In the end of Avengers (2012) movie, S.H.I.E.L.D. fired a nuke towards Manhattan to take out the portal and Chitauri army. Also, it looked like the nuke was precisely targeted to Stark Tower on which portal device was stationed.
Although, Iron Man was able to intercept it and change its trajectory, the nuke still reached its destination i.e. Stark Tower (Iron Man took the nuke into the portal which was directly above Stark Tower). Why didn't the nuke detonate upon reaching its destination?
Note: A nuke trigger is generally GPS location, timer, switch etc, but it's never impact because there's no incentive of impact (impact can't trigger nuclear reaction and it can even damage circuitry).