In the movie, The Sum of All Fears, a nuclear bomb goes off in Boston, and as a man is flying in a helicpoter to the location of the bomb after finding out there is a bomb, it explodes. He is flying over a rural area close to Boston, and as it goes off, an extremely powerful shock wave follows, and it takes the chopper down like hitting a tennis ball with a racket (somehow the guy survives, but the pilot doesn’t). Also with good effects of the shockwave flattening parts of the land.
My question is, do nuclear explosions really have a powerful shockwave like that? Do they have any shockwave at all?
All explosions create waves of pressure in the air. With small explosions, these waves are weak and we perceive them as sound. With gigantic explosions, they are strong enough to knock down buildings. That’s my layman’s understanding of it. I think these pressure waves are responsible for most of the immediate damage done by any large bomb.
Here’s a pretty detailed discussion of nuclear explosions:
A nuclear device detonated in the atmosphere will create a strong blast wave. It could certainly damage or destroy a helicopter. The bit about it knocking down the helicopter “like hitting a tennis ball with a racket” is suspect. If the pilot was lucky, he could auto-rotate and make a controlled landing. If not, I would expect the helicopter to just fall from the sky, like any other lump of metal without wings.
You get a preceding rush of fast moving air, which is air being pushed away and compressed from the blast area, then you get the high speed shockwave the blast itself, which will knock down buildings, and then you get a decompression wave, the air rushing back the other way, and this latter can finish of structures already weakened.
Pretty much the entire point of a nuclear weapon is the shock wave. The thermal effects are nice too.
The shock wave is measured in psi of overpressure. I’ve talked to someone who experienced a blast overpressure of about 1 psi. He said it felt like getting punched in the chest pretty hard. It’s been a while since I’ve read about this subject, but it doesn’t take much more than that before the shock wave starts ripping your lungs apart as it passes through you (maybe 4 or 5 psi or so). For big explosions, the blast overpressure can be a few thousand psi. It drops off rapidly as you move away from the center of the blast though.
Likewise been a while since I had a copy of “Blast effects of nuclear weapons”, a government publication detailing the effects of these devices, but IIRC a few tens of psi overpressure suffices to destroy most common types of structure and around 100psi overpressure will take care of reinforced structures. By way of example the live loads that buildings are designed around (such as wind loads) are typically measured in a few tens of psf (pounds per square foot) rather than pounds per square inch.
To confirm Valgard’s memory, Glasstone and Dolan’s The Effects of Nuclear Weapons (multiple editions; I’m looking at the 1980 first UK one) reckons - see Table 5.145 - that approximately 10 psi of overpressure will wreck any non-reinforced structure. For reinforced buildings, they consider up to 30 psi - see the first entry in Table 5.139a.
You don’t even need a nuclear explosion to have a very big and destructive shockwave (duh :)). In may of 1988 a jet fuel factory in Henderson, Nevada exploded. The perchlorate caught and the entire plant blew up in two very spectacular explosions. The biggest was equivalent to 1.5 million tons of TNT.
That actually has the video (Quicktime) on that page, as well as two downloadable versions that show very clearly what the explosion looks like. You can see the shockwave spread out, kicking up a circle of dust along the desert floor that finally hits one of the plant buildings, rippling the roof, and knocking down the plant. Towards the end of the video they show the big explosion at 20% speed and the flash is bright enough it overpowers the camera (causing it to darken exposure), and you can also see when the decompression wave causes the column of smoke to pull back and rush upwards.
The plant wasn’t too close to Henderson but it was close enough it cause $70 million in damages.
From your cite, 1.5 million pounds of TNT, which is 750 tons, or 0.75 kilotons. The first atomic bombs were on the order of 15 or 20 kilotons; 1.5 megatons (1.5 million tons) would be a good-sized H-bomb.