if you want to spawn the nuke without a plane you can.

First place an helipad with a variable ex : "helipad1"

after double click on the helipad and add this : "[nukepos] execVM "\Plane_CAS_01\data\scripts\nuclear\detonation.sqf" into the init of helipad1

after replace "nukepos" by the helipad variable name so "helipad1" so the code is : [helipad1] execVM "\Plane_CAS_01\data\scripts\nuclear\detonation.sqf"

now when you will start your mission the nuke will explode.