Mother of all bombs: How powerful is US mega-weapon?

The US military has just dropped its largest conventional (that is non-nuclear) bomb for the first time in combat, on Afghanistan's eastern province of Nangarhar.

The GBU-43/B Massive Ordnance Air Blast Bomb (MOAB) - or, in military speak, Mother of All Bombs - was launched on Thursday.
The target was said to be a network of tunnels operated by the so-called Islamic State in Achin district.
As a non-nuclear weapon, use of the MOAB does not necessarily require approval by the US president 
It is a huge weapon - a 30ft (9m), 21,600lb (9,800kg), GPS-guided munition that is dropped from the cargo doors of an MC-130 transport plane and detonates shortly before it hits the ground.
The MOAB falls from the aircraft on a pallet, which is then tugged aside by a parachute allowing the weapon to glide down, stabilised and directed by four grid-like fins.
Its principal effect is a massive blast wave - said to stretch for a mile in every direction - created by 18,000lb of TNT.
The bomb's thin aluminium casing was designed specifically to maximise the blast radius.

The "bunker-busting" bomb is designed to damage underground facilities and tunnels.
The weapon was developed for use in the Iraq war - at a reported cost of $16m (£13m) each - and was first tested in 2003, but never used in action - until now.
And yet, the MOAB is not the US military's heaviest non-nuclear bomb.
That distinction belongs to the Massive Ordnance Penetrator, or MOP, an even bigger bunker-buster which weighs a colossal 30,000lb.
Russia has developed its own massive conventional bomb, nicknamed the Father Of All Bombs. The FOAB is a kind of fuel-air bomb, technically known as a thermobaric weapon.
Thermobaric bombs generally detonate in two stages: a small blast creates a cloud of explosive material which is then ignited, generating a devastating pressure wave.
A significant part of the effect of weapons like the MOAB is said to be psychological - to instil terror by the massive force of the blast.
Its development followed the use of similar weapons including the BLU-82 Daisy Cutter, a 15,000lb bomb designed in part to flatten a section of forest to carve out a helicopter landing pad.
The MOAB was developed by the Alabama-based aeronautics company Dynetics.