Flow seems off

Augst 6th 8:15 am, the Enola Gaye banks away after dropping its payload, a device with a power unheard of and power unseen, until now. As this device falls towards the earth 11 miles in the air, a timer has just begun. Falling for 43 seconds, an internal clock along with the barometric sensors start the reaction. Firing a uranium bullet down a barrel impacting a tub of uranium, causing a chain reaction of nuclear fusion and fission. At two thousand feet, the uranium goes critical mass, and the device explodes. A flash out of nowhere blinding anyone who looks at it, the sky burning, set ablaze charring buildings and anyone it finds. A shockwave following leveling the city and anything in its path, and all that is left is the city is charred shadows of people caught in the open, destroyed buildings and a mushroom cloud eleven miles high

This is for a process analysis essay for my Comp 1 class. The topic is about how nuclear weapons work.

How can I improve this introduction to my essay The remaining paragraphs would be:

How is the material weaponized

Detonation types

Ground burst vs air burst

Fallout

Edit: Grammer and spelling mistakes will be fixed during class