"George E. Cawthon" wrote in message ...
Dan Thomas wrote:
In World War I the French used "flechettes" against the troops in
the trenches. These were machined steel darts a few inches long, with
flutes cut into the aft end to stabilize and rotate them. They were
dropped from airplanes at a considerable height, hundreds at a go, and
would reach transsonic speeds (one source claimed supersonic speeds,
but I think the drag would preclude that)before they hit the ground or
some unfortunate soldier. Helmets weren't much protection; they were
sharp.
The density of air at 18,000 feet is half of that at sea level.
Anything dropped from this altitude is going to accelerate much more
quickly, as drag is a function of the square of any increase in speed.
Half of the density should, I figure, cut the drag to a quarter.
Increasing drag at lower altitudes would slow the acceleration, but a
much higher final velocity should be possible for a dart.

Dan

You might be surprised about how low the terminal speed
would be, but without any data there is no point in
speculation. You did say the they were several inches long
so they would weight much more than a bullet and with a
point they could possibly have penetrated a helmet. In
comparison, it is highly unlikely that a 150 grain bullet
traveling at 300 fps would penetrate a helmet, just a dent.
Weight is everything at low speeds, an arrow shot into the
sky and falling down could penetrate you because of it's
much greater weight.


A link to some basic flechette info:
http://en.wikipedia.org/wiki/Flechettes

Other links pointed out the modern use of flechettes fired from
guns, in canisters, in Vietnam and Israel. These are much smaller,
maybe an inch or so.
I couldn't find a link giving terminal velocity for the WWI
variety, but there must be something online somewhere.
Dan