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A MOAB in John Deere Green

22 July 2011

A MOAB in John Deere Green

MOAB is for Massive Ordinance Air Bomb — photo by Joe May

Probes contain the fuzes ensuring detonation above ground surface — photo by Joe May

The Air Force Armament Museum has a Massive Ordinance Air Bomb (MOAB), officially designated the GBU-43/B, on exhibit next to the museum entrance.  This is an asymmetric warfare weapon — one that can only be used when air supremacy has been achieved. No USAF bomber aircraft can load the MOAB, instead it is deployed by a C-130 flying high in the neighborhood of 300 mph (480kph) — easy prey for a SAM or a fighter aircraft. MOAB is large, 3o feet in length, armed with 18,700 pounds (8500kg) of H6 explosive — a general purpose explosive meant to create a blasting effect.

The MOAB is carried and deployed from a cradle — photo by Joe May

The MOAB is satellite guided with a system of inertial gyroscopes controlling Belotserkovskiy* grid fins and stub wings for stabilization. This ordinance is meant to create a blast effect — a very large effect — and is likely best used against minefields, cave entrances, possibly canyons, as well as creating instant landing zones and firebases. The designer was Albert L. Weimorts, a Floridian from DeFuniak Springs, who passed away in 2005 not long after the MOAB was first tested.

The controlling fins and tail unit housing the GPS, gyroscopes and fin actuators — photo by Joe May

Closer view of the Belotserkovskiy grid fins — photo by Joe May

Closer view of the stabilizing stub wings — photo by Joe May

Deploying the MOAB appears to be a simply matter — a drogue parachute pulls the cradled MOAB out of the C-130 along the rear cargo ramp, then the MOAB falls free from the cradle and is guided by the GPS/control fin system to the target’s coordinates — ultimately exploding just above the ground surface destroying what is in the path of an expanding overpressure wave. The devil may be in the details, however. Assuming the MOAB has a 3 mile (5.8km) radius with the C-130 traveling at 300 mph (480kph) means that the time window for an accurate drop is 36 seconds. Then the wind velocity and drift must be accounted for as well as the target approach angle limitations. It appears the MOAB is a special purpose weapon the military has in the inventory should the proper contingency arise, but the conventional smart bombs provide greater standoff range and can generally be delivered with more accuracy.

Why the John Deere green? The color did not come about for any specific reason except the the weapon was built in accordance with such a short timetable that it simply was the only color available the weekend of construction — so reports the Air Force news here.


* Belotserkovskiy grid fins are more efficient that planar fins in subsonic and supersonic applications, but problematic at transonic speeds. Essentially they are a group of small fins which act collectively as a much larger fin but making but with a smaller overall area. The advantages are more efficient stowage, less torque required to actuate the fins so less motive power needed and a smaller resulting tail size, also better performance at high angles of attack so better turning potential.

2 Comments leave one →
  1. Marty Davis permalink
    23 July 2011 14:46

    I assume the twin “rods” that are projecting from the front are devices to sense ground contact and initiate explosion. Is this correct?

    • travelforaircraft permalink
      23 July 2011 16:19

      I think you are right but I couldn’t find a direct reference.

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