| JB-4 | |
|---|---|
| Type | Air-to-surface missile |
| Place of origin | United States |
| Service history | |
| In service | 1945 |
| Used by | United States Army Air Forces |
| Specifications | |
| Weight | 3,000 pounds (1,400 kg) |
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| Warhead | High explosive |
| Warhead weight | 2,000 pounds (910 kg) bomb |
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| Engine | Ford PJ31 pulsejet 660 lbf (2.9 kN) |
| Wingspan | 12 feet (3.7 m) |
| Operational range |
75 miles (121 km) |
| Speed | 445 mph (716 km/h) |
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.
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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 PJ31 pulsejet 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]
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]
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