<Serge77 - My Rocket Workshop >
Consequence of Accidental Ignition
Summary: the task is to melt KNO3-sorbitol propellant and ignite it in hot liquid state from the bottom of the pan.
KNO3: reagent grade "pure for analysis". Moisture content 0.1-0.2%. It was milled with coffee mill, crystals measured 50 microns to 300 microns.
Sorbitol: pharmaceutical grade. Moisture content 0.2-0.3%.
Experiment setup was the same as in the first test.
Four metal rods 1m height were placed at 1m distance from each other for the scale purposes.
Sheets of office paper were pinned on the ground at 0.5m distance from each other.
1 kg batch of thoroughly mixed powdered KNO3-sorbitol propellant mixture was placed in aluminum pan. Small propane burner was used as heat source, with salt bath and aluminum pan at the top, as in the third test.
Igniter was bare nichrome wire (diameter 0.2 mm, length 20 mm), attached to the rigid copper wire. 18V lead battery was used as voltage source.
After propellant melted salt bath and aluminum pan were quickly transferred from the burner to the middle of test area. The temperature of molten propellant was 117° C, it had usual pourable consistency. Igniter was placed under the propellant mass and the RED BUTTON was pressed. It took about 10 seconds after this moment to heat nichrome wire to ignition point of propellant.
VIDEO, 2 MB
Propellant temperature 117° C.
Ambient temperature 14° C.
Propellant depth 32 mm.
Diameter of propellant surface 135 mm.
Burn time 5 s.
Fireball height is about 2 m.
Fireball width is about 1 m.
There was small wind at the time of experiment, the maximal scattering of burning propellant drops was: 1 m downwind, less then 0.5 m upwind, 0.5 m at other sides.
There are very little residue in the aluminum pan.
Small drops and one burn-through hole:
Small drops and several burn-through hole: