<Serge77 - My Rocket Workshop >
Consequence of Accidental Ignition
Summary: the task is to melt KNO3-sorbitol propellant, heat it to 150-160° C and ignite it in hot liquid state from the top surface.
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. Top surface of the salt bath was covered with aluminum foil for reducing of heat loss.
After propellant was heated to 150° C, heat rate become very low, so I decided to stop heating at that point.
Prepared igniter: two-layer peace of secondary ignition composition.
After propellant melted and reach 151° C salt bath and aluminum pan were quickly transferred from the burner to the middle of test area. Molten propellant had appreciably thinner consistency, than at 115° C. Igniter was placed above the propellant surface and the RED BUTTON was pressed.
VIDEO, 1.1 MB
Propellant temperature 150° C.
Ambient temperature 15° C.
Propellant depth 33 mm.
Diameter of propellant surface 135 mm.
Burn time ~1.4 s.
Fireball height is about 2 m.
Fireball width is about 1.5 m.
There was almost no wind at the time of experiment, but scattering of burning propellant drops was highly asymmetric. There are many large footprints from flying large gobs of burning propellant at the distance up to 0.5 m.. Maximal scattering of burning drops was 1-1.5 m, but a little small drops were found as far as 2-2.5 meters downwind.
Aluminum foil almost completely disappeared form top surface of the salt bath. There are very little residue in the aluminum pan.