You misunderstand my friend.
It doesn't increase the burn rate of a given powder but increases the burn rate of a MASS of that given powder. The actual speed of powder burn is not increased.
And Digger yes you are correct as ever. Through my poor explanation I mean that the thin walled spheres increased the surface area (I believe in maybe similar proportions to smaller grains?) as there is no BP contained within.
Is that better?
Sounds good to me.
As you say the linear burning velocity is constant (neglecting pressure effects on burn rate as the pressure increases would be applied to whatever size of particle you choose) therefore for example if you have a 1cm cube and the burn rate is 1cm per second and you light all sides at once then it would take 1/2 second to completely burn the mass. However if you cut that cube into 8 0.5cm cubes and light all the surfaces at once then the mass would burn in 1/4 of a second.
Hence with a coating on rice crispies or whatever you choose then the coating is very thin so it will consequently be consumed quickly even though the linear burning velocity has not changed.
Edited by digger, 06 November 2008 - 10:13 PM.