# JB-4

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The **JB-4**, also known as **MX-607**, was an early American [air-to-surface missile](/source/Air-to-surface_missile) developed by the [United States Army Air Forces](/source/United_States_Army_Air_Forces) during [World War II](/source/World_War_II). Using [television/radio-command guidance](/source/Television_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](/source/Wright_Field) in Ohio,[1][2] the JB-4 was a modification of the [GB-4](/source/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](/source/Ford_PJ31) [pulsejet](/source/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](/source/Plywood) construction,[5] the JB-4 utilised [television](/source/Television)/radio-command guidance, with an [AN/AXT-2](/source/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]

## References

**Notes**

1. Parsch 2024.

1. Ross 1951, p.115.

1. Ordway and Wakeford 1960, p.186.

1. Parsch 2003.

1. Hanle 2007, p.268.

1. Hanle 2007, p.114.

1. *Air Force Magazine*, Volume 31. 1948. [p.25](https://books.google.com/books?id=Rj8PAAAAIAAJ&q=%22JB-4%22).

1. Gunston 1979, p.33.

**Bibliography**

- Gunston, Bill (1979). *The Illustrated Encyclopedia of the World's Rockets & Missiles*. London: Salamander Books. ASIN B002K4M822.
- Hanle, Donald J. (2007). *Near Miss: The Army Air Forces' Guided Bomb Program in World War II*. Lanham, MD: Scarecrow Press. ISBN 978-0-8108-5776-6.
- Ordway, Frederick Ira & Ronald C. Wakeford (1960). *International Missile and Spacecraft Guide*. New York: McGraw-Hill. ASIN B000MAEGVC.
- Parsch, Andreas (2003). ["GB Series"](http://www.designation-systems.net/dusrm/app1/gb.html). *Directory of U.S. Military Rockets and Missiles Appendix 1: Early Missiles and Drones*. designation-systems.net. Retrieved 2011-02-02.
- Parsch, Andreas (2024). ["JB Series"](http://www.designation-systems.net/dusrm/app1/jb.html). *Directory of U.S. Military Rockets and Missiles Appendix 1: Early Missiles and Drones*. designation-systems.net. Retrieved 2011-02-04.
- Ross, Frank (1951). [*Guided Missiles: Rockets & Torpedoes*](https://archive.org/details/guidedmissilesro00ross). New York: Lothrop, Lee & Shepard. ASIN B001LGSGX0.

## External links

- [B - Bombs/Bomb Units](https://web.archive.org/web/20080417022631/http://www.personal.psu.edu/dob104/aviation/us/bomb.html)

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Adapted from the Wikipedia article [JB-4](https://en.wikipedia.org/wiki/JB-4) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/JB-4?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.