal from a camera in the missile's nose to a remote operator. The operator, viewing the transmitted picture, would then transmit commands to the missile via radio, correcting the missile's course to ensure striking the target.
Operational history The JB-4 entered the flight testing stage in January 1945.Air Force Magazine, Volume 31. 1948. p.25. The missile demonstrated the ability to cruise at over ;Gunston 1979, p.33. however, the television-guidance concept suffered from the limitations of the technology of the time, the pictures being difficult to make out in anything except completely clear weather. The missile also suffered from reliability issues; these, combined with the end of World War II in August 1945, resulted in the termination of the project, with none of the JB-4s built seeing operational service.Ordway and Wakeford 1960, p.186.
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B - Bombs/Bomb Units