🚀 go-pugleaf

From William Logan Lee <bill@extro.ucc.su.oz.au>

In article <C19ny5.3IE@law7.DaytonOH.NCR.COM> MegaZone <megazone@granite.wpi.edu> writes:
>There are API shells which are DU. You do not get 'fusion' with Uranium in any
>case, especially DU. What happens in on contact the KE of the round becomes
>heat, melting the armor and the round and forming a high-temperature molten
>metal jet that slices through the armor. The temp is high enough that on 
>exiting the back of the armor the DU ignites. DU burns extremely hot, and 
>will set off ammo, etc inside the vehicle.

It is not even the heat of the impact that penetrates the armour, just the
plain KE of the impacting round.  High velocity impacts behave very much like
the interaction of two liquids as the pressures generated far exceed the
yield strength of the materials.  Impacts are usually modelled on this
assumption and this appears to be a reasonable model.  After the pressures
fall below their previously extreme levels, the materials again behave like
the solids they are.  They will be very hot from the conversion of KE
into heat, but the heat generated is not the method of penetration.
On penetration, the pressures generated by the impact cause a spray of
material from around the exit point (as well as the remaining projectile
exiting). This material is very hot and ignites on contact with the oxygen
in the air.  Even without the heat, "uranium metal in thin layers ignites
at room temperature within a few minutes after exposure" and "powdered
uranium [is] 'usually pyrophoric'" [_Military and Civilian Pyrotechmics_,
page 32].  This accounts for the incendiary nature of the impact.

The use of DU in a round is dictated by its physical characteristics
(like density) and its availibility, rather than the chemical nature
(such as pyrophoricity).  Non-nuclear countries do quite well with
tungsten penetrators.

Bill Lee