Editing Nuclear weapon design (section)

===Gun-type===
It is inherently dangerous to have a weapon containing a quantity and shape of fissile material which can form a critical mass through a relatively simple accident. Because of this danger, the propellant in Little Boy (four bags of [[cordite]]) was inserted into the bomb in flight, shortly after takeoff on August 6, 1945. This was the first time a gun-type nuclear weapon had ever been fully assembled.{{Citation needed|date=June 2021}}

If the weapon falls into water, the [[neutron moderator|moderating]] effect of the [[light-water reactor|water]] can also cause a [[criticality accident]], even without the weapon being physically damaged. Similarly, a fire caused by an aircraft crashing could easily ignite the propellant, with catastrophic results. Gun-type weapons have always been inherently unsafe.{{Citation needed|date=June 2021|reason=Safing schemes for the reliable earth penetrator warhead describes safing schemes for gun-type weapons}}