Over on the Brown Moses blog Richard M. Lloyd has a lengthy examination of the technology behind the so-called barrel bombs as used by the al-Assad forces in Syria’s civil war. He makes some crucial points about the primitive nature of these munitions:
“The Syrian government over the last year has supplemented it’s traditional conventional air campaign with cheap weapons that have been referred to as Barrel Bombs (BB). These Do It Yourself (DIY) weapons are derived from low cost cylinders that are filled with explosive, fuel and irregular shaped steel fragments. These DIY bombs are manually deployed by soldiers from Russian HIP helicopters. The idea is these helicopters can roam around Syrian neighbourhoods and drop these weapons with more accuracy than firing aircraft rockets.
Barrel bombs designs that are observed though social media demonstrate that the Syrian government designed these barrel bombs with a fuse wick that requires a heat source (matches, cigarettes, cigars) to ignite. The Syrian government must have made the simple calculation that if the helicopter is at a known altitude (H) and the fuse wick burns at a known rate (b˙) then the time that it takes for the bomb to detonate is t=H/b˙. However, this simple equation that computes the time before detonation is false. Whoever designed these barrel bombs does not understand that there is a 10% burn rate error in the fuse wick. They also don’t understand that if the helicopter is not at the designed altitude it will affect the time of fall. In conjunction with these errors, they did not take into account the barrel size, mass, barrel bomb L/D ratio, tumble rate, drag effects, wind speed as well as the time it takes the soldier to deploy the bombs once it has been lit inside the helicopter.”
One consequence of this poor design and deployment was the failure of many early barrel bombs to explode. In other cases the explosions took place well above the ground with little direct damage to the presumed targets below. Recently regime technicians have countered this by fitting crudely engineered fins to one end of the barrels with impact fuses fitted at the other. In theory this causes the munitions to fall “nose first” detonating upon hitting the ground though again this has proved highly problematic raising something of a mystery as to why the engineering of these weapons is so poor. Weighting the barrel bombs with shrapnel at the fuse-end or using a pressurised fuel-explosive mix that would burst upon impact would seem a more effective design. Alternatively given the manner in which they are being used deploying a small drogue parachute or streamer to arrest and guide the fall would more effectively aid the trajectory and detonation of the munitions. However where these “terror weapons” (as we may fairly summarise them) have been successfully deployed the results have proved deadly.