Contents 1 Cold Cast KNO3 / Sugar 1.1 Ratings 2 Formulations 2.1 F1 2.2 F2 2.2.1 Mechanical - Poor 2.2.2 Burn - Good 2.3 F3 2.3.1 Mechanical - Mediocre 2.3.2 Burn - Poor 2.4 F4 2.4.1 Mechanical - Mediocre 2.4.2 Burn - Poor 2.5 F5 2.5.1 Mechanical - Poor 2.5.2 Burn - Poor 2.6 F6 2.6.1 Mechanical - Good 2.6.2 Burn - Good 2.7 F7 - Rammed 2.7.1 Mechanical - Good - Too much work 2.7.2 Burn - Good

Cold Cast KNO3 / Sugar

In wintertime it is too cold to go outside and cook fuel in the skillet, and inside is too flammable to cook fuel in a skillet. What about a fuel that I don't need to heat to cast?

Ratings

For burn I am looking for it to hold a flame and burn with vigor. I am not too concerned with burn rate being high because it could be increased with an additive (probably).

For physical characteristics I want it to mix easy, mold easy, dry hard and not crumble. I was hoping for something that would case bond to PVC, but I have decided against case bonded motors for the time being. I would love to be able to cast it directly in the grain inhibitor, which I do with the hot propellant.

Formulations

F1

Royal Icing made with powdered sugar, cream of tartar and an egg white. Small pieces dried and burned, but grain sized pieces would not dry, much less burn.

F2

Formulation

Component	Amount
KNO3	32g
Sucrose	17g
PVC Cement	10g

Mechanical - Poor

Dry and hard, but brittle. Crumbles. Shrinks from mold to some extent.

Burn - Good

Lights very easily, burns well. 22mm in 6 seconds. Call it 7 seconds per inch.

F3

Formulation

Component	Amount
KNO3	32g
Sucrose	17g
Polystyrene	10g

Mechanical - Mediocre

Took a few days to dry. Hard and tough. Shrinks from mold, no good for case bond. Has trouble sticking to itself when wet. two balls, once separated, do not stick on contact, they have to be mixed back together. While wet it has a stringy texture. Minor voids.

Burn - Poor

Hard to light. Wont stay lit. 30 mm strand burned maybe 10mm in 12 seconds then went out.

F4

Formulation

Component	Amount
KNO3	34g
Sucrose	9g
Polystyrene	9g

Mechanical - Mediocre

Very hard when dry. Shrinks from mold. Significant voids.

Burn - Poor

Lights on fire, with difficulty. Yellow flame, no vigor.

F5

7g PVC Cement added to 36g (wet with acetone) #F4

Mechanical - Poor

Very hard. No shrinkage or visible voids. Bonds to PVC mold.

Terrible voids inside.

Burn - Poor

Barely lights.

F6

Formulation

Component	Amount
KNO3	33g
Sucrose	17g
Polystyrene	4g
PVC Cement	4g

Mechanical - Good

Very hard. Bonds to PVC mold when dry, however does not stick to it strongly while wet. When cast in cardboard it shrinks, more than recrystallized propellant. Not hygroscopic.

Burn - Good

Easy to light. Burns vigorously. 25mm in 12 seconds, or 12 seconds per inch. 3 later burns look more like 20 seconds per inch. Trying to roll snakes of the stuff creates voids in the center which greatly increase the apparent burn rate of a strand. Extruded strands, squished long with fingers, burn at about 20 (3 tests).

I disposed of a test grain with a hole drilled partway through (like a nozzleless motor) by burning it. The exhaust plume had a bright flame in it about 10 inches from the grain. I wonder if this could be leveraged into a visible or colored flame?

F7 - Rammed

Formulation

Component	Amount
KNO3	33g
Sucrose	17g
Polystyrene	4g
PVC Cement	4g

Mechanical - Good - Too much work

This is the same formula as F6 but with only enough acetone to create a crumbly barely damp powder. I then rammed it into PVC pipe. Dries very hard, no visible shrinkage. Does not bind to PVC mold, but is very hard to extract.

Further investigation shows that when case bonded to PVC it shrinks away in the center, not at the ends, creating an unacceptable situation.

The ramming is too much effort in my opinion. If I had the tooling for it I might consider this.

Burn - Good

Looks similar to F6, but since it is rammed I can not create a strand.