Explosions are really messy - they cause debris to be spread over a wide area. They may also cause collateral damage. I want to use implosion instead.
I wish to use a force-field sphere that contains a vacuum. The sphere is used as an invisible booby-trap or mine.
I imagine that such a sphere 'bursting' in mid air would sound very similar to a balloon being burst except that the air would rush inwards.
How big should my vacuum-filled sphere be in order to kill a single human?
Assumption - The person walks into the force-field thus setting it off.
As requested, here is my attempt at illustrating the idea.
Imagine that the rubber of the balloon is an invisible force-field. The air inside the balloon is the vacuum. The whole thing is invisible to the man (unless there is smoke billowing around outside that shows its shape). As soon as the man touches the 'balloon' by placing his hands on it or walking into it, it will activate itself. It does not wait until the man is inside the force field - it is triggered by touch. Therefore the man will presumably be pushed violently into the empty sphere by the air pressure from behind him. This might break his neck, damage his lungs, etc. There could even be a metal pole in the middle that he can see, but he won't be expecting to be thrown violently against it.