The real problem with these explosions is the problem that condemned the fates of Chernobyl and Fukushima--radiation poisoning.
No. No, no and no. I am sorry but Greenpeace and every other anti-nuclear organisation has been lying to you. Radiation is not a the Super Villain Deluxe™ that kills everything "for millions of years".
You are radioactive. The food you eat is radioactive. The ocean you take a swim in is radioactive. The ground you stand on is radioactive. The sky above your head; the deep space you look into at night is shining radiation at you.
Did you know that in the Gulf of Mexico alone there is 3 million tons of Uranium? And that is not even near the most radioactive part of that water.
You live with, breathe, eat and — pardon the profanity — shit radioactive substances your entire life.
It is with radiation as with everything else: the dose makes the poison.
And - yes - it is true that about half of those that did die from the atomic bombings of the two Japanese cities in 1945 died from radiation. But the vast majority of those were from the direct radiation at the moment of detonation. The fallout was small, and made for very few residual cases that died of long-term effects. The notion that a nuclear bomb must cause dangerous amounts of radiation to linger, is false.
As proof... this is Hiroshima today:
Ground zero is at the domed structure to the left
Fallout after a nuclear explosion depends on two things:
- The yield of the bomb.
- The proximity to the ground.
A ground burst will produce intense fallout, as was for instance fatally found at the Castle Bravo test. But an air burst, where the fireball only lightly touches the ground... while intensely devastating and causing acute radiation sickness in those caught out in the open by the blast of radiation at the moment of detonation, leave relatively little fallout.
And yes... the "radioactive wasteland" trope is so over-used it sickens me. But in reality you can use use nuclear explosions without turning everything into an irradiated desert where nothing can live. The key is air bursts. About half will die from the heat and blast effects, about half die from the direct radiation at the moment of detonation... and less than 10% die later from the residual radiation.
To answer the letter to your question and not just kill your faulty premise: what Separatrix said: projectiles from space at speed of Mach 10 or more will make some big booms.
Chelyabinsk meteor... Damage starts at 1m 45s ...and this was just a relatively "light" touch.