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Bomb aerodynamics

This is a discussion on Bomb aerodynamics within the Air Force & Aviation forum, part of the Global Defense & Military category; why the shape of JDAM and laser guided bomb are so different ? their wing shape , their nose , ...


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Old April 15th, 2013   #1
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Bomb aerodynamics

why the shape of JDAM and laser guided bomb are so different ? their wing shape , their nose , is there any advantages or disadvantages related to each shape ?
at first i thought their different in their appearance is because of their seeker however the paveway IV ( GBU-12 added GPS ) and the GBU-54 ( GBU-38 added laser seeker ) while both of them use laser guidance and GPS guidance at the same time they have very different shape why ?
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Old April 16th, 2013   #2
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Originally Posted by moon_light View Post
why the shape of JDAM and laser guided bomb are so different ? their wing shape , their nose , is there any advantages or disadvantages related to each shape ?
at first i thought their different in their appearance is because of their seeker however the paveway IV ( GBU-12 added GPS ) and the GBU-54 ( GBU-38 added laser seeker ) while both of them use laser guidance and GPS guidance at the same time they have very different shape why ?
Difference in sequence of capabilities being added and available technology.

The laser guided Paveway series of bombs were developed using 1960’s technology as a laser guided bomb, which required the seeker to be in the nose, so it was easier just to put the rest of the guidance system there. The GPS guidance was added as an upgrade to existing guidance packages after 2005 to provide an all weather capability.

The JDAM was developed using 1990’s technology as a GPS guided bomb which would work best if the antenna for the GPS was pointing upwards to get a strong signal just before impact, so it was natural to locate all the systems in the tail. Laser homing in the form of a nose cap was added after 2005 to improve terminal guidance. Because all the components are located in the tail the JDAM is consequently much more streamlined than the Paveway and uses strakes instead of fins for lift.
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Old April 18th, 2013   #3
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Difference in sequence of capabilities being added and available technology.

The laser guided Paveway series of bombs were developed using 1960’s technology as a laser guided bomb, which required the seeker to be in the nose, so it was easier just to put the rest of the guidance system there. The GPS guidance was added as an upgrade to existing guidance packages after 2005 to provide an all weather capability.

The JDAM was developed using 1990’s technology as a GPS guided bomb which would work best if the antenna for the GPS was pointing upwards to get a strong signal just before impact, so it was natural to locate all the systems in the tail. Laser homing in the form of a nose cap was added after 2005 to improve terminal guidance. Because all the components are located in the tail the JDAM is consequently much more streamlined than the Paveway and uses strakes instead of fins for lift.
so what the advantages of each designed in term of accuracy ,penetration , ability to hit moving target ? ( i mean does the aerodynamic different offer the the different capability as well )
P/S : in another forum there was a guy saying that due to aerodynamic JDAM design often get problem with vertical development and Paveway series get problem with stalling but i dont really understand there terms can anyone explain it more clear
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Old April 19th, 2013   #4
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so what the advantages of each designed in term of accuracy ,penetration , ability to hit moving target ? ( i mean does the aerodynamic different offer the different capability as well )
P/S : in another forum there was a guy saying that due to aerodynamic JDAM design often get problem with vertical development and Paveway series get problem with stalling but i dont really understand there terms can anyone explain it more clear
The kits have no effect on the penetration capability and are often standard equipment because the smaller bursting charge in penetrating warheads requires greater accuracy to be effective.

In terms of accuracy, GPS guidance is an all weather capability but is limited to stationary targets. Laser guidance is more accurate and can hit moving targets, but requires that the target be illuminated by a coded laser beam, so it is a clear weather only system, and generally requires the aircraft to overfly the target. The latest version of both JDAM and Paveway gives them both capabilities.

Not sure what is meant by vertical development, but if he meant the ability to strike vertically downward, there is no problem. Within the limits of the available kinetic energy and control surface the trajectory of a JDAM is programmable. Also, because the JDAM is largely unaffected by the accuracy of the launch trajectory, it is common to use ‘toss bombing’ techniques where it is launch it upward on a ballistic trajectory toward the target and come down on it. This also allows the aircraft to avoid overflying the target and leave as fast as possible.
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Old April 19th, 2013   #5
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The true reason they are shaped differently is that the Paveway was designed to be a laser guided bomb. The JDAM is a "kit" added to an existing dumb bomb which was designed to free fall without guidance.
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Old April 20th, 2013   #6
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The true reason they are shaped differently is that the Paveway was designed to be a laser guided bomb. The JDAM is a "kit" added to an existing dumb bomb which was designed to free fall without guidance.
The Paveway is a kit that is bolted to an existing dumb bomb, same as the JDAM.

The SDB "Small Diameter Bomb" is the one that was designed from the ground up as a guided bomb.
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Old April 20th, 2013   #7
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The Paveway is a kit that is bolted to an existing dumb bomb, same as the JDAM.

The SDB "Small Diameter Bomb" is the one that was designed from the ground up as a guided bomb.
My error, thanks for the correction!
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