Developed under the project code MX-607 at Wright Field in Ohio,[1][2] the JB-4 was a modification of the GB-4 glide bomb,[1][3] which had entered service with the U.S. Army Air Forces in 1944.[4] Powered by a Ford PJ31pulsejet engine, the JB-4 was intended to give an improved standoff range as opposed to its unpowered predecessor.[1] In addition, the addition of an engine made the missile capable of being ground-launched as well.[1] However the requirement to carry fuel for the engine meant that the size of the JB-4's warhead was limited to 750 pounds (340 kg),[5] compared to the 2,000 pounds (910 kg) bomb that formed the core of the GB-4.[6]
Utilising primarily plywood construction,[5] 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.[1]
Operational history
The JB-4 entered the flight testing stage in January 1945.[1][7] The missile demonstrated the ability to cruise at over 400 miles per hour (640 km/h);[8] 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.[4] 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,[1] with none of the JB-4s built seeing operational service.[3]
Gunston, Bill (1979). The Illustrated Encyclopedia of the World's Rockets & Missiles. London: Salamander Books. ASINB002K4M822.
Hanle, Donald J. (2007). Near Miss: The Army Air Forces' Guided Bomb Program in World War II. Lanham, MD: Scarecrow Press. ISBN978-0-8108-5776-6.
Ordway, Frederick Ira; Ronald C. Wakeford (1960). International Missile and Spacecraft Guide. New York: McGraw-Hill. ASINB000MAEGVC.
Parsch, Andreas (2003). "GB Series". Directory of U.S. Military Rockets and Missiles Appendix 1: Early Missiles and Drones. designation-systems.net. Retrieved 2 February 2011.
Parsch, Andreas (2024). "JB Series". Directory of U.S. Military Rockets and Missiles Appendix 1: Early Missiles and Drones. designation-systems.net. Retrieved 4 February 2011.
