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GBU-12 Very Short Range?


MARLAN_
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Is this normal?

 

GBU-38 (500lbs) can be dropped 12-18nm or so away, while GBU-12 (also 500lbs - with appears to be bigger fins) only flies about 5nm.

 

This is also slant range, so the closer you are the less "ground" range it actually is, GBU-12 is dropped nearly overhead, seems wrong, like I'm dropping a parachute bomb.

 

I don't have data to back it up, it just seems very wrong.

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3 hours ago, MARLAN_ said:

Is this normal?

 

GBU-38 (500lbs) can be dropped 12-18nm or so away, while GBU-12 (also 500lbs - with appears to be bigger fins) only flies about 5nm.

 

This is also slant range, so the closer you are the less "ground" range it actually is, GBU-12 is dropped nearly overhead, seems wrong, like I'm dropping a parachute bomb.

 

I don't have data to back it up, it just seems very wrong.

 

The GBU-38 has a much more sophisticated flight profile and guidance scheme to allow for longer ranges. The GBU-12 on the other hand is fairly basic using bang-bang guidance that doesn't lend itself to longer ranges (bang-bang is fairly crude and inefficient).

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Posted (edited)
On 5/16/2021 at 4:44 AM, MARLAN_ said:

Is this normal?

 

Yes.

 

Quote

GBU-38 (500lbs) can be dropped 12-18nm or so away, while GBU-12 (also 500lbs - with appears to be bigger fins) only flies about 5nm.

 

 

Like Northstar98 said, the GBU-38 flies a carefully controlled and plotted course.  It has a single moving fin which controls its direction and it needs to be very efficient.

 

The GBU-12 uses bang-bang navigation which means the control surfaces use full deflection for any correction.  So, each time the bomb has to correct its aimpoint it's like deploying an airbrake.  Think of it this way:  Imagine you're flying your favorite plane and your only means of controlling it is to deflect the controls all the way.  It doesn't matter how little you move the stick, you get full deflection immediately.

 

Why is it like this?  It was easy/cheap to do it, and this guidance kit is old.   New guidance kits use proportional navigation, allowing the bomb to glide much farther.

 

Quote

I don't have data to back it up, it just seems very wrong.

 

This is why you should have data 🙂


Edited by GGTharos
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50 minutes ago, GGTharos said:

New guidance kits use proportional navigation, allowing the bomb to glide much farther.

 

I wouldn't say it "gliding" as it is not a glide bomb. It is more of a "better controlled ballistic free falling". 

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Posted (edited)
On 5/17/2021 at 6:24 PM, GGTharos said:

 

Yes.

 

 

Like Northstar98 said, the GBU-38 flies a carefully controlled and plotted course.  It has a single moving fin which controls its direction and it needs to be very efficient.

 

The GBU-12 uses bang-bang navigation which means the control surfaces use full deflection for any correction.  So, each time the bomb has to correct its aimpoint it's like deploying an airbrake.  Think of it this way:  Imagine you're flying your favorite plane and your only means of controlling it is to deflect the controls all the way.  It doesn't matter how little you move the stick, you get full deflection immediately.

 

Why is it like this?  It was easy/cheap to do it, and this guidance kit is old.   New guidance kits use proportional navigation, allowing the bomb to glide much farther.

 

 

This is why you should have data 🙂

 

 

Afaik as soon as a laserpoint is detected the fins deflect fully in any one direction to minimize offset. then it's going fully into the other direction. So it's really, really bad 🙂 And one of the reasons why you don't lase too early.

 

 

  

On 5/17/2021 at 7:16 PM, Fri13 said:

 

I wouldn't say it "gliding" as it is not a glide bomb. It is more of a "better controlled ballistic free falling". 

 

Doing control inputs in a very economic way.


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44 minutes ago, deadpool said:

Doing control inputs in a very economic way.

 

But it is more expensive than a GBU-12..... 😉

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