|Keep It Simple, Stupid|
How does one 'explode' anything 'very, very gently'?
For what it's worth, you're exactly right...nothing has to 'explode'. It really is all kinetic energy...the closing velocity between two objects at the altitudes discussed are about 14 km/sec (or a little under 14 miles/sec).
About 15 years ago I was associated with a project to test hypervelocity impacts on the ground...by hypervelocity we meant velocities in excess of about 2 km/sec...which was the most we could create with very specialized devices called rail-guns (which were electromagnetic accelerators that could fire a small piece of steal (about the size of a thimble, but solid rather than hollow like a thimble) by a long series of elecromagnets that would successively accelerate the thimble faster and faster). They fired it into an embankment of heavy clay dirt...to see what it would do (seems like the old saying 'The difference between boys and men are the cost of their toys').
It basically left a crater about the equivalent of 50 to 60 feet across and about 10 to 15 feet deep...from a heavy thimble!
Another annecdote is the infamous (well...infamous in my business) paint fleck (about 2 mm square and about a few thounsands of an inch thick) that struck one of the space Shuttle's forward windows. Those windows are about 4-6 inches thick specially made glass-like material. The collision, estimated at about 4-5 km/sec gouged out a crater about 1/2 way through the window and was about 4-5 inches across at the surface of the window.
At 14 km/sec...the collision doesn't just vaporize most of the matter...it actually creates an ionized plasma out of much of the matter. The rest is varying degrees of dust and debris of a surprisingly large variety of shapes and sizes.
So 'explosions' are of no particular value...the kinetic energy of the collision is plenty.
ack Albuquerque, NM