The JB-4, also known as MX-607, was an early American
air-to-surface missile
An air-to-surface missile (ASM) or air-to-ground missile (AGM) is a missile designed to be launched from military aircraft at targets on land or sea. There are also unpowered guided glide bombs not considered missiles. The two most common prop ...
developed by the
United States Army Air Forces
The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...
during
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
. 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,
the JB-4 was a modification of the
GB-4
GB-4 ( Glide Bomb No.4) was a precision guided munition developed by the United States during World War II. GB-4s used a television guidance system with the weapon being steered by a TV bombardier operating a joystick in the launch aircraft.
...
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
file:Pulse Jet Engine.PNG, 300px, Diagram of a valved pulsejet. 1 - Air enters through valve and is mixed with fuel. 2 - The mixture is ignited, expands, closes the valve and exits through the tailpipe, creating thrust.3 - Low pressure in the engi ...
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.
Utilising primarily
plywood
Plywood is a composite material manufactured from thin layers, or "plies", of wood veneer that have been stacked and glued together. It is an engineered wood from the family of manufactured boards, which include plywood, medium-density fibreboa ...
construction,
[Hanle 2007, p.268.] the JB-4 utilised
television
Television (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, ...
/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.
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.]
References
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External links
B - Bombs/Bomb Units
{{US WWII guided bombs
Abandoned military rocket and missile projects of the United States
JB-004
Pulsejet-powered aircraft
World War II guided missiles of the United States