Thread by @noclador

So much nonsense on twitter about the Ground-Launched Small Diameter Bomb (GLSDB)...

Ok, a thread 🧵

GLSDB uses a Lockheed Martin M26 MLRS rocket section with a Boeing GBU-39/B Small Diameter Bomb.
1/n

The M26 was the original rocket used with the M270 to deliver cluster munitions. M26 rockets are being dismantled, which means lots of M26 rocket sections are available.
M26 rockets come in pods of six. Pods that are filled with rockets at Lockheed Martin's plant in Arkansas.
2/n

The GBU-39/B Small Diameter Bomb is made by Boeing. It is an INS/GPS guided glide bomb.

Each BRU-61/A Bomb Rack Unit carries four GBU-39/B (or GBU-39A/B, GBU-39B/B).

Almost all NATO fighters and bombers can deploy GBU-39/B.
3/n

Once released the bombs deploys wings and glide (!) to their target. Glide means the bombs are slow when compared to missiles.

And they are INS/GPS guided bombs, which means they can only (!) hit stationary targets.

And have a good look at the GBU-39/B's steel nose cone.
4/n

Lots of people are tweeting that the GLSDB can hit "moving targets"... yes, but only if you mate the M26 rocket section with a Boeing GBU-39B/B Laser Small Diameter Bomb (LSDB), which has a totally different nose cone, because you have to attach a laser seeker to the bomb.
5/n

Here is a photo of a GBU-39B/B after being released from a AC-130J Ghostrider.

GBU-39B/B are absolutely useless for Ukraine. They are laser-guided SDBs: meaning there needs to be a plane or drone lasering the (moving) target, which means you have a Ukrainian aircraft flying
6/n

at the ideal height for and within range of russian air defense systems.

Forget all the tweets about "moving targets" and "accuracy of 1 meter" - because those specs are for the GBU-39B/B, which Ukraine can't use.

Likewise there is no home-on-jam (HOJ) SDB version.
7/n

HOJ SDB are still in development. They would be used to autonomously strike jamming and radar systems, as does the AGM-88 HARM already given to Ukraine.

And now to the GBU-53/B, which is something different entirely.
8/n

The GBU-53/B or Stormbreaker or Small Diameter Bomb Increment II (SDB II) is made by Raytheon and uses GPS/INS guidance plus either a millimeter wave active radar homing or semi-active laser guidance or infrared homing seeker.
It's a completely new weapon system.
9/n

GBU-53/Bs are also way more expensive than GBU-39/B.

And as said before they are manufactured by Raytheon, while the GBU-39/B is made by Boeing, and the M26 rocket sections are made by Lockheed Martin, and the GLSDB was developed by Saab/Boeing.
10/n

What Ukraine will get are GPS/INS guided GBU-39/B on M26 rocket sections, which carry less explosive than a GMLRS M31 rocket and without the added punch of a supersonic GMLRS missile slamming into a target.

M31 GMLRS: 51 lb PBX-109
GBU-39/B: 36 lb AFX-757
11/n

Last but not least GLSDB isn't even in production... so before they can show up in Ukraine GLSDB has to enter production.

M26 rocket sections exist, GBU-39/B bombs exist - but the interstage connectors to mate these two need to be built. And the resulting rockets have to be
12/n

sent to Camden in Arkansas, where Lockheed Martin will mount them into M270/M142 HIMARS pods.

Yes, the GLSDB is a great weapon and will help Ukraine. But it will take some time to arrive and people need to stop mixing up GBU-39/B specs with GBU-39B/B and GBU-53/B specs.
13/n

Last but not least: the GBU-39A/B Focused Lethality Munition is a GBU-39/B variant with a carbon-fiber casing for ultra low fragmentation and a DIME explosive for a more focused-blast - both are used to reduce collateral damage.
Ukraine won't get it and doesn't need it.
14/end